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Sample records for bioturbation

  1. The mode of bioturbation triggers pesticide remobilization from aquatic sediments.

    Science.gov (United States)

    Bundschuh, Mirco; Schletz, Marco; Goedkoop, Willem

    2016-08-01

    After their release into the aquatic environment, contaminants may - depending on the physicochemical properties - adsorb to sediments. From there these contaminants can either be buried or remobilised by abiotic factors (e.g., resuspension) as well as by the bioturbating activity of sediment dwelling invertebrates. Little is, however, know about the effects of bioturbation on the fate of pesticides. Therefore, the present study quantified the impact of the bioturbation mode of benthic invertebrate species (bio-diffusor vs. bio-irrigation), the invertebrate density (i.e. 0-8 individuals per replicate), and the substance-inherent properties (i.e. hydrophobicity, water solubility) on the remobilization of sediment-associated pesticides in a laboratory-based set-up over 13 days. We found that both the bioturbation mode (i.e., species identity) and species density, as well as pesticide properties (i.e., hydrophobicity) affected the direction and magnitude of remobilisation of sediment-bound pesticides. The oligochaeta Lumbriculus variegatus showed a density-dependent effect on the remobilization of lindane to the water phase, whereas those with the amphipod Monoporeia affinis and larvae of the midge Chironomus riparius did not. Although these findings show that sediments not per definition are a sink for pesticides, the rates of pesticide remobilization are limited. This observation, thus, suggests that the risk for aquatic communities posed by the remobilization of pesticides from the sediment due to bioturbation is low. PMID:27107774

  2. Stabilization of the coupled oxygen and phosphorus cycles by the evolution of bioturbation

    DEFF Research Database (Denmark)

    Boyle, Richard; Dahl, Tais Wittchen; Dale, A. W.;

    2014-01-01

    between bioturbated and laminated sediments. Bioturbation also reduces steady-state marine phosphate levels, but this effect is offset by the decline in iron-adsorbed phosphate burial that results from a decrease in oxygen concentrations. The introduction of oxygen-sensitive bioturbation to dynamical...

  3. Bioturbation: a fresh look at Darwin's last idea

    NARCIS (Netherlands)

    Meysman, F.J.R.; Middelburg, J.J.; Heip, C.H.R.

    2006-01-01

    Bioturbation refers to the biological reworking of soils and sediments, and its importance for soil processes and geomorphology was first realised by Charles Darwin, who devoted his last scientific book to the subject. Here, we review some new insights into the evolutionary and ecological role of bi

  4. Remobilisation of uranium from contaminated freshwater sediments by bioturbation

    Directory of Open Access Journals (Sweden)

    S. Lagauzère

    2013-10-01

    Full Text Available Previous studies have demonstrated that benthic macro-invertebrate bioturbation can influence the remobilization of uranium initially associated with freshwater sediments resulting in a high release of this pollutant through the overlying water column. Giving the potential negative effects on aquatic biocenosis and the global ecological risk, it appeared crucial to improve our current knowledge concerning the uranium biogeochemical behaviour in sediments. The present study aimed to assess the biogeochemical modifications induced by Tubifex tubifex (Annelida, Clitellata, Tubificidae bioturbation within the sediment permitting to explain such a release of uranium. To reach this goal, uranium distribution between solid and solute phases of a reconstructed benthic system (i.e. in mesocosms inhabited or not by T. tubifex worms was assessed in a 12 day laboratory experiment. Thanks notably to fine resolution (mm-scale measurements (e.g. DET gels probes for porewater, bioaccumulation in worms of uranium and main chemical species (iron, sulfate, nitrate, nitrite, this work permitted (i to confirm that the removal of bottom sediment particles to the surface through the digestive tract of worms greatly favours the oxidative loss of uranium in the water column, and (ii to demonstrate that both uranium contamination and bioturbation of T. tubifex substantially influence major microbial-driven biogeochemical reactions in sediments (e.g. stimulation of denitrification, sulfate-reduction and iron dissolutive reduction. This study provides the first demonstration of biogeochemical modifications induced by bioturbation in freshwater uranium-contaminated sediments.

  5. An open source simulation model for soil and sediment bioturbation

    NARCIS (Netherlands)

    Schiffers, K.; Teal, L.R.; Travis, J.M.J.; Solan, M.

    2011-01-01

    Bioturbation is one of the most widespread forms of ecological engineering and has significant implications for the structure and functioning of ecosystems, yet our understanding of the processes involved in biotic mixing remains incomplete. One reason is that, despite their value and utility, most

  6. Quantifying bioturbation and soil thickening over the late Quaternary

    Science.gov (United States)

    Wilkinson, M. T.; Pietsch, T.; Fox, J. F.

    2009-04-01

    We present geochemistry and biochemistry data to explore how bioturbation has operated in a residual sandstone-derived soil that thickened during the Holocene following aeolian deflation during the Last Glacial Maximum. Our site is located on a plateau cut into Triassic sandstones in humid Blue Mountains, SE Australia, where precipitation is ~1100 mm/a, and the mean annual maximum and minimum temperatures are 17°C and 5°C, respectively. Vegetation cover increase occurred ~13 ka, based on nearby palaeodune activity and pollen data from other highland sites. Our interpretation of terrestrial cosmogenic radionuclides (TCN) data suggests that ~30 cm of soil thickening has taken place since 13 ka, which includes 16 cm of bedrock lowering. Biofabrics preserve a short-term picture of biotically-displaced soil. In general, bioturbation decreases exponentially with increasing soil depth. The upper 21 cm of the profile is ~95% bioturbated; the middle 13 cm is 13 - 32% bioturbated; and the lowest 52 cm is 1 - 6% bioturbated. Tree roots penetrate weakness in the sandstone below this depth. Fallout radionuclides (7Be, 210Pb, and 137Cs) in the profile also suggest that vertical mixing in the upper 20 - 40 cm occurs over short—decadal—timescales. Optically stimulated luminescene (OSL) data records the time that quartz grains were last at the surface, and are used here to demonstrate vertical mixing of the profile over tens of thousands of years. OSL data indicates that some soil grains at all burial depths were once at the surface, consistent with modern process observations. Carbon and nitrogen isotopic values (delta 13C and delta 15N) of soil organic matter support the existence of soil organic matter turnover in the upper 30 cm of the soil column when regressed with log(SOC) and log(TN). Our carbon isotope data defy typical trends below ~30 cm for residual, undisturbed soils. We suggest this may reflect the absence of bioturbation during the LGM when the climate was cold

  7. Bioturbation in different ecosystems at Forsmark and Oskarshamn

    International Nuclear Information System (INIS)

    The Swedish Nuclear Fuel and Waste Management Co (SKB) carries out extensive investigations on factors that can affect long-term storage of nuclear waste. Earthworms consume organic soil materials and when doing so they transport and mix mineral soil particles as well as litter and humus materials. Ants do not consume soil materials, but they collect and mix mineral soil particles and litter materials to construct their nests. This process of material displacement by earthworms and ants is called bioturbation and can be a mechanism for the redistribution (vertical and horizontal) of radionuclides within the soil profile. The aim of the present study was to determine the quantitative impact of earthworms and ants on bioturbation of soil in different ecosystems at Forsmark and Oskarshamn. Earthworms were sampled at four 20x20 cm2 sub-plots at each site and were determined, dried and weighed in the laboratory. Gut passage time and faeces production were determined in a laboratory experiment at constant temperature. Temperature dependence of earthworm growth was studied at 3, 6, 10 and 20 deg C, and it was assumed that defecation mirrored growth as regards temperature dependence. Ant species composition, ant nest density and nest volume were investigated in the field by using pitfall traps and a transect method to enumerate ant nests. Dry weights of ant nests were determined after weighing in the laboratory. Earthworm abundances and biomasses were high in moist/wet alder forests and deciduous woodlands and low in pine and pine/spruce forests at both Forsmark and Oskarshamn. In mesic spruce forests, high estimates of abundance/biomass of earthworms were found at Forsmark but low at Oskarshamn, whereas grazed pastures had high estimates at Oskarshamn and ungrazed abandoned fields had relatively low estimates at Forsmark. High pH at Forsmark and low pH at Oskarshamn as well as high groundwater tables at some of the Forsmark sites can explain the difference between

  8. Bioturbation in different ecosystems at Forsmark and Oskarshamn

    Energy Technology Data Exchange (ETDEWEB)

    Persson, Tryggve; Lenoir, Lisette; Taylor, Astrid [Dept. of Ecology and Environmental Research, Swedish University or Agricultural Sciences, Uppsala (Sweden)

    2007-01-15

    The Swedish Nuclear Fuel and Waste Management Co (SKB) carries out extensive investigations on factors that can affect long-term storage of nuclear waste. Earthworms consume organic soil materials and when doing so they transport and mix mineral soil particles as well as litter and humus materials. Ants do not consume soil materials, but they collect and mix mineral soil particles and litter materials to construct their nests. This process of material displacement by earthworms and ants is called bioturbation and can be a mechanism for the redistribution (vertical and horizontal) of radionuclides within the soil profile. The aim of the present study was to determine the quantitative impact of earthworms and ants on bioturbation of soil in different ecosystems at Forsmark and Oskarshamn. Earthworms were sampled at four 20x20 cm{sup 2} sub-plots at each site and were determined, dried and weighed in the laboratory. Gut passage time and faeces production were determined in a laboratory experiment at constant temperature. Temperature dependence of earthworm growth was studied at 3, 6, 10 and 20 deg C, and it was assumed that defecation mirrored growth as regards temperature dependence. Ant species composition, ant nest density and nest volume were investigated in the field by using pitfall traps and a transect method to enumerate ant nests. Dry weights of ant nests were determined after weighing in the laboratory. Earthworm abundances and biomasses were high in moist/wet alder forests and deciduous woodlands and low in pine and pine/spruce forests at both Forsmark and Oskarshamn. In mesic spruce forests, high estimates of abundance/biomass of earthworms were found at Forsmark but low at Oskarshamn, whereas grazed pastures had high estimates at Oskarshamn and ungrazed abandoned fields had relatively low estimates at Forsmark. High pH at Forsmark and low pH at Oskarshamn as well as high groundwater tables at some of the Forsmark sites can explain the difference between

  9. Protracted development of bioturbation through the early Palaeozoic Era

    Science.gov (United States)

    Tarhan, Lidya G.; Droser, Mary L.; Planavsky, Noah J.; Johnston, David T.

    2015-11-01

    Bioturbation, the physical and chemical mixing of sediment by burrowing animals, exerts an important control on the character of modern marine sediments and biogeochemical cycling. Here we show that the mixing of sediments on marine shelves remained limited until at least the late Silurian, 120 million years after the Precambrian-Cambrian transition. We present ichnological, stratigraphic and taphonomic data from a range of lower Phanerozoic siliciclastic successions spanning four palaeocontinents. The protracted development of the sediment mixed layer is also consistent with sulphur data and global sulphur model simulations. The slow increase in the intensity of bioturbation in the sediment record suggests that evolutionary advances in sediment colonization outpaced advances in sediment mixing. We conclude that ecosystem restructuring caused by the onset of significant infaunal mobile deposit feeding (`bulldozing’) occurred well after both the Cambrian Explosion and the Great Ordovician Biodiversification Event.

  10. Stabilization of the coupled oxygen and phosphorus cycles by the evolution of bioturbation

    Science.gov (United States)

    Boyle, R. A.; Dahl, T. W.; Dale, A. W.; Shields-Zhou, G. A.; Zhu, M.; Brasier, M. D.; Canfield, D. E.; Lenton, T. M.

    2014-09-01

    Animal burrowing and sediment-mixing (bioturbation) began during the run up to the Ediacaran/Cambrian boundary, initiating a transition between the stratified Precambrian and more well-mixed Phanerozoic sedimentary records, against the backdrop of a variable global oxygen reservoir probably smaller in size than present. Phosphorus is the long-term limiting nutrient for oxygen production via burial of organic carbon, and its retention (relative to carbon) within organic matter in marine sediments is enhanced by bioturbation. Here we explore the biogeochemical implications of a bioturbation-induced organic phosphorus sink in a simple model. We show that increased bioturbation robustly triggers a net decrease in the size of the global oxygen reservoir--the magnitude of which is contingent upon the prescribed difference in carbon to phosphorus ratios between bioturbated and laminated sediments. Bioturbation also reduces steady-state marine phosphate levels, but this effect is offset by the decline in iron-adsorbed phosphate burial that results from a decrease in oxygen concentrations. The introduction of oxygen-sensitive bioturbation to dynamical model runs is sufficient to trigger a negative feedback loop: the intensity of bioturbation is limited by the oxygen decrease it initially causes. The onset of this feedback is consistent with redox variations observed during the early Cambrian rise of bioturbation, leading us to suggest that bioturbation helped to regulate early oxygen and phosphorus cycles.

  11. Bioturbation by the Fungus-Gardening Ant, Trachymyrmex septentrionalis

    Science.gov (United States)

    Tschinkel, Walter R.; Seal, Jon N.

    2016-01-01

    Soil invertebrates such as ants are thought to be important manipulators of soils in temperate and tropical ecosystems. The fungus gardening ant, Trachymyrmex septentrionalis, is an important agent of biomantling, that is, of depositing soil excavated from below onto the surface, and has been suggested as an agent of bioturbation (moving soil below ground) as well. The amount of bioturbation by this ant was quantified by planting queenright colonies in sand columns consisting of 5 layers of different colored sand. The amount of each color of sand deposited on the surface was determined from April to November 2015. In November, colonies were excavated and the color and amount of sand deposited below ground (mostly as backfill in chambers) was determined. Extrapolated to one ha, T. septentrionalis deposited 800 kg of sand per annum on the surface, and an additional 200 kg (17% of the total excavated) below ground. On average, this mixes 1.3% of the sand from other layers within the top meter of soil per millennium, but this mixing is unlikely to be homogeneous, and probably occurs as "hotspots" in both horizontal and vertical space. Such mixing is discussed as a challenge to sediment dating by optically stimulated luminescence (OSL). PMID:27391485

  12. Bioturbation by the Fungus-Gardening Ant, Trachymyrmex septentrionalis.

    Science.gov (United States)

    Tschinkel, Walter R; Seal, Jon N

    2016-01-01

    Soil invertebrates such as ants are thought to be important manipulators of soils in temperate and tropical ecosystems. The fungus gardening ant, Trachymyrmex septentrionalis, is an important agent of biomantling, that is, of depositing soil excavated from below onto the surface, and has been suggested as an agent of bioturbation (moving soil below ground) as well. The amount of bioturbation by this ant was quantified by planting queenright colonies in sand columns consisting of 5 layers of different colored sand. The amount of each color of sand deposited on the surface was determined from April to November 2015. In November, colonies were excavated and the color and amount of sand deposited below ground (mostly as backfill in chambers) was determined. Extrapolated to one ha, T. septentrionalis deposited 800 kg of sand per annum on the surface, and an additional 200 kg (17% of the total excavated) below ground. On average, this mixes 1.3% of the sand from other layers within the top meter of soil per millennium, but this mixing is unlikely to be homogeneous, and probably occurs as "hotspots" in both horizontal and vertical space. Such mixing is discussed as a challenge to sediment dating by optically stimulated luminescence (OSL). PMID:27391485

  13. RESPONSE OF GHOST SHRIMP (NEOTRYPAEA CALIFORNIENSIS) BIOTURBATION TO ORGANIC MATTER ENRICHMENT OF ESTUARINE INTERTIDAL SEDIMENTS

    Science.gov (United States)

    Populations of burrowing shrimp (Neotrypaea californiensis and Upogebia p;ugettensis) are the dominant invertebrate fauna on Pacific estuarine tide flats, occupying >80% of intertidal area in some estuaries. Burrowing shrimp are renowned for their bioturbation of intertidal sedi...

  14. Quantification of termite bioturbation in a savannah ecosystem: Application of OSL dating

    DEFF Research Database (Denmark)

    Kristensen, Jeppe Ågård; Thomsen, Kristina Jørkov; Murray, Andrew;

    2015-01-01

    Luminescence dating is one of the most promising technique available for studying bioturbation on pedological timescales. In this study, we use multi-grain and single-grain quartz OSL to quantify termite bioturbation processes (Macrotermes natalensis) in a savannah ecosystem in Ghana. Termites...... 10e20% of the volume ka-1 below the unit formed by reburied termite deposits. © 2015 Elsevier B.V. All rights reserved....

  15. Ecosystem engineering at the sediment-water interface: bioturbation and consumer-substrate interaction.

    Science.gov (United States)

    Nogaro, Géraldine; Mermillod-Blondin, Florian; Valett, Maurice H; François-Carcaillet, Frédérique; Gaudet, Jean-Paul; Lafont, Michel; Gibert, Janine

    2009-08-01

    In soft-bottom sediments, consumers may influence ecosystem function more via engineering that alters abiotic resources than through trophic influences. Understanding the influence of bioturbation on physical, chemical, and biological processes of the water-sediment interface requires investigating top-down (consumer) and bottom-up (resource) forces. The objective of the present study was to determine how consumer bioturbation mode and sediment properties interact to dictate the hydrologic function of experimental filtration systems clogged by the deposition of fine sediments. Three fine-grained sediments characterized by different organic matter (OM) and pollutant content were used to assess the influence of resource type: sediment of urban origin highly loaded with OM and pollutants, river sediments rich in OM, and river sediments poor in OM content. The effects of consumer bioturbation (chironomid larvae vs. tubificid worms) on sediment reworking, changes in hydraulic head and hydraulic conductivity, and water fluxes through the water-sediment interface were measured. Invertebrate influences in reducing the clogging process depended not only on the mode of bioturbation (construction of biogenic structures, burrowing and feeding activities, etc.) but also on the interaction between the bioturbation process and the sediments of the clogging layer. We present a conceptual model that highlights the importance of sediment influences on bioturbation and argues for the integration of bottom-up influence on consumer engineering activities. PMID:19462183

  16. Water Velocity and Bioturbation Alter Sediment Resuspension and Biogeochemistry in an Experimental Freshwater Mesocosm System

    Science.gov (United States)

    Spivak, A.; Vanni, M. J.

    2010-12-01

    Processes such as bioturbation and resuspension can affect organic matter decomposition by altering sediment redox conditions. Increased oxygen availability may, in turn, affect remineralization rates and larger scale processes such as benthic-pelagic coupling. However, relatively few studies have explicitly tested the simultaneous effects of bioturbation and water velocity on benthic biogeochemistry and sediment resuspension. Using a mesocosm system we conducted two experiments testing the effects of bioturbator identity on particulate and dissolved nutrient dynamics before and after a resuspension event (i.e. water velocity held constant at 0.12 m s-1 for 2 hr; Expt. 1) and rates of sediment resuspension with increasing water velocity (0.00 - 0.20 m s-1; Expt. 2). We manipulated bioturbator identity across four levels as sediments were undisturbed (control), manually punctured (2% of surface area), or disturbed by one of two fish species, either bluegill or catfish. For Expt. 1, the bioturbation treatments were applied for several days and measurements were made before and after the resuspension event. Initially, water column chlorophyll and total suspended sediment (TSS) concentrations were highest in the catfish treatments. Bioturbator identity did not affect the stoichiometry of TSS as strongly; C:N was unaffected by our treatments while N:P was lowest in the disturbed treatments. After the resuspension event, there was no difference in TSS concentrations or stoichiometric ratios across the bioturbation treatments. Dissolved nutrient flux rates were insensitive to the bioturbation treatments and were more strongly influenced by the resuspension event. For instance, sediment NO3- fluxes were negative (i.e. net flux into sediments) until after the resuspension event when they became positive. In Expt. 2, we gradually increased water velocity from 0.00 - 0.20 m s-1 and measured TSS concentrations only. TSS was initially highest in catfish treatments and lowest in

  17. Bioturbation by Fire Ants in the Coastal Prairie of Texas

    Science.gov (United States)

    Cameron, G.; Williams, L.

    2001-12-01

    Fire ants (Solenopsis invicta) were introduced to the US in the early part of the last century. They have spread throughout the southeastern US in the absence of native competitors and predators with a range limited by abiotic factors. Each fire ant mound contains thousands of individuals, can be large, and can be numerous enough to comprise a dominant feature of the landscape. Studies of this species have focused upon its spread, formation of single- and multiple-queen colonies, genetic structure, and impact on native fauna and human health. Some studies have analyzed native fire ant-soil interactions, but few studies have examined the process of bioturbation by introduced fire ants in native ecosystems. Fire ants on the coastal prairie of Texas primarily are of the multiple-queen type that exhibit a much higher density of mounds than the single-queen type. Consequently, mound-building activities by fire ants can have a marked effect upon soil structure and nutrient content and may affect soil organisms and plants. Fire ant activity, mound density, mound dispersion, soil texture, soil permeability, soil moisture content, and soil nutrients were measured. Fire ants mounds are visible aboveground from April-November. Density of mounds was 117-738/ha, and average mound lifespan was 3.6 months with only 9% of the mounds remaining active throughout the entire season. Mounds were dispersed randomly. Foraging activity by fire ants was from June through October with a peak in July. Annual soil turnover was estimated by collecting and weighing mounds. There was no effect of ant mounds on soil texture, but water infiltration was higher in areas with ant mounds. Early-season samples showed no nutrient differences, but late-season samples showed that ant mounds contained higher amounts of micronutrients than random samples of soil. These data are compared to similar data on effects of mounds from native ants and from native and introduced ants in different habitats.

  18. [Effects of invertebrate bioturbation on vertical hydraulic conductivity of streambed for a river].

    Science.gov (United States)

    Ren, Chao-Liang; Song, Jin-Xi; Yang, Xiao-Gang; Xue, Jian

    2013-11-01

    Streambed hydraulic conductivity is a key factor influencing water exchange between surface water and groundwater. However, the streambed invertebrate bioturbation has a great effect on the hydraulic conductivity. In order to determine the impact of invertebrate bioturbation on streambed hydraulic conductivity, the investigation of invertebrate bioturbation and in-situ test of vertical hydraulic conductivity of streambed are simultaneously conducted at five points along the main stream of the Weihe River. Firstly, correlation between the streambed vertical hydraulic conductivity and grain size distribution is analyzed. Secondly, type and density of the invertebrate and their correlation to hydraulic conductivity are determined. Finally, the effect of invertebrate bioturbation on the streambed hydraulic conductivity is illustrated. The results show that the vertical hydraulic conductivity and biological density of invertebrate are 18.479 m x d(-1) and 139 ind x m(-2), respectively for the Caotan site, where sediment composition with a large amount of sand and gravel particles. For Meixian site, the sediment constitutes a large amount of silt and clay particles, in which the vertical hydraulic conductivity and biological density of invertebrate are 2.807 m x d(-1) and 2 742 ind x m(-2) respectively. Besides, for the low permeability of four sites (Meixian, Xianyang, Lintong and Huaxian), grain size particles are similar while the vertical hydraulic conductivity and biological density of invertebrate are significantly different from one site to another. However, for each site, the vertical hydraulic conductivity closely related to biological density of invertebrate, the Pearson correlation coefficient is 0.987. It can be concluded that both grain size particles and invertebrate bioturbation influence sediment permeability. For example, higher values of streambed hydraulic conductivity from strong permeability site mainly due to the large amount of large-size particles

  19. Bioturbation in a declining oxygen environment, in situ observations from Wormcam.

    Directory of Open Access Journals (Sweden)

    S Kersey Sturdivant

    Full Text Available Bioturbation, the displacement and mixing of sediment particles by fauna or flora, facilitates life supporting processes by increasing the quality of marine sediments. In the marine environment bioturbation is primarily mediated by infaunal organisms, which are susceptible to perturbations in their surrounding environment due to their sedentary life history traits. Of particular concern is hypoxia, dissolved oxygen (DO concentrations ≤2.8 mg l(-1, a prevalent and persistent problem that affects both pelagic and benthic fauna. A benthic observing system (Wormcam consisting of a buoy, telemetering electronics, sediment profile camera, and water quality datasonde was developed and deployed in the Rappahannock River, VA, USA, in an area known to experience seasonal hypoxia from early spring to late fall. Wormcam transmitted a time series of in situ images and water quality data, to a website via wireless internet modem, for 5 months spanning normoxic and hypoxic periods. Hypoxia was found to significantly reduce bioturbation through reductions in burrow lengths, burrow production, and burrowing depth. Although infaunal activity was greatly reduced during hypoxic and near anoxic conditions, some individuals remained active. Low concentrations of DO in the water column limited bioturbation by infaunal burrowers and likely reduced redox cycling between aerobic and anaerobic states. This study emphasizes the importance of in situ observations for understanding how components of an ecosystem respond to hypoxia.

  20. Bioturbation in a declining oxygen environment, in situ observations from Wormcam.

    Science.gov (United States)

    Sturdivant, S Kersey; Díaz, Robert J; Cutter, George R

    2012-01-01

    Bioturbation, the displacement and mixing of sediment particles by fauna or flora, facilitates life supporting processes by increasing the quality of marine sediments. In the marine environment bioturbation is primarily mediated by infaunal organisms, which are susceptible to perturbations in their surrounding environment due to their sedentary life history traits. Of particular concern is hypoxia, dissolved oxygen (DO) concentrations ≤2.8 mg l(-1), a prevalent and persistent problem that affects both pelagic and benthic fauna. A benthic observing system (Wormcam) consisting of a buoy, telemetering electronics, sediment profile camera, and water quality datasonde was developed and deployed in the Rappahannock River, VA, USA, in an area known to experience seasonal hypoxia from early spring to late fall. Wormcam transmitted a time series of in situ images and water quality data, to a website via wireless internet modem, for 5 months spanning normoxic and hypoxic periods. Hypoxia was found to significantly reduce bioturbation through reductions in burrow lengths, burrow production, and burrowing depth. Although infaunal activity was greatly reduced during hypoxic and near anoxic conditions, some individuals remained active. Low concentrations of DO in the water column limited bioturbation by infaunal burrowers and likely reduced redox cycling between aerobic and anaerobic states. This study emphasizes the importance of in situ observations for understanding how components of an ecosystem respond to hypoxia. PMID:22493701

  1. Influence of benthic macro-invertebrate bioturbation on the biogeochemical behaviour of uranium within freshwater sediments

    International Nuclear Information System (INIS)

    In freshwater ecosystems, sediments act as an accumulation compartment for metallic pollutants as uranium. Secondary, there can also represent endogenous sources of contamination by resuspension (e.g. flood, bioturbation) or changes of metal speciation that acts upon their bioavailability. Indeed, metallic compounds can be transformed in more or less toxic or inert compounds through physico-chemical (e.g. pH, redox conditions, ionic force) and microbiological variations. These conditions are themselves under the effects of benthic macro-invertebrate activities via bioturbation processes. The main objective of this PhD was to determinate the influence of two benthic macro-invertebrate species (Chironomus riparius and Tubifex tubifex) on the distribution and the transfers of uranium within freshwater sediments. To reach this goal, laboratory experiments were performed in order to (i) assess the effects of uranium on benthic macro-invertebrates, more particularly on their bioturbation activity, (ii) determine the influence of these organisms on uranium behaviour through high resolution physico-chemical measurements (e.g. oxygen optodes, DET gel probes), and (iii) estimate the consequences of these interactions on pelagic organisms via genotoxicity measurements (micronuclei assay and molecular bio-markers analysis on Xenopus laevis). The results demonstrate that bioturbation intensity of macro-invertebrates can be affected in uranium-contaminated sediments, but the two species studied in this work show a relative tolerance. For high uranium concentrations (>100 times the geochemical background level), corresponding however to realistic concentrations in highly contaminated sites, T. tubifex worms are able to maintain a sufficient bioturbation activity that induces a high remobilization of uranium initially associated with sediments to the overlying water (factor 2 to 10). That represents therefore a potential risk for the remaining aquatic biocenose. However, by

  2. Iron-coupled inactivation of phosphorus in sediments by macrozoobenthos (chironomid larvae) bioturbation: Evidences from high-resolution dynamic measurements

    International Nuclear Information System (INIS)

    The effects of chironomid larvae bioturbation on the lability of phosphorus (P) in sediments were investigated through sediment incubation for 140 days. High-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) techniques were applied to obtain soluble and labile P/Fe profiles at a millimeter resolution, respectively. The larvae bioturbation decreased concentrations of soluble/labile P and Fe by up to over half of the control at the sediment depths of influence up to 70 and 90 mm respectively. These effects continued over 116 days and disappeared on the 140th days due to eclosion of chironomid larvae. Labile P was highly correlated with labile Fe, while a weak correlation was observed between soluble P and soluble Fe. It was concluded that Fe(II) oxidation and its enhanced adsorption were the major mechanisms responsible for the decreases of soluble and labile P. - Highlights: • High resolution techniques were employed to study bioturbation effects on P. • Larvae bioturbation decreased the concentrations of soluble/labile P and Fe. • Bioturbation effects continued over 116 days and disappeared on the 140th days. • Labile P was more sensitive than pore water SRP in response to bioturbation. • It proved the mechanism of Fe-coupled inactivation of P in bioturbation sediments. - Chironomid larvae bioturation decreased the lability of P in sediments from Fe(II) oxidation and enhanced adsorption of P

  3. Bioturbation in near-surface sediments from the COMRA Polymetallic Nodule Area:evidence from excess 210Pb measurements

    Institute of Scientific and Technical Information of China (English)

    YANG Qunhui; ZHOU Huaiyang

    2004-01-01

    In order to evaluate bioturbation in sediments from the COMRA Polymetallic Nodule Area in the northeast tropical Pacific, excess 210Pb profiles in sediments cores collected with multiple corers during R/V DAYANGYIHAO Environmental Program Cruise in 1998 were measured by direct gamma assay using Ortec HPGe GWL series well-type coaxial low background intrinsic germanium detectors. A steady-state diffusion model of excess 210Pb profiles suggests that bioturbation mixing depths and biodiffusion coefficients are 16 cm and 2.75 cm2/a in East Zone, and 6 cm and 0.26 cm2/a in West Zone, respectively. Furthermore, the observations of macrofauna and measurements of total organic carbon (TOC) content in sediments suggest that bioturbation is directly controlled by species and abundance of benthic fauna, such as polychaete, and the bioturbation mixing depth and intensity are positively correlated with the organic matter content.

  4. Effects of bioturbation on the fate of oil in coastal sandy sediments - An in situ experiment

    DEFF Research Database (Denmark)

    Timmermann, Karen; Banta, Gary T.; Klinge, Lars;

    2011-01-01

    Effects of bioturbation by the common lugworm Arenicola marina on the fate of oil hydrocarbons (alkanes and PAHs) were studied in situ during a simulated oil spill in a shallow coastal area of Roskilde fjord, Denmark. The fate of selected oil compounds was monitored during 120 d using GC......–MS and bioturbation activity (feces production and irrigation) was measured regularly during the experiment and used as input parameters in a mechanistic model describing the effects of A. marina on the transport and degradation of oil compounds in the sediment. The chemical analytical data and model results...... indicated that A. marina had profound and predictable effects on the distribution, degradation and preservation of oil and that the net effect depended on the initial distribution of oil. In sediment with an oil contaminated subsurface-layer A. marina buried the layer deeper in the sediment which clearly...

  5. Effects of short term bioturbation by common voles on biogeochemical soil variables.

    Directory of Open Access Journals (Sweden)

    Burkhard Wilske

    Full Text Available Bioturbation contributes to soil formation and ecosystem functioning. With respect to the active transport of matter by voles, bioturbation may be considered as a very dynamic process among those shaping soil formation and biogeochemistry. The present study aimed at characterizing and quantifying the effects of bioturbation by voles on soil water relations and carbon and nitrogen stocks. Bioturbation effects were examined based on a field set up in a luvic arenosol comprising of eight 50 × 50 m enclosures with greatly different numbers of common vole (Microtus arvalis L., ca. 35-150 individuals ha-1 mth-1. Eleven key soil variables were analyzed: bulk density, infiltration rate, saturated hydraulic conductivity, water holding capacity, contents of soil organic carbon (SOC and total nitrogen (N, CO2 emission potential, C/N ratio, the stable isotopic signatures of 13C and 15N, and pH. The highest vole densities were hypothesized to cause significant changes in some variables within 21 months. Results showed that land history had still a major influence, as eight key variables displayed an additional or sole influence of topography. However, the δ15N at depths of 10-20 and 20-30 cm decreased and increased with increasing vole numbers, respectively. Also the CO2 emission potential from soil collected at a depth of 15-30 cm decreased and the C/N ratio at 5-10 cm depth narrowed with increasing vole numbers. These variables indicated the first influence of voles on the respective mineralization processes in some soil layers. Tendencies of vole activity homogenizing SOC and N contents across layers were not significant. The results of the other seven key variables did not confirm significant effects of voles. Thus overall, we found mainly a first response of variables that are indicative for changes in biogeochemical dynamics but not yet of those representing changes in pools.

  6. Middle Ordovician Bioturbation Structures from Southeastern Margin of Ordos Basin and Their Environmentary Interpretation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Trace fossils were discovered in the Middle Ordovician Badou Member of Fengfeng Formation and the Member 1 of Jinsushan Formation in Mt. Jinsu of the Fuping region which lies at the southeastern margin of the Ordos basin. The rocks of the fore-mentioned parts contain a considerable amount of bioturbation structures, in which ichnogenus and ichnospecies can not be identified, and abundant stromatolites.The distributions and characteristics of the bioturbation structures are analyzed and summarized in this paper. The paleoenvironments of related formations and members were interpreted in the method of semiquantitative analysis of bioturbation structures with researches on stromatolites and sedimentology. It is suggested that Fuping zone, located in the southeastern margin of the Ordos basin, was a carbonate platform where stromatolite-developing tidal flat and low-energy subtidal open platform environments dominated. Also that this zone experienced three paleogeographic evolutions from tidal flat to low-energy subtidal open platform environments, that is, three larger-scale eustatisms occurred during the sedimentary period of Middle Ordovician Badou Member of Fengfeng Formation to the Member 1 of Jinsushan Formation.

  7. Bioturbation of three endogeic earthworms - A. caliginosa, A. chlorotica and A. icterica - depending on organic matter location

    Science.gov (United States)

    Le Couteulx, Alexis; Wolf, Cédric; Pérès, Guénola; Hallaire, Vincent

    2015-04-01

    Earthworms alter soil structure through their bioturbation activity: the creation of burrow paths and the production of casts in their burrows or at soil surface. Thus, they may alter some soil functionnal properties (e.g. hydraulic conductivity) and ecosystem services. In cultivated fields, earthworms are a key structuring process and play a major role in the maintenance, the improvement and even the degradation of soil structure. However, bioturbation patterns of the different endogeic species are still not precisely known. This study aims at describing the burrowing and casting activity of three endogeic earthworm species with two different organic matter (OM) locations. Cylindrical microcosms (15 cm high) were set up with a silt-loam soil and 0.6 per cent of dry grass leaves was added at two locations: mixed with soil or dropped at its surface; three endogeic species were studied in monospecific microcosms: Allolobophora chlorotica, Allolobophora icterica and Aporrectodea caliginosa. Microcosms were kept for 60 days at 12°C. They were then stripped centimeter by centimeter and, on each layer the bioturbated area, number of bioturbated areas (= objects), blocking cast area (casts that prevent earthworms from passing), non-blocking cast area and the angles of burrow paths were assessed. In this study, the rate of non-blocking cast is stable whatever the species and the OM location. Regardless of the species, there are fewer objects but a greater percentage of blocking cast with mixed OM than with surface OM. Only A. chlorotica and A. caliginosa have a greater bioturbated area with mixed OM than with surface OM. With OM at soil surface: A. icterica has a higher bioturbated area and generates more objects than A. caliginosa, which has a higher bioturbated area and generates more objects than A. chlorotica. Interestingly, there are very few differences between the three species with mixed OM. The bioturbation activity of earthworms is also affected by depth: the

  8. The influence of bioturbation on the vertical distribution of soil organic matter in volcanic ash soils: A case study in northern Ecuador

    OpenAIRE

    Tonneijck, F.H.; Jongmans, A.G.

    2008-01-01

    Soil faunal bioturbation ('bioturbation') is often cited as a major process influencing the vertical distribution of soil organic matter (SOM). The influence of bioturbation on vertical SOM transport is complex because it is the result of interaction between different groups of soil faunal species that redistribute SOM through the soil profile in distinct ways. We performed a semi-quantitative micromorphological analysis of soil faunal pedofeatures and related their occurrence to the vertical...

  9. Soil bioturbation by earthworms and plant roots- mechanical and energetic considerations

    Science.gov (United States)

    Ruiz, S.; Or, D.; Schymanski, S. J.

    2014-12-01

    Soil structure is a key factor shaping hydrological and ecological functions including water storage, deep recharge and plant growth. Compaction adversely impacts soil ecosystem services over extended periods (years to decades) until structure and functionality are restored. An important class of soil structural restoration processes are related to biomechanical activity associated with borrowing of earthworms and root proliferation in impacted soils. This study employs a new biomechanical model to estimate stresses required for earthworm and plant root bioturbation under different conditions and the mechanical energy required. We consider steady state plastic cavity expansion to determine burrowing pressures of earthworms and plant roots as linked with models for cone penetration required for initial burrowing into soil volumes. We use earthworm physical and ecological parameters (e.g., population density, burrowing rate, and burrowing behavior) to convert mechanical deformation to estimation of energy and soil organic carbon (energy source for earthworms). Results illustrate a reduction in strain energy with increasing water content and trade-offs between pressure and energy investment for various root and earthworm geometries and soil hydration. The study provides a quantitative framework for estimating energy costs of bioturbation in terms of soil organic carbon or plant assimilates and delineates mechanical and hydration conditions that promote or constrain such activities.

  10. Soil Penetration by Earthworms and Plant Roots--Mechanical Energetics of Bioturbation of Compacted Soils.

    Science.gov (United States)

    Ruiz, Siul; Or, Dani; Schymanski, Stanislaus J

    2015-01-01

    We quantify mechanical processes common to soil penetration by earthworms and growing plant roots, including the energetic requirements for soil plastic displacement. The basic mechanical model considers cavity expansion into a plastic wet soil involving wedging by root tips or earthworms via cone-like penetration followed by cavity expansion due to pressurized earthworm hydroskeleton or root radial growth. The mechanical stresses and resulting soil strains determine the mechanical energy required for bioturbation under different soil hydro-mechanical conditions for a realistic range of root/earthworm geometries. Modeling results suggest that higher soil water content and reduced clay content reduce the strain energy required for soil penetration. The critical earthworm or root pressure increases with increased diameter of root or earthworm, however, results are insensitive to the cone apex (shape of the tip). The invested mechanical energy per unit length increase with increasing earthworm and plant root diameters, whereas mechanical energy per unit of displaced soil volume decreases with larger diameters. The study provides a quantitative framework for estimating energy requirements for soil penetration work done by earthworms and plant roots, and delineates intrinsic and external mechanical limits for bioturbation processes. Estimated energy requirements for earthworm biopore networks are linked to consumption of soil organic matter and suggest that earthworm populations are likely to consume a significant fraction of ecosystem net primary production to sustain their subterranean activities. PMID:26087130

  11. Contaminants, benthic communities, and bioturbation: potential for PAH mobilisation in Arctic sediments

    Energy Technology Data Exchange (ETDEWEB)

    Konovalov, D.; Renaud, P.E.; Berge, J.; Voronkov, A.Y.; Cochrane, S.K.J. [Polar Environmental Center, Tromso (Norway)

    2010-07-01

    Marine benthic fauna and biological mixing were studied in relation to sediment organic enrichment and polyaromatic hydrocarbons (PAHs) in bottom sediments of Svalbard. We investigated how organic enrichment may affect the fate and chemical composition of deposited contaminants by impacting biological reworking by faunal communities. Samples were collected near active coal mines at Barentsburg and at the mouth of Groenfjord. PAH sources in both areas were coal particles and pyrolytic compounds from coal-driven power stations. The results from a bioturbation experiment were consistent with the hypothesis that fauna enhance the vertical transport of PAHs within the sediment. Faunal community composition was similar at the two sites, with polychaete worms comprising 85% of the fauna. Abundances and taxon richness were eight and ten times higher in the organically enriched sediments near Barentsburg, and total PAH concentrations were up to three times higher in Barentsburg. Unlike expectations derived from models developed for temperate regions, organic enrichment in oligotrophic areas, such as this Arctic site, enhanced the biomass and bioturbation potential of benthic communities. Hence, new insights into the relationships among enrichment, benthic communities and the fate of contaminants must be considered in management and regulatory efforts in these areas.

  12. Soil Penetration by Earthworms and Plant Roots--Mechanical Energetics of Bioturbation of Compacted Soils.

    Directory of Open Access Journals (Sweden)

    Siul Ruiz

    Full Text Available We quantify mechanical processes common to soil penetration by earthworms and growing plant roots, including the energetic requirements for soil plastic displacement. The basic mechanical model considers cavity expansion into a plastic wet soil involving wedging by root tips or earthworms via cone-like penetration followed by cavity expansion due to pressurized earthworm hydroskeleton or root radial growth. The mechanical stresses and resulting soil strains determine the mechanical energy required for bioturbation under different soil hydro-mechanical conditions for a realistic range of root/earthworm geometries. Modeling results suggest that higher soil water content and reduced clay content reduce the strain energy required for soil penetration. The critical earthworm or root pressure increases with increased diameter of root or earthworm, however, results are insensitive to the cone apex (shape of the tip. The invested mechanical energy per unit length increase with increasing earthworm and plant root diameters, whereas mechanical energy per unit of displaced soil volume decreases with larger diameters. The study provides a quantitative framework for estimating energy requirements for soil penetration work done by earthworms and plant roots, and delineates intrinsic and external mechanical limits for bioturbation processes. Estimated energy requirements for earthworm biopore networks are linked to consumption of soil organic matter and suggest that earthworm populations are likely to consume a significant fraction of ecosystem net primary production to sustain their subterranean activities.

  13. Soil Penetration by Earthworms and Plant Roots--Mechanical Energetics of Bioturbation of Compacted Soils.

    Science.gov (United States)

    Ruiz, Siul; Or, Dani; Schymanski, Stanislaus J

    2015-01-01

    We quantify mechanical processes common to soil penetration by earthworms and growing plant roots, including the energetic requirements for soil plastic displacement. The basic mechanical model considers cavity expansion into a plastic wet soil involving wedging by root tips or earthworms via cone-like penetration followed by cavity expansion due to pressurized earthworm hydroskeleton or root radial growth. The mechanical stresses and resulting soil strains determine the mechanical energy required for bioturbation under different soil hydro-mechanical conditions for a realistic range of root/earthworm geometries. Modeling results suggest that higher soil water content and reduced clay content reduce the strain energy required for soil penetration. The critical earthworm or root pressure increases with increased diameter of root or earthworm, however, results are insensitive to the cone apex (shape of the tip). The invested mechanical energy per unit length increase with increasing earthworm and plant root diameters, whereas mechanical energy per unit of displaced soil volume decreases with larger diameters. The study provides a quantitative framework for estimating energy requirements for soil penetration work done by earthworms and plant roots, and delineates intrinsic and external mechanical limits for bioturbation processes. Estimated energy requirements for earthworm biopore networks are linked to consumption of soil organic matter and suggest that earthworm populations are likely to consume a significant fraction of ecosystem net primary production to sustain their subterranean activities.

  14. Bioturbation enhances the aerobic respiration of lake sediments in warming lakes.

    Science.gov (United States)

    Baranov, Viktor; Lewandowski, Jörg; Krause, Stefan

    2016-08-01

    While lakes occupy less than 2% of the total surface of the Earth, they play a substantial role in global biogeochemical cycles. For instance, shallow lakes are important sites of carbon metabolism. Aerobic respiration is one of the important drivers of the carbon metabolism in lakes. In this context, bioturbation impacts of benthic animals (biological reworking of sediment matrix and ventilation of the sediment) on sediment aerobic respiration have previously been underestimated. Biological activity is likely to change over the course of a year due to seasonal changes of water temperatures. This study uses microcosm experiments to investigate how the impact of bioturbation (by Diptera, Chironomidae larvae) on lake sediment respiration changes when temperatures increase. While at 5°C, respiration in sediments with and without chironomids did not differ, at 30°C sediment respiration in microcosms with 2000 chironomids per m(2) was 4.9 times higher than in uninhabited sediments. Our results indicate that lake water temperature increases could significantly enhance lake sediment respiration, which allows us to better understand seasonal changes in lake respiration and carbon metabolism as well as the potential impacts of global warming. PMID:27484649

  15. Bioturbational structures record environmental changes in the upwelling area off Vietnam (South China Sea) for the last 150,000 years

    NARCIS (Netherlands)

    Wetzel, A.; Tjallingii, R.; Wiesner, M.G.

    2011-01-01

    The sediments in the upwelling area off central Vietnam are totally bioturbated and display a low-diverse assemblage of bioturbational structures. During interglacial times (Marine Isotope Stage MIS 1, 5a, 5c, 5e), summer monsoon leads to pronounced upwelling and seasonally pulsed arrival of organic

  16. Bioturbation and dissolved organic matter enhance contaminant fluxes from sediment treated with powdered and granular activated carbon

    NARCIS (Netherlands)

    Kupryianchyk, D.; Noori, A.; Rakowska, M.I.; Grotenhuis, J.T.C.; Koelmans, A.A.

    2013-01-01

    Sediment amendment with activated carbon (AC) is a promising technique for in situ sediment remediation. To date it is not clear whether this technique sufficiently reduces sediment-to-water fluxes of sediment-bound hydrophobic organic chemicals (HOCs) in the presence of bioturbators. Here, we repor

  17. Bioturbation determines the response of benthic ammonia-oxidizing microorganisms to ocean acidification.

    Science.gov (United States)

    Laverock, B; Kitidis, V; Tait, K; Gilbert, J A; Osborn, A M; Widdicombe, S

    2013-01-01

    Ocean acidification (OA), caused by the dissolution of increasing concentrations of atmospheric carbon dioxide (CO2) in seawater, is projected to cause significant changes to marine ecology and biogeochemistry. Potential impacts on the microbially driven cycling of nitrogen are of particular concern. Specifically, under seawater pH levels approximating future OA scenarios, rates of ammonia oxidation (the rate-limiting first step of the nitrification pathway) have been shown to dramatically decrease in seawater, but not in underlying sediments. However, no prior study has considered the interactive effects of microbial ammonia oxidation and macrofaunal bioturbation activity, which can enhance nitrogen transformation rates. Using experimental mesocosms, we investigated the responses to OA of ammonia oxidizing microorganisms inhabiting surface sediments and sediments within burrow walls of the mud shrimp Upogebia deltaura. Seawater was acidified to one of four target pH values (pHT 7.90, 7.70, 7.35 and 6.80) in comparison with a control (pHT 8.10). At pHT 8.10, ammonia oxidation rates in burrow wall sediments were, on average, fivefold greater than in surface sediments. However, at all acidified pH values (pH ≤ 7.90), ammonia oxidation rates in burrow sediments were significantly inhibited (by 79-97%; p < 0.01), whereas rates in surface sediments were unaffected. Both bacterial and archaeal abundances increased significantly as pHT declined; by contrast, relative abundances of bacterial and archaeal ammonia oxidation (amoA) genes did not vary. This research suggests that OA could cause substantial reductions in total benthic ammonia oxidation rates in coastal bioturbated sediments, leading to corresponding changes in coupled nitrogen cycling between the benthic and pelagic realms.

  18. Crayfish and fish as bioturbators of streambed sediments: Assessing joint effects of species with different mechanistic abilities

    Science.gov (United States)

    Statzner, Bernhard; Sagnes, Pierre

    2008-01-01

    Many studies illustrate that bioturbating animal species individually affect aquatic sediments through diverse mechanistic abilities, whereas assessments of joint effects of such species on sediments are relatively rare. Such joint effects have implications for real systems, in which different bioturbators coexist, but are difficult to predict for two reasons. First, they can be additive (being the sum of the individual effects of each species) or they can be positive or negative interactive (being greater or smaller than the sum of the individual effects). Second, if interactive, they can depend on biotic interactions that affect the bioturbating activities of the species and/or they can depend on physical interactions among bioturbator-induced sediment modifications. Using experimental streams, we assessed such joint effects on gravel-sand sediments for flow and sediment conditions preferred by barbel ( Barbus barbus) but also used by gudgeon ( Gobio gobio) and, in a second experiment, for flow and sediment conditions preferred by both male crayfish ( Orconectes limosus) and gudgeon. These species have different mechanistic abilities to affect gravel and/or sand in stream beds. In each experiment, we measured (i) the transport of gravel and sand at baseflow (during 12 experimental days); (ii) four sediment surface characteristics (after 12 d); and (iii) the critical shear stress ( τc) causing incipient gravel and sand motion during experimental floods (after 12 d). Gudgeon contributed differently to the joint effects in the two experiments, which related to its individual weight, prevailing baseflow shear stress, sediment particle weight, and sediment mixture (availability of surface sand). Overall, the species pairs had predominantly negative interactive joint effects on the sediment variables assessed by us. Both a literature survey and observations during the experiments provided no evidence for direct biotic interactions between barbel and gudgeon or

  19. Late Quaternary spatial and temporal variability in Arctic deep-sea bioturbation and its relation to Mn cycles

    OpenAIRE

    Löwemark, Ludvig; Hanebuth, T J J; O'Regan, M.; Jakobsson, M.

    2012-01-01

    Changes in intensity and composition of bioturbation and trace fossils in deep-sea settings are directly related to changes in environmental parameters such as food availability, bottom water oxygenation, or substrate consistency. Because trace fossils are practically always preserved in situ, and are often present in environments where other environmental indicators are scarce or may have been compromised or removed by diagenetic processes, the trace fossils provide an important ...

  20. The mechanics and energetics of soil bioturbation by earthworms and plant roots - Impacts on soil structure generation and maintenance

    Science.gov (United States)

    Or, Dani; Ruiz, Siul; Schymanski, Stanlislaus

    2015-04-01

    Soil structure is the delicate arrangement of solids and voids that facilitate numerous hydrological and ecological soil functions ranging from water infiltration and retention to gaseous exchange and mechanical anchoring of plant roots. Many anthropogenic activities affect soil structure, e.g. via tillage and compaction, and by promotion or suppression of biological activity and soil carbon pools. Soil biological activity is critical to the generation and maintenance of favorable soil structure, primarily through bioturbation by earthworms and root proliferation. The study aims to quantify the mechanisms, rates, and energetics associated with soil bioturbation, using a new biomechanical model to estimate stresses required to penetrate and expand a cylindrical cavity in a soil under different hydration and mechanical conditions. The stresses and soil displacement involved are placed in their ecological context (typical sizes, population densities, burrowing rates and behavior) enabling estimation of mechanical energy requirements and impacts on soil organic carbon pool (in the case of earthworms). We consider steady state plastic cavity expansion to determine burrowing pressures of earthworms and plant roots, akin to models of cone penetration representing initial burrowing into soil volumes. Results show that with increasing water content the strain energy decreases and suggest trade-offs between cavity expansion pressures and energy investment for different root and earthworm geometries and soil hydration. The study provides a quantitative framework for estimating energy costs of bioturbation in terms of soil organic carbon or the mechanical costs of soil exploration by plant roots as well as mechanical and hydration limits to such activities.

  1. Transport of fallout radiocesium in the soil by bioturbation. A random walk model and application to a forest soil with a high abundance of earthworms

    International Nuclear Information System (INIS)

    It is well known that bioturbation can contribute significantly to the vertical transport of fallout radionuclides in grassland soils. To examine this effect also for a forest soil, activity-depth profiles of Chernobyl-derived 134Cs from a limed plot (soil, hapludalf under spruce) with a high abundance of earthworms (Lumbricus rubellus) in the Olu horizon (thickness=3.5 cm) were evaluated and compared with the corresponding depth profiles from an adjacent control plot. For this purpose, a random-walk based transport model was developed, which considers (1) the presence of an initial activity-depth distribution, (2) the deposition history of radiocesium at the soil surface, (3) individual diffusion/dispersion coefficients and convection rates for the different soil horizons, and (4) mixing by bioturbation within one soil horizon. With this model, the observed 134Cs-depth distribution at the control site (no bioturbation) and at the limed site could be simulated quite satisfactorily. It is shown that the observed, substantial long-term enrichment of 134Cs in the bioturbation horizon can be modeled by an exceptionally effective diffusion process, combined with a partial reflection of the randomly moving particles at the two borders of the bioturbation zone. The present model predicts significantly longer residence times of radiocesium in the organic soil layer of the forest soil than obtained from a first-order compartment model, which does not consider bioturbation explicitly

  2. Biomantling and bioturbation by colonies of the Florida harvester ant, Pogonomyrmex badius.

    Science.gov (United States)

    Tschinkel, Walter R

    2015-01-01

    In much of the world, soil-nesting ants are among the leading agents of biomantling and bioturbation, depositing excavated soil on the surface or in underground chambers. Colonies of the Florida harvester ant, Pogonomyrmex badius excavate a new nest once a year on average, depositing 0.1 to 12 L (3 L average) of soil on the surface. Repeated surveys of a population of about 400 colonies yielded the frequency of moves (approximately once per year), the distance moved (mean 4 m), and the direction moved (random). The area of the soil disc correlated well with the volume and maximum depth of the nest, as determined by excavation and mapping of chambers. The population-wide frequency distribution of disc areas thus yielded the frequency distribution of nest volumes and maximum depths. For each surveyed colony, the volume of soil excavated from six specified depth ranges and deposited on the surface was estimated. These parameters were used in a simulation to estimate the amount of soil mantled over time by the observed population of P. badius colonies. Spread evenly, P. badius mantling would create a soil layer averaging 0.43 cm thick in a millennium, with 10-15% of the soil deriving from depths greater than 1 m. Biomantling by P. badius is discussed in the context of the ant community of which it is a part, and in relation to literature reports of ant biomantling.

  3. Biomantling and bioturbation by colonies of the Florida harvester ant, Pogonomyrmex badius.

    Directory of Open Access Journals (Sweden)

    Walter R Tschinkel

    Full Text Available In much of the world, soil-nesting ants are among the leading agents of biomantling and bioturbation, depositing excavated soil on the surface or in underground chambers. Colonies of the Florida harvester ant, Pogonomyrmex badius excavate a new nest once a year on average, depositing 0.1 to 12 L (3 L average of soil on the surface. Repeated surveys of a population of about 400 colonies yielded the frequency of moves (approximately once per year, the distance moved (mean 4 m, and the direction moved (random. The area of the soil disc correlated well with the volume and maximum depth of the nest, as determined by excavation and mapping of chambers. The population-wide frequency distribution of disc areas thus yielded the frequency distribution of nest volumes and maximum depths. For each surveyed colony, the volume of soil excavated from six specified depth ranges and deposited on the surface was estimated. These parameters were used in a simulation to estimate the amount of soil mantled over time by the observed population of P. badius colonies. Spread evenly, P. badius mantling would create a soil layer averaging 0.43 cm thick in a millennium, with 10-15% of the soil deriving from depths greater than 1 m. Biomantling by P. badius is discussed in the context of the ant community of which it is a part, and in relation to literature reports of ant biomantling.

  4. A new method for measuring bioturbation rates in sandy tidal flat sediments based on luminescence dating

    DEFF Research Database (Denmark)

    Madsen, Anni T.; Murray, Andrew S.; Jain, Mayank;

    2011-01-01

    The rates of post-depositional mixing by bioturbation have been investigated using Optically Stimulated Luminescence (OSL) dating in two sediment cores (BAL2 and BAL5), retrieved from a sandy tidal flat in the Danish part of the Wadden Sea. A high-resolution chronology, consisting of thirty-six OSL...... ages with ages ranging between 2 ± 4 and 410 ± 20 years, is presented. Slices of sediment (1–2 cm thick) have been dated at least every 5 cm, and from these data mixing depths of 20 cm and 22 cm (BAL5 and BAL2, respectively) are readily identified. Below the mixing zone there is a significant decrease....... The significant change in sedimentation rates at BAL5 may indicate an offset in OSL age of up to 620 years. This paper uses a simple conceptual model for vertical mixing in which all the sediment excreted at the surface by lugworms is assumed to be completely reset before being re-incorporated in the sediment...

  5. A new method for measuring bioturbation rates in sandy tidal flat sediments based on luminescence dating

    DEFF Research Database (Denmark)

    Madsen, Anni Tindahl; Murray, Andrew S.; jain, A;

    2011-01-01

    The rates of post-depositional mixing by bioturbation have been investigated using Optically Stimulated Luminescence (OSL) dating in two sediment cores (BAL2 and BAL5), retrieved from a sandy tidal flat in the Danish part of the Wadden Sea. A high-resolution chronology, consisting of thirty-six OSL...... ages with ages ranging between 2 4 and 410 20 years, is presented. Slices of sediment (1e2 cm thick) have been dated at least every 5 cm, and from these data mixing depths of 20 cm and 22 cm (BAL5 and BAL2, respectively) are readily identified. Below the mixing zone there is a significant decrease....... The significant change in sedimentation rates at BAL5 may indicate an offset in OSL age of up to 620 years. This paper uses a simple conceptual model for vertical mixing in which all the sediment excreted at the surface by lugworms is assumed to be completely reset before being re-incorporated in the sediment...

  6. The Mechanics and Energetics of Soil Bioturbation by Plant Roots and Earthworms - Plastic Deformation Considerations

    Science.gov (United States)

    Ruiz, Siul; Or, Dani; Schymanski, Stanislaus

    2014-05-01

    Soil structure plays a critical factor in the agricultural, hydrological and ecological functions of soils. These services are adversely impacted by soil compaction, a damage that could last for many years until functional structure is restored. An important class of soil structural restoration processes are related to biomechanical activity associated with burrowing of earthworms and root proliferation in impacted soil volumes. We study details of the mechanical processes and energetics associated with quantifying the rates and mechanical energy required for soil structural restoration. We first consider plastic cavity expansion to describe earthworm and plant root radial expansion under various conditions. We then use cone penetration models as analogues to wedging induced by root tip growth and worm locomotion. The associated mechanical stresses and strains determine the mechanical energy associated with bioturbation for different hydration conditions and root/earthworm geometries. Results illustrate a reduction in strain energy with increasing water content and trade-offs between pressure and energy investment for various root and earthworm geometries. The study provides the basic building blocks for estimating rates of soil structural alteration, the associated energetic requirements (soil carbon, plant assimilates) needed to sustain structure regeneration by earthworms and roots, and highlights potential mechanical cut-offs for such activities.

  7. Nest building activity and bioturbation of the ant Lasius niger (L.).

    Science.gov (United States)

    Tůma, Jiří; Frouz, Jan

    2015-04-01

    The ants are called ecosystem engineers as they represents a significant group of bioturbation organisms in the soil. The ants can relocate considerable amount of soil material during their nest building activity. We can then record different soil properties inside and outside of the ant nest and thus ants contribute on mediating soil fertility. The ants are group of social insects with complex behavioural patterns which are self-organized. If we want to know which factors are determining these patterns in the nest building activity, we must study the construction process of the nest itself. Here, we are presenting the results of the nest building experiment with the ant Lasius niger (L.) in artificial formicaria with various combinations of materials. We found a negative effect of the fine material on building the underground structures. The width of the one-way tunnels was positively correlated with the maximum spread of the ant antennae. There was proportionally more excavated volume represented by chambers than by tunnels. The volume of excavated space decreased with the depth of the formicaria. We discuss here the relocation of the material in both vertical directions in our experiment. The ants excavated 56,17 cm3 of the space on the average, which represents 17,38 % of the total volume of the material in the formicaria. Finally, the volume of the excavated space correlated positively with the maximal reached depth of the formicaria as well as with the life span of the ant colony.

  8. A new tracer technique for in situ experimental study of bioturbation processes

    International Nuclear Information System (INIS)

    An experimental method has been developed to study material and radioactivity fluxes at the sediment-water interface and in the sedimentary column. This method has been applied in the Gulf of Fos, an area that is affected by deposits from the river Rhone, and where biodeposition products, resulting from the presence of intensive mussel cultures, can induce a concentration of trace elements at the sediment-water interface. Sediment surface materials were labelled with a mixture of radionuclides (Cerium-144, Cobalt-60 and Cesium-137), in experimental cores filled either with sediment containing in situ fauna or with defaunated sediment. The coupling of this mixture with inert colored sediment particles enabled us to measure radionuclide flux in both solute fraction and solid fraction. At the sediment-water interface, the tracer balance indicates that migrations into deeper sediment are estimated to be until 25 times greater in presence of macrofauna, depending on the tracer examined. Bioturbation may equally enhance exportation to the water column, to a factor ranging from 1.5 to 2.0. During a period of 14 days, in presence of macrofauna, we observed a migration of radionuclides to a maximum depth of 11 cm. A similar distribution pattern of luminophores at the same sediment depths indicates the preponderance of particle reworking in migration. (Author)

  9. Bioturbation depths, rates and processes in Massachusetts Bay sediments inferred from modeling of 210Pb and 239 + 240Pu profiles

    Science.gov (United States)

    Crusius, John; Bothner, Michael H.; Sommerfield, Christopher K.

    2004-01-01

    Profiles of 210Pb and 239 + Pu from sediment cores collected throughout Massachusetts Bay (water depths of 36-192 m) are interpreted with the aid of a numerical sediment-mixing model to infer bioturbation depths, rates and processes. The nuclide data suggest extensive bioturbation to depths of 25-35 cm. Roughly half the cores have 210Pb and 239 + 240Pu profiles that decrease monotonically from the surface and are consistent with biodiffusive mixing. Bioturbation rates are reasonably well constrained by these profiles and vary from ~0.7 to ~40 cm2 yr-1. As a result of this extensive reworking, however, sediment ages cannot be accurately determined from these radionuclides and only upper limits on sedimentation rates (of ~0.3 cm yr-1) can be inferred. The other half of the radionuclide profiles are characterized by subsurface maxima in each nuclide, which cannot be reproduced by biodiffusive mixing models. A numerical model is used to demonstrate that mixing caused by organisms that feed at the sediment surface and defecate below the surface can cause the subsurface maxima, as suggested by previous work. The deep penetration depths of excess 210Pb and 239 + 240Pu suggest either that the organisms release material over a range of >15 cm depth or that biodiffusive mixing mediated by other organisms is occurring at depth. Additional constraints from surficial sediment 234Th data suggest that in this half of the cores, the vast majority of the present-day flux of recent, nuclide-bearing material to these core sites is transported over a timescale of a month or more to a depth of a few centimeters below the sediment surface. As a consequence of the complex mixing processes, surface sediments include material spanning a range of ages and will not accurately record recent changes in contaminant deposition.

  10. Effects of Lumbriculus variegatus (Annelida, Oligochaete) bioturbation on zinc sediment chemistry and toxicity to the epi-benthic invertebrate Chironomus tepperi (Diptera: Chironomidae).

    Science.gov (United States)

    Colombo, Valentina; Pettigrove, Vincent J; Hoffmann, Ary A; Golding, Lisa A

    2016-09-01

    Classical laboratory-based single-species sediment bioassays do not account for modifications to toxicity from bioturbation by benthic organisms which may impact predictions of contaminated sediment risk to biota in the field. This study aims to determine the effects of bioturbation on the toxicity of zinc measured in a standard laboratory bioassay conducted with chironomid larvae (Chironomus tepperi). The epi-benthic chironomid larvae were exposed to two different levels of sediment contamination (1600 and 1980 mg/kg of dry weight zinc) in the presence or absence of annelid worms (Lumbriculus variegatus) which are known to be tolerant to metal and to have a large impact on sediment properties through bioturbation. Chironomids had 5-6x higher survival in the presence of L. variegatus which shows that bioturbation had a beneficial effect on the chironomid larvae. Chemical analyses showed that bioturbation induced a flux of zinc from the pore water into the water column, thereby reducing the bioavailability of zinc in pore water to the chironomid larvae. This also suggested that pore water was the major exposure path for the chironomids to metals in sediment. During the study, annelid worms (Oligochaetes) produced a thin layer of faecal pellets at the sediment surface, a process known to: (i) create additional adsorption sites for zinc, thus reducing its availability, (ii) increase the microbial abundance that in turn could represent an additional food source for opportunistic C. tepperi larvae, and (iii) modify the microbial community's structure and alter the biogeochemical processes it governs thus indirectly impact zinc toxicity. This study represents a contribution in recognising bioturbating organisms as "ecological engineers" as they directly and indirectly influence metal bioavailability and impact other sediment-inhabiting species. This is significant and should be considered in risk assessment of zinc levels (and other metals) in contaminated sediment

  11. On the quantification of soil bioturbation and soil relocation in a mountainous area in S Spain – testing the potential of single-grain OSL techniques

    NARCIS (Netherlands)

    Román Sánchez, A.; Reimann, T.; Vanwalleghem, T.; Temme, A.J.A.M.; Giráldez, J.V.

    2015-01-01

    Soil formation depends on bedrock, climate, relief, vegetation and time. Bioturbation and colluvial soil re-location are important and significant processes that affect the mechanisms and rate of bedrock weathering. The estimation of the relative fraction of bedrock grains which has been mixed in th

  12. Sediment nickel bioavailability and toxicity to estuarine crustaceans of contrasting bioturbative behaviors--an evaluation of the SEM-AVS paradigm.

    Science.gov (United States)

    Chandler, G Thomas; Schlekat, Christian E; Garman, Emily R; He, Lijian; Washburn, Katherine M; Stewart, Emily R; Ferry, John L

    2014-11-01

    Robust sediment quality criteria require chemistry and toxicity data predictive of concentrations where population/community response should occur under known geochemical conditions. Understanding kinetic and geochemical effects on toxicant bioavailability is key, and these are influenced by infaunal sediment bioturbation. This study used fine-scale sediment and porewater measurement of contrasting infaunal effects on carbon-normalized SEM-AVS to evaluate safe or potentially toxic nickel concentrations in a high-binding Spartina saltmarsh sediment (4%TOC; 35-45 μmol-S2-·g(-1)). Two crustaceans producing sharply contrasting bioturbation--the copepod Amphiascus tenuiremis and amphipod Leptocheirus plumulosus--were cultured in oxic to anoxic sediments with SEM[Ni]-AVS, TOC, porewater [Ni], and porewater DOC measured weekly. From 180 to 750 μg-Ni·g(-1) sediment, amphipod bioturbation reduced [AVS] and enhanced porewater [Ni]. Significant amphipod uptake, mortality, and growth-depression occurred at the higher sediment [Ni] even when [SEM-AVS]/foc suggested acceptable risk. Less bioturbative copepods produced higher AVS and porewater DOC but exhibited net population growth despite porewater [Ni] 1.3-1.7× their aqueous [Ni] LOEC. Copepod aqueous tests with/without dissolved organic matter showed significant aqueous DOC protection, which suggests porewater DOC attenuates sediment Ni toxicity. The SEM[Ni]-AVS relationship was predictive of acceptable risk for copepods at the important population-growth level.

  13. A model for microbial phosphorus cycling in bioturbated marine sediments: Significance for phosphorus burial in the early Paleozoic

    Science.gov (United States)

    Dale, Andrew W.; Boyle, Richard A.; Lenton, Timothy M.; Ingall, Ellery D.; Wallmann, Klaus

    2016-09-01

    A diagenetic model is used to simulate the diagenesis and burial of particulate organic carbon (Corg) and phosphorus (P) in marine sediments underlying anoxic versus oxic bottom waters. The latter are physically mixed by animals moving through the surface sediment (bioturbation) and ventilated by burrowing, tube-dwelling organisms (bioirrigation). The model is constrained using an empirical database including burial ratios of Corg with respect to organic P (Corg:Porg) and total reactive P (Corg:Preac), burial efficiencies of Corg and Porg, and inorganic carbon-to-phosphorus regeneration ratios. If Porg is preferentially mineralized relative to Corg during aerobic respiration, as many previous studies suggest, then the simulated Porg pool is found to be completely depleted. A modified model that incorporates the redox-dependent microbial synthesis of polyphosphates and Porg (termed the microbial P pump) allows preferential mineralization of the bulk Porg pool relative to Corg during both aerobic and anaerobic respiration and is consistent with the database. Results with this model show that P burial is strongly enhanced in sediments hosting fauna. Animals mix highly labile Porg away from the aerobic sediment layers where mineralization rates are highest, thereby mitigating diffusive PO43- fluxes to the bottom water. They also expand the redox niche where microbial P uptake occurs. The model was applied to a hypothetical shelf setting in the early Paleozoic; a time of the first radiation of benthic fauna. Results show that even shallow bioturbation at that time may have had a significant impact on P burial. Our model provides support for a recent study that proposed that faunal radiation in ocean sediments led to enhanced P burial and, possibly, a stabilization of atmospheric O2 levels. The results also help to explain Corg:Porg ratios in the geological record and the persistence of Porg in ancient marine sediments.

  14. Contribution of bioturbation by the red swamp crayfish Procambarus clarkii to the recruitment of bloom-forming cyanobacteria from sediment

    Directory of Open Access Journals (Sweden)

    Yoshimasa YAMAMOTO

    2010-02-01

    Full Text Available The development of cyanobacterial blooms in a small eutrophic pond was monitored along with the potential effect of bioturbation by the red swamp crayfish Procambarus clarkii discussed as well with respect to the recruitment of cyanobacteria from sediment. Cyanobacterial blooms were observed during the early spring and summer. The spring bloom was dominated by Aphanizomenon flos-aquae. Its population density reached the maximum level in late March, thereafter decreasing rapidly and becoming lower than the detection limit from May. When the water temperature exceeded 20 °C in late May, the population density of Microcystis spp. began to increase, and a bloom was formed from July to early August. Anabaena spp. also contributed to the formation of the summer bloom. The population densities of both Microcystis spp. and Anabaena spp. began to decline in mid August. Crayfish were sampled using baited traps from April to November. No sample was obtained in April, whereas crayfish were captured constantly from May to November. They were distributed widely throughout the pond from June, although a large number of crayfish were captured most effectively at a particular point in the pond. The first captures in late May were dominated by males. The sex ratio of the captures was almost 1:1 from June to September, and fell in favor of females from October. The sex ratio reached a minimum (0.2:1 in mid November, when an extremely large number of crayfish were captured at a distinctly warm point. Next, the potential ability of crayfish to promote the recruitment of cyanobacteria from the sediment was examined by performing an incubation experiment. The presence of crayfish in containers of the pond sediment increased the densities of cyanobacteria such as Microcystis spp. and Anabaena spp. However, population densities of cyanobacteria began to decline after the crayfish was removed. Overall, bioturbation by crayfish seemed to be somewhat important in the

  15. Bioturbation, geochemistry and geotechnics of sediments affected by the oxygen minimum zone on the Oman continental slope and abyssal plain, Arabian Sea

    Science.gov (United States)

    Meadows, Azra; Meadows, Peter S.; West, Fraser J. C.; Murray, John M. H.

    2000-01-01

    We investigate the way the oxygen minimum zone (OMZ) alters interactions between bioturbation and sediment geochemistry, and geotechnical properties. Sediments are compared within and below the OMZ on the Oman continental slope and adjacent abyssal plain during the post monsoonal autumn season. Quantitative measurements were made of Eh and pH, of total organic matter (TOM) and carbonate, of water content and shear strength, and of bioturbation structures in vertical profiles of subcores taken from spade-box core samples. The OMZ stations had distinctively low redox conditions and high carbonate content, and different geotechnical properties and different bioturbation structures than stations below the OMZ on the abyssal plain. These differences are related to the degree of anoxia and to water depth. Within the OMZ, Eh, pH and carbonate increased with water depth, and TOM and water content decreased. We also noted the presence of subsurface sediment heterogeneity on the continental slope within the OMZ. In the OMZ, Eh, water content and bioturbation decreased with increasing sediment depth. There was a slight decrease in pH in the top 5 cm at all stations. Shear strength nearly always increased with increasing sediment depth. At each water depth correlations show down-core trends in these parameters, while across all water depths correlations were significant at deeper sediment depths (20-30 cm). An Eh-pH diagram identified two water-depth groupings: 391-1008 and 1265-3396 m. Cluster analysis showed the upper and lower sediment depths form separate clusters, the break occurring at 4-7.5 cm; while there are also distinct clusters related to water depth. We relate our results to bottom-water oxygen concentrations reported by other investigators, and to regional-scale geochemical processes.

  16. Impacts of crab bioturbation and local pollution on sulfate reduction, Hg distribution and methylation in mangrove sediments, Rio de Janeiro, Brazil.

    Science.gov (United States)

    Correia, Raquel Rose Silva; Guimarães, Jean Remy Davée

    2016-08-15

    Mercury (Hg) and methylmercury (MeHg) are highly toxic and poorly studied in mangroves. Burrowing Uca crabs change sediment topography and biogeochemistry and thus may affect Hg distribution and MeHg formation. We studied added (203)Hg distribution, Me(203)Hg formation and sulfate reduction rates (SRR) in sediment aquariums containing Uca leptodactyla; and analyzed profiles of Me(203)Hg formation and SRR in sediment cores from two mangroves with distinct environmental impacts. MeHg formation and SRR were higher in the top (≤6cm) sediment and there was no significant difference in Hg methylation in more or less impacted mangroves. In aquariums, crab bioturbation favored Hg retention in the sediment. In the treatment without crabs, Hg volatilization and water Hg concentrations were higher. Hg methylation was higher in bioturbated aquariums but SRR were similar in both treatments. These findings suggest that bioturbating activity favors Hg retention in sediment but also promotes MeHg formation near the surface. PMID:27269386

  17. Polychaete response to fresh food supply at organically enriched coastal sites: Repercussion on bioturbation potential and trophic structure

    Science.gov (United States)

    Venturini, N.; Pires-Vanin, A. M. S.; Salhi, M.; Bessonart, M.; Muniz, P.

    2011-12-01

    We investigated the vertical distribution, abundance, specific and functional structure of polychaete assemblages at four organically enriched sites. The effects of fresh organic matter input from the water column driving by upwelling were evaluated. Temperature and salinity values indicate the intrusion of South Atlantic Central Water (SACW) in spring, a nutrient-rich water mass. The dominance of the conveyor belt transport (CONV) in the station influenced by SACW, in the spring survey, is associated with fresh organic matter input as indicated by higher amounts of polyunsaturated fatty acids. Conversely, the predominance of the diffusive mixing (DIFF) bioturbation category, in the sites without SACW influence is related to the preferential accumulation of more refractive food resources as indicated by higher concentrations of short chain saturated fatty acids. At the site influenced by SACW, the changes in polychaete assemblages were not all evident during proceeding upwelling conditions, but may persist at the end of the upwelling. Polychaetes in the study area seemed to be limited by the quality but not the quantity of food. The delay in polychaete response to fresh food supply may be related to the organic enrichment and the prevalence of refractory material in the sediments.

  18. Influence of bioturbation on the biogeochemistry of the sediment in the littoral zone of an acidic mine pit lake

    Directory of Open Access Journals (Sweden)

    S. Lagauzère

    2010-10-01

    Full Text Available In the last decades, the mining exploitation of large areas in Lusatia (South-eastern Germany but also in other mining areas worldwide has led to the formation of hundreds of pit lakes. Pyrite oxidation in the surrounding dumps makes many such lakes extremely acidic (pH < 3. The biogeochemical functioning of these lakes is mainly governed by cycling of iron. This represents a relevant ecological problem and intensive research has been conducted to understand the involved biogeochemical processes and develop bioremediation strategies. Despite some studies reporting the presence of living organisms (mostly bacteria, algae, and macro-invertebrates under such acidic conditions, and their trophic interactions, their potential impact on the ecosystem functioning was poorly investigated. The present study aimed to assess the influence of chironomid larvae on oxygen dynamics and iron cycle in the sediment of acidic pit lakes. In the Mining Lake 111, used as a study case since 1996, Chironomus crassimanus (Insecta, Diptera is the dominant benthic macro-invertebrate species and occurs at relatively high abundances in shallow water. A 16-day laboratory experiment using microcosms combined with high resolution measurements (DET gel probes and O2 microsensors was carried out. The burrowing activity of C. crassimanus larvae induced a 3-fold increase of the oxygen consumption by sediment, and stimulated the mineralization of organic matter in the upper layers of the sediment. The iron cycle was also impacted (e.g. lower rates of reduction and oxidation, increase of iron-oxidizing bacteria abundance, stimulation of mineral formation but with no significant effect on the iron flux at the sediment-water interface, and thus on the water acidity budget. This work provides the first assessment of bioturbation in an acidic mining lake and shows that its influence on biogeochemistry cannot be neglected.

  19. Influence of bioturbation on the biogeochemistry of littoral sediments of an acidic post-mining pit lake

    Directory of Open Access Journals (Sweden)

    S. Lagauzère

    2011-02-01

    Full Text Available In the last decades, the mining exploitation of large areas in Lusatia (Eastern Germany but also in other mining areas worldwide has led to the formation of hundreds of pit lakes. Pyrite oxidation in the surrounding dumps makes many such lakes extremely acidic (pH < 3. The biogeochemical functioning of these lakes is mainly governed by cycling of iron. This represents a relevant ecological problem and intensive research has been conducted to understand the involved biogeochemical processes and develop bioremediation strategies. Despite some studies reporting the presence of living organisms (mostly bacteria, algae, and macro-invertebrates under such acidic conditions, and their trophic interactions, their potential impact on the ecosystem functioning was poorly investigated. The present study aimed to assess the influence of chironomid larvae on oxygen dynamics and iron cycle in the sediment of acidic pit lakes. In the Mining Lake 111, used as a study case since 1996, Chironomus crassimanus (Insecta, Diptera is the dominant benthic macro-invertebrate species and occurs at relatively high abundances in shallow water. A 16-day laboratory experiment using microcosms combined with high resolution measurements (DET gel probes and O2 microsensors was carried out. The burrowing activity of C. crassimanus larvae induced a 3-fold increase of the diffusive oxygen uptake by sediment, indicating a stimulation of the mineralization of organic matter in the upper layers of the sediment. The iron cycle was also impacted (e.g. lower rates of reduction and oxidation, increase of iron-oxidizing bacteria abundance, stimulation of mineral formation but with no significant effect on the iron flux at the sediment-water interface, and thus on the water acidity budget. This work provides the first assessment of bioturbation in an acidic mining lake and shows that its influence on biogeochemistry cannot be neglected.

  20. Elemental and mineralogical changes in soils due to bioturbation along an earthworm invasion chronosequence in Northern Minnesota

    Energy Technology Data Exchange (ETDEWEB)

    Resner, Kathryn [Dept. of Soil, Water, and Climate, University of Minnesota, 439 Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN, 55108-6028 (United States); Yoo, Kyungsoo, E-mail: kyoo@umn.edu [Dept. of Soil, Water, and Climate, University of Minnesota, 439 Borlaug Hall, 1991 Upper Buford Circle, St. Paul, MN, 55108-6028 (United States); Hale, Cindy [University of Minnesota Duluth, The Natural Resources Research Institute, 5013 Miller Trunk Hwy. Duluth, MN 55811 (United States); Aufdenkampe, Anthony [Assistant Research Scientist - Isotope and Organic Geochemistry, Stroud Water Research Center, 970 Spencer Road, Avondale, PA 19311 (United States); Blum, Alex [US Geological Survey, 3215 Marine St., Boulder, CO 80303 (United States); Sebestyen, Stephen [Research Hydrologist, USDA Forest Service, Northern Research Station, Grand Rapids, MN 55744-3399 (United States)

    2011-06-15

    Minnesota forested soils have evolved without the presence of earthworms since the last glacial retreat. When exotic earthworms arrive, enhanced soil bioturbation often results in dramatic morphological and chemical changes in soils with negative implications for the forests' sustainability. However, the impacts of earthworm invasion on geochemical processes in soils are not well understood. This study attempts to quantify the role of earthworm invasion in mineral chemical weathering and nutrient dynamics along an earthworm invasion chronosequence in a sugar maple forest in Northern Minnesota. Depth and rates of soil mixing can be tracked with atmospherically derived short lived radioisotopes {sup 210}Pb and {sup 137}Cs. Their radioactivities increase in the lower A horizon at the expense of the peak activities near the soil surface, which indicate that soil mixing rate and its depth reach have been enhanced by earthworms. Enhanced soil mixing by earthworms is consistent with the ways that the vertical profiles of elemental and mineralogical compositions were affected by earthworm invasion. Biologically cycled Ca and P have peak concentrations near the soil surface prior to earthworm invasion. However, these peak abundances significantly declined in the earthworm invaded soils presumably due to enhanced soil mixing. It is clear that enhanced soil mixing due to earthworms also profoundly altered the vertical distribution of most mineral species within A horizons. Though the mechanisms are not clear yet, earthworm invasion appears to have contributed to net losses of clay mineral species and opal from the A horizons. As much as earthworms vertically relocated minerals and elements, they also intensify the contacts between organic matter and cations as shown in the increased amount of Ca and Fe in organically complexed and in exchangeable pools. With future studies on soil mixing rates and elemental leaching, this study will quantitatively and mechanically

  1. Elemental and mineralogical changes in soils due to bioturbation along an earthworm invasion chronosequence in Northern Minnesota

    International Nuclear Information System (INIS)

    Minnesota forested soils have evolved without the presence of earthworms since the last glacial retreat. When exotic earthworms arrive, enhanced soil bioturbation often results in dramatic morphological and chemical changes in soils with negative implications for the forests' sustainability. However, the impacts of earthworm invasion on geochemical processes in soils are not well understood. This study attempts to quantify the role of earthworm invasion in mineral chemical weathering and nutrient dynamics along an earthworm invasion chronosequence in a sugar maple forest in Northern Minnesota. Depth and rates of soil mixing can be tracked with atmospherically derived short lived radioisotopes 210Pb and 137Cs. Their radioactivities increase in the lower A horizon at the expense of the peak activities near the soil surface, which indicate that soil mixing rate and its depth reach have been enhanced by earthworms. Enhanced soil mixing by earthworms is consistent with the ways that the vertical profiles of elemental and mineralogical compositions were affected by earthworm invasion. Biologically cycled Ca and P have peak concentrations near the soil surface prior to earthworm invasion. However, these peak abundances significantly declined in the earthworm invaded soils presumably due to enhanced soil mixing. It is clear that enhanced soil mixing due to earthworms also profoundly altered the vertical distribution of most mineral species within A horizons. Though the mechanisms are not clear yet, earthworm invasion appears to have contributed to net losses of clay mineral species and opal from the A horizons. As much as earthworms vertically relocated minerals and elements, they also intensify the contacts between organic matter and cations as shown in the increased amount of Ca and Fe in organically complexed and in exchangeable pools. With future studies on soil mixing rates and elemental leaching, this study will quantitatively and mechanically address the role of

  2. Oil spill effects on macrofaunal communities and bioturbation of pristine marine sediments (Caleta Valdés, Patagonia, Argentina): experimental evidence of low resistance capacities of benthic systems without history of pollution

    OpenAIRE

    Ferrando, Agustina; Gonzalez, Emilia; Franco, Marcos; Commendatore, Marta; Nievas, Marina; Militon, Cécile; Stora, Georges; Gilbert, Franck; Esteves, José Luis; Cuny, Philippe

    2015-01-01

    The Patagonian coast is characterized by the existence of pristine ecosystems which may be particularly sensitive to oil contamination. In this study, a simulated oil spill at acute and chronic input levels was carried out to assess the effects of contamination on the macrobenthic community structure and the bioturbation activity of sediments sampled in Caleta Valdés creek. Superficial sediments were either noncontaminated or contaminated by Escalante crude oil and incubated in the laboratory...

  3. In situ, high resolution ZrO-Chelex DGT for the investigation of iron-coupled inactivation of arsenic in sediments by macrozoobenthos bioturbation and hydrodynamic interactions.

    Science.gov (United States)

    Yao, Yu; Wang, Chao; Wang, Peifang; Hou, Jun; Wang, Teng; Liu, Cui; Yuan, Ye

    2016-08-15

    The influence of chironomid larvae and hydrodynamics on the bioavailable arsenic (As) in sediments under different conditions was comprehensively investigated through water tank experiments spanning 132days. The high-resolution technique of revealing diffusive gradients in thin films (DGT) with ZrO-Chelex resin was employed in this study; this was done to simultaneously obtain concentrations of labile As and Fe in the profile at millimeter resolution. Bioturbation by larvae may significantly decrease the bioavailable As and Fe concentrations under different hydrodynamic intensities during the first two months of larval burrowing; the greatest difference between the bioavailable As concentration with and without the addition of larvae was seen on the 56th day, with around 49%, 47%, 73% and 67% reduction of As in the profile under static water, 0.3ms(-1), 0.5ms(-1) and 1.0ms(-1), respectively. However, these effects were diminished after the 56th day due to the eclosion of the chironomid larvae. The hydrodynamic conditions appeared to not have any significant effect on the labile concentration of As or Fe until after eclosion. The changing distributions of labile As and Fe were consistent with the dissolved oxygen concentrations in the profile under different conditions. Labile As showed the significantly correlation coefficients with labile Fe by a stepwise multiple linear regression under different experimental conditions in this study. We conclude that the decreases in bioavailable As are directly related to conversions between Fe(2+) and Fe(3). PMID:27107269

  4. Use of total organic carbon, spectral gamma ray and bioturbation as tools in the identification of source rock; Carbono organico total, gamaespectrometria e bioturbacao como ferramentas na busca de possiveis horizontes geradores de hidrocarbonetos

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Anderson S.; Pereira, Egberto [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil). Faculdade de Geologia. Dept. de Estratigrafia e Paleontologia

    2008-07-01

    This work presents the result obtained for the gamaespectrometric study of a borehole situated in north of Parana Basin, concerning sediments of the Ponta Grossa Formation. The Total Radioactivity data and the concentrations of Potassium (K), Uranium (U), Thorium (Th) have been compared to the Total Organic Carbon (TOC) and to the degree of bioturbation intensity. The mentioned formation is composed of basal sandstones deposited in shoreface conditions, which pass to siltstones and black shales deposited in offshore conditions. Nine sedimentary facies were identified based on sedimentological characteristics and sedimentary structures. The bioturbation intensity indicates the modification degree of the initial arrangement of sedimentary beds by the action of organisms. High TOC values in the intervals in addition to the increase of the radioactivity values indicate anoxic conditions. These conditions are ideal for the organic matter concentration and preservation, reflecting favorable intervals to the hydrocarbons (HC) generation. Thus, with the integrated use of diverse tools it was possible to confirm that the Givetian-Frasnian interval of the Ponta Grossa Formation presents the best potential of HC generation of the section analyzed. (author)

  5. Effects of Bioturbation on Vertical Distribution of Sediment Particles by Two Macrobenthos Species%两种大型底栖动物生物扰动对沉积物颗粒垂直分布的影响

    Institute of Scientific and Technical Information of China (English)

    吕洪斌; 王恕桥; 刘国山; 张秀梅

    2016-01-01

    Macrobenthos affect the physical, chemical and biological properties of the sediment-water interface. This bioturbation plays an important role in the biogeochemical processes of marine and lacustrine environments. Research has shown that bioturbation intensity depends on natural macrobenthos behavior, but is influenced by ex-ternal factors such as temperature, salinity, dissolved oxygen, macrobenthos density and food supply.In this stud-y,we investigated the effect of population density of a Polychaeta,Cirratulus chrysoderma, and size of a Bivalvia, Ruditapes philippinarum, on the vertical distribution of sediment particles.The two macrobenthos species were in-vestigated using polyvinyl chloride (PVC) tubes(L28 cm, D10.5 cm) with 15 cm of sediment.Glass beads(0.4-0.5 mm) were placed on the surface of the sediment as the tracer before the organisms were placed in the appa-ratus.The experiment was conducted at a salinity of 30 g/kg, temperature of 20℃and each treatment was run in triplicate.Treatment groups included three densities of C.chrysoderma (255, 510, 1 020 ind/m2),three sizes of R.philippinarum[large: (32.64 ±0.08) mm, (7.34 ±0.45) g;medium: (25.30 ±0.11) mm, (3.54 ± 0.19) g;small:(20.34 ±0.06) mm, (1.63 ±0.13) g)] and a control.The vertical distribution of tracers and macrobenthos for each treatment was determined on day 7 and day 20 of the experiment.The two macrobenthos spe-cies displayed significantly different bioturbation intensities, primarily because they belong to different bioturbation functional groups.The quantity and depth of tracer beads distributed in the sediments changed with C chrysoderma density, R philippinarum size and bioturbation time.The transport rate of tracer beads increased with density of C chrysoderma on day 7, but was negatively correlated on day 20.The transport rate of tracer beads decreased with size of R philippinarum at both sampling time.The maximum depth and number of tracer particles transported in the sediment

  6. Oil spill effects on macrofaunal communities and bioturbation of pristine marine sediments (Caleta Valdés, Patagonia, Argentina): experimental evidence of low resistance capacities of benthic systems without history of pollution.

    Science.gov (United States)

    Ferrando, Agustina; Gonzalez, Emilia; Franco, Marcos; Commendatore, Marta; Nievas, Marina; Militon, Cécile; Stora, Georges; Gilbert, Franck; Esteves, José Luis; Cuny, Philippe

    2015-10-01

    The Patagonian coast is characterized by the existence of pristine ecosystems which may be particularly sensitive to oil contamination. In this study, a simulated oil spill at acute and chronic input levels was carried out to assess the effects of contamination on the macrobenthic community structure and the bioturbation activity of sediments sampled in Caleta Valdés creek. Superficial sediments were either noncontaminated or contaminated by Escalante crude oil and incubated in the laboratory for 30 days. Oil contamination induced adverse effects on macrobenthic community at both concentrations with, for the highest concentration, a marked decrease of approximately 40 and 55 % of density and specific richness, respectively. Besides the disappearance of sensitive species, some other species like Oligochaeta sp. 1, Paranebalia sp., and Ostracoda sp. 2 species have a higher resistance to oil contamination. Sediment reworking activity was also affected by oil addition. At the highest level of contamination, nearly no activity was observed due to the high mortality of macroorganisms. The results strongly suggest that an oil spill in this protected marine area with no previous history of contamination would have a deep impact on the non-adapted macrobenthic community.

  7. 泥鳅对稻田土壤动物的扰动效应%A Preliminary Study on Bioturbation Effects of Misgurnus anguillicaudatus on Soil Animals in Paddy Field.

    Institute of Scientific and Technical Information of China (English)

    孙刚; 房岩; 胡佳林; 王准

    2011-01-01

    2008年6月至1O月,通过田间试验.设置对照稻田和养鱼稻田2个处理,采用分层取样法和大类群分类法,利用反映土壤动物群落结构数量特征的多样性指数、均匀性指数和优势度指数,研究了泥鳅对稻田土壤动物群落的扰动效应.结果表明,稻田土壤动物群落的优势类群为腹足类、线虫类和线蚓类.稻一鱼复合系统土壤动物类群数高于对照稻田,但土壤动物个体数少于对照稻田.稻一鱼复合系统土壤动物多样性指数和均匀性指数高于对照稻田,但优势度指数低于对照稻田,显示稻一鱼复合系统具有更高的稳定性和抗干扰能力.稻田土壤动物的垂直分布具有明显的表聚性.%A field experiment of two treatments (control plot and rice-fish system) was carried out in paddy field during the period from June to October 2008, to study bioturbation effects of Misgurnus anguillicaudatus on soil animal community in paddy field, using the multi-tier sampling method and macro-group classification method, and diversity index, evenness index, and dominance index that represents structural and quantitative characteristics of soil animal community.Results show that the dominant groups in the soil animal community are Gastropoda, Nematoda, and Enchytraeidae.Compared with the control plot, the rice-fish system has more groups but less individuals of soil animals.The diversity index and evenness index of the soil animals are higher, while the dominance index is lower in the rice-fish system than in the control plot, indicating the rice-fish integrated system is higher in stability and resistance against disturbance.Vertically, soil animals in paddy field concentrate mainly in surface soil profile.

  8. Seeing the unseen-bioturbation in 4D

    DEFF Research Database (Denmark)

    Delefosse, Matthieu; Kristensen, Erik; Crunelle, Diane;

    2015-01-01

    Understanding spatial and temporal patterns of bioirrigation induced by benthic fauna ventilation is critical given its significance on benthic nutrient exchange and biogeochemistry in coastal ecosystems. The quantification of this process challenges marine scientists because faunal activities and...... behaviors are concealed in an opaque sediment matrix. Here, we use a hybrid medical imaging technique, positron emission tomography and computed tomography (PET/CT) to provide a qualitative visual and fully quantitative description of bioirrigation in 4D (space and time). As a study case, we present images...... provide information that otherwise would require multiple methods. Furthermore, PET/CT scan is versatile as it can be used for a variety of benthic macrofauna species and sediment types and it provides information on burrow morphology or animal behavior. The lack of accessibility to the expensive...

  9. Influence of Bioturbation of Sipunculus nudus on the Nutrients of Sediment and Pore Water in the Polyculture System of S. nudus and Mugil cephlus%光裸方格星虫(Sipunculus nudus)生物扰动对混养系统沉积物及间隙水中营养物质的影响

    Institute of Scientific and Technical Information of China (English)

    李俊伟; 朱长波; 郭永坚; 颉晓勇; 黄国强; 陈素文

    2015-01-01

    To study the effects of bioturbation of Sipunculus nudus on the sediment and the pore water, we established a polyculture ecosystem consisting of S. nudus and Mugil cephlus in the laboratory conditions. The experiment was conducted in 20 breeding tanks (diameter 1 m, height 0.8 m, water volumn 550 L). S. nudus [mean weight (1.2±0.1) g] was stocked at four different densities in the sandy sediment at the bottom of the tank: 0 (control), 50, 100 and 150 individuals per tank. In each tank 3 juvenile M. cephlus [mean weight (24.5±0.5) g] were cultured with normal ration supply in a net cage (diameter of 0.8 m, height of 0.6 m). The sediment was prepared in layers: the bottom layer was 6 cm thick medium sand (grain size 0.40–1.10 mm), and the top layer was 1 cm thick fine sand (grain size 0.10–0.28 mm). The results showed that the organic content in the bottom sediment (6–8 cm) in the experimental groups was slightly but insignificantly higher than that in the control group (P>0.05). The contents of nitrate nitrogen (NO3-N), ammonia nitrogen (NH4-N) and soluble reactive phosphorus (SRP) in the pore water increased gradually as the experiment lasted. At the end of the experiment, it was found that the NO3-N content in the bottom pore water was negatively correlated with the density of S. nudus, and it was lower in pore water of the T100 and T150 groups than in the T0 group (P0.05)。随着试验的进行,4个试验组的间隙水中硝态氮(NO3-N)、氨氮(NH4-N)以及活性磷(SRP)浓度均呈现出升高的趋势。试验结束时,T100和 T150组各层间隙水的 NO3-N 浓度均低于T0组(P<0.05),且底层间隙水的 NO3-N 浓度随方格星虫密度的增加而降低;T0组表层 NH4-N 浓度高于方格星虫组,而底层氨氮却显著低于高密度方格星虫组(T100和 T150)(P<0.05)。结果表明,方格星虫的生物扰动在一定程度上可以促进沉积物表层的有机质向底层转移,从而影响间隙水中氮、磷营养

  10. Bioturbation of forested shale soils by tree throw in the Appalachian Mountains

    Science.gov (United States)

    Mann, E. A.; Downey, K.; Dere, A. L.; White, T.

    2011-12-01

    Tree throw, the upheaval of bedrock and soil in the root mass of a fallen tree, has been suggested as a major process in the overturn and downslope transport of soils in mountainous regions. The process typically leads to an excavated pit, often with exposed bedrock, and a large mass of rock and soil in the exposed root mass. Through time, the pit fills and soil and rock from the root mass move down slope as the tree and roots decay. Reported here is an effort to quantify the effects of tree throw along a climosequence of sites on shale in the Appalachian Mountains associated with the Susquehanna-Shale Hills Critical Zone Observatory (SSHO). The study includes the following field measurements for tree throws within a 120 meter diameter search area centered on soil pits on ridge tops on the Silurian Clinton Group shale: GPS location, tree girth, relative tree age, tree type, dimensions of pit, azimuth of fall, and slope and azimuth of maximum slope. Five sites were studied: central New York, central Pennsylvania (SSHO), west central Virginia, eastern Tennessee, and northern Alabama. A general north-to-south decreasing trend in total number of tree throws was observed excluding the Virginia site. In Virginia, the total number of tree throws was twice the number observed in New York, which we attribute to the higher elevation setting subjected to the steadiest winds as well as the shallowest soils. The relatively high number of throws in New York is likely tied to glacial till at the site - rooting depth appears to be limited by rock fragments, abundant clay and periodic soil saturation. Trees with the largest girths tend to excavate the largest tree throw pits, a relationship best defined in Alabama where the deepest pits were excavated by large trees that had fallen most recently. Most of the observed tree throws occurred on slopes ranging from 15-31 degrees except in Alabama where tree throws fall on a range of slopes with the highest number at 45 degrees. No strong relationship was observed between the azimuth of fallen trees and the azimuth of maximum slopes. At the New York site, all of the tree throws fell toward the east, suggestive of control by prevailing wind direction on the direction of fall. In Virginia, most of the trees fell to the west, the prevailing slope direction of the study site, though a significant number fell to the northeast, again suggestive of influence by prevailing wind direction. In Tennessee most of the trees fell to the south-southeast, the prevailing slope direction, while in Alabama most of the trees fell to the northwest, compatible with prevailing wind directions; the broader range of azimuth of falls in Alabama is most likely due to the effect of chaotic falls associated with recent tornadoes. These observations of tree throw have been made as part of a broader effort to characterize rates of erosion on shale hill slopes, information that is applicable to understanding the evolution of topography and regolith thickness on shale landscapes. Specifically, our observations are used to verify formulations of volumetric regolith flux due to tree throw.

  11. The effects of bioturbation on nutrient fluxes in lakes subjected to lake restoration

    DEFF Research Database (Denmark)

    Kristensen, Thomas Boll; Reitzel, Kasper; Andersen, Frede Østergaard;

    ) and cores from areas with and areas without an Al layer in Lake Nordborg with benthic macroinvertebrates in natural densities and "natural densities + 2800 Chironomus plumosus m-2" we are investigating the effects of benthic macroinvertebrates on nutrient fluxes and their influence on the effectiveness...

  12. Community structure and bioturbation potential of macrofauna at four North Sea stations with contrasting food supply

    NARCIS (Netherlands)

    Dauwe, B.; Herman, P.M.J.; Heip, C.H.R.

    1998-01-01

    We investigated the macrobenthic faunal composition, vertical distribution, biomass, abundance and trophic structure in 4 North Sea sediments with contrasting quantity and quality of organic matter and with different hydrodynamic environments. The vertical distribution of macrofauna biomass generall

  13. Doomed pioneers: Gravity-flow deposition and bioturbation in marine oxygen-deficient environments

    Science.gov (United States)

    Föilmi, Karl B.; Grimm, Kurt A.

    1990-11-01

    Isolated horizons of Thalassinoides and Gyrolithes burrows appear in exclusive association with gravity-flow deposits within sequences of nonbioturbated hernipelagic sedimentary rocks of the Miocene Monterey Formation of California and the Oligocene-Miocene San Gregorio Formation of Baja California. These burrowed levels are not associated with other ichnogenera such as Zoophycos and Chondrites. We infer a causal relation between gravity flow deposition and the presence of Thalassinoides and Gyrolithes and suggest that these gravity flows entrained thalassinidean crustacea. Upon deposition in oxygen-deficient environments, the surviving borrowers reworked substantial quantities of aminated, commonly organic-rich sediments in an environment from which they were previously excluded. The persistence of or the ecologically rapid return to oxygen-depleted conditions limited the survival time and ecological complexity of the transported infaunal dwellers and rendered them doomed pioneers. Ecological and physiological data support this hypothesis: thalassinidean crustacea have the capability to endure turbulent transport and survive up to 5-7 days of anoxia without being severely limited in their biological activities. The accurate recognition of doomed pioneer trace-fossil assemblages as ephemeral ecological phenomena in otherwise laminated successions may contribute to a better understanding and interpretation of paleo-oxygen levels and basin history.

  14. Testing the potential for improving quality of sediments impacted by mussel farms using bioturbating polychaete worms

    DEFF Research Database (Denmark)

    Bergström, Per; Carlsson, Marita S; Lindegarth, Mats;

    2015-01-01

    Biodeposits from farmed mussels severely influence the biogeochemistry of sediments by increasing the levels of organic matter (OM). Mitigation of such negative impacts is important for the development of sustainable aquaculture operations. As a step towards developing methods for remediation...... of coastal sediments affected by mussel farming, the effects of the polychaete, Hediste diversicolor was evaluated experimentally. In a series of field- and laboratory experiments we tested hypotheses about the effects of polychaetes on sediment oxygen consumption, nutrient fluxes and sulphide pools under...... of OM. The accumulation of pore water sulphides were reduced and fluxes of nutrients across the sediment-water interface increased. Additional calculations suggest that the effects of polychaetes were mainly indirect and driven by increased microbial activity due to the borrowing activity...

  15. Survival and bioturbation effects of common marine macrofauna in coastal soils newly flooded with seawater

    DEFF Research Database (Denmark)

    Valdemarsen, Thomas Bruun; Quintana, Cintia Organo; Thorsen, Sandra Walløe;

    Low-lying coastal soils are at risk of being permanently flooded due to global sea level rise, but how will these areas develop as habitat for marine species? We conducted an experiment to evaluate the habitat quality of flooded soils for common marine polychaetes (Marenzelleria viridis, Nereis...... diversicolor and Scoloplos armiger). Soil cores were collected at Gyldensteen Beach (Northern Fyn, Denmark), where a 200 ha area is designated for flooding as part of a nature restoration project. Soils cores were experimentally flooded for 1 month before adding polychaetes. We measured the effect...

  16. What is bioturbation? The need for a precise definition for fauna in aquatic sciences

    DEFF Research Database (Denmark)

    Kristensen, Erik; Penha-Lopes, Gil; Delefosse, Matthieu;

    2012-01-01

    The term ‘bioturbation’ is frequently used to describe how living organisms affect the substratum in which they live. A closer look at the aquatic science literature reveals, however, an inconsistent usage of the term with increasing perplexity in recent years. Faunal disturbance has often been...

  17. A model of fluff layer erosion and subsequent bed erosion in the presence of the bioturbator, Hydrobia ulvae

    OpenAIRE

    Orvain, Francis; Le Hir, Pierre; Sauriau, Pierre-guy

    2003-01-01

    Previous studies have shown that the gastropod Hydrobia ulvae destabilizes the top layers of fine-grained sediments. This process is mediated by the formation of a "biogenic" fluff layer that includes tracks, faecal pellets and mucus. This fluff layer has been shown to be easily resuspended before general bed erosion. In order to examine how fluff layer and bed. erosion interact, flume experiments were performed with fluid sediments of varying water contents. Ten thousand snails were placed a...

  18. The impact of bioturbation by small mammals on heavy metal redistribution in an embanked floodplain of the River Rhine

    NARCIS (Netherlands)

    Wijnhoven, S.; Thonon, I.; Velde, G.D.; Leuven, R.; Zorn, M.; Eijsackers, H.J.P.; Smits, T.

    2006-01-01

    Floodplains along large European rivers are diffusely polluted with heavy metals due to emissions in the past. Because of low mobility of heavy metals in floodplain soils and improvements of water quality, these pollutants will remain in place, and can gradually become covered with less contaminated

  19. Ichnofabric stacking pattern significance for stratigraphic correlation within highly bioturbated marine siliciclastics: case study from the Varg Field Southern Viking Graben, Norwegian sector

    Energy Technology Data Exchange (ETDEWEB)

    Siggerud, E.I.H.; Dexter, J.R.; Whitaker, M.F.; Spencer, P.A.

    1999-07-01

    This presentation discusses the following items: (1) Use of trace fossils, (2) Ichnofabric stacking patterns, (3) The Varg Field, (4) Reservoir description, (5) Varg Field ichnofabrics, and (6) Varg sequence stratigraphy. The presentation focuses on the use of trace fossilanalysis and the recognition of ichnofabrics from conventional cores in the Varg Field.

  20. 心形海胆的生物扰动对沉积物颗粒垂直分布的影响%The Effect of Bioturbation of Echinocardium cordatum (Pennant,1777) on Vertical Distribution of Sediment Particles

    Institute of Scientific and Technical Information of China (English)

    于子山; 张志南; 韩洁; 周宇

    2000-01-01

    以玻璃珠作为示踪颗粒,研究渤海大型底栖动物心形海胆对沉积物的扰动.海上实验的结果表明,在整个实验周期10 d内,沉积物表层的示踪颗粒有41%悬浮进入水体;有20%的颗粒由沉积物表层垂直向下移动,最大迁移深度为6-7.5 cm,垂直迁移率为8.2×10-3g-1·cm-2·d-1.

  1. Seagrass meadows on tropical Indo-pacific reef islands: How do water motion and water depth relate to seagrass species composition, and are seagrass communities really controlled by shrimp bioturbation ?

    OpenAIRE

    Kneer, Dominik; Priosambodo, Dody; Asmus, Harald

    2012-01-01

    Abstract. The present study investigated the distribution pattern of six tropical seagrass species on two coral islands in the Spermonde Archipelago, Indonesia. Shoot density, leaf area index, biomass and rhizome length of Halophila ovalis, Halodule uninervis, Syringodium isoetifolium, Cymodocea rotundata, Thalassia hemprichii and Enhalus acoroides were related to water motion and water depth. At research sites with high water motion the seagrass sucession was frequently disrupted by blowo...

  2. The impact of sediment reworking by opportunistic chironomids on specialised mayflies

    NARCIS (Netherlands)

    Haas, de E.M.; Kraak, M.H.S.; Koelmans, A.A.; Admiraal, W.

    2005-01-01

    1. Bioturbation, by definition, changes the structure and properties of sediments, thereby altering the environment of the bioturbator and other benthic species. In addition to the indirect effects of sediment reworking (e.g. changes in water quality), bioturbating species may also directly interfer

  3. Invertebrate footprints on detritus processing, bacterial community structure, and spatiotemporal redox profiles

    OpenAIRE

    Hunting, E.R.; Whatley, M. H.; Geest, van der, A.H.M.; Mulder, C; Kraak, M.H.S.; Breure, A M; Admiraal, W.

    2012-01-01

    Detritus processing is driven by a complex interplay between macroinvertebrate and microbial activities. Bioturbation/feeding activities of invertebrates in sediments are known to influence decomposition rates. However, direct effects of invertebrates on bacterial communities and detritus processing remain ill-defined, mainly because identifying interactions between invertebrates and sediments is methodologically challenging. We incubated 5 macroinvertebrate species with various bioturbation/...

  4. Phosphorites from the Oman Margin, ODP Leg 117

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.; Lamboy, M.

    . The phosphate grains occur as coprolites, faecal pellets, spherical and coated grains, micronodules, foraminifer infillings and bone fragments. The sediment levels dominated by phosphate grains are bioturbated and associated with shallow water oxic conditions...

  5. Complex effects of ecosystem engineer loss on benthic ecosystem response to detrital macroalgae

    NARCIS (Netherlands)

    Rossi, F.; Gribsholt, B.; Gazeau, F.; Di Santo, V.; Middelburg, J.J.

    2013-01-01

    Ecosystem engineers change abiotic conditions, community assembly and ecosystem functioning. Consequently, their loss may modify thresholds of ecosystem response to disturbance and undermine ecosystem stability. This study investigates how loss of the bioturbating lugworm Arenicola marina modifies t

  6. Complex Effects of Ecosystem Engineer Loss on Benthic Ecosystem Response to Detrital Macroalgae

    NARCIS (Netherlands)

    Rossi, F.; Gribsholt, B.; Gazeau, F.; Di Santo, V.; Middelburg, J.J.

    2013-01-01

    Ecosystem engineers change abiotic conditions, community assembly and ecosystem functioning. Consequently, their loss may modify thresholds of ecosystem response to disturbance and undermine ecosystem stability. This study investigates how loss of the bioturbating lugworm Arenicola marina modifies t

  7. Effect of Organic Enrichment and Hypoxia on the Biodiversity of Benthic Communities in Narragansett Bay

    Science.gov (United States)

    Excessive input of nitrogen to coastal waters leads to eutrophication and hypoxia that reduce biodiversity and impair key ecosystem services provided by benthic communities; for example, fish and shellfish production, bioturbation, nutrient cycling, and water filtration. Hypoxia ...

  8. Faunal Drivers of Soil Flux Dynamics via Alterations in Crack Structure

    Science.gov (United States)

    DeCarlo, Keita; Caylor, Kelly

    2016-04-01

    Organismal activity, in addition to its role in ecological feedbacks, has the potential to serve as instigators or enhancers of atmospheric and hydrologic processes via alterations in soil structural regimes. We investigated the biomechanical effect of faunal activity on soil carbon dynamics via changes in soil crack structure, focusing on three dryland soil systems: bioturbated, biocompacted and undisturbed soils. Carbon fluxes were characterized using a closed-system respiration chamber, with CO2 concentration differences measured using an infrared gas analyzer (IRGA). Results show that faunal influences play a divergent biomechanics role in bulk soil cracking: bioturbation induced by belowground fauna creates "surficial" (shallow, large, well-connected) networks relative to the "systematic" (deep, moderate, poorly connected) networks created by aboveground fauna. The latter also shows a "memory" of past wetting/drying events in the consolidated soil through a crack layering effect. These morphologies further drive differences in soil carbon flux: under dry conditions, bioturbated and control soils show a persistently high and low mean carbon flux, respectively, while biocompacted soils show a large diurnal trend, with daytime lows and nighttime highs comparable to the control and bioturbated soils, respectively. Overall fluxes under wet conditions are considerably higher, but also more variable, though higher mean fluxes are observed in the biocompacted and bioturbated soils. Our results suggest that the increased surface area in the bioturbated soils create enhanced but constant diffusive processes, whereas the increased thermal gradient in the biocompacted soils create novel convective processes that create high fluxes that are diurnal in nature.

  9. Faunal Influences on Fracture-Induced Carbon Flux Dynamics in Dryland Soils

    Science.gov (United States)

    DeCarlo, K. F.; Caylor, K. K.

    2015-12-01

    Organismal activity, in addition to its role in ecological feedbacks, ha the potential to serve as instigators or enhancers of atmospheric and hydrologic fluxes via alterations in soil structural regimes. We investigated the effect of faunally-induced crack morphology on soil carbon dynamics in three dryland soil systems in central Kenya: bioturbated soils, biocompacted soils, and undisturbed soils. Carbon fluxes were characterized using a closed-system respiration chamber, with CO2 concentration differences measured using an infrared gas analyzer. Results show that faunal influenes play a divergent biomechanical role in bulk soil cracking morphology and topology: macrofauna-induced bioturbation creates shallow, large, well-connected networks relative to those from megaherbivore-induced biocompaction, with the latter showing a "memory" of past drying events through a crack layering effect. These morphologies may further drive differences in soil carbon flux: under dry conditions, bioturbated and control soils show a persistently high and low mean carbon flux, respectively - biocompacted soils suggest a diurnal trend, with daytime lows and nighttime highs comparable to the control and bioturbated soils, respectively. Overall fluxes under wet conditions are considerably higher, but also more variable, though higher mean carbon fluxes are observed in the biocompacted and bioturbated soils. Our results suggest that fracture morphology induced in biocompacted soils may enhance diffusive fluxes that are typical in undisturbed soils to levels that are as high as those from macrofaunal respiration, but that particular physical conditions in fracture morphology and topology may be necessary as a prerequisite.

  10. Burgess shale-type biotas were not entirely burrowed away

    DEFF Research Database (Denmark)

    Gaines, Robert R.; Droser, Mary L.; Orr, Patrick J.;

    2012-01-01

    Burgess Shale-type biotas occur globally in the Cambrian record and offer unparalleled insight into the Cambrian explosion, the initial Phanerozoic radiation of the Metazoa. Deposits bearing exceptionally preserved soft-bodied fossils are unusually common in Cambrian strata; more than 40 are now......, however, suggest a more complex scenario. Ichnologic and microstratigraphic data from Burgess Shale-type deposits indicate that (1) bioturbation exerts a limiting effect on soft-bodied preservation; (2) the observed increase in the depth and extent or bioturbation following the Middle Cambrian would have...

  11. The effect of two endogeic earthworm species on zinc distribution and availability in artificial soil columns

    NARCIS (Netherlands)

    Zorn, M.I.; Gestel, van C.A.M.; Eijsackers, H.J.P.

    2005-01-01

    The objective of this study was to determine the impact of earthworm bioturbation on the distribution and availability of zinc in the soil profile. Experiments were carried out with Allolobophora chlorotica and Aporrectodea caliginosa in 24 perspex columns (0 10 cm), filled with 20-23 cm non-pollute

  12. Effects of carbohydrate source for maintaining a high C:N ratio and fish driven re-suspension on pond ecology and production in periphyton-based freshwater prawn culture systems

    NARCIS (Netherlands)

    Asaduzzaman, M.; Wahab, M.A.; Verdegem, M.C.J.; Adhikary, R.K.; Rahman, S.M.S.; Azim, M.E.; Verreth, J.A.J.

    2010-01-01

    The present research investigated the effect of carbohydrate (CH) source for maintaining a high C:N ratio, and tilapia driven bioturbation on pond ecology, production and economical performances in C/N controlled periphyton-based (C/N-CP) freshwater prawn ponds. Two carbohydrate sources (high-cost t

  13. Denitrification in marine sediments: A model study

    NARCIS (Netherlands)

    Middelburg, J.J.; Soetaert, K.E.R.; Herman, P.M.J.; Heip, C.H.R.

    1996-01-01

    The rate and factors controlling denitrification in marine sediments have been investigated using a prognostic diagenetic model. The model is forced with observed carbon fluxes, bioturbation and sedimentation rates, and bottom water conditions. It can reproduce rates of aerobic mineralization, denit

  14. Occurrence of benthic microbial nitrogen fixation coupled to sulfate reduction in the seasonally hypoxic Eckernförde Bay, Baltic Sea

    DEFF Research Database (Denmark)

    Bertics, V. J.; Löscher, C. R.; Salonen, I.;

    2013-01-01

    correlated with bottom water oxygen concentrations. Other variables that also appeared to play a role in rate determination were bioturbation, bubble irrigation and winter storm events. Molecular analysis demonstrated the presence of nifH sequences related to two known N2 fixing SRB, namely Desulfovibrio...

  15. Biogeochemistry of pyrite and iron sulfide oxidation in marine sediments

    DEFF Research Database (Denmark)

    Schippers, A.; Jørgensen, BB

    2002-01-01

    Pyrite (FeS2) and iron monosulfide (FeS) play a central role in the sulfur and iron cycles of marine sediments, They may be buried in the sediment or oxidized by O-2 after transport by bioturbation to the sediment surface. FeS2 and FeS may also be oxidized within the anoxic sediment in which NO3-...

  16. Obliquity paced contourite cyclicity in Antarctic sediments from the Wilkes Land (Site U1356) during Late Oligocene

    Science.gov (United States)

    Salabarnada, Ariadna; Escutia, Carlota; Nelson, C. Hans; Roehl, Ursula; Jimenez-Espejo, Francisco; Evangelinos, Dimitris; Ikehara, Minoru; McKay, Robert; Lopez, Adrian

    2016-04-01

    Our study on sediment cores from IODP Expedition 318 Site U1356 off the east Antarctic Wilkes Land margin comprises the interval from 641 meters below seafloor (mbsf) to 688 mbsf. Based on the age model, this section spans approximately 1 myr (between 26.2 and 25.2 Ma) during the Late Oligocene. Sediment cores were studied using a detailed facies analyses, X-Ray computed tomography (CT-scans), Scanning electron microscope (SEM) images, X-Ray Fluorescence (XRF) core-scanner data at 2cm resolution, and geochemical mapping. Sedimentary facies during the Late Oligocene are characterized by an alternation between scarcely bioturbated green claystones with variable silty laminations and highly bioturbated pale-brown silty-claystones with carbonate. In agreement, Magnetic Susceptibility (MS) and XRF analyses show a cyclical variation. Low magnetic susceptibility and high Barium (Ba) content characterizes the laminated facies. In contrast, highly bioturbated facies show high MS and high content in Zr/Ti. SEM images reveal that both facies present evidences of current reworking features. We interpret sedimentation during the Late Oligocene in the Wilkes Land margin to be dominated by bottom-currents of varying intensities during glacial and interglacial cycles. Spectral analyses of the XRF Ba and Zr/Ti scans, point to the observed cyclicity (i.e., laminated vs. bioturbated facies) to be paced by obliquity. In addition, the lack of Ice Rafted Debris (IRD) within the studied interval points to a reduced continental East Antarctic Ice Sheet (EAIS).

  17. Denitrification activity is closely linked to the total ambient Fe concentration in mangrove sediments of Goa, India

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, S.O.; Gonsalves, M.J.B.D.; Michotey, V.D.; Bonin, P.C.; LokaBharathi, P.A.

    .W., Mucci, A., 2000. Interactions between metal oxides and species of nitrogen and iodine in bioturbated marine sediments. Geochim Cosmochim Acta 64, 2751–2763. Balaram, V., Ramesh, S.L., Anjaiah, K.V., 1995. Comparative study of the sample decomposition...

  18. Effects of the invasive polychaete, Marenzelleria viridis, on the fate of sediment associated pollutants – a microcosm study with 14C-labelled pyrene

    DEFF Research Database (Denmark)

    Banta, Gary Thomas; Hedman, Jenny Elisabet

    The deep burrowing, invasive spionid polychaete, Marenzelleria spp. (3 sibling species), is rapidly expanding its range in the Baltic Sea ecosystem, increasing the depth of the bioturbated zone dramatically relative to the native benthic community. One concern is the effect of this invasion...

  19. Effects of sediment organic matter quality on bioaccumulation, degradation, and distribution of pyrene in two macrofaunal species and their surrounding sediment

    DEFF Research Database (Denmark)

    Granberg, Maria E.; Selck, Henriette

    2007-01-01

    of sediment-associated pyrene in Nereis diversicolor (Annelida) and Amphiura filiformis (Echinodermata), as well as the combined effect of SOM quality and infaunal bioturbation on pyrene distribution and metabolism in the sediment. After 45 d of exposure, SOM quality almost doubled pyrene bioaccumulation...

  20. Glauconitic deposits at Julegård on the south coast of Bornholm, Denmark dated to the Cambrian

    DEFF Research Database (Denmark)

    Clemmensen, Lars B; Bromley, Richard Granville; Holm, Paul Martin

    2011-01-01

    the deposits belong to the Lower Cambrian Norretorp Member of the Læså Formation. The shallow marine deposits are strongly bioturbated, but only a single ichnoassociation is represented. The ichnogenus is referable to either Trichophycus Miller and Dyer, 1878 or Teichichnus Seilacher, 1955. Rare...

  1. Indirect effects of non-lethal predation on bivalve activity and sediment reworking

    NARCIS (Netherlands)

    Maire, O.; Merchant, J.N.; Bulling, M.; Teal, L.R.; Gremare, A.; Duchene, J.C.; Solan, M.

    2010-01-01

    Deposit-feeders are the dominant bioturbators of aquatic sediments, where they profoundly impact biogeochemical processes, but they are also vulnerable to both lethal and non-lethal predation by a large variety of predators. In this study, we performed a series of experiments to test the effects of

  2. Biology of Pelosina arborescens PEARCEY, 1914, with comparative notes on Astrorhiza limicola SANDAHL, 1857 (Foraminifera: Astrorhizidae)

    DEFF Research Database (Denmark)

    Cedhagen, Tomas

    1993-01-01

    of the test are adaptations that also protect against bioturbation and predation but may restrict the respiratory surface. Field observations and laboratory experiments under anoxic conditions show that P arborescens can live anaerobically. Histological analysis of the protoplasm revealed large amounts...

  3. Effect of macrofauna, oxygen exchange and particle reworking on iron and manganese sediment gogeochemistry: a laboratory experiment

    NARCIS (Netherlands)

    Ferro, I.; Van Nugteren, P.; Middelburg, J.J.; Herman, P.M.J.; Heip, C.H.R.

    2003-01-01

    The impact of bioturbation on iron and manganese cycling in rine sediments was studied in laboratory experiments in which faunal effects which combine in the field (particle mixing and oxygen exchange) were studied separately. Particle mixing and sediment aeration both enhance metal oxide reduction

  4. A novel approach to the assess biotic oxygen consumption in marine sediment communities

    Science.gov (United States)

    Baranov, Victor; Queiros, Ana; Widdicombe, Stephen; Stephens, Nick; Lessin, Gennadi; Krause, Stefan; Lewandowski, Joerg

    2016-04-01

    Bioturbation , the mixing of the sediment matrix by burrowing animals impacts sediment metabolism, including respiration through redistribution of particulate organics, changes in bacterial biota diversity and acitivity, as well as via burrowing fauna's own metabolism. Bioturbation, reflecting faunal activity, is also a proxy for the general sedimentary ecosystem health, and can be impacted by many of emerging marine environmental issues such as ocean acidification, warming and the occurrence of heat waves. Sedimentary oxygen consumption is often taken as a proxy for the activity of bioturbating fauna, but determining baselines can be difficult because of the confounding effects of other fauna and microbes present in sediments, as well as irnorganic processes that consume oxygen. Limitations therefore exist in current methodologies, and numerous confounding factors are hampering progress in this area. Here, we present novel method for the assessment of sediment respiration which is expected to be affected only by the biogenic oxygen consumption (namely aerobic respiration). As long as tracer reduction "immune" to inorganic oxygen consumption, so that measurements using this method can be used, alongside traditional methods, to decouple biological respiration from inorganic oxygen consumption reactions. The tracer is easily detectable, non-toxic and can be applied in systems with constant oxygen supply. The latter allow for incubation without the need to to work with unsealed experimental units, bringing procedural advantage over traditional methods. Consequently assessed bioturbating fauna is not exposed to hypoxia and additional stress. Here, we had applied system for the first time to investigate impacts of a common North-Atlantic bioturbator, the brittle star Amphiura filiformis, - on respiration of marine sediments. Two series of experiments were conducted with animals and sediment collected from Cawsand Bay, Plymouth, UK Preliminary results show that tracer

  5. Palaeoenvironment of Eocene prodelta in Spitsbergen recorded by the trace fossil Phycosiphon incertum

    Directory of Open Access Journals (Sweden)

    Francisco Javier Rodríguez-Tovar

    2014-10-01

    Full Text Available Ichnological, sedimentological and geochemical analyses were conducted on the Eocene Frysjaodden Formation in order to interpret palaeoenvironment prodelta sediments in the Central Basin of Spitsbergen. Phycosiphon incertum is the exclusive ichnotaxon showing differences in size, distribution, abundance and density, and relation to laminated/bioturbated intervals. Large P. incertum mainly occur dispersed, isolated and randomly distributed throughout the weakly laminated/non-laminated intervals. Small P. incertum occur occasionally in patches of several burrows within laminated intervals or as densely packed burrows in thin horizons in laminated intervals or constituting fully bioturbated intervals that are several centimetres thick. Ichnological changes are mainly controlled by oxygenation, although the availability of benthic food cannot be discarded. Changes in oxygenation and rate of sedimentation can be correlated with the registered variations in the Bouma sequence of the distal turbiditic beds within prodeltal shelf sediments.

  6. Modelling Soil Profiles in their Landscape Context.

    Science.gov (United States)

    Kirkby, M. J.

    2015-12-01

    Through models, explores the relationships between the interacting drivers of soil profile evolution. Soil hydrology drives the partition of precipitation between overland flow, shallow subsurface flow and deeper percolation/ lateral flow. Critical parts of this interchange occurs close to the surface, within the zone of strong bioturbation, where inorganic composition is determined by the balance between erosion and weathering rates expressed in the chemical depletion ratio. The intensity of organic matter cycling may also limit the final composition of weathering products. Erosion rates are partly driven by the geomorphic environment, through gradient and hydrology, but also constrained by the degree of soil weathering, through particle size and mineralogy. Weathering rates are determined by water movement below the bioturbation zone and ionic diffusion from parent material, which control the rate of decline with soil depth. These interactions are explored through simple equilibrium and evolutionary models for the soil profile that are applicable across a wide range of geological and climatic environments.

  7. Plutonium in the marine environment at Thule, NW-Greenland after a nuclear weapons accident

    DEFF Research Database (Denmark)

    Dahlgaard, H.; Eriksson, M.; Ilus, E.;

    2001-01-01

    was revisited in August 1997, 29 years after the accident. Water and brown algae data indicate that plutonium is not transported from the contaminated sediments into the surface waters in significant quantities. Sediment core data only indicate minor translocation of plutonium from the accident to the area...... outside Bylot Sound. The present data support an earlier quantification of the sedimentation rate as 2-4 mm per year, i.e. 5-12 cm during the 29 years since the accident. Biological activity has mixed accident plutonium much deeper down, to 20-30 cm, and the 5-12 cm new sediment has been efficiently mixed...... into the contaminated layer. In addition to the classical bioturbation mixing the upper approximate to5 cm, the plutonium data indicate the existence of a deeper bioturbation gradually decreasing with depth. Transfer of plutonium to benthic biota is low leading to 1-2 orders of magnitude lower concentrations in biota...

  8. 宍道湖における17世紀初頭の汽水から淡水への環境変化 : コアのCT画像解析と堆積,C・N・S元素分析による検討

    OpenAIRE

    田村, 嘉之; 丹後, 雅憲; 井内, 美郎; 徳岡, 隆夫

    1996-01-01

    Geohistorical studies show that the environment of Lake Shinji changed from brackish to fresh water around the seventeenth century again. This environmental change is detectable by CT (computed tomography) scanning images and C.N.S elemental analyses of core samples. CT scanning images of core samples suggest that the sediments can be divided into two units, Unit I and II. The uppermost unit I is composed of fine- to very fine-sand and silt layers, with bioturbation and shell fragments. Fine-...

  9. Resuspension and estuarine nutrient cycling: insights from the Neuse River Estuary

    OpenAIRE

    D. R. Corbett

    2010-01-01

    For at least the past several decades, North Carolina's Neuse River Estuary (NRE) has been subject to water quality problems relating to increased eutrophication. Research studies initiated in the past several years have addressed the complex nutrient cycles in this system. Most of this research, however, is concerned with the nutrient processes of the water column and the passive diffusion processes of the benthic sedimentary environment. Resuspension of bottom sediments, by bioturbation, ti...

  10. Utilisation des minéraux sédimentaires argileux pour la reconstitution des variations paléoclimatiques à court terme en Mer d'Arabie

    OpenAIRE

    N. Fagel; Debrabant, P; deMenocal, P.; DEMOULIN, B

    1992-01-01

    During the Late Neogene, the sediments of the Owen ridge (Arabian Sea) were able to record paleoclimatic variations because of tectonic stability and weak bio-turbation. These changes had a powerful influence on the western, northern and northeastern detrital supplies related to monsoon conditions and low-latitude aridity which developed during glaciary stages. In ODP Leg 117 sites, previous studies on the distribution of clay assemblages show a great variety of mineral origins and their fluc...

  11. Plant diversity impacts decomposition and herbivory via changes in aboveground arthropods

    OpenAIRE

    Anne Ebeling; Meyer, Sebastian T.; Maike Abbas; Nico Eisenhauer; Helmut Hillebrand; Markus Lange; Christoph Scherber; Anja Vogel; Alexandra Weigelt; Weisser, Wolfgang W.

    2014-01-01

    Loss of plant diversity influences essential ecosystem processes as aboveground productivity, and can have cascading effects on the arthropod communities in adjacent trophic levels. However, few studies have examined how those changes in arthropod communities can have additional impacts on ecosystem processes caused by them (e.g. pollination, bioturbation, predation, decomposition, herbivory). Therefore, including arthropod effects in predictions of the impact of plant diversity loss on such ...

  12. The influence of hypercapnia and the infaunal brittlestar Amphiura filiformis on sediment nutrient flux – will ocean acidification affect nutrient exchange?

    Directory of Open Access Journals (Sweden)

    S. Widdicombe

    2009-10-01

    Full Text Available Rising levels of atmospheric carbon dioxide and the concomitant increased uptake of this by the oceans is resulting in hypercapnia-related reduction of ocean pH. Research focussed on the direct effects of these physicochemical changes on marine invertebrates has begun to improve our understanding of impacts at the level of individual physiologies. However, CO2-related impairment of organisms' contribution to ecological or ecosystem processes has barely been addressed. The burrowing ophiuroid Amphiura filiformis, which has a physiology that makes it susceptible to reduced pH, plays a key role in sediment nutrient cycling by mixing and irrigating the sediment, a process known as bioturbation. Here we investigate the role of A. filiformis in modifying nutrient flux rates across the sediment-water boundary and the impact of CO2- related acidification on this process. A 40 day exposure study was conducted under predicted pH scenarios from the years 2100 (pH 7.7 and 2300 (pH 7.3, plus an additional treatment of pH 6.8. This study demonstrated strong relationships between A. filiformis density and cycling of some nutrients; activity increases the sediment uptake of phosphate and the release of nitrite and nitrate. No relationship between A. filiformis density and the flux of ammonium or silicate were observed. Results also indicated that, within the timescale of this experiment, effects at the individual bioturbator level appear not to translate into reduced ecosystem influence. However, long term survival of key bioturbating species is far from assured and changes in both bioturbation and microbial processes could alter key biogeochemical processes in future, more acidic oceans.

  13. Restoration of estuarine tidal mudflat sediments after hypoxia

    DEFF Research Database (Denmark)

    Van Colen, Carl; Montserrat, F; Middelburg, JJ;

    facilitative and inhibitive interactions: early colonizers had a positive effect on subsequent colonizers, while later succession species negatively affected the stable conditions created by the early colonizing tube-builders. Transitions between different stages were related to changes in environmental...... surface deposit feeding macrofauna during the first stage, stabilized the sediment and thereby enhanced macrobenthic and nematode recruitment success. Bioturbation impact of later succession species increased oxygen input in the sediment, resulting in an enhanced nitrification, denitrification and energy...

  14. Nereis virens (Annelida: Polychaeta) is not an adequate sentinel species to assess the genotoxic risk (comet assay) of PAH exposure to the environment

    OpenAIRE

    Boeck, M.; Kirsch-Volders, M.

    1997-01-01

    Polychaetes, because of their bioturbation capacity, play an important role in the distribution of anthropogenic contaminants (including polycyclic aromatic hydrocarbons [PAHs]) throughout the sediments. In this work the use of Nereis virens (Annelida: Polychaeta) as a bioindicator to assess the genotoxic risk of PAH exposure for the environment was evaluated. For this purpose the alkaline single cell gel electrophoresis [comet] assay was applied on the coelomocytes of in vivo exposed Nereis ...

  15. Trace fossils from Eocene turbiditic deposits: A case study from the Slovak-Moravian Carpathians

    OpenAIRE

    Starek Dušan; Šimo Vladimír

    2015-01-01

    Well exposed, poorly bioturbated turbiditic sandstones of the Kýčera Beds (Zlín Formation; Eocene) in the Bieščary Quarry contain the deep-sea Nereites ichnofacies. The trace fossils Ophiomorpha rudis, Halopoa annulata and Scolicia strozzii are mainly common in thick-bedded sandstone packages. They represent the Ophiomorpha rudis ichnosubfacies. Paleodiction strozzii, Nereites irregularis, and Zoophycos brianteus occur in a series of thin- to medium bedded fine grained turbiditic sandstones i...

  16. The stratigraphy of cretaceous mudstones in the eastern Fuegian Andes: new data from body and trace fossils

    Directory of Open Access Journals (Sweden)

    Eduardo B. Olivero

    2009-04-01

    Full Text Available The stratigraphy of Cretaceous marine mudstones in the Fuegian Andes, roughly equivalent to Charles Darwin's clay-slate formation, remains a still unsolved problem. Previous records of Albian, Turonian-Coniacian, and Santonian-Campanian bivalves are combined with new findings of the Late Albian inoceramid Inoceramus anglicus Woods, and the Maastrichtian ammonites Diplomoceras sp., Anagaudryceras sp., Maorites densicostatus (Kilian and Reboul, Maorites sp., and Pachydiscus (Neodesmoceras sp. to further constrain the Cretaceous stratigraphy of the eastern Fuegian Andes. In addition, new records of distinctive trace fossils and ichnofabric are meaningful for stratigraphic division and delineation of paleoenvironmental settings in these Cretaceous mudstones. The Lower Cretaceous ichnoassemblage of Chondrites targioni (Brongniart and Zoophycos isp. is consistent with the inferred slope-volcaniclastic apron settings of the Yahgan Formation; Nereites missouriensis (Weller reflects distal basin plain depositional settings for the Beauvoir Formation. In the Upper Cretaceous, the "Estratos de Buen Suceso" record the earliest extensively bioturbated horizons, reflecting prolonged well-oxygenated bottom conditions. In the Bahía Thetis Formation, organic-rich, channel margin or distal basin slaty mudstones record the last occurrence of inoceramid bivalves in the Austral Basin; the generalized absence of trace fossils is consistent with dysoxic bottom conditions. The thoroughly bioturbated Policarpo Formation, records a marked change in paleoceanographic conditions. The strong contrast in the intensity of bioturbation between the Upper Campanian-Maastrichtian Bahía Thetis Formation, almost devoid of trace fossils, and the highly bioturbated Maastrichtian-Danian Policarpo Formation reflects a change from dysoxic-anoxic to well ventilated conditions, probably associated with a cooling trend of bottom waters in the austral deep oceans.

  17. Biological activities relating to the transfer of radionuclides (a) within the sediment fabric, (b) between the sediment and water column

    International Nuclear Information System (INIS)

    A study has been made of the infaunal species present in the N.E. Irish Sea and of their bioturbative effect. A novel technique for estimation of sediment disturbance using magnetic anisotropy measurements was developed and used successfully in a series of laboratory experiments. The results are discussed with regard to the species composition and to the physical environment present in the area of the Irish Sea close to Sellafield, Cumbria, U.K. (author)

  18. Trophic ecology of the sea urchin elucidated from gonad fatty acids composition analysis

    OpenAIRE

    López Jiménez, José Ángel; Barberá, C.; Fernández Jover, D.; González Silvera, D.; Hinz, H; Moranta, J.

    2011-01-01

    Abstract Irregular sea urchins such as the spatangoid Spatangus purpureus are important bioturbators that contribute to natural biogenic disturbance and the functioning of biogeochemical cycles in soft sediments. In the coastal waters of the Balearic Islands S. purpureus occurs in soft red algal beds, and can reach high densities. The diet of S. purpureus is unknown and it is particularly difficult to analyze the stomach contents of this group; therefore, we analyzed the fatty acid...

  19. The importance of biotic entrainment for base flow fluvial sediment transport

    Science.gov (United States)

    Rice, Stephen P.; Johnson, Matthew F.; Mathers, Kate; Reeds, Jake; Extence, Chris

    2016-05-01

    Sediment transport is regarded as an abiotic process driven by geophysical energy, but zoogeomorphological activity indicates that biological energy can also fuel sediment movements. It is therefore prudent to measure the contribution that biota make to sediment transport, but comparisons of abiotic and biotic sediment fluxes are rare. For a stream in the UK, the contribution of crayfish bioturbation to suspended sediment flux was compared with the amount of sediment moved by hydraulic forcing. During base flow periods, biotic fluxes can be isolated because nocturnal crayfish activity drives diel turbidity cycles, such that nighttime increases above daytime lows are attributable to sediment suspension by crayfish. On average, crayfish bioturbation contributed at least 32% (474 kg) to monthly base flow suspended sediment loads; this biotic surcharge added between 5.1 and 16.1 t (0.21 to 0.66 t km-2 yr-1) to the annual sediment yield. As anticipated, most sediment was moved by hydraulic forcing during floods and the biotic contribution from baseflow periods represented between 0.46 and 1.46% of the annual load. Crayfish activity is nonetheless an important impact during baseflow periods and the measured annual contribution may be a conservative estimate because of unusually prolonged flooding during the measurement period. In addition to direct sediment entrainment by bioturbation, crayfish burrowing supplies sediment to the channel for mobilization during floods so that the total biotic effect of crayfish is potentially greater than documented in this study. These results suggest that in rivers, during base flow periods, bioturbation can entrain significant quantities of fine sediment into suspension with implications for the aquatic ecosystem and base flow sediment fluxes. Energy from life rather than from elevation can make significant contributions to sediment fluxes.

  20. Remote sensing of biologically reworked sediments: a laboratory experiment

    OpenAIRE

    Backer, A De; S. Adam; Monbaliu, J.; Toorman, E; Vincx, M.; Degraer, S.

    2009-01-01

    The present study aims to test the application of remote sensing to address the impact of bioturbation on physical sediment properties. Therefore, a laboratory experiment was developed, using microcosms mimicking a marine intertidal water–sediment interface to test the influence of Corophium volutator densities on sediment properties. Three main variables (water content, clay content, and mean grain size) were measured in three treatments (no Corophium, 5,000 Corophium per square meter, and 2...

  1. Biological vs. physical mixing effects on benthic food web dynamics.

    Directory of Open Access Journals (Sweden)

    Ulrike Braeckman

    Full Text Available Biological particle mixing (bioturbation and solute transfer (bio-irrigation contribute extensively to ecosystem functioning in sediments where physical mixing is low. Macrobenthos transports oxygen and organic matter deeper into the sediment, thereby likely providing favourable niches to lower trophic levels (i.e., smaller benthic animals such as meiofauna and bacteria and thus stimulating mineralisation. Whether this biological transport facilitates fresh organic matter assimilation by the metazoan lower part of the food web through niche establishment (i.e., ecosystem engineering or rather deprives them from food sources, is so far unclear. We investigated the effects of the ecosystem engineers Lanice conchilega (bio-irrigator and Abra alba (bioturbator compared to abiotic physical mixing events on survival and food uptake of nematodes after a simulated phytoplankton bloom. The (13C labelled diatom Skeletonema costatum was added to 4 treatments: (1 microcosms containing the bioturbator, (2 microcosms containing the bio-irrigator, (3 control microcosms and (4 microcosms with abiotic manual surface mixing. Nematode survival and subsurface peaks in nematode density profiles were most pronounced in the bio-irrigator treatment. However, nematode specific uptake (Δδ(13C of the added diatoms was highest in the physical mixing treatment, where macrobenthos was absent and the diatom (13C was homogenised. Overall, nematodes fed preferentially on bulk sedimentary organic material rather than the added diatoms. The total C budget (µg C m(-2, which included TO(13C remaining in the sediment, respiration, nematode and macrobenthic uptake, highlighted the limited assimilation by the metazoan benthos and the major role of bacterial respiration. In summary, bioturbation and especially bio-irrigation facilitated the lower trophic levels mainly over the long-term through niche establishment. Since the freshly added diatoms represented only a limited food

  2. Biological vs. physical mixing effects on benthic food web dynamics.

    Science.gov (United States)

    Braeckman, Ulrike; Provoost, Pieter; Moens, Tom; Soetaert, Karline; Middelburg, Jack J; Vincx, Magda; Vanaverbeke, Jan

    2011-01-01

    Biological particle mixing (bioturbation) and solute transfer (bio-irrigation) contribute extensively to ecosystem functioning in sediments where physical mixing is low. Macrobenthos transports oxygen and organic matter deeper into the sediment, thereby likely providing favourable niches to lower trophic levels (i.e., smaller benthic animals such as meiofauna and bacteria) and thus stimulating mineralisation. Whether this biological transport facilitates fresh organic matter assimilation by the metazoan lower part of the food web through niche establishment (i.e., ecosystem engineering) or rather deprives them from food sources, is so far unclear. We investigated the effects of the ecosystem engineers Lanice conchilega (bio-irrigator) and Abra alba (bioturbator) compared to abiotic physical mixing events on survival and food uptake of nematodes after a simulated phytoplankton bloom. The (13)C labelled diatom Skeletonema costatum was added to 4 treatments: (1) microcosms containing the bioturbator, (2) microcosms containing the bio-irrigator, (3) control microcosms and (4) microcosms with abiotic manual surface mixing. Nematode survival and subsurface peaks in nematode density profiles were most pronounced in the bio-irrigator treatment. However, nematode specific uptake (Δδ(13)C) of the added diatoms was highest in the physical mixing treatment, where macrobenthos was absent and the diatom (13)C was homogenised. Overall, nematodes fed preferentially on bulk sedimentary organic material rather than the added diatoms. The total C budget (µg C m(-2)), which included TO(13)C remaining in the sediment, respiration, nematode and macrobenthic uptake, highlighted the limited assimilation by the metazoan benthos and the major role of bacterial respiration. In summary, bioturbation and especially bio-irrigation facilitated the lower trophic levels mainly over the long-term through niche establishment. Since the freshly added diatoms represented only a limited food source

  3. First observations on marine subaqueous soils in "Torre del Cerrano" marine protected area, Adriatic sea (Italy)

    OpenAIRE

    Stefania Cocco; Valeria Cardelli; Silvia Pedicini; Rogeiro Borguete Alves Rafael; Alberto Agnelli; Flavio Fornasier; Fabio Vallarola; Giuseppe Corti

    2015-01-01

    Subaqueous soils have to be studied with proper methodologies, according to a pedological approach and considering the key role of animal bioturbation. Morphological and chemical characteristics of submerged soils found in the MPA of "Torre del Cerrano", Adriatic sea (Italy), have been studied in this way, and we conclude that submarine soils of the MPA are important examples of pedogenesis promoted by animals. Soils from the highly protected marine area hosted a major biodiversity than those...

  4. Taphonomy of a Mysticeti whale in the Lower Pliocene Huelva Sands Formation (Southern Spain)

    OpenAIRE

    Esperante, R.; Muñiz Guinea, F.; Nick, K.E.

    2009-01-01

    This paper reports the occurrence of an incomplete fossil baleen whale skeleton in the Lower Pliocene Huelva Sands Formation (Guadalquivir basin) near the town of Bonares, southwestern Spain. The skeleton was found in the highly bioturbated glauconitic sandstone unit in association with Neopycnodonte cochlear shells. Several morphological features of the mandibles, scapula and vertebrae suggest that the specimen belongs in the suborden Mysticeti, family Balaenopteridae. Most bones show abrasi...

  5. Paleoecology of Early Jurassic Navajo Sandstone Interdune Deposits

    OpenAIRE

    Wilkens, Nathan Daniel

    2008-01-01

    The Lower Jurassic Navajo Sandstone represents a desert that covered more than 366,000 square kilometers. Localized interdune deposits commonly occur along the eastern edge of this desert that include carbonates, bioturbated layers, and plant fossils. Previous studies of these deposits focused on specific fossil types or isolated sites. This study involved a comprehensive analysis of the paleoecology of interdune deposits with an integrated approach combining paleontology, sedimentology and g...

  6. The Laminated Marca Shale: High-Frequency Climate Cycles From the Latest Cretaceous

    Science.gov (United States)

    Davies, A.; Kemp, A. E.; Weedon, G.; Barron, J. A.

    2005-12-01

    The Latest Cretaceous (Maastrichtian) Marca Shale Member, California, displays a well-preserved record of alternating terrigenous and diatomaceous laminae couplets, remarkably similar in lithology to recent laminated sediments from the Gulf of California and Santa Barbara Basin. This similarity, together with the recognition of intra- and inter-annual variability in the diatom flora, implies an annual origin for these couplets. High-resolution backscattered electron imagery has identified two sublaminae types within the varved succession; near monospecific lamina of Chaetoceros-type resting spore and of large Azpeitiopsis morenoensis. The composition and occurrence of these laminae is similar to ENSO forced intra-annual variability of diatom flora along the modern Californian margin. Relative thickness variations in terrigenous and biogenic laminae (proxies for precipitation and productivity respectively) also exhibit similar characteristics to variability in Quaternary varves from the Santa Barbara Basin, shown to be imparted by ENSO forcing. In order to track changes in the levels of bottom water oxygenation within the basin, a bioturbation index was established. Periods when bioturbation was minimal (enhanced benthic anoxia) coincide with times of greatest diatomaceous export flux and also lowest flux of detrital material. Conversely, periods of enhanced bioturbation correspond with reduced diatomaceous export flux and an increased flux of detrital material, comparable with ENSO forced variations in diatomaceous and terrigenous export flux and associated benthic oxygenation levels in Pleistocene varves off the Californian margin. Power spectra obtained from time-series analysis of the bioturbation index and laminae thickness variations exhibit strong signals within the ENSO band. This research implies that high-frequency climate perturbations are inherent components of the climate system and that ENSO-type variability was not confined to the dynamic climate

  7. Decoupled evolution of soft and hard substrate communities during the Cambrian Explosion and Great Ordovician Biodiversification Event.

    Science.gov (United States)

    Buatois, Luis A; Mángano, Maria G; Olea, Ricardo A; Wilson, Mark A

    2016-06-21

    Contrasts between the Cambrian Explosion (CE) and the Great Ordovician Biodiversification Event (GOBE) have long been recognized. Whereas the vast majority of body plans were established as a result of the CE, taxonomic increases during the GOBE were manifested at lower taxonomic levels. Assessing changes of ichnodiversity and ichnodisparity as a result of these two evolutionary events may shed light on the dynamics of both radiations. The early Cambrian (series 1 and 2) displayed a dramatic increase in ichnodiversity and ichnodisparity in softground communities. In contrast to this evolutionary explosion in bioturbation structures, only a few Cambrian bioerosion structures are known. After the middle to late Cambrian diversity plateau, ichnodiversity in softground communities shows a continuous increase during the Ordovician in both shallow- and deep-marine environments. This Ordovician increase in bioturbation diversity was not paralleled by an equally significant increase in ichnodisparity as it was during the CE. However, hard substrate communities were significantly different during the GOBE, with an increase in ichnodiversity and ichnodisparity. Innovations in macrobioerosion clearly lagged behind animal-substrate interactions in unconsolidated sediment. The underlying causes of this evolutionary decoupling are unclear but may have involved three interrelated factors: (i) a Middle to Late Ordovician increase in available hard substrates for bioerosion, (ii) increased predation, and (iii) higher energetic requirements for bioerosion compared with bioturbation. PMID:27247396

  8. Tectonically induced climate and its control on the distribution of depositional systems in a continental foreland basin, Cloverly and Lakota Formations (Lower Cretaceous) of Wyoming, U.S.A.

    Science.gov (United States)

    Elliott, William S.; Suttner, Lee J.; Pratt, Lisa M.

    2007-12-01

    Continental sediments of the Cloverly and Lakota Formations (Lower Cretaceous) in Wyoming are subdivided into three depositional systems: perennial to intermittent alluvial, intermittent to ephemeral alluvial, and playa. Chert-bearing sandstones, conglomerates, carbonaceous mudrocks, blocky mudrocks, and skeletal limestones were deposited by perennial to intermittent alluvial systems. Carbonaceous mudrocks contain abundant wood fragments, cuticle and cortical debris, and other vascular plant remains representing deposition in oxbow lakes, abandoned channels, and on floodplains under humid to seasonal conditions. Intraformational conglomerates, sandstones, bioturbated and blocky mudrocks with caliche nodules, and bioturbated limestones characterize deposition in intermittent to ephemeral alluvial systems. Bioturbated limestones are encased in bioturbated mudrocks with abundant pseudo-slickensides. The presence of caliche nodules in some of the blocky to bioturbated mudrocks is consistent with supersaturation and precipitation of calcium carbonate from groundwater under semi-arid conditions. Caliche nodules, pseudo-slickensides, and carbonate-rich floodplain sediments are interpreted to have been deposited by intermittent to ephemeral alluvial systems under seasonal to semi-arid climatic conditions. Laminated mudrocks, siltstones, vuggy carbonates, bedded to nodular evaporites, pebbly mudrocks, and diamictites were deposited in evaporative alkaline lakes or playas. Pebbly mudrocks and diamictites are interpreted to represent deposition from channelized and unchannelized hyperconcentrated flows on a playa, resulting from intense rain events within the basin. The areal abundance and distribution of these depositional systems change systematically across the overfilled portion of the Early Cretaceous Cordilleran foreland basin in Wyoming. The lower part (A-interval) of the Cloverly and Lakota Formations is characterized by deposits of perennial to intermittent rivers

  9. The evolutionary ecology of biotic association in a megadiverse bivalve superfamily: sponsorship required for permanent residency in sediment.

    Directory of Open Access Journals (Sweden)

    Jingchun Li

    Full Text Available BACKGROUND: Marine lineage diversification is shaped by the interaction of biotic and abiotic factors but our understanding of their relative roles is underdeveloped. The megadiverse bivalve superfamily Galeommatoidea represents a promising study system to address this issue. It is composed of small-bodied clams that are either free-living or have commensal associations with invertebrate hosts. To test if the evolution of this lifestyle dichotomy is correlated with specific ecologies, we have performed a statistical analysis on the lifestyle and habitat preference of 121 species based on 90 source documents. METHODOLOGY/PRINCIPAL FINDINGS: Galeommatoidea has significant diversity in the two primary benthic habitats: hard- and soft-bottoms. Hard-bottom dwellers are overwhelmingly free-living, typically hidden within crevices of rocks/coral heads/encrusting epifauna. In contrast, species in soft-bottom habitats are almost exclusively infaunal commensals. These infaunal biotic associations may involve direct attachment to a host, or clustering around its tube/burrow, but all commensals locate within the oxygenated sediment envelope produced by the host's bioturbation. CONCLUSIONS/SIGNIFICANCE: the formation of commensal associations by Galeommatoidean clams is robustly correlated with an abiotic environmental setting: living in sediments (P < 0.001. Sediment-dwelling bivalves are exposed to intense predation pressure that drops markedly with depth of burial. Commensal galeommatoideans routinely attain depth refuges many times their body lengths, independent of siphonal investment, by virtue of their host's burrowing and bioturbation. In effect, they use their much larger hosts as giant auto-irrigating siphon substitutes. The evolution of biotic associations with infaunal bioturbating hosts may have been a prerequisite for the diversification of Galeommatoidea in sediments and has likely been a key factor in the success of this exceptionally diverse

  10. Urban pollution of sediments: Impact on the physiology and burrowing activity of tubificid worms and consequences on biogeochemical processes.

    Science.gov (United States)

    Pigneret, M; Mermillod-Blondin, F; Volatier, L; Romestaing, C; Maire, E; Adrien, J; Guillard, L; Roussel, D; Hervant, F

    2016-10-15

    In urban areas, infiltration basins are designed to manage stormwater runoff from impervious surfaces and allow the settling of associated pollutants. The sedimentary layer deposited at the surface of these structures is highly organic and multicontaminated (mainly heavy metals and hydrocarbons). Only few aquatic species are able to maintain permanent populations in such an extreme environment, including the oligochaete Limnodrilus hoffmeisteri. Nevertheless, the impact of urban pollutants on these organisms and the resulting influence on infiltration basin functioning remain poorly studied. Thus, the aim of this study was to determine how polluted sediments could impact the survival, the physiology and the bioturbation activity of L. hoffmeisteri and thereby modify biogeochemical processes occurring at the water-sediment interface. To this end, we conducted laboratory incubations of worms, in polluted sediments from infiltration basins or slightly polluted sediments from a stream. Analyses were performed to evaluate physiological state and burrowing activity (X-ray micro-tomography) of worms and their influences on biogeochemical processes (nutrient fluxes, CO2 and CH4 degassing rates) during 30-day long experiments. Our results showed that worms exhibited physiological responses to cope with high pollution levels, including a strong ability to withstand the oxidative stress linked to contamination with heavy metals. We also showed that the presence of urban pollutants significantly increased the burrowing activity of L. hoffmeisteri, demonstrating the sensitivity and the relevance of such a behavioural response as biomarker of sediment toxicity. In addition, we showed that X-ray micro-tomography was an adequate technique for accurate and non-invasive three-dimensional investigations of biogenic structures formed by bioturbators. The presence of worms induced stimulations of nutrient fluxes and organic matter recycling (between +100% and 200% of CO2 degassing rate

  11. Contrasting effects of ecosystem engineering by the cordgrass Spartina maritima and the sandprawn Callianassa kraussi in a marine-dominated lagoon

    Science.gov (United States)

    Pillay, D.; Branch, G. M.; Dawson, J.; Henry, D.

    2011-01-01

    Ecosystem engineering by plants and animals significantly influences community structure and the physico-chemical characteristics of marine habitats. In this paper we document the contrasting effects of ecosystem engineering by the cordgrass Spartina maritima and the burrowing sandprawn Callianassa kraussi on physico-chemical characteristics, microflora, macrofaunal community structure and morphological attributes in the high shore intertidal sandflats of Langebaan Lagoon, a marine-dominated system on the west coast of South Africa. Comparisons were made at six sites in the lagoon within Spartina and Callianassa beds, and in a "bare zone" of sandflat between these two habitats that lacks both sandprawns and cordgrass. Sediments in Spartina habitats were consolidated by the root-shoot systems of the cordgrass, leading to low sediment penetrability, while sediments in beds of C. kraussi were more penetrable, primarily due to the destabilising effects of sandprawn bioturbation. Sediments in the "bare zone" had intermediate to low values of penetrability. Sediment organic content was lowest in bare zones and greatest in Spartina beds, while sediment chl- a levels were greatest on bare sand, but were progressively reduced in the Spartina and Callianassa beds. These differences among habitats induced by ecosystem engineering in turn affected the macrofauna. Community structure was different between all three habitats sampled, with species richness being surprisingly greater in Callianassa beds than either the bare zone or Spartina beds. In general, the binding of surface sediments by the root systems of Spartina favoured rigid-bodied, surface-dwelling and tube-building species, while the destabilising effect of bioturbation by C. kraussi favoured burrowing species. The contrasting effects of these ecosystem engineers suggest that they play important roles in increasing habitat heterogeneity. Importantly, the role of bioturbation by C. kraussi in enhancing macrofaunal

  12. Metal-macrofauna interactions determine microbial community structure and function in copper contaminated sediments.

    Directory of Open Access Journals (Sweden)

    Daniel J Mayor

    Full Text Available Copper is essential for healthy cellular functioning, but this heavy metal quickly becomes toxic when supply exceeds demand. Marine sediments receive widespread and increasing levels of copper contamination from antifouling paints owing to the 2008 global ban of organotin-based products. The toxicity of copper will increase in the coming years as seawater pH decreases and temperature increases. We used a factorial mesocosm experiment to investigate how increasing sediment copper concentrations and the presence of a cosmopolitan bioturbating amphipod, Corophium volutator, affected a range of ecosystem functions in a soft sediment microbial community. The effects of copper on benthic nutrient release, bacterial biomass, microbial community structure and the isotopic composition of individual microbial membrane [phospholipid] fatty acids (PLFAs all differed in the presence of C. volutator. Our data consistently demonstrate that copper contamination of global waterways will have pervasive effects on the metabolic functioning of benthic communities that cannot be predicted from copper concentrations alone; impacts will depend upon the resident macrofauna and their capacity for bioturbation. This finding poses a major challenge for those attempting to manage the impacts of copper contamination on ecosystem services, e.g. carbon and nutrient cycling, across different habitats. Our work also highlights the paucity of information on the processes that result in isotopic fractionation in natural marine microbial communities. We conclude that the assimilative capacity of benthic microbes will become progressively impaired as copper concentrations increase. These effects will, to an extent, be mitigated by the presence of bioturbating animals and possibly other processes that increase the influx of oxygenated seawater into the sediments. Our findings support the move towards an ecosystem approach for environmental management.

  13. 塔里木盆地晚泥盆世东河塘组河口湾相遗迹化石%TRACE FOSSILS FROM ESTUARINE FACIES OF DONGHETANG FORMATION (UPPER DEVONIAN), TARIM BASIN

    Institute of Scientific and Technical Information of China (English)

    齐永安; 李凯琦

    2003-01-01

    epifaunal forms; 4)presence of an impoverished marine assemblage of ichnofauna rather than a mixed freshwater/marine assemblage, and diminished size relative to fully marine counterparts; 5)presence of elements of both the Skolithos and Cruziana ichnofacies.Based on the synthetic analysis on bioturbation index and ichnofabric constituent diagram, three ichnofabrics have been recognized from estuarine facies of Donghetang Formation (Upper Devonian) of Tarim Basin,western China, they are: Ophiomorpha ichnofabric, Skolithos ichnofabric and Palaeophycus ichnofabric.Ophiomorpha ichnofabric is characterized by the widely occurrence of Ophiomorpha as well as the absence of other trace fossils. The trace fossil Ophiomorpha ranges from simple, individual burrows to irregular three-dimensional burrow networks consisting of cylindrical tunnels and shafts that typically bifurcate at acute angles. The pelleted wall lining is unclear in the Donghetang Formation because of the strong diagenetic cementation in the burrows. The burrows are very obvious in core because they are commonly high-lighted by contrasting colors of the burrow fill and the surrounding matrix. The burrow fill is much lighter than the matrix and has different texture and fabric. The burrow fill, greyish white in color, consists of secondary ferroan calcite. The matrix, dark brown in color, is constituted by oil-soaked quartz sands. The bioturbation structures formed by Ophiomorpha tracemaker show a different bioturbated degree. They can be divided into 6 grades (bioturbation index), each grade of bioturbation (or BI)is clearly defined in terms of burrow density, amount of burrow overlap and preserved percent of the original sedimentary structures and represents different petrophysical properties. Bed by bed core analysis and statistics of bioturbation indices of Ophiomorpha ichnofabric indicate that the index 2 is common and amounts to 30% of the measured strata, other indices have low percent, absence of bioturbation

  14. Geochemical variability of copper and iron in Oman margin sediments

    Digital Repository Service at National Institute of Oceanography (India)

    Alagarsamy, R.

    in the laboratory. 2.1. Analytical Methods Sediment grain size distribution in each section of cores collected below the OMZ was determined with a Coulter Counter (Model LS 130). Water content in each section of cores collected below the OMZ was determined...-rate estimates suggested that some bioturbation occurring below the mixed-layer depths. Mean Peclet numbers (i.e., [mixed layer depth]x[sedimentation rate]/[D b ]) for the mixed layer were ≤0.4 at five of six stations in the Oman Margin; at 1000 m, a...

  15. Comparison of Biocoenosis with Thanatocoenosis from Adriatic, between the peninsula Istria and the river Po

    Directory of Open Access Journals (Sweden)

    Luka Šribar

    1994-12-01

    Full Text Available The comparison of biocoenosis and thanatocoenosis at three observational stations, west of the peninsula Istria, in littoral of the Adriatic sea, has shown a suprisingly low similarity between them. The difference seems to be due to ecological changes during the deposition of thanatocoenosis (approximately in thelast hundert years. These ecological changes can not be studied in thanatocoenosis because of a very high degree of bioturbation that destroyed stratification and mixed all the skeletal particles. Lateral transport of skeletal particles seems to be of minor importance.

  16. Early diagenesis of recently deposited organic matter: A 9-yr time-series study of a flood deposit

    OpenAIRE

    Tesi, Tommaso; Langone, L.; Goni, Ma; Wheatcroft, Ra; Miserocchi, Stefano; Bertotti, Luciana

    2012-01-01

    stract: In Fall 2000, the Po River (Italy) experienced a 100-yr return period flood that resulted in a 1-25 cm-thick deposit in the adjacent prodelta (10-25 m water depth). In the following years, numerous post-depositional perturbations occurred including bioturbation, reworking by waves with heights exceeding 5 m, as well as periods of extremely high and low sediment supply. Cores collected in the central prodelta after the Fall 2000 flood and over the following 9 yr, allowed characterizati...

  17. The influence of hypercapnia and macrofauna on sediment nutrient flux – will ocean acidification affect nutrient exchange?

    Directory of Open Access Journals (Sweden)

    H. L. Wood

    2009-02-01

    Full Text Available Rising levels of atmospheric carbon dioxide and the concomitant increased uptake of this by the oceans is resulting in hypercapnia-related reduction of ocean pH. Research focussed on the direct effects of these physicochemical changes on marine invertebrates has begun to improve our understanding of impacts at the level of individual physiologies. However, CO2-related impairment of organisms' contribution to ecological or ecosystem processes has barely been addressed. The burrowing ophiuroid Amphiura filiformis, which has a physiology that makes it susceptible to reduced pH, plays a key role in sediment nutrient cycling by mixing and irrigating the sediment, a process known as bioturbation. Here we investigate the role of A. filiformis in modifying nutrient flux rates across the sediment-water boundary and the impact of CO2-related acidification on this process. A 40 day exposure study was conducted under predicted pH scenarios from the years 2100 (pH 7.7 and 2300 (pH 7.3, plus an additional treatment of pH 6.8. This study demonstrated strong relationships between A. filiformis density and cycling of some nutrients; A. filiformis activity increases the sediment uptake of phosphate and the release of nitrite and nitrate. No relationship between A. filiformis density and the flux of ammonium or silicate were observed. Results also indicated that, within the timescale of this experiment, effects at the individual bioturbator level appear not to translate into reduced ecosystem influence. Rather the effect of hypercapnia and lowered pH on bacteria and microphytobenthos may have been of greater significance in understanding the changes to nutrient fluxes seen here. However, long term survival of key bioturbating species is far from assured and changes in both bioturbation and microbial processes could alter key biogeochemical processes in future, more acidic oceans.

  18. Modelling the effects of macrofauna on sediment transport and bed elevation: Application over a cross-shore mudflat profile and model validation

    Science.gov (United States)

    Orvain, Francis; Le Hir, Pierre; Sauriau, Pierre-Guy; Lefebvre, Sébastien

    2012-08-01

    The effects of 2 functional groups of bioturbators have been predicted in terms of long-term impact on erodability: (1) one superficial mobile deposit-feeder, the gastropod Hydrobia ulvae; and (2) one endobenthic deposit-feeder, the bivalve Scrobicularia plana. Different scenarios of morphodynamical cross-shore 1DH/1DV model were performed to simulate the equilibrium profile of an intertidal mudflat under tide and wave forcings. This process-based model for erosion is able to simulate multiphasic sequential resuspension, by discriminating various erosion behaviour like benthos-generated fluff-layer erosion (BGFL) and general bed loosening and burrowing activity in deep layers. The results were analysed and compared to examine the long-term effect of macrofauna after 14 years. It reveals that the impact of the bivalve S. plana is very significant after only 4 years of simulation while the effect of the gastropod H. ulvae is negligible in terms of sediment transport even after 14 years. More generally, this reveals the strong impact of stationary endobenthic bioturbators that induces a high downward shift of the upper shore while the effects of superficial motile bioturbators remain very low. This impact is mainly due to the effect of endobenthic species in deep layers associated to burrowing activities and their consequences on the bed erosion, but the production of a fluff layer by surface grazer like H. ulvae at the sediment surface can be neglected. The importance of macrofauna mediation of bed erodability is discussed in this study by comparing the activities of the two functional groups of bioturbation on the general functioning of intertidal mudflats. The model outcomes (transferred in a 1DV framework) were in close agreement with the measured results of flume data at 3 different bathymetric levels of the mudflat over the cross-shore profile. This validation step revealed that model of sediment transport under influence of biota effects does not need further

  19. Modelling the interactions between radionuclides and particles in the ocean for assessments of sea disposal of radioactive waste

    International Nuclear Information System (INIS)

    This report describes work connected with the combined ocean dispersion and sedimentation model developed by MAFF/NRPB. Firstly, the ability of the model to reproduce the observed profiles of nine naturally occurring tracers was studied. Secondly, a number of sensitivity analyses on the sedimentation component of the model were performed. Thirdly, the effect of variations in bioturbation rate and of the inclusions of turbiditic sedimentation or coastal scavenging were studied. The results are used to draw conclusions on the adequacy of the model. (author)

  20. Sedimentology and ichnology of the fluvial reach to inner estuary of the Ogeechee River estuary, Georgia, USA

    Science.gov (United States)

    Shchepetkina, Alina; Gingras, Murray K.; Pemberton, S. George

    2016-08-01

    Through the integration of sedimentological and ichnological observations, this paper explores the character of sediments deposited across the fluvio-tidal transition zone of the upper microtidal, mixed-energy, sand-dominated Ogeechee River estuary, Georgia, USA. A transect of tidally influenced to fluvial channel-bars and their facies variability is reported. Field and laboratory methods were employed, including observation of physical and biogenic sedimentary structures on the point-bar surfaces and in trenches, collection of grab samples, suction and box coring, grain size and total organic carbon analyses, optical microscopy, core logging, and daylight photography. The data presented in the paper can help in predicting facies changes across the fluvio-tidal transition of sand-dominated fluvio-tidal deposits in the rock record. The lower inner estuary is characterized by medium-fine and fine-medium sand with planar and trough cross-bedding, small-scale ripple lamination, tidal sedimentary structures (flaser and wavy bedding, herringbone cross-stratification), abundant organic debris, and mud rip-up clasts. Bioturbation of the intertidal point bars is low, but cryptobioturbation is locally observed. Upper inner estuary deposits comprise coarse-medium- and medium-coarse-grained sand, and are characterized by faint high-angle planar and trough cross-bedding. Organic debris, mud rip-up clasts, herringbone and current-ripple lamination are rarely observed. Bioturbation is absent to sparse. The fluvio-tidal transition is represented by very-coarse- to coarse-grained sand and granules. Physical sedimentary structures constitute massive, graded planar and trough cross-bedding with abundant plant detritus. Except for rare Siphonichnus- and Lockeia-like traces, bioturbation is absent. The fluvial setting is characterized by coarse-medium sand with unidirectional cross-bedding, current-ripple lamination, and rare organic-rich mud clasts. Bioturbation is absent. Inner

  1. Trace fossils of a cyclic chalk-marl succession; the upper Maastrichtian Rørdal Member, Denmark

    DEFF Research Database (Denmark)

    Lauridsen, Bodil Wesenberg; Surlyk, Finn; Bromley, Richard Granville

    2011-01-01

    -normal sample surfaces vary in area between 29 and 155 cm2. Eight ichnogenera and two undetermined ichnogenera are recognised. The member is characterised by three ichnofabrics (A, B and C). The ichnofabric analysis is based on texture and internal structure of the sediments resulting from bioturbation...... situation between ichnofabrics A and C and occurs in chalk samples immediately adjacent to marl beds. The observed changes in ichnofabrics between chalk and marl are related to the amount of clay in the samples and the differences in the occurrence of trace fossils are interpreted as due to differences...

  2. First observations on marine subaqueous soils in "Torre del Cerrano" marine protected area, Adriatic sea (Italy

    Directory of Open Access Journals (Sweden)

    Stefania Cocco

    2015-12-01

    Full Text Available Subaqueous soils have to be studied with proper methodologies, according to a pedological approach and considering the key role of animal bioturbation. Morphological and chemical characteristics of submerged soils found in the MPA of "Torre del Cerrano", Adriatic sea (Italy, have been studied in this way, and we conclude that submarine soils of the MPA are important examples of pedogenesis promoted by animals. Soils from the highly protected marine area hosted a major biodiversity than those from the sub- and non-protected areas, while no striking differences in terms of soil physical and chemical characteristics among protected, sub-protected and non-protected areas occurred.

  3. Nonbiomineralized carapaces in Cambrian seafloor landscapes (Sirius Passet, Greenland)

    DEFF Research Database (Denmark)

    Mangano, M. Gabriela; Bromley, Richard Granville; Harper, David A.T.;

    2012-01-01

    Widespread microbial mats and the absence of significant bioturbation resulted in a poorly developed mixed layer and extensive cohesive substrates during the Ediacaran-Cambrian transition. Large nonbiomineralized arthropod carapaces overprinted with trails, interconnected burrow systems, narrow...... a significant role. Although some trace fossils (e.g., annulated structures) may be related to scavenging and/or deposit feeding, morphologic evidence suggests that this is not always the case. Interconnected burrow systems provide evidence for re-use of structures, suggesting grazing on or farming of bacteria...

  4. The origin of ferro-manganese oxide coated pumice from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Pearce, N.J.G.; Parthiban, G.; Smith, V.C.; Mudholkar, A.V.; Rao, N.R.

    respectively. 4. Discussion The occurrence of fully Fe-Mn oxide coated pumice with partially coated and fresh/uncoated one at the sediment-water interface could be the result of the so-called “Brazil Nut Effect”, where larger grains are kept... at the sediment–water interface while smaller grains sink because of shaking/tectonic effects (Rosato et al., 1987). In addition to Brazil Nut Effect, bioturbation, benthic organisms and bottom water currents might have helped to keep the older pumice (Fe...

  5. Sediment reworking rates in deep sediments of the Mediterranean Sea

    Energy Technology Data Exchange (ETDEWEB)

    Barsanti, M., E-mail: mattia.barsanti@enea.it [ENEA, Marine Environment Research Centre, La Spezia (Italy); Delbono, I., E-mail: ivana.delbono@enea.it [ENEA, Marine Environment Research Centre, La Spezia (Italy); Schirone, A., E-mail: antonio.schirone@enea.it [ENEA, Marine Environment Research Centre, La Spezia (Italy); Langone, L., E-mail: leonardo.langone@bo.ismar.cnr.it [CNR, ISMAR Istituto di Scienze Marine, U.O.S. Bologna (Italy); Miserocchi, S., E-mail: stefano.miserocchi@bo.ismar.cnr.it [CNR, ISMAR Istituto di Scienze Marine, U.O.S. Bologna (Italy); Salvi, S., E-mail: stefano.salvi@enea.it [ENEA, Research Centre Brasimone, Camugnano (Italy); Delfanti, R., E-mail: roberta.delfanti@enea.it [ENEA, Marine Environment Research Centre, La Spezia (Italy)

    2011-07-01

    Different pelagic areas of the Mediterranean Sea have been investigated in order to quantify physical and biological mixing processes in deep sea sediments. Herein, results of eleven sediment cores sampled at different deep areas (> 2000 m) of the Western and Eastern Mediterranean Sea are presented. {sup 210}Pb{sub xs} and {sup 137}Cs vertical profiles, together with {sup 14}C dating, are used to identify the main processes characterising the different areas and, finally, controlling mixing depths (SML) and bioturbation coefficients (D{sub b}). Radionuclide vertical profiles and inventories indicate that bioturbation processes are the dominant processes responsible for sediment reworking in deep sea environments. Results show significant differences in sediment mixing depths and bioturbation coefficients among areas of the Mediterranean Sea characterised by different trophic regimes. In particular, in the Oran Rise area, where the Almeria-Oran Front induces frequent phytoplankton blooms, we calculate the highest values of sediment mixing layers (13 cm) and bioturbation coefficients (0.187 cm{sup 2} yr{sup -1}), and the highest values of {sup 210}Pb{sub xs} and {sup 137}Cs inventories. Intermediate values of SML and D{sub b} ({approx} 6 cm and {approx} 0.040 cm{sup 2} yr{sup -1}, respectively) characterise the mesothrophic Algero-Balearic basin, while in the Southern Tyrrhenian Sea mixing parameters (SML of 3 cm and D{sub b} of 0.011 cm{sup 2} yr{sup -1}) are similar to those calculated for the oligotrophic Eastern Mediterranean (SML of 2 cm and D{sub b} of {approx} 0.005 cm{sup 2} yr{sup -1}). - Research highlights: {yields} Physical and biological mixing processes in the Mediterranean Sea are investigated. {yields} Results of 11 sediment cores in deep areas of the Mediterranean Sea are shown. {yields} {sup 210}Pb{sub xs} and {sup 137}Cs vertical profiles are analysed. {yields} New data on {sup 210}Pb and {sup 137}Cs inventories of Mediterranean deep sediments are

  6. Physically-based distributed hydrologic modeling of tropical catchments: Hypothesis testing on model formation and runoff generation

    Science.gov (United States)

    Abebe, N. A.; Ogden, F. L.

    2011-12-01

    Watersheds vary in their nature based on their geographic location, altitude, climate, geology, soils, and land use/land cover. These variations lead to differences in the conceptualization and formulation of hydrological models intended to represent the expected hydrological processes in a given catchment. Watersheds in the tropics are characterized by intensive and persistent biological activity and a large amount of rainfall. Our study focuses on the Agua Salud project catchments located in the Panama Canal Watershed, Panama, which have steep rolling topography, deep soils derived from weathered bedrock, and limited exposed bedrock. These catchments are also highly affected by soil cracks, decayed tree roots and animal burrows that form a network of preferential flow paths. One hypothesis is that these macropores conduct interflow during heavy rainfall, when a transient perched water table forms at a depth where the vertical hydraulic conductivity is significantly reduced near the bottom of the bioturbation layer. We have developed a physics-based, spatially distributed, multi-layered hydrologic model to simulate the dominant flow processes, including overland flow, channel flow, vertical matrix and non-Richards film flow, lateral downslope saturated matrix and non-Darcian pipe flow in the bioturbation layer and deep saturated groundwater flow. In our model formulation, we use the model to examine a variety of hydrological processes which we anticipate may occur. Emphasis is given to the modeling of the soil moisture dynamics in the bioturbation layer, development of lateral preferential flow and activation of the macropores and exchange of water at the interface between a bioturbation layer and a second layer below it. We consider interactions between surface water, ground water, channel water and perched water in the riparian zone cells with the aim of understanding likely runoff generation mechanisms. Results show that inclusion of as many different flow

  7. Ichnological record of the Frasnian-Famennian boundary interval: two examples from the Holy Cross Mts (Central Poland)

    Science.gov (United States)

    Stachacz, Michał; Uchman, Alfred; Rodríguez-Tovar, Francisco J.

    2016-03-01

    The Frasnian-Famennian (Late Devonian) boundary interval within the carbonate-siliciclastic series in the Kowala and Płucki sections (Holy Cross Mts, Central Poland) has been analysed to evaluate the influence of the Kellwasser event on the macrobenthic tracemaker community. The Upper Kellwasser event has a lithologically variable record, as horizons of flints (Kowala) and as a bed of bituminous, black, cephalopod limestone (Płucki). Both sections show mostly laminated, unbioturbated beds of marlstones or shales just above the Frasnian-Famennian boundary, which point to events of anoxia on the sea floor. However, the first anoxic horizon occurs below the Frasnian-Famennian boundary. The trace fossils and bioturbational structures are uncommon and poorly diversified. Trichichnus and Multina are the only frequent trace fossils in some beds. Moreover, one horizon above the Frasnian-Famennian boundary contains numerous Multina and a single ?Planolites. Such poorly diversified trace fossil assemblage suggests an unfavourable environment for most of burrowing organisms and fluctuations in oxygenation from anoxic, to dysoxic conditions. The occurrence of the trace fossils and bioturbational structures as spotted and mottled ichnofabrics from the 1.3 m above the Frasnian-Famennian boundary is interpreted as an improvement in bottom water oxygen conditions after the Upper Kellwasser event.

  8. Modelling benthic biophysical drivers of ecosystem structure and biogeochemical response

    Science.gov (United States)

    Stephens, Nicholas; Bruggeman, Jorn; Lessin, Gennadi; Allen, Icarus

    2016-04-01

    The fate of carbon deposited at the sea floor is ultimately decided by biophysical drivers that control the efficiency of remineralisation and timescale of carbon burial in sediments. Specifically, these drivers include bioturbation through ingestion and movement, burrow-flushing and sediment reworking, which enhance vertical particulate transport and solute diffusion. Unfortunately, these processes are rarely satisfactorily resolved in models. To address this, a benthic model that explicitly describes the vertical position of biology (e.g., habitats) and biogeochemical processes is presented that includes biological functionality and biogeochemical response capturing changes in ecosystem structure, benthic-pelagic fluxes and biodiversity on inter-annual timescales. This is demonstrated by the model's ability to reproduce temporal variability in benthic infauna, vertical pore water nutrients and pelagic-benthic solute fluxes compared to in-situ data. A key advance is the replacement of bulk parameterisation of bioturbation by explicit description of the bio-physical processes responsible. This permits direct comparison with observations and determination of key parameters in experiments. Crucially, the model resolves the two-way interaction between sediment biogeochemistry and ecology, allowing exploration of the benthic response to changing environmental conditions, the importance of infaunal functional traits in shaping benthic ecological structure and the feedback the resulting bio-physical processes exert on pore water nutrient profiles. The model is actively being used to understand shelf sea carbon cycling, the response of the benthos to climatic change, food provision and other societal benefits.

  9. Performance assessment methodology as applied to the Greater Confinement Disposal site: Preliminary results of the third performance iteration

    International Nuclear Information System (INIS)

    The US Department of Energy has contracted Sandia National Laboratories to conduct a performance assessment of the Greater Confinement Disposal facility, Nevada. The performance assessment is an iterative process in which transport models are used to prioritize site characterization data collection. Then the data are used to refine the conceptual and performance assessment models. The results of the first two performance assessment iterations indicate that the site is likely to comply with the performance standards under the existing hydrologic conditions. The third performance iteration expands the conceptual model of the existing transport system to include possible future events and incorporates these processes in the performance assessment models. The processes included in the third performance assessment are climate change, bioturbation, plant uptake, erosion, upward advection, human intrusion and subsidence. The work completed to date incorporates the effects of bioturbation, erosion and subsidence in the performance assessment model. Preliminary analyses indicate that the development of relatively deep-rooting plant species at the site, which could occur due to climate change, irrigated farming or subsidence, poses the greatest threat to the site's performance

  10. Field isotopic study of lead fate and compartmentalization in earthworm-soil-metal particle systems for highly polluted soil near Pb recycling factory.

    Science.gov (United States)

    Goix, Sylvaine; Mombo, Stéphane; Schreck, Eva; Pierart, Antoine; Lévêque, Thibaut; Deola, Frédéric; Dumat, Camille

    2015-11-01

    Earthworms are important organisms in soil macrofauna and play a key role in soil functionality, and consequently in terrestrial ecotoxicological risk assessments. Because they are frequently observed in soils strongly polluted by metals, the influence of earthworm bioturbation on Pb fate could therefore be studied through the use of Pb isotopes. Total Pb concentrations and isotopic composition ((206)Pb, (207)Pb and (208)Pb) were then measured in earthworms, casts and bulk soils sampled at different distance from a lead recycling factory. Results showed decreasing Pb concentrations with the distance from the factory whatever the considered matrix (bulk soils, earthworm bodies or cast samples) with higher concentrations in bulk soils than in cast samples. The bivariate plot (208)Pb/(206)Pb ratios versus (206)Pb/(207)Pb ratios showed that all samples can be considered as a linear mixing between metallic process particulate matter (PM) and geochemical Pb background. Calculated anthropogenic fraction of Pb varied between approximately 84% and 100%. Based on Pb isotopic signatures, the comparison between casts, earthworms and bulk soils allowed to conclude that earthworms preferentially ingest the anthropogenic lead fraction associated with coarse soil organic matter. Actually, soil organic matter was better correlated with Pb isotopic ratios than with Pb content in soils. The proposed hypothesis is therefore a decrease of soil organic matter turnover due to Pb pollution with consequences on Pb distribution in soils and earthworm exposure. Finally, Pb isotopes analysis constitutes an efficient tool to study the influence of earthworm bioturbation on Pb cycle in polluted soils. PMID:26025429

  11. Early Triassic wrinkle structures on land: stressed environments and oases for life

    Science.gov (United States)

    Chu, Daoliang; Tong, Jinnan; Song, Haijun; Benton, Michael J.; Bottjer, David J.; Song, Huyue; Tian, Li

    2015-06-01

    Wrinkle structures in rocks younger than the Permian-Triassic (P-Tr) extinction have been reported repeatedly in marine strata, but rarely mentioned in rocks recording land. Here, three newly studied terrestrial P-Tr boundary rock succession in North China have yielded diverse wrinkle structures. All of these wrinkles are preserved in barely bioturbated shore-shallow lacustrine siliciclastic deposits of the Liujiagou Formation. Conversely, both the lacustrine siliciclastic deposits of the underlying Sunjiagou Formation and the overlying Heshanggou Formation show rich bioturbation, but no wrinkle structures or other microbial-related structures. The occurrence of terrestrial wrinkle structures in the studied sections reflects abnormal hydrochemical and physical environments, presumably associated with the extinction of terrestrial organisms. Only very rare trace fossils occurred in the aftermath of the P-Tr extinction, but most of them were preserved together with the microbial mats. This suggests that microbial mats acted as potential oases for the surviving aquatic animals, as a source of food and oxygen. The new finds suggests that extreme environmental stresses were prevalent both in the sea and on land through most of the Early Triassic.

  12. Modelling interactions between soil evolution and diffusive surface processes

    Science.gov (United States)

    Kirkby, Mike; Johnson, Michelle; Gloor, Emanual

    2014-05-01

    Bioturbation, combined with settlement under gravity, generates profiles of bulk density, porosity and hydraulic conductivity (Ksat). Rates of bioturbation are linked to rates of diffusive downslope sediment transport (creep) and rates can be compared via the increase in OSL ages of soil aggregate grains with depth. Some primary porosity is also produced by weathering of rock to saprolite, often with little reduction in bulk density but some dilation of joints. Downward percolation of rain water near the surface is controlled by the diffusion-induced decrease in porosity and Ksat, driving lateral subsurface flow in the zone of fluctuating water table, and leaving progressively less water for downward percolation. As the depth to the weathering front is varied, progressively less water is therefore available for weathering, producing the observed decrease in weathering rate with increasing soil depth. These processes are modelled by repeatedly applying a stochastic realisation of daily rainfalls for an area until the annual hydrological cycle stabilises, providing the average partition of rainfall into its components of evapotranspiration, lateral flow and downward percolation, with depth in the soil. The average hydrology is then applied to drive evolution of the weathering profile over longer time spans.

  13. Temporal Distribution of Diagnostic Biofabrics in the Lower and Middle Ordovician in North China:Clues to the Geobiology of the Great Ordovician Biodiversification Event

    Institute of Scientific and Technical Information of China (English)

    LIU Jianbo; ZHAN Renbin

    2009-01-01

    The temporal distribution of the diagnostic biofabrics In the Lower and Middle Ordovician in North China distinctly illustrates that the sedimentary systems on the paleoplate have been changed markedly as consequences of the Great Ordovician Biodiversification Event (GOBE).The pre-GOBE sedimentary systems deposited in Tremadoc display widespread microbialite and flat-pebble conglomerates,and a less extent of bioturbation.Through the transitional period of early Floian,the sedimentary systems in the rest of the Early and Mid-Ordovician change to GOBE type and are characterized by intensive bioturbation and vanishing flat-pebble conIglomerates and subtidal microbial sediments.The irreversible changes in sedimentary systems in North China are Iinked to the GOBE,which conduced the increase in infaunal tiering,the expansion of infaunal ecospace,and the appearance of new burrowers related to the development of the Paleozoic Evolutionary Fauna during the Ordovician biodiversification.Thus,changes in sedimentary systems during the pivotal period of the GOBE were consequences of a steep diversification of benthic faunas rather than the GOBE's environmental background.

  14. The Hamburg Oceanic Carbon Cycle Circulation Model. Version 1. Version 'HAMOCC2s' for long time integrations

    Energy Technology Data Exchange (ETDEWEB)

    Heinze, C.; Maier-Reimer, E. [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany)

    1999-11-01

    The Hamburg Ocean Carbon Cycle Circulation Model (HAMOCC, configuration HAMOCC2s) predicts the atmospheric carbon dioxide partial pressure (as induced by oceanic processes), production rates of biogenic particulate matter, and geochemical tracer distributions in the water column as well as the bioturbated sediment. Besides the carbon cycle this model version includes also the marine silicon cycle (silicic acid in the water column and the sediment pore waters, biological opal production, opal flux through the water column and opal sediment pore water interaction). The model is based on the grid and geometry of the LSG ocean general circulation model (see the corresponding manual, LSG=Large Scale Geostrophic) and uses a velocity field provided by the LSG-model in 'frozen' state. In contrast to the earlier version of the model (see Report No. 5), the present version includes a multi-layer sediment model of the bioturbated sediment zone, allowing for variable tracer inventories within the complete model system. (orig.)

  15. Sedimentary and petrofacies analyses of the Amasiri Sandstone, southern Benue Trough, Nigeria: Implications for depositional environment and tectonic provenance

    Science.gov (United States)

    Okoro, A. U.; Igwe, E. O.; Nwajide, C. S.

    2016-11-01

    This study was undertaken to determine the depositional environment, provenance and tectonic setting for the Turonian Amasiri Sandstone, southern Benue Trough, Nigeria, using lithofacies analysis and re-appraisal of petrography of the sandstones. Local stratigraphy and field relationships show a thick succession of shales alternating with elongate/parallel sandstone ridges extending eastwards from Akpoha to Amasiri through Itigidi and Ugep to Apiapum areas. Lithofacies analysis reveals 9 lithofacies suggestive of storm (mass flow) and tidal shelf processes. These include dark grey to black laminated shale/silty mudstones, bioturbated mudstones, coquinoid limestones, very fine-grained bioturbated sandstones with shell hash/debris in places and limestone rip-up clasts, massive and chaotic sandy conglomerate with rip - up clasts, fine to medium-grained, parallel laminated sandstone, hummocky cross-stratified, massive, medium to coarse-grained sandstones, medium to very coarse-grained, planar cross-bedded sandstone, with clay-draped foresets and Ophiomorpha burrows, and coarse-grained trough cross-bedded sandstone. Petrofacies analysis identifies the sandstones as feldspathic and arkosic arenites. Ternary plot of framework mineralogy indicates derivation from an uplifted continental block related to the nearby Oban Massif and Cameroon Basement Complex.

  16. Back barrier facies of a microtidal coastline, Upper Cretaceous Blackhawk Formation, Utah

    Energy Technology Data Exchange (ETDEWEB)

    Kamola, D.L.

    1985-01-01

    Protected lagoonal environments situated landward or prograding barriers, are characterized by low energy deposits which include flood tidal deltas, flood-dominated channel-fill sandstones, swamps (coal), and lagoon-fill siltstones. Flood tidal deltas consists of landward-dipping beds of sandstone which interfinger vertically and laterally with rooted and/or bioturbated lagoonal siltstones. Locally, individual beds of the flood tidal delta may be rooted or burrowed, which indicates discontinuous deposition of sediment into a lagoon. Channel-fill sandstones characterized by landward-oriented paleocurrent directions are interpreted to represent tidally influenced channels in a flood-dominated, microtidal setting. The majority of the lagoon-fill sediments are bioturbated, rooted, or burrowed siltstone, with brackish water bivalves Crossostrea, Brachidontes, Corbula and Anomia. Trace fossils Thalassinoides, Planolites, Palaeophycus, and Pelecypodichnus are common. Ophiomorpha-burrowed, medium grain size sandstone with abraded oyster shells is the only evidence of higher energy (storm-related) lagoonal deposition. Swamps are represented by low sulfur, low ash coal seams, with tree stumps, tree roots, and dinosaur tracks. Swamp environments prograded over sediment-filled lagoons, and are interpreted as the final stage of back barrier deposition.

  17. Bottom-up and top-down mechanisms indirectly mediate interactions between benthic biotic ecosystem components

    Science.gov (United States)

    Van Colen, Carl; Thrush, Simon F.; Parkes, Samantha; Harris, Rachel; Woodin, Sally A.; Wethey, David S.; Pilditch, Conrad A.; Hewitt, Judi E.; Lohrer, Andrew M.; Vincx, Magda

    2015-04-01

    The loss or decline in population size of key species can instigate a cascade of effects that have implications for interacting species, therewith impacting biodiversity and ecosystem functioning. We examined how top-down and bottom-up interactions may mediate knock-on effects of a coastal deposit-feeding clam, Macomona liliana (hereafter Macomona), on sandflat meiobenthos densities. Therefore we manipulated densities of Macomona in combination with predator exclusion and experimental shading that was expected to alter microphytobenthos biomass. We show that Macomona regulated densities of meiobenthic (38-500 μm) nematodes, copepods, polychaetes, turbellarians, and ostracodes during the three months of incubation via indirect mechanisms. Predator pressure on Macomona by eagle rays (Myliobatis tenuicaudatus) was found to have a negative effect on densities of some meiobenthic taxa. Furthermore, experimental shading resulted in the loss of a positive relation between Macomona and microphytobenthos biomass, while concurrently increasing the density of some meiobenthic taxa. We suggest that this observation can be explained by the release from bioturbation interference effects of the cockle Austrovenus stutchburyi that was found to thrive in the presence of Macomona under non-shaded conditions. Our results highlight the importance of interactions between macrofaunal bioturbation, microphyte biomass, sediment stability, and predation pressure for the structuring of benthic communities. This experiment illustrates that manipulative field experiments may be particularly suitable to study such multiple indirect mechanisms that regulate ecosystem diversity and related functioning because such approaches may best capture the complex feedbacks and processes that determine ecosystem dynamics.

  18. Biogeomorphically driven salt pan formation in Sarcocornia-dominated salt-marshes

    Science.gov (United States)

    Escapa, Mauricio; Perillo, Gerardo M. E.; Iribarne, Oscar

    2015-01-01

    Salt-marshes are under increasing threat, particularly from sea-level rise and increased wave action associated with climate change. The development and stability of these valuable habitats largely depend on complex interactions between biotic and abiotic processes operating at different scales. Also, interactions between biotic and abiotic processes drive internal morphological change in salt-marshes. In this paper we used a biogeomorphological approach to assess the impact of biological activities and interactions on salt pan formation in Sarcocornia-dominated salt marshes. Salt pans represent a key physiographic feature of salt-marshes and recent studies hypothesized that biogeomorphic processes could be related to salt pan formation in SW Atlantic salt-marshes. The glasswort Sarcocornia perennis is one of the dominant plants in the salt-marshes of the Bahía Blanca Estuary (Argentina) where they form patches up to 8 m in diameter. These salt-marshes are also inhabited in great densities by the burrowing crab Neohelice (Chasmagnathus) granulata whose bioturbation rates are among the highest reported for salt-marshes worldwide. A set of biological interactions between N. granulata and S. perennis appears to be responsible for salt pan development in these areas which has not been described elsewhere. The main objective of this work was to determine the ecological interactions occurring between plants and crabs that lead to salt pan formation by using field-based sampling and manipulative experiments. Our results showed that S. perennis facilitated crab colonization of the salt-marsh by buffering otherwise stressful physical conditions (e.g., temperature, desiccation). Crabs preferred to construct burrows underneath plants and, once they reach high densities (up to 40 burrows m- 2), the sediment reworking caused plant die-off in the central area of patches. At this state, the patches lose elevation and become depressed due to the continuous bioturbation by crabs

  19. Viability of microcomputed tomography to study tropical marine worm galleries in humid muddy sediments

    Energy Technology Data Exchange (ETDEWEB)

    Pennafirme, Simone F., E-mail: sipennafirme@gmail.com [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Inst. de Biologia. Dept. de Biologia Marinha; Machado, Alessandra S.; Lima, Inaya; Suzuki, Katia N.; Lopes, Ricardo T., E-mail: machado@lin.ufrj.br, E-mail: inaya@lin.ufrj.br, E-mail: norisuzuki6@yahoo.com.br, E-mail: ricardo@lin.ufj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), RJ (Brazil). Lab. de Instrumentacao Nuclear

    2013-07-01

    Bioturbation is an ecological process driven by organisms, which transports nutrients and gases from air/water to sediment through their galleries, by the time they feed, burrow and/or construct galleries. This exchange is vital to the maintenance of micro and macrobenthic organisms, mainly in muddy flat environments. Species with distinct galleries could create levels of bioturbation, affecting the benthic interactions. In this sense, it is fundamental developing a non-destructive method that permits identifying/quantifying the properties of these galleries. The recent advances in micro-computed tomography are allowing the high resolution 3D images generation. However, once muddy sediments are rich in organic matter and interstitial water, these would lead to motion artifacts which could, in turn, decrease the accuracy of galleries identification/quantification. In this context, the aim of this study was to develop a protocol which combines laboratory experiments and microtomography analysis in order to generate accurate 3D images of the small marine worm's galleries within humid muddy sediments. The sediment was collected at both muddy flats of Surui's and Itaipu lagoon's mangroves (RJ-Brazil), sieved (0.5mm mesh) and introduced with one individual of the marine worm Laeonereis acuta (Nereididae, Polychaeta) in each acrylic corer holders (4.4cm of internal diameter). High energy microtomography scanner was used to obtain 3D images and the setup calibration was 130 kV and 61 mA. Each acquisition image time was among 4h and 6h. Several procedures of drying remained water inside the cores were performed aiming obtaining images without movement artifacts due to circulating water, and this issue was one of the main studied parameter. In order to investigate possible chemical effects, 2ml of formalin (35%) with menthol were added to the surface of the cores. The results show that although the drying time was appropriated, the chemicals created bubbles

  20. ASPEK PROSES DIAGENESIS TERHADAP SIFAT FISIK BATUPASIR FORMASI KEREK, DAERAH KALIPUTIH DAN SEKITARNYA, KECAMATAN SINGOROJO, KABUPATEN KENDAL, JAWA TENGAH

    Directory of Open Access Journals (Sweden)

    Vanny Hertanto Vahyu

    2012-07-01

    Full Text Available The sedimentary rock is formed and associated with the diagenesis processes, as all the physical, chemical, andbiological changes in the characteristics of a sediment accumulation from the time the grains are deposited untilthey are metamorphosed. This process is profoundly influence the characteristic of sedimentary rock, including thetexture, internal structure, mineral composition, cementation type, and pore space. Hence, it is important to knowor learn the stage of sandstone diagenesis, especially in the Kerek Formation to mark the correlation betweendiagenesis and physical properties of sandstone.The purpose of this research is to identify the stage of diagenetic processes, diagenetic environment, the type ofcementation, and the relationship between diagenetic stage and physical properties of sandstone. The methods usedin this research are survey method and data analysis method. The survey method includes the making of crosssectionalmeasured stratigraphy and data analysis method includes petrographic and scanning electron microscopy(SEM.The sedimentary structures found in the carbonate sandstones are burrows, convolute ripple lamination, gradedbedding, parallel lamination, cross lamination, current ripple lamination; which are features of turbidity deposition(Bouma sequence. Based on the petrography analysis results for sample P 01 and P 02 showed compaction,cementation, dissolution, and bioturbation, with a porosity value of 1 %. Sample P 03 showed compaction,cementation, dissolution, and bioturbation, with a porosity value of 7 %. Sample P 04 showed compaction,cementation, and dissolution, with a porosity value of 1 %. Sample P 06 showed compaction, cementation,dissolution and replacement, with a porosity value of 5 %. Sample P 07 showed compaction, and cementation, witha porosity value of 30 %. The Lithology type in the research area was Calcarenite with dominant shell fragment,the lithology names are Packed biomicrite (Folks, 1959; in

  1. The role of benthic macrofauna on nitrogen cycling in eutrophic lake sediment

    Energy Technology Data Exchange (ETDEWEB)

    Svensson, J.M.

    1998-12-01

    This thesis concerns the role of sediment-living macrobenthos in the cycling of nitrogen species and nitrogen transformation in eutrophic freshwater sediments. In my thesis I have, employing {sup 15}N-isotope techniques in laboratory experiments, shown the importance of infaunal chironomid larvae and oligochaetes on denitrification in eutrophic lake sediments. Investigated benthic organisms not only expand the sediment surface with their permanent or non-permanent burrow constructions, they also transport water through the burrows continuously. This behaviour of intermittent water-pumping activity, provides the burrows with oxygen, and in addition, mediates the supply of nitrate to denitrifying zones. The highly dynamic oxygen climate within and narrow oxic zones around burrows, due to their radial geometry, provides a very short diffusion path for nitrate into surrounding anoxic zones. In my studies rates of denitrification were enhanced c. 3 to 6-fold by the influence of chironomids (Chironomus plumosus) and c. 2-fold by the influence of oligochaetes at comparable biomass. The difference in degree of stimulation is explained by species-specific habitat exploitation which could also be observed between different tube-dwelling species of chironomids. Besides chironomid biomass, the degree of enhancement of denitrification by chironomids was dependent on nitrate concentration in the overlying water, and water temperature. Nitrification was also seen to be stimulated by the infaunal macrobenthos but to a lesser degree than denitrification. It is suggested that bioturbated eutrophic sediment, under predominantly oxic bottom water conditions may act more pronouncedly as a sink for inorganic nitrogen relative to non-bioturbated sediment, and that bioturbated sediment above all, may be an important factor contributing to lowered transport of nitrogen to the coast. In order to sustain high nitrogen removal capacity in wetlands, ponds and lakes, it is further suggested

  2. Viability of microcomputed tomography to study tropical marine worm galleries in humid muddy sediments

    International Nuclear Information System (INIS)

    Bioturbation is an ecological process driven by organisms, which transports nutrients and gases from air/water to sediment through their galleries, by the time they feed, burrow and/or construct galleries. This exchange is vital to the maintenance of micro and macrobenthic organisms, mainly in muddy flat environments. Species with distinct galleries could create levels of bioturbation, affecting the benthic interactions. In this sense, it is fundamental developing a non-destructive method that permits identifying/quantifying the properties of these galleries. The recent advances in micro-computed tomography are allowing the high resolution 3D images generation. However, once muddy sediments are rich in organic matter and interstitial water, these would lead to motion artifacts which could, in turn, decrease the accuracy of galleries identification/quantification. In this context, the aim of this study was to develop a protocol which combines laboratory experiments and microtomography analysis in order to generate accurate 3D images of the small marine worm's galleries within humid muddy sediments. The sediment was collected at both muddy flats of Surui's and Itaipu lagoon's mangroves (RJ-Brazil), sieved (0.5mm mesh) and introduced with one individual of the marine worm Laeonereis acuta (Nereididae, Polychaeta) in each acrylic corer holders (4.4cm of internal diameter). High energy microtomography scanner was used to obtain 3D images and the setup calibration was 130 kV and 61 mA. Each acquisition image time was among 4h and 6h. Several procedures of drying remained water inside the cores were performed aiming obtaining images without movement artifacts due to circulating water, and this issue was one of the main studied parameter. In order to investigate possible chemical effects, 2ml of formalin (35%) with menthol were added to the surface of the cores. The results show that although the drying time was appropriated, the chemicals created bubbles within the

  3. Modeling the vertical soil organic matter profile using 210Pbex measurements and Bayesian inversion

    Directory of Open Access Journals (Sweden)

    B. Kruijt

    2011-07-01

    Full Text Available In view of its potential significance for soil organic matter (SOM cycling, the vertical SOM distribution in the profile should be considered in models. To mechanistically predict the SOM profile, three additional processes should be represented compared to bulk SOM models: (vertically distributed rhizodeposition, mixing due to bioturbation, and movement with the liquid phase as dissolved organic matter. However, the convolution of these processes complicates parameter estimation based on the vertical SOM distribution alone. Measurements of the atmospherically produced isotope 210Pbex may provide the additional information needed to constrain the processes. Since 210Pbex enters the soil at the surface and bind strongly to organic matter it is an effective tracer for SOM transport. In order to study the importance of root input, bioturbation, and liquid phase transport for SOM profile formation we performed Bayesian parameter estimation of the previously developed mechanistic SOM profile model SOMPROF. 13 parameters, related to decomposition and transport of organic matter, were estimated for the soils of two temperate forests with strongly contrasting SOM profiles: Loobos (the Netherlands and Hainich (Germany. Measurements of organic carbon stocks and concentrations, decomposition rates, and 210Pbex profiles were used in the optimization. For both sites, 3 optimizations were performed in which stepwise 210Pbex data and prior knowledge were added. The optimizations yielded posterior distributions with several cases (modes which were characterized by the dominant organic matter (OM pool: non-leachable slow OM, leachable slow OM, or root litter. For Loobos, the addition of 210Pbex data to the optimization clearly indicated which case was most likely. For Hainich, there is more uncertainty, but the most likely case produced by the optimization agrees well with other measurements. For both sites the most likely case of the final optimization was one

  4. Environmental Fate of Synthetic Drilling fluids from Offshore Drilling Operations - An Experimental Study of an Olefin-, Ether- and Ester-Based Mud System on Cuttings Deposited in Benthic Chambers

    Energy Technology Data Exchange (ETDEWEB)

    Schaanning, M.T.

    1996-03-01

    In offshore drilling operations, much of the mineral oil previously used in mud systems has been replaced by synthetic drilling fluid. The chemicals enter the North Sea environment attached to bore hole cuttings deposited on the seabed near the discharge sites. After deposition, erosion may occur by biodegradation, bioturbation, resuspension and release to the water mass of dissolved chemicals or metabolites. In the investigation described in this report aliquots of control sediment and three types of cuttings were deposited in duplicate benthic chambers. During an experimental period of 161 days, the loss of drilling fluids from the sediments as well as the change of the ratio between drilling fluid and barium was measured. The mineralization of drilling carbon fluid to CO{sub 2} and water was calculated from oxygen consumption measurements and effects on sediment pH and redox potentials were determined at various time intervals. 10 refs., 13 figs., 25 tabs.

  5. Consequences of a simulated rapid ocean acidification event for benthic ecosystem processes and functions.

    Science.gov (United States)

    Murray, Fiona; Widdicombe, Stephen; McNeill, C Louise; Solan, Martin

    2013-08-30

    Whilst the biological consequences of long-term, gradual changes in acidity associated with the oceanic uptake of atmospheric carbon dioxide (CO2) are increasingly studied, the potential effects of rapid acidification associated with a failure of sub-seabed carbon storage infrastructure have received less attention. This study investigates the effects of severe short-term (8days) exposure to acidified seawater on infaunal mediation of ecosystem processes (bioirrigation and sediment particle redistribution) and functioning (nutrient concentrations). Following acidification, individuals of Amphiura filiformis exhibited emergent behaviour typical of a stress response, which resulted in altered bioturbation, but limited changes in nutrient cycling. Under acidified conditions, A. filiformis moved to shallower depths within the sediment and the variability in occupancy depth reduced considerably. This study indicated that rapid acidification events may not be lethal to benthic invertebrates, but may result in behavioural changes that could have longer-term implications for species survival, ecosystem structure and functioning.

  6. Implications of excess 210Pb and 137Cs in sediment cores from Mikawa Bay, Japan

    Institute of Scientific and Technical Information of China (English)

    LU Xueqiang; MATSUMOTO Eiji

    2009-01-01

    Four sediment cores were collected from Mikawa Bay, Japan, and excess 210Pb and 137Cs were measured by gamma spectrometry. Sedimentation rates for the four cores were determined by 210Pb method. The sedimentation rate range is 0.10--0.70 g/(cm2·year). The bio-mixing depth for each core is less than 7.0 cm, and was determined by the excess 210Pb profiles as well. Therefore, the bioturbation is slight. The 210Pb-derived dates coincide with the results from 137Cs geochronology. Acceleration in sedimentation rate due to environmental alteration has been found in cores A2.5 and 05AS8, representing two depocenters due to their topography. Evidence of the Tokai Flood in 2000 was found in core 05AS8 according to the profiles of both radioisotopes and trace metals.

  7. Carbon mineralization and oxygen dynamics in sediments with deep oxygen penetration, Lake Superior

    DEFF Research Database (Denmark)

    Li, Jiying; Crowe, Sean Andrew; Miklesh, David;

    2012-01-01

    To understand carbon and oxygen dynamics in sediments with deep oxygen penetration, we investigated eight locations (160–318-m depth) throughout Lake Superior. Despite the 2–4 weight percent organic carbon content, oxygen penetrated into the sediment by 3.5 to > 12 cm at all locations. Such deep......, suggesting that temporal variability in deeply oxygenated sediments may be greater than previously acknowledged. The oxygen uptake rates (4.4–7.7 mmol m−2 d−1, average 6.1 mmol m−2 d−1) and carbon mineralization efficiency (∼ 90% of deposited carbon) were similar to those in marine hemipelagic and pelagic...... penetration is explained by low sedimentation rates (0.01–0.04 cm yr−1), high solubility of oxygen in freshwater, and a shallow (∼ 2 cm) bioturbation zone. In response mainly to oxygen variations in the bottom waters, the sediment oxygen penetration varied seasonally by as much as several centimeters...

  8. Denudation rates determined from the accumulation of in situ-produced 10Be in the luquillo experimental forest, Puerto Rico

    Science.gov (United States)

    Brown, Erik Thorson; Stallard, Robert F.; Larsen, Matthew C.; Raisbeck, Grant M.; Yiou, Francoise

    1995-01-01

    We present a simple method for estimation of long-term mean denudation rates using in situ-produced cosmogenic 10Be in fluvial sediments. Procedures are discussed to account for the effects of soil bioturbation, mass wasting and attenuation of cosmic rays by biomass and by local topography. Our analyses of 10Be in quartz from bedrock outcrops, soils, mass-wasting sites and riverine sediment from the Icacos River basin in the Luquillo Experimental Forest, Puerto Rico, are used to characterize denudation for major landform elements in that basin. The 10Be concentration of a discharge-weighted average of size classes of river sediment corresponds to a long-term average denudation of ≈ 43 m Ma −1, consistent with mass balance results. 

  9. GEOMORPHOLOGY. Experimental evidence for hillslope control of landscape scale.

    Science.gov (United States)

    Sweeney, K E; Roering, J J; Ellis, C

    2015-07-01

    Landscape evolution theory suggests that climate sets the scale of landscape dissection by modulating the competition between diffusive processes that sculpt convex hillslopes and advective processes that carve concave valleys. However, the link between the relative dominance of hillslope and valley transport processes and landscape scale is difficult to demonstrate in natural landscapes due to the episodic nature of erosion. Here, we report results from laboratory experiments combining diffusive and advective processes in an eroding landscape. We demonstrate that rainsplash-driven disturbances in our experiments are a robust proxy for hillslope transport, such that increasing hillslope transport efficiency decreases drainage density. Our experimental results demonstrate how the coupling of climate-driven hillslope- and valley-forming processes, such as bioturbation and runoff, dictates the scale of eroding landscapes. PMID:26138970

  10. A comparison of two nitrification inhibitors used to measure nitrification rates in estuarine sediments

    Science.gov (United States)

    Caffrey, J.M.; Miller, L.G.

    1995-01-01

    Nitrification rates were measured using intact sediment cores from South San Francisco Bay and two different nitrification inhibitors: acetylene and methyl fluoride. Sediment oxygen consumption and ammonium and nitrate fluxes were also measured in these cores. Four experiments were conducted in the spring, and one in the fall of 1993. There was no significant difference in nitrification rates measured using the two inhibitors, which suggests that methyl fluoride can be used as an effective inhibitor of nitrification. Nitrification was positively correlated with sediment oxygen consumption and numbers of macrofauna. This suggests that bioturbation by macrofauna is an important control of nitrification rates. Irrigation by the tube-dwelling polychaete, Asychis elongata, which dominates the benthic biomass at this location, appears particularly important. Ammonium fluxes out of the sediment were greatest about one week after the spring bloom, while nitrification peaked about one month later.

  11. TransparC

    DEFF Research Database (Denmark)

    Callesen, Ingeborg; Vesterdal, Lars; Magnussen, Andreas;

    soil horizons and the fraction of the organic horizon that is translocated to spodic material in a B-horizon is to be chosen from a range of values. Four cases were selected in that reflect common forested soil types in Denmark. In the four selected cases turnover rates (k, year-1) were adjusted......, and iterated turnover rates in horizontal fixed depth soil sections to 1 meter depth. The intended use is mainly for outlier detection in resampling studies and teaching soil C dynamics. The simulation utilized repeated measurements of soil C (SINKS 2007-12) and will be validated with new data collected during......, bioturbation by macrofauna (earthworms) and podzolisation were included, allowing transfer of SOC between the forest floor and mineral soil layers. The forest soil carbon simulator incorporates all types of new and old organic matter into one pool. It is organized in six horizontal soil layers and runs for 40...

  12. Distributions of Pu, Am and Cs in margin sediments from the western Mediterranean (Spanish coast)

    International Nuclear Information System (INIS)

    Continental margins are important areas to be considered when studying the distributions and depositions of pollutants, both conventional and radioactive. Coastal sediments accumulate most of those contaminants which can be introduced following atmospheric and/or fluvial pathways. Moreover, their residence times within the water column are usually shortened due to their affinity to associate with the downward falling particulate matter, more abundant at shallower depths. In this paper, the distribution profiles and inventories of plutonium, americium and cesium are detailed, providing useful information about recent sedimentation phenomena such as sediment mixing, slumping processes and bioturbation. Unsupported 210Pb data are used as reliable indicators of enhanced/reduced deposition events. Also, the calculated inventories have enabled the estimation of the radiological contribution of the Spanish Mediterranean margin to the total radioactivity deposited onto the Mediterranean sea floor

  13. Periodic anoxic shelf in the Early-Middle Ordovician transition: ichnosedimentologic evidence from west-central Utah, USA

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ichnosedimentologic evidence of periodic anoxic shelf in the Early-Middle Ordovician transition includes lower ichnodiversity, shallower bioturbation and burrowing depth (<4 cm ), rare domichnia, tiny Chondrites occupying shallower or shallowest tiering, widely distributed nodules of limonite pseudomorphs after pyrite, occurrence of trace fossils being closely associated with the storm event layers, and stratigraphic successions with orbital cyclostratigraphic architecture. It is suggested that lower atmospheric oxygen level during the Early Paleozoic, the Ordovician radiation, dramatic transgression and warmer temperatures would result in the periodic anoxia in the Early-Middle Ordovician transition. This episode began at the later Early Ordovician and lasted about 3.4 Ma on the basis of orbital cyclostratigraphy.

  14. Mussel farming as a nutrient reduction measure in the Baltic Sea: consideration of nutrient biogeochemical cycles.

    Science.gov (United States)

    Stadmark, J; Conley, D J

    2011-07-01

    Nutrient loads from the land to the sea must be reduced to combat coastal eutrophication. It has been suggested that further mitigation efforts are needed in the brackish Baltic Sea to decrease nutrients, especially in eutrophic coastal areas. Mussel farming is a potential measure to remove nutrients directly from the sea. Mussels consume phytoplankton containing nitrogen (N) and phosphorus (P); when the mussels are harvested these nutrients are removed from the aquatic system. However, sedimentation of organic material in faeces and pseudo-faeces below a mussel farm consumes oxygen and can lead to hypoxic or even anoxic sediments causing an increased sediment release of ammonium and phosphate. Moreover, N losses from denitrification can be reduced due to low oxygen and reduced numbers of bioturbating organisms. To reveal if mussel farming is a cost-effective mitigation measure in the Baltic Sea the potential for enhanced sediment nutrient release must be assessed.

  15. The stratigraphy of cretaceous mudstones in the eastern Fuegian Andes: new data from body and trace fossils Estratigrafía de las fangolitas del Cretácico en los Andes Fueguinos orientales: Nuevos datos de cuerpos y trazas fósiles

    Directory of Open Access Journals (Sweden)

    Eduardo B. Olivero

    2009-04-01

    Full Text Available The stratigraphy of Cretaceous marine mudstones in the Fuegian Andes, roughly equivalent to Charles Darwin's clay-slate formation, remains a still unsolved problem. Previous records of Albian, Turonian-Coniacian, and Santonian-Campanian bivalves are combined with new findings of the Late Albian inoceramid Inoceramus anglicus Woods, and the Maastrichtian ammonites Diplomoceras sp., Anagaudryceras sp., Maorites densicostatus (Kilian and Reboul, Maorites sp., and Pachydiscus (Neodesmoceras sp. to further constrain the Cretaceous stratigraphy of the eastern Fuegian Andes. In addition, new records of distinctive trace fossils and ichnofabric are meaningful for stratigraphic division and delineation of paleoenvironmental settings in these Cretaceous mudstones. The Lower Cretaceous ichnoassemblage of Chondrites targioni (Brongniart and Zoophycos isp. is consistent with the inferred slope-volcaniclastic apron settings of the Yahgan Formation; Nereites missouriensis (Weller reflects distal basin plain depositional settings for the Beauvoir Formation. In the Upper Cretaceous, the "Estratos de Buen Suceso" record the earliest extensively bioturbated horizons, reflecting prolonged well-oxygenated bottom conditions. In the Bahía Thetis Formation, organic-rich, channel margin or distal basin slaty mudstones record the last occurrence of inoceramid bivalves in the Austral Basin; the generalized absence of trace fossils is consistent with dysoxic bottom conditions. The thoroughly bioturbated Policarpo Formation, records a marked change in paleoceanographic conditions. The strong contrast in the intensity of bioturbation between the Upper Campanian-Maastrichtian Bahía Thetis Formation, almost devoid of trace fossils, and the highly bioturbated Maastrichtian-Danian Policarpo Formation reflects a change from dysoxic-anoxic to well ventilated conditions, probably associated with a cooling trend of bottom waters in the austral deep oceans.En los Andes Fueguinos la

  16. New Ediacara fossils preserved in marine limestone and their ecological implications

    Science.gov (United States)

    Chen, Zhe; Zhou, Chuanming; Xiao, Shuhai; Wang, Wei; Guan, Chengguo; Hua, Hong; Yuan, Xunlai

    2014-02-01

    Ediacara fossils are central to our understanding of animal evolution on the eve of the Cambrian explosion, because some of them likely represent stem-group marine animals. However, some of the iconic Ediacara fossils have also been interpreted as terrestrial lichens or microbial colonies. Our ability to test these hypotheses is limited by a taphonomic bias that most Ediacara fossils are preserved in sandstones and siltstones. Here we report several iconic Ediacara fossils and an annulated tubular fossil (reconstructed as an erect epibenthic organism with uniserial arranged modular units), from marine limestone of the 551-541 Ma Dengying Formation in South China. These fossils significantly expand the ecological ranges of several key Ediacara taxa and support that they are marine organisms rather than terrestrial lichens or microbial colonies. Their close association with abundant bilaterian burrows also indicates that they could tolerate and may have survived moderate levels of bioturbation.

  17. Conditional Responses of Benthic Communities to Interference from an Intertidal Bivalve.

    Directory of Open Access Journals (Sweden)

    Carl Van Colen

    Full Text Available Habitat-modifying organisms that impact other organisms and local functioning are important in determining ecosystem resilience. However, it is often unclear how the outcome of interactions performed by key species varies depending on the spatial and temporal disturbance context which makes the prediction of disturbance-driven regime shifts difficult. We investigated the strength and generality of effects of the filter feeding cockle Cerastoderma edule on its ambient intertidal benthic physical and biological environment. By comparing the magnitude of the effect of experimental cockle removal between a non-cohesive and a sheltered cohesive sediment in two different periods of the year, we show that the outcome of cockle interference effects relates to differences in physical disturbance, and to temporal changes in suspended sediment load and ontogenetic changes in organism traits. Interference effects were only present in the cohesive sediments, though the effects varied seasonally. Cockle presence decreased only the density of surface-dwelling species suggesting that interference effects were particularly mediated by bioturbation of the surface sediments. Furthermore, density reductions in the presence of cockles were most pronounced during the season when larvae and juveniles were present, suggesting that these life history stages are most vulnerable to interference competition. We further illustrate that cockles may enhance benthic microalgal biomass, most likely through the reduction of surface-dwelling grazing species, especially in periods with high sediment load and supposedly also high bioturbation rates. Our results emphasize that the physical disturbance of the sediment may obliterate biotic interactions, and that temporal changes in environmental stressors, such as suspended sediments, may affect the outcome of key species interference effects at the local scale. Consequently, natural processes and anthropogenic activities that change

  18. Kinetic quantification of vertical solid matter transfers in soils by a multi-isotopic approach

    International Nuclear Information System (INIS)

    Clay translocation is one of the major soil forming processes, however it is poorly quantified and modeled. We propose to quantify it together with bioturbation by combining different isotopic systems (137Cs, 210Pb (xs), meteoric 10Be, 206/207Pb, δ13C, 14C) with numerical modeling based on a nonlinear diffusion-convection equation with depth dependent parameters. This novel method has been applied on Luvisol anthropo-sequences developed on loess, differing by their land use (cropping versus grassland or forest) and their agricultural practices (reduced tillage, no tillage and manure input). Our results show that as much as 91 ± 9 % and 80 ± 9 % of 137Cs and 10Be, respectively, are associated to the clay size fraction (0-2 μm) and can thus effectively trace vertical solid matter transfers in soils with pH > 5 and low organic carbon. Lead partitioning between different solid phases is more complex. Considering two spatial distributions of isotopes (macro-pores or soil matrix), we built up a multi-isotopic modelling approach that simulates the experimental data with the common set of transfer parameters and allowed us to quantify the relative contributions of vertical solid matter transfers to present-day 0-2 μm vertical distributions. Clay translocation is responsible for 9 to 66 % of the clay accumulations in the Bt-horizon. The diffusion coefficient also quantifies the rate of soil mixing by bioturbation. Modeling of the kinetics of solid matter transfer at multiple spatio-temporal scales should become a method of predilection in modern pedogenic and critical zone studies. (author)

  19. 210Pb balance and implications for particle transport on the continental shelf, U.S. Middle Atlantic Bight

    Science.gov (United States)

    Bacon, M.P.; Belastock, Rebecca A.; Bothner, Michael H.

    1994-01-01

    Supply of 210Pb to the continental shelf off the northeastern United States is dominated by the deposition from the atmosphere, the rate of which is reliably known from previously published work. Excess 210Pb inventories in the shelf sediments show accumulations that are nearly in balance with the supply, even in areas of relict sands where it is believed that no net accumulation of sediment presently occurs. The 210Pb distributions in shelf and slope water indicate that the two-way fluid exchange at the shelf-slope front and the net transport in the alongshore flow make comparatively small contributions to the shelf 210Pb budget. The near balance between supply and decay of 210Pb on the shelf implies a limit to the particle export flux. It is concluded that the export of particulate organic carbon does not exceed 60 g m−2 y−1 (∼25% of primary production) and is probably lower. The hypothesis is advanced that fine particulate matter introduced to the continental shelf is detained in its transit of the shelf because of bioturbational trapping in the sediment due to benthic animals. Distributions of 210Pb in suspended particulate matter and in the fine fraction of shelf sediments suggest that the average fine particle must undergo several cycles of deposition-bioturbation-resuspension-redeposition and requires a number of decades for its transit and ultimate export from the shelf. Thus, only the most refractory organic matter is likely to be exported.

  20. Small ecosystem engineers as important regulators of lake's sediment respiration.

    Science.gov (United States)

    Baranov, Victor; Lewandowski, Joerg; Krause, Stefan; Romeijn, Paul

    2016-04-01

    Although shallow lakes are covering only about 1.5% of the land surface of the Earth, they are responsible for sequestration of carbon amounts similar or even larger than those sequestered in all marine sediments. One of the most important drivers of the carbon sequestration in lakes is sediment respiration. Especially in shallow lakes, bioturbation, i.e. the biogenic reworking of the sediment matrix and the transport of fluids within the sediment, severely impacts on sediment respiration. Widespread freshwater bioturbators such as chironomid larvae (Diptera, Chironomidae) are building tubes in the sediment and actively pump water through their burrows (ventilation). In the present work we study how different organism densities and temperatures (5-30°C) impact on respiration rates. In a microcosm experiment the bioreactive resazurin/resorufin smart tracer system was applied for quantifying the impacts of different densities of Chironomidae (Diptera) larvae (0, 1000, 2000 larvae/m2) on sediment respiration. Tracer transformation rates (and sediment respiration) were correlated with larval densities with highest transformation rates occurring in microcosms with highest larval densities. Respiration differences between defaunated sediment and sediment with 1000 and 2000 larvae per m2 was insignificant at 5 °C, and was progressively increasing with rising temperatures. At 30 °C respiration rates of sediment with 2000 larvae per m2 was 4.8 times higher than those of defaunated sediment. We interpret this as an effect of temperature on larval metabolic and locomotory activity. Furthermore, bacterial communities are benefiting from the combination of the high water temperatures and bioirrigation as bacterial community are able to maintain high metabolic rates due to oxygen supplied by bioirrigation. In the context of global climate change that means that chironomid ecosystem engineering activity will have a profound and increasing impact on lake sediment respiration

  1. Base of brackish-water mud as key regional stratigraphic marker of mid-Holocene marine flooding of the Baltic Sea Basin

    Science.gov (United States)

    Virtasalo, Joonas J.; Endler, Michael; Moros, Matthias; Jokinen, Sami A.; Hämäläinen, Jyrki; Kotilainen, Aarno T.

    2016-08-01

    Many modern epicontinental seas were dry land before their marine flooding by the mid-Holocene glacioeustatic sea-level rise, whereas the Baltic Sea Basin was covered by a huge postglacial lake. This change from a postglacial lake to the present-day semi-enclosed brackish-water sea is studied here in sediment cores and acoustic profiles from the Baltic Sea major sub-basins, based on novel datasets combined with information extracted from earlier publications. In shallow areas (water depth), the base of the brackish-water mud is erosional and covered by a patchy, thin, transgressive silt-sand sheet resulting from decreased sediment supply, winnowing and the redistribution of material from local coarse-grained deposits during transgression. This erosional marine flooding surface becomes sharp and possibly erosional in deep areas (>50m water depth), where it may be locally less clearly expressed due to reworking and bioturbation. Both in the shallow and deep areas, the brackish-water mud is strongly enriched in organic matter compared to underlying sediments. Bioturbation type changes at the flooding surface in response to the increased sedimentary organic content, but no firm-ground ichnofacies were developed because of low erosion. It is concluded that the base of the brackish-water mud is a robust allostratigraphic bounding surface that is identifiable by the lithologic examination of cores over the Baltic Sea. The surface is a distinct reflector in seismic-acoustic profiles, which facilitates mapping and basin-wide stratigraphic subdivision. Detailed geochronologic studies are required to confirm if sediments immediately overlying the erosional flooding surface in shallow areas are younger than the basal part of the brackish-water mud in deep areas that is predicted to be time-equivalent to the erosion.

  2. Investigation into the Origin and Character of Surficial Sedimentary Deposits at the Midshore Regional Solid Waste Facility near Easton, Maryland

    Science.gov (United States)

    Smoot, Joseph P.; Newell, Wayne L.; DeJong, Benjamin D.

    2009-01-01

    A temporary exposure at the Midshore Regional Solid Waste Facility near Easton, MD, provided an opportunity to document the characteristics of the complex assemblage of surficial facies in that area. This unusually large cross section allowed interpretation of the changing processes that shaped the landscape in response to climate change through the late Pleistocene. Eight stratigraphic units were recognized: (1) gray, fossiliferous, muddy silt of the marine Miocene Choptank Formation; (2) coarse, crossbedded conglomerate of the late Miocene to Pliocene fluvial Pensauken Formation; (3) bioturbated muddy conglomerate interpreted as deposits of small colluvial fans; (4) pebbly, quartzose sand overlying a planar erosional surface reflecting a marine transgression; (5) irregular pods and lenses of sand and gravel deformed into bowl-shaped folds and faulted, which are interpreted as wind deposits over a semipermanent snow cover (niveo-aeolian deposits); (6) crossbedded sand and conglomerate with abundant mud partings indicating tidal influences on sinuous stream channels; (7) heavily bioturbated silt and sand with abundant root casts and flattened vesicles interpreted as aeolian loess deposits in marshy fens; and (8) pebbly sand and mud with scattered boulders and cobbles that reflect modern infill of the excavation by the operators. Soils formed on units 3, 4, and 7. Superimposed on units 4, 5, and 7 is evidence of deep freezing and permafrost development and subsequent thermokarst development after thawing, which includes large, complexly filled wedge-shaped cracks, deformed bedding and faults, fluid-injection structures, and spherical blobs of sand and mud. Each of the stratigraphic units has irregular distributions and lateral changes. The results of this study provide a unique insight into the geometry of surficial deposits that will help facilitate mapping of units, interpretation of cored intervals, and understanding of ground-penetrating radar profiles. The

  3. A physically-based Distributed Hydrologic Model for Tropical Catchments

    Science.gov (United States)

    Abebe, N. A.; Ogden, F. L.

    2010-12-01

    Hydrological models are mathematical formulations intended to represent observed hydrological processes in a watershed. Simulated watersheds in turn vary in their nature based on their geographic location, altitude, climatic variables and geology and soil formation. Due to these variations, available hydrologic models vary in process formulation, spatial and temporal resolution and data demand. Many tropical watersheds are characterized by extensive and persistent biological activity and a large amount of rain. The Agua Salud catchments located within the Panama Canal Watershed, Panama, are such catchments identified by steep rolling topography, deep soils derived from weathered bedrock, and limited exposed bedrock. Tropical soils are highly affected by soil cracks, decayed tree roots and earthworm burrows forming a network of preferential flow paths that drain to a perched water table, which forms at a depth where the vertical hydraulic conductivity is significantly reduced near the bottom of the bioturbation layer. We have developed a physics-based, spatially distributed, multi-layered hydrologic model to simulate the dominant processes in these tropical watersheds. The model incorporates the major flow processes including overland flow, channel flow, matrix and non-Richards film flow infiltration, lateral downslope saturated matrix and non-Darcian pipe flow in the bioturbation layer, and deep saturated groundwater flow. Emphasis is given to the modeling of subsurface unsaturated zone soil moisture dynamics and the saturated preferential lateral flow from the network of macrospores. Preliminary results indicate that the model has the capability to simulate the complex hydrological processes in the catchment and will be a useful tool in the ongoing comprehensive ecohydrological studies in tropical catchments, and help improve our understanding of the hydrological effects of deforestation and aforestation.

  4. A large-scale field trial of thin-layer capping of PCDD/F-contaminated sediments: Sediment-to-water fluxes up to 5 years post-amendment.

    Science.gov (United States)

    Cornelissen, Gerard; Schaanning, Morten; Gunnarsson, Jonas S; Eek, Espen

    2016-04-01

    The longer-term effect (3-5 y) of thin-layer capping on in situ sediment-to-surface water fluxes was monitored in a large-scale field experiment in the polychlorinated dibenzodioxin and dibenzofuran (PCDD/F) contaminated Grenlandfjords, Norway (4 trial plots of 10,000 to 40,000 m(2) at 30 to 100 m water depth). Active caps (designed thickness 2.5 cm) were established in 2 fjords, consisting of dredged clean clay amended with powdered activated carbon (PAC) from anthracite. These active caps were compared to 2 nonactive caps in one of the fjords (designed thickness 5 cm) consisting of either clay only (i.e., without PAC) or crushed limestone. Sediment-to-water PCDD/F fluxes were measured in situ using diffusion chambers. An earlier study showed that during the first 2 years after thin-layer capping, flux reductions relative to noncapped reference fields were more extensive at the fields capped with nonactive caps (70%-90%) than at the ones with PAC-containing caps (50%-60%). However, the present work shows that between 3 and 5 years after thin-layer capping, this trend was reversed and cap effectiveness in reducing fluxes was increasing to 80% to 90% for the PAC caps, whereas cap effectiveness of the nonactive caps decreased to 20% to 60%. The increasing effectiveness over time of PAC-containing "active" caps is explained by a combination of slow sediment-to-PAC mass transfer of PCDD/Fs and bioturbation by benthic organisms. The decreasing effectiveness of "nonactive" limestone and clay caps is explained by deposition of contaminated particles on top of the caps. The present field data indicate that the capping efficiency of thin active caps (i.e., enriched with PAC) can improve over time as a result of slow diffusive PCDD/F transfer from sediment to PAC particles and better mixing of the PAC by bioturbation. PMID:26012529

  5. Paleoecology of the Devonian-Mississippian black-shale sequence in eastern Kentucky with an atlas of some common fossils

    Energy Technology Data Exchange (ETDEWEB)

    Barron, L.S.; Ettensohn, F.R.

    1981-04-01

    The Devonian-Mississippian black-shale sequence of eastern North America is a distinctive stratigraphic interval generally characterized by low clastic influx, high organic production in the water column, anaerobic bottom conditions, and the relative absence of fossil evidence for biologic activity. The laminated black shales which constitute most of the black-shale sequence are broken by two major sequences of interbedded greenish-gray, clayey shales which contain bioturbation and pyritized micromorph invertebrates. The black shales contain abundant evidence of life from upper parts of the water column such as fish fossils, conodonts, algae and other phytoplankton; however, there is a lack of evidence of benthic life. The rare brachiopods, crinoids, and molluscs that occur in the black shales were probably epiplanktic. A significant physical distinction between the environment in which the black sediments were deposited and that in which the greenish-gray sediments were deposited was the level of dissolved oxygen. The laminated black shales point to anaerobic conditions and the bioturbated greenish-gray shales suggest dysaerobic to marginally aerobic-dysaerobic conditions. A paleoenvironmental model in which quasi-estuarine circulation compliments and enhances the effect of a stratified water column can account for both depletion of dissolved oxygen in the bottom environments and the absence of oxygen replenishment during black-shale deposition. Periods of abundant clastic influx from fluvial environments to the east probably account for the abundance of clays in the greenish-gray shale as well as the small amounts of oxygen necessary to support the depauparate, opportunistic, benthic faunas found there. These pulses of greenish-gray clastics were short-lived and eventually were replaced by anaerobic conditions and low rates of clastic sedimentation which characterized most of black-shale deposition.

  6. A structurally controlled fan-delta complex at the southern margin of the peninsular range forearc basin complex (Baja California)

    Energy Technology Data Exchange (ETDEWEB)

    Morris, W.R.; Busby-Spera, C. (Univ. of California, Santa Barbara (USA))

    1990-05-01

    A confined trunk fan delta and its structurally controlled tributary fan deltas are extremely well exposed along the southern margin of the Rosario embayment. This fan-delta complex consists of nonmarine to deep marine deposits almost continuously exposed for over 20 km in the down-paleoslope direction. Facies and stratal patterns in the fan-delta complex were controlled by local faulting, climatic variation, and eustasy, resulting in relative sea level fluctuations. Basin bathymetry and drainage patterns were controlled by a series of half-grabens that formed along north-south-trending faults that lay along the northern margin of an east-west-trending depression. Breccias were initially shed into the north-south-trending half-grabens; axial drainage systems were later established within the grabens, making up the tributary fan deltas. These tributary fan deltas fed a voluminous trunk fan delta confined to the east-west-trending depression. The trunk and tributary fan delta deposits show two major progradational to retrogradational cycles that record relative sea level fluctuations. Progradation in the shallow-marine environment is represented by conglomerate channels cut into ripple-laminated or bioturbated siltstone and HCS sandstones, overlain by conglomerate mouth bar deposits interstratified with nearshore sandstone deposits. Retrogradation in the shallow marine environment is recorded by either a vertical clastic facies transition or a clastic-carbonate facies transition. The clastic facies transition consists of nearshore sandstone deposits overlain by offshore bioturbated siltstones. The clastic-carbonate facies transition consists of the development of red algal patch reefs and rhodoliths on top of fan-delta conglomeratic lobes, mudstone and sandstone bank channel margins, or paleobasement highs. The clastic-carbonate facies transition reflects low sediment supply controlled by climatic conditions.

  7. Marine geological study of the continental shelf around Heugsan island, SE Korea

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chi Won; Jin, Jae Hwa; Shin, Won Cheol; Kim, Won Sik; Kim, Jung Ki; Kim, Sang Woo; Lee, Ho Yong; Chang, Cheong Hae; Kim, Sung Woo; Lee, Yoon Oh; Park, Young Soo; Bahng, Hyo Ky [Korea Inst. of Geology Mining and Materials, Taejon (Korea, Republic of)

    1995-12-01

    This annual report is a result of marine geological and geophysical surveys conducted in 1995 to obtain a variety of data available for mapping Korean continental shelf geology. The study area is situated off city of Mokpo, comprising a rectangle enclosed by lines connecting between 34 degree 30`N and 35 degree 00`N, and between 125 degree 00`E and 126 degree 00`E. Geophysical surveys included water-depth sounding, sea floor side scanning, 3.5 khz sub-bottom profiling, air gun seismic reflection profiling and measurement of total magnetic intensity. During geological terms, 102 grab samples were collected from a grid of 4 miles x 4 miles spaced on the sea floor, and 31 sediment cores were raised from the proper sites determined by preliminary interpretation of geophysical data. The survey vessel, R/V Tamhae, was positioned by a GPS system (Loran-GPS 10X; Trimble Navigation Co.). The sea floor is largely covered with seven distinct types of surface and near-surface sediments; (1) massive sand, (2) homogeneous clay, (3) laminated silt, (4) bioturbated muddy sand, (5) massive silt, (6) bioturbated gravelly muddy sand, and (7) shell aggregate. Based on synthetic interpretation of high-resolution (3.5 khz) seismic data and correlated sedimentary facies, the shallow substratum comprises low-stand, transgressive and high-stand systems tracts (LST, TST and HST, respectively) formed during the last glacio-eutectics regression and transgression. Air gun seismic profiles show that pre-Pleistocene sediments comprise 4 sequences designated as B, C, D, and E, respectively. (author). 63 refs.

  8. Depositional environment, ichnological features and oxygenation of Permian to earliest Triassic marine sediments in central Spitsbergen, Svalbard

    Directory of Open Access Journals (Sweden)

    Alfred Uchman

    2016-05-01

    Full Text Available Late Early Permian–lowermost Triassic carbonate, siliceous (spiculites and clastic marine sediments in the Marmierfjellet area (Isfjorden, central Spitsbergen contain a relatively diverse and abundant trace fossil assemblage providing important information about the depositional processes. The Vøringen Member (Late Artinskian–Kungurian of the Kapp Starostin Formation (Late Artinskian–? Changhsingian contains trace fossils (Nereites, Phycosiphon, Zoophycos and Arenicolites—common in tempestites typical of the proximal–archetypal Cruziana ichnofacies, which indicates lower shoreface. Nereites, Phycosiphon and Zoophycos, accompanied by other rare trace fossils, characterize the Svenskegga and Hovtinden members of the Kapp Starostin Formation. They are interpreted as the distal Cruziana ichnofacies, possibly transitional to the Zoophycos ichnofacies typical of the lower offshore zone. However, the sporadic occurrences of Arenicolites and Macaronichnus can point to episodic shallowing to upper offshore–lower shoreface. The lowest part of the Triassic Vikinghøgda Formation (Induan–Olenekian contains a very low-diverse ichnoassemblage composed of a few simple and branched forms ascribed to the impoverished Cruziana ichnofacies (lower to upper offshore environment, which is attributed to the early recovery stage after the Permian–Triassic extinction. The trace fossils and loss of primary sedimentary structures caused by intense bioturbation throughout most of the section point to generally oxygenated pore waters on the sea floor. However, some horizons, especially laminated black shales, display reduced or no bioturbational activity. These horizons also show high V/(V+Ni ratios, which indicate oxygen-depleted sediments with periods of anoxic conditions. A remarkable black shale unit deposited under anoxic and sulphidic conditions occurs at the Permian–Triassic transition.

  9. Interbasinal marker intervals——A case study from the Jurassic basins of Kachchh and Jaisalmer, western India

    Institute of Scientific and Technical Information of China (English)

    PANDEY; Dhirendra; Kumar; FüRSICH; Franz; Theodor

    2009-01-01

    The Kachchh Basin and the Jaisalmer Basin are two neighboring Mesozoic sedimentary basins at the western margin of the Indian craton. The Jurassic succession of the Kachchh Basin is more complete and more fossiliferous than that of the Jaisalmer Basin. Consequently, intrabasinal correlation of the sedimentary units has been possible in the Kachchh Basin, but not in the Jaisalmer Basin. However, some marker beds existing in the Kachchh Basin can be recognized also in the Jaisalmer Basin. Ammonite evidence shows that they are time-equivalent. The following four units form marker intervals in both basins: (1) the pebbly rudstone unit with Isastrea bernardiana and Leptosphinctes of the Kaladongar Formation (Kachchh Basin) and the Isastrea bernardiana-bearing rudstone of the Jaisalmer Formation (Jaisalmer Basin) both represent transgressive systems tract deposits dated as Late Bajocian; (2) bioturbated micrites with anomalodesmatan bivalves within the Goradongar Yellow Flagstone Member (Kachchh Basin) and bioturbated units in the Fort Member (Jaisalmer Basin) represent maximum flooding zone deposits of the Middle to Late Bathonian; (3) trough-crossbedded, sandy packto grainstones of the Raimalro Limestone Member (Kachchh Basin) and the basal limestone-sandstone unit of the Kuldhar section of the Jaisalmer Formation (Jaisalmer Basin) correspond to Late Bathonain transgressive systems tract deposits; and (4) ferruginous ooid-bearing carbonates with hardgrounds of the Dhosa Oolite member (Kachchh Basin) and the middle part of the Jajiya Member (Jaisalmer Basin) are Oxfordian transgressive systems tract deposits. The fact that in both basins similar biofacies prevailed during certain time intervals demonstrates a common control of their depositional history. As the two basins represent different tectonic settings, the most likely controlling factors were the relative sea-level changes produced by eustatic processes, a common subsidence history of the northwestern margin of

  10. The effect of macrofaunal disturbance on Cerastoderma edule post-larvae

    Science.gov (United States)

    Whitton, Timothy Andrew; Jenkins, Stuart Rees; Richardson, Christopher Allan; Hiddink, Jan Geert

    2016-06-01

    Populations of the Common European cockle (Cerastoderma edule) often have highly patchy distributions and variable recruitment success. One of the proposed reasons is that high densities of filter feeders and/or bioturbators are thought to reduce the success of larval settlement and post-settlement survival, but the direct causal processes driving these observations are not clearly identified and validated. Through combined field and laboratory experiments, we test the hypothesis that macrofauna cause decreases in post-larval density through feeding and movement activities. The effect of excluding the bioturbating lugworm Arenicola marina and filter-feeding adult cockles on post-larval cockle densities was estimated in separate field experiments at two locations from the time of initial larval settlement in May 2012 to late summer August 2012. Lugworm exclusion led to a significant increase in cockle post-larval densities whereas the opposite was true for adult cockles, where exclusion led to a reduction in C. edule post-larval density. Although clear effects were observed in the field, experiments conducted in the laboratory failed to detect changes in mortality or byssus drifting of post-larvae as a consequence of macrofaunal activity. This study demonstrates that the presence of macrofauna can have both positive and negative effects on post-settlement density of C. edule post-larvae. Thus the density, distribution and identity of macrofauna have significant effects on the density and spatial distribution of C. edule post-larvae during the post-settlement period. These observations have implications for conservation and fishery management of this species.

  11. Sedimentary facies of the central part of radial tidal sand ridge system of the eastern China coast

    Institute of Scientific and Technical Information of China (English)

    Yong YIN; Xinqin ZOU; Dakui ZHU; Jiaxiang HUANG

    2008-01-01

    A unique radial tidal sand ridge system (RTSRS) has developed under a complex tidal current field on the eastern China coast between the Yangtze River delta to the south and the abandoned Yellow River (Huanghe) delta to the north. The present study examines the sedimentary evolution of a ridge-channel pair in the central RTSRS. Three cores, with two on the ridges and one in the channel, were drilled to reveal the late Pleistocene-Holocene deposits of the system. Five sedimentary facies were distinguished, i.e. ridge-shallow subtidal facies, ridge-deep subtidal facies, near-surface channel bottom facies, middle tidal flat facies and low tidal flat facies. The ridge-shallow subtidal facies consists of sandy strata with ripple cross bed-dings, horizontal lamina, and massive beddings. Bioturbation seldom occurs. The ridge-deep subtidal facies is primarily characterized by sandy and muddy interlayers with common flaser and lenticular bedding structures. Bioturbation appears abundantly. Massive and graded sediment sequences of storm origin are pre-sent as characterized by rich shell fragments. The near-surface channel bottom facies consists of loose, soft, clayey silt deposits with deformed sedimentary layers. This facies occurs in the deeper part of the active chan-nels. The middle tidal flat and lower tidal flat facies composed of silt-clay couplets prevailed primarily in the tidal flats. Incomplete sedimentary successions show that coastal plain deposits dominate in the study area during 12-13 ka B.P. The sandy ridge and channel facies became dominant during 4 6 ka B.P. when the sea level receded temporarily. Tidal ridge and channel in the study area became active during the last four decades. Sediment reworking due to typhoon and sandy ridge migration plays a key role in shaping the present radial ridge system.

  12. Spatial distribution of southern brown shrimp (Farfantepenaeus subtilis on the Amazon continental shelf: a fishery, marine geology and GIS integrated approach

    Directory of Open Access Journals (Sweden)

    Déborah E. G. Martins

    2015-12-01

    Full Text Available Abstract The spatial distribution of the southern brown shrimp Farfantepenaeus subtilis (Pérez-Farfante, 1967 was studied based on industrial fishing fleet activities and is associated with geological and oceanographic characteristics of the benthonic environments on the Amazon continental shelf. Using a geographical information system (GIS this paper sought to calculate the relative abundance of brown shrimp based on catch per unit effort (CPUE and compare it with bathymetry, type of sedimentary structure, sedimentation rate and bottom salinity. As a result, we have concluded that the relative abundance (in terms of CPUE is not uniformly distributed in space. Spatial analysis indicates that commercial trawling efforts were made in the (foreset region of the subaqueous Amazon delta at depths of 40 to 60 m. In this region, prawn are responsible for the bioturbation of the sediments and the creation of a sedimentary structure called mottled mud. In the foreset region, sedimentation rates progressively increased up to 10 cm.yr-1; re-suspension was reduced and bottom salinity was high (~ 36. It appears that all of these factors define a stable muddy area with intense bioturbation. This notable biological activity is to be explained by the occurrence of a high F. subtilis abundance that appears to originate in a microbial loop. We concluded that by combining fishery information with environmental data from a GIS, it was possible to identify abundance distribution patterns for southern brown shrimp and other economically important fishery resources and to understand how they change on a large spatial-scale.

  13. Benthic Oxygen Demand in Three Former Salt Ponds Adjacent to South San Francisco Bay, California

    Science.gov (United States)

    Topping, Brent R.; Kuwabara, James S.; Athearn, Nicole D.; Takekawa, John Y.; Parcheso, Francis; Henderson, Kathleen D.; Piotter, Sara

    2009-01-01

    Sampling trips were coordinated in the second half of 2008 to examine the interstitial water in the sediment and the overlying bottom waters of three shallow (average depth 2 meters). The water column at all deployment sites was monitored with dataloggers for ancillary water-quality parameters (including dissolved oxygen, salinity, specific conductance, temperature, and pH) to facilitate the interpretation of benthic-flux results. Calculated diffusive benthic flux of dissolved (0.2-micron filtered) oxygen was consistently negative (that is, drawn from the water column into the sediment) and ranged between -0.5 x 10-6 and -37 x 10-6 micromoles per square centimeter per second (site averages depicted in table 2). Assuming pond areas of 1.0, 1.4, and 2.3 square kilometers for ponds A16, A14, and A3W, respectively, this converts to an oxygen mass flux into the ponds' sediment ranging from -1 to -72 kilograms per day. Diffusive oxygen flux into the benthos (listed as negative) was lowest in pond A14 (-0.5 x 10-6 to -1.8 x 10-6 micromoles per square centimeter per second) compared with diffusive flux estimates for ponds A16 and A3W (site averages -26 x 10-6 to -35 x 10-6 and -34 x 10-6 to -37 x 10-6 micromoles per square centimeter per second, respectively). These initial diffusive-flux estimates are of the order of magnitude of those measured in the South Bay using core-incubation experiments (Topping and others, 2004), which include bioturbation and bioirrigation effects. Estimates of benthic oxygen demand reported herein, based on molecular diffusion, serve as conservative estimates of benthic flux because solute transport across the sediment-water interface can be enhanced by multidisciplinary processes including bioturbation, bioirrigation, ground-water advection, and wind resuspension (Kuwabara and others, 2009).

  14. Missoula flood dynamics and magnitudes inferred from sedimentology of slack-water deposits on the Columbia Plateau, Washington

    International Nuclear Information System (INIS)

    Sedimentological study of late Wisconsin, Missoula-flood slack-water sediments deposited along the Columbia and Tucannon Rivers in southern Washington reveals important aspects of flood dynamics. Most flood facies were deposited by energetic flood surges (velocities>6 m/sec) entering protected areas along the flood tract, or flowing up and then directly out of tributary valleys. True still-water facies are less voluminous and restricted to elevations below 230 m. High flood stages attended the initial arrival of the flood wave and were not associated with subsequent hydraulic ponding upslope from channel constrictions. Among 186 flood beds studied in 12 sections, 57% have bioturbated tops, and about half of these bioturbated beds are separated from overlying flood beds by nonflood sediments. A single graded flood bed was deposited at most sites during most floods. Sequences in which 2-9 graded beds were deposited during a single flood are restricted to low elevations. These sequences imply complex, multi-peaked hydrographs in which the first flood surge was generally the largest, and subsequent surges were attenuated by water already present in slack-water areas. Slack-water - sediment stratigraphy suggests a wide range of flood discharges and volumes. Of >40 documented late Wisconsin floods that inundated the Pasco Basin, only about 20 crossed the Palouse-Snake divide. Floods younger than the set-S tephras from Mount St.Helens were generally smaller than earlier floods of late Wisconsin age, although most still crossed the Palouse-Snake divide. These late floods primarily traversed the Cheney-Palouse scabland because stratigraphy of slack-water sediment along the Columbia River implies that the largest flood volumes did not enter the Pasco Basin by way of the Columbia River. 47 refs., 17 figs., 2 tabs

  15. Linking hydropedology and ecosystem services: differential controls of surface field saturated hydraulic conductivity in a volcanic setting in central Mexico

    Directory of Open Access Journals (Sweden)

    A. Gómez-Tagle

    2009-03-01

    Full Text Available In this study the variation of field saturated soil hydraulic conductivity (Kfs as key control variable and descriptor of infiltration was examined by means of a constant head single ring infiltrometer. The study took place in five coverage types and land uses in a volcanic setting in central Mexico. The tested hypothesis was that there exist a positive relationship between plant cover and surface Kfs for the study area. The examined coverage types included; Second growth pine-oak forest, pasture land, fallow land, gully and Cupresus afforestation. Results indicate that Kfs did not depend exclusively of plant cover; it was related to surface horizontal expression of the unburied soil horizons and linked to land use history. Therefore the Kfs measured at a certain location did not depend exclusively of the actual land use, it was also influenced by soil bioturbation linked to plant succession patterns and land use management practices history. The hypothesis accounts partially the variation between sites. Kfs under dense plant cover at the Cupresus afforestation was statistically equal to that measured at the fallow land or the gully sites, while second growth pine-oak forest Kfs figures were over an order of magnitude higher than the rest of the coverage types. The results suggest the relevance of unburied soil horizons in the soil hydrologic response when present at the surface. Under these conditions loosing surface soil horizons due to erosion, not only fertility is lost, but environmental services generation potential. A conceptual model within the hydropedological approach is proposed. It explains the possible controls of Kfs, for this volcanic setting. Land use history driven erosion plays a decisive role in subsurface horizon presence at the surface and soil matrix characteristic determination, while plant succession patterns seem to be strongly linked to soil bioturbation and

  16. Kinetic quantification of vertical solid matter transfers in soils by a multi-tracers approach

    Science.gov (United States)

    Jagercikova, Mariannaa; Cornu, Sophiea; Bourl`es, Didierb; Evrard, Olivierc; Alainb, V.'eron; Hatt'e, Christinec; Ayrault, Sophiec; Jérômea, Balesdent

    2015-04-01

    We will present a novel multi-tracers method - combining different isotopic systems (137 Cs, 210 Pb (xs), meteoric 10 Be, 206/207 Pb, δ13 C, 14 C) with numerical modeling based on a non-linear diffusion-convection equation with depth dependent parameters - to quantify vertical transfer of solid matter in Luvisols, namely clay translocation and bioturbation. Our results show that as much as 91 ± 9 % and 80 ± 9 % of 137Cs and 10Be, respectively, are associated with the clay size fraction (0-2 µm) and provide therefore relevant tracers to investigate vertical transfer of solid matter in soils with pH > 5 and low organic carbon contents. Lead partitioning between different solid phases is more complex. Considering two spatial distributions of isotopes (macropores or soil matrix) depending on the contribution of a fraction inherited from the loess parent material to the soil concentration, we built up a multi-tracers modeling approach that simulates the experimental data with the common set of transfer parameters and allows us to quantify the relative contributions of vertical solid matter transfers to present-day 0-2 µm vertical distributions. Clay translocation is responsible for 9 to 66 % of clay accumulation in the Bt-horizon. The diffusion coefficients quantifying the rate of soil mixing by bioturbation yields values that are significantly higher than those estimated in previous ecological studies. Modeling the kinetics of solid matter transfer at various spatial and temporal scales should become a reference method in modern pedogenic and critical zone studies.

  17. Sediment geochemistry and accumulation rates on the northeastern shelf of the Gulf of Cádiz (SW Iberian Peninsula)

    International Nuclear Information System (INIS)

    Geochemistry, total organic carbon and total nitrogen of three sediment cores collected in the Gulf of Cádiz and the Guadalquivir prodelta areas in Spain were investigated. The C/N ratio, mostly around 10, seems to indicate a predominantly marine origin for the sedimentary organic matter. Major and minor elements (Si, Ti, Al, Fe, Mg, Ca, K, Na, P, S) and trace elements (Mn, Sc, V, Cr, Ni, Cu, Zn, Rb, Sr, Y, Zr, Ba, Ce, Pb, Hg) showed significant differences in bulk chemical composition between the two areas. Despite the effects of bioturbation, vertical changes in downcore profiles of heavy metals occur only in the cores of the Cádiz area, although the concentrations keep to low levels. The relatively high concentrations of Zr and Y, elements commonly associated with the heavy minerals fraction, at the top of cores from the Cádiz area are attributed to an enrichment of heavy minerals related to selective transport that concentrates this fraction. 137Cs and 210Pb activities in one of the two sediment cores collected in the Gulf of Cádiz were also measured. The distribution of excess 210Pb was used to determine the modern (last 100 yr) mass accumulation rate and the depth of sediment mixing on the continental shelf of the gulf. Estimated sediment accumulation rate was 0.1 g cm-2 yr-1. The uppermost 4 cm had uniform excess 210Pb activity profiles above a region of steadily decreasing 210Pb activity, and this phenomenon was attributed to sediment mixing (bioturbation). 137Cs activity was lower than 3 Bq kg-1 and the profile does not show evidence of fallout peaks

  18. Identification of the most influential factors in the Norwegian guidelines for risk assessment of dispersion of contaminants from sediments.

    Science.gov (United States)

    Saloranta, Tuomo M; Ruus, Anders; Borgå, Katrine

    2011-10-01

    The Norwegian guidelines for risk assessment of contaminated sediments are used to identify areas of concern where remediation may be needed to meet the governmental long-term goal of clean fjords and harbors along the Norwegian coastline. By a thorough sensitivity analysis, this study identifies the most influential factors and parameters for the Tier 2A model in this risk guideline, which are used to estimate fluxes of contaminants from sediments due to diffusion and bioturbation (F(diff)), resuspension caused by ship traffic (F(skipnorm)), and uptake and predation of benthic biota (F(org)). The sensitivity analysis is run for 36 different scenarios combining 3 different sizes of contaminated area, 3 harbor types, and 3 persistent organic pollutants, namely lindane (γ-hexachlorocyclohexane), benzo[a]pyrene, and 2,2',4,4',5,5'-hexachlorobiphenyl (PCB-153), as well as the metal mercury (Hg). The most influential parameters vary from scenario to scenario, but generally 5 parameters appear to be particularly influential for the fluxes and transport estimated by the Tier 2A model: flux of organic carbon to sediment (OC(sed)), factor for increased diffusion due to bioturbation (a), sediment-water partitioning coefficient (K(d)), benthic biota-water bioconcentration factor (BCF(fisk)), and mass of resuspended fine sediment during arrival or departure of a ship (m(sed)). We also quantify which of the 3 fluxes (F(diff), F(skipnorm), and F(org)) dominate in the different scenarios. Our sensitivity analysis results can be used by authorities, problem owners, consultants, and environmental managers involved in contaminated sediment management to gain insight on the key processes and parameters and to focus their site-specific or laboratory-based measurement efforts on the key parameters and thus increase efficiency and reliability in the contaminated sediment risk assessment. PMID:21384542

  19. Presentation, calibration and validation of the low-order, DCESS Earth System Model (Version 1

    Directory of Open Access Journals (Sweden)

    J. O. Pepke Pedersen

    2008-11-01

    Full Text Available A new, low-order Earth System Model is described, calibrated and tested against Earth system data. The model features modules for the atmosphere, ocean, ocean sediment, land biosphere and lithosphere and has been designed to simulate global change on time scales of years to millions of years. The atmosphere module considers radiation balance, meridional transport of heat and water vapor between low-mid latitude and high latitude zones, heat and gas exchange with the ocean and sea ice and snow cover. Gases considered are carbon dioxide and methane for all three carbon isotopes, nitrous oxide and oxygen. The ocean module has 100 m vertical resolution, carbonate chemistry and prescribed circulation and mixing. Ocean biogeochemical tracers are phosphate, dissolved oxygen, dissolved inorganic carbon for all three carbon isotopes and alkalinity. Biogenic production of particulate organic matter in the ocean surface layer depends on phosphate availability but with lower efficiency in the high latitude zone, as determined by model fit to ocean data. The calcite to organic carbon rain ratio depends on surface layer temperature. The semi-analytical, ocean sediment module considers calcium carbonate dissolution and oxic and anoxic organic matter remineralisation. The sediment is composed of calcite, non-calcite mineral and reactive organic matter. Sediment porosity profiles are related to sediment composition and a bioturbated layer of 0.1 m thickness is assumed. A sediment segment is ascribed to each ocean layer and segment area stems from observed ocean depth distributions. Sediment burial is calculated from sedimentation velocities at the base of the bioturbated layer. Bioturbation rates and oxic and anoxic remineralisation rates depend on organic carbon rain rates and dissolved oxygen concentrations. The land biosphere module considers leaves, wood, litter and soil. Net primary production depends on atmospheric carbon dioxide concentration and

  20. Presentation, calibration and validation of the low-order, DCESS Earth System Model

    Directory of Open Access Journals (Sweden)

    J. O. P. Pedersen

    2008-06-01

    Full Text Available A new, low-order Earth system model is described, calibrated and tested against Earth system data. The model features modules for the atmosphere, ocean, ocean sediment, land biosphere and lithosphere and has been designed to simulate global change on time scales of years to millions of years. The atmosphere module considers radiation balance, meridional transport of heat and water vapor between low-mid latitude and high latitude zones, heat and gas exchange with the ocean and sea ice and snow cover. Gases considered are carbon dioxide and methane for all three carbon isotopes, nitrous oxide and oxygen. The ocean module has 100 m vertical resolution, carbonate chemistry and prescribed circulation and mixing. Ocean biogeochemical tracers are phosphate, dissolved oxygen, dissolved inorganic carbon for all three carbon isotopes and alkalinity. Biogenic production of particulate organic matter in the ocean surface layer depends on phosphate availability but with lower efficiency in the high latitude zone, as determined by model fit to ocean data. The calcite to organic carbon rain ratio depends on surface layer temperature. The semi-analytical, ocean sediment module considers calcium carbonate dissolution and oxic and anoxic organic matter remineralisation. The sediment is composed of calcite, non-calcite mineral and reactive organic matter. Sediment porosity profiles are related to sediment composition and a bioturbated layer of 0.1 m thickness is assumed. A sediment segment is ascribed to each ocean layer and segment area stems from observed ocean depth distributions. Sediment burial is calculated from sedimentation velocities at the base of the bioturbated layer. Bioturbation rates and oxic and anoxic remineralisation rates depend on organic carbon rain rates and dissolved oxygen concentrations. The land biosphere module considers leaves, wood, litter and soil. Net primary production depends on atmospheric carbon dioxide concentration and

  1. The geoarchaeology of urban wastes: from refuses to activities and towns organisation (France, 6th c. BC - 10th c. aD)

    Science.gov (United States)

    Borderie, Q.; Cammas, C.; Petit, C.

    2012-04-01

    In an urban context, geoarchaeological study of man-environment interaction is often neglected, although recent studies of urbic anthrosols and human induced processes show that it can provide a great amount of data. The sedimentary matrix of the archaeological layers, especially its organic and heavy metal contents (phosphore, organic carbon, lead…) and the pedo-sedimentary processes (such as bioturbation, percolation, decay of organic matter…), are evidence of ancient lifestyle and waste disposal habits. This data are even more useful when archaeological evidence is rare or inefficient, such as in the early medieval Dark Earth. This paper is based on several geoarchaeological studies undertaken since the 1990 in French towns ranging from the Iron Age to the early Middle Ages (Paris, Beauvais, Bayeux, Noyon, Macon, Metz, Lattara…), mainly from rescue excavations. Multi-scale, 3D and fine scale analyses of archaeological stratigraphy are combined with micromorphological studies of undisturbed samples and grain size as well as geochemical analysis of bulk samples (CaCO3, C/N, Fe, Pb, Zn, Cu…). Spatial sampling reveals complex pattern of activities in finely stratified and well defined architectural context like Lattara (Iron Age). Organic refuses were found mainly in specific urban spaces like courtyards or squares and animal housing areas could be delineate. In more undifferentiated stratigraphy (early medieval Dark Earth), bioturbation is one of the main formation process and seems to have obliterated others. Thus, we analysed the 3D pattern of macro-artefacts on field, combined with micromorphology, geochemical and semi quantitative counting of micro-artefacts on thin sections. It allowed us to characterise Dark Earth by the type of activity refuses, in relation with the pedo-sedimentary context and the uses of the areas. It also allowed us to assess the characters induced by in situ activities and those due to the local background. Moreover, in Metz

  2. Ichnofabrics and their Sedimentary Environment of the Lower Permian Taiyuan Formation, Western Henan%豫西地区下二叠统太原组遗迹组构及其沉积环境

    Institute of Scientific and Technical Information of China (English)

    宋慧波; 金毅; 胡磊; 胡斌

    2012-01-01

    豫西下二叠统太原组中发育丰富的遗迹化石,常见有Zoophycos,Taenidium,Thalassinoides,Teichichnus,Gordia,Nereites,Chondrites和Planolites等,部分灰岩层中还发育生物扰动构造.根据遗迹化石的形态、组成、产状、分布特征以及丰度、分异度、生物扰动程度的不同,在研究区太原组碳酸盐岩中共识别出5种遗迹组构,包括类型A——Gordia-Planolites遗迹组构、类型B—— Rhizocoralliurn- Thalassinoides遗迹组构、类型C—— Zoophycos- Taenidium遗迹组构、类型D——Zoophycos- Speckle burrow强生物扰动遗迹组构、类型E——Chondrites- Nereites遗迹组构.其中类型C根据Zoophycos在剖面上所展现的各种特征,又可细分为3种类型,即类型C-1,C-2和C-3.通过分析宿主岩的沉积特征,表明太原组碳酸盐岩中的遗迹组构主要分布于潟湖潮坪和台内浅滩(类型A)、正常天气浪基面之上的浅海上部或局限台地(类型B,类型C-1和类型C-2)、正常天气浪基面之下的开阔台地(类型C-3,类型D)和风暴浪基面之下的浅海下部或水动力条件类似的较闭塞的沉积环境中(类型E).%The abundant trace fossils were developed in the Lower Permian Taiyuan Formation of western Henan, in which common components include Zoophycos, Taenidium, Thalassinoides, Teichichnus, Gordia,Nereites,Chondrites,Planolites and so on, and strong bioturbation structures were found in part of limestone beds. Based on the differences of trace fossil characteristics in morphology, composition, occurrence, distribution, aboundance, biotaldiversity and bioturbation degree, five types of ichnofabrics have been recognized in the carbonates of the Taiyuan Formation in this study area,and they are named as follows: Type A, GordiarPlanolites ichnofabric; Type B, Rhizocorallium-Thalassinoides ichnofabric; Type C, Zoophycos-Taenidium ichnofabrics Type D, Zoophycos- speckle burrow (strong bioturbation) ichnofabric; Type E, Chondrites

  3. The Bakken - An Unconventional Petroleum and Reservoir System

    Energy Technology Data Exchange (ETDEWEB)

    Sarg, J.

    2011-12-31

    An integrated geologic and geophysical study of the Bakken Petroleum System, in the Williston basin of North Dakota and Montana indicates that: (1) dolomite is needed for good reservoir performance in the Middle Bakken; (2) regional and local fractures play a significant role in enhancing permeability and well production, and it is important to recognize both because local fractures will dominate in on-structure locations; and (3) the organic-rich Bakken shale serves as both a source and reservoir rock. The Middle Bakken Member of the Bakken Formation is the target for horizontal drilling. The mineralogy across all the Middle Bakken lithofacies is very similar and is dominated by dolomite, calcite, and quartz. This Member is comprised of six lithofacies: (A) muddy lime wackestone, (B) bioturbated, argillaceous, calcareous, very fine-grained siltstone/sandstone, (C) planar to symmetrically ripple to undulose laminated, shaly, very fine-grained siltstone/sandstone, (D) contorted to massive fine-grained sandstone, to low angle, planar cross-laminated sandstone with thin discontinuous shale laminations, (E) finely inter-laminated, bioturbated, dolomitic mudstone and dolomitic siltstone/sandstone to calcitic, whole fossil, dolomitic lime wackestone, and (F) bioturbated, shaly, dolomitic siltstone. Lithofacies B, C, D, and E can all be reservoirs, if quartz and dolomite-rich (facies D) or dolomitized (facies B, C, E). Porosity averages 4-8%, permeability averages 0.001-0.01 mD or less. Dolomitic facies porosity is intercrystalline and tends to be greater than 6%. Permeability may reach values of 0.15 mD or greater. This appears to be a determinant of high productive wells in Elm Coulee, Parshall, and Sanish fields. Lithofacies G is organic-rich, pyritic brown/black mudstone and comprises the Bakken shales. These shales are siliceous, which increases brittleness and enhances fracture potential. Mechanical properties of the Bakken reveal that the shales have similar

  4. Rapid shoreline erosion induced by human impacts in a tropical muddy coast context, an example from western French Guiana.

    Science.gov (United States)

    Brunier, Guillaume; Anthony, Edward; Gardel, Antoine

    2015-04-01

    The Guyanas coast (French Guiana, Surinam and Guiana) is the longest muddy coast in the world (1500 km). It is under the influence of mud banks in transit from the Amazon delta in Brazil to the Orinoco delta in Venezuela. This westward mud bank migration induces a strong geomorphic control on the shoreline which can be summarized in terms of "bank" (shoreline advance and wave energy dissipation) and "inter-bank" phases (erosion of shoreline by waves). Our study site, rice polders close to Mana city (western French Guiana), is a fine example of the exacerbation, by human activities, of the erosional dynamics on this muddy coast during an "inter-bank" phase. The polders cover 50,000 ha, in 200 x 600 m compartments flanked by earth dikes and canals. They were built in the muddy Holocene coastal plain in the 1980s and are rapidly eroding. Waves (mean significant height = 1.5 m height) comprise Atlantic swell and local trade wind-waves, and the tidal context is semi-diurnal and meso-tidal. We determined historical shoreline evolution from satellite (Landsat & SPOT) and orthophotography images, and conducted four field campaigns between October 2013 and October 2014, comprising topographic (RTK-DGPS) and hydrodynamic (pressure sensors) measurements. The results show intense erosion of 150 m/year affecting the polders since 2001, and lesser retreat (30 to 100 m/year) of the adjacent sectors colonized by mangrove forests. The erosive shoreface shows the same structure in each polder compartment: a chenier beach which freely retreats backwards under the influence of wave overwash. The chenier retreat rate is 100 m/year and it appears to be more intense (net retreat of 45 m) during the high wave-energy season (December to March), which generates more overwashing. In front of the chenier, we observed a large (50 m) inter-tidal mud bed showing different levels of induration and bioturbation by mangrove roots. The mud shorefaces exhibit an erosion rate of 100 m/year on average

  5. Occurrence of benthic microbial nitrogen fixation coupled to sulfate reduction in the seasonally hypoxic Eckernförde Bay, Baltic Sea

    Directory of Open Access Journals (Sweden)

    V. J. Bertics

    2013-03-01

    Full Text Available Despite the worldwide occurrence of marine hypoxic regions, benthic nitrogen (N cycling within these areas is poorly understood and it is generally assumed that these areas represent zones of intense fixed N loss from the marine system. Sulfate reduction can be an important process for organic matter degradation in sediments beneath hypoxic waters and many sulfate-reducing bacteria (SRB have the genetic potential to fix molecular N (N2. Therefore, SRB may supply fixed N to these systems, countering some of the N lost via microbial processes, such as denitrification and anaerobic ammonium oxidation. The objective of this study was to evaluate if N2 fixation, possibly by SRB, plays a role in N cycling within the seasonally hypoxic sediments from the Eckernförde Bay, Baltic Sea. Monthly samplings were performed over the course of one year to measure nitrogenase activity (NA and sulfate reduction rates, to determine the seasonal variations in bioturbation (bioirrigation activity and important benthic geochemical profiles, such as sulfur and N compounds, and to monitor changes in water column temperature and oxygen concentrations. Additionally, at several time points, the active N-fixing community was examined via molecular tools. Integrated rates of N2 fixation (approximated from NA and sulfate reduction showed a similar seasonality pattern, with highest rates occurring in August (approx. 22 and 880 nmol cm−3 d−1 of N and SO42−, respectively and October (approx. 22 and 1300 nmol cm−3 d−1 of N and SO42− respectively, and lowest rates occurring in February (approx. 8 and 32 nmol cm−3 d−1 of N and SO42−, respectively. These rate changes were positively correlated with bottom water temperatures and previous reported plankton bloom activities, and negatively correlated with bottom water oxygen concentrations. Other variables that also appeared to play a role in rate determination were bioturbation, bubble irrigation and winter storm

  6. Variations in glacial and interglacial marine conditions over the last two glacial cycles off northern Greenland

    Science.gov (United States)

    Löwemark, Ludvig; Chao, Weng-Si; Gyllencreutz, Richard; Hanebuth, Till J. J.; Chiu, Pin-Yao; Yang, Tien-Nan; Su, Chih-Chieh; Chuang, Chih-Kai; León Dominguez, Dora Carolina; Jakobsson, Martin

    2016-09-01

    Five sediment cores from the Lomonosov Ridge and the Morris Jesup Rise north of Greenland show the history of sea-ice coverage and primary productivity over the last two glacial cycles. Variations in Manganese content, benthic and planktonic foraminifera, bioturbation, and trace fossil diversity are interpreted to reflect differences in sea-ice cover and sediment depositional conditions between the identified interglacials. Marine Isotope Stage (MIS) 1 and MIS 2 are represented by thin (units while the preceding interglacial MIS 5 and glacial MIS 6 are characterized by thick (10-20 cm) deposits. Foraminiferal abundances and bioturbation suggest that MIS 1 was generally characterized by severe sea-ice conditions north of Greenland while MIS 5 appears to have been considerably warmer with more open water, higher primary productivity, and higher sedimentation rates. Strengthened flow of Atlantic water along the northern continental shelf of Greenland rather than development of local polynyas is here suggested as a likely cause for the relatively warmer marine conditions during MIS 5 compared to MIS 1. The cores also suggest distinct differences between the glacial intervals MIS 2 and MIS 6. While MIS 6 is distinguished by a relatively thick sediment unit poor in foraminifera and with low Mn values, MIS 2 is practically missing. We speculate that this could be the effect from a paleocrystic sea-ice cover north of Greenland during MIS 2 that prevented sediment delivery from sea ice and icebergs. In contrast, the thick sequence deposited during MIS 6 indicates a longer glacial period with dynamic intervals characterized by huge drifting icebergs delivering ice rafted debris (IRD). A drastic shift from thinner sedimentary cycles where interglacial sediment parameters indicate more severe sea-ice conditions gave way to larger amplitude cycles with more open water indicators was observed around the boundary between MIS 7/8. This shift is in agreement with a sedimentary

  7. Planktic foraminiferal shell thinning in the Arabian Sea due to anthropogenic ocean acidification?

    Directory of Open Access Journals (Sweden)

    H. de Moel

    2009-02-01

    Full Text Available About one third of the anthropogenic carbon dioxide (CO2 released into the atmosphere in the past two centuries has been taken up by the ocean. As CO2 invades the surface ocean, carbonate ion concentrations and pH are lowered. Laboratory studies indicate that this reduces the calcification rates of marine calcifying organisms, including planktic foraminifera. Such a reduction in calcification resulting from anthropogenic CO2 emissions has not been observed, or quantified in the field yet. Here we present the findings of a study in the Western Arabian Sea that uses shells of the surface water dwelling planktic foraminifer Globigerinoides ruber in order to test the hypothesis that anthropogenically induced acidification has reduced shell calcification of this species. We found that light, thin-walled shells from the surface sediment are younger (based on 14C and δ13C measurements than the heavier, thicker-walled shells. Shells in the upper, bioturbated, sediment layer were significantly lighter compared to shells found below this layer. These observations are consistent with a scenario where anthropogenically induced ocean acidification reduced the rate at which foraminifera calcify, resulting in lighter shells. On the other hand, we show that seasonal upwelling in the area also influences their calcification and the stable isotope (δ13C and δ18O signatures recorded by the foraminifera shells. Plankton tow and sediment trap data show that lighter shells were produced during upwelling and heavier ones during non-upwelling periods. Seasonality alone, however, cannot explain the 14C results, or the increase in shell weight below the bioturbated sediment layer. We therefore must conclude that probably both the processes of acidification and seasonal upwelling are responsible for the presence of light shells in the top of the sediment and the age

  8. Textural and Mineralogical Characteristics of Microbial Fossils in Modern and Ancient Iron (oxyhydr)oxides

    Science.gov (United States)

    Potter, S. L.; Chan, M. A.; McPherson, B. J.

    2012-12-01

    The Jurassic Brushy Basin Member of the Morrison Formation contains extensive alkaline saline lacustrine deposits rich in diagenetic iron (oxyhydr)oxides that are well exposed on the Colorado Plateau of the southwestern USA. These early diagenetic iron (oxyhydr)oxide minerals are associated with preserved diatoms and other algal forms, identified via scanning electron microscope (SEM) in thin sections of representative samples. The minerals are also associated with macroscopic bioturbation features (e.g., charophytes, burrows and fossilized dinosaur bones). Algal forms with cellular elaboration are identified by HF dissolution of bioturbation structures and examination with SEM. Collectively, these features suggest biomediated textures are preserved in early diagenetic iron (oxyhydr)oxides, and can persist for tens of millions of years. Modern microbially precipitated iron (oxyhydr)oxides and ~100ka tufa terraces from a cold spring system along Ten Mile Graben in southern Utah, USA are compared with the Morrison examples to identify modern microbial fossils and document any differences and preservation changes during diagenesis over geologic time. Two distinct suites of elements (1. C, Fe, As and 2. C, S, Se) are associated with microbial fossils in both the modern and ancient tufas, as well as the ancient Morrison specimens. The occurrence of these distinctive trace element configurations in the iron (oxyhydr)oxide minerals suggest the suites could be potential markers for biosignatures. The presence of ferrihydrite in ~100ka fossil microbial mats suggests this thermodynamically unstable mineral may also be used as a biomarker. Diagnostic trace element suites and unusual mineral phases warrant further study for their potential as biomarkers. These terrestrial iron (oxyhydr)oxide examples will: 1) document specific biomediated textures and what their origins might be (related to different processes or species), 2) show how they might persist or respond to

  9. Sedimentology and ichnology of two Lower Triassic sections in South China: Implications for the biotic recovery following the end-Permian mass extinction

    Science.gov (United States)

    Luo, Mao; George, Annette D.; Chen, Zhong-Qiang

    2016-09-01

    Biotic recovery following the end-Permian mass extinction was investigated using trace fossil and facies analysis of two Lower-Middle Triassic sections in South China. The Susong section (Lower Yangtze Sedimentary Province) comprises a range of carbonate and mudstone facies that record overall shallowing from offshore to intertidal settings. The Tianshengqiao section (Upper Yangtze Sedimentary Province) consists of mixed carbonate and siliciclastic facies deposited in shallow marine to offshore settings. Griesbachian to Dienerian ichnological records in both sections are characterized by low ichnodiversity, low ichnofabric indices (1-2) and low bedding plane bioturbation indices (1-2). Higher ichnofabric indices (3 and 4), corresponding to a dense population of diminutive ichnotaxon, in the Tianshengqiao section suggest opportunistic infaunal biotic activity during the earliest Triassic. Ichnological data from the Susong section show an increase in ichnodiversity during the late Smithian with 11 ichnogenera identified and increased ichnofabric indices of 4-5 and bedding plane bioturbation indices of 3-5. Although complex traces such as Rhizocorallium are present in Spathian-aged strata in this section, low ichnodiversity and ichnofabric indices and diminutive Planolites suggest a decline in recovery. In the Tianshengqiao section, ichnofabric indices are moderate to high (3-5) although only six ichnogenera are present and Planolites burrows are consistently small in Smithian and Spathian strata. Complex traces, such as large Rhizocorallium and Thalassinoides, and large Planolites, did not appear until the Anisian. Ichnological results from both sections record the response of organisms to unfavourable environmental conditions although the Susong section shows earlier recovery during the Smithian prior to latest Smithian-Spathian decline. This decline may have resulted from a resurgence of euxinic to anoxic marine environment in various regions of South China

  10. A modeling approach to simulate the role of anecic and endogeic earthworms in soil structure dynamics of two agricultural systems

    Science.gov (United States)

    Le Couteulx, Alexis; Wolf, Cédric; Pérès, Guénola; Hallaire, Vincent

    2015-04-01

    In agriculture, one of the main purposes of innovative systems is to preserve and improve soil quality and noticeably their physical quality. This physical quality of a soil is intimately linked with its structure, i.e. the spatial arrangement of voids and solids. It is well-known that agricultural systems may deeply impact on soil structure through their effect on various structuring processes, in particular (i) the mechanical action of soil tillage and (ii) the burrowing activity and casts production of earthworms. As the assessment of agricultural systems needs long term experiments, it is not feasible to assess them all. However, the modeling approach has been used seldom despite it seems promising. As a first step towards the modeling of agricultural systems, we propose a model that simulates the impact of earthworm bioturbation and several tillage practices on soil structure dynamics. The proposed model accounts for two earthworm ecological categories: anecics and endogeics. Anecics are split into epi-anecics and true anecics and endogeics are kept at the specific level. The model takes into account their physiological and morphological features such as their diapause period, their gut transit time or their body size. In order to simulate the bioturbation activity of earthworms, they can make six different actions: (i) burrow new paths by ingesting soil particles, (ii) move inside existing paths, (iii) move to soil surface, (iv) wait, (v) produce a subsurface cast or (vi) produce a surface cast. For the various species and groups of earthworms, the probability of these actions was adjusted from experiments and published results. This part of the model dedicated to earthworms allows to build and study their network of burrows but also the position and volume of their subsurface and surface casts. This network may be couple with models of water conductivity to assess the role of earthworm on this soil functional property. To better simulate soil structure

  11. Late Miocene fossils from shallow marine sediments in Brunei Darussalam: systematics, palaeoenvironment and ecology.

    Science.gov (United States)

    Roslim, Amajida; Briguglio, Antonino; Kocsis, László; Ćorić, Stjepan; Razak, Hazirah

    2016-04-01

    The geology of Brunei Darussalam is fascinating but difficult to approach: rainforests and heavy precipitation tend to erode and smoothen the landscape limiting rocks exposure, whereas abundant constructions sites and active quarries allow the creation of short time available outcrop, which have to be immediately sampled. The stratigraphy of Brunei Darussalam comprises mainly Neogene sediments deposited in a wave to tide dominated shallow marine environment in a pure siliciclastic system. Thick and heavily bioturbated sandstone layers alternate to claystone beds which occasionally yield an extraordinary abundance and diversity of fossils. The sandstones, when not bioturbated, are commonly characterized by a large variety of sedimentary structures (e.g., ripple marks, planar laminations and cross beddings). In this study, we investigate the sediments and the fossil assemblages to record the palaeoenvironmental evolution of the shallow marine environment during the late Miocene, in terms of sea level change, chemostratigraphy and sedimentation rate. The study area is one of the best in terms of accessibility, extension, abundance and preservation of fossils; it is located in the region -'Bukit Ambug' (Ambug Hill), Tutong District. The fossils fauna collected encompasses mollusks, decapods, otoliths, shark and ray teeth, amber, foraminifera and coccolithophorids. In this investigation, sediment samples were taken along a section which measures 62.5 meters. A thick clay layer of 9 meters was sampled each 30 cm to investigate microfossils occurrences. Each sample was treated in peroxide and then sieved trough 63 μm, 150μm, 250μm, 450μm, 600μm, 1mm and 2mm sieves. Results point on the changes in biodiversity of foraminifera along the different horizons collected reflecting sea level changes and sediment production. The most abundant taxa identified are Pseoudorotalia schroeteriana, Ampistegina lessonii, Elphidium advenum, Quinqueloculina sp., Bolivina sp

  12. Assessing SfM-Photogrammetry potential at micro-scale on a rapidly evolving mud-bank: case study on a mesocosm study within pioneer mangroves in French Guiana (South America)

    Science.gov (United States)

    Fleury, Jules; Brunier, Guillaume; Michaud, Emma; Anthony, Edward; Dussouillez, Philippe; Morvan, Sylvain

    2016-04-01

    Mud banks are the loci of rich bio-geo-chemical processes occuring rapidly at infra-tide frequency. Their surface topography is commonly affected by many of these processes, including bioturbation, water drainage or dessication. Quantifying surface morphology and changes on a mud bank at the micro-scale is a challenging task due to a number of issues. First, the water-saturated nature of the soil makes it difficult to measure High Resolution Topography (HRT) with classical methods. Second, setting up an instrumented experiment without disrupting the signal being studied is hardly achieved at micro-scale. Finally, the highly mobile nature of this environment enhancing strong spatio-temporal heterogeneity is hard to capture. Terrestrial Laser Scanning (TLS) and SfM (Surface from Motion)-Photogrammetry are two techniques that enable mapping of micro-scale features, but the first technique is not suitable because of the poor quality of the backscattered laser signal on wet surfaces and the need to set up several measuring stations on a complex, unstable substrate. Thus, we set up an experiment to assess the feasibility and the accuracy of SfM in such a context. We took the opportunity of the installation of a pontoon dedicated to the study of bio-geochemical processes within benthic mesocosms installed on a mud bank inhabited by pioneer mangroves trees to develop an adapted photogrammetry protocol based on a full-frame remotely triggered camera sensor mounted on a pole. The incident light on the surface was also controlled with a light-diffusing device. We obtained sub-millimetric resolution 3D-topography and visible imagery. Surveys were carried out every 2 hours at low tide to detect surface changes due to water content variation as well as bioturbation mainly caused by crabs digging galleries and feeding on sediment surface. Both the qualitative and quantitative results seem very promising and lead us to expect new insights into heterogeneous surface processes on a

  13. An experimental approach for archeological soil micromorphology: building a model for site taphonomy in coastal shell middens of the Beagle Channel (Argentina)

    Science.gov (United States)

    Balbo, Andrea; Suarez Villagran, Ximena; Madella, Marco; Vila, Asumpcio; Estevez, Jordi

    2010-05-01

    component of the Tunel VII archaeological site, combusted in a muffle furnace at temperatures from 200 to 800° C. The original archaeological samples from Tunel VII included resin-consolidat columns taken from vaious profiles within the shell midden site. The thin sections analysed here were taken from a profile dug through a passageway that crosses the shell dumping area. The experimental reference collection showed the intense bioturbation of both exposed and buried surfaces, despite the low temperatures that characterize the area, commonly associated to inhibition of biological activity. The same intense bioturbation was observed in the shell midden, were a form of anthrosol develops during abandonment periods of the site. The experimental samples of Mytilus edulis served as reference for identification of burning temperatures reached by the anthropic fires and were useful aids to identify reworked burnt layers as accretion material for the shell midden.

  14. Lower Eocene alluvial paleosols (Willwood Formation, Northwest Wyoming, U.S.A.) and their significance for paleoecology, paleoclimatology, and basin analysis

    Science.gov (United States)

    Bown, T.M.; Kraus, M.J.

    1981-01-01

    The lower Eocene Willwood Formation of northwest Wyoming is a 700 m thick accumulation of alluvial floodplain and channel mudstones and sandstones, nearly all of which show paleopedogenic modifications. Pedogenesis of Willwood sandstones is indicated by taproot and vertebrate and invertebrate bioturbation, early local cementation by calcium carbonate, and thin illuviation cutans on clastic grains. Pedogenesis in Willwood mudstones is indicated by plant bioturbation, insect and other invertebrate burrow casts and lebensspuren; free iron, aluminum, and manganese mobilization, including hydromorphic gleying; sesquioxide and calcareous glaebule formation in lower parts of the solum; presence of clay-rich and organic carbon-rich zones; and well differentiated epipedons and albic and spodic horizons. Probable A horizons are also locally well developed. Occurrence of variegated paleosol units in thick floodplain mudstone deposits and their association with thin, lenticular, and unconnected fluvial sandstones in the Willwood Formation of the central and southeast Bighorn Basin suggest that these soils formed during times of rapid sediment accumulation. The tabular geometry and lateral persistence of soil units as well as the absence of catenization indicate that Willwood floodplains were broad and essentially featureless. All Willwood paleosols were developed on alluvial parent materials and are complex in that B horizons of younger paleosols were commonly superimposed upon and mask properties of suspected A and B horizons of the next older paleosols. The soils appear to be wet varieties of the Spodosol and Entisol groups (aquods and ferrods, and aquents, respectively), though thick, superposed and less mottled red, purple, and yellow paleosols resemble some ultisols. Most Willwood paleosols resemble warm temperate to subtropical alluvial soils that form today under alternating wet and dry conditions and (or) fluctuating water tables. The up-section decrease in frequency

  15. Storm Bed Imprinting on the Northern California Shelf: Interaction of Fluvial and Marine Processes.

    Science.gov (United States)

    Swift, D. J.; Fan, S.; Niedoroda, A. W.; Reed, C.; Borgeld, J. C.; Crockett, J. S.

    2001-05-01

    Seismic records and cores from ONR's STRATAFORM program indicate that the Holocene deposits on the northern California shelf consist of a succession of back-stepping, storm-generated event beds, deposited as sediment undergoes cross-shelf dispersal from intermittently flooding river mouths. The beds are modified to varying degrees by secondary processes (gravity transport, bioturbation). Box core observations show that there is "mud line" on the shelf surface at approximately the 45 m isobath. Long cores show that within the 3-dimensional sediment body, nearshore sand beds intertongue with offshore mud beds beneath this line. However, numerical simulations suggest a more complex relationship. Instead of intertonguing, most event beds begin as sand beds in the nearshore sand deposit, pass through an interbedded zone, and enter the offshore mud deposit as mud beds. Event stratification is difficult to discern both seaward and landward of the transitional zone, mainly because the Cutoff Percentage has been exceeded in these areas (percent thickness of an upward-fining bed which must be preserved to observe grain size contrast). There are thus three facies bodies present, an Amalgamated Sand Facies on the inner shelf (sand beds on sand beds), an Interbedded Sand and Mud Facies on the central shelf, and an offshore Laminated or Bioturbated Mud Facies. Several other parameters are useful for defining these facies. The degree of condensation (extent to which each bed has cannibalized its predecessor) can be measured by the Reworking Ratio (ratio of mean annual resuspension depth to deposition per event). This value decreases seaward across the shelf to a minimum in the Interbedded Facies in response to decreasing wave energy flux into the sea floor. It then increases seaward across the outer shelf, as the decrease in available sediment becomes more important. The standard deviation of bed thickness is (in part) a measure of variation in storm intensity, and is a

  16. Snow vole (Chionomys nivalis Martins) affects the redistribution of soil organic matter and hormone-like activity in the alpine ecosystem: ecological implications.

    Science.gov (United States)

    Pizzeghello, Diego; Cocco, Stefania; Francioso, Ornella; Ferrari, Erika; Cardinali, Alessandra; Nardi, Serenella; Agnelli, Alberto; Corti, Giuseppe

    2015-10-01

    In alpine environments, colonies of snow vole (Chionomys nivalis Martins) cause strong pedoturbation, which may affect humification process and soil organic matter (SOM) cycling, with repercussions on the hormone-like activity of organics. We investigated the effect of snow vole pedoturbation on the chemical and spectroscopic features of soil organic fractions, and the potential hormone-like activity of humic and fulvic acids (HA, FA). The study site was located on the high-mountain environment of the Majella massif (central Italy). Pedoturbated and regular soils were morphologically described and characterized for pH and content of total organic carbon, total extractable carbon, HA, and FA. Both HA and FA were extracted and investigated using attenuated total reflectance/Fourier transform infrared (ATR/FTIR), nuclear magnetic resonance with high-resolution magic angle spinning (HRMAS-NMR), and (1)H-(13)C heteronuclear single quantum coherence (HSQC). HA and FA were also tested for their auxin-like and gibberellin-like activities. Results provide evidences that bioturbated and regular soils contain a poorly decomposed SOM, but HA and FA with a well-defined molecular structure. The HA and FA from both bioturbated and regular soils show a hormone-like activity with a different allocation along the soil profile. In the regular soil, the highest auxin-like activity was shown by HA and FA from Oe1 horizon, while gibberellin-like activity was expressed by FA from Oe2 horizon. Burrowing activity determines a redistribution of organics throughout the profile with a relatively high auxin-like activity in the FA from straw tunnel wall (STW) and gibberellin-like activity in the HA from vole feces (VF). The relative high presence of carboxylic acids, amides, proteins, and amino acids in the FA from STW and the aromatic moieties in the HA from VF put evidences for their different behavior. The fact that snow vole activity has modified the chemical and biological properties of

  17. Spilled oil and infaunal activity - Modification of burrowing behavior and redistribution of oil

    Science.gov (United States)

    Clifton, H.E.; Kvenvolden, K.A.; Rapp, J.B.

    1984-01-01

    A series of experiments in Willapa Bay, Washington, indicates the degree to which the presence of spilled oil modifies the burrowing behavior of infauna and the extent to which the animals redistribute oil into intertidal sediment. Small amounts of North Slope crude oil introduced at low tide directly into burrow openings (mostly made by the crustacean Callianassa) resulted in a limited and temporary reduction in the number of burrow openings. In contrast, a layer of oil-saturated sand 1 cm thick buried about 5 cm below the sediment surface sharply reduced the number of burrow openings. After a year, the few new burrows penetrated only the margins of the experimental plot, and bioturbation below the buried oil-saturated sand layer declined dramatically. The experiments suggest that small amounts of oil temporarily stranded by tides in themselves have no long-range effect on burrowing behavior. The fauna, however, are capable of introducing measurable amounts of oil into the subsurface, where it is retained long after the rest of the stranded oil had washed away. A buried layer of oil-saturated sand greatly reduces infaunal activity; the oil presents an effective barrier that can persist for years. The oil incorporated into the sediment from burrow openings showed evidence of degradation after 7 months. In contrast the layer of buried oil remained essentially undergraded after a period of two years, even though oil in lower concentrations above the layer was degraded after a period of one year. This variation in degree of degradation of the buried oil, as well as the heterogeneity of oil distribution wherever the oil has been incorporated from the surface, emphasises the importance of careful sampling in any attempt to locate or monitor the presence of spilled oil in the substrate.In a series of experiments in Willapa Bay, Washington, small amounts of North Slope crude oil introduced at low tide directly into burrow openings resulted in a limited and temporary

  18. Salt Marsh Sediment Mixing Following Petroleum Hydrocarbon Exposure from the Deepwater Horizon Oil Spill

    Science.gov (United States)

    Hatch, R. S.; Yeager, K. M.; Brunner, C. A.; Wade, T. L.; Briggs, K. B.; Schindler, K. J.

    2013-12-01

    Tidal marshes support valuable ecosystems, but their coastal locations make them susceptible to oil spills. Oil spilled in the ocean is easily transported via tidal and wind-driven currents to the shore and incorporated into sediments. The primary goal of this research was to determine how deeply oil from the 2010 Deepwater Horizon spill has penetrated sediments along the Gulf Coast, and whether oil has quantifiably affected benthic ecosystems at these sites. Sediment cores were taken from three marsh environments at sites classified as unoiled, lightly oiled, and heavily oiled based on data from NOAA's Environmental Response Management Application (ERMA). These classifications have been verified by measurements of total polycyclic aromatic hydrocarbons ([TPAH] without perylene). Bioturbators, such as polychaetes and oligochaetes, constantly rework sediments as they burrow into them. In this way, bioturbators can play a role in the fate of organic contaminants, either by allowing for natural remediation of contaminants via enhanced microbial degradation, or by mixing oil from the surface deeper into the sediment column. The constant fallout radionuclide 7Be was measured to determine short-term sediment mixing depths. However, there was a conspicuous absence of 7Be at most sites. This could be due to sediment composition constraints on 7Be sorption (coarse-grained sediment, high organic matter contents), or rapid erosion of the marsh surface. Instead, minimum mixing depths were derived from 234Thxs profiles. Thorium-234 is a lithogenic isotope that has widely been used to trace particle mixing on short time scales near that of its mean life (36 days). Penetration depths of 234Thxs ranged between 0.25 and 4.5 cm. Sediment accumulation rates will be determined using 210Pb, with verification from an independent tracer, 137Cs, in selected cores. Preliminary results from 210Pb profiles reveal thorough, long-term (decadal) sediment mixing to at least 40 cm at all sites

  19. Char BC amendments for soil and sediment amelioration: BC quantification and field pilot trials

    Science.gov (United States)

    Cornelissen, G.; Braendli, R. C.; Eek, E.; Henriksen, T.; Hartnik, T.; Breedveld, G. D.

    2008-12-01

    sediment by bioturbation), chemical monitoring (porewater concentrations, diffusive transport to water and air) and biological monitoring (biodiversity, bioaccumulation). The first results indicate that i) bioturbation mixes BC into the top 5 cm of the sediments, ii) 6 months after BC amendment, PAH leaching from soils is reduced by a factor of 2, iii) Hg leaching from sediments is reduced, iv) diffusive transport from sediment to water is reduced, and v) sediment biodiversity remains unaffected by the placement of a thin BC layer.

  20. Modeling the vertical soil organic matter profile using Bayesian parameter estimation

    Directory of Open Access Journals (Sweden)

    M. C. Braakhekke

    2012-08-01

    Full Text Available The vertical distribution of soil organic matter (SOM in the profile may constitute a significant factor for soil carbon cycling. However, the formation of the SOM profile is currently poorly understood due to equifinality, caused by the entanglement of several processes: input from roots, mixing due to bioturbation, and organic matter leaching. In this study we quantified the contribution of these three processes using Bayesian parameter estimation for the mechanistic SOM profile model SOMPROF. Based on organic carbon measurements, 13 parameters related to decomposition and transport of organic matter were estimated for two temperature forest soils: an Arenosol with a mor humus form (Loobos, The Netherlands, and a Cambisol with mull type humus (Hainich, Germany. Furthermore, the use of the radioisotope 210Pbex as tracer for vertical SOM transport was studied.

    For Loobos the calibration results demonstrate the importance of liquid phase transport for shaping the vertical SOM profile, while the effects of bioturbation are generally negligible. These results are in good agreement with expectations given in situ conditions. For Hainich the calibration offered three distinct explanations for the observations (three modes in the posterior distribution. With the addition of 210Pbex data and prior knowledge, as well as additional information about in situ conditions, we were able to identify the most likely explanation, which identified root litter input as the dominant process for the SOM profile. For both sites the organic matter appears to comprise mainly adsorbed but potentially leachable material, pointing to the importance of organo-mineral interactions. Furthermore, organic matter in the mineral soil appears to be mainly derived from root litter, supporting previous studies that highlighted the importance of root input for soil carbon sequestration. The 210

  1. Modeling the vertical soil organic matter profile using Bayesian parameter estimation

    Directory of Open Access Journals (Sweden)

    M. C. Braakhekke

    2013-01-01

    Full Text Available The vertical distribution of soil organic matter (SOM in the profile may constitute an important factor for soil carbon cycling. However, the formation of the SOM profile is currently poorly understood due to equifinality, caused by the entanglement of several processes: input from roots, mixing due to bioturbation, and organic matter leaching. In this study we quantified the contribution of these three processes using Bayesian parameter estimation for the mechanistic SOM profile model SOMPROF. Based on organic carbon measurements, 13 parameters related to decomposition and transport of organic matter were estimated for two temperate forest soils: an Arenosol with a mor humus form (Loobos, the Netherlands, and a Cambisol with mull-type humus (Hainich, Germany. Furthermore, the use of the radioisotope 210Pbex as tracer for vertical SOM transport was studied. For Loobos, the calibration results demonstrate the importance of organic matter transport with the liquid phase for shaping the vertical SOM profile, while the effects of bioturbation are generally negligible. These results are in good agreement with expectations given in situ conditions. For Hainich, the calibration offered three distinct explanations for the observations (three modes in the posterior distribution. With the addition of 210Pbex data and prior knowledge, as well as additional information about in situ conditions, we were able to identify the most likely explanation, which indicated that root litter input is a dominant process for the SOM profile. For both sites the organic matter appears to comprise mainly adsorbed but potentially leachable material, pointing to the importance of organo-mineral interactions. Furthermore, organic matter in the mineral soil appears to be mainly derived from root litter, supporting previous studies that highlighted the importance of root input for soil carbon sequestration. The 210

  2. Be2D: A model to understand the distribution of meteoric 10Be in soilscapes

    Science.gov (United States)

    Campforts, Benjamin; Vanacker, Veerle; Vanderborght, Jan; Govers, Gerard

    2016-04-01

    Cosmogenic nuclides have revolutionised our understanding of earth surface process rates. They have become one of the standard tools to quantify soil production by weathering, soil redistribution and erosion. Especially Beryllium-10 has gained much attention due to its long half-live and propensity to be relatively conservative in the landscape. The latter makes 10Be an excellent tool to assess denudation rates over the last 1000 to 100 × 103 years, bridging the anthropogenic and geological time scale. Nevertheless, the mobility of meteoric 10Be in soil systems makes translation of meteoric 10Be inventories into erosion and deposition rates difficult. Here we present a coupled soil hillslope model, Be2D, that is applied to synthetic and real topography to address the following three research questions. (i) What is the influence of vertical meteoric Be10 mobility, caused by chemical mobility, clay translocation and bioturbation, on its lateral redistribution over the soilscape, (ii) How does vertical mobility influence erosion rates and soil residence times inferred from meteoric 10Be inventories and (iii) To what extent can a tracer with a half-life of 1.36 Myr be used to distinguish between natural and human-disturbed soil redistribution rates? The model architecture of Be2D is designed to answer these research questions. Be2D is a dynamic model including physical processes such as soil formation, physical weathering, clay migration, bioturbation, creep, overland flow and tillage erosion. Pathways of meteoric 10Be mobility are simulated using a two step approach which is updated each timestep. First, advective and diffusive mobility of meteoric 10Be is simulated within the soil profile and second, lateral redistribution because of lateral soil fluxes is calculated. The performance and functionality of the model is demonstrated through a number of synthetic and real model runs using existing datasets of meteoric 10Be from case-studies in southeastern US. Brute

  3. Contrasting styles of deep-marine pyroclastic eruptions revealed from Axial Seamount push core records

    Science.gov (United States)

    Portner, Ryan A.; Clague, David A.; Helo, Christoph; Dreyer, Brian M.; Paduan, Jennifer B.

    2015-08-01

    A comprehensive understanding of explosive basaltic eruption processes in the deep-sea relies upon detailed analysis and comparison of the variety of volcaniclastic lithologies on the seafloor, which has been challenged by insufficient sample recovery. A dedicated ROV-based sampling approach using long push cores offers an unparalleled opportunity to fully characterize the diversity of unconsolidated volcaniclastic lithofacies on a recently active seamount. Lithofacies from Axial Seamount record two styles of pyroclastic eruptions, strombolian and phreatomagmatic, at 1.5 km water depth. Strombolian eruptions are represented by abundant fluidal and highly vesicular (up to 50%) vitriclasts within limu o Pele lapilli tuff and tuffaceous mud lithofacies. Lapilli-ash grain size, normal grading, good sorting, rip-up clasts and homogeneous glass geochemistry characterize individual limu o Pele lapilli tuff beds, and imply proximal deposition from a turbidity flow associated with a single eruption (i.e. event bed). Limu o Pele lapilli tuff beds are interbedded with poorly sorted, chemically heterogeneous and bioturbated tuffaceous mud units that preserve reworking and biologic habitation of more distal pyroclastic fallout and dilute turbidity flows. The phreatomagmatic eruption style is preserved by hydrothermal mineral-bearing muddy tuff that exhibits characteristics distinct from lapilli ash and tuffaceous mud lithofacies. Hydrothermal muddy tuff lithofacies are well-sorted and fine-grained with notable components of non-fluidal basaltic ash (∼45%), fluidal ash (∼30%) and accessory lithics (∼25%). Heterogeneous geochemistry of ash shards implies that juvenile components are minimal. The abundance, mineralogy and texture of lithic components (Fe-Mg clays, pyrite, epidote, actinolite, altered glass, basalt/diabase, hydrothermal breccia and agglutinate), and very fine-grain size of basaltic ash, are consistent with phreatomagmatic eruption deposits. A lack of

  4. Preface and brief synthesis for the FOODBANCS volume

    Science.gov (United States)

    Smith, Craig R.; DeMaster, David J.

    2008-11-01

    In this volume we present results from the FOODBANCS Project, which examined the fate and benthic community impact of summer bloom material on the West Antarctic Peninsula shelf floor. The project involved a 5-cruise, 15-month time-series program in which sediment-trap moorings, core sampling, radiochemical profiling, sediment respirometry, bottom photography, and bottom trawling were used to evaluate: (1) seafloor deposition and lability of POC, (2) patterns of labile POC consumption and sediment mixing by benthos, and (3) seasonal and inter-annual variations in biotic abundance, biomass, reproductive condition, recruitment, and sediment community respiration. We find that the seafloor flux and accumulation of particulate organic carbon on the West Antarctic Peninsula shelf exhibit intense seasonal and interannual variability. Nonetheless, many key benthic processes, including organic-matter degradation, bioturbation, deposit feeding, and faunal abundance, reproduction and recruitment, show relatively muted response to this intense seasonal and inter-annual variability in export flux. We thus hypothesize that benthic ecosystems on the Antarctic shelf act as "low-pass" filters, and may be extremely useful in resolving the impacts of climatic change over periods of years to decades in Antarctic Peninsula region.

  5. Mineralogical, geochemical and micromorphological evaluation of the Plio-Quaternary paleosols and calcretes from Karahamzall, Ankara (Central Turkey

    Directory of Open Access Journals (Sweden)

    Küçükuysal Ceren

    2014-06-01

    Full Text Available We present the mineralogical, micromorphological, and geochemical characteristics of the paleosols and their carbonates from Karahamzall, Ankara (Central Turkey. The paleosols include calcretes of powdery to nodular forms and alternate with channel deposits. The presence of pedofeatures, such as clay cutans, floating grains, circumgranular cracks, MnO linings, secondary carbonate rims, traces of past bioturbation and remnants of root fragments are all the evidence of pedogenesis. Bw is the most common soil horizon showing subangular-angular blocky to granular or prismatic microstructures. Calcretes, on the other hand, are evaluated as semi-mature massive, nodular, tubular or powdery forms. The probable faunal and floral passages may also imply the traces of life from when these alluvial deposits were soil. The presence of early diagenetic palygorskite and dolomite together with high salinization, high calcification and low chemical index of alteration values are evidence of the formation of calcretes under arid and dry conditions. δ13C compositions of the carbonates ranging from -7.11 ‰ to -7.74 ‰ VPDB are comformable with the world pedogenic carbonates favouring the C4 vegetation; likely δ18O compositions of the carbonates are between -3.97 ‰ and -4.91 ‰ which are compatible with the paleosols formed under the influence of meteroic water in the vadose zone

  6. Recognizing magnetostratigraphy in overprinted and altered marine sediments: Challenges and solutions from IODP Site U1437

    Science.gov (United States)

    Musgrave, Robert J.; Kars, Myriam

    2016-08-01

    Core disturbance, drilling overprints, postdepositional acquisition of remanence, authigenic growth of magnetic iron sulfides, and alteration all contribute challenges to recognizing the primary magnetostratigraphy in marine sediments. We address these issues in a sequence of tuffaceous muds and volcaniclastics at International Ocean Discovery Program Site U1437 and produce the longest continuous magnetic polarity stratigraphy in the history of scientific ocean drilling. Remanence measurements were filtered to remove intervals affected by fluidization, plastic sediment disturbance, and core biscuiting. Drilling overprints are concentrated in the disturbed annulus surrounding intact core material. Bioturbation was limited to a vertical extent of at most 15 cm. Changes in sediment color, stiffness, and magnetic hysteresis all suggest that remanence was locked in within a few meters of the sediment-water interface. We did not observe any systematic offset between magnetostratigraphic and biostratigraphic datums. Authigenic growth of greigite, in response to both initial sulfate reduction in the upper 50 m of the sediment column and to deeper resupply of sulfate, has led to magnetic overprinting. Anomalous polarity artefacts, extending <5 m and occurring within about 20 m below a real polarity transition, appear to be due to a chemical remanence acquired by greigite produced during early diagenesis. Diagenetic magnetic mineral alteration resulted in the progressive loss of fine-grained magnetite, which enhanced susceptibility to drilling and postdrilling overprints and increased the resistance of these overprints to removal by conventional demagnetization. We recovered the magnetostratigraphic record from many samples with resistant overprints through low-temperature demagnetization through the Verwey transition.

  7. Attempt of absolute dating and reconstitutions of climate changes in the Caribbean Sea: multi-proxy approaches to planktonic foraminifera and fine aragonitic fraction

    International Nuclear Information System (INIS)

    Absolute dating of climate archives is essential to better understand climate mechanisms. A marine sediment core from the Caribbean Sea enriched in fine-grained aragonite (suitable to U/Th dating) has been studied for both planktonic foraminifera tests (≥150 μm) and fine fraction (≤63 μm) over the last one million years using mineralogical and geochemical approaches. This study aims at i) examining lead/lag of δ18O and radiometric ages of the different-size fractions and ii) reconstructing paleo-environment in the area. The fine fraction mineralogy is strongly influenced by glacial-interglacial sea level changes. The offset of δ18O and 14C ages between the fine and foraminifera fractions during Termination I is partly explained by a bioturbation model. Attempt of U/Th dating to Termination II and V reveals that the fine fraction contains non-radiogenic Th, which needs further analytical development. Reconstructed surface water δ18O changes suggest a decrease in surface water salinity at the end of Mid-Pleistocene Transition related to ITCZ position over the Caribbean Sea. (author)

  8. Analytical characterization of selective benthic flux components in estuarine and coastal waters

    Science.gov (United States)

    King, Jeffrey N.

    2011-01-01

    Benthic flux is the rate of flow across the bed of a water body, per unit area of bed. It is forced by component mechanisms, which interact. For example, pressure gradients across the bed, forced by tide, surface gravity waves, density gradients, bed–current interaction, turbulence, and terrestrial hydraulic gradients, drive an advective benthic flux of water and constituents between estuarine and coastal waters, and surficial aquifers. Other mechanisms also force benthic flux, such as chemical gradients, bioturbation, and dispersion. A suite of component mechanisms force a total benthic flux at any given location, where each member of the suite contributes a component benthic flux. Currently, the types and characteristics of component interactions are not fully understood. For example, components may interact linearly or nonlinearly, and the interaction may be constructive or destructive. Benthic flux is a surface water–groundwater interaction process. Its discharge component to a marine water body is referred to, in some literature, as submarine groundwater discharge. Benthic flux is important in characterizing water and constituent budgets of estuarine and coastal systems. Analytical models to characterize selective benthic flux components are reviewed. Specifically, these mechanisms are for the component associated with the groundwater tidal prism, and forced by surface gravity wave setup, surface gravity waves on a plane bed, and the terrestrial hydraulic gradient. Analytical models are applied to the Indian River Lagoon, Florida; Great South Bay, New York; and the South Atlantic Bight in South Carolina and portions of North Carolina.

  9. Depositional variability of estuarine intertidal sediments and implications for metal distribution: An example from Moreton Bay (Australia)

    Science.gov (United States)

    Morelli, Guia; Gasparon, Massimo

    2015-10-01

    This study examines the patterns of depositional variability, sediment geochemistry and metal distribution in intertidal areas of Moreton Bay, southeast Queensland, Australia. Recent concern over increasing human impact on the bay has generated the need to obtain evidence on how the disturbance of the depositional setting might affect the natural estuarine environment. Sediment stratigraphy, major, and trace element analyses of sediment cores show that the sedimentation pattern is unique to each intertidal site. Disturbed 210Pb and 137Cs activity profiles of some of the cores indicate that sediment reworking occurs across the intertidal flats up to a depth of at least 80 cm. With some notable exceptions, an accurate geochronology of the surface sediments could not be established due to low 210Pb activities and sediment mixing. Thus, an increase in Pb, Zn and Cu towards the surface sediments observed at various sites is attributed to both anthropogenic contribution following the rapid urban development in the last century and to post-depositional diagenetic processes, bioturbation and sediment re-suspension induced by tides, storms or floods. Sediment cores are representative only of the local sedimentation and may not always allow extensive correlation to larger areas. Vertical profiles of heavy metals reflect the different depositional environment controlled by the complex hydrodynamics of the bay. Local hydrologic, physical, and tidal conditions might induce metals redistribution at different scales. This information is of critical importance in view of sediment remobilization caused by future development such as dredging, intertidal areas reclamation or excavation of new navigational channels.

  10. BURROW ARCHITECTURE OF RED GHOST CRAB OCYPODE MACROCERA (H. MILNE-EDWARDS, 1852 : A CASE STUDY IN INDIAN SUNDARBANS

    Directory of Open Access Journals (Sweden)

    Sourabh Kumar Dubey

    2013-12-01

    Full Text Available A study on burrow architecture and burrow morphology of the red ghost crab (Ocypode macrocera was carried out at the southern proximity of the Sagar island (21°37.973' N, to E 88° 04.195', western sector of Indian Sundarbans that faces the regular tidal influences of Bay of Bengal. Ocypode macrocera constructs burrows that are highly species specific and used by single individual. Four types of burrow patterns were observed like ‘I’, ‘J’ ‘U’ and ‘semi-U’ type with different sizes as revealed by POP casting. Important physic-chemical parameters like air temperature, temperature and salinity of the water were significantly varied (P < 0.05 throughout seasons in the Ocypode zone. Burrow sand column temperature were also significantly varied from ambient air temperature thus exhibiting preference for cooler subterranean residential compartment. The digging behaviour of Ocypodes enhances oxygenation in the ground soil and facilitates decomposition of organic materials, nutrient recycling, entrapping the sediments and mangrove seedlings and helps the process of bioturbation. As per the preliminary observations it was suggested that burrow shape is directly related to tidal action and metabolic activities of the crab are strongly correlated with burrow microenvironment. They are adapted to the different sediment conditions, tidal fluctuations, varying salinity gradients, air and water temperatures and other environmental fluctuations.

  11. Quantification of the inevitable: the influence of soil macrofauna on soil water movement in rehabilitated open-cut mined lands

    Science.gov (United States)

    Arnold, S.; Williams, E. R.

    2016-01-01

    Recolonisation of soil by macrofauna (especially ants, termites and earthworms) in rehabilitated open-cut mine sites is inevitable and, in terms of habitat restoration and function, typically of great value. In these highly disturbed landscapes, soil invertebrates play a major role in soil development (macropore configuration, nutrient cycling, bioturbation, etc.) and can influence hydrological processes such as infiltration, seepage, runoff generation and soil erosion. Understanding and quantifying these ecosystem processes is important in rehabilitation design, establishment and subsequent management to ensure progress to the desired end goal, especially in waste cover systems designed to prevent water reaching and transporting underlying hazardous waste materials. However, the soil macrofauna is typically overlooked during hydrological modelling, possibly due to uncertainties on the extent of their influence, which can lead to failure of waste cover systems or rehabilitation activities. We propose that scientific experiments under controlled conditions and field trials on post-mining lands are required to quantify (i) macrofauna-soil structure interactions, (ii) functional dynamics of macrofauna taxa, and (iii) their effects on macrofauna and soil development over time. Such knowledge would provide crucial information for soil water models, which would increase confidence in mine waste cover design recommendations and eventually lead to higher likelihood of rehabilitation success of open-cut mining land.

  12. Metal partitioning and availability in estuarine surface sediments: Changes promoted by feeding activity of Scrobicularia plana and Liza ramada

    Science.gov (United States)

    Pedro, Sílvia; Duarte, Bernardo; Reis, Givaldo; Pereira, Eduarda; Duarte, Armando C.; Costa, José Lino; Caçador, Isabel; Almeida, Pedro Raposo de

    2015-12-01

    Several works have evidenced in the past the importance and influence of plants and terrestrial invertebrates in metal availability in soils and sediments through changes in metal speciation. In contrast, the impact of estuarine invertebrates and fishes in this process has been poorly explored. The partition of metals in estuarine surface sediments was studied in a controlled environment according to four operationally defined fractions. Sediments were analyzed before and after the passage through the gut of two detritivorous species. Scrobicularia plana feeds on the bottom and suspended sediment particles through the inhalant siphon. Liza ramada is an interface feeder, filtering the superficial layer of the sediment and suspended particles in the water column. Cd, Cu and Ni bound to carbonates increased in the pellets of S. plana, compared with the ingested sediment, as did exchangeable Zn. Similarly, Cd and Zn bound to carbonates have also increased in the pellets of L. ramada; on the contrary, a decrease of Ni was observable in the pellets of this fish. The outcome of the controlled experiments pointed to a potential increase in some metals' availability in the estuarine environment, as a result of the more mobile metal forms in the excreted fecal pellets. This draws the attention to a relevant impact of the trophic activity of both species, alongside with the potential enhancement brought to it by the bioturbation promoted by them, in the role that the estuary itself has as a contaminants' buffer.

  13. Diversity and taphonomic gradients from shoreface to deep water: Case studies based on sea urchin assemblages from the Miocene of Sardinia

    Science.gov (United States)

    Nebelsick, James; Mancosu, Andrea

    2016-04-01

    Echinoid faunas from Miocene sediments from Sardinia allow diversity to be correlated to variations in depositional environments as well as taphonomic pathways. Taxonomic richness and preservation potentials vary among both carbonate and siliciclastic dominated shelf environments. Studies include detailed investigation of stratigraphy, sedimentology, palaeontology and taphonomy in both the field and in the laboratory. Environmental Interpretations are based on composition and diversity of taxa, functional morphological interpretation of life habits as well as taphonomic signatures. These investigations have revealed: 1) various mass accumulations of clypeasteroid echinoids ranging from autochthonous assemblages to multiple in situ reworked accumulations in shore face environments, 2) the distribution of morphotypes of the common genus Clypeaster, 3) echinoid assemblages dominated by both irregular and regular echinoids in siliciclastic and carbonate shelf environments, 4) spatangoid assemblages in heavily bioturbated coarse sands, and 5) monotypic shell beds of well-preserved regular echinoids and spatangoid from deeper siliciclastic environments. Variations in the diversity of echinoid taxa are correlated to biotic and abiotic ecological factors in specific depositional environments. Preservation potentials vary highly as determined by ambient environmental conditions and skeletal architectures. A synthesis of faunal diversities and preservation potentials along shelf gradient ranging from shoreface to deep water is presented.

  14. Anatomy of a phylloid algal buildup, Raytown Limestone, Iola Formation, Pennsylvanian, Southeast Kansas, U.S.A.

    Science.gov (United States)

    Dawson, William C.; Carozzi, Albert V.

    1986-05-01

    Quantitative petrography and temporal-spatial relationships of microfacies were used to interpret the depositional history of Iola carbonates. The Paola Limestone, consisting of four microfacies, was deposited on a carbonate ramp and appears to record the maximum transgression within the Iola cycle of deposition. The overlying Raytown Limestone was composed of nineteen microfacies arranged in three vertically successive depositional models of similar general configuration. These models revealed an initial bioclastic bar evolving upward into a complex bioaccumulated-bioconstructed phylloid algal buildup. The latter was replaced landward by a siliciclastic distal deltaic environment and graded basinward into upper ramp and lower ramp carbonates. Locally, restricted circulation caused the development of hypersaline conditions. The shallowing-upward depositional evolution of the phylloid algal buildup consisted of four distinct stages: bioclastic (hydrodynamic buildup), bioaccumulation, bioconstruction, and bioclastic (destruction in storm-dominated conditions and intermittent emergence). Diagenesis of Iola microfacies was complex and included: marine phreatic 1 (bioturbation, syneresis, micritization, micrite lithification, and hardground genesis; freshwater vadose—phreatic undersaturated 1 (dissolution of evaporites, moldic dissolution, collapse brecciation, and vadose silt infiltration); marine phreatic 2 (isopachous rim and botryoidal cementation); freshwater phreatic saturated 2 (sparite cementation, and extensive neomorphism); deep burial (anhydritization, dolomitization, stylolitization, and silicification); and late uplift (fracturation and cementation). Most of the diagenesis was microfacies specific.

  15. Interactions between sediment chemistry and frenulate pogonophores (Annelida) in the north-east Atlantic

    Science.gov (United States)

    Dando, P. R.; Southward, A. J.; Southward, E. C.; Lamont, P.; Harvey, R.

    2008-08-01

    The small frenulate pogonophores (Annelida: Pogonophora a.k.a. Siboglinidae) typically inhabit muddy sediments on the continental slope, although a few species occur near hydrothermal vents and cold seeps. We present data on the distribution and habitat characteristics of several species on the European continental shelf and slope from 48°N to 75°N and show how the animals interact with the chemistry of the sediments. The environments inhabited include: shallow (30 m), organic-rich, fjord sediments; slope sediments (1000-2200 m) and methane seeps at 330 m depth. All the species studied obtain nutrition from endosymbiotic bacteria. They take up reduced sulphur species, or in one case, methane, through the posterior parts of their tubes buried in the anoxic sediment. We conclude that most species undertake sulphide 'mining', a mechanism previously demonstrated in the bivalves Lucinoma borealis and Thyasira sarsi. These pogonophores participate in the sulphur cycle and effectively lower the sulphide content of the sediments. Our results show that the abundance of frenulate pogonophores increases with increasing sedimentation and with decreasing abundance of other benthos, particularly bioturbating organisms. The maximum sustainable carrying capacity of non-seep sediments for frenulate pogonophores is limited by the rate of sulphate reduction.

  16. Iron limitation in the Western Interior Seaway during the Late Cretaceous OAE 3 and its role in phosphorus recycling and enhanced organic matter preservation

    Science.gov (United States)

    Tessin, Allyson; Sheldon, Nathan D.; Hendy, Ingrid; Chappaz, Anthony

    2016-09-01

    The sedimentary record of the Coniacian-Santonian Oceanic Anoxic Event 3 (OAE 3) in the North American Western Interior Seaway is characterized by a prolonged period of enhanced organic carbon (OC) burial. This study investigates the role of Fe in enhancing organic matter preservation and maintaining elevated primary productivity to sustain black shale deposition within the Coniacian-Santonian-aged Niobrara Formation in the USGS #1 Portland core. Iron speciation results indicate the development of a reactive Fe limitation coeval with reduced bioturbation and increased organic matter preservation, suggesting that decreased sulfide buffering by reactive Fe may have promoted enhanced organic matter preservation at the onset of OAE 3. An Fe limitation would also provide a feedback mechanism to sustain elevated primary productivity through enhanced phosphorus recycling. Additionally our results demonstrate inconsistencies between Fe-based and trace metal redox reconstructions. Iron indices from the Portland core indicate a single stepwise change, whereas the trace metal redox proxies indicate fluctuating redox conditions during and after OAE 3. Using Fe speciation to reconstruct past redox conditions may be complicated by a number of factors, including Fe sequestration in diagenetic carbonate phases and efficient sedimentary pyrite formation in a system with limited Fe supply and high levels of export production.

  17. Diagenesis and benthic fluxes of nutrients and metals during experimentally induced anoxia in the Gulf of Trieste (northern Adriatic Sea

    Directory of Open Access Journals (Sweden)

    N. Koron

    2013-07-01

    Full Text Available Sequential nutrient regeneration and organic matter (OM degradation in surface sediments of the Gulf of Trieste (northern Adriatic Sea were examined using in situ benthic chambers under normoxic, anoxic and reoxic conditions. Intensive NH4+ and PO4− anoxic regeneration was subsequently slower in prolonged anoxia. NH4+ production was probably also a consequence of dissimilatory nitrate reduction to NH4+. The presence of anammox and laterally pumping of oxygenated water by benthic infauna explained the presence of NO3− in anoxia. Anoxic phases were characterized by enhanced dissolution of Sibiog, decreasing pore water Ca and Mg concentrations indicating carbonate precipitation and higher Fe and Mn concentrations as a result of reduction/respiration. Reoxygenation was characterized by enhanced bioturbation. Nitrification caused NH4+ decrease and P precipitated quickly as carbonate fluorapatite and FePO4. In addition adsorption of P onto Fe-hydroxides could also occur since Fe (and Mn reoxidized quickly. Increased Ca levels suggested enhanced carbonate dissolution. Diffusive fluxes at the sediment–water interface (SWI, calculated from pore water modelling using diffusion-reaction model, revealed high anoxic NH4+ effluxes and Ca (and Mg influxes. PO4− fluxes were very low and high NH4+/PO4− flux ratios in anoxic and reoxic phases suggested an excess of benthic inorganic N. Nutrient budgets at the SWI showed intensive anoxic recycling of inorganic N but low P and Si cycling in all redox phases.

  18. Mediterranean climate variability during the Holocene

    Directory of Open Access Journals (Sweden)

    J.S.L. CASFORD

    2012-12-01

    Full Text Available We present a study on four high sedimentation-rate marine cores with suppressed bioturbation effects, recovered along the northern margin of the eastern Mediterranean. We demonstrate that this region, central to the development of modern civilisation, was substantially affected throughout the Holocene by a distinct cycle of cooling events on the order of 2o C. In the best-preserved cases the onset of these events appears particularly abrupt, within less than a century. The cooling events typically lasted several centuries, and there are compelling indications that they were associated with increased aridity in the Levantine/NE African sector (Rossignol-Strick, 1995; 1998; Alley et al., 1997; Hassan, 1986; 1996; 1997a,b; McKim Malville et al., 1998. Several of these episodes appear coincident with cultural reorganisations, with indigenous developments (eg. cattle domestication, new technologies and population migrations and fusion of peoples and ideas (Hassan, 1986; 1996; 1997a,b; McKim Malville, 1998. We infer that climatic events of a likely high-latitude origin (O’Brien et al., 1995; Bond et al., 1997; Mayewski et al., 1997; Alley et al., 1997 caused cooling and aridity in and around the eastern Mediterranean via a direct atmospheric link, and therefore played an important role in the development of modern civilisation.

  19. Rooting Characteristics of Vegetation Near Areas 3 and 5 Radioactive Waste Management Sites at the Nevada Test Site--Part 1

    Energy Technology Data Exchange (ETDEWEB)

    D. J. Hansen

    2003-09-30

    The U.S. Department of Energy emplaced high-specific-activity low-level radioactive wastes and limited quantities of classified transuranic wastes in Greater Confinement Disposal (GCD) boreholes from 1984 to 1989. The boreholes are located at the Area 5 Radioactive Waste Management Site (RWMS) on the Nevada Test Site (NTS) in southern Nevada. The boreholes were backfilled with native alluvium soil. The surface of these boreholes and trenches is expected to be colonized by native vegetation in the future. Considering the long-term performance of the disposal facilities, bioturbation (the disruption of buried wastes by biota) is considered a primary release mechanism for radionuclides disposed in GCD boreholes as well as trenches at both Areas 3 and 5 RWMSs. This report provides information about rooting characteristics of vegetation near Areas 3 and 5 RWMSs. Data from this report are being used to resolve uncertainties involving parameterization of performance assessment models used to characterize the biotic mixing of soils and radionuclide transport processes by biota. The objectives of this study were to: (1) survey the prior ecological literature on the NTS and identify pertinent information about the vegetation, (2) conduct limited field studies to describe the current vegetation in the vicinity of Areas 3 and 5 RWMSs so as to correlate findings with more extensive vegetation data collected at Yucca Mountain and the NTS, ( 3 ) review prior performance assessment documents and evaluate model assumptions based on current ecological information, and (4) identify data deficiencies and make recommendations for correcting such deficiencies.

  20. Ecological effects of co-culturing the sea cucumber Apostichopus japonicus with the Chinese white shrimp Fenneropenaeus chinensis in an earthen pond

    Science.gov (United States)

    Zhou, Shun; Ren, Yichao; Pearce, Christopher M.; Dong, Shuanglin; Tian, Xiangli; Gao, Qinfeng; Wang, Fang

    2016-03-01

    Using net enclosures in an earthen pond, we established three culture treatments with the sea cucumber Apostichopus japonicus and the Chinese white shrimp Fenneropenaeus chinensis: monoculture of sea cucumbers (C), monoculture of shrimp (S), and co-culture of the two species (CS). We measured levels of suspended particulate matter in the water column; total organic matter, total organic carbon, total nitrogen, and carbon/nitrogen ratios in both settling particles and the sediment; and chlorophyll a levels in the sediment. We then compared these variables between the three treatments. We also examined growth, survival, and yield of the two species in the different treatments. From June to September, the mean monthly suspended particulate matter sedimentation rates in the CS and S treatments were significantly (Pculture were all significantly greater than those of sea cucumbers in monoculture. There were no significant differences among any of these variables for shrimp reared in the two systems. The bioturbation of the sediment and fecal production of the shrimp likely supplied natural food for the sea cucumbers. Co-culture of the two species is a viable option for increasing yield per unit area, maximizing use of the water body, and diversifying crop production.

  1. Ecosystem engineering effects on species diversity across ecosystems: a meta-analysis.

    Science.gov (United States)

    Romero, Gustavo Q; Gonçalves-Souza, Thiago; Vieira, Camila; Koricheva, Julia

    2015-08-01

    Ecosystem engineering is increasingly recognized as a relevant ecological driver of diversity and community composition. Although engineering impacts on the biota can vary from negative to positive, and from trivial to enormous, patterns and causes of variation in the magnitude of engineering effects across ecosystems and engineer types remain largely unknown. To elucidate the above patterns, we conducted a meta-analysis of 122 studies which explored effects of animal ecosystem engineers on species richness of other organisms in the community. The analysis revealed that the overall effect of ecosystem engineers on diversity is positive and corresponds to a 25% increase in species richness, indicating that ecosystem engineering is a facilitative process globally. Engineering effects were stronger in the tropics than at higher latitudes, likely because new or modified habitats provided by engineers in the tropics may help minimize competition and predation pressures on resident species. Within aquatic environments, engineering impacts were stronger in marine ecosystems (rocky shores) than in streams. In terrestrial ecosystems, engineers displayed stronger positive effects in arid environments (e.g. deserts). Ecosystem engineers that create new habitats or microhabitats had stronger effects than those that modify habitats or cause bioturbation. Invertebrate engineers and those with lower engineering persistence (1 year. Invertebrate species richness was particularly responsive to engineering impacts. This study is the first attempt to build an integrative framework of engineering effects on species diversity; it highlights the importance of considering latitude, habitat, engineering functional group, taxon and persistence of their effects in future theoretical and empirical studies.

  2. Quantification of the inevitable: the influence of soil macrofauna on soil water movement in rehabilitated open-cut mine land

    Science.gov (United States)

    Arnold, S.; Williams, E. R.

    2015-08-01

    Recolonisation of soil by macrofauna (especially ants and termites) in rehabilitated open-cut mine sites is inevitable. In these highly disturbed landscapes, soil invertebrates play a major role in soil development (macropore configuration, nutrient cycling, bioturbation, etc.) and can influence hydrological processes such as infiltration and seepage. Understanding and quantifying these ecosystem processes is important in rehabilitation design, establishment and subsequent management to ensure progress to the desired end-goal, especially in waste cover systems designed to prevent water reaching and transporting underlying hazardous waste materials. However, soil macrofauna are typically overlooked during hydrological modelling, possibly due to uncertainties on the extent of their influence, which can lead to failure of waste cover systems or rehabilitation activities. We propose that scientific experiments under controlled conditions are required to quantify (i) macrofauna - soil structure interactions, (ii) functional dynamics of macrofauna taxa, and (iii) their effects on macrofauna and soil development over time. Such knowledge would provide crucial information for soil water models, which would increase confidence in mine waste cover design recommendations and eventually lead to higher likelihood of rehabilitation success of open-cut mining land.

  3. What They Work at is not What They eat: Incongruence of Strong Interactions and Assimilation in Shrimps and Baetid Mayflies in a Brazilian Coastal Stream

    Science.gov (United States)

    Moulton, T.; de Souza, M. L.; Brito, E. F.; Krsulovic, F. M.; Silveira, R. M.; Ometto, J. B.

    2005-05-01

    Exclusion experiments showed that atyid shrimps (Potimirim glabra) and baetid mayflies (Cloeodes sp., Americabaetis sp.) removed benthic material from hard substrate at different sites in the forested stream Rio Andorinha, Ilha Grande, Rio de Janeiro. Their effects were greater on organic material not associated with algae than on algae. Macrobrachium olfersi shrimp had a negative effect on the mayflies, causing a trophic cascade with the benthic material. Gut analysis of the atyid and baetids showed that they ingested large amounts of detritus, as expected. Macrobrachium contained mainly detritus, some algae and some insect parts. Stable isotope analysis of the gut contents confirmed these compositions, but the tissue of the shrimps and mayflies was of carbon derived from algae (as testified by enriched δ 13C corresponding to microalgae from the periphyton). Baetids appeared to be algal herbivores and both Potimirim and Macrobrachium appeared (from their δ 15N signatures) to be secondary consumers. We note that what the animals remove (both by bioturbation and ingestion) and what they assimilate are very different. We speculate that the baetids and atyid are "gardeners" and remove material to promote the growth of algal turf.

  4. Influence of biological activity on sorption by using {sup 65}Zn and {sup 109}Cd into mangrove sediment

    Energy Technology Data Exchange (ETDEWEB)

    Sondermann, Melissa N.; Barros, Joanna F.; Suzuki, Katia N.; Bellido, Alfredo V.B., E-mail: melissa.sonder@gmail.com, E-mail: joanna_barros2@hotmail.com, E-mail: ksuzuki@id.uff.br, E-mail: alfredobellido@gmail.com [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Instituto de Quimica. Pos-Graduacao em Geoquimica Ambiental; Bellido, Luis F., E-mail: lbellido@cnen.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Lopes, Ricardo T., E-mail: ricardo@lin.ufrj.br [Coordenacao dos Programas de Pos-Graduacao em Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil)

    2015-07-01

    Evaluation of the chemical behavior of zinc and cadmium as well as the influence of biological activity in the sorption kinetics under microcosm experiments by mangrove sediments collected in Sepetiba Bay - Rio de Janeiro was carried out. The mentioned area was well contaminated due to the leaching from the tailing pile by the abandoned zinc processing company Inga Mercantil. Radiotracer {sup 65}Zn and {sup 109}Cd were used to follow their exchange across water-sediment interfaces up to 48 hours experiments in six mangrove sediment cores. To determine the benthic activity index (BAI) the cores were treated with formaldehyde (biocide) and it was found that the presence of the radiotracers in the deeper layers of sediment without formaldehyde treatment showed clearly the influence of benthic activity retention (benthic faunal and microbial effects), since the same pattern was not found in the treated sediment. The activity values obtained for {sup 65}Zn and {sup 109}Cd in the untreated sediment with formaldehyde on the first centimeter were 53.79±0.28 % and 67.34±0.16 % respectively, whereas for the treated ones, were 98.72 ± 0.29 % and 98.31 ± 0.24 % respectively. Thus, it was demonstrated that the use of formaldehyde, as biological activity inhibitor, ceases the bioturbation process and allowed the accumulation along the sediment. (author)

  5. The Anthropocene: a conspicuous stratigraphical signal of anthropogenic changes in production and consumption across the biosphere

    Science.gov (United States)

    Williams, Mark; Zalasiewicz, Jan; Waters, Colin N.; Edgeworth, Matt; Bennett, Carys; Barnosky, Anthony D.; Ellis, Erle C.; Ellis, Michael A.; Cearreta, Alejandro; Haff, Peter K.; Ivar do Sul, Juliana A.; Leinfelder, Reinhold; McNeill, John R.; Odada, Eric; Oreskes, Naomi; Revkin, Andrew; Richter, Daniel deB; Steffen, Will; Summerhayes, Colin; Syvitski, James P.; Vidas, Davor; Wagreich, Michael; Wing, Scott L.; Wolfe, Alexander P.; Zhisheng, An

    2016-03-01

    Biospheric relationships between production and consumption of biomass have been resilient to changes in the Earth system over billions of years. This relationship has increased in its complexity, from localized ecosystems predicated on anaerobic microbial production and consumption to a global biosphere founded on primary production from oxygenic photoautotrophs, through the evolution of Eukarya, metazoans, and the complexly networked ecosystems of microbes, animals, fungi, and plants that characterize the Phanerozoic Eon (the last ˜541 million years of Earth history). At present, one species, Homo sapiens, is refashioning this relationship between consumption and production in the biosphere with unknown consequences. This has left a distinctive stratigraphy of the production and consumption of biomass, of natural resources, and of produced goods. This can be traced through stone tool technologies and geochemical signals, later unfolding into a diachronous signal of technofossils and human bioturbation across the planet, leading to stratigraphically almost isochronous signals developing by the mid-20th century. These latter signals may provide an invaluable resource for informing and constraining a formal Anthropocene chronostratigraphy, but are perhaps yet more important as tracers of a biosphere state that is characterized by a geologically unprecedented pattern of global energy flow that is now pervasively influenced and mediated by humans, and which is necessary for maintaining the complexity of modern human societies.

  6. Modeling Channelization in Coastal Wetlands with Ecological Feedbacks

    Science.gov (United States)

    Hughes, Z. J.; Mahadevan, A.; Pennings, S.; FitzGerald, D.

    2014-12-01

    In coastal wetlands in Georgia and South Carolina, dendritic channel networks are actively incising headward at the rate of nearly 2 m/yr. The future geomorphic evolution of these marshes remains in question as rates of relative sea-level rise increase. Our objective is to understand the mechanisms that lead to the evolution of these channel networks through field observations and modeling. We model the geomorphological evolution of tidal creeks by viewing the wetland as a permeable medium. The porosity of the medium affects its hydraulic conductivity, which in turn is altered by erosion. Our multiphase model spontaneously generates channelization and branching networks through flow and erosion. In our field studies, we find that crabs play an active role in grazing vegetation and in the bioturbation of sediments. These effects are incorporated in our model based on field and laboratory observations of crab behavior and its effects on the marsh. We find the erosional patterns and channelization are significantly altered by the faunal feedback. Crabs enhance the growth of channels, inducing the headward erosion of creeks where flow-induced stresses are weakest. They are instrumental in generating high rates of creek extension, which channelize the marsh more effectively in response to sea-level rise. This indicates that the evolution of coastal wetlands is responding to interactions between physics and ecology and highlights the importance of the faunal contribution to these feedbacks.

  7. The fate of terrestrial organic matter in two Scottish sea lochs

    Science.gov (United States)

    Loh, P. S.; Reeves, A. D.; Harvey, S. M.; Overnell, J.; Miller, A. E. J.

    2008-02-01

    Sea lochs are zones of rapid organic matter (OM) turnover. Most of this OM is of allochthonous origin, being introduced into the lochs via freshwater input. In this study the behaviour of terrestrially derived OM was elucidated using a combination of parameters which indicate OM diagenesis in the near surface sediments from two Scottish sea lochs, Loch Creran and Loch Etive. Alkaline CuO oxidation was used to determine lignin phenols which serve as biomarkers for terrestrial OM in sediments. Stable carbon isotope, total carbon and nitrogen and total OM (including the labile and refractory fractions) compositions were also determined. Lignin materials in the lochs were generally highly degraded and undergo little degradation further seaward. The vanillic acid to vanillin ratio, (Ad/Al)v in the lochs ranged from 0.52 to 2.69. However, there was a fraction of relatively fresh, land-derived OM, still undergoing degradation adding to the carbon cycling in the lochs, as indicated by the Rp values (ratio of refractory to total OM) and OC/N ratios in the surface sediments. The hydrological and hydrodynamic regimes in Loch Creran result in several phenomena such as the transportation of terrestrial debris via hydrodynamic sorting processes and the promotion of surface sediment diagenesis by bioturbation. Frequent water renewal results in better water circulation and oxygenation which facilitate OM decomposition. In Loch Etive the less frequent renewal gives rise to a more constant OM diagenesis along the loch.

  8. Benthic foraminiferal assemblage formation: Theory and observation for the European Arctic margin

    Science.gov (United States)

    Loubere, Paul; Rayray, Shan

    2016-09-01

    We use theory and observation to determine how benthic foraminiferal populations living in a range of sedimentary microenvironments are translated into fossil assemblages along the continental margin of the European Arctic. We examine downcore stained (cell tracker green and rose Bengal) and total species shell abundances through the sediment mixing (bioturbation) zone. This, in combination with porewater geochemical measurements, allows us to establish zones of production and destruction for species' shells, and deduce how the fossil record is being generated by the living community. For many taxa, shell production is high in the upper, oxic, sedimentary layer, but destruction in this zone is also high. Hence, contribution to the fossil record is biased to more infaunal populations and species. Taxa producing near, or below, the anoxic boundary of the sediments are particularly important to the developing fossil record of the fjord environment. We find that taxon relative and absolute abundances change continuously through the biologically active sediment profile. This has implications for reconstructing paleoenvironments using benthic foraminiferal assemblages, and potentially for the geochemistry of individual fossil taxa.

  9. Calibration and Performance of the Stirred Flux Chamber from the Benthic Lander Elinor

    DEFF Research Database (Denmark)

    GLUD, RN; GUNDERSEN, JK; REVSBECH, NP;

    1995-01-01

    Flow velocities and O-2 microgradients were measured by use of minithermistors and O-2 microelectrodes inside a laboratory model of the chamber from the benthic lander, Elinor. The sensors were introduced from below through small holes in the chamber bottom and penetrated up through the sediment.......%. Radial pressure gradients in the stirred chamber were 1-3 Pa. Such pressure gradients may induce advective pore water transport in permeable sediments and increase the flushing of animal burrows in bioturbated sediments.......Flow velocities and O-2 microgradients were measured by use of minithermistors and O-2 microelectrodes inside a laboratory model of the chamber from the benthic lander, Elinor. The sensors were introduced from below through small holes in the chamber bottom and penetrated up through the sediment....... Flow velocities and the diffusive boundary layer (DBL) could thereby be studied with a minimum of disturbance. In the central part of the chamber covering 9% of the area, the DBL was thicker and the flow rates significantly lower than in the rest of the hydrodynamically uniform chamber. Average flow...

  10. Rooting Characteristics of Vegetation near Areas 3 and 5 Radioactive Waste Management Sites at the Nevada Test Site

    International Nuclear Information System (INIS)

    The U.S. Department of Energy emplaced high-specific-activity low-level radioactive wastes and limited quantities of classified transuranic wastes in Greater Confinement Disposal (GCD) boreholes from 1984 to 1989. The boreholes are located at the Area 5 Radioactive Waste Management Site (RWMS) on the Nevada Test Site (NTS) in southern Nevada. The boreholes were backfilled with native alluvium soil. The surface of these boreholes and trenches is expected to be colonized by native vegetation in the future. Considering the long-term performance of the disposal facilities, bioturbation (the disruption of buried wastes by biota) is considered a primary release mechanism for radionuclides disposed in GCD boreholes as well as trenches at both Areas 3 and 5 RWMSs. This report provides information about rooting characteristics of vegetation near Areas 3 and 5 RWMSs. Data from this report are being used to resolve uncertainties involving parameterization of performance assessment models used to characterize the biotic mixing of soils and radionuclide transport processes by biota. The objectives of this study were to: (1) survey the prior ecological literature on the NTS and identify pertinent information about the vegetation, (2) conduct limited field studies to describe the current vegetation in the vicinity of Areas 3 and 5 RWMSs so as to correlate findings with more extensive vegetation data collected at Yucca Mountain and the NTS, (3) review prior performance assessment documents and evaluate model assumptions based on current ecological information, and (4) identify data deficiencies and make recommendations for correcting such deficiencies

  11. Rooting Characteristics of Vegetation Near Areas 3 and 5 Radioactive Waste Management Sites at the Nevada Test Site--Part 1

    International Nuclear Information System (INIS)

    The U.S. Department of Energy emplaced high-specific-activity low-level radioactive wastes and limited quantities of classified transuranic wastes in Greater Confinement Disposal (GCD) boreholes from 1984 to 1989. The boreholes are located at the Area 5 Radioactive Waste Management Site (RWMS) on the Nevada Test Site (NTS) in southern Nevada. The boreholes were backfilled with native alluvium soil. The surface of these boreholes and trenches is expected to be colonized by native vegetation in the future. Considering the long-term performance of the disposal facilities, bioturbation (the disruption of buried wastes by biota) is considered a primary release mechanism for radionuclides disposed in GCD boreholes as well as trenches at both Areas 3 and 5 RWMSs. This report provides information about rooting characteristics of vegetation near Areas 3 and 5 RWMSs. Data from this report are being used to resolve uncertainties involving parameterization of performance assessment models used to characterize the biotic mixing of soils and radionuclide transport processes by biota. The objectives of this study were to: (1) survey the prior ecological literature on the NTS and identify pertinent information about the vegetation, (2) conduct limited field studies to describe the current vegetation in the vicinity of Areas 3 and 5 RWMSs so as to correlate findings with more extensive vegetation data collected at Yucca Mountain and the NTS, ( 3 ) review prior performance assessment documents and evaluate model assumptions based on current ecological information, and (4) identify data deficiencies and make recommendations for correcting such deficiencies

  12. Active eukaryotes in microbialites from Highborne Cay, Bahamas, and Hamelin Pool (Shark Bay), Australia.

    Science.gov (United States)

    Edgcomb, Virginia P; Bernhard, Joan M; Summons, Roger E; Orsi, William; Beaudoin, David; Visscher, Pieter T

    2014-02-01

    Microbialites are organosedimentary structures that are formed through the interaction of benthic microbial communities and sediments and include mineral precipitation. These lithifying microbial mat structures include stromatolites and thrombolites. Exuma Sound in the Bahamas, and Hamelin Pool in Shark Bay, Western Australia, are two locations where significant stands of modern microbialites exist. Although prokaryotic diversity in these structures is reasonably well documented, little is known about the eukaryotic component of these communities and their potential to influence sedimentary fabrics through grazing, binding and burrowing activities. Accordingly, comparisons of eukaryotic communities in modern stromatolitic and thrombolitic mats can potentially provide insight into the coexistence of both laminated and clotted mat structures in close proximity to one another. Here we examine this possibility by comparing eukaryotic diversity based on Sanger and high-throughput pyrosequencing of small subunit ribosomal RNA (18S rRNA) genes. Analyses were based on total RNA extracts as template to minimize input from inactive or deceased organisms. Results identified diverse eukaryotic communities particularly stramenopiles, Alveolata, Metazoa, Amoebozoa and Rhizaria within different mat types at both locations, as well as abundant and diverse signatures of eukaryotes with eukaryotic diversity, particularly in hypersaline Hamelin Pool. There was evidence of vertical structuring of protist populations and foraminiferal diversity was highest in bioturbated/clotted thrombolite mats of Highborne Cay.

  13. Outer ramp cycles in the Upper Muschelkalk of the Catalan Basin, northeast Spain

    Science.gov (United States)

    Calvet, Francesc; Tucker, Maurice E.

    1988-06-01

    The Upper Muschelkalk (Triassic) of the Catalan Basin, eastern Spain, was deposited upon a carbonate ramp of homoclinal type located in an intracratonic setting. The Rasquera Unit in the Upper Muschelkalk mostly consists of outer ramp carbonates arranged in upward shallowing cycles. Five cycles from 1.5 to 12 m thick are recognised. Each cycle shows an upward coarsening of grain-size, an upward increase in bed thickness, and an upward change in fossil content, reflecting an upward shallowing of the environment. In the complete cycle, marlstone and shale pass up into marlstone with thin-bedded line mudstones containing pelagic bivalves. The succeeding thin-bedded and nodular limestones with shaley partings contain a more varied fauna and are bioturbated; they pass up into thick-bedded skeletal wackestones. Packstone-coquinas locally cap the cycles and have a diverse benthic fauna, as well as the alga Tubiphytes occurring as bioclasts, encrustations around skeletal grains and forming microbuildups. Although some of the thin beds were deposited during weak storms, there is little evidence of intense storm activity. Petrological, sedimentological and palaeontological criteria, and the geological setting, allow the recognition of distal, intermediate and proximal facies on a relatively deepwater carbonate ramp.

  14. Sediment quality and ecorisk assessment factors for a major river system

    International Nuclear Information System (INIS)

    Sediment-related water quality and risk assessment parameters for the Columbia River were developed using heavy metal loading and concentration data from Lake Roosevelt (river km 1120) to the mouth and adjacent coastal zone. Correlation of Pb, Zn, Hg, and Cd concentrations in downstream sediments with refinery operations in British Columbia suggest that solutes with Kd's > 105 reach about 1 to 5 μg/g per metric ton/year of input. A low-suspended load (upriver avg. <10 mg/L) and high particle-surface reactivity account for the high clay-fraction contaminant concentrations. In addition, a sediment exposure path was demonstrated based on analysis of post-shutdown biodynamics of a heavy metal radiotracer. The slow decline in sediment was attributed to resuspension, bioturbation, and anthropogenic disturbances. The above findings suggest that conservative sediment quality criteria should be used to restrict additional contaminant loading in the upper drainage basin. The issuance of an advisory for Lake Roosevelt, due in part to Hg accumulation in large sport fish, suggests more restrictive controls are needed. A monitoring strategy for assessing human exposure potential and the ecological health of the river is proposed

  15. Deglacial History and Paleoceanography of the Umanak System, West Greenland

    DEFF Research Database (Denmark)

    Sheldon, Christina; Jennings, Anne; Andrews, John;

    2012-01-01

    of the area. SWATH bathymetry data show that the GIS extended to the shelf edge via an ice stream in the Umanak System during the Last Glacial Maximum (LGM). Three sediment cores, located on the upper slope (VC46), outer shelf (VC45) and inner shelf (VC42) of the Umanak Trough capture the progressive retreat...... the timing of these changes. Preliminary foraminiferal assemblage analyses in context of lithofacies changes demonstrate a change from ice-proximal to ice-distal conditions across the shelf trough. Radiocarbon dates indicate that the UIS had retreated from the shelf edge by 14,880 cal kyr BP (VC45) and ice......-distal conditions were established on the mid-shelf by 11,350 cal kyr BP (VC43). By 8480 cal yr BP, the UIS had retreated from the inner shelf. Foraminiferal assemblages with distinct Atlantic Water associations are found in the bioturbated mud unit 18 cm above the glacigenic debris flow deposit in VC46...

  16. A conceptual framework for shear flow-induced erosion of soft cohesive sediment beds

    Science.gov (United States)

    Winterwerp, J. C.; van Kesteren, W. G. M.; van Prooijen, B.; Jacobs, W.

    2012-10-01

    This paper proposes a conceptual framework for erosion of cohesive sediment beds. We focus on cohesive beds, distinguishing between floc erosion, surface erosion, and mass erosion. By (our) definition, surface erosion is a drained soil mechanical process, whereas mass erosion occurs under undrained conditions. The eroding shear stress is modeled through a probability density function. This yields a continuous description of floc erosion and surface erosion as a function of mean bed shear stress. Furthermore, we assume a distribution for the bed strength. The mean values of the bed strength are derived from soil mechanical theory, assuming that the surface erosion rate is limited by the swelling rate from the undrained shear strength in the bed to its drained value at its surface. The rate of erosion then relates to the undrained shear strength of the soil, and its consolidation (swelling) coefficient. The critical shear stress for erosion is slightly larger than the true cohesion of the bed, i.e., the drained strength, and follows a power law relation with the plasticity index. The conceptual framework proposed herein has been validated against a limited number of experimental data, and has a series of advantages above other methods of direct measuring erodibility, as it is inexpensive and can be used to attain space-covering information on the sediment bed. Moreover, the use of bulk soil mechanical parameters accounts implicitly for the effects of organic material, though the role of, e.g., macrophytobenthos mats and/or bioturbation is difficult to capture a priori.

  17. Charles Darwin's Observations on the Behaviour of Earthworms and the Evolutionary History of a Giant Endemic Species from Germany, Lumbricus badensis (Oligochaeta: Lumbricidae

    Directory of Open Access Journals (Sweden)

    U. Kutschera

    2010-01-01

    Full Text Available The British naturalist Charles Darwin (1809–1882 began and ended his almost 45-year-long career with observations, experiments, and theories related to earthworms. About six months before his death, Darwin published his book on The Formation of Vegetable Mould, through the Actions of Worms, With Observations on their Habits (1881. Here we describe the origin, content, and impact of Darwin's last publication on earthworms (subclass Oligochaeta, family Lumbricidae and the role of these annelids as global “ecosystem reworkers” (concept of bioturbation. In addition, we summarize our current knowledge on the reproductive behaviour of the common European species Lumbricus terrestris. In the second part of our account we describe the biology and evolution of the giant endemic species L. badensis from south western Germany with reference to the principle of niche construction. Biogeographic studies have shown that the last common ancestor of L. badensis, and the much smaller sister-taxon, the Atlantic-Mediterranean L. friendi, lived less than 10 000 years ago. Allopatric speciation occurred via geographically isolated founder populations that were separated by the river Rhine so that today two earthworm species exist in different areas.

  18. The influence of mature oak stands and spruce plantations on soil-dwelling click beetles in lowland plantation forests.

    Science.gov (United States)

    Loskotová, Tereza; Horák, Jakub

    2016-01-01

    Most European forests have been converted into forest plantations that are managed for timber production. The main goal of this paper was to determine the difference between mature native sessile oak (Quercus petraea) stands and non-indigenous Norway spruce (Picea abies) plantations, with respect to communities of Athous click beetles in approximately 6,500 ha of lowland plantation forest area in the Czech Republic. Athous subfuscus was the most abundant and widespread species, followed by A. zebei and A. haemorrhoidalis, while A. vittatus was considered rare. Spatial analysis of environmental variables inside studied patches showed that the species composition of Athous beetles best responded to a 20 m radius surrounding traps. The species' responses to the environment showed that A. vittatus and A. haemorrhoidalis preferred oak stands, while A. zebei and A. subfuscus were associated with spruce plantations. In addition, oak stands showed higher diversity of beetle communities. The studied species are important for their ecosystem services (e.g. predation on pests or bioturbation) and seem to tolerate certain degrees of human disturbances, which is especially beneficial for forest plantations managed for timber production. PMID:26793425

  19. Changes in Sediment Fatty Acid Composition during Passage through the Gut of Deposit Feeding Holothurians: Holothuria atra (Jaeger, 1883) and Holothuria leucospilota (Brandt, 1835).

    Science.gov (United States)

    Mfilinge, Prosper L; Tsuchiya, Makoto

    2016-01-01

    Sea cucumbers Holothuria atra and Holothuria leucospilota play an important role in the bioturbation of sediment in coral reef and rocky intertidal ecosystems. This study investigated changes in sediment fatty acid (FA) composition during gut passage in H. atra and H. leucospilota. The FA composition did not differ significantly between species. Comparison of FA composition in ambient sediment (AS), foregut (FG), midgut (MG), hindgut (HG), and faecal pellets (FPs) indicated that marked changes in FA composition occurred during passage through the gut of H. atra and H. leucospilota. Saturated fatty acids (SAFAs), monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), and branched fatty acids (BrFAs) were significantly higher in FG than in AS, suggesting that both species selectively ingested nutrient rich particles. Significant reduction of SAFAs, MUFAs, PUFAs, and BrFAs occurred in MD and HD, with complete elimination of most PUFAs in FPs. A decrease in PUFAs 20:5ω3, 18:4ω3, 22:5ω3, 22:6ω3, 18:2ω6, 18:3ω3, 18:3ω6, odd-numbered BrFAs, and MUFA 18:1ω7 indicated that algal detritus and bacteria were important part of diet. These results have implications for the fate of specific dietary FAs, especially ω3 and ω6, and the contribution holothurian FPs make to the FA composition of coral reef and rocky intertidal ecosystems. PMID:27042355

  20. Changes in Sediment Fatty Acid Composition during Passage through the Gut of Deposit Feeding Holothurians: Holothuria atra (Jaeger, 1883 and Holothuria leucospilota (Brandt, 1835

    Directory of Open Access Journals (Sweden)

    Prosper L. Mfilinge

    2016-01-01

    Full Text Available Sea cucumbers Holothuria atra and Holothuria leucospilota play an important role in the bioturbation of sediment in coral reef and rocky intertidal ecosystems. This study investigated changes in sediment fatty acid (FA composition during gut passage in H. atra and H. leucospilota. The FA composition did not differ significantly between species. Comparison of FA composition in ambient sediment (AS, foregut (FG, midgut (MG, hindgut (HG, and faecal pellets (FPs indicated that marked changes in FA composition occurred during passage through the gut of H. atra and H. leucospilota. Saturated fatty acids (SAFAs, monounsaturated fatty acids (MUFAs, polyunsaturated fatty acids (PUFAs, and branched fatty acids (BrFAs were significantly higher in FG than in AS, suggesting that both species selectively ingested nutrient rich particles. Significant reduction of SAFAs, MUFAs, PUFAs, and BrFAs occurred in MD and HD, with complete elimination of most PUFAs in FPs. A decrease in PUFAs 20:5ω3, 18:4ω3, 22:5ω3, 22:6ω3, 18:2ω6, 18:3ω3, 18:3ω6, odd-numbered BrFAs, and MUFA 18:1ω7 indicated that algal detritus and bacteria were important part of diet. These results have implications for the fate of specific dietary FAs, especially ω3 and ω6, and the contribution holothurian FPs make to the FA composition of coral reef and rocky intertidal ecosystems.

  1. Consequences of artificial deepwater ventilation in the Bornholm Basin for oxygen conditions, cod reproduction and benthic biomass – a model study

    Directory of Open Access Journals (Sweden)

    A. Stigebrandt

    2014-07-01

    Full Text Available We develop and use a circulation model to estimate hydrographical and ecological changes in the isolated basin water of the Bornholm Basin. By pumping well oxygenated so-called winter water, residing beneath the level of the summer thermocline, to the greatest depth of the basin, where it is forced to mix with the resident water, the rate of density reduction should increase and thereby the frequency of intrusions of new oxygen-rich deepwater. We show that pumping 1000 m3 s−1 should increase the rates of water exchange and oxygen supply by 2.5 and 3 times, respectively. The CRV (Cod Reproduction Volume, the volume of water in the isolated basin meeting the requirements for successful cod reproduction (S > 11, O2 > 2 mL L−1, should every year be greater than 54 km3, which is an immense improvement since it in certain years is currently much less. Anoxic bottoms should no longer occur in the basin and hypoxic events will become rare. This should permit extensive colonization of fauna on the earlier periodically anoxic bottoms. Increased biomass of benthic fauna should also mean increased food supply to economically valuable demersal fish like cod and flatfish. In addition, the bioturbation activity and re-oxygenation of the sediments should lead to increased phosphorus retention by the sediments.

  2. Radioactivity and United Kingdom estuaries: an overview identifying research priorities

    International Nuclear Information System (INIS)

    The report consists of the results of an evaluation of research priorities for the environmental radioactivity of estuaries, (and near shore waters) of the United Kingdom. The format of this report is:(i) general conclusions for the future requirements for research in the field of environmental radioactivity; (ii) an overview of some specific recommendations for research; and (iii) an appendix in which a comprehensive evaluation of the research priorities for specific areas of research are given. On the basis that man is the prime target for concern and protection, special attention has been given to the environment in the vicinity of the British Nuclear Fuels (BNFL) reprocessing plant at Sellafield, Cumbria, which is the source of major releases of a variety of radionuclides into the natural environment. Subjects covered in the Appendix are: site factors; pathways to man; source term; hot particles; terrestrial inputs; surveys and monitoring; analysis; organics; field versus laboratory data; biology; bioaccumulation factors; some bioaccumulators of radioactivity; bioturbation; bacteria; genetics; natural change; sediment; resuspension; surfaces; Ksub(d) factors; pore liquids; diagenesis and the ageing processes; airborne transport of radionuclides; models; natural radioactivity; public opinion; recreation; the ICRP; the ALARA principle; decommissioning of nuclear power stations; identification of research requirements; environmental radioactivity - the national effort. (U.K.)

  3. Effects of a natural toxin on life history and gene expression of Eisenia andrei.

    Science.gov (United States)

    van Ommen Kloeke, A E Elaine; Gong, Ping; Ellers, Jacintha; Roelofs, Dick

    2014-02-01

    Earthworms perform key functions for a healthy soil ecosystem, such as bioturbation. The soil ecosystem can be challenged by natural toxins such as isothiocyanates (ITCs), produced by many commercial crops. Therefore, the effects of 2-phenylethyl ITC were investigated on the earthworm Eisenia andrei using an ecotoxicogenomics approach. Exposure to 2-phenylethyl ITC reduced both survival and reproduction of E. andrei in a dose-dependent manner (median effective concentration [EC50] = 556 nmol/g). Cross-species comparative genomic hybridization validated the applicability of an existing 4 × 44,000 Eisenia fetida microarray to E. andrei. Gene expression profiles revealed the importance of metallothionein (MT) as an early warning signal when E. andrei was exposed to low concentrations of 2-phenylethyl ITC. Alignment of these MT genes with the MT-2 gene of Lumbricus rubellus showed that at least 2 MT gene clusters are present in the Eisenia sp. genome. At high-exposure concentrations, gene expression was mainly affected by inhibiting chitinase activity, inducing an oxidative stress response, and stimulating energy metabolism. Furthermore, analysis by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway implied that the high concentration may have caused impaired light sensitivity, angiogenesis, olfactory perception, learning, and memory. Increased levels of ITCs may be found in the field in the near future. The results presented call for a careful investigation to quantify the risk of such compounds before allowing them to enter the soil on a large scale. PMID:24395740

  4. Patterns of short-term sedimentation in a freshwater created marsh.

    Science.gov (United States)

    Harter, Sarah K; Mitsch, William J

    2003-01-01

    This study investigated different sedimentation measurement techniques and examined patterns of short-term sedimentation in two 1-ha replicate created freshwater marshes in central Ohio, USA. Short-term (one-year) sediment accumulation above feldspar, clay, glitter, and sand artificial marker horizons was compared at different water depths and distances from wetland inflow. A sediment budget was also constructed from turbidity and suspended sediment data for comparison with marker horizons. Glitter and sand marker horizons were the most successful for measuring sediment accumulation (81-100% marker recovery), while clay markers were completely unsuccessful. The sedimentation rate for both wetlands averaged 4.9 cm yr(-1) (36 kg m(-2) yr(-1)), and ranged from 1.82 to 9.23 cm yr(-1) (12.4 to 69.7 kg m(-2) yr(-1)). Sedimentation rates in deep, open water areas were significantly higher than in shallow, vegetated areas for both wetlands (t test, p wetlands, suggesting that bioturbation and turbulence may cause significant resuspension or that high hydrologic loads may distribute sediments throughout the basins. A sediment budget estimated sediment retention of approximately 740 g m(-2) yr(-1) per wetland (43% removal rate), yet gross sediment accumulation was 36,000 g m(-2) yr(-1) measured by marker horizons. These results suggest that erosive forces may have influenced sedimentation, but also may indicate problems with the sediment budget calculation methodology.

  5. Microfacies Analysis of Upper Eocene Shallow-water Carbonates from the Rodnei Mountains (N Romania

    Directory of Open Access Journals (Sweden)

    Diana Sahy

    2008-10-01

    Full Text Available A Priabonian carbonate ramp developed in the NW Rodnei Mountains as a part of a Paleogene sedimentary cover which overlies the metamorphic basement of the Eastern Carpathians. Two sections were sampled at different locations along the carbonate ramp. The deposits accumulated in a shallow environment, in which relative sea level change is seen as the main controlling factor of facies distribution. A shoreface → middle ramp → inner ramp transition was recorded in both sections. Associations of large benthic foraminifers and high siliciclastic input are the dominant features in the northern part of the ramp, while in the south corals and coralline algae thrived in an environment characterized by low hydrodynamic energy and clastic input. A 4-5 m thick intercalation identified in the middle ramp deposits of both studied sections shows a temporary change in fossil assemblages, with foraminifers almost completely replaced by red algae and rhodoliths, and extensive bioturbation caused by ostracods and gastropods. Towards the top of the carbonate deposits, large bivalve colonies and an increase in clastic input indicate a relative sea-level fall, which ultimately led to the cessation of carbonate sedimentation and the deposition of black shales on a basin-wide scale during the Lower Oligocene.

  6. Characterizing benthic substrates of Santa Monica Bay with seafloor photography and multibeam sonar imagery.

    Science.gov (United States)

    Edwards, Brian D; Dartnell, Peter; Chezar, Henry

    2003-01-01

    Seafloor photography from three cruises is combined with multibeam sonar imagery to characterize benthic substrates and associated fauna of Santa Monica Bay, California. The multibeam EM1000 imagery was collected in 1996. Two sampling cruises (in 1998 and 1999) provided photographs at 142 sites throughout the Bay; a final cruise (in 2000) collected still photographs and continuous video along nine transects on the mainland shelf from Pt. Dume to the Palos Verdes peninsula. Muddy substrates (typically low backscatter) were the predominant habitat throughout the Santa Monica Bay, from the 20 m isobath to the adjacent Santa Monica basin floor (780 m). Bioturbation was pervasive as evidenced by abundant open burrows, mounds, and faunal tracks and trails. Sandy substrates (typically intermediate to high backscatter) were restricted to the innermost mainland shelf and a narrow outer shelf band north of Santa Monica Canyon. Cobble and gravel substrates (high backscatter) were restricted to the innermost shelf south of El Segundo and limited parts of the shelf edge. Rocky substrates (high backscatter) with interspersed patches of sand and gravel occurred on the high-relief marginal plateau and along parts of the shelf break offshore of Malibu. PMID:12648949

  7. Sedimentary radioactive tracers and diffusive models.

    Science.gov (United States)

    Carroll, J; Lerche, I

    2010-08-01

    This paper examines the underlying assumptions and consequences of applying a steady-state equation to sediment profiles of radioactive tracers in order to deconvolute sedimentation from bioturbation processes modelled as a diffusive type process. Several factors follow immediately from this investigation: (i) if the observed radioactive concentration increases with depth over any finite depth range then the proposed steady-state, constant flux equation is not applicable. Any increase in radioactive concentration with depth implies a negative mixing coefficient which is a physical impossibility; (ii) when the radioactive concentration systematically decreases with increasing sedimentary depth then solutions to the steady-state conservation equation exist only when either the constant solid state flux to the sediment surface is small enough so that a positive mixing coefficient results or when the mixing coefficient is small enough so that a positive flux results. If the radioactive concentration, porosity and/or density of the solid phase are such that the proposed equation is inappropriate (because no physically acceptable solution exists) then one must abandon the proposed steady-state equation. Further: if the flux of solid sediment to the sediment surface varies with time then, of course, a steady-state conservation equation is also inappropriate. Simple examples illustrate that the assumption of steady-state restricts the applicability of this modelling approach to a relatively small sub-set of expected situations in the real world.

  8. Southern North Sea Basin in Europe: Biodiversity of the Marine Fürstenau Formation Including Early White and Megatooth Sharks

    Directory of Open Access Journals (Sweden)

    C. G. Diedrich

    2012-01-01

    Full Text Available The Fürstenau Formation (Lutetian, Paleogene, Eocene is based on type sections near Fürstenau in Germany (central Europe and is built of 22 meter thick marine glauconitic and strongly bioturbated sands, clays, and a vertebrate-rich conglomerate bed. The conglomerate layer from the Early Lutetian transgression reworked Lower Cretaceous, and Paleogene marine sediments. It is dominated by pebbles from the locally mountains which must have been transported by an ancient river in a delta fan. Marine reworked Lower Cretaceous and Paleogen pebbles/fossils, were derived from the underlying deposits of northern Germany (= southern pre North Sea basin. The benthic macrofauna is cold upwelling water influenced and non-tropical, and medium divers. The vertebrate fish fauna is extremely rich in shark teeth, with about 5,000 teeth per cubic meter of gravel. The most dominant forms are teeth from sand shark ancestors Striatolamia macrota, followed by white shark ancestors Carcharodon auriculatus. Even teeth from the magatooth shark ancestor Carcharocles sokolovi are present in a moderately diverse and condensed Paleogene fish fauna that also includes rays, chimaeras, and more then 80 different bony fish. Fragmentary turtle remains are present, and few terrestrial vertebrates and even marine mammals with phocids, sirenians and possibly whales.

  9. Anatomy of a shoreface sand ridge revisted using foraminifera: False Cape Shoals, Virginia/North Carolina inner shelf

    Science.gov (United States)

    Robinson, Marci M.; McBride, Randolph A.

    2008-01-01

    Certain details regarding the origin and evolution of shelf sand ridges remain elusive. Knowledge of their internal stratigraphy and microfossil distribution is necessary to define the origin and to determine the processes that modify sand ridges. Fourteen vibracores from False Cape Shoal A, a well-developed shoreface-attached sand ridge on the Virginia/North Carolina inner continental shelf, were examined to document the internal stratigraphy and benthic foraminiferal assemblages, as well as to reconstruct the depositional environments recorded in down-core sediments. Seven sedimentary and foraminiferal facies correspond to the following stratigraphic units: fossiliferous silt, barren sand, clay to sandy clay, laminated and bioturbated sand, poorly sorted massive sand, fine clean sand, and poorly sorted clay to gravel. The units represent a Pleistocene estuary and shoreface, a Holocene estuary, ebb tidal delta, modern shelf, modern shoreface, and swale fill, respectively. The succession of depositional environments reflects a Pleistocene sea-level highstand and subsequent regression followed by the Holocene transgression in which barrier island/spit systems formed along the Virginia/North Carolina inner shelf not, vert, ~5.2 ka and migrated landward and an ebb tidal delta that was deposited, reworked, and covered by shelf sand.

  10. Anatomy of a shoreface sand ridge revisited using foraminifera: False Cape Shoals, Virginia/North Carolina inner shelf

    Science.gov (United States)

    Robinson, M.M.; McBride, R.A.

    2008-01-01

    Certain details regarding the origin and evolution of shelf sand ridges remain elusive. Knowledge of their internal stratigraphy and microfossil distribution is necessary to define the origin and to determine the processes that modify sand ridges. Fourteen vibracores from False Cape Shoal A, a well-developed shoreface-attached sand ridge on the Virginia/North Carolina inner continental shelf, were examined to document the internal stratigraphy and benthic foraminiferal assemblages, as well as to reconstruct the depositional environments recorded in down-core sediments. Seven sedimentary and foraminiferal facies correspond to the following stratigraphic units: fossiliferous silt, barren sand, clay to sandy clay, laminated and bioturbated sand, poorly sorted massive sand, fine clean sand, and poorly sorted clay to gravel. The units represent a Pleistocene estuary and shoreface, a Holocene estuary, ebb tidal delta, modern shelf, modern shoreface, and swale fill, respectively. The succession of depositional environments reflects a Pleistocene sea-level highstand and subsequent regression followed by the Holocene transgression in which barrier island/spit systems formed along the Virginia/North Carolina inner shelf ???5.2 ka and migrated landward and an ebb tidal delta that was deposited, reworked, and covered by shelf sand.

  11. Varying depositional environments across the Oligocene-Miocene boundary and their relevance for East Antarctic ice sheet history: IODP Site U1356, Wilkes Land margin

    Science.gov (United States)

    Salabarnada, Ariadna; Escutia, Carlota; Nelson, Hans; Damuth, John E.; Brinkhuis, Henk

    2014-05-01

    IODP Expedition 318 drilled seven sites in two transects across the Wilkes Land (WL) margin of Antarctica. The objective was to obtain a long-term record of the Cenozoic Antarctic glaciation in response to climatic changes, including major transitions. Our work focuses on the study of nearly 300 meters of Oligocene-early Miocene sediments from Site 1356 (cores 42R to 72R) located on a channel levee in the lower continental rise. Shipboard core descriptions reported these sediments to consist of strongly bioturbated claystone and calcareous claystone with Zoophycos or Nereites ichnofacies. Subordinate lithofacies include: 1) laminated silty claystones, 2) convoluted claystones, sandstones and conglomerates; 3) mudstones and sandstones, with a few dispersed to common clasts; and 4) graded or cross-laminated siltstones and sandstones. Based on our study of facies associations in the cores, we differentiate 3 major sedimentary phases, representing important changes in the depositional environments off the WL margin. During the early-late Oligocene, sediments record deposition in a deep-water setting, with bottom currents reworking hemipelagic sediments. Late Oligocene sedimentary processes are dominated by successive fine- to coarse-grained debris-flow mass transport deposits. In the early Miocene, turbidites and hemipelagic sedimentation, characteristic of levee deposition, dominate. With this interpretation of sedimentary environments, plus the correlation between Site U1356 and seismic reflection profiles at the site and vicinity, we can begin to link the relation between along-slope and down-slope processes to the evolution of the East Antarctic Ice Sheet.

  12. Trace fossils from Eocene turbiditic deposits: A case study from the Slovak-Moravian Carpathians

    Directory of Open Access Journals (Sweden)

    Starek Dušan

    2015-12-01

    Full Text Available Well exposed, poorly bioturbated turbiditic sandstones of the Kýčera Beds (Zlín Formation; Eocene in the Bieščary Quarry contain the deep-sea Nereites ichnofacies. The trace fossils Ophiomorpha rudis, Halopoa annulata and Scolicia strozzii are mainly common in thick-bedded sandstone packages. They represent the Ophiomorpha rudis ichnosubfacies. Paleodiction strozzii, Nereites irregularis, and Zoophycos brianteus occur in a series of thin- to medium bedded fine grained turbiditic sandstones intercalated with mudstone shales. They belong to the Paleodictyon–Nereites ichnosubfacies. The sedimentological interpretation of the turbidity facies and the distribution of the trace fossils suggest that the recognized ichnosubfacies probably express a non-bathymetric facies trend from channel axis, levee to overbank or inter-channel/interlobe areas of a deep sea fan. The distribution and preservation of trace fossils depend mostly on lithology, sedimentation rate, erosion and amalgamation of beds in the proximal mid fan areas, bulldozing effect during colonization as well as on the hardly quantified effect of bottom oxygenation and supply of nutrients.

  13. Estimates of direct biological transport of radioactive waste in the deep sea with special reference to organic carbon budgets

    International Nuclear Information System (INIS)

    Calculations can be made for the maximum theoretical transport of pollutants such as radionuclides by movement of organisms out of a deep-sea benthic boundary layer dump site based on a presumption of a steady state organic carbon budget and estimated biological concentration factors. A calculated flux rate depends on the difference between a limiting input of organic matter and that carbon used by the biota or accumulating in the sediment. On average, the potential biological mass transport is low compared to physical transport. Exceptions to this generalization are possible in the far field after spatial gradients are obliterated or if natural mass migrations or periodic spawning concentrations occur in the near field. Biologically mediated fluxes of contaminants due to mixing of sediments by bioturbation or vertical flux due to scavenging by sinking particles are significant for movements of pollutants to and from sediments. These pathways contribute to the direct input of contaminants into food webs which may contain harvestable species. These fluxes are unimportant for mass transfers in the ocean but they determine the exposure of critical groups to contaminants

  14. Role of soil macrofauna in soil formation in post mining sites along climatic and litter quality gradients

    Science.gov (United States)

    Frouz, Jan

    2014-05-01

    Soil macrofauna can play important role in soil formation. Here we used thin soil sections to study this process in two environmental gradients, climatic gradient, and liter quality gradient. Climatic gradient consist from four chronosequences of post mining sites in the USA, covering hardwood forest (TN, IN), tallgrass prairie (IL), or shortgrass prairie (WY). Earthworms and other saprophages were absent in such shortgrass sites but were present in the wetter, eastern sites. Absence of saprophagous groups, and especially earthworms, resulted in the absence of bioturbation in shortgrass prairie sites while worm casts and other biogenic structures formed an important part of the soil profile in other chronosequences, in short grass prairie in turn physical processes, such as erosion may play important role in soil mixing. Litter quality gradient consists from set of 28 sites planted with six kind of tree stand (pine, larch, spruce, oak, lime and alder) and unreclaimed sites (covered by willow, birch, aspen dominated forest) on one large heap in Czech Republic. Earthworm density on these sites negatively correlate with CN ratio, the same relationships was shown for proportion of earthworm cast in soil volume. In sites with high earthworm density Oe layer was absent and A layer formed by worm casts was well developed, in the contrary when earthworm were absent Oe layer was thick and A layer absent. Development of A layer correlate with soil carbon storage.

  15. Pu in coastal marine environments

    Science.gov (United States)

    Santschi, Peter H.; Li, Yuan-Hui; Bell, Joy J.; Trier, Robert M.; Kawtaluk, Kathy

    1980-12-01

    Analysis of water samples from the New York Bight area and Narragansett Bay reveals that a small fraction of the total Pu (probably Pu (III + IV) species) is continuously removed to the sediments at a rate similar to that of the particle-reactive isotope 228Th. A more "soluble" Pu species appears to be released at times from the sediments to the water column in these nearshore regions. Sediments in shallow areas of the New York Bight south of Rhode Island and Narragansett Bay have high Pu inventories and relatively deep penetration of this element, although the net sediment accumulation rate is generally low (resuspension and sediment mixing are assumed to be the major controlling factors for the effective transfer of Pu from the water column to the sediments. By simultaneous modelling of the depth distribution of three tracers which operate on vastly different time scales: 234Th (half-life 24 days), 210Pb (half-life 22 years) and 239,240Pu (introduced into the environment during the past 30 years), bioturbation rates ranging from 4 to 32 cm 2/yr in the surface mixed layer (5-10 cm thick) and from 0.3 to 2.5 cm 2/yr in the layer below (up to 40 cm thick) and net sediment accumulation rates of approximately zero to 0.14 g/cm 2 yr were calculated for these areas.

  16. Ichnological record of palaeoenvironment from the Cretaceous-Paleogene boundary interval at El Kef, Tunisia: The first study of old and new sections at the stratotype area

    Science.gov (United States)

    Rodríguez-Tovar, F. J.; Uchman, A.; M'Hamdi, A.; Riahi, S.; Ismail-Lattrache, K. B.

    2016-08-01

    Trace fossil analysis of the Cretaceous-Paleogene (K/Pg) boundary interval at El Kef (Tunisia) has provided new information on the response of the macrobenthic tracemaker community to the K/Pg boundary event. Ichnological data from the Global Stratotype Section and Point (GSSP) for the Cretaceous-Paleogene (K/Pg) boundary were completed with those from a new, well-exposed section nearby. The trace fossil assemblage consists of dominant Trichichnus, frequent Chondrites, and rare Thalassinoides and Zoophycos in the uppermost Maastrichtian, and only Trichichnus in the lowest Danian, the diversity being comparatively lower than in other K/Pg boundary sections worldwide. Bioturbational structures are observed continuously across the K/Pg boundary interval, without primary lamination; this discards anoxic conditions. However, the upward-decreasing diversity in the sections may be related to a transition from a moderately dysoxic or slightly dysoxic macrobenthic habitat in the sediment during the latest Maastrichtian to a strong or very strong dysoxia during early Danian. Comparison with micropaleontological data reveals a minor influence of the K/Pg boundary event on the macrobenthic tracemaker community, while the change in oxygenation of pore waters at the El Kef sections can be attributed to local or regional phenomenon, marked by increasing clay content in the Danian sediments.

  17. Oxygen and evolutionary patterns in the sea: onshore/offshore trends and recent recruitment of deep-sea faunas

    Science.gov (United States)

    Jacobs, D. K.; Lindberg, D. R.

    1998-01-01

    Over the last 15 years a striking pattern of diversification has been documented in the fossil record of benthic marine invertebrates. Higher taxa (orders) tend to originate onshore, diversify offshore, and retreat into deep-water environments. Previous studies attribute this macroevolutionary pattern to a variety of causes, foremost among them the role of nearshore disturbance in providing opportunities for the evolution of novel forms accorded ordinal rank. Our analysis of the post-Paleozoic record of ordinal first appearances indicates that the onshore preference of ordinal origination occurred only in the Mesozoic prior to the Turonian stage of the Cretaceous, a period characterized by relatively frequent anoxic/dysoxic bottom conditions in deeper marine environments. Later, in the Cretaceous and Cenozoic, ordinal origination of benthic organisms did not occur exclusively, or even preferentially, in onshore environments. This change in environmental pattern of ordinal origination roughly correlates with Late Cretaceous: (i) decline in anoxia/dysoxia in offshore benthic environments; (ii) extinction of faunas associated with dysoxic conditions; (iii) increase in bioturbation with the expansion of deep burrowing forms into offshore environments; and (iv) offshore expansion of bryozoan diversity. We also advance a separate argument that the Cenomanian/Turonian and latest Paleocene global events eliminated much of the deep-water benthos. This requires a more recent origin of modern vent and deep-sea faunas, from shallower water refugia, than the Paleozoic or early Mesozoic origin of these faunas suggested by other workers.

  18. Enchytraeus crypticus as model species in soil ecotoxicology.

    Science.gov (United States)

    Castro-Ferreira, Marta P; Roelofs, Dick; van Gestel, Cornelis A M; Verweij, Rudo A; Soares, Amadeu M V M; Amorim, Mónica J B

    2012-06-01

    Enchytraeids are ecologically relevant soil organisms, due to their activity in decomposition and bioturbation in many soil types worldwide. The enchytraeid reproduction test (ERT) guidelines ISO 16387 and OECD 220 are exclusive to the genus Enchytraeus and recommend using the species E. albidus with a 6-week test period. The suggested alternative, E. crypticus has a shorter generation time which may enable the ERT to be twice as fast. To confirm the suitability of a 3-week test period for E. crypticus, the toxicity of five chemicals, with distinct properties and modes of action, was assessed in LUFA 2.2 soil. In all controls the validity criteria were met, as survival of E. crypticus was above 92% and more than 772 juveniles were produced. The good performance supports its appropriateness as model species. Reproduction was more sensitive than survival, with only cadmium and 3,5-dichloroaniline causing significant lethal effects in the tested concentration ranges. The effect concentration causing 50% reduction in the number of juveniles (EC50) was 35 mg kg(-1) for cadmium, ecotoxicology, with advantages such as good control performance and speed, leading to a reliable and faster ERT.

  19. Hyperspectral imaging of the microscale distribution and dynamics of microphytobenthos in intertidal sediments

    KAUST Repository

    Chennu, Arjun

    2013-10-03

    We describe a novel, field-deployable hyperspectral imaging system, called Hypersub, that allows noninvasive in situ mapping of the microphytobenthos (MPB) biomass distribution with a high spatial (sub-millimeter) and temporal (minutes) resolution over areas of 1 × 1 m. The biomass is derived from a log-transformed and near-infrared corrected reflectance hyperspectral index, which exhibits a linear relationship (R2 > 0.97) with the chlorophyll a (Chl a) concentration in the euphotic zone of the sediment and depends on the sediment grain size. Deployments of the system revealed that due to factors such as sediment topography, bioturbation, and grazing, the distribution of MPB in intertidal sediments is remarkably heterogeneous, with Chl a concentrations varying laterally by up to 400% of the average value over a distance of 1 cm. Furthermore, due to tidal cycling and diel light variability, MPB concentrations in the top 1 mm of sediments are very dynamic, changing by 40–80% over a few hours due to vertical migration. We argue that the high-resolution hyperspectral imaging method overcomes the inadequate resolution of traditional methods based on sedimentary Chl a extraction, and thus helps improve our understanding of the processes that control benthic primary production in coastal sediments.

  20. Palaeoecological aspects of some invertebrate trace fossils from the mid- to Upper Permian Middleton Formation (Adelaide Subgroup, Beaufort Group, Karoo Supergroup), Eastern Cape, South Africa

    Science.gov (United States)

    Bordy, Emese M.; Linkermann, Sean; Prevec, Rose

    2011-10-01

    Ichnological and sedimentological analyses in the Eastern Cape allowed the first description of a Cochlichnus-dominated ichnofossil site from the mid- to Upper Permian Middleton Formation (Karoo Supergroup) in South Africa. The locality is within the uppermost Pristerognathus Assemblage Zone, a biostratigraphic interval characterized by a low vertebrate biodiversity at the turn of the mid- to Late Permian. Our field data indicates that the surficial bioturbation of very fine to fine-grained sand layers resulted from life activities of shallow infaunal and epifaunal invertebrates (possibly annelids, aquatic oligochaetes, nematodes, insect larvae) and fish. The morphology of the trails, their relationship to the substrate and the behaviour inferred from them indicate that the tracemakers developed a strategy that facilitated the optimization of low food resources in a permanently submerged freshwater setting. Combined ichnological and sedimentological evidence suggests a low-energy, freshwater lacustrine depositional environment, where occasional higher energy currents brought nutrients. Data also imply that colonization of these erratic event beds by opportunistic sediment-feeders was short-lived and followed by longer intervals of lower energy deposition under possibly poorly oxygenated conditions. We propose that these event beds as well as the sporadic red mudstones of the Middleton Formation may have formed during short-term, higher storm-frequency and dryer periods, signalling changes in the otherwise humid climate in this part of the main Karoo Basin during the mid- to Late Permian.

  1. Insights into biogeochemical cycling from a soil evolution model and long-term chronosequences

    Directory of Open Access Journals (Sweden)

    M. O. Johnson

    2014-04-01

    Full Text Available Despite the importance of soil processes for global biogeochemical cycles, our capability for predicting soil evolution over geological timescales is poorly constrained. We attempt to probe our understanding and predictive capability of this evolutionary process by developing a mechanistic soil evolution model, based on an existing model framework, and comparing the predictions with observations from soil chronosequences in Hawaii. Our soil evolution model includes the major processes of pedogenesis: mineral weathering, percolation of rainfall, leaching of solutes, surface erosion, bioturbation and vegetation interactions and can be applied to various bedrock compositions and climates. The specific properties the model simulates over timescales of tens to hundreds of thousand years are, soil depth, vertical profiles of elemental composition, soil solution pH and organic carbon distribution. We demonstrate with this model the significant role that vegetation plays in accelerating the rate of weathering and hence soil profile development. Comparisons with soils that have developed on Hawaiian basalts reveal a remarkably good agreement with Na, Ca and Mg profiles suggesting that the model captures well the key components of soil formation. Nevertheless, differences between modelled and observed K and P are substantial. The fact that these are important plant nutrients suggests that a process likely missing from our model is the active role of vegetation in selectively acquiring nutrients. This study therefore indirectly indicates the valuable role that vegetation can play in accelerating the weathering and thus release of these globally important nutrients into the biosphere.

  2. Mineralogical, geochemical and micromorphological evaluation of the Plio-Quaternary paleosols and calcretes from Karahamzall, Ankara (Central Turkey)

    Science.gov (United States)

    Küçükuysal, Ceren; Kapur, Selim

    2014-06-01

    We present the mineralogical, micromorphological, and geochemical characteristics of the paleosols and their carbonates from Karahamzall, Ankara (Central Turkey). The paleosols include calcretes of powdery to nodular forms and alternate with channel deposits. The presence of pedofeatures, such as clay cutans, floating grains, circumgranular cracks, MnO linings, secondary carbonate rims, traces of past bioturbation and remnants of root fragments are all the evidence of pedogenesis. Bw is the most common soil horizon showing subangular-angular blocky to granular or prismatic microstructures. Calcretes, on the other hand, are evaluated as semi-mature massive, nodular, tubular or powdery forms. The probable faunal and floral passages may also imply the traces of life from when these alluvial deposits were soil. The presence of early diagenetic palygorskite and dolomite together with high salinization, high calcification and low chemical index of alteration values are evidence of the formation of calcretes under arid and dry conditions. δ13C compositions of the carbonates ranging from -7.11 ‰ to -7.74 ‰ VPDB are comformable with the world pedogenic carbonates favouring the C4 vegetation; likely δ18O compositions of the carbonates are between -3.97 ‰ and -4.91 ‰ which are compatible with the paleosols formed under the influence of meteroic water in the vadose zone

  3. Sedimentation studies relevant to low-level radioactive effluent dispersal in the Irish Sea. Part III. An evaluation of possible mechanisms for the incorporation of radionuclides into marine sediments

    International Nuclear Information System (INIS)

    Based on circumstantial evidence the Cumbrian mud area was previously interpreted as accretionary. There are no measurements confirming that riverborne sediment reaches the mud area and the postulated subtidal sources appear to be sealed by a lag gravel. In contrast, fine sediment deposited in Liverpool Bay is known to return to the Ribble, Mersey and Dee. Similarly 'hot' particles originating in the Sellafield outfall are implied to travel, perhaps accompanied by natural fine sediment, into the Ravenglass Estuary and elsewhere. The likely interpretation is that fine sediment accumulating in the coastal zone of the eastern Irish Sea is partly derived from seawards. Possible sources are coast erosion and the unconsolidated mud areas themselves. Radionuclide profiles from the Cumbrian mud area have previously been interpreted as confirming the accretionary hypothesis. In fact three principal types of radionuclide profiles occur, which are interpreted here to indicate progressively more efficient bioturbation. Burrowing animals may also supply uncontaminated sediment to the bed, where it absorbs radionuclides before, in part, being redeposited locally. This implies that no large external sediment source is necessary to explain the radionuclide profiles encountered. We thus interpret the area as a relatively stable sedimentary regime dominated by biological processes. (author)

  4. Regional and long-term patterns of lead concentrations in fluvial, marine and terrestrial systems and humans in Europe

    Energy Technology Data Exchange (ETDEWEB)

    Hagner, C. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Hydrophysik

    2000-07-01

    Lead contamination of abiotic and biotic systems has been studied closely since the early 1970s, when lead was firstly perceived as an environmental problem. Lead emission reduction policies were implemented throughout Europe during that time. Nonetheless, analyses of lead loads in aquatic systems, such as the river Elbe, showed no decline over time in either suspended matter or surface sediments. Regional differences in lead concentrations of fluvial systems were found, due to tidal influence, runoff and local emissions. Lead contamination of sediments from the North Sea was highest in estuaries. Concentrations in sediment cores were quite stable down to the depth of background values, due to bioturbation, flow, waves and meandering channels. Terrestrial soils in Europe were highly polluted in industrial and ore mining areas and large cities. No decline in lead concentrations was evident in foraminifers, bladder wrack or fish. It was found that contamination in sediments, mammals and fish was higher in coastal zones than in the open sea. In contrast to in aquatic organisms, positive impacts of lead reduction regulations were detected in terrestrial plants, which adsorbed or took up lead mainly through atmospheric lead deposition. European lead concentrations in plants decreased coincidently with lead emissions. That trend could also be identified in the blood lead levels of the human population in Europe: since 1979 they have declined in every group of the population. Mainly influenced by age, sex and the living environment, overall, the lead loads of humans had never been high enough to cause health danger. (orig.)

  5. Microplastics in the Terrestrial Ecosystem: Implications for Lumbricus terrestris (Oligochaeta, Lumbricidae).

    Science.gov (United States)

    Huerta Lwanga, Esperanza; Gertsen, Hennie; Gooren, Harm; Peters, Piet; Salánki, Tamás; van der Ploeg, Martine; Besseling, Ellen; Koelmans, Albert A; Geissen, Violette

    2016-03-01

    Plastic debris is widespread in the environment, but information on the effects of microplastics on terrestrial fauna is completely lacking. Here, we studied the survival and fitness of the earthworm Lumbricus terrestris (Oligochaeta, Lumbricidae) exposed to microplastics (Polyethylene, litter at concentrations of 7, 28, 45, and 60% dry weight, percentages that, after bioturbation, translate to 0.2 to 1.2% in bulk soil. Mortality after 60 days was higher at 28, 45, and 60% of microplastics in the litter than at 7% w/w and in the control (0%). Growth rate was significantly reduced at 28, 45, and 60% w/w microplastics, compared to the 7% and control treatments. Due to the digestion of ingested organic matter, microplastic was concentrated in cast, especially at the lowest dose (i.e., 7% in litter) because that dose had the highest proportion of digestible organic matter. Whereas 50 percent of the microplastics had a size of litter, 90 percent of the microplastics in the casts was <50 μm in all treatments, which suggests size-selective egestion by the earthworms. These concentration-transport and size-selection mechanisms may have important implications for fate and risk of microplastic in terrestrial ecosystems. PMID:26852875

  6. Radiometric studies of box cores from the Ontong-Java plateau

    International Nuclear Information System (INIS)

    Five box cores, 30-35 cm deep, from the Ontong-Java Plateau in the Pacific Ocean have been analysed for several radioisotopes, bringing the total number of cores thus studied to nine. All cores contain calcareous sediments; they are from water depths between 1600 and 4300 m. The studies were made with a view to measure CaCO3 accumulation rates in the equatorial Pacific and to understand the nature of bioturbation and of erosion effects on carbonate accumulation. The 14C based accumulation rates vary from between 0.7 and 3 cm/k yr. The upper-most disturbed layer in the cores showing distinct effects of surface processes, including benthic mixing, is between 4 and 10 cm thick, in good agreement with the mean values for mixed layer thicknesses of 8 +- 2 cm reported earlier. The nature of mixing is very complicated. It does not resemble diffusion; considerable mixing seems to have occurred due to discrete events. The effects of in-situ dissolution during Holocene accumulation are clearly seen in two cores taken below 4000m. (auth.)

  7. Sediment quality and ecorisk assessment factors for a major river system

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, V.G. [Westinghouse Hanford Co., Richland, WA (United States); Wagner, J.J. [Pacific Northwest Lab., Richland, WA (United States); Cutshall, N.H. [Oak Ridge National Lab., TN (United States)

    1993-08-01

    Sediment-related water quality and risk assessment parameters for the Columbia River were developed using heavy metal loading and concentration data from Lake Roosevelt (river km 1120) to the mouth and adjacent coastal zone. Correlation of Pb, Zn, Hg, and Cd concentrations in downstream sediments with refinery operations in British Columbia suggest that solutes with K{sub d}`s > 10{sup 5} reach about 1 to 5 {mu}g/g per metric ton/year of input. A low-suspended load (upriver avg. <10 mg/L) and high particle-surface reactivity account for the high clay-fraction contaminant concentrations. In addition, a sediment exposure path was demonstrated based on analysis of post-shutdown biodynamics of a heavy metal radiotracer. The slow decline in sediment was attributed to resuspension, bioturbation, and anthropogenic disturbances. The above findings suggest that conservative sediment quality criteria should be used to restrict additional contaminant loading in the upper drainage basin. The issuance of an advisory for Lake Roosevelt, due in part to Hg accumulation in large sport fish, suggests more restrictive controls are needed. A monitoring strategy for assessing human exposure potential and the ecological health of the river is proposed.

  8. Paleoclimatical significance of the paleosol levels occurring in the Miocene-Pleistocene stratigraphy of the Manonga-Wembere Valley inCentral Tanzania

    Institute of Scientific and Technical Information of China (English)

    PeterD.Kafumu

    2004-01-01

    Micromorphological characteristics of four paleosol levels of the Manonga - Wembere deposits in Central Tanzania indicate periods of wetter climate in the Pliocene than at present. The stratigraphy of the studied section shows a series of lacustrine calcareous clay sediments alternating with gravel, sand and silt. The sediments are believed to have been deposited in the Manonga - Wembere paleolake environment. Paleosols intercalate these sediments and were formed when stable landscapes developed on former lake beds during regression periods. Micromorphological features of the paleosols indicate strong clay illuviation of red to yellow typic clay coating and some Fe-Mn hydoxide hypocoatings in voids and channels. The groundmass consists of either an accumulation of bioturbated yellow to red clay coating fragments or an argillic red to yellow groundmass of clay mass. Such an illuviation and its associated groundmass is comparable to intense clay illuviation fronts that are found in present-day calcareous sediments of warm and wet climates. The paleosol levels therefore represent wetter climatic conditions than today in the area during the Lower Pliocene.

  9. Abundance of adult horseshoe crabs (Limulus polylphemus) in Delaware Bay estimated from a bay-wide mark-recapture study

    Science.gov (United States)

    Smith, D.R.; Millard, M.J.; Eyler, S.

    2006-01-01

    Estimates of the abundance of American horseshoe crabs (Limulus polyphemus) are important to determine egg production and to manage populations for the energetic needs of shorebirds that feed on horseshoe crab eggs. In 2003, over 17,500 horseshoe crabs were tagged and released throughout Delaware Bay, and recaptured crabs came from spawning surveys that were conducted during peak spawning. We used two release cohorts to test for a temporary effect of tagging on spawning behavior and we adjusted the number of releases according to relocation rates from a telemetry study. The abundance estimate was 20 million horseshoe crabs (90% confidence interval: 13-28 million), of which 6.25 million (90% CI: 4.0-8.8 million) were females. The combined harvest rate for Delaware, New Jersey, Virginia, and Maryland in 2003 was 4% (90% CI: 3-6%) of the abundance estimate. Over-wintering of adults in Delaware Bay could explain, in part, differences in estimates from ocean-trawl surveys. Based on fecundity of 88,000 eggs per female, egg production was 5.5??1011 (90% CI: 3.5??1011, 7.7??1011), but egg availability for shorebirds also depended on overlap between horseshoe crab and shorebird migrations, density-dependent bioturbation, and wave-mediated vertical transport.

  10. Resource utilisation by deep-sea megabenthos in the Canadian High Arctic (Baffin Bay and Parry Channel)

    Science.gov (United States)

    Bourgeois, Solveig; Witte, Ursula; Harrison, Ailish M.; Makela, Anni; Kazanidis, Georgios; Archambault, Philippe

    2016-04-01

    Ongoing climate change in the Arctic is causing drastic alteration of the Arctic marine ecosystem functioning, such as shifts in patterns of primary production, and modifying the present tight pelagic-benthic coupling. Subsequently benthic communities, which rely upon organic matter produced in the top layers of the Ocean, will also be affected by these changes. The benthic megafaunal communities play a significant role in ecological processes and ecosystem functioning (i.e. organic matter recycling, bioturbation, food source for the higher trophic levels…). Yet, information is scarce regarding the main food sources for dominant benthic organisms, and therefore the impact of the ongoing changes is difficult to assess. The goal of this study is to investigate the preferential feeding of different carbon sources by megabenthic organisms in the Canadian High Arctic and to identify environmental drivers which explain the observed trends. In summer 2013, benthic megafauna was collected at 9 stations spread along latitudinal (58 to 81°N) and longitudinal (62 to 114°W) transects in the Baffin Bay and Parry Channel, respectively. Carbon and nitrogen bulk stable isotope analyses (δ13C and δ15N) were performed on several species divided into groups according to their feeding type. This study highlights distinct trends in δ13C values of benthic organisms suggesting the importance of both phytoplankton and ice algae as carbon sources for megafauna in the Canadian High Arctic. The importance of physical and biological parameters as drivers of food web structure will be furthermore discussed.

  11. Geological characteristics of the peat deposits in Costa Rica (preliminary study)

    Energy Technology Data Exchange (ETDEWEB)

    Mora, S.; Cohen, A.D.; Raymond, R.; Alvarado, A.; Malavassi, L.

    1986-04-01

    Wide areas containing peat deposits have been found in Costa Rica. Three of them were selected for the preliminary evaluation. In the Talamanca range peat occurs as a thin blanket deposit about 1 m thick in an area of about 150 km/sup 2/. It is very decomposed (about 28% fibers), with high ash content, (21%) and extensively bioturbated. It has the lowest water content (84%), pH, fixed carbon (23%) and sulphur (0.2%) of all the sampled sites, However, it has the highest bulk density (0.22 g/cm/sup 3/) and volatile components (55%). Its calorific value averages 7700 Btu/lb, dry. In Medio Queso de Upala, several peat horizons are interbedded with alluvium layers within a 70 km/sup 2/ flood plain. They have the highest calorific values (8000 Btu/lb, dry), fixed carbon (30%) and ash content (22%). Their fiber content is low (27%), and the bulk density 0.20 g/cm/sup 3/. In El Silencio, near Siquirres, the thickness of the main layer exceeds 3.5 m, averaging 19% of ash, 53% of fibers, 5.8 pH, 0.6% of sulphur, 0.13 g/cm/sup 3/ bulk density, and 7500 Btu/lb, dry. (5 refs.)

  12. Radiocarbon dating of palaeosol components in moraines in Lapland, northern Sweden

    Science.gov (United States)

    Hormes, Anne; Karlén, Wibjörn; Possnert, Göran

    2004-10-01

    Accurate geochronologies are the key for comparison of palaeoclimate records. In order to clarify problems concerning the geochronology of glacier fluctuations we dated palaeosols in moraines in the Kebnekaise mountain region of Swedish Lapland. These palaeosols already have been dated several years ago using bulk samples of the palaeosols and yielded ages of 6180-5790 and 2750-2100 cal yr BP. In an attempt to evaluate the sources of contamination associated with bulk samples these soils were re-dated by using Coleoptera fragments, Cenococcum geophilum spores, humic acids and woody plant tissues. The new dates reveal that the two palaeosols found within the moraines represent much longer periods of time than was previously assumed. Soil formation periods can be distinguished for periods 7800-7580, 6300-4080, 2450-2000 and 1170-740 cal yr BP. These age groups point to differentiated soil formation processes, resedimentation, bioturbation and/or cryoturbation. The results show that dated terrestrial macrofossils from glacial moraines indicate climate changes that are in accordance with other proxy records in northern and central Scandinavia and in certain times off-phase with glacier fluctuations in southern maritime Norway. This throws light on possible changing interaction of forcing factors during the Holocene.

  13. Seasonality and depth distribution of the abundance and activity of ammonia oxidizing microorganisms in marine coastal sediments (North Sea

    Directory of Open Access Journals (Sweden)

    Yvonne Antonia Lipsewers

    2014-09-01

    Full Text Available Microbial processes such as nitrification and anaerobic ammonium oxidation (anammox are important for nitrogen cycling in marine sediments. Seasonal variations of archaeal and bacterial ammonia oxidizers (AOA and AOB and anammox bacteria, as well as the environmental factors affecting these groups, are not well studied. We have examined the seasonal and depth distribution of the abundance and potential activity of these microbial groups in coastal marine sediments of the southern North Sea. This was achieved by quantifying specific intact polar lipids (IPLs as well as the abundance and gene expression of their 16S rRNA gene, the ammonia monooxygenase subunit A (amoA gene of AOA and AOB, and the hydrazine synthase (hzsA gene of anammox bacteria. AOA, AOB and anammox bacteria were detected and transcriptionally active down to 12 cm sediment depth. In all seasons, the abundance of AOA was higher compared to the AOB abundance suggesting that AOA play a more dominant role in aerobic ammonia oxidation in these sediments. Anammox bacteria were abundant and active even in oxygenated and bioturbated parts of the sediment. The abundance of AOA and AOB was relatively stable with depth and over the seasonal cycle, while anammox bacteria abundance and transcriptional activity were highest in August. North Sea sediments thus seem to provide a common, stable, ecological niche for AOA, AOB and anammox bacteria.

  14. Phylogenetic and functional diversity of nitrogen cycling microbes in coastal sediments

    Directory of Open Access Journals (Sweden)

    Xiaoli Zhang

    2013-07-01

    Full Text Available The coastal zone contains diverse habitats which are usually characterized by strong environmental gradients (e.g. salinity, nutrients and pollutants. This makes the coastal zone an ideal experimental laboratory for describing microbial diversity and testing hypotheses on community structure, function and control. Coastal sediment is of significance in nutrient regeneration and transformation involving different assemblages of microbes in the nitrogen cycle. This review focuses on 16S rRNA gene-based phylogenetic diversity and the key enzyme encoding gene-based (e.g. nifH, amoA, narG, nirS, nirK, nosZ, nrfA, hzo and hzs functional diversity of nitrogen fixing, ammonia oxidizing and anaerobic ammonia oxidation (Anammox bacteria as well as bacteria and fungi involved in denitrification and dissimilatory nitrate reduction to ammonium (DNRA. Characteristics of community composition and diversity of nitrogen cycling microbes in different habitats (e.g. estuarine, intertidal flats, seagrass or seaweed beds, mangroves, salt marsh, coral reefs, and shallow seas, and their spatiotemporal patterns under benthic pollution or bioturbation are reviewed. Future directions for a better understanding diversity of nitrogen cycling microbes are suggested, such as culture methods and technologies, and single-cell sequencing, etc.

  15. Microfacies analysis of the Upper Triassic (Norian) "Bača Dolomite": early evolution of the western Slovenian Basin (eastern Southern Alps, western Slovenia)

    Science.gov (United States)

    Gale, Luka

    2010-08-01

    The Slovenian Basin represents a Mesozoic deep-water sedimentary environment, situated on the southern Tethyan passive margin. Little is known about its earliest history, from the initial opening in the Carnian (probably Ladinian) to a marked deepening at the beginning of the Jurassic. The bulk of the sediment deposited during this period is represented by the Norian-Rhaetian "Bača Dolomite", which has, until now, been poorly investigated due to a late-diagenetic dolomitization. The Mount Slatnik section (south-eastern Julian Alps, western Slovenia) is one of a few sections where the dolomitization was incomplete. Detailed analysis of this section allowed us to recognize eight microfacies (MF): MF 1 (calcilutite), MF 2 (pelagic bivalve-radiolarian floatstone/wackestone to rudstone/packstone), MF 3 (dolomitized mudstone) with sub-types MF 3-LamB and MF 3-LamD (laminated mudstone found in a breccia matrix and laminated mudstone found in thin-bedded dolomites, respectively) and MF 3-Mix (mixed mudstone), MF 4 (bioturbated radiolarian-spiculite wackestone), MF 5 (fine peloidal-bioclastic packstone), MF 6 (very fine peloidal packstone), MF 7 (bioclastic wackestone) and MF 8 (crystalline dolomite). The microfacies and facies associations indicate a carbonate slope apron depositional environment with hemipelagic sedimentation punctuated by depositions from turbidites and slumps. In addition to the sedimentary environment, two "retrogradation-progradation" cycles were recognized, each with a shift of the depositional setting from an inner apron to a basin plain environment.

  16. Use of X-ray computed tomography for the estimation of parameters relevant to the modeling of acoustic scattering from the seafloor

    International Nuclear Information System (INIS)

    Underwater sonar systems are increasingly being used at frequencies greater than 100 kHz for bathymetry measurement, seabed characterization and object detection [Proceedings of the 5th European Conference on Underwater Acoustics, Vol. 2, p. 1283]. In general, there are two main contributions to the backscattered acoustic wave due to seafloor properties: scattering from interface roughness (interface scattering) and from volume heterogeneities (e.g. due to sediment layering or bioturbation) in the first few decimeters of the seabed (volume scattering) [J. Acoust. Soc. Am. 95 (1994) 2441]. Until recently, modeling and validated measurements at these very high frequencies have been limited by the difficulty of accurately characterizing seabed properties at centimeter and sub-centimeter scales. This paper examines how X-ray computed tomography (CT) scans of seafloor cores have been used to obtain data sets that not only allow computation of both the statistical and the spatial distribution of density-related parameters relevant to volume scattering modeling, but also represent a valuable tool for selective, nondestructive visual analysis of inner features of cores. The main advantages of X-ray CT are the excellent spatial resolution and the ready availability of digital data sets that naturally lend themselves to computer processing. The methodology of the whole process, from core collection to advanced instruis described here, with special emphasis on image processing and density quantification issues

  17. Freshwater seepages and ephemeral macroalgae proliferation in an intertidal bay: I Effect on benthic community structure and food web

    Science.gov (United States)

    Ouisse, Vincent; Riera, Pascal; Migné, Aline; Leroux, Cédric; Davoult, Dominique

    2011-01-01

    Freshwater seepages and ephemeral Enteromorpha spp. proliferation create heterogeneity at small spatial scale in intertidal sediment. Macrobenthic community diversity was compared between these two disturbances and their respective control points throughout the year 2007 at the Roscoff Aber Bay (Western English Channel, France). In March and September 2007, trophic community pathways of characteristic species were additionally studied using stable isotope ratios of carbon and nitrogen. The low salinity recorded at the freshwater seepage induced the exclusion of the main bioturbator and the presence of omnivores which modified the community composition by biotic pressure. Moreover, food web analyses clearly highlighted a separation at small spatial scale between the two trophic pathways of the impacted area and its control. On the contrary, little differences were observed owning to the ephemeral Enteromorpha spp. proliferation. This suggested a progressive and diffusive disturbance which was applied from the algal mat to the nearby area. However, seasonal changes were observed. First, the algal expansion phase increased the macrofauna diversity and foraminifers' abundance (meiofauna) and then acted as a physical barrier decreasing sediment and water column exchanges and decreasing the fauna diversity. This study highlights the need to take into account small spatial heterogeneity to avoid misinterpretations in intertidal ecology studies.

  18. El Niño-Southern oscillation variability from the late cretaceous marca shale of California

    Science.gov (United States)

    Davies, Andrew; Kemp, Alan E.S.; Weedon, Graham P.; Barron, John A.

    2012-01-01

    Changes in the possible behavior of El Niño–Southern Oscillation (ENSO) with global warming have provoked interest in records of ENSO from past “greenhouse” climate states. The latest Cretaceous laminated Marca Shale of California permits a seasonal-scale reconstruction of water column flux events and hence interannual paleoclimate variability. The annual flux cycle resembles that of the modern Gulf of California with diatoms characteristic of spring upwelling blooms followed by silt and clay, and is consistent with the existence of a paleo–North American Monsoon that brought input of terrigenous sediment during summer storms and precipitation runoff. Variation is also indicated in the extent of water column oxygenation by differences in lamina preservation. Time series analysis of interannual variability in terrigenous sediment and diatom flux and in the degree of bioturbation indicates strong periodicities in the quasi-biennial (2.1–2.8 yr) and low-frequency (4.1–6.3 yr) bands both characteristic of ENSO forcing, as well as decadal frequencies. This evidence for robust Late Cretaceous ENSO variability does not support the theory of a “permanent El Niño,” in the sense of a continual El Niño–like state, in periods of warmer climate.

  19. Magnetic study of four turbidites

    Science.gov (United States)

    Tanty, Cyrielle; Valet, Jean-Pierre; Carlut, Julie; Bassinot, Franck

    2016-04-01

    Turbidites are usually discarded from paleomagnetic studies, and therefore their remanence and magnetic properties are poorly described. Turbidites are exempt of bioturbation and acquire their remanent magnetization over a short time period. We have studied magnetic characteristics of four different quaternary turbidites sampled in marine sediment cores. Downcore coarsening of both magnetic and sedimentary fractions indicates that coarser sedimentary and magnetic grains reached the bottom first. As coarse magnetic grains have no reason to preferentially cluster with coarse sediment particles during their fall we infer that flocculation, if any, was not dominant before the particles reached the surface of the sediment. This observation goes against the concept that aggregates would be the dominant factor impeding alignment of magnetic grains in natural sediments. Another significant result is a progressive shallowing of magnetic inclinations between the upper and bottom layers of turbidites, while the axes of magnetic susceptibility are randomly scattered. The amplitude of shallowing increases with the size of the events and obeys a simple linear scaling law. We infer that hydrodynamic conditions appear to control the orientation of the magnetic moments. The small spherical grains are randomly oriented with zero resultant magnetization in the most turbulent conditions. The small elongated grains are also subjected to competition between the gravity and the magnetic forces, but in the most turbulent conditions they rest at the bottom with their long axes parallel to the surface yielding shallow inclinations. The absence of magnetic perturbations present in the smallest (11 cm thick) and thus weakly turbulent event supports also this model.

  20. High resolution shallow geologic characterization of a late Pleistocene eolian environment using ground penetrating radar and optically stimulated luminescence techniques: North Carolina, USA

    Science.gov (United States)

    Mallinson, D.; Mahan, S.; Moore, Christine

    2008-01-01

    Geophysical surveys, sedimentology, and optically-stimulated luminescence age analyses were used to assess the geologic development of a coastal system near Swansboro, NC. This area is a significant Woodland Period Native American habitation and is designated the "Broad Reach" archaeological site. 2-d and 3-d subsurface geophysical surveys were performed using a ground penetrating radar system to define the stratigraphic framework and depositional facies. Sediment samples were collected and analyzed for grain-size to determine depositional environments. Samples were acquired and analyzed using optically stimulated luminescence techniques to derive the depositional age of the various features. The data support a low eolian to shallow subtidal coastal depositional setting for this area. Li-DAR data reveal ridge and swale topography, most likely related to beach ridges, and eolian features including low-relief, low-angle transverse and parabolic dunes, blowouts, and a low-relief eolian sand sheet. Geophysical data reveal dominantly seaward dipping units, and low-angle mounded features. Sedimentological data reveal mostly moderately-well to well-sorted fine-grained symmetrical to coarse skewed sands, suggesting initial aqueous transport and deposition, followed by eolian reworking and bioturbation. OSL data indicate initial coastal deposition prior to ca. 45,000 yBP, followed by eolian reworking and low dune stabilization at ca. 13,000 to 11,500 yBP, and again at ca. 10,000 yBP (during, and slightly after the Younger Dryas chronozone).

  1. User guide for luminescence sampling in archaeological and geological contexts

    Science.gov (United States)

    Nelson, Michelle S.; Gray, Harrison J.; Johnson, Jack A.; Rittenour, Tammy M.; Feathers, James K.; Mahan, Shannon

    2015-01-01

    Luminescence dating provides a direct age estimate of the time of last exposure of quartz or feldspar minerals to light or heat and has been successfully applied to deposits, rock surfaces, and fired materials in a number of archaeological and geological settings. Sampling strategies are diverse and can be customized depending on local circumstances, although all sediment samples need to include a light-safe sample and material for dose-rate determination. The accuracy and precision of luminescence dating results are directly related to the type and quality of the material sampled and sample collection methods in the field. Selection of target material for dating should include considerations of adequacy of resetting of the luminescence signal (optical and thermal bleaching), the ability to characterize the radioactive environment surrounding the sample (dose rate), and the lack of evidence for post-depositional mixing (bioturbation in soils and sediment). Sample strategies for collection of samples from sedimentary settings and fired materials are discussed. This paper should be used as a guide for luminescence sampling and is meant to provide essential background information on how to properly collect samples and on the types of materials suitable for luminescence dating.

  2. Occurrence of benthic microbial nitrogen fixation coupled to sulfate reduction in the seasonally hypoxic Eckernförde Bay, Baltic Sea

    Directory of Open Access Journals (Sweden)

    V. J. Bertics

    2012-06-01

    Full Text Available Despite the worldwide occurrence of marine hypoxic regions, benthic nitrogen (N cycling within these areas is poorly understood and it is generally assumed that these areas represent zones of intense fixed N loss from the marine system. Sulfate reduction can be an important process for organic matter degradation in sediments beneath hypoxic waters and many sulfate-reducing bacteria (SRB have the genetic potential to fix molecular N (N2. Therefore, SRB may supply fixed N to these systems, countering some of the N lost via microbial processes such as denitrification and anaerobic ammonium oxidation. The objective of this study was to evaluate if N2-fixation, possibly by SRB, plays a role in N cycling within the seasonally hypoxic sediments from Eckernförde Bay, Baltic Sea. Monthly samplings were performed over the course of one year to measure N2-fixation and sulfate reduction rates, to determine the seasonal variations in bioturbation (bioirrigation activity and important benthic geochemical profiles, such as sulfur and N compounds, and to monitor changes in water column temperature and oxygen concentrations. Additionally, at several time points, rates of benthic denitrification were also measured and the active N-fixing community was examined via molecular tools. Integrated rates of N2-fixation and sulfate reduction showed a similar seasonality pattern, with highest rates occurring in August (approx. 22 and 880 nmol cm−3 d−1 of N and SO42−, respectively and October (approx. 22 and 1300 nmol cm−3 d−1 of N and SO42−, respectively, and lowest rates occurring in February (approx. 8 and 32 nmol cm−3 d−1 of N and SO42−, respectively. These rate changes were positively correlated with bottom water temperatures and previous reported plankton bloom activities

  3. Braidplain, floodplain and playa lake, alluvial-fan, aeolian and palaeosol facies composing a diversified lithogenetical sequence in the permian and triassic of South Devon (England)

    Science.gov (United States)

    Mader, Detlef

    The Permian and Triassic of South Devon (England) are a continental red bed sequence of very diversified lithogenetical composition. Within the thick series, the distribution of the main depositional environments being fluvial braidplain, fluvial floodplain and playa lake, alluvial fan, aeolian dune and calcrete palaeosol changes repeatedly in both horizontal and vertical direction. Significant sedimentary milieus such as aeolian dunes and calcrete palaeosols occur repeatedly within the succession, but are also lacking in several parts of the sequence. Fluvial braidplain deposits comprise conglomerates, sandstones, intraformational reworking horizons and mudstones and originate in channels and overbank plains of a braided river system. Conglomerates and sandstones are formed by migration of bars and spreading out of sheets during infilling of streams and aggradation of flats. Gravel is often enriched as lag pockets or veneers within steeper scour holes and kolk pots or on the plane floor of the watercourse. Finer-grained sandstones and mudstones are laid down by suspension settling in stagnant water bodies such as small lakes in the overbank area and residual pools in interbar depressions during low-stage or waning-flow in active channels or in abandoned streams. Spectacular bioturbation features in some sandstones with both horizontal tubes and vertical burrows testify to the colonization of the sediments at the bottom of the rivers with declining discharge and transport capacity. Intraformational reworking horizons with ghost-like remnants of degraded sandstones, mudstones and pedogenic carbonates document partially severe condensation of the sequence by removal of some facies elements from the depositional record. The occasionally occurring gravel-bearing mudstones or silty-clayey sandstones represent products of high-energy water surges overspilling the channel banks and transporting sandy and gravelly bed-load in limited amounts beyond the levee wall. The

  4. Lower Aptian Sequence at Madoz (SE Spain) in Relation to Cretaceous Anoxic Event-1a (OAE- 1a)

    Science.gov (United States)

    Gaona-Narvaez, T.; Maurrasse, F. J.; Lamolda, M. A.

    2008-05-01

    levels of fossiliferous marls (bioclasts 50%), framboidal pyrite (1-2.5%), and organic matter (5-7 %). Benthic foraminifers and bioturbation are totally absent within this interval, but there are occasional algal fragments, and very rare ostracods. In contrast to the adjacent levels, the absence of benthic foraminifers lack of bioturbation, and increased OM suggest that the black shale level clearly implies development of anoxic to dysoxic conditions within that interval. Based on the presence of D. desahyesi in subunit 1 its relationship to OAE- 1a remains ambiguous, and its occurrence may be related to a possible regional event due to the complexity of the paleogeography of that region during its tectonic development in the Early Cretaceous. Duvernois, Ch., Floquet, M., Humbel, B. 1972. La Sierra d'Aralar (Pyrénées basques Espagnoles): stratigraphie, structure. Thèse de Doctorat de Troisième cycle, Université de Dijon, 240 pp. Cherchi, A., Schroeder, R. 1998. Aptian and Albian large foraminifera at Madoz. 24° Coloquio Europeo de Micropaleontología. Libro Guía. Lamolda, M.A. Ed. 71-73p.

  5. Taphonomy of a thick Terebratula bioherm from the Pliocene of southeastern Spain

    Science.gov (United States)

    García-Ramos, Diego A.

    2015-04-01

    Brachiopods were extremely abundant during the Paleozoic era but underwent a dramatic loss of biodiversity at the Permo-Triassic boundary. The comparison of brachiopod and bivalve diversity through geological time shows that the latter were the most successful counterpart at best recovering from mass extinction events. Nonetheless, there are cases where Post-Paleozoic brachiopods stand out as the dominant marine benthos in particular environments, forming paucispecific brachiopod-dominated bioherms. This note describes an example of shallow-water brachiopod bioherm dominated by the terebratulid Terebratula calabra. The shell bed is found in mixed siliciclastic-temperate carbonate deposits of late Early Pliocene age nearby Águilas (southeastern Spain). This unique brachiopod concentration may be helpful to understand the particular success of large-sized brachiopods like Terebratula in Cenozoic environments typically dominated by bivalves. The bioherm attains 1.5 meters in thickness and crops out along a band up to 140 meters wide. The lithology consists of bioturbated fine-grained sands containing poorly sorted bioclasts, mostly fragments of Terebratula. This shell bed also records a diverse fauna, including five brachiopod genera, pectinids (4 genera), oysters (3 genera), in addition to rare gastropods, echinoids, bryozoans, etc. The density and sorting of bioclasts is laterally variable, and the biofabrics range from loosely dispersed to densely-packed, including examples of concave-up vertical stacking and nesting of shells. Most of the fragments of Terebratula preserve the posterior part of the shell only. These fragments generally display corrasion (rounded fractured margins, rounded to completely missing symphytium), bioerosion (prevailing the ichnogenera Entobia, Gnathichnus and Podichnus) and encrustation (mainly by bryozoans, Ancistrocrania, and Pododesmus). The good preservation of Pododesmus contrasts with that of most fragments of Terebratula, although

  6. The recent marine sedimentary record of Baranof Island, Southeast Alaska - implications for paleoclimate reconstructions

    Science.gov (United States)

    Addison, J. A.; Finney, B. P.; Jaeger, J. M.; Stoner, J. S.; Norris, R. D.; Hangsterfer, A.

    2011-12-01

    Modern and paleoclimate studies suggest a correlation between Pacific decadal climate variability and marine ecosystem productivity, but are generally limited by either short periods of observation or low temporal resolution. Long, annually resolved paleoclimate time-series data are thus critical for assessing this correlation and understanding the full range of Pacific climate variability and its impacts. Baranof Island is located in the Alexander Archipelago of Southeast Alaska, and contains many temperate ice-free fjords with shallow sills that enhance organic matter preservation by restricting oxygenation of bottom waters. Multicore samples EW0408-32MC and 43MC were recovered from two fjords on Baranof Island, and analyzed to determine how recent sedimentation patterns relate to the instrument record as a first step towards reconstructing high-latitude Pacific climate at annual timescales. A combination of radiometric 137Cs and excess 210Pb geochronometry, 3D computerized tomography (CT), and high-resolution Avaatech scanning XRF geochemical analyses were used to investigate this relationship. Scanning XRF data were collected every 2 mm on core 32MC, while 43MC was measured at 0.2 mm intervals. Core 32MC is composed of a diffusely laminated to bioturbated clay with a maximum apparent steady-state sedimentation rate of ~5±1 mm/yr, while core 43MC is a strongly laminated diatom ooze with a maximum apparent sedimentation rate of ~6±0.5 mm/yr. Using conservative estimates of accumulation to assess basal ages of the cores yields approximately ~AD 1930 for 32MC, and ~AD 1900 for 43MC. Scanning XRF centered natural log-ratio transformed [clr] element intensities indicate 32MC is controlled by a balance between detrital (Al, Si, K, Ti, Fe, and Ca) and biogenic components (S and Br), and isolated peaks in clr Ca data correspond with CT-visible shell debris. Core 43MC is more complex, with both XRF and CT scans indicating four distinct lithologies: (i) millimeter

  7. The truth is out there: measured, calculated and modelled benthic fluxes.

    Science.gov (United States)

    Pakhomova, Svetlana; Protsenko, Elizaveta

    2016-04-01

    In a modern Earth science there is a great importance of understanding the processes, forming the benthic fluxes as one of element sources or sinks to or from the water body, which affects the elements balance in the water system. There are several ways to assess benthic fluxes and here we try to compare the results obtained by chamber experiments, calculated from porewater distributions and simulated with model. Benthic fluxes of dissolved elements (oxygen, nitrogen species, phosphate, silicate, alkalinity, iron and manganese species) were studied in the Baltic and Black Seas from 2000 to 2005. Fluxes were measured in situ using chamber incubations (Jch) and at the same time sediment cores were collected to assess the porewater distribution at different depths to calculate diffusive fluxes (Jpw). Model study was carried out with benthic-pelagic biogeochemical model BROM (O-N-P-Si-C-S-Mn-Fe redox model). It was applied to simulate biogeochemical structure of the water column and upper sediment and to assess the vertical fluxes (Jmd). By the behaviour at the water-sediment interface all studied elements can be divided into three groups: (1) elements which benthic fluxes are determined by the concentrations gradient only (Si, Mn), (2) elements which fluxes depend on redox conditions in the bottom water (Fe, PO4, NH4), and (3) elements which fluxes are strongly connected with organic matter fate (O2, Alk, NH4). For the first group it was found that measured fluxes are always higher than calculated diffusive fluxes (1.5bioturbation, bioirrigation and advection should be taken into account. For the second group measured fluxes can be both much lower (practically absent) and much higher than calculated diffusive fluxes (0.01

  8. Differential severity of Permian Triassic environmental changes on Tethyan shallow-water carbonate platforms

    Science.gov (United States)

    Weidlich, Oliver; Bernecker, Michaela

    2007-01-01

    Significantly different Guadalupian-Late Triassic patterns are observed in the evolution of attached and isolated carbonate platforms of the southwestern Tethys (Oman Mountains). Close to the rim of the attached Arabian platform, carbonates of the Saiq and Mahil Formations reveal an almost complete Permian-Triassic sedimentary record. Guadalupian-Changhsingian 3rd order sequences consist of fossiliferous transgressive systems tracts and monotonous highstand systems tracts with mud/wackestone and coral bafflestone. The youngest Changhsingian beds are bioturbated floatstone with crinoids, sponges and bryozoans. All sediments indicate a healthy, tropical carbonate production. Above, a unique facies change begins with a pyrite-encrusted omission surface. Greenish mudstone rich in authigenic pyrite infills the relief of the unconformity and is overlain by clastic sediment and by laminated, microbialite-bearing carbonate. Unfossiliferous sediments and seafloor cements indicate a change in carbonate production towards abiotic processes. Prevailing anoxic conditions were interrupted by seven oxic event beds, as indicated either by low-diversity and small-sized ichnotaxa or by shell beds with low-diversity bivalve and crinoid assemblages. By comparison with published data, the described sedimentary sequence can be assigned to the Changhsingian-earliest Griesbachian. Beginning probably with the Anisian, bioturbated Griesbachian-Dienerian recovery period and the unconformity below to the latest grain-supported sediment textures mark the return to biogenic tropical carbonate production under oxic conditions. The Middle-Late Triassic carbonate platform consists of stacked high-frequency shallowing upward cycles. By contrast, carbonate production of Neo-Tethyan isolated platforms was discontinuous and interrupted by a large gap. Guadalupian deposits of the Al Jil Formation consist of bioclastic limestone typical of a tropical carbonate production. The uppermost bed, an

  9. Redox-sensitive element mobility in mid-Miocene clays from Unit II of Hole M0027A, the New Jersey Shallow Shelf (IODP Expedition 313)

    Science.gov (United States)

    McGrath, A. G.; Inwood, J.; Morgan, S.; Davies, S.; Foster, H.

    2012-12-01

    The geochemistry of an unusual seven metre interval of distinctive color-banded clays of Serravallian age has been analysed. This interval is from Hole M0027A, the most landward of the three holes cored during IODP Expedition 313. The clays lie immediately above a key surface (the m4.1 reflector), with the available age constraints indicating deposition of the clays during a time of global cooling and major sea level change. The behaviour of major and trace elements from this interval will help to elucidate the paleoenvironmental conditions and nature of shelf sedimentation during this time. Conventional XRF analysis reveals enrichments in the redox-sensitive trace elements As, Co, Sc, V, Cr, the LREEs La, Ce and Nd, and also Ba and Cs throughout this interval. The enrichment of Co, Sc and V is particularly notable, being much higher than both average New Jersey clay and North Atlantic Average Shale Composition (NASC). Examination of cut cores from Unit II reveals that the enriched zone consists of a sequence of cm- to metre-scale packages of banded clays, alternating with thinner, paler homogeneous clays. The cm-scale color-bands are interpreted to represent diagenetic features due to the mobilisation and relocation of redox-sensitive elements in the sediments during, or shortly after, deposition. Manganese and iron peaks likely reflect previous locations of the manganese redox boundary in the sediment - i.e. they represent relict or paleo-redox fronts. The dark bands are very organic rich, show little bioturbation and contain pyrite or possibly authigenic greigite. They also consistently correspond to peaks in magnetic susceptibility. The homogeneous clays are extensively mottled due to bioturbation, contain little organic matter and generally correspond to lows in magnetic susceptibility. The dark bands are organic-rich clays that are cyclically intercalated with organic-poor lighter colored sediments. The degradation and oxidation of organic matter likely

  10. Testing hillslope transport models in the Susquehanna Shale Hills Critical Zone Observatory

    Science.gov (United States)

    West, N.; Kirby, E.

    2012-12-01

    Since the recognition that hillslope gradients adjust to balance downslope fluxes with production of regolith, workers have sought to understand the quantitative relationship between mass fluxes and hillslope topography. For much of the last century, it has been hypothesized that the downslope flux of regolith is linearly proportional to the local hillslope gradient, while the rate of surface lowering is linearly proportional to hillslope curvature. The development of new isotopic methods and the increasing availability of high resolution topographic data sets allows for testing of these simple transport models in a variety of landscapes. With the application of these tools, workers have learned that the simple linear transport rules do not always adequately describe the behavior of hillslopes. Our study presents a preliminary test of simple geomorphic models, using a combination of meteoric 10Be derived regolith erosion and flux rates and high resolution topographic data, collected using airborne laser swath mapping. Our field area, the Susquehanna Shale Hills Critical Zone Observatory (SSHO), located only 75 km due south of the Laurentide ice margin in central Pennsylvania, serves as a compelling staging ground for investigating process control on erosion, as local mechanisms for sediment transport have transitioned from freeze-thaw processes to bioturbation. Local hillslope gradients and ridgetop curvature values were extracted from a 1 m resolution digital elevation model for use in flux calculations and model testing. Meteoric 10Be concentrations in regolith along two hillslopes in SSHO were used to measure downslope flux rates, and revealed a systematic increase in flux rates from ~ 5 cm2/y near the ridge tops to ~ 30 cm2/y near the toe slopes. Comparing our measured flux rates with simple geomorphic transport rules suggests a surprising result - at SSHO, fluxes of regolith are not linearly correlated with topographic gradient. However, if we incorporate the

  11. Radiocarbon Dating and age Inversions in Lake Chapala Late Holocene Sediments, Western Mexico.

    Science.gov (United States)

    Zarate-Del Valle, P.; Israde-Alcantara, I.; Ramírez-Sánchez, H.; Gómez-Salazar, S.; Ríos-Donato, N.

    2006-12-01

    Neotectonic Lake Chapala, the major Mexican freshwater reservoir lies at the north and northeast of the Citala Rift and is linked to history of the active Plio-Quaternary Transmexican Volcanic Belt geological province. Eight radiocarbon 14C dates were obtained on shallow sediment samples from a gravity corer (T46) of 5 cm in diameter and 1.7 m long. The core was collected from the western sector of Lake Chapala (103° 15.43' W, 20° 14.45' N) at water depth of 3.7 m (june 2000). In general, shallow sediments (Lake Chapala are dark and silty with granulometric median ranging from 10 to 50 μm. Major oxides in sediments are: SiO2 (54.05%), Al2O3 (18.94%), Fe2O3 (6.75%) and CaO (2.57%). The major mineralogical composition of sediments is as follows: plagioclases (25.86%), quartz (20.92%), clays (38.5%), carbonates (2.99%) and TiO2 (1.05%). Radiocarbon ages were measured by accelerator mass spectrometry (AMS) and were obtained through the organic carbon fraction extracted from the bulk sediment samples sliced every 20 cm taken from the whole core. Stratigraphically ordered from highest to lowest, the eight ages reported are: 1) 2,000 ±40 yr on sediments at 30 cm deep; 2) 1,920 ±35 yr on sediments at 50 cm deep; 3) 1,900 ±35 yr on sediments at 70 cm deep; 4) 2,080 ±35 yr on sediments at 90 cm deep; 5) 2,090 ±50 yr on sediments at 110 cm deep; 6) 2,190 ±35 yr on sediments at 130 cm deep; 7) 2,050 ±35 yr on sediments at 150 cm deep and, 8) 1,500 ±35 yr on sediments at 170 cm deep. From the top until 70 cm and from 130 to bottom we observe two age inversions; the interval apparently with no age inversions is from 70cm to 130cm. As it is known the age inversions observed may be due to a) ancient carbon being incorporated into the sediment during deposition; b) unrecognized bioturbation, c) Postdepositional alteration and, d) variations in the apparent geological ages of the different chemical phases comprising the total sediment. Basically, the factors probably

  12. Stratigraphic characterization of the Anthropocene: a progress report

    Science.gov (United States)

    Zalasiewicz, Jan

    2014-05-01

    Rapid and large-scale anthropogenic changes have led to the concept that we are now living through the beginning of the Anthropocene Epoch - an interval of geological time dominated by human influence. The term was proposed little more than a decade ago by Paul Crutzen, the Nobel Prize-winning atmospheric chemist, and has since been widely used - and sharply debated. Its stratigraphic analysis needs considering the various kinds of historical and environmental change in terms of geological - or more precisely stratigraphic - change. Lithostratigraphic change, for instance, is strikingly represented by the spread of the 'urban stratum', the refashioning of sand, clay and limestone into our buildings, foundations and transport systems. Biostratigraphic changes include the ongoing mass extinction event and the effect of invasive species (while deep human-made bioturbation is a novel aspect the fossil record). Chemostratigraphic changes include the reshaping of the Earth's natural carbon, phosphorus and nitrogen cycles. As regards the potential formalizing of the Anthropocene, one question to be pursued relates to the chronostratigraphic definition of the phenomena involved: that is, given that many of these transformations are diachronous on human timescales, can an Anthropocene Series, with a synchronous time boundary, be characterized and mapped across the Earth's surface? Efforts to answer this question (Williams et al. 2011; Waters et al., in press) should help in the understanding of the Anthropocene within its geological context, and also in exploring the stratigraphic relation between time and rock generally at very fine stratigraphic timescales. Waters, C.W., Zalasiewicz, J.A., Williams, M., Ellis, M. & Snelling, A. In press. A Stratigraphical Basis for the Anthropocene. Geological Society of London, Special Publication. Williams, M., Zalasiewicz, J., Haywood, A. & Ellis M. (eds) 2011. The Anthropocene: a new epoch of geological time? Philosophical

  13. Geomorphic controls on biological soil crust distribution: A conceptual model from the Mojave Desert (USA)

    Science.gov (United States)

    Williams, Amanda J.; Buck, Brenda J.; Soukup, Deborah A.; Merkler, Douglas J.

    2013-08-01

    Biological soil crusts (BSCs) are bio-sedimentary features that play critical geomorphic and ecological roles in arid environments. Extensive mapping, surface characterization, GIS overlays, and statistical analyses explored relationships among BSCs, geomorphology, and soil characteristics in a portion of the Mojave Desert (USA). These results were used to develop a conceptual model that explains the spatial distribution of BSCs. In this model, geologic and geomorphic processes control the ratio of fine sand to rocks, which constrains the development of three surface cover types and biogeomorphic feedbacks across intermontane basins. (1) Cyanobacteria crusts grow where abundant fine sand and negligible rocks form saltating sand sheets. Cyanobacteria facilitate moderate sand sheet activity that reduces growth potential of mosses and lichens. (2) Extensive tall moss-lichen pinnacled crusts are favored on early to late Holocene surfaces composed of mixed rock and fine sand. Moss-lichen crusts induce a dust capture feedback mechanism that promotes further crust propagation and forms biologically-mediated vesicular (Av) horizons. The presence of thick biogenic vesicular horizons supports the interpretation that BSCs are long-lived surface features. (3) Low to moderate density moss-lichen crusts grow on early Holocene and older geomorphic surfaces that display high rock cover and negligible surficial fine sand. Desert pavement processes and abiotic vesicular horizon formation dominate these surfaces and minimize bioturbation potential. The biogeomorphic interactions that sustain these three surface cover trajectories support unique biological communities and soil conditions, thereby sustaining ecological stability. The proposed conceptual model helps predict BSC distribution within intermontane basins to identify biologically sensitive areas, set reference conditions for ecological restoration, and potentially enhance arid landscape models, as scientists address impacts

  14. Trace fossil evidence for late Permian shallow water condition in Guryul ravine, Kashmir, India

    Science.gov (United States)

    Parcha, Suraj; Horacek, Micha; Krystyn, Leopold; Pandey, Shivani

    2015-04-01

    The present study is focused on the Late Permian (Changhsingian) succession, present in the Guryul ravine, Kashmir Basin. The basin has a complete Cambro-Triassic sequence and thus contains a unique position in the geology of Himalaya. The Guryul Ravine Permian mainly comprises of mixed siliciclastic-carbonate sediments deposited in a shallow-shelf or ramp setting. The present assemblage of Ichnofossils is the first significant report of trace fossils in the Guryul ravine since early reports in the 1970s. The Ichnofossils reported from this section include: Diplichnites, Dimorphichnus, Monomorphichnus, Planolites, Skolithos along with burrow, scratch marks and annelid worm traces?. The ichnofossils are mainly preserved in medium grain sandstone-mudstone facies. The Ichnofossils are widely distributed throughout the section and are mostly belonging to arthropods and annelid origin, showing behavioral activity, mainly dwelling and feeding, and evidence the dominant presence of deposit feeders. The vertical to slightly inclined biogenic structures are commonly recognized from semi-consolidated substrate which are characteristic features of the near shore/foreshore marine environment, with moderate to high energy conditions. The topmost layer of silty shale contains trace fossils like Skolithos and poorly preserved burrows. The burrow material filled is same as that of host rock. The studied Zewan C and D sequence represents the early to late part of the Changhsingian stage, from 40 to 5 m below the top of Zewan D member with bioturbation still evident in some limestone layers till 2 metres above. No trace fossils could be recognized in the topmost 3 m beds of Zewan D due to their gliding related amalgamated structure. The widespread distribution of traces and their in situ nature will be useful for interpretation of the paleoecological and paleoenvironmental conditions during the late Permian in the Guryul ravine of Kashmir.

  15. Distribution of gamma-emitting radionuclides in surface subtidal sediments near the Sellafield plant

    Energy Technology Data Exchange (ETDEWEB)

    Jones, D.G.; Roberts, P.D.; Miller, J.M.

    1988-08-01

    Detailed distributions of total gamma activity, /sup 137/Cs, /sup 106/Ru and /sup 95/Zr + /sup 95/Nb in surface seabed sediments near the Sellafield plant are presented. The results are derived from a towed seabed gamma-ray spectrometer survey in September, 1982. All the distributions are similar, with contours of equal activity parallel to the coast defining a 'ridge' of higher activity which is displaced northwards relative to the outfall. Nuclide concentrations decrease with increasing distance from Sellafield; rates of decrease being in the order Zr + Nb > Ru > Cs. This can be related to the levels of the nuclides discharged, their sorption characteristics and their half lives. The pattern of seabed activity seems to have been fairly stable over the period 1978-85, but there is evidence of a small northward shift. Concentrations of /sup 137/Cs and /sup 106/Ru in 1985 were considerably lower than in 1978 or 1982. This is explicable in terms of the fall in discharge levels allied, in the case of Ru, to its short half life and, for Cs, the desorption observed in laboratory experiments. Nuclide ratios in sediment samples yield apparent transit times for the transport of nuclides in the survey area of 1.7-3.7 years. These times are generally greater than those obtained from sediments in the more distant Solway Firth and Ravenglass Estuary. It is suggested that they reflect fairly intense bioturbation causing mixing of relatively recent effluent with that from earlier discharges. This is supported by structures observed in X-radiographs of box cores, an abundant burrowing benthos and by interpretations of nuclide profiles and radiocarbon dating of sediment cores by other workers. A lag effect, of up to two years across the survey area, appears to be superimposed on that due to mixing.

  16. Effects of ghost shrimp on zinc and cadmium in sediments from Tampa Bay, FL

    Science.gov (United States)

    Klerks, P.L.; Felder, D.L.; Strasser, K.; Swarzenski, P.W.

    2007-01-01

    This study investigated the effects that ghost shrimp have on the distribution of metals in sediment. We measured levels of HNO3-extractable zinc and cadmium in surface sediment, in ghost shrimp burrow walls and in sediment ejected by the ghost shrimp from their burrows, at five sandy intertidal sites in Tampa Bay. Ghost shrimp densities and their rate of sediment ejection were also quantified, as were sediment organic content and silt + clay content. Densities of ghost shrimp (Sergio trilobata and Lepidophthalmus louisianensis) averaged 33/m2 at our sites, and they ejected sediment at an average rate of 28 g/burrow/day. Levels of both Zn and Cd were significantly higher in burrow walls than in surface sediments. Sediment ejected by the shrimp from their burrows had elevated levels of Zn (relative to surface sediments) at one of the sites. Sediment organic content and silt + clay content were higher in burrow-wall sediments than in ejected sediment, which in turn tended to have values above those of surface sediments. Differences in levels of HNO3-extractable Zn and Cd among sediment types may be a consequence of these sediments differing in other physiochemical characteristics, though the differences in metal levels remained statistically significant for some sites after correcting for differences in organic content and silt + clay content. We conclude that the presence of ghost shrimp burrows contributes to spatial heterogeneity of sedimentary metal levels, while the ghost shrimp bioturbation results in a significant flux of metals to the sediment surface and is expected to decrease heterogeneity of metal levels in sedimentary depth profiles.

  17. Pronounced Climatic and Environmental Changes in the South West Pacific Ocean Following the End-Cretaceous Extinction Event

    Science.gov (United States)

    Crouch, E. M.; Taylor, K. W.; Willumsen, P. S.; Hollis, C. J.; Pancost, R. D.

    2014-12-01

    Dinoflagellate cyst assemblages from Cretaceous/Paleogene (K/Pg) boundary sections in eastern New Zealand record an alternating succession of pronounced abundance changes in two peridinioid (primarily heterotrophic) genera following the K/Pg boundary event. In Canterbury and East Coast Basin sections, two phases of abundant Trithyrodinium evittii, the first immediately following the K/Pg boundary, are interposed by two acme intervals of Palaeoperidinium pyrophorum. While several lines of evidence suggest T. evittii was a warm-water species and P. pyrophorum flourished in cooler oceanic conditions, robust temperature records have not been available from these K/Pg boundary sections. We have completed sea surface temperature (SST) reconstructions, based on glycerol dialkyl glycerol tetraether (GDGT) distributions, at mid-Waipara River, North Canterbury, from ~1 m below to 20 m above the K/Pg boundary. Changes in GDGT distribution across the K/Pg boundary indicates warming of 2-3°C, regardless of which TEX86-based proxy is used, coincident with the interval of abundant T. evittii. Detailed climatic records at the K/Pg boundary layer are hampered by intense bioturbation. Above an unconformity (at 23 cm) notable shifts in GDGT distribution indicates pronounced cooling, yielding SST estimates that are 7°C lower than the uppermost Cretaceous. The acme of P. pyrophorum corresponds with these cooler SSTs, and an unusual increase in the proportion of GDGT-2 in this interval can be attributed to cool water upwelling. The P. pyrophorum acme is also documented in distal diatom-rich siliceous sediments in Marlborough, where siliceous microfossils and element geochemistry indicate cool-water upwelling in the basal Paleocene. The second phase of abundant T. evittii, at ~2 m in Waipara, coincides with an interval of more stable SSTs that are comparable to the uppermost Cretaceous. Further discussion of the TEX86-based SST proxy and GDGT distributions will be provided in the

  18. Consequences of increasing hypoxic disturbance on benthic communities and ecosystem functioning.

    Directory of Open Access Journals (Sweden)

    Anna Villnäs

    Full Text Available Disturbance-mediated species loss has prompted research considering how ecosystem functions are changed when biota is impaired. However, there is still limited empirical evidence from natural environments evaluating the direct and indirect (i.e. via biota effects of disturbance on ecosystem functioning. Oxygen deficiency is a widespread threat to coastal and estuarine communities. While the negative impacts of hypoxia on benthic communities are well known, few studies have assessed in situ how benthic communities subjected to different degrees of hypoxic stress alter their contribution to ecosystem functioning. We studied changes in sediment ecosystem function (i.e. oxygen and nutrient fluxes across the sediment water-interface by artificially inducing hypoxia of different durations (0, 3, 7 and 48 days in a subtidal sandy habitat. Benthic chamber incubations were used for measuring responses in sediment oxygen and nutrient fluxes. Changes in benthic species richness, structure and traits were quantified, while stress-induced behavioral changes were documented by observing bivalve reburial rates. The initial change in faunal behavior was followed by non-linear degradation in benthic parameters (abundance, biomass, bioturbation potential, gradually impairing the structural and functional composition of the benthic community. In terms of ecosystem function, the increasing duration of hypoxia altered sediment oxygen consumption and enhanced sediment effluxes of NH(4(+ and dissolved Si. Although effluxes of PO(4(3- were not altered significantly, changes were observed in sediment PO(4(3- sorption capability. The duration of hypoxia (i.e. number of days of stress explained a minor part of the changes in ecosystem function. Instead, the benthic community and disturbance-driven changes within the benthos explained a larger proportion of the variability in sediment oxygen- and nutrient fluxes. Our results emphasize that the level of stress to the

  19. Depositional environment and organic geochemistry of the Upper Permian Ravenfjeld Formation source rock in East Greenland

    Energy Technology Data Exchange (ETDEWEB)

    Christiansen, F.G.; Piasecki, S.; Stemmerik, L. (Geologoical Survey of Greenland, Copenhagen (Denmark)); Telnaes, N. (Norsk Hydro Research Center, Bergen (Norway))

    1993-09-01

    The Upper Permian Ravnefjeld Formation in East Greenland is composed of shales that laterally pass into carbonate buildups and platforms of the Wegener Halvo Formation. The Ravnefjeld Formation is subdivided into five units that can be traced throughout the Upper Permian depositional basin. Two of the units are laminated and organic rich and were deposited under anoxic conditions. They are considered good to excellent source rocks for liquid hydrocarbons with initial average TOC (total organic carbon) values between 4 and 5% and HI (hydrogen index) between 300 and 400. The cumulative source rocks are separated and enclosed by three units of bioturbated siltstone with a TOC of less than 0.5% and an HI of less than 100. These siltstones were deposited under relatively oxic conditions. The organic geochemistry of the source rocks is typical for marine source rocks with some features normally associated with carbonate/evaporite environments [low Pr/Ph (pristane/phytane), low CPI (carbon preference index), distribution of tricyclic and pentacyclic terpanes]. The establishment of anoxic conditions and subsequent source rock deposition was controlled by eustatic sea level changes. The subenvironment (paleogeographic setting, influx of carbonate material, water depth, salinity) has some influence on a number of bulk parameters [TOC-HI relations, TOC-TS (total sulfur) relations] and, in particular, biomarker parameters such as Pr/Ph and terpane ratios. All the basal shales or shales in the vicinity of carbonate buildups of platforms are characterized by low Pr/Ph, high C[sub 23] tricyclic terpanes, and high C[sub 35] and C[sub 33] hopanes. 52 refs., 20 figs., 3 tabs.

  20. Infaunal community responses to a gradient of trawling disturbance and a long-term Fishery Exclusion Zone in the Southern Tyrrhenian Sea

    Science.gov (United States)

    Mangano, M. Cristina; Kaiser, Michel J.; Porporato, Erika M. D.; Lambert, Gwladys I.; Rinelli, Paola; Spanò, Nunziacarla

    2014-03-01

    Historically the majority of Mediterranean trawl fisheries occur on the continental shelf with a smaller proportion focused on the shelf slope and deep sea areas. Understanding how trawl fisheries affect the wider ecosystem is an important component of the ecosystem-based approach to fisheries management. In this context the current study examined the impact of the otter trawl fishery on the infaunal communities found on the continental shelf and upper slope off the coast of Sicily and Calabria, Italy. A total of thirty six sites were sampled across a gradient of fishing intensity and from within a large bay from which trawling has been excluded for 22 years. Fishing intensities were ascertained post-hoc from vessel monitoring system data. Seabed characteristics of the sites studied were uniform across the continental shelf and slope areas that were studied, such that the only factor that varied was fishing intensity. The density index (DI) and total number of species (S) were significantly higher in the fishery closure area compared with other continental shelf sites. In particular, bioturbating decapod fauna occurred only within the fishery closure area. Fished sites were dominated primarily by burrowing deposit feeding worms, small bivalves and scavenging biota. In contrast, the response to fishing on the upper slope was less clear. This observation was treated with caution as the power to detect fishing effects was lower for the upper slope sites as a result of possible illegal fishing that had compromised two of the four replicate sites within the closed area. While the present study was able to quantify the effect of the demersal trawl fleet on the benthic infauna of the continental shelf, the effects of trawling on the upper shelf slope remain unclear and warrant further study.

  1. Insights into site formation at Rose Cottage Cave, South Africa, based on the analysis of sediment peels

    Science.gov (United States)

    Kloos, Peter; Miller, Christopher E.; Kritikakis, Panagiotis; Wadley, Lyn

    2016-04-01

    Rose Cottage Cave (RCC), in South Africa, has been a key site for explaining the origins of modern human behaviour and movement of early modern humans out of Africa. Nine sediment peels were made previously from the profile sections, preserving original materials that provide a record of cultural and environmental change during the late Pleistocene and Holocene. Here, we present the preliminary results of the study of the RCC sediment peels which aims to investigate site formation processes and the implications for site interpretation. Methods used include micromorphology and Fourier Transform Infrared spectroscopy coupled with detailed observations of the peels. The predominance of geogenic processes is demonstrated by the abundance of silt- and sand-sized quartz grains, which entered the site primarily through a crevice at the back of the cave. RCC lacks rich anthropogenic deposits as noted at other Middle Stone Age sites in southern Africa, but anthropogenic input to the sediment is indicated by the presence of charcoal, burnt bone, lithic fragments, fat-derived char and ashes. Clay coating fragments and chaotic microstructures demonstrate that bioturbation and colluvial reworking homogenised much of the deposit and may explain the absence of preserved bedding and rarity of combustion features. Downward movement of water through the sequence, indicated by clay coatings, is the likely cause for poor bone preservation and near lack of ashes at the site, as well as fluctuations in dose rate that have complicated luminescence dating studies. Evidence for diagenesis at the site is in the form of secondary apatite and gypsum. Sedimentary structures such as channel lag deposits and (silt and sand) laminae observed in peels dating between 60 and 35 ka BP suggest a high-energy sedimentary environment, which experienced flooding events that eroded underlying deposits and deposited large volumes of sediment. This explains why some of the post-Howiesons Poort layers contain

  2. Community structure and activity of a highly dynamic and nutrient-limited hypersaline microbial mat in Um Alhool Sabkha, Qatar.

    Directory of Open Access Journals (Sweden)

    Roda Al-Thani

    Full Text Available The Um Alhool area in Qatar is a dynamic evaporative ecosystem that receives seawater from below as it is surrounded by sand dunes. We investigated the chemical composition, the microbial activity and biodiversity of the four main layers (L1-L4 in the photosynthetic mats. Chlorophyll a (Chl a concentration and distribution (measured by HPLC and hyperspectral imaging, respectively, the phycocyanin distribution (scanned with hyperspectral imaging, oxygenic photosynthesis (determined by microsensor, and the abundance of photosynthetic microorganisms (from 16S and 18S rRNA sequencing decreased with depth in the euphotic layer (L1. Incident irradiance exponentially attenuated in the same zone reaching 1% at 1.7-mm depth. Proteobacteria dominated all layers of the mat (24%-42% of the identified bacteria. Anoxygenic photosynthetic bacteria (dominated by Chloroflexus were most abundant in the third red layer of the mat (L3, evidenced by the spectral signature of Bacteriochlorophyll as well as by sequencing. The deep, black layer (L4 was dominated by sulfate reducing bacteria belonging to the Deltaproteobacteria, which were responsible for high sulfate reduction rates (measured using 35S tracer. Members of Halobacteria were the dominant Archaea in all layers of the mat (92%-97%, whereas Nematodes were the main Eukaryotes (up to 87%. Primary productivity rates of Um Alhool mat were similar to those of other hypersaline microbial mats. However, sulfate reduction rates were relatively low, indicating that oxygenic respiration contributes more to organic material degradation than sulfate reduction, because of bioturbation. Although Um Alhool hypersaline mat is a nutrient-limited ecosystem, it is interestingly dynamic and phylogenetically highly diverse. All its components work in a highly efficient and synchronized way to compensate for the lack of nutrient supply provided during regular inundation periods.

  3. Acid-base physiology response to ocean acidification of two ecologically and economically important holothuroids from contrasting habitats, Holothuria scabra and Holothuria parva.

    Science.gov (United States)

    Collard, Marie; Eeckhaut, Igor; Dehairs, Frank; Dubois, Philippe

    2014-12-01

    Sea cucumbers are dominant invertebrates in several ecosystems such as coral reefs, seagrass meadows and mangroves. As bioturbators, they have an important ecological role in making available calcium carbonate and nutrients to the rest of the community. However, due to their commercial value, they face overexploitation in the natural environment. On top of that, occurring ocean acidification could impact these organisms, considered sensitive as echinoderms are osmoconformers, high-magnesium calcite producers and have a low metabolism. As a first investigation of the impact of ocean acidification on sea cucumbers, we tested the impact of short-term (6 to 12 days) exposure to ocean acidification (seawater pH 7.7 and 7.4) on two sea cucumbers collected in SW Madagascar, Holothuria scabra, a high commercial value species living in the seagrass meadows, and H. parva, inhabiting the mangroves. The former lives in a habitat with moderate fluctuations of seawater chemistry (driven by day-night differences) while the second lives in a highly variable intertidal environment. In both species, pH of the coelomic fluid was significantly negatively affected by reduced seawater pH, with a pronounced extracellular acidosis in individuals maintained at pH 7.7 and 7.4. This acidosis was due to an increased dissolved inorganic carbon content and pCO2 of the coelomic fluid, indicating a limited diffusion of the CO2 towards the external medium. However, respiration and ammonium excretion rates were not affected. No evidence of accumulation of bicarbonate was observed to buffer the coelomic fluid pH. If this acidosis stays uncompensated for when facing long-term exposure, other processes could be affected in both species, eventually leading to impacts on their ecological role.

  4. Organic carbon burial in fjords: Terrestrial versus marine inputs

    Science.gov (United States)

    Cui, Xingqian; Bianchi, Thomas S.; Savage, Candida; Smith, Richard W.

    2016-10-01

    Fjords have been identified as sites of enhanced organic carbon (OC) burial and may play an important role in regulating climate change on glacial-interglacial timescales. Understanding sediment processes and sources of sedimentary OC are necessary to better constrain OC burial in fjords. In this study, we use Fiordland, New Zealand, as a case study and present data on surface sediments, sediment down-cores and terrestrial end-members to examine dynamics of sediments and the sources of OC in fjord sediments. Sediment cores showed evidence of multiple particle sources, frequent bioturbation and mass-wasting events. A multi-proxy approach (stable isotopes, lignin-phenols and fatty acids) allowed for separation of marine, soil and vascular plant OC in surface sediments. The relationship between mass accumulation rate (MAR) and OC contents in fjord surface sediments suggested that mineral dilution is important in controlling OC content on a global scale, but is less important for specific regions (e.g., New Zealand). The inconsistency of OC budgets calculated by using MAR weighted %OC and OC accumulation rates (AR; 6 vs 21-31 Tg OC yr-1) suggested that sediment flux in fjords was likely underestimated. By using end-member models, we propose that 55% to 62% of total OC buried in fjords is terrestrially derived, and accounts for 17 ± 12% of the OCterr buried in all marine sediments. The strong correlation between MAR and OC AR indicated that OC flux will likely decrease in fjords in the future with global warming due to decrease in sediment flux caused by glacier denudation.

  5. Replacement of benthic communities in two Neoproterozoic-Cambrian subtropical-to-temperate rift basins, High Atlas and Anti-Atlas, Morocco

    Science.gov (United States)

    Clausen, Sébastien; Álvaro, J. Javier; Zamora, Samuel

    2014-10-01

    The ‘Cambrian explosion’ is often introduced as a major shift in benthic marine communities with a coeval decline of microbial consortia related to the diversification of metazoans and development of bioturbation (‘Agronomic Revolution’). Successive community replacements have been reported along with ecosystem diversification and increase in guild complexity from Neoproterozoic to Cambrian times. This process is recorded worldwide but with regional diachroneities, some of them directly controlled by the geodynamic conditions of sedimentary basins. The southern High Atlas and Anti-Atlas of Morocco record development of two rifts, Tonian (?) - early Cryogenian and latest Ediacarian-Cambrian in age, separated by the onset of the Pan-African Orogeny. This tectonically controlled, regional geodynamic change played a primary control on pattern and timing of benthic ecosystem replacements. Benthic communities include microbial consortia, archaeocyathan-thromboid reefal complexes, chancelloriid-echinoderm-sponge meadows, and deeper offshore echinoderm-dominated communities. Microbial consortia appeared in deeper parts of the Tonian (?) - early Cryogenian fluvio-deltaic progradational rift sequences, lacustrine environments of the Ediacaran Volcanic Atlasic Chain (Ouarzazate Supergroup) and the Ediacaran-Cambrian boundary interval, characterized by the peritidal-dominated Tifnout Member (Adoudou Formation). They persisted and were largely significant until Cambrian Age 3, as previous restricted marine conditions precluded the immigration of shelly metazoans in the relatively shallow epeiric parts of the Cambrian Atlas Rift. Successive Cambrian benthic communities were replaced as a result of distinct hydrodynamic and substrate conditions, which allow identification of biotic (e.g., antagonistic relationships between microbial consortia and echinoderms, and taphonomic feedback patterns in chancelloriid-echinoderm-sponge meadows) and abiotic (e.g., rifting

  6. Towards an improved modeling of chemical weathering in the SoilGen soil evolution model

    Science.gov (United States)

    Opolot, Emmanuel; Finke, Peter

    2014-05-01

    As the need for soil information particularly in the fields of agriculture, land evaluation, hydrology, biogeochemistry and climate change keeps increasing, models for soil evolution are increasingly becoming valuable tools to provide such soil information. Although still limited, such models are progressively being developed. The SoilGen model is one of such models with capabilities to provide soil information such as soil texture, pH, base saturation, organic carbon, CEC, etc over multi-millennia time scale. SoilGen is a mechanistic water flow driven pedogenetic model describing soil forming processes such as carbon cycling, clay migration, decalcification, bioturbation, physical weathering and chemical weathering. The model has been calibrated and confronted with field measurements in a number of case studies, giving plausible results. Discrepancies between measured and simulated soil properties as concluded from case studies have been mainly attributed to (i) the simple chemical weathering system (ii) poor estimates of initial data inputs such as bulk density and element fluxes, and (iii) incorrect values of variables that describe boundary conditions such as precipitation and potential evapotranspiration. This study focuses on extending the chemical weathering system, such that it can deal with a more heterogeneous composition of primary minerals and includes more elements such as Fe and Si. We propose and discuss here an extended description of chemical weathering in the model that is based on more primary minerals, taking into account the role of the specific area of these minerals, and the effect of physical weathering on these specific areas over time. In the initial stage, the proposed chemical weathering mechanism is also implemented in PHREEQC (a widely applied geochemical code with capabilities to simulate equilibrium reactions involving water and minerals, surface complexes and ion exchangers, etc.) to facilitate comparison with the model results

  7. Stratigraphic Architecture of a Former Lowland Kauri Swamp in Ruakaka, North Island, New Zealand.

    Science.gov (United States)

    Velez, M.; Gontz, A. M.; Lorrey, A.

    2015-12-01

    The long-lived Kauri (Agathis australis) is an endemic conifer that presently exists within 4% of their pre-human contact range in northern New Zealand. Kauri preserve well in anoxic swamp and wetland environments in the lowlands across Northland and buried, subfossil samples of this species are commonly termed 'swamp kauri'. Subfossil kauri have been recently employed as a proxy to reconstruct past climate and establish a long dendrochronological records that have direct use for building the radiocarbon calibration curve. One component of work related to interpreting ancient kauri tree ring records is improving the understanding of the stratigraphic and geomorphic history of former lowland kauri environments to outline the role of environmental change in preserving this ancient wood resource. This study contributes to improving general understanding the subsurface stratigraphy of former lowland swamp kauri sites. A combination of ground penetrating radar, sediment cores, probing transects and trench exposures, provide details for the stratigraphic relationships for one type of swamp kauri site -relic coastal dune sequences- that will form a basis for future sediment and geochemistry work. Based on GPR and trenches, the stratigraphy includes several units -Peat, woody debris, dune sand, and coastal sand. Thickness of the peat, which usually contains the subfossil kauri, varies from thin veneers over antecedent coastal deposits 10-50cm to > 2.2m, with the thickest peat accumulation located between relic foredune ridges. Prior work at locations nearby have shown Rotoehu Tephra (>45ka) has been observed as a 40 cm thick deposit. Early sedimentary analysis suggests the Rotoehu is present at our study site, but it is possibly disseminated and bioturbation may have mixed the tephra into the underlying peat sediments. OSL samples and peat sediment samples were recovered for future chemical and chronological analysis from selected locations based on GPR and trench sections.

  8. Depositional Settings of the basal López de Bertodano Formation, Maastrichtian, Antarctica

    Directory of Open Access Journals (Sweden)

    E.B. Olivero

    2007-12-01

    Full Text Available In Snow Hill and Seymour islands the lower Maastrichtian, basal part of the L ópez de Bertodano Formation, rests on a high relief, erosive surface elaborated in the underlying Snow Hill Island Formation. Mudstone-dominated beds with inclined heterolithic stratification dominate the basal strata of the López de Bertodano Formation. They consist of rhythmical alternations of friable sandy- and clayeymudstone couplets, with ripple cross lamination, mud drapes, and flaser bedding. They are characterized by a marked lenticular geometry, reflecting the filling of tide-influenced channels of various scales and paleogeographic positions within a tide-dominated embayment or estuary. Major, sand-rich channel fills, up to 50-m thick, bounded by erosive surfaces probably represent inlets, located on a more central position in the estuary. Minor channel fills, 1- to 3-m thick, associated with offlapping packages with inclined heterolithic stratification probably represent the lateral accretion of point bars adjacent to migrating tidal channels in the upper estuary. Both types of channel fills bear relatively abundant marine fauna, are intensively bioturbated, and are interpreted as a network of subtidal channels. In southwestern Snow Hill Island, the minor offlapping packages have scarce marine fossils and bear aligned depressions interpreted as poor preserved dinosaur footprints. They represent the lateral accretion of point bars adjacent to intertidal creeks, probably located on the fringes of a mud-dominated estuary or embayment. The basal unconformity was produced by subaerial erosion; hence the inferred estuarine settings are consistent with the beginning of a new transgressive sedimentary cycle.

  9. Impact of bottom trawling on deep-sea sediment properties along the flanks of a submarine canyon.

    Directory of Open Access Journals (Sweden)

    Jacobo Martín

    Full Text Available The offshore displacement of commercial bottom trawling has raised concerns about the impact of this destructive fishing practice on the deep seafloor, which is in general characterized by lower resilience than shallow water regions. This study focuses on the flanks of La Fonera (or Palamós submarine canyon in the Northwestern Mediterranean, where an intensive bottom trawl fishery has been active during several decades in the 400-800 m depth range. To explore the degree of alteration of surface sediments (0-50 cm depth caused by this industrial activity, fishing grounds and control (untrawled sites were sampled along the canyon flanks with an interface multicorer. Sediment cores were analyzed to obtain vertical profiles of sediment grain-size, dry bulk density, organic carbon content and concentration of the radionuclide 210Pb. At control sites, surface sediments presented sedimentological characteristics typical of slope depositional systems, including a topmost unit of unconsolidated and bioturbated material overlying sediments progressively compacted with depth, with consistently high 210Pb inventories and exponential decaying profiles of 210Pb concentrations. Sediment accumulation rates at these untrawled sites ranged from 0.3 to 1.0 cm y-1. Sediment properties at most trawled sites departed from control sites and the sampled cores were characterized by denser sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sediments caused by trawling gears. Other alterations of the physical sediment properties, including thorough mixing or grain-size sorting, as well as organic carbon impoverishment, were also visible at trawled sites. This work contributes to the growing realization of the capacity of bottom trawling to alter the physical properties of surface sediments and affect the seafloor integrity over large spatial scales of the deep-sea.

  10. Interplay between physical movements of soils and mineral grains and chemical weathering

    Science.gov (United States)

    Yoo, K.

    2007-12-01

    Most soil biogeochemistry studies treat the soils and their inorganic and organic constituents as physically immobile. Those soil materials, however, are in perpetual motion due to the conversion of bedrock to soils, colluvial transport, and vertical mixing by various biophysical perturbations of the soils. Subsequently, a soil is continuously replaced by the materials from the neighboring soils and the underlying parent material, while its individual horizons are gradually mixed with the materials in the neighboring horizons. The movements of bulk soil materials are ultimately driven by moving individual mineral grains. While rarely appreciated, these physical movements of soil's mineral components operate in the presence of strong vertical and topographic gradients of the rates of mineral dissolution and leaching. The result is that the physical movement of soil constituents affects chemical weathering. The fluxes of soil materials (via physical movements and solute fluxes) in and out of a soil system defined by a researcher determine the time length that the materials reside in the system. The residence time, together with the system-specific rates of chemical weathering, determine the degree of weathering of the materials within the system. This presentation provides a new mathematical framework to consistently quantify the residence times of minerals, individual soil horizons, soil profiles, and an entire soil within a watershed boundary. Soil age, which is equivalent of the time length since the cessation of erosion or deposition on level grounds, becomes a special case of the residence time. The model is combined with empirical data to quantitatively illustrate the impacts that the physical motion of soil constituents have on the rates of chemical weathering. The data are drawn from ongoing field and laboratory studies focusing on the impact of river incision, colluvial flux, bioturbation, and agricultural tillage on the vertical and lateral variation of

  11. GPR investigation of karst guided by comparison with outcrop and unmanned aerial vehicle imagery

    Science.gov (United States)

    Fernandes, Antonio L.; Medeiros, Walter E.; Bezerra, Francisco H. R.; Oliveira, Josibel G.; Cazarin, Caroline L.

    2015-01-01

    The increasing importance of carbonate rocks as aquifers, oil reservoirs, and for urban problems is demanding detailed characterization of karst systems, a demand that can be partially satisfied with GPR imaging. However, the goal of imaging and interpreting karstified carbonate rocks is notoriously difficult due to the complex nature of the geometry of the dissolution and the GPR intrinsic limitations. One way forward is the direct comparison of GPR images with similar outcropping rocks. A joint study involving a 200 MHz GPR survey, unmanned aerial vehicle imagery (UAV), and outcrop characterization is presented aiming to improve the interpretation of sedimentary structures, fractures and karst structures in GPR images. The study area is a 500 m wide and 1000 m long carbonate outcrop of the Jandaíra Formation in Potiguar basin, Brazil, where sedimentary, fracture, and karst features can be directly investigated in both vertical and horizontal plan views. The key elements to interpret GPR images of karstified carbonate rocks are: (1) primary sedimentary structures appear in radargrams as unaltered imaged strata but care must be taken to interpret complex primary sedimentary features, such as those associated with bioturbation; (2) subvertical fractures might appear as consistent discontinuities in the imaged strata, forming complex structures such as negative flowers along strike-slip faults; (3) dissolution may create voids along subhorizontal layers, which appear in radargrams as relatively long amplitude shadow zones; and (4) dissolution may also create voids along subvertical fractures, appearing in radargrams as amplitude shadow zones with relatively large vertical dimensions, which are bounded by fractures.

  12. Application of paleoDNA for identification of paleotsunami deposits

    Science.gov (United States)

    Szczucinski, W.; Pawlowska, J.; Lejzerowicz, F.; Nishimura, Y.; Kokocinski, M.; Majewski, W.; Nakamura, Y.; Pawlowski, J.

    2015-12-01

    The identification of sedimentary records of paleotsunamis is the key to tsunami hazard assessment. However, it is often challenging to distinguish the tsunami deposits due to their variability, influence of local context, variable sediment sources, as well as postdepositional alterations. Among the most commonly used approaches to identify paleotsunami is the study of microfossils (e.g. foraminifera, diatoms). They are most commonly used to show marine origin of sediments. The common problem with microfossils in coastal settings (eg. marshes, peat bogs) is that they may not be preserved. For instance, it was found during studies on post-depositional changes of 2004 tsunami deposits and in paleotsunami deposits in Thailand that the tests composed of calcium carbonate as well as from silica have been largely dissolved with time. The rapid progress in paleogenetic studies suggests that analyses of DNA preserved in marine sediments may be a new research direction. A recent successful application of the method to the deep sea and fjord sediments, greater than 30,000 years old proved that it is possible to extract DNA and identify it from sediments that are affected by oxygenated waters and bioturbating organisms. Here we apply the paleogenetic studies for a series of paleotsunami deposits from Urahoro, eastern Hokkaido Island, Japan dated to be from several hundreds of years to more than 2000 years old based on tephrochronology. The sandy tsunami deposits intercalated by muddy peat contained rare diatoms of various origin but foraminifera and radiolaria tests were missing. Nevertheless, we were able to retrieve short fragments of the foraminiferal DNA from marine species using high-throughput sequencing technology. Our study provides first evidence that eukaryotic DNA can be preserved in tsunami deposits in coastal marsh environment for as long as 2000 years even in absence of any micropaleontological evidence. Thus paleoDNA analyses may provide a new useful tool to

  13. Origin of carbonate concretions from mud mounds in the Gulf of Cadiz (SW Iberian Peninsula); Origen de las concreciones carbonatadas de los monticulos de fango en el Golfo de Cadiz (SO Peninsula Iberica)

    Energy Technology Data Exchange (ETDEWEB)

    Rejas, M.; Taberner, C.; Pueyo, J. J.; Giralt, S.; Mata, M. P.; Gibert, J. M. de; Diaz del Rio, V.

    2015-07-01

    The Gulf of Cadiz displays a number of structures that are associated with fluid circulation (mud volcanoes, mud mounds and pockmarks).This area has been used as natural laboratory for the sedimentological, bio- logical and biogeochemical studies of these environments. Analysis of the associated authigenic carbonates has been widely used as a proxy to yield insights into the circulation and chemical composition of these flu- ids. A study of carbonate concretions from the Iberico, Cornide and Arcos mud mounds in the Diasom Field was undertaken to better understand the origin and type of fluids from which these concretions precipitated. The concretions display varying morphologies, some of which correspond to bioturbation traces. X-ray dif- fractions revealed that these carbonate concretions are mainly composed of dolomite, Fe-rich dolomite, high magnesium calcite (HMC) and ankerite. The δ{sup 1}3 C values of carbonate minerals ranged between -48.3 and-10.9 V-PDB, which suggests that the main processes involved in their genesis are organic matter oxidation, bac- terial sulphate-reduction (BSR) and anaerobic methane oxidation (AOM). The origin of the methane is main- ly thermogenic, and only few concretions yielded δ{sup 1}3C values lower than -40 V-PDB, suggesting oxidation of microbial methane. Fluids involved in the carbonate precipitation are interpreted as being related to gas hydrate destabilisation (δ{sup 18}O fluid-V-SMOW values higher than +2%) and, to a lesser extent, modified seawater enriched in {sup 18}O due to rock-water interaction. Nevertheless, the highest δ{sup 1}8O fluid-V-SMOW values suggest that the influence of other deep-seated fluids due to clay-mineral dehydration cannot be ruled out. (Author)

  14. Spatial variability and the fate of cesium in coastal sediments near Fukushima, Japan

    Directory of Open Access Journals (Sweden)

    E. Black

    2014-05-01

    Full Text Available Quantifying the amount of cesium incorporated into marine sediments as a result of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP accident has proven challenging due to the limited multi-core sampling from within the 30 km zone around the facility, the inherent spatial heterogeneities in ocean sediments, and the potential for inventory fluctuations due to physical, biological, and chemical processes. Using 210Pb, 234Th, 137Cs, and 134Cs profiles from 20 sediment cores, coastal sediment inventories were reevaluated. A minimum 137Cs sediment inventory of 100 ± 50 TBq was found for an area of 55 000 km2 using cores from this study and a total of 130 ± 60 TBq using an additional 181 samples. These inventories represent less than 1% of the estimated 15–30 PBq of cesium released during the FDNPP disaster and constitute ~ 90% of the total coastal inventory of 137Cs remaining in 2012. The time needed for surface sediment activities (0 to 3 cm at the 20 locations to reduce by 50% via bioturbation was estimated to range from 0.4 to 26 years, indicating a much greater persistence of cesium in the sediments relative to coastal water activities. However, due to the observed variability in mixing rates, grain size, and inventories, additional cores are needed to further improve estimates and capture the full extent of cesium penetration into the shallow coastal sediments, which was deeper than 14 cm for all cores retrieved from water depths less than 150 m.

  15. Determinants of soil organic carbon pools in oak stands in northeastern Austria

    Science.gov (United States)

    Bruckman, Viktor J.; Hochbichler, Eduard; Yan, Shuai; Glatzel, Gerhard

    2010-05-01

    Recently deciduous forests in northeastern Austria received increased attention as potential sources of biomass for energetic utilisation. There are still substantial deficits in the knowledge on carbon pools, -sequestration and -dynamics at these forest sites. The aim of our study was therefore to identify the main determinants which control soil organic carbon (SOC) pools in differently managed Quercus petraea dominated stands. We used the chronosequence approach to test the influence of stand age and management on the SOC pool. Soil samples were systematically collected from 14 plots by means of a 70mm hand auger to a depth of max. 60cm and separated into five geometric horizons. Narrow O-layers and signs of active bioturbation on most sites suggest rapid carbon mineralisation. Carbon pools of the aboveground biomass, the O horizon as well as fine and coarse roots and decay were determined. Soils in our study are cambisols derived from fossil alluvial deposits and loess and calcic chernozems derived from loess. Total soil carbon was determined by means of dry combustion and subtraction of soil inorganic carbon (SIC, by means of the Scheibler-method) if present. Mean SOC contents ranged from 5.3 kg.m-2 to10.4 kg.m-2 in the entire study area. The highest contents were found in calcic chernozem sites (7.2-10.4 kg.m-2) followed by loamy cambisol (6.1-6.8 kg.m-2) and sandy cambisol sites (5.3-6.9 kg.m-2). Among three chronosequence sets, we found strong positive correlations with total nitrogen (Pearson correlation coefficients of +0.91 to +0.93, pcoppice with standards vs. high forest system) in deciduous forests in the northeastern lowlands of Austria has no decisive influence on soil carbon pools.

  16. Structured heterogeneity in a marine terrace chronosequence: Upland mottling

    Science.gov (United States)

    Schulz, Marjorie S.; Stonestrom, David A.; Lawrence, Corey; Bullen, Thomas D.; Fitzpatrick, John; Kyker-Snowman, Emily; Manning, Jane; Mnich, Meagan

    2016-01-01

    Soil mottles generally are interpreted as a product of reducing conditions during periods of water saturation. The upland soils of the Santa Cruz, CA, marine terrace chronosequence display an evolving sequence of reticulate mottling from the youngest soil (65 ka) without mottles to the oldest soil (225 ka) with well-developed mottles. The mottles consist of an interconnected network of clay and C-enriched regions (gray, 2.5Y 6/1) bordered by leached parent material (white, 2.5Y 8/1) within a diminishing matrix of oxidized parent material (orange, 7.5YR 5/8). The mottles develop in soils that formed from relatively uniform nearshore sediments and occur below the depth of soil bioturbation. To explore how a presumably wetland feature occurs in an unsaturated upland soil, physical and chemical characteristics of mottle separates (orange, gray, and white) were compared through the deep time represented by the soil chronosequence. Mineralogical, isotopic, and surface-area differences among mottle separates indicate that rhizogenic centimeter-scale mass transfer acting across millennia is an integral part of weathering, pedogenesis, and C and nutrient transfer. Elemental analysis, electron microscopy, and Fe-isotope systematics indicate that mottle development is driven by deep roots together with their fungal and microbial symbionts. Taken together, these data suggest that deep soil horizons on old stable landforms can develop reticulate mottling as the long-term imprint of rhizospheric processes. The processes of rhizogenic mottle formation appear to regulate pedogenesis, nutrients, and C sequestration at depth in unsaturated zones.

  17. {sup 210}Pb dating of sediments from the central and northern Adriatic Sea: deposition and preservation of sedimentary organic carbon

    Energy Technology Data Exchange (ETDEWEB)

    Hamilton, T. F., LLNL

    1998-04-01

    Lead-210 ({sup 21O}Pb) and organic C depth distribution profiles in sediments from the northern and central Adriatic Sea were measured as part of the EEC funded project on Eutrophic Limits of the Northern Adriatic (ELNA). {sup 210}Pb derived mass-accumulation rates decrease southward from between 0.15 and 0.2 g cm{sup -2}y{sup -1} close to the Po River outflow (> 24 m, water depth) to less than 0.04 g cm{sup -2}y{sup -1} in the Jabuka Pit (246 m, water depth) in the central Adriatic Sea. The mass- accumulation rates obtained in the Jabuka Pit correspond to mean sedimentation rates of about 0.03 cm y{sup -1} (ref. porosity = 0.5) and fall between 5 to 20 times lower than rates found for north Adriatic shelf cores. Estimated sedimentation rates are considered as upper limits because of the possible effects of bioturbation and physical disturbance on the {sup 21O}Pb sedimentary record but are consistent with data from previous work. Rates of sediment accumulation and carbon burial appear to be strongly influenced by the transport of fluvial materials from land and transport of fine-grained particles. First-order estimates of organic C burial rates into surface sediment ranged from 1 to 0.028 mMol cm{sup -2}y{sup -1} between the Po delta and the Jabuka Pit regions, respectively. We estimate that a maximum of 50% of organic C preserved in surface sediment may be derived from biological production in the overlying water column.

  18. The effects of temperature on oxygen uptake and nutrient flux in sediment inhabited by molluscs

    Directory of Open Access Journals (Sweden)

    Lei Zhang

    2013-02-01

    Full Text Available Benthic invertebrates play important roles in oxygen uptake and nutrient cycling in the benthic boundary layer. Temperature is an important factor that influences both invertebrate activity and the effects of the bioturbation on biogeochemistry. The present study aimed to investigate the influence of temperature on the sediment oxygen uptake and nutrient flux across the sediment-water interface in sediment inhabited by molluscs, animals that often dominate the benthic community. A microcosm was constructed using sediment, lake water, and molluscs from Lake Taihu, China. The clam Corbicula fluminea (Bivalvia: Corbiculidae and the snail Bellamya aeruginosa (Gastropoda: Viviparidae were selected for the experiment because they dominate the benthic community in the lake. The effect of C. fluminea and B. aeruginosa on sediment oxygen uptake and nutrient flux was simultaneously examined at both 15 and 25℃. The results indicated that C. fluminea significantly increased the sediment oxygen uptake and release of soluble reactive phosphorus (SRP and ammonium from the sediment to the overlying water at both temperatures, and the net sediment oxygen uptake, and the net SRP and ammonium fluxes caused by the clams were significantly higher at 25℃ than at 15℃. Moreover, B. aeruginosa significantly increased the sediment oxygen uptake at the two experimental temperatures, however the net sediment oxygen uptake induced by the snail did not differ significantly between 15 and 25℃. The SRP released from the sediment was stimulated significantly by B. aeruginosa at 25℃, and B. aeruginosa also produced significantly more net SRP release at 25℃ than that at 15℃. In contrast, the influence of B. aeruginosa on the net ammonium flux at each temperature was not statistically significant.

  19. Sub-MIlankovitch millennial and decadal cyclicity in Middle Eocene deep-marine laminated sediments, Ainsa Basin, Spanish Pyrenees

    Science.gov (United States)

    Scotchman, J. I.; Pickering, K. T.; Robinson, S. A.

    2010-12-01

    James I. Scotchman1, Kevin T. Pickering1 & Stuart A. Robinson1 1Department of Earth Sciences, UCL (University College London), Gower Street, London, WC1E 6BT, U.K. Climate variability on the scale of millennia has become conspicuous within Quaternary records with far fewer such records existing within the pre-Pleistocene geological record. We identify millennial and decadal cyclicity in deep-marine siliciclastic (turbiditic and hemipelagic) sediments from a core in the middle Eocene Ainsa Basin, Spanish Pyrenees. Outcrop spectral gamma-ray data from laterally adjacent and age-equivalent strata to the core, together with a re-analysis of bioturbation data from the core, identifies the three main Milankovitch orbital periods. From this data, we derive a robust sediment accumulation rate for these sediments of 27.5 cm/kyr. Spectral analysis of data from high-resolution multi-element XRF scanning of a ~10 m-thick stratigraphic interval of fine-grained laminated sediments reveals the presence of various high-frequency cycles mainly above the 99% confidence level. Applying our derived sediment accumulation rate yields sub-Milankovitch millennial-scale cycles (~5,400, ~2,800, and ~1,000 yr) and decadal (~90, ~50, and ~30 yr) cycles split between allogenic and authigenic deposition. These cycles are manifest in the core as grain-size variations. The ~5,400 and ~2,800 yr cycles, recorded by elemental (Al, K, Ca and Fe) and element/Al ratios (Si/Al, Ca/Al and Zr/Al) are interpreted as representing climatically-driven variation in sediment supply to the deep-marine Ainsa basin. Higher-frequency decadal cycles are coincident with well-known Gleissberg solar cycles or possible multiples of the 11-year Schwabe cycle although how these cycles are expressed within these sediments remains unclear.

  20. Development of topographic asymmetry: Insights from dated cinder cones in the western United States

    Science.gov (United States)

    McGuire, Luke A.; Pelletier, Jon D.; Roering, Joshua J.

    2014-08-01

    Topographic asymmetry, that is, differences in the morphology of landscapes as a function of slope aspect, can be used to infer ecohydrogeomorphic feedback relationships. In this study, we document the dependence of topographic gradients and drainage densities on slope aspect and time/age in four Quaternary cinder cone fields in Arizona, Oregon, and California. Cinder cones are particularly useful as natural experiments in geomorphic evolution because they begin their evolution at a known time in the past (many have been radiometrically dated) and because they often have simple, well-constrained initial morphologies. North-facing portions of cinder cones have steeper topographic gradients and higher mean vegetation cover (i.e., Normalized Difference Vegetation Index, or NDVI, values) under current climatic conditions compared with corresponding south-facing portions of cones within each volcanic field. Drainage density is also higher on north-facing portions of cones in three of the four volcanic fields. These differences in topography were not present initially but developed progressively over time, indicating that the asymmetry is a result of post-eruption geomorphic processes. To test alternative hypotheses for the slope-aspect control of topography, we developed a numerical model for cinder cone evolution and a methodology for estimating local paleovegetation cover as a function of elevation, slope aspect, and time within the Quaternary. The numerical model results demonstrate that rates of colluvial transport were higher on south-facing hillslopes in at least three of the four cinder cones fields. Our paleovegetation analysis suggests that in the two Arizona volcanic fields we studied, higher rates of colluvial transport on south-facing hillslopes were the result of greater time-averaged vegetation cover and hence higher rates of sediment transport by floral bioturbation. Our results illustrate the profound impact that relatively small variations in solar

  1. Correlation of resource plays and biodiversity patterns: accumulation of organic-rich shale tracks taxonomic turnover

    Science.gov (United States)

    Eoff, Jennifer D.

    2012-01-01

    Similar paleogeographic and paleotectonic settings characterize most self-sourced shale hydrocarbon plays. Their deposition occurred within similar orders of magnitude of eustatic events and during geologic periods characterized by “warm” (or transitional) climates and calcitic seas. In addition, the stratigraphic occurrence of shale plays parallels certain historical patterns of marine metazoan biodiversity. Such strong agreement among several correlation tools elucidates why these resources may be limited to discrete intervals of geological time. Correlation of self-sourced shale with biodiversity trends indicates that the factors controlling the deposition of marine organic matter may not be independent of those that induced taxonomic turnover. Paleoecological changes promoted accumulation and preservation of Type II kerogen. Deposition of self-sourced shale appears to correspond to reductions in absolute biodiversity and declining percentages of bioturbating taxa, with concomitant increases in proportions of pelagic taxa relative to infaunal and epifaunal organisms. Whereas upwelling and anoxia may have contributed to the deposition of kerogen in source rocks throughout much of the sedimentary record, diminished consumption of biomass by benthic metazoans likely augmented the preservation of organic carbon during deposition of this shale type. Rapid tectonic-plate reconfiguration induced coeval events, creating basins with sufficiently high rates of accommodation creation necessary to preserve additional organic material accumulating as the heterotrophic benthos suffered in response to rapidly changing environments. Combining sea-level curves, paleogeography, climate, and seawater chemistry provides a first-order approximation of the distribution of potential self-sourced shale in the geologic record. A model that predicts the stratigraphic distribution of self-sourced-shale deposition can aid in exploration of continuous hydrocarbon accumulations in self

  2. Trophic ecology of the sea urchin Spatangus purpureus elucidated from gonad fatty acids composition analysis.

    Science.gov (United States)

    Barberá, C; Fernández-Jover, D; López Jiménez, J A; González Silvera, D; Hinz, H; Moranta, J

    2011-05-01

    Irregular sea urchins such as the spatangoid Spatangus purpureus are important bioturbators that contribute to natural biogenic disturbance and the functioning of biogeochemical cycles in soft sediments. In the coastal waters of the Balearic Islands S. purpureus occurs in soft red algal beds, and can reach high densities. The diet of S. purpureus is unknown and it is particularly difficult to analyze the stomach contents of this group; therefore, we analyzed the fatty acid (FA) composition of the gonads and potential food resources in order to assess the trophic relationships of this species. The FA profiles of the gonads of S. purpureus agree well with the FA composition of the potential trophic resources (algae and sediment) and reveals changes between localities with different available resources. Three polyunsaturated FAs mainly contributes in the composition in the S. purpureus gonads: eicosapentaenoic acid (C20:5n-3) and arachidonic acid (C20:4n-6), both abundant in the macroalgal material, and palmitoleic acid (C16:1n-7), which is characteristic of sediment samples. Trophic markers of bacterial input and carnivorous feeding were significantly more abundant in sea urchins caught on bottoms with less vegetation. The current study demonstrates that the FA content of S. purpureus gonads is a useful marker of diet, as differences in the profiles reflected the variations in detritus composition. The results of this study show that this species has omnivorous feeding behavior; however, viewed in conjunction with available abundance data the results suggest that phytodetritus found within algal beds is an important carbon source for this species. PMID:21334740

  3. Earth-System Scales of Biodiversity Variability in Shallow Continental Margin Seafloor Ecosystems

    Science.gov (United States)

    Moffitt, S. E.; White, S. M.; Hill, T. M.; Kennett, J.

    2015-12-01

    High-resolution paleoceanographic sedimentary sequences allow for the description of ecosystem sensitivity to earth-system scales of climate and oceanographic change. Such archives from Santa Barbara Basin, California record the ecological consequences to seafloor ecosystems of climate-forced shifts in the California Current Oxygen Minimum Zone (OMZ). Here we use core MV0508-20JPC dated to 735,000±5,000 years ago (Marine Isotope Stage 18) as a "floating window" of millennial-scale ecological variability. For this investigation, previously published archives of planktonic δ18O (Globigerina bulloides) record stadial and interstadial oscillations in surface ocean temperature. Core MV0508-20JPC is an intermittently laminated archive, strongly influenced by the California Current OMZ, with continuously preserved benthic foraminifera and discontinuously preserved micro-invertebrates, including ophiuroids, echinoderms, ostracods, gastropods, bivalves and scaphopods. Multivariate statistical approaches, such as ordinations and cluster analyses, describe climate-driven changes in both foraminiferal and micro-invertebrate assemblages. Statistical ordinations illustrate that the shallow continental margin seafloor underwent predictable phase-shifts in oxygenation and biodiversity across stadial and interstadial events. A narrow suite of severely hypoxic taxa characterized foraminiferal communities from laminated intervals, including Bolivina tumida, Globobulimina spp., and Nonionella stella. Foraminiferal communities from bioturbated intervals are diverse and >60% similar to each other, and they are associated with echinoderm, ostracod and mollusc fossils. As with climate shifts in the latest Quaternary, there is a sensitive benthic ecosystem response in mid-Pleistocene continental margins to climatically related changes in OMZ strength.

  4. Effects of salt pond restoration on benthic flux: Sediment as a source of nutrients to the water column

    Science.gov (United States)

    Topping, Brent R.; Kuwabara, James S.; Carter, James L.; Garrettt, Krista K.; Mruz, Eric; Piotter, Sarah; Takekawa, John Y.

    2016-01-01

    augmented further by bioturbation, bioirrigation and episodic sediment resuspension events.

  5. Community Structure and Activity of a Highly Dynamic and Nutrient-Limited Hypersaline Microbial Mat in Um Alhool Sabkha, Qatar

    KAUST Repository

    Al-Thani, Roda

    2014-03-21

    The Um Alhool area in Qatar is a dynamic evaporative ecosystem that receives seawater from below as it is surrounded by sand dunes. We investigated the chemical composition, the microbial activity and biodiversity of the four main layers (L1–L4) in the photosynthetic mats. Chlorophyll a (Chl a) concentration and distribution (measured by HPLC and hyperspectral imaging, respectively), the phycocyanin distribution (scanned with hyperspectral imaging), oxygenic photosynthesis (determined by microsensor), and the abundance of photosynthetic microorganisms (from 16S and 18S rRNA sequencing) decreased with depth in the euphotic layer (L1). Incident irradiance exponentially attenuated in the same zone reaching 1% at 1.7-mm depth. Proteobacteria dominated all layers of the mat (24%–42% of the identified bacteria). Anoxygenic photosynthetic bacteria (dominated by Chloroflexus) were most abundant in the third red layer of the mat (L3), evidenced by the spectral signature of Bacteriochlorophyll as well as by sequencing. The deep, black layer (L4) was dominated by sulfate reducing bacteria belonging to the Deltaproteobacteria, which were responsible for high sulfate reduction rates (measured using 35S tracer). Members of Halobacteria were the dominant Archaea in all layers of the mat (92%–97%), whereas Nematodes were the main Eukaryotes (up to 87%). Primary productivity rates of Um Alhool mat were similar to those of other hypersaline microbial mats. However, sulfate reduction rates were relatively low, indicating that oxygenic respiration contributes more to organic material degradation than sulfate reduction, because of bioturbation. Although Um Alhool hypersaline mat is a nutrient-limited ecosystem, it is interestingly dynamic and phylogenetically highly diverse. All its components work in a highly efficient and synchronized way to compensate for the lack of nutrient supply provided during regular inundation periods.

  6. The origin of terrestrial pisoliths and pisolitic iron ore deposits: Raindrops and sheetwash in a semi-arid environment

    Science.gov (United States)

    Lascelles, Desmond F.

    2016-07-01

    Ooliths evidently form by chemical precipitation in limnic, paralic, fluvial and marine environments, pisoliths, however, appear to be restricted to terrestrial environments. Typically composed of iron, aluminium and manganese sesquioxides with minor admixtures of quartz and kaolinite, they are widely distributed in tropical to subtropical regions overlying deeply weathered soil profiles. Although iron-, aluminium- and manganese-rich end members are important sources of these metals, their genesis is still enigmatic; their formation has never been observed or produced experimentally and current models for their origin are little more than guesses. A new model is presented based on a unique personal observation in which pisoliths are formed by the action of charged raindrops during thunderstorms impacting on dry deeply weathered powdery soils. The pisoliths are transported across pediments by sheetwash, accumulating as thick deposits in the valley floors. Pisolites are characteristically unfossiliferous and typically clearly pedogenic. The absence of fine depositional layering, fossil seeds, leaves and pollen in pisolites is explained by bioturbation and the action of soil organisms during extended pedogenesis while the major coarse bedding features derive from erosional and depositional events in the evolution of the pediment. Pisolitic iron ores (aka channel iron deposits, CID) are a special case of transported pisolitic ferricrust that form an important resource of medium grade iron ore (57-60 wt% Fe) in the Pilbara Region of Western Australia. Apart from minor deposits in the northern Yilgarn Province of Western Australia, they have not been found elsewhere. They differ from normal transported ferricrust and terrestrial pisolites not only in the exceptionally high iron and low alumina and silica content but also in containing abundant fossilised wood particles.

  7. Factors controlling mud accumulation in the Heuksan mud belt off southwestern Korea

    Science.gov (United States)

    Chang, Tae Soo; Ha, Hun Jun; Chun, Seung Soo

    2015-12-01

    The Heuksan mud belt (hereafter HMB) is 20~50 km wide, ~200 km long, and ~50 m thick, having accumulated in the course of the Holocene transgression on the tide-dominated epicontinental shelf southwest of Korea. The internal architecture of the HMB is characterized by offshore prograding clinoforms. Of particular interest are the depositional processes responsible for this anomalously thick mud accumulation within a relatively short period of time. Tidal currents are important in the dispersal of mud in the HMB, although these alone cannot explain such an enormous mud deposit. In order to understand the formative processes of the HMB, a detailed sedimentary facies analysis, including high-resolution grain-size measurements, has been conducted on more than 30 short cores and three long drill cores recovered from the mud belt. Five major mud facies were identified. Of these, mud sequences showing a thickening-thinning trend of alternating silt and clay laminae suggestive of a tidal origin occur dominantly at inner to mid shelf locations. By contrast, internally structureless muds with sharp bases and no bioturbation, which are interpreted of representing fluid-mud deposits, are widespread at mid to outer shelf locations. Wave-generated mud ripples and storm beds on the inner shelf suggest that storm waves in winter resuspend previously deposited mud to form near-bed fluid-mud suspensions with resulting gravity-driven mud transport across the low-gradient outer shelf. This previously not recognized process is probably a major factor controlling depositional processes on the giant mud belt, enabling rapid accumulation and offshore progradation even during transgression, i.e., at times of sea-level rise.

  8. Process regime variability across growth faults in the Paleogene Lower Wilcox Guadalupe Delta, South Texas Gulf Coast

    Science.gov (United States)

    Olariu, Mariana I.; Ambrose, William A.

    2016-07-01

    The Wilcox Group in Texas is a 3000 m thick unit of clastic sediments deposited along the Gulf of Mexico coast during early Paleogene. This study integrates core facies analysis with subsurface well-log correlation to document the sedimentology and stratigraphy of the Lower Wilcox Guadalupe Delta. Core descriptions indicate a transition from wave- and tidally-influenced to wave-dominated deposition. Upward-coarsening facies successions contain current ripples, organic matter, low trace fossil abundance and low diversity, which suggest deposition in a fluvial prodelta to delta front environment. Heterolithic stratification with lenticular, wavy and flaser bedding indicate tidal influence. Pervasively bioturbated sandy mudstones and muddy sandstones with Cruziana ichnofacies and structureless sandstones with Ophiomorpha record deposition in wave-influenced deltas. Tidal channels truncate delta front deposits and display gradational upward-fining facies successions with basal lags and sandy tabular cross-beds passing into heterolithic tidal flats and biologically homogenized mudstones. Growth faults within the lower Wilcox control expanded thickness of sedimentary units (up to 4 times) on the downdip sides of faults. Increased local accommodation due to fault subsidence favors a stronger wave regime on the outer shelf due to unrestricted fetch and water depth. As the shoreline advances during deltaic progradation, successively more sediment is deposited in the downthrown depocenters and reworked along shore by wave processes, resulting in a thick sedimentary unit characterized by repeated stacking of shoreface sequences. Thick and laterally continuous clean sandstone successions in the downthrown compartments represent attractive hydrocarbon reservoirs. As a consequence of the wave dominance and increased accommodation, thick (tens of meters) sandstone-bodies with increased homogeneity and vertical permeability within the stacked shoreface successions are created.

  9. High-intensity geomagnetic field 'spike' observed at ca. 3000 cal BP in Texas, USA

    Science.gov (United States)

    Bourne, Mark D.; Feinberg, Joshua M.; Stafford, Thomas W.; Waters, Michael R.; Lundelius, Ernest; Forman, Steven L.

    2016-05-01

    By observing the fluctuations in direction and intensity of the Earth's magnetic field through time, we increase our understanding of the fluid motions of the Earth's outer core that sustain the geomagnetic field, the geodynamo. Recent archaeomagnetic studies in the Near East have found extremely rapid increases - 'spikes' - in geomagnetic field intensity at ca. 3000 yr cal BP. These observations have proved problematic for our current understanding of core-flow. However, until now, these geomagnetic spikes had not been observed outside of the Near East, where they have been preserved in metallurgical slag and fired, mud brick walls. We present a new, fully oriented, geomagnetic secular variation and relative palaeointensity (RPI) record for the last 17,000 yr from Hall's Cave, Texas, whose complete, >3.8 m thick sedimentary sequence spans from the present to 16 , 850 ± 110 RC yr BP (Modern to 20,600 cal BP). Within the stable, cool climate of the cave, pedogenic and bioturbation processes are negligible to non-existent, thereby limiting post-depositional physical and geochemical alteration of the magnetic record. The sub-aerial and subterranean setting of the sedimentary sequence in Hall's Cave enabled us to collect oriented palaeomagnetic cubes from a previously excavated stratigraphic section. The palaeomagnetic samples yielded high-quality vectors. An age model for the sequence, determined using 15 AMS 14C-dates on individual bones from microvertebrates, was combined with the palaeomagnetic data to construct a secular variation record. The record is in broad agreement with predictions by Holocene field models for the site's location. However, starting ca. 3000 yr ago, the RPI data indicate an almost four-fold increase in geomagnetic field intensity lasting several hundred years. This record presents well-dated evidence, obtained using conventional techniques, for the existence of a geomagnetic intensity spike in North America that is contemporaneous with the

  10. Seagrasses are negatively affected by organic matter loading and Arenicola marina activity in a laboratory experiment.

    Science.gov (United States)

    Govers, Laura L; Pieck, Timon; Bouma, Tjeerd J; Suykerbuyk, Wouter; Smolders, Alfons J P; van Katwijk, Marieke M

    2014-06-01

    When two ecosystem engineers share the same natural environment, the outcome of their interaction will be unclear if they have contrasting habitat-modifying effects (e.g., sediment stabilization vs. sediment destabilization). The outcome of the interaction may depend on local environmental conditions such as season or sediment type, which may affect the extent and type of habitat modification by the ecosystem engineers involved. We mechanistically studied the interaction between the sediment-stabilizing seagrass Zostera noltii and the bioturbating and sediment-destabilizing lugworm Arenicola marina, which sometimes co-occur for prolonged periods. We investigated (1) if the negative sediment destabilization effect of A. marina on Z. noltii might be counteracted by positive biogeochemical effects of bioirrigation (burrow flushing) by A. marina in sulfide-rich sediments, and (2) if previously observed nutrient release by A. marina bioirrigation could affect seagrasses. We tested the individual and combined effects of A. marina presence and high porewater sulfide concentrations (induced by organic matter addition) on seagrass biomass in a full factorial lab experiment. Contrary to our expectations, we did not find an effect of A. marina on porewater sulfide concentrations. A. marina activities affected the seagrass physically as well as by pumping nutrients, mainly ammonium and phosphate, from the porewater to the surface water, which promoted epiphyte growth on seagrass leaves in our experimental set-up. We conclude that A. marina bioirrigation did not alleviate sulfide stress to seagrasses. Instead, we found synergistic negative effects of the presence of A. marina and high sediment sulfide levels on seagrass biomass. PMID:24633960

  11. The benthic marine assemblages of the estuarine and shallow marine Upper Burdigalian deposits of the Korneuburg Basin in Lower Austria

    Science.gov (United States)

    Hengst, Babette; Zuschin, Martin; Harzhauser, Mathias; Mandic, Oleg; Roetzel, Reinhard

    2010-05-01

    In the course of highway constructions (Wiener Außenring-Schnellstraße (S1)) a detailed sedimentological transect of 1.8 km length was logged in deposits of the Central Paratethys near the village of Stetten, N of Korneuburg in Lower Austria. A total of 324 sediment- and 118 molluscan samples was studied. The siliciclastic succession consists of pelitic and sandy sediments and sandstones and is rich in fossils. The fossil remains consist of sponges, corals, serpulids, molluscs, balanids, echinoderms, fish and micromammals. Quantitatively the molluscs dominate and have been studied in detail. 139 species were determined from more than 11,000 shells. Two gastropod species, Agapilia pachii und Granulolabium bicinctum make up more than 53% of the assemblage. Another 11 species (Nassarius edlaueri, Bittium spina, Loripes dujardini, Hydrobia spp., Paphia subcarinata, Cyllenina ternodosa, Turritella gradata, Corbula gibba, Cerastoderma praeplicata, Striarca lactea, Sandbergeria perpusilla) each contributes more than 1% to the total molluscan composition, but all other 126 species are quantitatively unimportant. A conspicuous alternation between intertidal and shallow subtidal mollusc associations is evident. The intertidal is dominated by the superabundant Agapilia pachii and Granulolabium plicatum, whereas the heavily bioturbated fully marine subtidal is characterized by a more diverse assemblage including Turritella gradata, Nassarius edlaueri, Anadara diluvii and various venerids. Additionally, layers with large fragments of Crassostrea and thin coal deposits with Terebralia bidentata are quite abundant in the section. Washed in land snails (e.g., Planorbidae) and river snails (Melanopsidae) occur occasionally. This faunal composition, along with its typical alternation points to a vivid dynamic within this Lower Miocene, subtropical ecosystem in the paleo-estuary of the southern Korneuburg basin.

  12. Ecohydrological Interfaces as Dynamic Hotspots of Biogeochemical Cycling

    Science.gov (United States)

    Krause, Stefan; Lewandowski, Joerg; Hannah, David; McDonald, Karlie; Folegot, Silvia; Baranov, Victor

    2016-04-01

    Ecohydrological interfaces, represent the boundaries between water-dependent ecosystems that can alter substantially the fluxes of energy and matter. There is still a critical gap of understanding the organisational principles of the drivers and controls of spatially and temporally variable ecohydrological interface functions. This knowledge gap limits our capacity to efficiently quantify, predict and manage the services provided by complex ecosystems. Many ecohydrological interfaces are characterized by step changes in microbial metabolic activity, steep redox gradients and often even thermodynamic phase shifts, for instance at the interfaces between atmosphere and water or soil matrix and macro-pores interfaces. This paper integrates investigations from point scale laboratory microcosm experiments with reach and subcatchment scale tracer experiments and numerical modeling studies to elaborate similarities in the drivers and controls that constitute the enhanced biogeochemical activity of different types of ecohydrologica interfaces across a range of spatial and temporal scales. We therefore combine smart metabolic activity tracers to quantify the impact of bioturbating benthic fauna onto ecosystem respiration and oxygen consumption and investigate at larger scale, how microbial metabolic activity and carbon turnover at the water-sediment interface are controlled by sediment physical and chemical properties as well as water temperatures. Numerical modeling confirmed that experimentally identified hotspots of streambed biogeochemical cycling were controlled by patterns of physical properties such as hydraulic conductivities or bioavailability of organic matter, impacting on residence time distributions and hence reaction times. In contrast to previous research, our investigations thus confirmed that small-scale variability of physical and chemical interface properties had a major impact on biogeochemical processing at the investigated ecohydrological interfaces

  13. Influence of tubificid worms on nutrient fluxes across water-sediment interface in fish farm settling ponds

    Directory of Open Access Journals (Sweden)

    Puigagut J.

    2014-04-01

    Full Text Available The influence of tubificid worms on nutrient translocation from water to fish farm sediments accumulating in settling ponds was addressed under laboratory conditions. Small microcosms of 0.5 L were filled up with 35 g of sludge from a fish farm settling pond and 0.15 L of filtered settling pond water. The experimental set up consisted of one control line (no worms added, a second experimental line with 1 mg of tubificid worms·g-1 fresh sediment (550 individuals·m-2 and a third experimental line with 40 mg of tubificid worms·g-1 fresh sediment (22 000 individuals·m-2. Nutrients translocation was determined by monitoring overlaying water concentration of ammonia, nitrate and phosphate for ten days. Results showed that abundances of 550 individuals·m-2 had no significant influence on the fluxes of nutrients here considered. However, the influence of higher abundances of tubificids (22 000 individuals·m-2 was of significant extent on the translocation of nitrate and phosphate. Accordingly, bioturbation of tubificids caused 55% lower nitrate uptake by the sediment when compared to control conditions. Phosphorus released by the sediments of the control condition was ca. 90% higher than that recorded under abundances of tubificids (22 000 individuals·m-2. Results obtained allowed us to estimate that fish farm settling ponds highly colonized by tubificid worms (22 000 individuals·m-2 may contribute to decrease phosphorus discharge (in terms of soluble phosphorus in ca. 5 g of P·ton-1 of fish produced.

  14. The usefulness of outcrop analogue air permeameter measurements for analysing aquifer heterogeneity: testing outcrop hydrogeological parameters with independent borehole data

    Directory of Open Access Journals (Sweden)

    B. Rogiers

    2013-07-01

    Full Text Available Outcropping sediments can be used as easily accessible analogues for studying subsurface sediments, especially to determine the small-scale spatial variability of hydrogeological parameters. The use of cost-effective in situ measurement techniques potentially makes the study of outcrop sediments even more attractive. We investigate to what degree air permeameter measurements on outcrops of unconsolidated sediments can be a proxy for aquifer saturated hydraulic conductivity (K heterogeneity. The Neogene aquifer in northern Belgium, known as a major groundwater resource, is used as case study. K and grain size data obtained from different outcropping sediments are compared with K and grain size data from aquifer sediments obtained either via laboratory analyses on undisturbed borehole cores (K and grain size or via large-scale pumping tests (K only. This comparison shows a pronounced and systematic difference between outcrop and aquifer sediments. Part of this difference is attributed to grain size variations and earth surface processes specific to outcrop environments, including root growth, bioturbation, and weathering. Moreover, palaeoenvironmental conditions such as freezing-drying cycles and differential compaction histories will further alter the initial hydrogeological properties of the outcrop sediments. A linear correction is developed for rescaling the outcrop data to the subsurface data. The spatial structure pertaining to outcrops complements that obtained from the borehole cores in several cases. The higher spatial resolution of the outcrop measurements identifies small-scale spatial structures that remain undetected in the lower resolution borehole data. Insights in stratigraphic and K heterogeneity obtained from outcrop sediments improve developing conceptual models of groundwater flow and transport.

  15. Eutrophication in the northern Adriatic Sea: Pore water and sediment studies

    Energy Technology Data Exchange (ETDEWEB)

    Hammond, D.E.; Berelson, W.M. (Univ. of Southern California, Los Angeles (United States)); Giordani, P.; Langone, L.; Frignani, M.; Ravaioli, M. (Inst. di Geologia Marina, CNR, Bologna (Italy))

    1990-01-09

    The northern Adriatic Sea has been plagued by problems of eutrophication. This area is relatively shallow (maximum depth = 60m), becoming stratified during the summer months which inhibits oxygen transport to bottom waters. Anthropogenic nutrient loading in rivers entering the northern Adriatic (Po River being the largest) has increased nutrient input to this system and stimulated algal growth. Cores were collected for studies of pore water and solid phase chemistry at 6 stations in this region. [sup 210]Pb was used to constrain sediment accumulation rates and a range of 0-0.5 cm/yr was determined at different stations. Excess [sup 234]Th was only found in the upper 1-2 cm, suggesting that bioturbation is largely restricted to shallow depths. Pore water profiles show evidence of irrigation, and mean diffusive fluxes for oxygen, silica phosphate and ammonia are generally 20-90% of the fluxes obtained from benthic chamber measurements. This is consistent with previous work in this area in which studies of radon fluxes indicated that irrigation plays an important role in sediment-water exchange. Pore water profiles in the northern portion of the study area (near the Po River Delta) were markedly different than profiles in the south; sediments in the north are substantially more acidic and have high concentrations of dissolved iron and phosphate. From the alkalinity vs. TCO[sub 2] relationship in sediment pore waters it appears that differences in reactions involving the reduction of iron oxides and the exchange of magnesium for iron in clays are responsible for this regional difference in pore water properties. Sediments close to the Po apparently undergo more iron-magnesium exchange, while more distal sediments are limited in their ability to do so. Other pore water observations are limited in their ability to do so. Other pore water observations and trends regarding the shape of the silica profiles (which show shallow maxima) will be discussed.

  16. Multiscale heterogeneity characterization of tidal channel, tidal delta and foreshore facies, Almond Formation outcrops, Rock Springs uplift, Wyoming

    Energy Technology Data Exchange (ETDEWEB)

    Schatzinger, R.A.; Tomutsa, L. [BDM Petroleum Technologies, Bartlesville, OK (United States)

    1997-08-01

    In order to accurately predict fluid flow within a reservoir, variability in the rock properties at all scales relevant to the specific depositional environment needs to be taken into account. The present work describes rock variability at scales from hundreds of meters (facies level) to millimeters (laminae) based on outcrop studies of the Almond Formation. Tidal channel, tidal delta and foreshore facies were sampled on the eastern flank of the Rock Springs uplift, southeast of Rock Springs, Wyoming. The Almond Fm. was deposited as part of a mesotidal Upper Cretaceous transgressive systems tract within the greater Green River Basin. Bedding style, lithology, lateral extent of beds of bedsets, bed thickness, amount and distribution of depositional clay matrix, bioturbation and grain sorting provide controls on sandstone properties that may vary more than an order of magnitude within and between depositional facies in outcrops of the Almond Formation. These features can be mapped on the scale of an outcrop. The products of diagenesis such as the relative timing of carbonate cement, scale of cemented zones, continuity of cemented zones, selectively leached framework grains, lateral variability of compaction of sedimentary rock fragments, and the resultant pore structure play an equally important, although less predictable role in determining rock property heterogeneity. A knowledge of the spatial distribution of the products of diagenesis such as calcite cement or compaction is critical to modeling variation even within a single facies in the Almond Fin. because diagenesis can enhance or reduce primary (depositional) rock property heterogeneity. Application of outcrop heterogeneity models to the subsurface is greatly hindered by differences in diagenesis between the two settings. The measurements upon which this study is based were performed both on drilled outcrop plugs and on blocks.

  17. Biological Dimensions of Crack Morphology in Dryland Soils

    Science.gov (United States)

    DeCarlo, K. F.; Spiegel, M.; Caylor, K. K.

    2014-12-01

    Macropores and cracks have an integral role in soil hydrology, and the physicochemical factors that induce them have been the subject of much laboratory research. How these processes translate to field soils, however, is often obfuscated by the biological elements present that complicate its formation and dynamics. In this study, we investigated the biological influence of herbivores and vegetation on 3D crack morphology in a dryland swelling soil (black cotton/vertisol). Fieldwork was conducted at and near the Kenya Long-Term Exclosure Experiment (KLEE) plots in Mpala, central Kenya, where three different soil regions were identified: highly vegetated areas, animal trails, and termite mounds. Crack networks were physically characterized by pouring liquid resin into the soil and excavating them when dry, after which they were imaged and quantified using medical magnetic resonance imaging (MRI). Cracking intensity of each cast was corrected via soil moisture and bulk density measurements at 5 cm intervals over 30 cm. 3D characterization of the soil system shows that mechanical compaction is a major influence in the formation of extensive and deep cracks in animal trails, with megaherbivores (e.g. elephants) inducing the most extreme cracks. Bioturbation is seen as a major influence in the formation of shallower cracks in termite mounds, as termites loosen and aerate the soil and reduce the soil's cohesive properties. Highly vegetated soils show a large degree of variability: small, disconnected soil patches induced by vegetative cover and a larger root network results in smaller and shallower cracks, but full vegetative cover induces deep and irregular cracks, possibly due to diverted rainfall. Our results highlight the intricate connections between the biology and physics that dictate soil processes in a complex soil system at the field scale.

  18. Surface sedimentation and sediment property of 2014~2015 years on the Dongho open-coast intertidal flat, Gochang coast of southwestern Korea

    Science.gov (United States)

    Ryang, Woo Hun; Kang, Na Yeong; Kang, Sol Ip

    2016-04-01

    The Dongho intertidal flat, located on the southwestern coast of Korea, is macro-tide, open-coast, linear shoreline, and sand substrates. In the Dongho intertidal flat, this study has focused on characteristics of surface sedimentation and sediment properties during 2014~2015 years. Can cores (30×17×5 cm3) were sampled at 4 sites with 150 m interval from shoreline to lower intertidal area during the 6 seasons from spring (June) in 2014 to summer (Aug.) in 2015. The 24 can cores of the intertidal flat were analyzed for sediment texture, porosity, wet density, grain density, and shear strength at 2, 10, and 25 cm parts from the top. Sediment type is mostly sand (S) facies of the Folk scheme, and mean grain size and skewness of the sediments are 0.93~2.70 ϕ and -0.50~0.41, respectively. Sediment properties show porosity of 9~32%, wet density of 1.88~2.45 g/cm3, grain density of 2.62~3.09 g/cm3, and shear strength of 8~64 kPa. The cancore peels represent planar and inclined stratification and bioturbated faintly stratification with some shell fragments. The stratification weaken from the shoreline to the lower intertidal site. This is indicative of waning influences of sea wave in the Dongho intertidal flat. Keywords: macro-tide, open-coast, can core, intertidal flat, Gochang coast Acknowledgements: This study was supported by the research grant from the Korean Ministry of Oceans and Fisheries (PJT200538). This presentation is an interim result of the coastal research program in the study area.

  19. Towards an Accurate and Precise Chronology for the Colonization of Australia: The Example of Riwi, Kimberley, Western Australia

    Science.gov (United States)

    Balme, Jane; O’Connor, Sue; Whitau, Rose

    2016-01-01

    An extensive series of 44 radiocarbon (14C) and 37 optically stimulated luminescence (OSL) ages have been obtained from the site of Riwi, south central Kimberley (NW Australia). As one of the earliest known Pleistocene sites in Australia, with archaeologically sterile sediment beneath deposits containing occupation, the chronology of the site is important in renewed debates surrounding the colonization of Sahul. Charcoal is preserved throughout the sequence and within multiple discrete hearth features. Prior to 14C dating, charcoal has been pretreated with both acid-base-acid (ABA) and acid base oxidation-stepped combustion (ABOx-SC) methods at multiple laboratories. Ages are consistent between laboratories and also between the two pretreatment methods, suggesting that contamination is easily removed from charcoal at Riwi and the Pleistocene ages are likely to be accurate. Whilst some charcoal samples recovered from outside hearth features are identified as outliers within a Bayesian model, all ages on charcoal within hearth features are consistent with stratigraphy. OSL dating has been undertaken using single quartz grains from the sandy matrix. The majority of samples show De distributions that are well-bleached but that also include evidence for mixing as a result of post-depositional bioturbation of the sediment. The results of the two techniques are compared and evaluated within a Bayesian model. Consistency between the two methods is good, and we demonstrate human occupation at this site from 46.4–44.6 cal kBP (95.4% probability range). Importantly, the lowest archaeological horizon at Riwi is underlain by sterile sediments which have been dated by OSL making it possible to demonstrate the absence of human occupation for between 0.9–5.2 ka (68.2% probability range) prior to occupation. PMID:27655174

  20. From Magnetotactic Bacteria to Sediment Magnetizations: new insights

    Science.gov (United States)

    Egli, R.; Mao, X.; Zhao, X.

    2015-12-01

    Magnetotactic bacteria (MTB) represent one of the most intriguing examples of iron biomineralization and magnetic navigation in nature. MTB synthesize magnetic nanocrystals, called magnetosomes, which act as an incorporated compass for navigation purposes (magnetotaxis). MTB are ubiquitous organisms living in chemically stratified freshwater and marine environments, where they contribute significantly to the Fe cycle. Magnetosomes accumulate as fossil MTB remains in sediment (magnetofossils). The recent development of magnetic measurement protocols enabling to detect small magnetosome concentrations among complex iron mineral mixtures led to the discovery that magnetofossil preservation over geological times is not uncommon. Therefore, magnetofossils can play an important role in sedimentary records of the Earth's magnetic field, as well as conveying selective information about past environmental conditions (e.g. redox conditions and nutrient concentration). Paleomagnetic and environmental applications require us to understand the processes that control MTB occurrence, magnetofossil formation and preservation, and the final alignment with the Earth's magnetic field. Our current knowledge relies mostly on experiments performed with cultured MTB in aqueous solutions, under physical and chemical conditions that do not necessarily reproduce those encountered in sediment. These experiments have been pivotal for understanding magnetosome growth and the fundaments of magnetotaxis. On the other hand, recent investigations of living MTB populations in sediment with specially developed observation techniques led to unexpected findings, with important implications for magnetotaxis models, MTB ecology, and, indirectly, for modeling the acquisition of natural magnetizations in bioturbated sediments. Ludwig, P. et al. (2013), Global Planet. Change 110, 321-339. Mao, X. et al. (2014), Geochem. Geophys. Geosys. 15, doi:10.1002/2013GC005034. Mao, X. et al. (2014). PLoS ONE 9, doi

  1. Acid-base physiology response to ocean acidification of two ecologically and economically important holothuroids from contrasting habitats, Holothuria scabra and Holothuria parva.

    Science.gov (United States)

    Collard, Marie; Eeckhaut, Igor; Dehairs, Frank; Dubois, Philippe

    2014-12-01

    Sea cucumbers are dominant invertebrates in several ecosystems such as coral reefs, seagrass meadows and mangroves. As bioturbators, they have an important ecological role in making available calcium carbonate and nutrients to the rest of the community. However, due to their commercial value, they face overexploitation in the natural environment. On top of that, occurring ocean acidification could impact these organisms, considered sensitive as echinoderms are osmoconformers, high-magnesium calcite producers and have a low metabolism. As a first investigation of the impact of ocean acidification on sea cucumbers, we tested the impact of short-term (6 to 12 days) exposure to ocean acidification (seawater pH 7.7 and 7.4) on two sea cucumbers collected in SW Madagascar, Holothuria scabra, a high commercial value species living in the seagrass meadows, and H. parva, inhabiting the mangroves. The former lives in a habitat with moderate fluctuations of seawater chemistry (driven by day-night differences) while the second lives in a highly variable intertidal environment. In both species, pH of the coelomic fluid was significantly negatively affected by reduced seawater pH, with a pronounced extracellular acidosis in individuals maintained at pH 7.7 and 7.4. This acidosis was due to an increased dissolved inorganic carbon content and pCO2 of the coelomic fluid, indicating a limited diffusion of the CO2 towards the external medium. However, respiration and ammonium excretion rates were not affected. No evidence of accumulation of bicarbonate was observed to buffer the coelomic fluid pH. If this acidosis stays uncompensated for when facing long-term exposure, other processes could be affected in both species, eventually leading to impacts on their ecological role. PMID:25028324

  2. Effects of invasive fish and quality of water and sediment on macrophytes biomass, and their consequences for the waterbird community of a Mediterranean floodplain.

    Science.gov (United States)

    Laguna, Celia; López-Perea, Jhon J; Viñuela, Javier; Florín, Máximo; Feliu, Jordi; Chicote, Álvaro; Cirujano, Santos; Mateo, Rafael

    2016-05-01

    Floodplains are among the most threatened ecosystems world-wide because of multiple stressors, i.e., invasive species, pollution and aquifer overexploitation; the Tablas de Daimiel National Park (Spain) is a clear example of these kinds of impact. This work aims to test whether invasive fish and/or the water and sediment quality are significant drivers of the decline of stonewort (Chara spp.) meadows in the Tablas de Daimiel, investigating how this could explain changes observed in the waterbird community. Bird surveys performed monthly between June 2010 and April 2014 have shown that herbivorous species like the red-crested pochard (Netta rufina) reached historical records between September 2010 and June 2011, but have decreased since then. Piscivorous waterbirds like the great cormorant (Phalacrocorax carbo) and herons increased in population after 2011, however. These changes may be due to the decline of Chara spp. meadows, connected to overexploitation by herbivores, or to changes in water and sediment quality. To test this hypothesis, we studied the growth of Chara spp. biomass in ten sites of the Tablas de Daimiel, where experimental exclosures were set up to exclude herbivory by birds, and bioturbation and herbivory by fish. Our results have shown that the absence of Chara spp. in the Tablas de Daimiel is mostly explained by presence of invasive fish (i.e. common carp). Moreover, the physicochemical characteristics of the water (lower values of conductivity and higher values of inorganic carbon and organic nitrogen), as well as of the sediment (lower values of inorganic and organic phosphorus), favour the increase of Chara spp., in the absence of the fish effect. These results led the National Park managers to begin the control of invasive fish as an urgent measure to assure the ecological conservation of this Mediterranean wetland. PMID:26896580

  3. Transport mechanisms and rates for the long-lived Chernobyl deposits

    International Nuclear Information System (INIS)

    A programme of work has been carried out to determine the various transport rates and mechanisms of Chernobyl radionuclides moving from catchment areas to rivers, reservoirs, lakes and sediments. In so doing the potential for Cs to be retained by and remobilised from sediments was assessed, along with the amount of deposited radioactivity which was in soluble form and hence was available in drinking water. Only a limited Ru-103 data set was obtained before it had decayed away below detection limits. However, results from this period showed that Ru mirrored Cs in its behaviour as it was measurable in the sediments at the same time after the deposition and it was trapped in the bottom waters of the lake. A substantial Cs data set was obtained for two lakes, Windermere and Esthwaite Water and it could be interpreted, with the aid of mathematical models developed during this study, to indicate the major processes and pathways operating in the transport of Cs through lake catchments. During the initial period after the deposition a maximum of 27% of the Cs in the water column was found in the particulate form and rapidly (months) reduced to 10-15% of the total. Total water column concentrations had reduced to half their initial measured values within 15 days in Esthwaite Water and 70 days in Windermere. Cs-134 was observed in surface sediments within 7 days in Esthwaite Water (15.5 m deep) and 30 days in Windermere (65 m deep) which, from a knowledge of mixing regimes of the lakes can be interpreted in terms of similar settlement velocities of 1-2 m per day. A small proportion of Chernobyl material was rapidly moved into the sediment as shown by small concentrations of Cs-134 being found at a depth of 8 cm after one year. This indicates that a non-diffusional transport mechanism, such as bioturbation, may be important for the transport of particulate caesium in sediments. (author)

  4. Free atmospheric CO2 enrichment increased above ground biomass but did not affect symbiotic N2-fixation and soil carbon dynamics in a mixed deciduous stand in Wales

    Directory of Open Access Journals (Sweden)

    A. R. Smith

    2011-02-01

    Full Text Available Through increases in net primary production (NPP, elevated CO2 is hypothesized to increase the amount of plant litter entering the soil. The fate of this extra carbon on the forest floor or in mineral soil is currently not clear. Moreover, increased rates of NPP can be maintained only if forests can escape nitrogen limitation. In a Free atmospheric CO2 Enrichment (FACE experiment near Bangor, Wales, 4 ambient and 4 elevated [CO2] plots were planted with patches of Betula pendula, Alnus glutinosa and Fagus sylvatica on a former arable field. After 4 years, biomass averaged for the 3 species was 5497 (se 270 g m−2 in ambient and 6450 (se 130 g m−2 in elevated [CO2] plots, a significant increase of 17% (P = 0.018. During that time, only a shallow L forest floor litter layer had formed due to intensive bioturbation. Total soil C and N contents increased irrespective of treatment and species as a result of afforestation. We could not detect an additional C sink in the soil, nor were soil C stabilization processes affected by elevated [CO2]. We observed a decrease of leaf N content in Betula and Alnus under elevated [CO2], while the soil C/N ratio decreased regardless of CO2 treatment. The ratio of N taken up from the soil and by N2-fixation in Alnus was not affected by elevated [CO2]. We infer that increased nitrogen use efficiency is the mechanism by which increased NPP is sustained under elevated [CO2] at this site.

  5. Morphological and structural analysis of earthworm burrows A methodological approach by X-ray tomography

    Science.gov (United States)

    Garbout, A.; Peres, G.; Cluzeau, D.

    2009-04-01

    Earthworms are known to have burrowing activities that affect soil physical properties, generating tubular macroporosity, galleries. These bioturbation, establishing channels of preferential flow in soil, have a major role in the flow of water through percolation process in the profile or diffusion to the soil matrix. Our study had the purpose to propose a new approach to understand the descriptive parameters of earthworm burrows (morphological parameters, structural parameters). 5 Different soil volumes are taken from the field. X-ray tomography has been used for studying the 3D soil architecture. This approach allows us to characterize several morphological parameters (total length, volume, pore surface …) and structural ones (wall gallery density) of galleries extracted from networks, through the X-ray tomography. The wall has been defined in 3 areas (Z1 Z2 and Z3) as concentric ROI cylinders (region of interest) of constant increasing diameters (5mm) around the burrows. A density was measured in these 3 areas and along the gallery, to describe the evolution of the density around the pore and along the gallery, for the 5 different modalities. A wide variability of density was observed along the gallery and from the central zone to the soil matrix: The densities in the 3 zones are significantly different one another, whatever the modality considered (Friedman, 0.05). The density of the wall in Z1 evolves according to the pore surface and diameter. The Spearman's rank correlation test allows us to say that the density in Z1 is significantly and negatively correlated to the diameter and the surface of the pore. Evolution of the density around the pore of the burrow: A growth is noticed in Z1, located between 3 and 8 mm from the center of the pore. Its densities growth from -750Hu to 1100Hu.

  6. Porewater dynamics of silver, lead and copper in coastal sediments and implications for benthic metal fluxes

    Science.gov (United States)

    Kalnejais, Linda H.; Martin, W. R.; Bothner, Michael H.

    2015-01-01

    To determine the conditions that lead to a diffusive release of dissolved metals from coastal sediments, porewater profiles of Ag, Cu, and Pb have been collected over seven years at two contrasting coastal sites in Massachusetts, USA. The Hingham Bay (HB) site is a contaminated location in Boston Harbor, while the Massachusetts Bay (MB) site is 11 km offshore and less impacted. At both sites, the biogeochemical cycles include scavenging by Fe-oxyhydroxides and release of dissolved metals when Fe-oxyhydroxides are reduced. Important differences in the metal cycles at the two sites, however, result from different redox conditions. Porewater sulfide and seasonal variation in redox zone depth is observed at HB, but not at MB. In summer, as the conditions become more reducing at HB, trace metals are precipitated as sulfides and are no longer associated with Fe-oxyhydroxides. Sulfide precipitation close to the sediment–water interface limits the trace metal flux in summer and autumn at HB, while in winter, oxidation of the sulfide phases drives high benthic fluxes of Cu and Ag, as oxic conditions return. The annual diffusive flux of Cu at HB is found to be significant and contributes to the higher than expected water column Cu concentrations observed in Boston Harbor. At MB, due to the lower sulfide concentrations, the association of trace metals with Fe-oxyhydroxides occurs throughout the year, leading to more stable fluxes. A surface enrichment of solid phase trace metals was found at MB and is attributed to the persistent scavenging by Fe-oxyhydroxides. This process is important, particularly at sites that are less reducing, because it maintains elevated metal concentrations at the surface despite the effects of bioturbation and sediment accumulation, and because it may increase the persistence of metal contamination in surface sediments.

  7. Sea-Floor geology and character of Eastern Rhode Island Sound West of Gay Head, Massachusetts

    Science.gov (United States)

    Poppe, L.J.; McMullen, K.Y.; Ackerman, S.D.; Blackwood, D.S.; Irwin, B.J.; Schaer, J.D.; Forrest, M.R.

    2011-01-01

    Gridded multibeam bathymetry covers approximately 102 square kilometers of sea floor in eastern Rhode Island Sound west of Gay Head, Massachusetts. Although originally collected for charting purposes during National Oceanic and Atmospheric Administration hydrographic survey H11922, these acoustic data and the sea-floor stations subsequently occupied to verify them (1) show the composition and terrain of the seabed, (2) provide information on sediment transport and benthic habitat, and (3) are part of an expanding series of studies that provide a fundamental framework for research and management activities (for example, windfarms and fisheries) along the Massachusetts inner continental shelf. Most of the sea floor in the study area has an undulating to faintly rippled appearance and is composed of bioturbated muddy sand, reflecting processes associated with sediment sorting and reworking. Shallower areas are composed of rippled sand and, where small fields of megaripples are present, indicate sedimentary environments characterized by processes associated with coarse bedload transport. Boulders and gravel were found on the floors of scour depressions and on top of an isolated bathymetric high where erosion has removed the Holocene marine sediments and exposed the underlying relict lag deposits of Pleistocene drift. The numerous scour depressions, which formed during storm-driven events, result in the juxtaposition of sea-floor areas with contrasting sedimentary environments and distinct gravel, sand, and muddy sand textures. This textural heterogeneity in turn creates a complex patchwork of habitats. Our observations of local variations in community structure suggest that this small-scale textural heterogeneity adds dramatically to the sound-wide benthic biological diversity.

  8. Sedimentological and Stratigraphic Controls on Natural Fracture Distribution in Wajid Group, SW Saudi Arabia

    Science.gov (United States)

    Benaafi, Mohammed; Hariri, Mustafa; Abdullatif, Osman; Makkawi, Mohammed; Korvin, Gabor

    2016-04-01

    The Cambro-Permian Wajid Group, SW Saudi Arabia, is the main groundwater aquifer in Wadi Al-Dawasir and Najran areas. In addition, it has a reservoir potentiality for oil and natural gas in Rub' Al-Khali Basin. Wajid Group divided into four formations, ascending Dibsiyah, Sanamah, Khussyayan and Juwayl. They are mainly sandstone and exposed in an area extend from Wadi Al-Dawasir southward to Najran city and deposited within fluvial, shallow marine and glacial environments. This study aims to investigate the sedimentological and stratigraphic controls on the distribution of natural fractures within Wajid Group outcrops. A scanline sampling method was used to study the natural fracture network within Wajid Group outcrops, where the natural fractures were measured and characterized in 12 locations. Four regional natural fracture sets were observed with mean strikes of 050o, 075o, 345o, and 320o. Seven lithofacies characterized the Wajid Group at these locations and include fine-grained sandstone, coarse to pebbly sandstone, cross-bedded sandstone, massive sandstone, bioturbated sandstone, conglomerate sandstone, and conglomerate lithofacies. We found that the fine-grained and small scale cross-bedded sandstones lithofacies are characterized by high fracture intensity. In contrast, the coarse-grained sandstone and conglomerate lithofacies have low fracture intensity. Therefore, the relative fracture intensity and spacing of natural fractures within Wajid Group in the subsurface can be predicted by using the lithofacies and their depositional environments. In terms of stratigraphy, we found that the bed thickness and the stratigraphic architecture are the main controls on fractures intensity. The outcomes of this study can help to understand and predict the natural fracture distribution within the subsurface fractured sandstone hosting groundwater and hydrocarbon in Wajid and Rub' Al-Khali Basins. Hence, the finding of this study might help to explore and develop the

  9. Evolving Phytoplankton Stoichiometry Fueled Diversification of the Marine Biosphere

    Directory of Open Access Journals (Sweden)

    Antonietta Quigg

    2012-05-01

    Full Text Available The availability of nutrients and the quantity and quality of food at the base of food webs have largely been ignored in discussions of the Phanerozoic record of biodiversity. We examine the role of nutrient availability and phytoplankton stoichiometry (the relative proportions of inorganic nutrients to carbon in the diversification of the marine biosphere. Nutrient availability and phytoplankton stoichiometry played a critical role in the initial diversification of the marine biosphere during the Neoproterozoic. Initial biosphere expansion during this time resulted in the massive sequestration of nutrients into biomass which, along with the geologically slow input of nutrients from land, set the stage for severe nutrient limitation and relatively constant marine biodiversity during the rest of the Paleozoic. Given the slow nutrient inputs from land and low recycling rates, the growth of early-to-middle Paleozoic metazoans remained limited by their having to expend energy to first “burn off” (respire excess carbon in food before the associated nutrients could be utilized for growth and reproduction; the relative equilibrium in marine biodiversity during the Paleozoic therefore appears to be real. Limited nutrient availability and the consequent nutrient imbalance may have delayed the appearance of more advanced carnivores until the Permo-Carboniferous, when widespread orogeny, falling sea level, the spread of forests, greater weathering rates, enhanced ocean circulation, oxygenation, and upwelling all combined to increase nutrient availability. During the Meso-Cenozoic, rising oxygen levels, the continued nutrient input from land, and, especially, increasing rates of bioturbation, enhanced nutrient availability, increasing the nutrient content of phytoplankton that fueled the diversification of the Modern Fauna.

  10. Marine coastal sediments microbial hydrocarbon degradation processes: contribution of experimental ecology in the omics’era

    Directory of Open Access Journals (Sweden)

    Cristiana eCravo-Laureau

    2014-02-01

    Full Text Available Coastal marine sediments, where important biological processes take place, supply essential ecosystem services. By their location, such ecosystems are particularly exposed to human activities as evidenced by the recent Deepwater Horizon disaster. This catastrophe revealed the importance to better understand the microbial processes involved on hydrocarbon degradation in marine sediments raising strong interests of the scientific community. During the last decade, several studies have shown the key role played by microorganisms in determining the fate of hydrocarbons in oil-polluted sediments but only few have taken into consideration the whole sediment’s complexity. Marine coastal sediment ecosystems are characterized by remarkable heterogeneity, owning high biodiversity and are subjected to fluctuations in environmental conditions, especially to important oxygen oscillations due to tides. Thus, for understanding the fate of hydrocarbons in such environments, it is crucial to study microbial activities, taking into account sediment characteristics, physical-chemical factors (electron acceptors, temperature, nutrients, co-metabolites availability as well as sediment’s reworking due to bioturbation activities. Key information could be collected from in situ studies, which provide an overview of microbial processes, but it is difficult to integrate all parameters involved. Microcosm experiments allow to dissect in-depth some mechanisms involved in hydrocarbon degradation but exclude environmental complexity. To overcome these lacks, strategies have been developed, by creating experiments as close as possible to environmental conditions, for studying natural microbial communities subjected to oil pollution. We present here a review of these approaches, their results and limitation, as well as the promising future of applying ‘omics’ approaches to characterize in-depth microbial communities and metabolic networks involved in hydrocarbon

  11. Sedimentation Pulse in the NE Gulf of Mexico following the 2010 DWH Blowout.

    Directory of Open Access Journals (Sweden)

    Gregg R Brooks

    Full Text Available The objective of this study was to investigate the impacts of the Deepwater Horizon (DWH oil discharge at the seafloor as recorded in bottom sediments of the DeSoto Canyon region in the northeastern Gulf of Mexico. Through a close coupling of sedimentological, geochemical, and biological approaches, multiple independent lines of evidence from 11 sites sampled in November/December 2010 revealed that the upper ~1 cm depth interval is distinct from underlying sediments and results indicate that particles originated at the sea surface. Consistent dissimilarities in grain size over the surficial ~1 cm of sediments correspond to excess (234Th depths, which indicates a lack of vertical mixing (bioturbation, suggesting the entire layer was deposited within a 4-5 month period. Further, a time series from four deep-sea sites sampled up to three additional times over the following two years revealed that excess (234Th depths, accumulation rates, and (234Th inventories decreased rapidly, within a few to several months after initial coring. The interpretation of a rapid sedimentation pulse is corroborated by stratification in solid phase Mn, which is linked to diagenesis and redox change, and the dramatic decrease in benthic formanifera density that was recorded in surficial sediments. Results are consistent with a brief depositional pulse that was also reported in previous studies of sediments, and marine snow formation in surface waters closer to the wellhead during the summer and fall of 2010. Although sediment input from the Mississippi River and advective transport may influence sedimentation on the seafloor in the DeSoto Canyon region, we conclude based on multidisciplinary evidence that the sedimentation pulse in late 2010 is the product of marine snow formation and is likely linked to the DWH discharge.

  12. Origin of carbonate concretions from mud mounds in the Gulf of Cadiz (SW Iberian Peninsula)

    International Nuclear Information System (INIS)

    The Gulf of Cadiz displays a number of structures that are associated with fluid circulation (mud volcanoes, mud mounds and pockmarks).This area has been used as natural laboratory for the sedimentological, bio- logical and biogeochemical studies of these environments. Analysis of the associated authigenic carbonates has been widely used as a proxy to yield insights into the circulation and chemical composition of these flu- ids. A study of carbonate concretions from the Iberico, Cornide and Arcos mud mounds in the Diasom Field was undertaken to better understand the origin and type of fluids from which these concretions precipitated. The concretions display varying morphologies, some of which correspond to bioturbation traces. X-ray dif- fractions revealed that these carbonate concretions are mainly composed of dolomite, Fe-rich dolomite, high magnesium calcite (HMC) and ankerite. The δ13 C values of carbonate minerals ranged between -48.3 and-10.9 V-PDB, which suggests that the main processes involved in their genesis are organic matter oxidation, bac- terial sulphate-reduction (BSR) and anaerobic methane oxidation (AOM). The origin of the methane is main- ly thermogenic, and only few concretions yielded δ13C values lower than -40 V-PDB, suggesting oxidation of microbial methane. Fluids involved in the carbonate precipitation are interpreted as being related to gas hydrate destabilisation (δ18O fluid-V-SMOW values higher than +2%) and, to a lesser extent, modified seawater enriched in 18O due to rock-water interaction. Nevertheless, the highest δ18O fluid-V-SMOW values suggest that the influence of other deep-seated fluids due to clay-mineral dehydration cannot be ruled out. (Author)

  13. Characteristics and origin of Earth-mounds on the Eastern Snake River Plain, Idaho

    Energy Technology Data Exchange (ETDEWEB)

    Tullis, J.A.

    1995-09-01

    Earth-mounds are common features on the Eastern Snake River Plain, Idaho. The mounds are typically round or oval in plan view, <0.5 m in height, and from 8 to 14 m in diameter. They are found on flat and sloped surfaces, and appear less frequently in lowland areas. The mounds have formed on deposits of multiple sedimentary environments. Those studied included alluvial gravel terraces along the Big Lost River (late Pleistocene/early Holocene age), alluvial fan segments on the flanks of the Lost River Range (Bull Lake and Pinedale age equivalents), and loess/slopewash sediments overlying basalt flows. Backhoe trenches were dug to allow characterization of stratigraphy and soil development. Each mound has features unique to the depositional and pedogenic history of the site; however, there are common elements to all mounds that are linked to the history of mound formation. Each mound has a {open_quotes}floor{close_quotes} of a sediment or basement rock of significantly different hydraulic conductivity than the overlying sediment. These paleosurfaces are overlain by finer-grained sediments, typically loess or flood-overbank deposits. Mounds formed in environments where a sufficient thickness of fine-grained sediment held pore water in a system open to the migration to a freezing front. Heaving of the sediment occurred by the growth of ice lenses. Mound formation occurred at the end of the Late Pleistocene or early in the Holocene, and was followed by pedogenesis. Soils in the mounds were subsequently altered by bioturbation, buried by eolian deposition, and eroded by slopewash runoff. These secondary processes played a significant role in maintaining or increasing the mound/intermound relief.

  14. Dynamics of bacterial community structure on intertidal sandflat inhabited by the ghost shrimp Nihonotrypaea harmandi (Decapoda: Axiidea: Callianassidae) in Tomioka Bay, Amakusa, Japan.

    Science.gov (United States)

    Wada, Minoru; Urakawa, Tatsuyuki; Tamaki, Akio

    2016-02-01

    Callianassid (ghost) shrimp has been claimed as an ecosystem engineer, as it is one of the most powerful bioturbating macrobenthos in intertidal sandflats. However, our knowledge about the relationship between areal distribution of bottom-dwelling ghost shrimps and dynamics of sediment microbial community structure remains obscured. We used automated ribosomal intergenic spacer analysis (ARISA) to reveal the bacterial community dynamics in the sediment of intertidal sandflat of Tomioka Bay, Kyushu, Japan, which is predominantly inhabited by a burrow-dwelling callianassid shrimp Nihonotrypaea harmandi. We found that the bacterial community structures of high and middle shrimp population areas were significantly differentiated from those of low population area (ANOSIM, R=0.10-0.18, p0.1). These results illustrated the potential importance of shrimp population density as a key factor in shaping the bacterial community structure and interpreting their dynamics in the sandflat. Furthermore, greater similarity between burrow and non-burrow communities was found in samples taken in autumn through winter than in those in summer (one-way ANOVA, pshrimp in permeable sandflat would strongly homogenize sediment particles, enhance solute transport surrounding the burrow and ambient subsurface substrate, and therefore reduce spatial differentiation of the bacterial community structure between the two sites. A comparison between present and previous studies of axiidean (former taxonomic group name, thalassinidean) ghost shrimps provides us with a comprehensive understanding of the shrimps' impacts on bacterial community dynamics, highlighting the importance of sediment permeability, a characteristic determined by the type of sediment, as a key controlling factor to shape spatial heterogeneity of bacterial community structure around burrow.

  15. The zoogeomorphic characteristics of burrows and burrowing by nine-banded armadillos (Dasypus novemcinctus)

    Science.gov (United States)

    Sawyer, Carol F.; Brinkman, Donald C.; Walker, Vincent D.; Covington, Tyler D.; Stienstraw, Elizabeth A.

    2012-07-01

    Burrowing animals act like a geomorphic disturbance, changing the environment through soil excavation, landform creation and bioturbation. The potential zoogeomorphic effects of these actions include modification of surficial features, increased soil erosion, changes in the growth and distribution of vegetation, and modifications to soil fertility. The burrowing ninebanded armadillo (Dasypus novemcinctus) migrated to North America prior to the 1850s and has since continued to expand its habitat to the American Southeast and parts of the Midwest. Little data are available on the zoogeomorphic impact of the burrowing nature of this species, making it difficult to predict future implications of this animal as it continues to migrate into new regions. On the University of South Alabama campus, in Mobile, Alabama, armadillos are present on a 35-hectare unprotected forested preserve used by the university community for outdoor activities and research. To understand the potential zoogeomorphic impact of armadillo burrows on the local environment, morphometric measurements were recorded on 187 burrows located in the study area. Using dimensions of burrow entrances and minimum lengths of tunnels in calculations, armadillos excavated approximately 0.029 m3 to 0.04 m3 of soil from each burrow. The entrances to burrows averaged 33.5° in slope and tended to be located in a microhabitat of a fallen tree, exposed tree roots, or a sideslope. Persistent fall of forest litter and anthropogenic modifications makes positive identification of spoil mounds possible in approximately half of the burrow sites. Surface modification by armadillos is ongoing in the study area with over half of the burrows classified as active during the four-month project. We concluded that, for southern Alabama, armadillos prefer to excavate burrows into sideslopes, and that given the lack of ground cover, sandy soil, and humid climate, armadillos are an important zoogeomorphic agent in the region.

  16. Stratigraphic revision of Campanian (Upper Cretaceous) rocks in the Henry Basin, Utah

    Energy Technology Data Exchange (ETDEWEB)

    Eaton, J.G. (Museum of Northern Arizona, Flagstaff (USA))

    1990-01-01

    Upper Cretaceous strata in the Henry Basin of south-central Utah include a 1,575 ft thick sequence of marginal marine and continental rocks of Campanian age. Stratigraphic study of this sequence indicates the need for changes in nomenclature and boundary definitions. Paleontologic study of the same sequence provides a basis for improved interpretations of depositional environments and age. The Mancos Shale of the Henry Basin is here redefined to include only strata up to the top of the Blue Gate Shale Member. The overlying Muley Canyon Sandstone and Masuk member are here removed from the Mancos Shale and given separate formation status. The lower and upper boundaries of the Muley Canyon Sandstone are redefined. The lower boundary is defined at the first prominent sandstone above the Mancos Shale. The upper boundary is defined at the base of the coal deposits overlying the bioturbated sandstones. The Muley Canyon Sandstone was deposited along a wave-dominated coastline and marks the final regression of Cretaceous epeiric seas from the area in the earliest Campanian. A type section of the overlying Masuk Formation is here designated and the formation is divided into three informal members. Abundant nonmarine molluscs and vertebrates have been recovered throughout the Masuk Formation and indicate a coastal floodplain depositional environment with only minor brackish influence. The vertebrate fauna supports an early Campanian age for the formation. The overlying Tarantula Mesa Sandstone and the beds on Tarantula Mesa are entirely nonmarine in origin, and fossils recovered from the beds on Tarantula Mesa support correlation of the unit to the lower part of the Kaiparowits Formation.

  17. A Numerical Model to Assess Soil Fluxes from Meteoric 10Be Data

    Science.gov (United States)

    Campforts, B.; Govers, G.; Vanacker, V.; Vanderborght, J.; Smolders, E.; Baken, S.

    2015-12-01

    Meteoric 10Be may be mobile in the soil system. The latter hampers a direct translation of meteoric 10Be inventories into spatial variations in erosion and deposition rates. Here, we present a spatially explicit 2D model that allows us to simulate the behaviour of meteoric 10Be in the soil system. The Be2D model is then used to analyse the potential impact of human-accelerated soil fluxes on meteoric 10Be inventories. The model consists of two parts. A first component deals with advective and diffusive mobility of meteoric 10Be within the soil profile including particle migration, chemical leaching and bioturbation, whereas a second component describes lateral soil (and meteoric 10Be) fluxes over the hillslope. Soil depth is calculated dynamically, accounting for soil production through weathering and lateral soil fluxes from creep, water and tillage erosion. Model simulations show that meteoric 10Be inventories can indeed be related to erosion and deposition, across a wide range of geomorphological and pedological settings. However, quantification of the effects of vertical mobility is essential for a correct interpretation of the observed spatial patterns in 10Be data. Moreover, our simulations suggest that meteoric 10Be can be used as a tracer to unravel human impact on soil fluxes when soils have a high retention capacity for meteoric meteoric 10Be. Application of the Be2D model to existing data sets shows that model parameters can reliably be constrained, resulting in a good agreement between simulated and observed meteoric 10Be concentrations and inventories. This confirms the suitability of the Be2D model as a robust tool to underpin quantitative interpretations of spatial variability in meteoric 10Be data for eroding landscapes.

  18. Fidelity of life and death molluscan assemblages from carbonate tidal flats in the Persian (Arabian) Gulf

    Science.gov (United States)

    García-Ramos, Diego A.; Albano, Paolo G.; Harzhauser, Mathias; Piller, Werner E.; Zuschin, Martin

    2016-04-01

    Live-dead (LD) studies aim to help understand how faithfully fossil assemblages can be used to quantitatively infer the structure of the original living communities that generated them. To this purpose, LD comparisons have been conducted in different terrestrial and aquatic environments to assess how environment-specific differences in quality and intensity of taphonomic factors affect LD fidelity. In sub-tropical and tropical settings, most LD studies have focused on hard substrates or seagrass bottoms. Here we present results on molluscan assemblages from soft carbonate sediments in tidal flats of the Persian (Arabian) Gulf (Indo-West Pacific biogeographic province). We analyzed a total of 7193 mollusks collected from six sites comprising time-averaged death assemblages (DAs) and snapshot living assemblages (LAs). All analyses were performed at site and at habitat scales after correcting for sample-size differences. We found a good match in proportional abundance and a notable mismatch in species composition. In fact, species richness in DAs is 6 times larger than in LAs at site scale, and 4 times at habitat scale. Additionally, we found a good fidelity of evenness, and rank abundance of feeding guilds. Other studies have shown that molluscan DAs from subtidal carbonate environments can display lower time-averaging than those from siliciclastic environments due to high rates of shell loss to bioerosion and dissolution. For our case study of tidal flat carbonate settings, we interpret that despite temporal autocorrelation (good fidelity of proportional abundance), substantial differences in species richness and composition can be explained by early cementation, lateral mixing, intense bioturbation and moderate sedimentation rates. Our results suggest that tidal flat carbonate environments can potentially lead to a wider window of time-averaging in comparison with subtidal carbonate settings.

  19. Improvement of Carbon Dioxide Sweep Efficiency by Utilization of Microbial Permeability Profile Modification to Reduce the Amount of Oil Bypassed During Carbon Dioxide Flood

    Energy Technology Data Exchange (ETDEWEB)

    Schmitz, Darrel [Mississippi State Univ., Mississippi State, MS (United States); Brown, Lewis [Mississippi State Univ., Mississippi State, MS (United States); Lynch, F. Leo [Mississippi State Univ., Mississippi State, MS (United States); Kirkland, Brenda L. [Mississippi State Univ., Mississippi State, MS (United States); Collins, Krystal M. [Mississippi State Univ., Mississippi State, MS (United States); Funderburk, William K. [Mississippi State Univ., Mississippi State, MS (United States)

    2010-12-31

    The objective of this project was to couple microbial permeability profile modification (MPPM), with carbon dioxide flooding to improve oil recovery from the Upper Cretaceous Little Creek Oil Field situated in Lincoln and Pike counties, MS. This study determined that MPPM technology, which improves production by utilizing environmentally friendly nutrient solutions to simulate the growth of the indigenous microflora in the most permeable zones of the reservoir thus diverting production to less permeable, previously unswept zones, increased oil production without interfering with the carbon dioxide flooding operation. Laboratory tests determined that no microorganisms were produced in formation waters, but were present in cores. Perhaps the single most significant contribution of this study is the demonstration that microorganisms are active at a formation temperature of 115°C (239°F) by using a specially designed culturing device. Laboratory tests were employed to simulate the MPPM process by demonstrating that microorganisms could be activated with the resulting production of oil in coreflood tests performed in the presence of carbon dioxide at 66°C (the highest temperature that could be employed in the coreflood facility). Geological assessment determined significant heterogeneity in the Eutaw Formation, and documented relatively thin, variably-lithified, well-laminated sandstone interbedded with heavily-bioturbated, clay-rich sandstone and shale. Live core samples of the Upper Cretaceous Eutaw Formation from the Heidelberg Field, MS were quantitatively assessed using SEM, and showed that during MPPM permeability modification occurs ubiquitously within pore and throat spaces of 10-20 μm diameter. Testing of the MPPM procedure in the Little Creek Field showed a significant increase in production occurred in two of the five production test wells; furthermore, the decline curve in each of the production wells became noticeably less steep. This project greatly

  20. Effects of the invasive polychaete Marenzelleria spp. on benthic processes and meiobenthos of a species-poor brackish system

    Science.gov (United States)

    Urban-Malinga, Barbara; Warzocha, Jan; Zalewski, Mariusz

    2013-07-01

    The effects of the invasive polychaete Marenzelleria spp. on sediment processes and meiobenthos with an emphasis on free-living nematodes of the Vistula Lagoon (southern Baltic Sea) were investigated in a laboratory microcosm experiment. Marenzelleria occupies an open niche and its deep burying behaviour and feeding strategy represent a new function in the study area. Halos of oxidized sediment along Marenzelleria burrow walls indicated oxygen penetration into the burrows but the polychaete had no significant effect on porewater nutrient concentrations. The results showed, however, the density dependent effects of Marenzelleria on ammonium transport. An enhanced ammonium efflux was recorded at high polychaete densities (2000 ind. m- 2) but not at low polychaete densities (300 ind. m- 2). There was no observable impact of the polychaete on total meiobenthic numbers. There was, therefore, no indication that Marenzelleria caused meiofauna mortality. On the contrary, the polychaete significantly affected vertical distribution of meiofauna facilitating the colonization of deeper sediment depths and thus extending the habitat to be used by meiobenthos. In addition, Marenzelleria had a positive impact on the survival of turbellarians. Nevertheless, there was no effect of Marenzelleria on nematode assemblage structure and diversity, indicating that neither the physical presence nor the biological activity of the worm affected the nematode community. This suggests either 1. the limited impact of Marenzelleria on nematodes, resulting from the creation of simple, narrow and un-branched burrows, 2. poor response of nematode community resulting from their low abundance and diversity in the study area, or 3. the overriding role of the harsh chemical environment typical of sediments of the Vistula Lagoon, masking the effect of the bioturbator.

  1. Mercury contaminated sediment sites—An evaluation of remedial options

    Energy Technology Data Exchange (ETDEWEB)

    Randall, Paul M., E-mail: randall.paul@epa.gov [U.S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, 26 West Martin Luther King Drive, Cincinnati, OH 45268 (United States); Chattopadhyay, Sandip, E-mail: Sandip.Chattopadhyay@tetratech.com [Tetra Tech, Inc., 250 West Court Street, Suite 200W, Cincinnati, OH 45202 (United States)

    2013-08-15

    Mercury (Hg) is a naturally-occurring element that is ubiquitous in the aquatic environment. Though efforts have been made in recent years to decrease Hg emissions, historically-emitted Hg can be retained in the sediments of aquatic bodies where they may be slowly converted to methylmercury (MeHg). Consequently, Hg in historically-contaminated sediments can result in high levels of significant exposure for aquatic species, wildlife and human populations consuming fish. Even if source control of contaminated wastewater is achievable, it may take a very long time, perhaps decades, for Hg-contaminated aquatic systems to reach relatively safe Hg levels in both water and surface sediment naturally. It may take even longer if Hg is present at higher concentration levels in deep sediment. Hg contaminated sediment results from previous releases or ongoing contributions from sources that are difficult to identify. Due to human activities or physical, chemical, or biological processes (e.g. hydrodynamic flows, bioturbation, molecular diffusion, and chemical transformation), the buried Hg can be remobilized into the overlying water. Hg speciation in the water column and sediments critically affect the reactivity (i.e. conversion of inorganic Hg(II) to MeHg), transport, and its exposure to living organisms. Also, geochemical conditions affect the activity of methylating bacteria and its availability for methylation. This review paper discusses remedial considerations (e.g. key chemical factors in fate and transport of Hg, source characterization and control, environmental management procedures, remediation options, modeling tools) and includes practical case studies for cleaning up Hg-contaminated sediment sites. -- Highlights: ► Managing mercury-contaminated sediment sites are challenging to remediate. ► Remediation technologies are making a difference in managing these sites. ► Partitioning plays a dominant role in the distribution of mercury species. ► Mathematical

  2. Preliminary report on the Oldenburg “butter shale” in the Upper Ordovician (Katian; Richmondian Waynesville Formation, USA

    Directory of Open Access Journals (Sweden)

    Christopher D. Aucoin

    2015-02-01

    Full Text Available The Cincinnatian Series (Upper Ordovician; upper Katian of the Cincinnati Arch region, Ohio, Indiana and Kentucky contains several bed packages informally referred to as “butter shales” or “trilobite shales”. These packages are typically 1–2 m of relatively pure, homogeneous claystone with isolated, lenticular limestone beds. These claystones are most widely known for their excellent preservation of abundant trilobites, especially Isotelus and Flexicalymene, as well as diverse and commonly articulated bivalves, and nautiloids. A newly recognized butter shale interval in the Clarksville Member of the Waynesville Formation contains a typical butter-shale fossil assemblage, dominated by bivalves, orthoconic cephalopods and trilobites. To better study the fabric of this claystone, a large, epoxy-coated block of the claystone was dry-cut. Polished surfaces show a variety of otherwise cryptic features, including pervasive bioturbation and the presence of probable lingulid escape burrows (Lingulichnus, as well as abundant fodinichnia (Chondrites, Planolites, Teichichnus. Preservation of articulated trilobites and closed bivalves in approximate living position, as well as escape burrows, indicates deposition as a series of mud burial events or obrution deposits. We suggest that the butter shales resulted from net accumulation of multiple episodes of re-suspended mud deposition, which rapidly smothered organisms and resulted in exceptional preservation. Between events the seafloor was colonized by abundant deposit-feeding infaunal organisms, which destabilized the substrate and generated turbidity near the sediment–water interface, thus inhibiting sessile suspension feeders. Rapid net deposition was also interrupted by more prolonged periods (tens to hundreds of years of low sedimentation that permitted colonization by epifaunal brachiopod-dominated communities. While most butter shale units are regionally extensive, the Oldenburg is

  3. Correlation, dispersal, and preservation of the Kawakawa Tephra and other Late Quaternary tephra layers in the Southwest Pacific Ocean

    International Nuclear Information System (INIS)

    Voluminous rhyolitic eruptions and prevailing westerly winds have dispersed Late Quaternary ash from the Taupo Volcanic Zone (TVZ) of the North Island, New Zealand, across the Southwest Pacific Ocean. We identify the Taupo (1850 14C years), Waimihia (3280 yr), Rerewhakaaitu (14,700 yr), and Kawakawa (22,590 yr) Tephra layers in deep ocean cores, mainly on the basis of their stratigraphic position, radiometric age, and glass shard chemistry. Approximately 25 km3 of Taupo Tephra were dispersed ENE at least 650 km from the TVZ whereas c. 22 km3 of Waimihia Tephra and c. 14 km3 of Rerewhakaaitu Tephra travelled over 500 km to the east. In contrast, at least 400 km3 of Kawakawa Tephra occur out to 1400 km southeast of the TVZ. Such widespread dispersal is not only a function of the size of the Kawakawa eruption, but is also influenced by the strong wind regime during the last glaciation as manifest by high aeolian quartz contents of sediments encasing the tephra. More ash appears to have deposited offshore than is predicted by exponential thinning models. Taupo Tephra, in particular, has a conspicuous second thickness maximum, 660 km from the eruption centre. Dispersal has extended over different depositional settings that have affected the tephra layers. The best preserved deposits are in zones of high sedimentation including channel levees, submarine fans, and boundary current drifts. In contrast, preservation is poor in regions of active currents including the continental shelf, the crest of Chatham Rise, and the foot of Chatham Rise-Hikurangi Plateau where a deep western boundary current is intensified. Primary tephra deposits are also at risk in regions of frequent gravitational mass movement such as offshore Hawke Bay and eastern Bay of Plenty. Further post depositional modification is by bioturbation, especially where tephra are c. <1 cm thick; thicker deposits tend to survive, which implies a smothering of the benthic fauna. (author). 81 refs., 8 figs., 6 tabs

  4. Soil and vegetation carbon stocks in Brazilian Western Amazonia: relationships and ecological implications for natural landscapes.

    Science.gov (United States)

    Schaefer, C E G R; do Amaral, E F; de Mendonça, B A F; Oliveira, H; Lani, J L; Costa, L M; Fernandes Filho, E I

    2008-05-01

    The relationships between soils attributes, soil carbon stocks and vegetation carbon stocks are poorly know in Amazonia, even at regional scale. In this paper, we used the large and reliable soil database from Western Amazonia obtained from the RADAMBRASIL project and recent estimates of vegetation biomass to investigate some environmental relationships, quantifying C stocks of intact ecosystem in Western Amazonia. The results allowed separating the western Amazonia into 6 sectors, called pedo-zones: Roraima, Rio Negro Basin, Tertiary Plateaux of the Amazon, Javari-Juruá-Purus lowland, Acre Basin and Rondonia uplands. The highest C stock for the whole soil is observed in the Acre and in the Rio Negro sectors. In the former, this is due to the high nutrient status and high clay activity, whereas in the latter, it is attributed to a downward carbon movement attributed to widespread podzolization and arenization, forming spodic horizons. The youthful nature of shallow soils of the Javari-Juruá-Purus lowlands, associated with high Al, results in a high phytomass C/soil C ratio. A similar trend was observed for the shallow soils from the Roraima and Rondonia highlands. A consistent east-west decline in biomass carbon in the Rio Negro Basin sector is associated with increasing rainfall and higher sand amounts. It is related to lesser C protection and greater C loss of sandy soils, subjected to active chemical leaching and widespread podzolization. Also, these soils possess lower cation exchangeable capacity and lower water retention capacity. Zones where deeply weathered Latosols dominate have a overall pattern of high C sequestration, and greater than the shallower soils from the upper Amazon, west of Madeira and Negro rivers. This was attributed to deeper incorporation of carbon in these clayey and highly pedo-bioturbated soils. The results highlight the urgent need for refining soil data at an appropriate scale for C stocks calculations purposes in Amazonia. There

  5. Limnogeology in Brazil's "forgotten wilderness": a synthesis from the large floodplain lakes of the Pantanal

    Science.gov (United States)

    McGlue, Michael M.; Silva, Aguinaldo; Corradini, Fabricio A.; Zani, Hiran; Trees, Mark A.; Ellis, Geoffrey S.; Parolin, Mauro; Swarzenski, Peter W.; Cohen, Andrew S.; Assine, Mario L.

    2011-01-01

    Sediment records from floodplain lakes have a large and commonly untapped potential for inferring wetland response to global change. The Brazilian Pantanal is a vast, seasonally inundated savanna floodplain system controlled by the flood pulse of the Upper Paraguay River. Little is known, however, about how floodplain lakes within the Pantanal act as sedimentary basins, or what influence hydroclimatic variables exert on limnogeological processes. This knowledge gap was addressed through an actualistic analysis of three large, shallow (2- > Si4+ > Ca2+), mildly alkaline, freshwater systems, the chemistries and morphometrics of which evolve with seasonal flooding. Lake sills are bathymetric shoals marked by siliciclastic fans and marsh vegetation. Flows at the sills likely undergo seasonal reversals with the changing stage of the Upper Paraguay River. Deposition in deeper waters, typically encountered in proximity to margin-coincident topography, is dominated by reduced silty-clays with abundant siliceous microfossils and organic matter. Stable isotopes of carbon and nitrogen, plus hydrogen index measured on bulk organic matter, suggest that contributions from algae (including cyanobacteria) and other C3-vegetation dominate in these environments. The presence of lotic sponge spicules, together with patterns of terrigenous sand deposition and geochemical indicators of productivity, points to the importance of the flood pulse for sediment and nutrient delivery to the lakes. Flood-pulse plumes, waves and bioturbation likewise affect the continuity of sedimentation. Short-lived radioisotopes indicate rates of 0.11-0.24 cm year-1 at sites of uninterrupted deposition. A conceptual facies model, developed from insights gained from modern seasonal processes, can be used to predict limnogeological change when the lakes become isolated on the floodplain or during intervals associated with a strengthened flood pulse. Amplification of the seasonal cycle over longer time scales

  6. The distribution of gamma-emitting radionuclides in surface subtidal sediments near the Sellafield plant

    Science.gov (United States)

    Jones, D. G.; Roberts, P. D.; Miller, J. M.

    1988-08-01

    Detailed distributions of total gamma activity, 137Cs, 106Ru and 95Zr + 95Nb in surface seabed sediments near the Sellafield plant are presented. The results are derived from a towed seabed gamma-ray spectrometer survey in September, 1982. All the distributions are similar, with contours of equal activity parallel to the coast defining a 'ridge' of higher activity which is displaced northwards relative to the outfall. This pattern appears to be largely a response to the transport of particle-associated radioeffluent modified in places by the type of seabed sediment present. At greater distance from Sellafield, the uptake of nuclides from solution seems to be more important. Nuclide concentrations decrease with increasing distance from Sellafield; rates of decrease being in the order Zr + Nb > Ru > Cs. This can be related to the levels of the nuclides discharged, their sorption characteristics and their half lives. The pattern of seabed activity seems to have been fairly stable over the period 1978 - 1985, but there is evidence of a small northward shift. Concentrations of 137Cs and 106Ru in 1985 were considerably lower than in 1978 or 1982. This is explicable in terms of the fall in discharge levels allied, in the case of Ru, to its short half life and, for Cs, the desorption observed in laboratory experiments. Nuclide ratios in sediment samples yield apparent transit times for the transport of nuclides in the survey area of 1·7 - 3·7 years. These times are generally greater than those obtained from sediments in the more distant Solway Firth and Ravenglass Estuary. It is suggested that they reflect fairly intense bioturbation causing mixing of relatively recent effluent with that from earlier discharges. This is supported by structures observed in X-radiographs of box cores, an abundant burrowing benthos and by interpretations of nuclide profiles and radiocarbon dating of sediment cores by other workers. A lag effect, of up to two years across the survey area

  7. Impacts of leaves, roots, and earthworms on soil organic matter composition and distribution in sycamore maple stands

    Science.gov (United States)

    Rivera, N.; Mueller, K. E.; Mueller, C. W.; Oleksyn, J.; Hale, C.; Freeman, K. H.; Eissenstat, D.

    2009-12-01

    The relative contributions of leaf and root material to soil organic matter (SOM) are poorly understood despite the importance of constraining SOM sources to conceptual and numeric models of SOM dynamics. Selective ingestion and bioturbation of litter and soil by earthworms can alter the fate and spatial distribution of OM in soils, including stabilization pathways of leaf and root litter. However, studies on the contributions of leaves, roots, and earthworms to SOM dynamics are rare. In 3 stands of sycamore maple (Acer pseudoplatanus) with minimal O horizon development and high earthworm activity, we sampled surface litter (> 2 mm) from the Oi horizon, fine roots (< 2 mm), bulk mineral soils (0-20 cm depth), and earthworm casts from Lumbricus terrestris middens. The chemical composition of these samples was estimated by wet-chemical degradation followed by GC-MS analysis. In addition, elemental analyses (C and N) were performed on bulk soils and earthworm casts, before and after physical fractionation by means of particle size and density. Relative to bulk soils, earthworm casts were highly enriched in organic matter, dominated by large particulate OM, and had lower acid to aldehyde ratios among lignin monomers (a proxy for extent of decomposition), confirming that L. terrestris casts stabilize recent plant litter inputs. Maple fine roots and surface litter were distinguished by different profiles of carboxylic acids estimated by GC-MS, facilitating interpretation of OM sources in bulk soil and earthworm casts. Earthworm casts were characterized by a distribution of carboxylic acids similar to that of surface litter while bulk soils had a carboxylic acid profile much closer to that of roots. These results confirm that L. terrestris is primarily a surface, leaf feeder and suggest that OM in the bulk soil may be dominated by root inputs. In bulk soils, the ratio of lignin to hydroxy- and diacids derived from suberin and cutin was low relative to plant litter

  8. Carbon isotopes and iodine concentrations in a Mississippi River delta core recording land use, sediment transport, and dam building in the river's drainage basin.

    Science.gov (United States)

    Santschi, Peter H; Oktay, Sarah D; Cifuentes, Luis

    2007-04-01

    Sedimentary material from coastal and nearshore areas in the Mississippi Delta region are comprised of different organic carbon sources with diverse ages that require isotopic and elemental records for resolving the various sources of plant residues. Carbon isotopic ((13)C, (14)C) values were used to differentiate contributions from plants using the C3, C4, and/or CAM (crassulacean acid metabolism) carbon fixation pathways., and iodine concentrations indicated that wetland plant residues are a significant source of organic carbon in a sediment core from the Mississippi River delta region collected at a 60 m water depth. This sediment core had been extensively described in Oktay et al. [Oktay, S.D., Santschi, P.H., Moran, J.E., Sharma, P., 2000. The (129)Iodine Bomb Pulse Recorded in Mississippi River delta Sediments: Results from Isotopes of I, Pu, Cs, Pb, and C. Geochim. Cosmochim. Acta 64 (6), 989-996.] and significantly, includes unique features that had not previously been seen in the marine environment. These special features include a plutonium isotopic close-in fallout record that indicates a purely terrestrial source for these sediment particles and the elements associated with it, and a distinct iodine isotopic peak (as well as peaks for plutonium and cesium isotopes) that indicate little bioturbation in this core. Our carbon isotopic and iodine data can thus be compared to published records of changes in drainage basin land use, river hydrology, and hydrodynamic sorting of suspended particles to elucidate if these changes are reflected in nearshore sediments. This comparison suggests a significant contribution for organic carbon (OC) from C4 plants to these sediments during the 1950's to early 1960's. Relative older carbon isotopes, and episodically high iodine concentrations (up to 34 ppm) were observed during this time period that (1) indicate sediment deposition that is coincident with the times of major hydrological changes induced from dam and levee

  9. Seabed erodibility variations on the Louisiana continental shelf before and after the 2011 Mississippi River flood

    Science.gov (United States)

    Xu, K.; Corbett, D. R.; Walsh, J. P.; Young, D.; Briggs, K. B.; Cartwright, G. M.; Friedrichs, C. T.; Harris, C. K.; Mickey, R. C.; Mitra, S.

    2014-08-01

    Erodibility is critical to the sediment resuspension process but has not been measured systematically in large river-dominated muddy continental shelves before. During early summer of 2011, the Mississippi River experienced a major flood event. This flood provided a unique opportunity to examine how shelf seabed erodibility responded to a large river flood, and the ultimate fate of flood deposition is important to geological and biogeochemical processes (e.g., stratal formation, carbon sequestration). A total of 106 sediment cores were collected on the Louisiana shelf during five cruises in 2010 and 2011, and a new dataset was used to evaluate the response of the seabed to the recent conditions. The localized flood deposit was mainly within tens of kilometers of river sources, and little sediment accumulated on the middle Louisiana shelf. Seabed erodibility was measured using a dual-core Gust Erosion Microcosm System. The erodibility of sediment collected in April 2011 exceeded that for August 2010 and August 2011. The springtime increase in erodibility seemed to be related to the recent presence of energetic waves that mobilized the seabed. Erodibility was highest on the inner shelf southwest of Atchafalaya Bay, intermediate on the middle shelf, lowest in the Mississippi Canyon, and highly variable on the Mississippi subaqueous delta. These spatial patterns were influenced by proximity to river sources, flood-deposit thicknesses, intensity of wave-driven bed stresses, and bioturbation. The flood-deposit thickness itself, however, was not sufficient to explain all the spatial variations of erodibility after the peak of the Mississippi flood. Comparing values to published data, the depth-varying erodibility on the Louisiana shelf was close to the "low erodibility" level for the York River of Virginia, and similar to the data collected from Baltimore Harbor in Maryland and the main stem of upper Chesapeake Bay. Our findings promote understanding of the resuspension

  10. Physical vs. Chemical Weathering Controls of Soils' Capacity to Store Carbon: Hillslope Transects under Different Climatic Conditions

    Science.gov (United States)

    Yoo, K.; Wackett, A.; Amundson, R.; Heimsath, A. M.

    2015-12-01

    Soil C storage is balanced by photosynthetic production and microbial decomposition of organic matter (OM). Recently, this view has been expanded to account for the effects of physical erosion of OM in determining soil C storage. In parallel, the focus on OM quality as a primary determinant of C turnover has shifted to OM-mineral interactions. These recent advances necessitates our ability to discern how physical erosion, which controls the production, breakdown, and removal of colluvial soils, and chemical weathering, which generates secondary phyllosilicate and iron oxides, independently and collaboratively affect soils' capacity to store C. Here we present soil organic C contents and storages as a function of soil properties that are controlled by physical vs. chemical weathering processes. The study site includes two hillslopes under different climates in SW Australia. The wetter site has continuous canopy of eucalyptus, while the drier site is covered by grasses with scattered eucalyptus overstorey. The two hillslope transects share similar granodiorite parent materials and denudation rates. Bioturbation-driven soil creep appears equally effective at both sites. In eroding areas, chemical weathering has created greater mineral surface area in the soils of wetter site, while physical soil production and erosion resulted in forming the eroding soils of similar thicknesses at both sites. In the drier site, however, vegetation density varies significantly with topography-dependent soil moisture, which appears to have resulted in a soil toposequence where impacts of localized overland-flow erosion is evident through soil mineral surface area, texture, and C contents. These soil properties, in contrast, are largely homogeneous across the wetter hillslope transect presumably because of the lack of localized overland-flow erosion. As a result, at the depositional areas, the drier site exhibits greater or similar soil C storages, which sharply contrasts with the

  11. A new Permian bivalve-dominated assemblage in the Rio do Rasto Formation, Paraná Basin, Brazil: Faunal turnover driven by regional-scale environmental changes in a vast epeiric sea

    Science.gov (United States)

    Simões, Marcello Guimarães; Matos, Suzana Aparecida; Anelli, Luiz Eduardo; Rohn, Rosemarie; Warren, Lucas Veríssimo; David, Juliana Machado

    2015-12-01

    The basal portion of the Permian Rio do Rasto Formation (Serrinha Member), Passa Dois Group, Paraná Basin, Brazil, records an entirely new bivalve fauna intercalated between the underlying Pinzonella neotropica assemblage (uppermost portion of the Teresina Formation) and the overlying Leinzia similis assemblage (Rio do Rasto Formation). Mollusks of these assemblages lived in marginal shallow-water habitats of an immense epeiric sea and were dominated by endemic bivalve species. Taxonomic analysis revealed the presence of Terraia curvata (60.61%), Astartellopsis prosoclina (19.70%), Cowperesia emerita (10.61%), Leinzia curta (4.55%), Terraia bipleura (3.03%) and Beurlenella elongatella (1.52%), which are associated with conchostracans and plant remains. Species composition, abundance, and dominance in this novel assemblage differ notably from the preceding ones, suggesting a substantial evolutionary turnover. Regional-scale environmental changes recognized based on taphonomy, facies analysis, and geochemical data consist of progressive freshening of the marginal habitats of the Paraná Basin and taxic changes that include the following: (a) loss of genera, (b) decrease in bivalve abundance and ecological guilds, (c) disappearance of the dominant bivalve group (Pinzonellinae) and (d) diversification of Terrainae bivalves. The ecological signature also changed notably because only infaunal suspension-feeding bivalves are present, indicating a significant loss of functional diversity at the regional scale. Likely stressor factors (among others) are tied to freshening events, suggesting profound changes in (a) salinity, (b) primary productivity and (c) a lack of coarse, stable substrates coupled with high bioturbation rates. Hence, our regional example could offer valuable clues to benthic (bivalve) community responses in a habitat subjected to (a) rapid climate changes and (b) freshening events in shallow-water settings. Finally, the stratigraphic range of the

  12. Changes in the northern Adriatic molluscan community from the Holocene transgression up to the present

    Science.gov (United States)

    Gallmetzer, Ivo; Haselmair, Alexandra; Tomasovych, Adam; Stachowitsch, Michael; Zuschin, Martin

    2016-04-01

    The northern Adriatic Sea is one of the few modern, epicontinental seas comparable to typical Palaeozoic shelf environments. It has a shallow average water depth (degraded marine ecosystems worldwide. Our study was designed to reconstruct major environmental changes here since the onset of the Holocene transgression using down-core changes in death assemblages of molluscs as indicators for ecological shifts. The sediment cores were taken at three different stations (Brijuni Islands, Croatia, off Piran, Slovenia, and off Venice, Italy), each representative of specific sediment and nutrient conditions and degrees of habitat exploitation. The cores were 1.5 m long and had diameters of 90 or 160 mm. For the molluscan shell analyses, sediment subsamples were examined for species composition, abundance, taxonomic similarity and ecological interactions (e.g. frequencies of drilling predation). In total, 98,700 valves and shells were investigated and 113 bivalve and 178 gastropod species recorded. Sedimentation rates derived from 210Pb dating are very low, between 0.15 cm/yr at Brijuni and 0.25 cm/yr at Piran. The dating of Lucinella divaricata, Timoclea ovata and Gouldia minima shells with 14C calibrated amino-acid racemisation (AAR) revealed that the cores at all three stations cover at least 6000 to 8000 years, i.e. the whole Holocene transgression period. Time averaging is high, especially in the lower core layers of Piran station, probably due to strong bioturbation. Surface mixed-layer assemblages tend to show right-skewed postmortem age-frequency distributions, whereas subsurface assemblages show unimodal or uniform shapes. Molluscan assemblages show significant interregional differences that correlate with sedimentation rate, grain size, and the occurrence of organic pollutants and heavy metals. Down-core changes in molluscan communities are also conspicuous in all cores. They partly reflect long-term changes in water depth, vegetation cover or grain size

  13. Off shore wind farms change the benthic pelagic coupling in the Belgian Part of the North Sea

    Science.gov (United States)

    Vanaverbeke, Jan; Coates, Delphine; Braeckman, Ulrike; Soetaert, Karline; Moens, Tom

    2016-04-01

    sediment matrix, will lead to a change in the biogeochemical properties of the sediment: highly reactive permeable sediments, poor in organic matter will shift towards sediment where organic matter will accumulate. Degradation of organic matter will then no longer be governed by physical processes, but mediated by biological processes (bioturbation, bio-irrigation).

  14. Spatial variability of soil parameters - subsoils as heterogenic environments

    Science.gov (United States)

    Heinze, Stefanie; John, Stephan; Kirfel, Kristina; Mikutta, Robert; Niebuhr, Jana; Preusser, Sebastian; Marschner, Bernd

    2014-05-01

    Subsoils are known to store a high amount of organic carbon (40-60% of the total C-pool). 14C-dating detected that in subsoils organic matter (OM) age increased with increasing depth and reaches several 1000 years. The high age of subsoil OM might be caused by a complex structure, by limited access of OM for microbial decomposition or a limited input of fresh organic material. The latter, mostly reaches the subsoil through special pathways, like root channels, bioturbation processes or preferential flow pathways where dissolved organic carbon will be transported. The spatially concentrated input of OM supposed that the heterogeneity of physical, chemical, and biological soil parameters is higher in subsoils than in top soils. Within the DFG-FOR 1806 we investigated the heterogeneity of soil parameters in soil profiles (top and subsoil) of a podzolic Cambisol in a 95 years old beech forest in Lower Saxony, Germany. Three transects were established with a vertical and horizontal dimension of 2.00m and 3.15m, respectively. 64 soil samples were taken out of a grid in 10, 35, 60, 85, 110, 135, 160 and 185m depth with increasing horizontal distance to a main tree. To analyze the variability and relationship of soil properties in the soil profiles, analysis of soil physical (e.g. texture), chemical (e.g. organic C, dissolved organic C, total N, pH), and biological (e.g. enzyme activities, microbial biomass C) parameters were conducted within the research group. The results showed a very strong decline of organic C from 1.15% (10cm) to 0.12% (60cm). The differences of SOC were not pronounced with increasing distance to the main tree. Also total nitrogen decreased between 10 and 60cm strongly from 0.05 to 0.005%. The pH showed a slight increase between 10 and 35cm from 3.51 up to 4.27. For microbial biomass measures the same stratification was detected but the variance within biological parameters were higher in the subsoil than in the topsoil. Enzyme activities showed a

  15. Spatial Distribution and Sedimentary Facies of the 2007 Solomon Islands Tsunami Deposits

    Science.gov (United States)

    Nakamura, Y.; Nishimura, Y.; Woodward, S.

    2007-12-01

    We conducted a field survey of the extent of damage, crustal deformation, and onshore deposits caused by 2007 Solomon Islands tsunami in Ghizo and adjacent islands in the western Solomon Islands, from 13th to 18th April, 2007. Our survey team was comprised of six Japanese and one American researcher. Three of us, the authors, mainly investigated tsunami deposits in three villages (Titiana, Suva, and Pailongge) in southern Ghizo Island. One member of our team re-investigated the deposits in June 2007. The tsunami generated sheet-like deposits of coral beach sand on the flat plain in Titiana. Beside the sea coast, the tsunami wave eroded ground surfaces and formed small scarps at 30 m from the sea. Just interior of the scarps, tsunami deposits accumulated up to 9 cm in thickness. The thickness decreased with distance from the sea and was also affected by microtopography. No sandy tsunami deposits were observed on the inland area between 170 m and 210 m from the sea. The upper boundary of inundation was recognized at about 210 m from the sea because of accumulation of driftwood and floating debris. In Suva and Pailongge, the outline of sand-sheet distribution is the same as it in Titiana. The tsunami had a maximum thickness of 10 cm and two or three sand layers are separated by thin humic sand layers. These humic layers were likely supplied from hillslopes eroded by the tsunami and transported by return-flows. These successions of deposits suggest that tsunami waves inundated at least two times. This is consistent with the number of large waves told by eyewitnesses. In the Solomon Islands, the plentiful rainfall causes erosion and resedimentation of tsunami deposits. Furthermore, the sedimentary structures will be destroyed by chemical weathering in warm and moist environment, and bioturbation by plants, animals, and human activities. The sedimentary structures had been preserved till the end of June 2007, but had already been penetrated by plant roots and sandpipes

  16. Nomination of the Globigerina Limestone of the Maltese Islands as a "Global Heritage Stone Resource"

    Science.gov (United States)

    Cassar, JoAnn

    2016-04-01

    The Maltese Islands consist of two main islands, Malta and Gozo, as well as a small number of islets, and lie in the central Mediterranean Sea approximately 90 km south of Sicily. Although only 316 square kilometres in size, the Islands contain a rich concentration of archaeological sites and historic buildings, as well as vernacular architecture and modern buildings, for the most part built of the local Globigerina Limestone, which is one of the few natural resources of the Islands. This stone can be described as a typical "soft limestone", very easy to carve and shape. It forms part of the large family of Oligo-Miocene "soft limestones" widely diffused in the Mediterranean Basin. The Maltese Globigerina Limestone Formation is one of five main Formations, and varies in thickness from 20 to over 200 m. The material used for building is located stratigraphically in the lower part of the Globigerina Limestone Formation, called the Lower Globigerina Limestone. This Formation is stratified into thick beds at outcrop. Sections where bioturbation is concentrated often also occur. This limestone is fine-grained, yellow to pale grey in colour, almost wholly composed of the tests of globigerinid planktonic foraminifera. Petrographically, Globigerina Limestone can be described as a bioclastic packstone, with bioclastic wackestones also occurring. This limestone has always been used as the predominant building material in the Islands. The Maltese prehistoric Temples, which were constructed approximately 6000 years ago, bear testimony to this. Between 1530 and 1798 the Order of the Knights of St John built kilometres of fortifications in this same material to protect the Island from the expanding Ottoman Empire. Fortifications, impressive churches, auberges and palaces were built of this stone during this period. The capital city of Valletta, a rich and dense manifestation of Baroque architecture in Globigerina Limestone, is included on the UNESCO World Heritage List, as are

  17. Impact of Marine Submergence and Season on Faunal Colonization and Decomposition of Pig Carcasses in the Salish Sea

    Science.gov (United States)

    Anderson, Gail S.; Bell, Lynne S.

    2016-01-01

    Pig carcasses, as human proxies, were placed on the seabed at a depth of 300 m, in the Strait of Georgia and observed continuously by a remotely operated camera and instruments. Two carcasses were deployed in spring and two in fall utilizing Ocean Network Canada’s Victoria Experimental Network under the Sea (formerly VENUS) observatory. A trial experiment showed that bluntnose sixgill sharks could rapidly devour a carcass so a platform was designed which held two matched carcasses, one fully exposed, the other covered in a barred cage to protect it from sharks, while still allowing invertebrates and smaller vertebrates access. The carcasses were deployed under a frame which supported a video camera, and instruments which recorded oxygen, temperature, salinity, density, pressure, conductivity, sound speed and turbidity at per minute intervals. The spring exposed carcass was briefly fed upon by sharks, but they were inefficient feeders and lost interest after a few bites. Immediately after deployment, all carcasses, in both spring and fall, were very rapidly covered in vast numbers of lyssianassid amphipods. These skeletonized the carcasses by Day 3 in fall and Day 4 in spring. A dramatic, very localized drop in dissolved oxygen levels occurred in fall, exactly coinciding with the presence of the amphipods. Oxygen levels returned to normal once the amphipods dispersed. Either the physical presence of the amphipods or the sudden draw down of oxygen during their tenure, excluded other fauna. The amphipods fed from the inside out, removing the skin last. After the amphipods had receded, other fauna colonized such as spot shrimp and a few Dungeness crabs but by this time, all soft tissue had been removed. The amphipod activity caused major bioturbation in the local area and possible oxygen depletion. The spring deployment carcasses became covered in silt and a black film formed on them and on the silt above them whereas the fall bones remained uncovered and hence

  18. Evaluating sensitivity of silicate mineral dissolution rates to physical weathering using a soil evolution model (SoilGen2.25)

    Science.gov (United States)

    Opolot, E.; Finke, P. A.

    2015-11-01

    Silicate mineral dissolution rates depend on the interaction of a number of factors categorized either as intrinsic (e.g. mineral surface area, mineral composition) or extrinsic (e.g. climate, hydrology, biological factors, physical weathering). Estimating the integrated effect of these factors on the silicate mineral dissolution rates therefore necessitates the use of fully mechanistic soil evolution models. This study applies a mechanistic soil evolution model (SoilGen) to explore the sensitivity of silicate mineral dissolution rates to the integrated effect of other soil-forming processes and factors. The SoilGen soil evolution model is a 1-D model developed to simulate the time-depth evolution of soil properties as a function of various soil-forming processes (e.g. water, heat and solute transport, chemical and physical weathering, clay migration, nutrient cycling, and bioturbation) driven by soil-forming factors (i.e., climate, organisms, relief, parent material). Results from this study show that although soil solution chemistry (pH) plays a dominant role in determining the silicate mineral dissolution rates, all processes that directly or indirectly influence the soil solution composition play an equally important role in driving silicate mineral dissolution rates. Model results demonstrated a decrease of silicate mineral dissolution rates with time, an obvious effect of texture and an indirect but substantial effect of physical weathering on silicate mineral dissolution rates. Results further indicated that clay migration and plant nutrient recycling processes influence the pH and thus the silicate mineral dissolution rates. Our silicate mineral dissolution rates results fall between field and laboratory rates but were rather high and more close to the laboratory rates possibly due to the assumption of far from equilibrium reaction used in our dissolution rate mechanism. There is therefore a need to include secondary mineral precipitation mechanism in our

  19. Community characteristics of macrobenthos in the Huanghe (Yellow River) Estuary during water and sediment discharge regulation

    Institute of Scientific and Technical Information of China (English)

    REN Zhonghua; LI Fan; WEI Jiali; LI Shaowen; LV Zhenbo; GAO Yanjie; CONG Xuri

    2016-01-01

    demonstrate that anthropogenic activity is having both long-term (3 decadal) and short term (1-month) impacts on the structure of the macrobenthic community of the Huanghe Estuary. In conclusion, human activities WSDR influence the habitat environment of macro benthos, including the water temperature, nutrients, bioturbation, and so on. Therefore, we suggest the necessity to strengthen regulations of land-derived organic pollutant input to maintain the ecological balance of the Huanghe Estuary.

  20. Imaging Reservoir Quality: Seismic Signatures of Geologic Processes

    Energy Technology Data Exchange (ETDEWEB)

    Department of Geophysics

    2008-06-30

    Lithofacies successions from diverse depositional environments show distinctive patterns in various rock-physics planes (velocity-porosity, velocity-density and porosity-clay). Four clear examples of decameter-scale lithofacies sequences are documented in this study: (1) Micocene fluvial deposits show an inverted-V pattern indicative of dispersed fabric, (2) a fining-upward sequence of mud-rich deep deposits shows a linear trend associated with laminated sand-clay mixtures, (3) sand-rich deposits show a pattern resulting from the scarcity of mixed lithofacies, and (4) a coarsening-upward sequence shows evidence of both dispersed and horizontally laminated mixed lithofacies, with predominating dispersed mixtures generated by bioturbation. It was observed that carbonate-cemented sandstones are extremely heterogeneous in the project deep-water study area. Those from the base of incisions are usually associated with lower shaliness, lower porosity and higher P-impedance, while from the top of flooding surfaces exhibit higher shaliness, higher porosity and lower P-impedance. One rock physics model that captures the observed impedance-porosity trend is the 'stiff-sand model'. For this model, the high-porosity end-member is unconsolidated sand whose initial porosity is a function of sorting and shaliness, while the low-porosity end-member is solid mineral. These two end points are joined with a Hashin-Shtrikman equation. A systematic variation of quartz:clay ratio from proximal to distal locations was observed in the study area even within a single facies. The quartz:clay ratio changes from [0.5:0.5] to [1:0] along the direction of flow, based on the trends of P-impedance vs. porosity as predicted by the rock model for uncemented sands. The results are in agreement with spill-and-fill sequence stratigraphic model in mini-basin setting. In addition, porosity at the distal location ({approx}25 % to 35%) is higher than the porosity at the proximal location ({approx

  1. Environmental Magnetism of mid-Pleistocene Lacustrine Sediments of the Valles Caldera, New Mexico

    Science.gov (United States)

    Hurley, L. L.; Geissman, J. W.; Fawcett, P.; Tim, W.; Goff, F.

    2007-12-01

    Rock magnetic measurements are applied to almost 80 m of lacustrine sediment (VC-3) to augment independent means of interpreting the environmental conditions of a mid-Pleistocene lake in the Valle Grande of the Valles Caldera, northern New Mexico. An age model for the core is pinned to an Ar/Ar age determination of 552 ± 3 ka for a sanidine bearing ash layer at 78 m depth and major transitions in the organic carbon record at 53 m, 40 m, 27 m, and 17 m; these data suggest that deposition of VC-3 spans MIS 14 to MIS 10, including glacial terminations VI (531 ka) and V (426 ka). AF demagnetization resolves positive inclination magnetizations from most of the core, consistent with Brunhes normal polarity. Three thin (magnetizations may indicate poorly-recorded geomagnetic polarity events at ~406 ka (11α), ~536 ka (14α) and the Big Lost excursion (~580 ± 8 ka). Data from an array of rock magnetic investigations indicate magnetite, titanomagnetite, and pyrhotite characterize VC-3 sediments. Susceptibility and frequency dependent susceptibility experiments at low temperature reveal an abundance of paramagnetic and super-paramagnetic material. Scanning electron microscopy of magnetic separates show an array of Fe-oxide and Fe-sulfide grains, including titanomagnetites with trellis ilmenite intergrowths. NRM intensities of sediment deposited during glacial periods typically range from 0.04 mA/m to values as high as 1.6 mA/m; interglacial sediment NRM intensities range from 0.05 mA/m to 0.2 mA/m. NRM values increase to 3.3 mA/m, between 48 m to 43 m, where the sediment exhibits shallow mud crack, bioturbation, and oxidation. Overall, trends in susceptibility, ARM, and SIRM are similar to those in NRM intensity. Bivariate plot of susceptibility/ARM shows little variation in concentration of low coercivity minerals (i.e. magnetite) in VC-3 sediments. Also, the concentration of high coercivity minerals (i.e. hematite) indicated by the IRM/susceptibility curve show similar

  2. The Jurassic of Denmark and Greenland: Volgian–Ryazanian ‘hot shales’ of the Bo Member (Farsund Formation in the Danish Central Graben, North Sea: stratigraphy, facies and geochemistry

    Directory of Open Access Journals (Sweden)

    Dybkjær, Karen

    2003-10-01

    Full Text Available Upper Jurassic – lowermost Cretaceous marine mudstones represent the most significant source of hydrocarbons in the Central and Northern North Sea. Of particular importance in the Danish sector of the Central Graben is a succession of radioactive ‘hot shales’ referred to the Bo Member, in the upper levels of the Farsund Formation (Kimmeridge Clay Formation equivalent. This mudstone-dominated succession is typically 15–30 m thick and has a total organic carbon (TOC content of 3–8%, though locally exceeding 15%. Although truncated on some structural highs, the Bo Member is a persistent feature of the Danish Central Graben. Lateral variation in boththickness and organic richness is attributed to intrabasinal structural topography and to the location of sediment input centres.Detailed study of the dinoflagellate cyst biostratigraphy of 10 wells indicates that the onset of enhanced organic carbon burial began in the middle–late Middle Volgian in this portion of theCentral Graben. The Bo Member, representing the peak of organic carbon enrichment, is largely of Early Ryazanian age. Core data (Jeppe-1, E-1 wells indicate that the organic-rich shales of theBo Member are not wholly of hemipelagic origin, as commonly assumed, but may locally be dominated by fine-grained turbidites. Absence of bioturbation, well-preserved lamination and high TOC values suggest that bottom waters were predominantly anoxic although the presenceof in-situ benthic bivalves at discrete horizons in the E-1 well suggests that suboxic conditions prevailed on occasion. The Bo Member is a good to very good source rock, showing very highpyrolysis yields (10–100 kg HC/ton rock and Hydrogen Index (HI values in the range 200–600. In particular, the Bo Member is characterised by an abundance of 28,30 bisnorhopane (H28, acompound that is indicative of anoxic environments. These new data from the Danish sector of the Central Graben are compatible with the model of Tyson et

  3. Decoupling of the Carbon Cycle during Ocean Anoxic Event-2

    Science.gov (United States)

    Eldrett, J.; Bergman, S. C.; Minisini, D.

    2013-12-01

    The Cenomanian to Turonian Boundary transition (95-93 Ma) represents one of the most profound global perturbations in the carbon cycle of the last 140 million years. This interval is characterized by widespread deposition of organic-rich fine-grained sediment marked by a globally recognised positive carbon isotope excursion (CIE) reflecting the widespread removal of 12C-enriched organic matter in marine sediments under global anoxic conditions. However, the exact timing and trigger of this inferred global phenomenon, termed Oceanic Anoxic Event-2 is still debated, with recent studies showing diachroneity between the deposition of the organic-rich sediment and the CIE, and conflicting interpretations on detailed redox analyses in several of these inferred anoxic settings. Here we present the first evidence for widespread and persistent oxygenation during OAE-2 based primarily on the distribution of redox-sensitive trace metals preserved in sediments from the Eagle Ford Formation, Western Interior Seaway of North America. We generated a δ13C curve which indicates an earlier initiation of the CIE in Texas compared to the Global Stratotype and Point Section at Pueblo, Colorado. Our data also indicate anoxic-euxinic conditions in the mid-late Cenomanian, but improved bottom-water oxygenation prior to and during the CIE, corroborated by increased bioturbation, abundance of benthic foraminifera and reduced total organic carbon values. Trace metal enrichments support large volumes of mafic volcanism possibly from the High Arctic Large Igneous Province (LIP), which occur during peak bottom-water oxygenation and a plateau in δ13Corg values and does not immediately precede the Cenomanian-Turonian CIE, as previously stated. This suggests that the emplacement of a LIP was not the primary trigger of the OAE-2 event. It is also unlikely that bottom-water oxygenation was promoted by the introduction of volcanogenic Fe inhibiting sulfate reduction, as the depletion in redox

  4. The distribution of depleted uranium contamination in Colonie, NY, USA

    International Nuclear Information System (INIS)

    Uranium oxide particles were dispersed into the environment from a factory in Colonie (NY, USA) by prevailing winds during the 1960s and '70s. Uranium concentrations and isotope ratios from bulk soil samples have been accurately measured using inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) without the need for analyte separation chemistry. The natural range of uranium concentrations in the Colonie soils has been estimated as 0.7-2.1 μg g-1, with a weighted geometric mean of 1.05 μg g-1; the contaminated soil samples comprise uranium up to 500 ± 40 μg g-1. A plot of 236U/238U against 235U/238U isotope ratios describes a mixing line between natural uranium and depleted uranium (DU) in bulk soil samples; scatter from this line can be accounted for by heterogeneity in the DU particulate. The end-member of DU compositions aggregated in these bulk samples comprises (2.05 ± 0.06) x 10-3235U/238U, (3.2 ± 0.1) x 10-5236U/238U, and (7.1 ± 0.3) x 10-6234U/238U. The analytical method is sensitive to as little as 50 ng g-1 DU mixed with the natural uranium occurring in these soils. The contamination footprint has been mapped northward from site, and at least one third of the uranium in a soil sample from the surface 5 cm, collected 5.1 km NNW of the site, is DU. The distribution of contamination within the surface soil horizon follows a trend of exponential decrease with depth, which can be approximated by a simple diffusion model. Bioturbation by earthworms can account for dispersal of contaminant from the soil surface, in the form of primary uranium oxide particulates, and uranyl species that are adsorbed to organic matter. Considering this distribution, the total mass of uranium contamination emitted from the factory is estimated to be c. 4.8 tonnes.

  5. The Messinian marine to nonmarine gypsums of Jumilla (Northern Betic Cordillera, SE Spain): Isotopic and Sr concentration constraints on the origin of parent brines

    Science.gov (United States)

    Rossi, Carlos; Vilas, Lorenzo; Arias, Consuelo

    2015-10-01

    The origin of the Messinian Hoya de la Sima (HS) gypsum (Betic foreland) is constrained using 87Sr/86Sr, δ34S, Sr concentration, and petrographic data. The Lower and Middle HS units consist of subaqueous vertically-aligned and stromatolitic selenites, the latter containing unusual microbial depositional textures. The Upper Unit consists of very-shallow-water bioturbated lenticular gypsum with Paracamelus ichnites. 87Sr/86Sr and δ34S indicate precipitation from predominantly marine waters, with upward increasing continental influence. Mixing models between Messinian seawater and continental water that dissolved Triassic evaporites show that the percentages of seawater required to explain the measured 87Sr/86Sr are analogous to the percentages obtained using δ34S, supporting precipitation from such mixtures. 87Sr/86Sr and δ34S of Lower HS selenites resemble those of the Primary Lower Gypsum (PLG) of the Messinian Salinity Crisis (MSC), in both cases indicating precipitation from seawater-continental water mixtures in which most Sr and SO4 were supplied by Messinian seawater. In the Lower HS selenites, Sr concentrations indicate contributing continental waters with Sr/Ca ratios similar to seawater. However, Sr concentrations of PLG selenites from other Betic basins (Bajo Segura, Sorbas indicate parent waters with Sr/Ca ratios lower than seawater. If the Sr contents of the betic PLG selenites are representative, it is unlikely that the Lower HS selenites represent the PLG. However, we cannot completely discard that option since different LPG subbasins could have had variable Sr/Ca. The HS gypsums formed coevally to diapirism of Triassic evaporites, in a restricted lagoonal basin developed during or slightly after a phase of strike-slip faulting in the Betic Cordillera. More general implications of this work are that Sr concentrations, combined with 87Sr/86Sr and δ34S data, provide key constraints on the origin of parent brines, and using Sr concentrations as

  6. Seabed Filter Feasibility Study of Om Almisk Island

    KAUST Repository

    Sesler, Kathryn

    2012-06-01

    Freshwater access has always been and is continuing to be a severe problem in desert coastal regions, despite the fact that they have an unlimited supply of easily accessible saline water. Water desalination plants are well established and heavily relied upon throughout the Middle East, Saudi Arabia in particular. However, water desalination tends to be a very expensive and energy intensive solution to the problem. The transition from using open water intake systems and all of the pretreatment processes that they require, to using seabed water filters as an intake, would potentially reduce the lifetime costs, energy consumption, and environmental impacts commonly associated with water desalination. This is because the filtration process that the seabed filter generates, serves as sufficient pretreatment for seawater as well as eliminating any risk of entrainment or impingement of marine organisms. The main objective of this research is to conduct a feasibility study on Om Almisk Island, an island off the coast of King Abdullah University of Science and Technology (KAUST), to determine if it would be a suitable location to construct a seabed water filter as a replacement for the current open water intake. The Om Almisk Island site was evaluated through collection of sand samples over a radial grid around Om Almisk Island and sample analysis using grain size distribution, porosity, and hydraulic conductivity. The lack of mud, high hydraulic conductivity, proximity to KAUST, and the shallow waters of the sandy apron surrounding Om Almisk Island make this an ideal location for a seabed water filter to be used as an intake and pretreatment for the KAUST desalination plant. This location also has low tide change and the presence of benthic macrofauna to create bioturbation in the sediments, which could inhibit the growth of a schmutzdecke. If this biological layer forms, it could drastically reduce the hydraulic conductivity of the system. Due to the high hydraulic

  7. A cross-section analysis of sedimentary organic matter in a mangrove ecosystem under dry climate conditions: The Somone estuary, Senegal

    Science.gov (United States)

    Sakho, Issa; Mesnage, Valérie; Copard, Yoann; Deloffre, Julien; Faye, Guilgane; Lafite, Robert; Niang, Isabelle

    2015-01-01

    Mangrove sediments are an important organic matter (OM) reservoir and play a major role in the carbon cycle. Since the 1990s, these ecosystems were subjected to numerous studies, in order to quantify the sedimentary sink for organic carbon (OC) and to characterize the organic matter sources, but remain poorly studied in Western Africa. The aim of our study is to quantify the organic carbon content and to identify the OM origin stored in the Somone mangrove sediments. Studied area is characterized by a (i) dry climate conditions with a higher rate of evaporation, (ii) lack of freshwater input by river, and (iii) tide dominated system. Here, we focus on physico-chemical properties of sediments (temperature, pH and redox), sediment grain size, water content, particulate organic carbon and dissolved organic carbon from a series of 40 cm-deep cores in four tidal contexts: mudflat, Rhizophora, and Avicennia mangroves and barren area. Results show that total organic carbon (TOC) contents range between 0.34 and 3.92 wt.% and are higher in sediments from mudflat and Rhizophora mangrove than in sediments from Avicennia mangrove and barren area. Indeed, sediments stored under Avicennia is subjected to suboxic conditions initiated by roots system and crabs bioturbation; while under Rhizophora and mudflat, local anoxic conditions are prevalent as suggest the negative Eh values and the occurrence of framboidal pyrites. Mangrove sediments of the Somone estuary contain an autochthonous lignocellulosic-derived organic matter. The youngest and stunted form of the Somone mangrove explains the low organic carbon content of sediments; where dry climate conditions limit the organic matter production by the mangrove forest. The shallow depth at which the organic matter of the former mudflat was found confirms that the Somone mangrove is subjected to a low sedimentation rate. This suggests that organic carbon burial depends on others processes than sedimentation. Then, in the Somone

  8. Ecohydrologic Investigations of Shallow Lateral Subsurface Flow in Tropical Soils using Time-Lapse Surface Electrical Resistivity Tomography

    Science.gov (United States)

    Ogden, F. L.; Mojica, A.; Abebe, N. A.; Smithsonian Tropical Research Institute, Panama Canal Watershed Experiment, Agua Salud Project

    2010-12-01

    The hydrologic effects of deforestation and aforestation in the tropics remain an area of active research. Hydrologic predictions of land-use change effects remain elusive. One of the unique features of catchment hydrology in the tropics is the effect of intense, continuous biological activity by insects, shrubs, trees, and small mammals. Sapprolitic soils derived from weathered bedrock cover widespread areas. These soils have low matrix permeabilities on the order of 1 mm/h, are 10 to 20 m in thickness and have relatively low activity because they have been depleted of light cations by annual rainfall over 2000 mm. As part of the Smithsonian Tropical Research Institute, Panama Canal Watershed Experiment, Agua Salud Project, we have observed shallow subsurface flow in tropical soils in central Panama using an introduced salinity contrast and surface electrical resistivity tomography (ERT). In 2009 and 2010, experiments were conducted in a 30 year-old secondary succession forest, and in two former pasture sites that were planted with native timber species and teak, respectively, in 2008. At each site, saline water (NaCl tagged with LiBr) was introduced to the soil using two different methods: soil pits and ponded surface applications. Results showed the strongest response in the case of ponded surface applications with observed changes in resistivity between -50% and 50%. In soil pit applications, the change in electrical resistivity varied from -10% to 10%. Results suggest that in the case of surface application, a transient perched water table is created near the bottom of the bioturbation layer that activates the downslope macropore network and results in bulk flow velocities that are significantly higher than observed soil matrix permeabilities. When heavy rainfall occurred during tests, increased mobility of the salinity contrast more clearly showed the active layer where most flow occurred. Time-series ERT observations enabled measurements of downslope bulk

  9. The distribution of depleted uranium contamination in Colonie, NY, USA

    Energy Technology Data Exchange (ETDEWEB)

    Lloyd, N.S., E-mail: nsl3@alumni.leicester.ac.uk [Department of Geology, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom); Chenery, S.R.N. [British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham, NG12 5GG (United Kingdom); Parrish, R.R. [Department of Geology, University of Leicester, University Road, Leicester, LE1 7RH (United Kingdom); NERC Isotope Geosciences Laboratory, Kingsley Dunham Centre, Keyworth, Nottingham, NG12 5GG (United Kingdom)

    2009-12-20

    Uranium oxide particles were dispersed into the environment from a factory in Colonie (NY, USA) by prevailing winds during the 1960s and '70s. Uranium concentrations and isotope ratios from bulk soil samples have been accurately measured using inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) without the need for analyte separation chemistry. The natural range of uranium concentrations in the Colonie soils has been estimated as 0.7-2.1 {mu}g g{sup -1}, with a weighted geometric mean of 1.05 {mu}g g{sup -1}; the contaminated soil samples comprise uranium up to 500 {+-} 40 {mu}g g{sup -1}. A plot of {sup 236}U/{sup 238}U against {sup 235}U/{sup 238}U isotope ratios describes a mixing line between natural uranium and depleted uranium (DU) in bulk soil samples; scatter from this line can be accounted for by heterogeneity in the DU particulate. The end-member of DU compositions aggregated in these bulk samples comprises (2.05 {+-} 0.06) x 10{sup -3235}U/{sup 238}U, (3.2 {+-} 0.1) x 10{sup -5236}U/{sup 238}U, and (7.1 {+-} 0.3) x 10{sup -6234}U/{sup 238}U. The analytical method is sensitive to as little as 50 ng g{sup -1} DU mixed with the natural uranium occurring in these soils. The contamination footprint has been mapped northward from site, and at least one third of the uranium in a soil sample from the surface 5 cm, collected 5.1 km NNW of the site, is DU. The distribution of contamination within the surface soil horizon follows a trend of exponential decrease with depth, which can be approximated by a simple diffusion model. Bioturbation by earthworms can account for dispersal of contaminant from the soil surface, in the form of primary uranium oxide particulates, and uranyl species that are adsorbed to organic matter. Considering this distribution, the total mass of uranium contamination emitted from the factory is estimated to be c. 4.8 tonnes.

  10. Soil and vegetation carbon stocks in Brazilian Western Amazonia: relationships and ecological implications for natural landscapes.

    Science.gov (United States)

    Schaefer, C E G R; do Amaral, E F; de Mendonça, B A F; Oliveira, H; Lani, J L; Costa, L M; Fernandes Filho, E I

    2008-05-01

    The relationships between soils attributes, soil carbon stocks and vegetation carbon stocks are poorly know in Amazonia, even at regional scale. In this paper, we used the large and reliable soil database from Western Amazonia obtained from the RADAMBRASIL project and recent estimates of vegetation biomass to investigate some environmental relationships, quantifying C stocks of intact ecosystem in Western Amazonia. The results allowed separating the western Amazonia into 6 sectors, called pedo-zones: Roraima, Rio Negro Basin, Tertiary Plateaux of the Amazon, Javari-Juruá-Purus lowland, Acre Basin and Rondonia uplands. The highest C stock for the whole soil is observed in the Acre and in the Rio Negro sectors. In the former, this is due to the high nutrient status and high clay activity, whereas in the latter, it is attributed to a downward carbon movement attributed to widespread podzolization and arenization, forming spodic horizons. The youthful nature of shallow soils of the Javari-Juruá-Purus lowlands, associated with high Al, results in a high phytomass C/soil C ratio. A similar trend was observed for the shallow soils from the Roraima and Rondonia highlands. A consistent east-west decline in biomass carbon in the Rio Negro Basin sector is associated with increasing rainfall and higher sand amounts. It is related to lesser C protection and greater C loss of sandy soils, subjected to active chemical leaching and widespread podzolization. Also, these soils possess lower cation exchangeable capacity and lower water retention capacity. Zones where deeply weathered Latosols dominate have a overall pattern of high C sequestration, and greater than the shallower soils from the upper Amazon, west of Madeira and Negro rivers. This was attributed to deeper incorporation of carbon in these clayey and highly pedo-bioturbated soils. The results highlight the urgent need for refining soil data at an appropriate scale for C stocks calculations purposes in Amazonia. There

  11. Upper Cretaceous chalk facies and depositional history recorded in the Mona-1 core, Mona Ridge, Danish North Sea: Plate 1

    Directory of Open Access Journals (Sweden)

    Surlyk, Finn

    2011-12-01

    Full Text Available The 331 m long core from the Mona-1 well in the Danish North Sea spans almost the entire Upper Cretaceous Chalk Group but only about 10% of Late Cretaceous time is represented. The succession comprises 14 facies representing pelagic deposition, turbidity flow, and mass-transport processes, including mudflow, debris flow, and slumping. Pelagic deposits vary mainly in terms of the concentration of siliciclastic material, the trace-fossil assemblage, and the presence or ab¬sence of primary sedimentary structures. Pelagic sedimentation was probably punctuated by the deposition of thin turbidites, and the resultant deposits were thoroughly bioturbated if deposited during normal oxygenation at the sea floor. Periodic benthic dysoxia resulted in the preservation of primary structures, as represented by laminated chalk which consists of thin pelagic laminae alternating with thin turbidites. In addition to the thin turbidites in the laminated chalk, four dif¬ferent turbidite facies are interpreted as representing high- to low-energy flows. Clast-supported chalk conglomerates have previously not been differentiated from other turbidites, but are here interpreted to be directly related to the down-slope evolution of debris flows. Debris flows are rep¬resented by matrix-supported conglomerates, which form one of the most common facies in the succession. High-concentration, gravity-driven suspension flows passed into dilute visco-plastic flows during the final stages of deposition and resulted in the deposition of structureless chalks. Limited shear deformation produced distinct quasi-facies from which the precursor facies can be deduced, whereas intense or continued shear deformation produced a shear-banded quasi-facies from which the precursor facies cannot be deduced in all cases. A series of major slump packages (14–18 in total are interpreted, forming over 40% of the succession; debrites appear to be the most common precursor facies involved in

  12. The Jurassic of Denmark and Greenland: An offshore transgressive–regressive mudstone-dominated succession from the Sinemurian of Skåne, Sweden

    Directory of Open Access Journals (Sweden)

    Surlyk, Finn

    2003-10-01

    Full Text Available A Sinemurian mudstone-dominated succession was exposed until recently in the Gantofta quarry in Skåne, southern Sweden. The deposits are placed in the Döshult and Pankarp Members of the Sinemurian–Aalenian Rya Formation. Similar facies of the same age are widespread in the Danish Basin where they constitute the F-Ib unit (F-I member of the Fjerritslev Formation. The Gantofta succession thus represents the easternmost extension of the environment characteristic of the Fjerritslev Formation and is essentially the only locality where it has been possible tostudy the facies of this formation in outcrop. Sedimentation seems to have taken place under relatively quiet tectonic conditions except for the possible fault-control of the basin margin. Thelower part of the Gantofta section is of Early and early Late Sinemurian age. It represents the upper part of the Döshult Member and consists of muddy, lower shoreface sandstones, abruptlyoverlain by dark, bioturbated, fossiliferous mudstones with thin storm siltstones and sandstones. They are overlain by the Upper Sinemurian Pankarp Member which comprises red-brown, restricted marine calcareous mudstones with an upwards increasing number of storm siltstones and sandstones reflecting general shallowing and shoreline progradation.The succession spans the greater part of two simple sequences with a distal sequence boundary located at the boundary between the Döshult Member and the Pankarp Member. The exposed part of the lower sequence includes a thick transgressive systems tract and a very thin highstand systems tract. The upper sequence is represented by an undifferentiated transgressive and highstand systems tract. An Early Sinemurian sea-level rise, a late Early Sinemurian highstand, an early Late Sinemurian fall and a Late Sinemurian minor rise and a major fall are recognised. Nearby boreholes show evidence for an end-Sinemurian – Early Pliensbachian major rise. This evolution corresponds well with

  13. Large-scale field study on thin-layer capping of marine PCDD/F-contaminated sediments in Grenlandfjords, Norway: physicochemical effects.

    Science.gov (United States)

    Cornelissen, Gerard; Amstaetter, Katja; Hauge, Audun; Schaanning, Morten; Beylich, Bjørnar; Gunnarsson, Jonas S; Breedveld, Gijs D; Oen, Amy M P; Eek, Espen

    2012-11-01

    A large-scale field experiment on in situ thin-layer capping was carried out in the polychlorinated dibenzodioxin and dibenzofuran (PCDD/F) contaminated Grenlandsfjords, Norway. The main focus of the trial was to test the effectiveness of active caps (targeted thickness of 2.5 cm) consisting of powdered activated carbon (AC) mixed into locally dredged clean clay. Nonactive caps (targed thickness of 5 cm) consisting of clay without AC as well as crushed limestone were also tested. Fields with areas of 10,000 to 40,000 m(2) were established at 30 to 100 m water depth. Auxiliary shaken laboratory batch experiments showed that 2% of the applied powdered AC substantially reduced PCDD/F porewater concentrations, by >90% for tetra-, penta- and hexa-clorinated congeners to 60-70% for octachlorinated ones. In-situ AC profiles revealed that the AC was mixed into the sediment to 3 to 5 cm depth in 20 months. Only around 25% of the AC was found inside the pilot fields. Sediment-to-water PCDD/F fluxes measured by in situ diffusion chambers were significantly lower at the capped fields than at reference fields in the same fjord, reductions being largest for the limestone (50-90%) followed by clay (50-70%), and the AC + clay (60%). Also reductions in overlying aqueous PCDD/F concentrations measured by passive samplers were significant in most cases (20-40% reduction), probably because of the large size of the trial fields. The AC was less effective in the field than in the laboratory, probably due to prolonged sediment-to-AC mass transfer times for PCDD/Fs and field factors such as integrity of the cap, new deposition of contaminated sediment particles, and bioturbation. The present field data indicate that slightly thicker layers of limestone and dredged clay can show as good physicochemical effectiveness as thin caps of AC mixed with clay, at least for PCDD/Fs during the first two years after cap placement. PMID:23046183

  14. Response of macrobenthic and foraminifer communities to changes in deep-sea environmental conditions from Marine Isotope Stage (MIS) 12 to 11 at the "Shackleton Site"

    Science.gov (United States)

    Rodríguez-Tovar, Francisco J.; Dorador, Javier; Martin-Garcia, Gloria M.; Sierro, Francisco J.; Flores, José A.; Hodell, David A.

    2015-10-01

    Integrative research including facies characterization, ichnological composition and foraminifer analysis has been conducted on cores from Site U1385 of the IODP Expedition 339 to evaluate the incidence of Marine Isotope Stage (MIS) 12 and MIS 11 on deep-sea environmental changes. Four color facies groups have been differentiated, showing variable transitions between them (bioturbated, gradual and sharp contacts). Trace fossil assemblage, assigned to the Zoophycos ichnofacies, consists of light and dark filled structures, with Alcyonidiopsis, Chondrites, Nereites, Planolites, Spirophyton, Thalassinoides, Thalassinoides-like structures, and Zoophycos. A deep-sea multi-tiered trace fossil community is interpreted, revealing predominance of well-oxygenated bottom and pore-waters, as well as abundance of food in the sediment for macrobenthic tracemaker community. Changes in environmental parameters are interpreted to be associated with significant variations in trace fossil distribution according to the differentiated intervals (A to M). Benthic foraminifer concentration in the sediments and variations of the planktonic foraminifer assemblages suggest significant changes in surface productivity and food supply to the sea floor since the ending of MIS 13 to the end of MIS 11 that could be correlated with the registered changes in facies and trace fossil assemblages. At the end of MIS 13 values of annual export productivity were very low, that together with the presence of light-color sediments and the continuous presence of light Planolites and Thalassinoides, reveal lower organic carbon flux to the bottom and high oxygen conditions (interval A). Afterwards the organic matter supply increased rapidly and remained very high until Termination V, determining an eutrophic environment, expressed by high benthic foraminifer accumulation rates, and reduced availability of oxygen, that correlate with the record of Spirophyton and Zoophycos, and the presence of Chondrites

  15. Reaction hotspots at micro- and macroscales: Challenges in early diagenetic modeling (Invited)

    Science.gov (United States)

    Meile, C. D.

    2010-12-01

    . This bottom-up approach is contrasted by the quantification of organic matter decomposition from a wide range of measurements. Data obtained in the field include direct rate measurements of select processes, concentration and flux measurements, and isotopic composition of bulk organic matter as well as specific molecules. Mathematical interpretation of these various signatures help to then constrain the breakdown of organic matter under a wider range of environmental conditions. A third and equally critical feature of porous media is the role of spatio-temporal patchiness in the distribution of reaction zones and the oscillatory nature of metabolic processes. Examples include the presence of hotspots in marsh settings associated with tidal flooding, soil horizons or bioturbated settings exhibiting redox oscillations, and aggregate structures with reducing microenvironments caused by transport limitations or because they contain elevated levels of electron donors. Due to the need for and the challenge associated with parameterization of complex semi-mechanistic models of biogeochemical reactions, the linkage between experimental and modeling efforts will be emphasized.

  16. Animating the biodynamics of soil thickness using process vector analysis: A dynamic denudation approach to soil formation

    Science.gov (United States)

    Johnson, D.L.; Domier, J.E.J.; Johnson, D.N.

    2005-01-01

    This paper expands the dynamic denudation framework of landscape evolution by providing new process insights and details on how soil and its signature morphological feature, the biomantle, form and function in the environment. We examine soils and their biomantles from disparate parts of the world, from the tropics through midlatitudes and hyperarid through perhumid, a range that exhibits varying environments for, and of, life. We then explicate the process pathways that cause soils to thicken and thin, and to even disappear, then reform. We do this by examining thickness relationships, where soil thickness stand biomantle thickness bt are functions of upbuilding u and deepening d minus removal r processes, hence st/bt=f(u+d-r). Upbuilding has two subsets, u1, which includes all exogenous (allochthonous-outside) mineral and/or organic inputs to the soil system, and u2, which includes all endogenous (autochthonous-in situ) processes and productions, including weathering. Exogenous u1 inputs include eolian and slopewash inputs (sedimentations) of mineral and organic materials, mass wasting accumulations and the like. Endogenous u2 processes and productions include the sum of in situ bioturbations, biosynthetic productions, organic accumulations, biovoid productions, weathering and volume increases caused by their sum. Endogenous upbuildings, which dominantly occur in the biomantle, are basically biodynamic bd processes and productions, hence u2=bd. Therefore, if exogenous upbuildings u1 are minimal or zero, then biomantle thickness bt is expressed by bt=f(u2-r) or bt=f(bd-r). Drawing on these relationships, we employ a graphic-conceptual device called process vector analysis in a digital animation (see supplementary materials or cf. https://netfiles.uiuc.edu/jdomier/www/temp/ biomantle.html) that illustrates the main pathways that form both Earth's soil and its unique epidermis, the biomantle. We then discuss the main elements of the animation using still frames that

  17. Changes in the redox state of sediments following the 2010 BP blowout

    Science.gov (United States)

    Hastings, D. W.; Brooks, G.; Hollander, D. J.; Larson, R. A.; Morford, J. L.; Romero, I.; Hammaker, S.; Hogan, A.; Roeder, T. K.

    2012-12-01

    We have collected multi-core sediment cores from over 40 sites along the NE Gulf of Mexico continental slope following the 2010 Deepwater Horizon oil spill. We present the geochemical results from four select sites collected on August 2010, December 2010, February 2011, September 2011, and August 2012. Cores were extruded at 2 mm intervals, and sediments were analyzed for TOC, 13C, carbonate, short-lived radioisotopes (Pb-210, Cs-137, Be-7, Th-234) and grain size. Cores reveal a well-defined, internally stratified dark brown layer in the top 1-6 cm, with finer grain size than underlying sediments. Samples were digested at high temperature and pressure in concentrated nitric acid to dissolve both the oil and authigenic fractions, but not the detrital component. Samples were subsequently analyzed by ICP-MS. Although the Macondo crude oil is slightly enriched in Ni, V, and Co, with concentrations of 2.8, 0.9, and 0.08ppm, respectively, no significant enrichment of these metals is observed in Gulf of Mexico sediments. Sediment mass accumulation rates following the event range from 0.6 - 20 g/cm2/yr, which are one to two orders of magnitude higher than pre-spill rates. Organic and inorganic carbon deposition rates from the 2010 and February 2011 cores are also elevated one to two orders of magnitude. 13C signatures of this recent deposited material are slightly depleted relative to pre-oil event material. Large sedimentation rates, depleted 13C values and lack of bioturbation on the surface of the deep sediments studied supports the hypothesis of a large sea-snow-like blizzard event during the oil-spill in 2010. Bacterially mediated oxidation of organic matter is reflected in a well-established sequence of oxidation-reduction reactions. We exploit redox sensitive trace elements including Mn, Fe, Re, U, Mo, and V to infer changes in the redox state of sediments following this large pulse of organic matter to the seafloor.

  18. Canada's National Building Stone: Tyndall Stone from Manitoba

    Science.gov (United States)

    Pratt, Brian R.; Young, Graham A.; Dobrzanski, Edward P.

    2016-04-01

    Tyndall Stone is a distinctively mottled and highly fossiliferous dolomitic limestone that belongs to the Selkirk Member of the Red River Formation, of Late Ordovician (Katian) age. It has been quarried at Garson, Manitoba, 37 km northeast of Winnipeg, since 1895, although other quarries in the area go back to 1832. Tyndall Stone, so named because it was shipped by rail from nearby Tyndall, is currently produced by Gillis Quarries Limited. It has various uses as a dimension stone. Large slabs, most often cut parallel to bedding, face the exterior or interior of many important buildings such as the Parliament Buildings and the Canadian Museum of Civilization in the Ottawa area, the Empress Hotel in Victoria, and the provincial legislatures in Winnipeg and Regina, as well as many commercial buildings especially in the Canadian prairies. At the quarries, the stone is cut vertically, using eight foot (2.44 m) diameter saws mounted on one hundred foot (30.5 m) tracks, then split into 6-8 tonne blocks that are moved using front-end loaders. Gillis Quarries operates a large finishing plant with an area of about 4000 m2. Stone is processed along advanced cutting lines that feature eight primary saws and six gantry saw stations, allowing it to be made into a variety of sizes, shapes, and finishes. The Selkirk Member is 43 m thick and the stone is extracted from a 6-8 m thick interval within the lower part. The upper beds tend to be more buff-coloured than the grey lower beds due to weathering by groundwater. The stone is massive, but extracted blocks are less than ~1m thick due to splitting along stylolites. Consisting of bioturbated wackestone to packstone, the Tyndall Stone was deposited in a shallow-marine environment within the photic zone, in the central part of the vast equatorial epicontinental sea that covered much of Laurentia. Scattered thin, bioclastic grainstone lenses record brief, low-energy storm events. The distinctive mottles are formed by dolomitized

  19. Sedimentary structures formed by upper-regime flows on a Pleistocene carbonate ramp (Favignana Calcarenite, Sicily, Italy)

    Science.gov (United States)

    Slootman, Arnoud; Moscariello, Andrea; Cartigny, Matthieu; de Boer, Poppe

    2015-04-01

    Antidune, chute-and-pool and cyclic step deposits are found in the outcrops of the Pleistocene calcarenite wedge of Favignana Island. These deposits were formed on a prograding carbonate ramp. Three zones are identified: inner-mid ramp (shoreface), ramp slope, and outer ramp (offshore). The ramp slope dips 3° to 10° and drops 30-40 m over 400-600 m. The ramp slope and outer ramp show a succession of bioturbated dune cross beds with up to 10 m-thick, intercalated event beds containing supercritical-flow structures. Grain sizes range from coarse sand to granules, with large rhodoliths (algal balls) and shells as gravel-sized clasts. It is our aim to provide insight into the processes that create upper-regime flow structures and the hydraulic parameters of their generating flows. During normal storms, wind-driven currents generated submarine dunes that migrated across the sea floor. During exceptional high-energy events (megastorms, tsunamis), large amounts of skeletal debris from the carbonate factory were transported towards the top of the ramp slope, where under the effect of gravity sustained supercritical sediment gravity flows were generated. In a case study of bedform evolution, we present the formation of a large downstream-asymmetric bedform with two antidunes superimposed on its upstream flank. A stepwise flow reconstruction reveals the progressive steepening of the antidunes until critical steepness is reached, and the first and, shortly after, the second antidune wave breaks. The two hydraulic jumps thus formed, developed a temporary cyclic step morphology (i.e. hydraulic jump, accelerating subcritical flow, supercritical chute, hydraulic jump etc.). The bedform geometries are used to reconstruct the nature of the catastrophic events that were active on the ramp slope. The wave length of the antidunes is measured from outcrop, which, through hydraulic equations, allows for estimation of mean flow velocity as a function of sediment concentration in the

  20. Modern non-tropical mixed carbonate-siliciclastic sediments and environments of the southwestern Gulf of California, Mexico

    Science.gov (United States)

    Halfar, Jochen; Ingle, James C.; Godinez-Orta, Lucio

    2004-03-01

    Modern mixed carbonate-siliciclastic warm-temperate environments were studied in the southern Gulf of California (GOC), Mexico. The combined heterozoan and photozoan character is defined by the absence of true coral reef structures, calcareous green algae and non-skeletal grains, and the dominance of rhodoliths (unattached coralline red algae), mollusks and small coral patch reefs. The major carbonate producing environments are pocket bays, a shallow carbonate bioherm, high-energy rocky and sandy shorelines and mid-shelf settings. Sediments characterizing the pocket bays display heavily bioturbated bioclastic wackestone and grainstone textures. The rhodolith dominated bioherm is composed of coarse sediments exhibiting grainstone and rudstone textures with fine material being winnowed away by tidal currents. Rocky and sandy shorelines are characterized by erosion and mixing of up to boulder size granitic and volcaniclastic material with coralline red algal and molluskan carbonates. The mid-shelf settings are defined by a silt and fine sand sized non-carbonate matrix mixed with abundant molluskan fragments and foraminifera. Peak carbonate production takes place between 10 and 15 m water depth; below 40 m production significantly decreases, combined with a steep increase in the amount of siliciclastics. This is in contrast to many temperate and cool-water mixed-carbonate siliciclastic systems, where most carbonate production occurs in mid- to outer shelf settings. A full spectrum of sediments from pure carbonates (90-100% carbonate), allochem carbonates (50-90% carbonate) and allochemic mud or sand (<50% carbonate) was encountered in the study area. The absence of early diagenetic binding and cementation of the non-tropical carbonates facilitates mixing of carbonates and siliciclastics. The latter are mainly derived from adjacent Tertiary volcaniclastics and Mesozoic granites. Mixing takes place (1) as punctuated mixing during periodic short-term storm or hurricane

  1. The ELSA-Flood-Stack: A reconstruction from the laminated sediments of Eifel maar structures during the last 60 000 years

    Science.gov (United States)

    Brunck, H.; Sirocko, F.; Albert, J.

    2016-07-01

    This study reconstructs the main flood phases in central Europe from event layers in sediment cores from Holocene Eifel maar lakes and Pleistocene dry maar structures. These reconstructions are combined with recent gauge time-series to cover the entire precipitation extremes of the last 60 000 years. In general, Eifel maar sediments are perfectly suited for the preservation of event layers since the deep water in the maar lakes is seasonal anoxic and therefore, bioturbation is low. However, the preservation of annual lamination is only preserved in Holzmaar and Ulmener Maar; the other cores are dated by 14C, magnetostratigraphy, tephra markers and ice core tuning. The cores were drilled in the Eifel region of central western Germany, which represents a climatic homogenous region from Belgium to Poland and all across Central Europe. A total of 233 flood layers over 7.5 mm were detected in all analysed cores. The stratigraphic classification of the flood events follows the newly defined Landscape Evolution Zones (LEZ). The strongest events in the Holocene have occurred during LEZ 1 (0-6000 b2k) in the years 658, 2800 and 4100 b2k. Flood layers in the LEZ 2 (6000-10 500 b2k) are not as frequent as during the LEZ 1, nevertheless, the floods cluster between 6000 and 6500 b2k. Twenty flood layers are found in the LEZ 3 (10 500-14 700 b2k); 11 in LEZ 4 (14 700-21 000 b2k); 15 in LEZ 5 (21 000-28 500 b2k); 34 in LEZ 6 (28 500-36 500 b2k); 8 in LEZ 7 (36 500-49 000 b2k); zero in LEZ 8 (49 000-55 000 b2k) and LEZ 9 (55 000-60 000 b2k). The maximum flood phases during the Pleistocene are at 11 500-17 500 (late glacial and Younger Dryas), 23 000-24 000 (before Greenland Interstadial (GI) 2), 29 000-35 000 (especially between GI 5 and 4) and 44 000-44 500 b2k (transition from GI 12 to 11). The variations in flood dynamics are climatically driven and mainly associated with climate transitions and colder periods, combined with light vegetation. It turns out that low vegetation

  2. Geological "Ground Truth" of Sea-level Highstand Events During Warm Interglaciations (MIS 11 and 5e): Taking the Punch out of Proxy Precision

    Science.gov (United States)

    Hearty, P. J.

    2005-12-01

    High-resolution sea-level records for marine isotope stages (MIS) 11 and 5e from coastal outcrops in Bahamas, Bermuda, Hawaii, and Western Australia provide physical confirmation of extreme ice-melting events during Pleistocene interglacials. Field evidence indicates MIS 11 sea level rose in a series of oscillations to c. +20 m, while that of MIS 5e reached its maximum of +6-10 m. Because these were brief events (100s yrs), their true magnitude is generally muted or obscured in deep-sea oxygen isotope records; generally averaged over thousands of years by the combined effects of sampling, bioturbation, and sedimentation rates. Further unresolvable variables such as temperature and salinity further cloud the isotope proxy record. Thus, the tangible rock record is of greatest importance in understanding the nature of these extreme events. Geomorphology, sedimentary structures, taphonomy of and dating of organisms, and petrology provide ground truth at field sites. Sea-level highstands preserve terraces and benches by erosion and subsequent deposition of sub- and intertidal sediments. Fenestral porosity is a measure of intertidal wetting and drying of sand, while decimetre-scale, high-angle cross beds of poorly-sorted sand and gravel indicate shallow subtidal conditions. In situ coral heads describe similar subtidal conditions. Delicate, sometimes partially articulated skeletons of birds and reptiles in sea caves reveal a protected shoreline. An early generation of isopachous, fibrous cement verifies the presence of marine phreatic water over a sustained period of time. These features, often misinterpreted (McMurtry, 2004, AGU Fall Meeting, OS21E-06), categorically exclude emplacement by tsunami waves. Oceanic isotope records cannot produce an equivalent level of resolution of short, extreme events via (in terms of age, duration, rates of sea-level and ice-volume changes), thus shifting the `burden of proof' to proxy methods to identify such events. In our quest to

  3. Methane and organic matter as sources for excess carbon dioxide in intertidal surface sediments of the German Wadden Sea

    Science.gov (United States)

    Böttcher, M. E.; Al-Raei, A. M.; Walpersdorf, E. C.; Heuer, V.; Hinrichs, K.; Hilker, Y.; Engelen, B.; Volkenborn, N.; Segl, M.

    2009-12-01

    terrestrial organic matter. (Biogenic) methane in hypersulfidic surface sands contained isotope signatures down to -65 per mil. Below reduced sandy surfaces, the isotopic composition of enhanced DIC down to -36 per mil indicate methane as a major source for the oxidized carbon pool. In contrast, DIC was less enriched in the lighter isotope below oxidized surface sands or mixed flats where oxidation of organic matter using oxygen and sulfate as electron acceptors dominated. At Sylt Island the effect of bioturbation and bioirrigation by dwelling organisms (lugworms Arenicola marina) on experimental field sites, was considered, too. In the top 10 cmbsf, highest SRR, DIC concentrations, and lightest C-13 signatures in DIC were observed during summer time with no contribution from CH4.

  4. Dissolved inorganic carbon and alkalinity fluxes from coastal marine sediments: model estimates for different shelf environments and sensitivity to global change

    Directory of Open Access Journals (Sweden)

    V. Krumins

    2012-07-01

    Full Text Available We present a one-dimensional reactive transport model to estimate benthic fluxes of dissolved inorganic carbon (DIC and alkalinity (AT from coastal marine sediments. The model incorporates the transport processes of sediment accumulation, molecular diffusion, bioturbation and bioirrigation, while the reactions included are the redox pathways of organic carbon oxidation, re-oxidation of reduced nitrogen, iron and sulfur compounds, pore water acid-base equilibria, and dissolution of particulate inorganic carbon (calcite, aragonite, and Mg-calcite. The coastal zone is divided into four environmental units with different particulate inorganic carbon (PIC and particulate organic carbon (POC fluxes: reefs, banks and bays, carbonate shelves and non-carbonate shelves. Model results are analyzed separately for each environment and then scaled up to the whole coastal ocean. The model-derived estimate for the present-day global coastal benthic DIC efflux is 126 Tmol yr−1, based on a global coastal reactive POC depositional flux of 117 Tmol yr−1. The POC decomposition leads to a~carbonate dissolution from shallow marine sediments of 7 Tmol yr−1 (on the order of 0.1 Pg C yr−1. Assuming complete re-oxidation of aqueous sulfide released from sediments, the effective net flux of alkalinity to the water column is 29 Teq yr−1, primarily from PIC dissolution (46% and ammonification (33%. Because our POC depositional flux falls in the high range of global values given in the literature, the reported DIC and alkalinity fluxes should be viewed as upper-bound estimates. Increasing coastal seawater DIC to what might be expected in year 2100 due to the uptake of anthropogenic CO2 increases PIC dissolution by 2.3 Tmol yr−1 and alkalinity efflux by 4.8 Teq yr−1. Our reactive transport modeling approach not only yields global estimates of benthic DIC, alkalinity

  5. Flux and accumulation of sedimentary particles off the continental slope of Pakistan: a comparison of water column and seafloor estimates from the oxygen minimum zone, NE Arabian Sea

    Directory of Open Access Journals (Sweden)

    H. Schulz

    2013-07-01

    Full Text Available Due to the lack of bioturbation, the laminated muds from the oxygen-minimum zone (OMZ off Pakistan provide a unique opportunity to precisely determine the vertical and lateral sediment fluxes in the near shore part of the northeastern Arabian Sea, and to explore the effects of the margin topography and the low oxygen conditions on the accumulation of organic matter and other particles. West of Karachi, in the Hab river area of EPT and WPT (Eastern and Western PAKOMIN Traps, 16 short sediment profiles from water depths between 250 m and 1970 m on a depth transect crossing the OMZ (~ 120 to ~ 1200 m water depth were investigated, and correlated on the basis of a thick, light-gray- to reddish-colored turbidite layer. Varve counting yielded a date for this layer of AD 1905 to 1888. We adopted the young age which agrees with 210Pb- dating, and used this isochronous stratigraphic marker bed to calculate sediment accumulation rates, that we could directly compare with the flux rates from the sediment traps installed within the water column above. All traps in the area show exceptionally high, pulsed winter fluxes of up to 5000 mg m−2 d−1 in this margin environment. The lithic flux at the sea floor is as high as 4000 mg m−2 d−1 , and agrees remarkably well with the bulk winter flux of material. This holds as well for the individual bulk components (organic carbon, calcium carbonate, opal, lithic fraction. However, the high winter flux events (HFE by their extreme mass of remobilized matter terminated the recording in the shallow traps by clogging the funnels. Based on our comparisons, we argue that HFE for the past 5000 yr most likely occurred as regular events within the upper OMZ off Pakistan. Coarse fraction and foraminiferal accumulation rates from sediment surface samples along the Hab transect show distribution patterns that seem to be a function of water depth and distance from the shelf. Some of these sediment fractions show sudden

  6. {sup 239+240}Pu in the Barents Sea Regions. Sources and radioecological assessment

    Energy Technology Data Exchange (ETDEWEB)

    Iosjpe, Mikhail [Norwegian Radiation Protection Authority, P.O. Box 55, N-1332 Oesteraas (Norway)

    2014-07-01

    The radioecological assessment for {sup 239+240}Pu in the Barents sea regions was made using the compartment modelling approach. The following sources of radioactive contamination were under consideration: global fallout from atmospheric testing of nuclear weapons, transport of {sup 239+240}Pu from the Sellafield and La Hauge nuclear plants and underwater testing of nuclear weapons in Chernaya Bay, Novaya Zemlya. The box model developed at NRPA uses a modified approach for compartmental modeling, which takes into account the dispersion of radionuclides over time. The box structures for surface, mid-depth and deep water layers have been developed based on the description of polar, Atlantic and deep waters in the Arctic Ocean and the Northern Seas, as well as site-specific information for the boxes. The volume of the three water layers in each box has been calculated using detailed bathymetry together with Geographical Information Systems. The box model includes the processes of advection of radioactivity between compartments, sedimentation, diffusion of radioactivity through pore water in sediments, resuspension, mixing due to bioturbation, particle mixing and a burial process for radionuclides in deep sediment layers. Radioactive decay is calculated for all compartments. The contamination of biota is further calculated from the known radionuclide concentrations in filtered seawater in the different water regions. Doses to man are calculated on the basis of seafood consumptions, in accordance with available data for seafood catches and assumptions about human diet in the respective areas. Dose to biota are determined on the basis of calculated radionuclide concentrations in marine organisms, water and sediment, using dose conversion factors. Results of the calculations show that atmospheric deposition is the dominant source for the Barents Sea, except for the Chernaya Bay region. It is also demonstrated that the impact of the Sellafield nuclear facilities has

  7. Radioecological assessment of marine environment: complexity, sensitivity and uncertainties

    Energy Technology Data Exchange (ETDEWEB)

    Iosjpe, Mikhail [Norwegian Radiation Protection Authority, P.O. Box 55, N-1332 Oesteraas (Norway)

    2014-07-01

    A compartment modelling approach is widely used to evaluate the consequences after the release of radionuclides into the marine environment, by taking into account: (i) dispersion of radionuclides in water and sediment phases, (ii) bioaccumulation of radionuclides in biota and (iii) dose assessments for marine organisms and human populations. The NRPA box model includes site-specific information for the compartments, advection of radioactivity between compartments, sedimentation, diffusion of radioactivity through pore water in sediment, resuspension, mixing due to bioturbation, particle mixing, a burial process for radionuclides in deep sediment layers and radioactive decay. The contamination of biota is calculated from the known radionuclide concentrations in filtered seawater in the different water regions. Doses to man are calculated on the basis of seafood consumption, in accordance with available data for seafood catches and assumptions about human diet in the respective areas. Dose to biota is calculated on the basis of radionuclide concentrations in marine organisms, water and sediment, using dose conversion factors. This modelling approach requires the use of a large set of parameters (up to several thousand), some of which have high uncertainties linked to them. This work consists of two parts: A radioecological assessment as described above, and a sensitivity and uncertainty analysis, which was applied to two release scenarios: (i) a potential accident with a nuclear submarine and (ii) unit uniform atmospheric deposition to selected marine areas. The sensitivity and uncertainty analysis is based on the calculation of local and global sensitivity indexes, and then compare this approach to the Monte-Carlo Methods. The simulations clearly demonstrate the complexities encountered when using the compartment modelling approach. It is shown that the results can strongly depend on the time being analyzed. For example, the change of a given parameter may either

  8. Paleoenvironmental reconstruction of the coastal Monte Léon and Santa Cruz formations (Early Miocene) at Rincón del Buque, Southern Patagonia: A revisited locality

    Science.gov (United States)

    Raigemborn, M. Sol; Matheos, Sergio D.; Krapovickas, Verónica; Vizcaíno, Sergio F.; Bargo, M. Susana; Kay, Richard F.; Fernicola, Juan C.; Zapata, Luciano

    2015-07-01

    Sedimentological, ichnological and paleontological analyses of the Early Miocene uppermost Monte León Formation and the lower part of the Santa Cruz Formation were carried out in Rincón del Buque (RDB), a fossiliferous locality north of Río Coyle in Santa Cruz Province, Patagonia, Argentina. This locality is of special importance because it contains the basal contact between the Monte Léon (MLF) and the Santa Cruz (SCF) formations and because it preserves a rich fossil assemblage of marine invertebrates and marine trace fossils, and terrestrial vertebrates and plants, which has not been extensively studied. A ˜90 m-thick section of the MLF and the SCF that crops out at RDB was selected for this study. Eleven facies associations (FA) are described, which are, from base to top: subtidal-intertidal deposits with Crassotrea orbignyi and bioturbation of the Skolithos-Cruziana ichnofacies (FA1); tidal creek deposits with terrestrial fossil mammals and Ophiomorpha isp. burrows (FA2); tidal flat deposits with Glossifungites ichnofacies (FA3); deposits of tidal channels (FA4) and tidal sand flats (FA5) both with and impoverish Skolithos ichnofacies associated; marsh deposits (FA6); tidal point bar deposits recording a depauperate mixture of both the Skolithos and Cruziana ichnofacies (FA7); fluvial channel deposits (FA8); fluvial point bar deposits (FA9); floodplain deposits (FA10); and pyroclastic and volcaniclastic deposits of the floodplain where terrestrial fossil mammal remains occur (FA11). The transition of the MLF-SCF at RDB reflects a changing depositional environment from the outer part of an estuary (FA1) through the central (FA2-6) to inner part of a tide-dominated estuary (FA7). Finally a fluvial system occurs with single channels of relatively low energy and low sinuosity enclosed by a broad, low-energy floodplain dominated by partially edaphized ash-fall, sheet-flood, and overbank deposits (FA8-11). Pyroclastic and volcaniclastic materials throughout the

  9. Pore Water Circulation in Isolated Wetlands: Implications to Internal Nutrient Loading.

    Science.gov (United States)

    Bhadha, J. H.; Perkins, D. B.; Jawitz, J. W.

    2005-12-01

    feature because large vertical changes in chemical composition of the pore water could be useful in calculating potential diffusive fluxes associated with pore water circulation. While the concentration of macro-nutrients such as total phosphorus (TP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP) and total organic carbon (TOC) showed a general depleting trend from the sediment-water interface downward, the dissolved oxygen (DO) concentration fluctuated between 6.55 to 1.69 mg/L. The nonzero concentrations of oxygen could indicate the lack of complete microbial reduction of the oxygen in the pore water, more likely the result of advective mixing of the pore water due to bioturbation.

  10. Early Callovian ingression in southwestern Gondwana. Palaeoenvironmental evolution of the carbonate ramp (Calabozo Formation) in southwestern Mendoza, Neuquen basin, Argentina

    Science.gov (United States)

    Armella, Claudia; Cabaleri, Nora G.; Cagnoni, Mariana C.; Panarello, Héctor O.

    2013-08-01

    The carbonatic sequence of the Calabozo Formation (Lower Callovian) developed in southwestern Gondwana, within the northern area of the Neuquén basin, and is widespread in thin isolated outcrops in southwestern Mendoza province, Argentina. This paper describes the facies, microfacies and geochemical-isotopic analysis carried out in five studied localities, which allowed to define the paleoenvironmental conditions of a homoclinal shallow ramp model, highly influenced by sea level fluctuations, where outer, mid and inner ramp subenvironments were identified. The outer ramp subenvironment was only recognized in the south of the depocenter and is characterized by proximal outer ramp facies with shale levels and interbedded mudstone and packstone layers. The mid ramp subenvironment is formed by low energy facies (wackestone) affected by storms (packstones, grainstones and floatstones). The inner ramp subenvironment is the most predominant and is characterized by tidal flat facies (wackestones, packstones and grainstones) over which a complex of shoals (grainstones and packstones) dissected by tidal channels (packstone, grainstones and floatstones) developed. In the north area, protected environment facies were recorded (bioturbated wackestones and packstones). The vertical distribution of facies indicates that the paleoenvironmental evolution of the Calabozo Formation results from a highstand stage in the depocenter, culminating in a supratidal environment, with stromatolitic levels interbedded with anhydrite originated under restricted water circulation conditions due to a progressive isolation of the basin. δ13C and δ18O values of the carbonates of the Calabozo Formation suggest an isotopic signature influenced by local palaeoenvironmental parameters and diagenetic overprints. The δ13C and δ18O oscillations between the carbonates of the different studied sections are related with lateral facies variations within the carbonate ramp accompanied with dissimilar

  11. Evaluating Multi-Proxy Records of Paleocyclones in Florida Coastal Sediments

    Science.gov (United States)

    Hart, M. R.; Jaeger, J. M.

    2002-12-01

    this include: (1) the vegetation separating the ponds from the beach may prevent much of the overwash from reaching the ponds and (2) bioturbation within the ponds would cause a mixing of the sediments that would destroy storm-produced bedding.

  12. The Submarine Paleoseismic Recording Threshold of Shallow Cascadia Earthquakes Under a Wide Variety of Site Conditions

    Science.gov (United States)

    Black, B.; Goldfinger, C.; Patton, J. R.; Morey, A. E.; Galer, S.; Hausmann, R. B.

    2015-12-01

    The triggering, recording, and preservation of seismoturbidites depends on thresholds for each step that involve slope stability, shear strength, sediment supply, bioturbation and other factors. An important factor is the triggering distances for earthquakes of varying magnitudes from a given site. Data from paleoseismic studies globally (Japan, Taiwan, Sumatra, Black Sea, Sea of Marmara, Portugal, Haiti, California Borderlands, Monterey Bay, alpine lakes in Chile, Lake Washington, and southern Cascadia lakes) were compiled as a basis for comparison between sites. A limited assessment of site conditions such as across strike vs. along strike position of core sites, fault type, directivity, and Q value was included. Global averages suggest an MMI of 5.5 and distance of ~ 50-100 km is most common. Maximum triggering distances were estimated as 60-120 km for the CSZ, and 40-75 km for the NSAF based on existing data and comparisons to global values. The region between Eel Canyon and Mendocino Channel (CSZ) and Noyo Canyon (NSAF) has a higher likelihood of recording at least a portion of past seismicity from both the NSAF and CSZ, though Noyo Canyon is likely at the limit of possible influence from the CSZ. The high seismoturbidite frequency (240 yrs. vs. 500 yrs. in Washington) of southern Cascadia (excluding the Eel system) shows clear continuity along strike nearly bed for bed over 170 km (cores, CHIRP profiles), crossing four canyon systems. The record shows a weak relationship to sediment supply from the canyons, and no relationship to slope angle, recently suggested as an explanation. The average axial slope is 3-6 o for these systems, with a few short pitches of 12-20 o. By comparison, the lower frequency record at Hydrate Ridge (~ 350 yrs.) has a steeper average source slope of 10o, steep 20-30 o pitches and no modern sediment supply. The turbidite frequency at the base of the upper reach of Quinault Canyon is lower still (~ 500 years), but the source slope

  13. Seasonal dynamics of surface runoff in mountain grassland ecosystems differing in land use

    Science.gov (United States)

    Leitinger, Georg; Tasser, Erich; Newesely, Christian; Obojes, Nikolaus; Tappeiner, Ulrike

    2010-05-01

    SummaryBetter understanding of surface runoff quantity for distinct hydrological units becomes increasingly important as many rainfall-runoff models use static surface runoff coefficients and neglect key factors affecting ecohydrological dynamics, e.g. land cover and land use. Especially in small-scale alpine catchments, surface runoff and its contribution to mountain torrent runoff is frequently underestimated. In our study, the seasonal variability of surface runoff on abandoned areas and pastures in the alpine catchment 'Kaserstattalm' (Stubai Valley, Austria, Eastern Alps) was analyzed using a rain simulator along with soil water content ( SWC) and soil water tension ( SWT) measurements. Additionally, seasonal variability of soil physical and soil hydraulic properties were assessed. Analyzing more than 30 rainfall simulations on 10 m 2 plots at a rate of 90 mm h -1 (equivalent to convective precipitation events with 100 years return period) revealed a mean surface runoff coefficient of 0.01 on abandoned areas and 0.18 on pastures. Regarding seasonal variability, relevant surface runoff was limited to pastures in autumn with a maximum runoff coefficient of 0.25. The field capacity ( Fc) of all soils was found to be stable throughout the season. However, for pastures, cattle trampling led to a significant increase of dry bulk density ( BD) of up to +0.33 g cm -3 ( p ⩽ 0.01) in the top 0.1 m of the soil which is attributed to a compaction of macropores. Although measured infiltration rates decreased by more than 60%, BD could 'recover' during the winter season presumably due to freezing-and-thawing cycles and bioturbation processes decreasing soil compaction. This study highlights that impacts of land-use changes on soil physical properties make surface runoff difficult to model. Moreover, dynamic and interactive behaviour of soil parameters have to be considered in order to make realistic assessments and accurate predictions of surface runoff rates. Finally

  14. Rhythmic bedding in prodeltaic deposits of the ancient Colorado River: Exploring genetic processes

    Science.gov (United States)

    Waresak, Sandra; Nalin, Ronald; Lucarelli, Andrea

    2016-04-01

    Prodeltaic deposits represent a valuable archive for the characterization of deltaic depositional systems, offering a distal, minimally reworked record of dominant processes active at the fluvial-marine interface. The Fish Creek Basin (CA, US) preserves a ~ 3-km thick, lower Pliocene, progradational deltaic succession formed when the ancestral Colorado River infiltrated a marine rift basin (the early Gulf of California). The unit in this succession interpreted as prodeltaic, corresponding to the upper Mud Hills Member of the Deguynos Formation, consists of ~ 300 m of muddy siltstones. A striking attribute of parts of this unit is the presence of rhythmic bedding, with consistently alternating silt- to fine sand-dominated and clay-dominated beds forming couplets with an average thickness of 12 cm. By performing a detailed sedimentological analysis of the rhythmites and investigating periodicities in bed thickness, our study aimed at reconstructing the mode of deposition of this enigmatic prodeltaic succession. We measured at high stratigraphic resolution 265 consecutive couplets, for a total thickness of 33 m. Individual beds have good lateral persistence of at least tens of meters and gradational to sharp, flat contacts. Observed sedimentary structures are concentrated on the coarser portion of the couplets and mostly consist of parallel and wavy lamination, with subordinate ripple cross-lamination and localized internal scours. Bioturbation appears low in intensity or absent. Most notably, grain size analysis performed with laser diffraction techniques on several couplets shows a consistent pattern of inverse grading transitioning to normal grading. The cumulative evidence of these sedimentological features indicates that deposition of the rhythmites was accomplished via hyperpycnal flows, each couplet most likely representing an individual event in a setting characterized by high overall depositional rates. We performed time series analysis on bed thickness of

  15. Shallow lacustrine system of the Permian Pedra de Fogo Formation, Western Gondwana, Parnaíba Basin, Brazil

    Science.gov (United States)

    Araújo, Raphael Neto; Nogueira, Afonso César Rodrigues; Bandeira, José; Angélica, Rômulo Simões

    2016-04-01

    The Permian Period of the Parnaíba Basin, northern Brazil, represented here by deposits from the Pedra de Fogo Formation, records important events that occurred in Western Gondwana near its boundary with the Mesozoic Era. The analysis of outcrop based facies from the Permian Pedra de Fogo Formation, which is 100 m thick, carried out along the eastern and western borders of the Parnaiba Basin, allowed the identification of eleven sedimentary facies, which were grouped into three distinct facies associations (FA), representative of a shallow lacustrine system associated with mudflats and ephemeral rivers. Bioturbation, desiccation cracks, silcretes and various siliceous concretions characterize the Pedra de Fogo deposits. The FA1 mudflat deposits occur predominantly at the base of the Pedra de Fogo Formation and consist of laminated claystone/mudstone, mudcrack-bearing sandstones/mudstones and sandstones exhibiting cross-lamination, massive and megaripple bedding. Popcorn-like silicified nodules and casts indicate evaporite deposits. Other common features are silica concretions, silicified tepees and silcretes. FA2 represents nearshore deposits and consists of fine-grained sandstones with evenly parallel lamination, climbing ripple cross-lamination, massive and megaripple bedding and mudstone/siltstone showing evenly parallel lamination. FA3 refers to wadi/inundite deposits, generally organized as fining-upward cycles of metric size, composed of conglomerates and medium-grained pebbly sandstones showing massive bedding and cross-stratification, as well as claystone/siltstone showing evenly parallel to undulate lamination. Scour-and-fill features are isolated in predominantly tabular deposits composed of mudstones interbedded with fine to medium-grained sandstones showing planar to slightly undulate lamination. Silicified plant remains previously classified as belonging to the Psaronius genus found in the uppermost levels of the Pedra de Fogo Formation, near the

  16. An ichnofabric approach to the depositional interpretation of the intensely burrowed Bateig Limestone, Miocene, SE Spain

    Science.gov (United States)

    de Gibert, Jordi M.; Goldring, Roland

    2007-01-01

    The foraminiferal-rich pelagic Bateig Limestone forms several varieties of the important building stones quarried at Bateig Hill in southeastern Spain. Three principal ichnofabrics ( Bichordites, mottled- Palaeophycus and mottled- Ophiomorpha) are recognized, which are present in at least two (possibly up to four) repeated successions (cycles). Each succession begins with an erosional event. The Bichordites ichnofabric represents a new type of facies, formed as thin turbidity/grain flow, stratiform units derived from sediment slips off a fault into deep water. Each slipped unit became almost completely bioturbated by infaunal echinoids, colonizing by lateral migration. Because of the thinness of the units, successive colonizations tended to truncate the underlying burrows giving rise to a pseudo-stratification. As the Bichordites ichnofabric accumulated on the fault apron, thus reducing the effective height of the fault scarp, the substrate gradually came under the influence of currents traversing the shelf. This led to a change in hydraulic regime, and to the mottled- Palaeophycus and mottled- Ophiomorpha ichnofabrics in sediment deposited under bed load transport, and associated with laminar and cross-stratified beds and local muddy intervals. Reactivation of the fault triggered erosion and channeling and a return to grain flow sedimentation, and to the Bichordites ichnofabric of the succeeding cycle. The highest unit of the Bateig Limestone is formed entirely of cross-stratified calcarenites with occasional Ophiomorpha ( Ophiomorpha-primary lamination ichnofabric) and is similar to many shallow marine facies but they still bear a significant content of pelagic foraminifera. The sedimentary setting bears resemblance with that described for the Pleistocene Monte Torre Paleostrait and the modern Strait of Messina (Italy), where the narrow morphology of the depositional area enhanced tidal currents and allowed for high-energy sandy deposition in relatively deep

  17. A chain of processes - from past climate variations to paleoclimate reconstructions

    Science.gov (United States)

    Rehfeld, Kira; Laepple, Thomas

    2014-05-01

    dependence of the proxy interpretation on the archive type, location and recording seasonality. We identify common challenges such as bioturbation in marine or lacustrine sediments, and isotopic diffusion in ice-cores which both lead to a smoothing of the resulting signal. Where proxy communities have developed successful solutions or coping strategies, these could be useful for other types of paleoclimate data. Besides our goal to recognize cross-pollination potential we determine archive-proxy combinations that provide complementing climate information. Ultimately, the emerging proxy panorama will improve the potential of paleoclimate reconstructions and will contribute to a better understanding and reduction of uncertainties and caveats in paleoclimate data analysis. In order to populate and cross-reference the proxy network further we explicitly welcome and rely on the opportunity for feedback and discussion with experts at the EGU General Assembly 2014.

  18. Inventory and burial fluxes of Black Carbon in the Swedish continental shelf sediments

    Science.gov (United States)

    Sánchez-García, L.; Cato, I.; Gustafsson, Ö.

    2009-04-01

    Highly condensed black carbon (BC) particles, mainly derived from incomplete combustion of biomass and fossil fuel, are involved in several important processes in the biogeosphere [1], including sedimentary carbon burial, sequestration of organic pollutants in soils and sediments, affecting Earth's radiative heat balance and even human respiratory health. BC is commonly found to constitute several to 20% of total sedimentary carbon, and thus plays an important but poorly constrained role in the global biogeospheric carbon cycle. Sequestration of biogenic carbon as BC is a direct sink of the element from the rapidly cycling atmosphere-biosphere reservoirs, whereas burial of petrogenic/fossil BC is simply a conversion of one form of geological carbon to another [2]. Considerable emphasis has been made on the relevant role this recalcitrant form of organic matter (OM) may play on the global C cycle and yet large uncertainty exists around BC detection and quantification. This work seeks to provide a large-scale estimate of the reservoir and burial sink flux of BC in sediments from the extensive Swedish continental shelf (SCS), as a first approach to global inventories. To this end, a total of 120 sediment samples were collected from the Exclusive Economic Zone (EEZ) along the ?2000 km SCS stretch. The most recalcitrant fraction of the sedimentary OM was isolated and determined by means of a commonly applied method in biogeochemical studies of soils and sediments: chemo-thermal oxidation at 375˚ C in air (CTO-375). The obtained BC concentration was used to estimate the inventory and burial flux of BC in the SCS surface sediments, following [3], which takes into account key geophysical and geochemical properties of the nine distinct sedimentary regimes of the SCS that was separately assessed. Globally representative values of the sediment properties (e.g. density of dried sediments, bioturbated mixing depth, sedimentation rate or porosity over the mixed depth) were

  19. Transfer and mobility of trace metallic elements in the sedimentary column of continental hydro-systems

    International Nuclear Information System (INIS)

    In freshwater systems, trace metal pollutants are transferred into water and sedimentary columns under dissolved forms and/or fixed onto solid particles. Accumulated in the sedimentary areas, these latter ones can constitute important stocks of materials and associated pollutants and may impair water quality when environmental changes lead to increase their mobility. The mobility of the stocks of pollutants is mainly depending on the erosion, on the interstitial diffusion of the mobile phases (dissolved and colloidal) and on the bioturbation. In this context, this study involves the analysis of the mobility by interstitial diffusion. This topic consists in studying trace metal fractionation between their mobile (dissolved and colloidal) and non mobile (fixed onto the particles) forms. This point is governed by sorption/desorption processes at the particle surfaces. These processes are regulated by physico-chemical parameters (pH, redox potential, ionic strength...) and are influenced by biogeochemical reactions resulting from the oxidation of the organic matter by the microbial activity. These reactions generate vertical profiles of nutrients and metal concentrations along the sedimentary column. To understand these processes, this work is based on a mixed approach that combines in situ, analysis and modelling. In situ experimental part consists in sampling natural sediments cores collected at 4 different sites (1 site in Durance and 3 sites on the Rhone). These samples are analyzed according to an analytical protocol that provides the vertical distribution of physicochemical parameters (pH, redox potential, size distribution, porosity), nutrients and solid - liquid forms of trace metals (cobalt, copper, nickel, lead, zinc). The analysis and interpretation of these experimental results are based on a model that was developed during this study and that includes: 1) model of interstitial diffusion (Boudreau, 1997), 2) biogeochemical model (Wang and Van Cappellen

  20. Toward a Better Approach to Data-Model Comparison

    Science.gov (United States)

    Dowsett, H. J.; Robinson, M. M.; Salzmann, U.

    2015-12-01

    The quantitative census of a typical faunal assemblage recovered from a deep-sea core sample is the result of an integration of many different factors including but not limited to environmental (e.g., temperature, salinity, dissolved oxygen, nutrient availability, etc.), temporal (e.g., cycle of annual productivity), and pre- and post-depositional processes (e.g., dissolution, preservation potential, bioturbation, etc.). Extraction of a single environmental variable (e.g., temperature) requires poorly supported assumptions that introduce additional error and results in loss of valuable information contained within the assemblage. Conversely, temperatures generated by a numerical climate model for a given locale do not have any associated error. Thus, comparison of faunal assemblage-based temperature estimates with simulated temperatures from GCMs is an oversimplification of a complex system. It is critical that like data sets are compared. For example, proxies for temperature may estimate conditions at the surface or at various depths or during particular seasons. These estimates are not directly comparable, and pooling Mg/Ca, alkenone and assemblage-based estimates of ocean temperature is inherently wrong. A more appropriate data-model comparison would involve comparing the faunal assemblage found in a core sample to one estimated by a paleoecological model driven by a GCM. An ideal comparison would score a suite of environmental factors gleaned from a faunal assemblage with those simulated by a GCM. Quantification of these factors, however, is not practical in some cases. A paradigm shift in marine paleoclimate reconstruction is overdue, and comparison of paleoenvironments to model simulations requires a revised approach. The PRISM4 reconstruction presents a holistic and nuanced interpretation of multidimensional oceanographic processes and responses that is lost when reduced to a single variable such as temperature. Beyond the global approach, we incorporate

  1. Dissolved inorganic carbon and alkalinity fluxes from coastal marine sediments: model estimates for different shelf environments and sensitivity to global change

    Directory of Open Access Journals (Sweden)

    V. Krumins

    2013-01-01

    Full Text Available We present a one-dimensional reactive transport model to estimate benthic fluxes of dissolved inorganic carbon (DIC and alkalinity (AT from coastal marine sediments. The model incorporates the transport processes of sediment accumulation, molecular diffusion, bioturbation and bioirrigation, while the reactions included are the redox pathways of organic carbon oxidation, re-oxidation of reduced nitrogen, iron and sulfur compounds, pore water acid-base equilibria, and dissolution of particulate inorganic carbon (calcite, aragonite, and Mg-calcite. The coastal zone is divided into four environmental units with different particulate inorganic carbon (PIC and particulate organic carbon (POC fluxes: reefs, banks and bays, carbonate shelves and non-carbonate shelves. Model results are analyzed separately for each environment and then scaled up to the whole coastal ocean. The model-derived estimate for the present-day global coastal benthic DIC efflux is 126 Tmol yr−1, based on a global coastal reactive POC depositional flux of 117 Tmol yr−1. The POC decomposition leads to a carbonate dissolution from shallow marine sediments of 7 Tmol yr−1 (on the order of 0.1 Pg C yr−1. Assuming complete re-oxidation of aqueous sulfide released from sediments, the effective net flux of alkalinity to the water column is 29 Teq. yr−1, primarily from PIC dissolution (46% and ammonification (33%. Because our POC depositional flux falls in the high range of global values given in the literature, the reported DIC and alkalinity fluxes should be viewed as upper-bound estimates. Increasing coastal seawater DIC to what might be expected in year 2100 due to the uptake of anthropogenic CO2 increases PIC dissolution by 2.3 Tmol yr−1and alkalinity efflux by 4.8 Teq. yr−1. Our reactive transport modeling approach not only yields global estimates of benthic DIC

  2. Ação dos térmitas no solo Termites action on the soil

    Directory of Open Access Journals (Sweden)

    Eric Victor de Oliveira Ferreira

    2011-05-01

    Full Text Available A ordem Isoptera é bastante conhecida pelo seu potencial como praga, apesar dos cupins-praga constituírem a minoria dentro do grupo. Os cupins (térmitas são invertebrados dominantes em ambientes terrestres tropicais e estão espalhados desde as florestas úmidas até as savanas, sendo encontrados até mesmo em regiões áridas, nos mais variados habitats. Esses insetos têm um papel destacado e ainda pouco estudado nos ecossistemas tropicais. Ciclagem de nutrientes, aeração, infiltração de água do solo, bioturbação, formação de agregados e decomposição de material orgânico, são processos influenciados pela ação dos térmitas, que vão, direta ou indiretamente, influenciar a formação dos solos e da paisagem onde se encontram. Sugerimos que uma maior abordagem deva ser dirigida em futuras pesquisas para a influência desses insetos no solo sob condições específicas de uso e manejo, na produção sustentável de alimentos e nas mudanças climáticas.The order Isoptera is well known by its potential as a plague, although the number of species that are plagues is small within the group. Termites are the dominant invertebrates in tropical terrestrial environments and are spread from tropical rainforests to the savannahs, being found even in arid regions, in various habitats. These insects have a major role and are still little studied in tropical ecosystems. Nutrient cycling, aeration, water infiltration of soil, bioturbation, aggregates formation and organic material decomposition, are processes influenced by the action of termites, which , directly or indirectly, affect soil and landscape formation wherever they are. We suggest that a better approach must be addressed in future researches about these insects influence in the soil under specified conditions of use and management, in sustainable food production and climate changes.

  3. Quaternary Antarctic ice-sheet fluctuations and Southern Ocean palaeoceanography: natural variability studies at the Antarctic CRC

    International Nuclear Information System (INIS)

    and carbonate radiocarbon dating. Measurements of unsupported 230Th and 231Pa may allow estimation of accumulation rates, although dating techniques using these radioisotopes require uniform sedimentation rates, which may not (and probably do not) apply to these cores. The principal chronostratigraphic tool employed in this work is radiocarbon dating of sedimentary bulk organic carbon (the cores contain ∼1-2% organic carbon). Radiocarbon ages have been determined by accelerator mass spectrometry (AMS) at the Australian Nuclear Science and Technology Organisation facility at Lucas Heights, New South Wales, or at the Rafter Radiocarbon Laboratory of the New Zealand Institute of Geological and Nuclear Sciences. In addition, unsupported 210Pb was measured in the core-top subsamples by gamma spectrometry at the University of Hawaii, in an effort to evaluate recent accumulation rates, bioturbation, and core-top loss

  4. Impact of Marine Submergence and Season on Faunal Colonization and Decomposition of Pig Carcasses in the Salish Sea.

    Science.gov (United States)

    Anderson, Gail S; Bell, Lynne S

    2016-01-01

    Pig carcasses, as human proxies, were placed on the seabed at a depth of 300 m, in the Strait of Georgia and observed continuously by a remotely operated camera and instruments. Two carcasses were deployed in spring and two in fall utilizing Ocean Network Canada's Victoria Experimental Network under the Sea (formerly VENUS) observatory. A trial experiment showed that bluntnose sixgill sharks could rapidly devour a carcass so a platform was designed which held two matched carcasses, one fully exposed, the other covered in a barred cage to protect it from sharks, while still allowing invertebrates and smaller vertebrates access. The carcasses were deployed under a frame which supported a video camera, and instruments which recorded oxygen, temperature, salinity, density, pressure, conductivity, sound speed and turbidity at per minute intervals. The spring exposed carcass was briefly fed upon by sharks, but they were inefficient feeders and lost interest after a few bites. Immediately after deployment, all carcasses, in both spring and fall, were very rapidly covered in vast numbers of lyssianassid amphipods. These skeletonized the carcasses by Day 3 in fall and Day 4 in spring. A dramatic, very localized drop in dissolved oxygen levels occurred in fall, exactly coinciding with the presence of the amphipods. Oxygen levels returned to normal once the amphipods dispersed. Either the physical presence of the amphipods or the sudden draw down of oxygen during their tenure, excluded other fauna. The amphipods fed from the inside out, removing the skin last. After the amphipods had receded, other fauna colonized such as spot shrimp and a few Dungeness crabs but by this time, all soft tissue had been removed. The amphipod activity caused major bioturbation in the local area and possible oxygen depletion. The spring deployment carcasses became covered in silt and a black film formed on them and on the silt above them whereas the fall bones remained uncovered and hence

  5. An Integrated Geochemical and Paleontological Investigation of Environmental and Biotic Change Associated with Late Devonian Mass Extinctions in the Appalachian Basin, USA

    Science.gov (United States)

    Haddad, E.; Love, G. D.; Boyer, D.; Droser, M. L.

    2012-12-01

    window maturity levels from Rock-Eval pyrolysis confirm that these units are appropriate for organic geochemical analyses. No appreciable amount of aromatic carotenoid biomarkers diagnostic for green sulfur bacteria (isorenieratane and aryl isoprenoids) has been detected as yet at any of the Appalachian localities, which line of evidence favors a local paleoredox model without a persistently shallow sulfidic zone. Thus, photic zone euxinia is not always associated with extinction horizons in the Late Devonian, though it is possible that a complex redox stratified water column with an oscillating chemocline existing for extended periods below photic zone water depths (>100 m depth) was the depositional setting in the marine realm around ocean margins. The trace fossil record through the uK black shale interval complements the geochemical proxies; the presence of horizons with abundant bioturbation between well-laminated intervals provides biological support for intermittently oxygenated bottom waters.

  6. Co-evolution of Eukaryotes and Ocean and Atmosphere Oxygenation in the Neoproterozoic and Paleozoic Eras

    Science.gov (United States)

    Lenton, T. M.; Daines, S. J.; Mills, B.; Boyle, R. A.

    2014-12-01

    The nature, timing and cause(s) of the Earth's second oxygenation event are widely debated. It has been argued that there was a single pronounced rise in atmospheric oxygen toward present levels in the Late Neoproterozoic, which in turn triggered the evolution of animals. Here we suggest a more complex co-evolutionary scenario, with fluctuations in ocean and atmosphere oxygenation in the Late Neoproterozoic and Early Paleozoic caused partly by the evolution of animals, followed by a pronounced rise of atmospheric oxygen to present levels later in the Paleozoic caused by the rise of land plants. Current geochemical evidence suggests some parts of the deep oceans became oxygenated during the Ediacaran, but there was subsequent de-oxygenation of the ocean during the Cambrian that may have persisted into the Ordovician. Only later in the Paleozoic is there evidence for widespread oxygenation of the deep ocean, together with charcoal indicating atmospheric oxygen had approached present levels. The limited Neoproterozoic oxygenation of the ocean could be explained by the evolution of filter-feeding sponges removing oxygen demand from the water column and encouraging a shift from cyanobacteria to faster-sinking eukaryotic algae, which transferred oxygen demand to greater depths and into sediments. The resulting oxygenation of shelf bottom waters would have increased phosphorus removal from the ocean thus lowering global productivity and oxygen demand in a positive feedback loop encouraging ocean oxygenation [1]. The subsequent Cambrian de-oxygenation of the ocean could be explained by the evolution of bioturbating animals oxygenating the sediments and thus lowering the C/P burial ratio of organic matter, reducing organic carbon burial and lowering atmospheric oxygen [2]. The later rise of land plants, selectively weathering phosphorus from continental rocks and producing recalcitrant high C/P biomass, increased organic carbon burial and atmospheric oxygen, finally

  7. High-resolution topography using SfM-photogrammetry from UAV for coastal mudflat geomorphic surveys

    Science.gov (United States)

    Fleury, Jules; Brunier, Guillaume; Michaud, Emma; Anthony, Edward; Morvan, Sylvain; Dussouillez, Philippe; Gardel, Antoine

    2016-04-01

    The coast between the Amazon and the Orinoco river mouths comprises mud banks formed from the large muddy discharge of the Amazon and migrating westward under the influence of waves and currents. These banks are highly dynamic and strongly affected by complex hydro-bio-geochemical interactions that are also important in mangrove colonization of bare mudflats in the upper intertidal zone of these banks. The surface topography of these mud banks is further affected by physical and biological processes such as tidal channel incision and bioturbation. Surveying the morphology of these mudflats over large areas and at a high-resolution without perturbing their surface is a real challenge that cannot be accomplished using classical survey methods such as RTK-GPS or Total Stations. To overcome this hurdle, we conducted a SfM(Surface from Motion)-photogrammetry experiment over 1 ha of a large intertidal mudflat colonized by pioneer mangroves at the mouth of the Sinnamary estuary in French Guiana. We developed a topographic data acquisition system based on sub-vertical aerial photography from a UAV flying at low altitude (15 m), in order to produce images at 3 mm resolution. A light DJI F550 drone was used, with an automatic flight programming using GPS navigation and a flight plan designed on photogrammetric criteria. The payload was a lightweight (250 grams) Ricoh GR camera with an APS-C sensor of 16.2 Megapixel and including an intervalometer triggering function. The drone had a flight autonomy of 12 minutes thus covering entirely the surrounding mudflat platform. The landing procedure was conducted manually in order for the drone to land safely on a very narrow artificial ground base set up for our experiment. 3D-models and derived products were generated using Agisoft Photoscan Professionnal software. We produced a gridded Digital Surface Model (DSM) and an orthophoto in visible bands at 1 cm and 5mm pixel resolution respectively. The vertical accuracy of the DSM based

  8. Biogenic habitat transitions influence facilitation in a marine soft-sediment ecosystem.

    Science.gov (United States)

    Lohrer, Andrew M; Rodil, Iván F; Townsend, Michael; Chiaroni, Luca D; Hewitt, Judi E; Thrush, Simon F

    2013-01-01

    Habitats are often defined by the presence of key species and biogenic features. However, the ecological consequences of interactions among distinct habitat-forming species in transition zones where their habitats overlap remain poorly understood. We investigated transition zone interactions by conducting experiments at three locations in Mahurangi Harbour, New Zealand, where the abundance of two habitat-forming marine species naturally varied. The two key species differed in form and function: One was a sessile suspension-feeding bivalve that protruded from the sediment (Atrina zelandica; Pinnidae); the other was a mobile infaunal urchin that bioturbated sediment (Echinocardium cordatum; Spatangoida). The experimental treatments established at each site reflected the natural densities of the species across sites (Atrina only, Echinocardium only, Atrina and Echinocardium together, and plots with neither species present). We identified the individual and combined effects of the two key species on sediment characteristics and co-occurring macrofauna. After five months, we documented significant treatment effects, including the highest abundance of co-occurring macrofauna in the Atrina-only treatments. However, the facilitation of macrofauna by Atrina (relative to removal treatments) was entirely negated in the presence of Echinocardium at densities >10 individuals/m2. The transitional areas in Mahurangi Harbour composed of co-occurring Atrina and Echinocardium are currently widespread and are probably more common now than monospecific patches of either individual species, due to the thinning of dense Atrina patches into sparser mixed zones during the last 10-15 years. Thus, although some ecologists avoid ecotones and habitat edges when designing experiments, suspecting that it will skew the extrapolation of results, this study increased our understanding of benthic community dynamics across larger proportions of the seascape and provided insights into temporal

  9. Partitioning the contributions of mega-, macro- and meiofauna to benthic metabolism on the upper continental slope of New Zealand: Potential links with environmental factors and trawling intensity

    Science.gov (United States)

    Leduc, Daniel; Pilditch, Conrad A.; Nodder, Scott D.

    2016-02-01

    be explained by benthic communities shifting towards smaller body size following physical disturbance. Future studies of deep-sea benthic ecosystem function will need to quantify the indirect influence of fauna on microbial metabolism through activities such as feeding and bioturbation in order to better understand the total contribution of benthic fauna to benthic processes.

  10. Possible Impact Origin for the Late Ordovician Bear Swamp Structure in the Finger Lakes Region of New York

    Science.gov (United States)

    Leiphart, D.

    2010-12-01

    Impact structures, or astroblemes, are one of rarest formations in the geologic record. Presently there are 176 confirmed impact structures on the planet with roughly two-thirds of them evident at the surface. A potential impact structure has been discovered in a 3D seismic survey in the Finger Lakes Region of upstate New York (Figure 1 - N42o43.187’; W76o16.637’). The Bear Swamp crater is uppermost Ordovician (~444 Ma) in age and is situated within the fluvial-deltaic to shallow marine Queenston Formation. This nearly circular structure measures 3.5 km (2.2 mi) in diameter and is completely buried in the subsurface at a depth of approximately 1,220 m (4,000 ft). Seismic data show a central uplift within the crater that rises about 160 m (525 ft) above the base. Around the central uplift is an annular basin that is more than 300 m (~1,000 ft) thick and is characterized by synformal seismic reflectors (Figure 1). This three-dimensional morphology resembles other complex craters of confirmed impact origin. Two exploration wells were drilled into the crater and image logs were run. The first well tested the central rebound which consists of steeply dipping beds and heavily brecciated zones. The second well was drilled in the annular basin which contains alternating sequences of chaotic zones and shallow dipping beds. Based on analogous impact structures, this crater fill is here interpreted as resurge breccias and turbidites which were the result of intense wave action in the moments after impact. Above these impact-related deposits lies a zone of very thin (~2cm) laminae which resemble varved sediments in lacustrine environments. A bioturbated zone overlies these thin laminae, which is in turn capped by the End Ordovician unconformity. Observations of both seismic and well data are consistent with a shallow marine to transition zone impact origin for the Bear Swamp crater. Figure 1: Location map showing the area of the ~180 km2 (70 mi2) 3D seismic survey and the

  11. Vertical and Interfacial Transport in Wetlands (Invited)

    Science.gov (United States)

    Variano, E. A.

    2010-12-01

    The objective of this work is to understand the fluxes connecting the water column, substrate, and atmosphere in wetland environments. To do this, analytical, numerical, and laboratory models have been used to quantify the hydrodynamic contributions to vertical fluxes. A key question is whether the hydrodynamic transport can be modeled as a diffusivity, and, if so, what the vertical structure of this diffusivity is. This question will be addressed in a number of flow types and for a number of fluxes. The fluxes of interest are heat, sediment, dissolved gases (such as methane and oxygen) and other dissolved solutes (such as nutrients and pollutants). The flows of interest include: unidirectional current, reversing flow (under waves, seiches, and tides), wind-sheared surface flows, and thermal convection. Rain and bioturbation can be important, but are not considered in the modeling work discussed herein. Specifically, we will present results on gas transport at wind-sheared free surface, sediment transport in unidirectional flow, and heat transfer in an oscillating flow cause by a seiche. All three of these will be used to consider the question of appropriate analytical models for vertical transport. The analytic models considered here are all 1D models that assume homogeneity in the horizontal plane. The numerical models use finite element methods and resolve the flow around individual vegetation stems in an idealized geometry. Laboratory models discussed herein also use an idealized geometry. Vegetation is represented by an array of cylinders, whose geometry is modeled after Scirpus spp. wetlands in Northern California. The laboratory model is constructed in a way that allows optical access to the flow, even in dense vegetation and far from boundaries. This is accomplished by using fluoropolymer plastics to construct vegetation models. The optical access allows us to employ particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) to measure

  12. Benthic flux of nutrients and trace metals in the northern component of San Francisco Bay, California

    Science.gov (United States)

    Kuwabara, James S.; Topping, Brent R.; Parcheso, Francis; Engelstad, Anita C.; Greene, Valerie E.

    2009-01-01

    ). These initial diffusive-flux estimates are greater than those measured in the South Bay using core-incubation experiments, which include bioturbation and bioirrigation effects, but they are nevertheless probably one to t

  13. Making a black shale shine: the interaction of hydrothermal fluids and diagenetic processes

    Science.gov (United States)

    Gleeson, Sarah; Magnall, Joe; Reynolds, Merilie

    2016-04-01

    Hydrothermal fluids are important agents of mass and thermal transfer in the upper crust. This is exemplified by shale-hosted massive sulphide deposits (SHMS), which are anomalous accumulations of Zn and Pb sulphides (± barite) in sedimentary basins created by hydrothermal fluids. These deposits occur in passive margin settings and, typically, there is no direct evidence of magmatic input. Recent studies of Paleozoic deposits in the North American Cordillera (MacMillan Pass and Red Dog Districts) have shown that the deposits are formed in a sub-seafloor setting, where the potential for thermal and chemical gradients is high. Mineralization is characterized by the replacement and displacement of unconsolidated, partially lithified and lithified biosiliceous mudstones (± carbonates), and commonly the sulphide mineralization post-dates, and replaces, bedded barite units in the sediments. The Red Dog District (Alaska, USA) contain some of the largest Zn-Pb deposits ever discovered. The host-rocks are dominantly carbonaceous mudstones, with carbonate units and some radiolarites. The ore forms massive sulphide bodies that replace pyritized mudstones, barite and carbonate units. Lithological and textural relationships provide evidence that much of the ore formed in bioturbated, biosiliceous zones that may have had high primary porosity and/or permeability. Sediment permeability may have been further modified by aging of the silica rich sediments and the dissolution/replacement of carbonate and barite beds. At the Tom and Jason deposits (MacMillan Pass, Yukon) the fault-controlled hydrothermal upflow zone is uniquely preserved as an unequivocal vent complex. Here, the metal bearing fluids are hot (300°C), low salinity (6 wt% NaCl equiv.) and acidic (pH Red Dog deposits, reduced sulphur was generated during open system diagenesis and euxinic conditions were not present at the time of mineralization. Furthermore, the formation of diagenetic barite provided an important

  14. Impact of typhoon disturbance on the diversity of key ecosystem engineers in a monoculture mangrove forest plantation, Can Gio Biosphere Reserve, Vietnam

    Science.gov (United States)

    Diele, K.; Tran Ngoc, D. M.; Geist, S. J.; Meyer, F. W.; Pham, Q. H.; Saint-Paul, U.; Tran, T.; Berger, U.

    2013-11-01

    ecosystem engineering activities are still performed. However, bioturbation may be reduced as crab biomass and body size were smaller in the gaps. Follow-up assessments and field experiments are needed to understand the crabs' role in processing the woody debris, their long-term community dynamics and possible feed-backs between species shifts and gap regeneration.

  15. Carbonate-associated sulfate in lucinid (Bivalvia) shells

    Science.gov (United States)

    Peng, Y.; Bao, H.; Anderson, L.; Engel, A. S.

    2007-12-01

    . These data suggest that 1) pore-water sulfate in shallow sediments is highly heterogeneous in its concentration and isotope composition, probably due to active microbial sulfate reduction, bioturbation, and water-pumping by bivalves and other infaunal filter feeders; 2) CAS is derived from ambient porewater or pumped-in seawater for infauna or epifauna, as well as for lucinids; and 3) CAS concentration and isotope compositions are vulnerable to later diagenetic processes.

  16. Carbon Storage of Three Natural Mangrove Forests in Gaoqiao, Zhanjiang%广东湛江高桥三个天然红树林的土壤碳库

    Institute of Scientific and Technical Information of China (English)

    许方宏; 张进平; 张倩媚; 林康英; 林广旋

    2012-01-01

    陆地生态系统土壤有机质(SOM)的碳动态研究已引起科学界的广泛关注,对海陆交错带的相关研究则较少.本研究选取位于广东湛江红树林保护区高桥三个天然红树林群落土壤剖面,采用C同位素方法测定了土壤有机碳(SOC)含量.结果表明,地表l00cm土壤碳库分别为:桐花树(Aegiceras comiculatum)群落碳库量较大,达673.2Mg/ha,而木榄(Bruguiera gymnonRhiza)+秋茄(Kandelia candel)群落为371.9Mg/ha,白骨壤(Avicennia marina)群落为325.2Mg/ha.有机质分解过程、植物根系分泌物和凋落物的差异、潮汐作用、群落演替阶段以及生物干扰等,都会对红树林土壤的碳动态产生一定的影响.%Steadily increasing concentrations of atmospheric CO2 have drawn considerable worldwide attention to the carbon dynamics of soil organic matter (SOM) under different vegetative conditions. We examined the soil profiles of three natural mangrove stands in Zhanjiang, Southern China, comparing their soil organic carbon (SOC) content In the upper 100cm, the carbon storage values in the Aegiceras comiculatum, Bruguiera gymnorrhiza+ Kandelia candel, and Avicennia marina profiles were 673.2, 371.9, and 325.2Mg/ha, respectively. The depositions such as root and litter and other processes, such as tidal influences, successional stages, and bioturbation, also contributed to this kind of pattern.

  17. Geologic framework, hydrostratigraphy, and ichnology of the Blanco, Payton, and Rough Hollow 7.5-minute quadrangles, Blanco, Comal, Hays, and Kendall Counties, Texas

    Science.gov (United States)

    Clark, Allan K.; Golab, James A.; Morris, Robert E.

    2016-09-13

    ­stratigraphic units (from top to bottom) the Bulverde, Little Blanco, Twin Sisters, Doeppenschmidt, Rust, and Honey Creek hydrostratigraphic units.This study used the ichnofabric index scale to interpret the amount of bioturbation in the field. Most of the geologic units in the study area are assigned to the Cruziana and Thalassinoides ichnofacies consistent with interpretations of a tidal-dominated open marine environment (sublittoral zone). Ichnofossil assemblages are dominated by Thalassinoides networks, but also contain Cruziana, Ophiomorpha, Paleo­phycus, Planolites, and Serpulid traces.

  18. Postglacial sedimentary processes on the Storfjorden and Kveithola trough mouth fans: Significance of extreme glacimarine sedimentation

    Science.gov (United States)

    Lucchi, R. G.; Camerlenghi, A.; Rebesco, M.; Colmenero-Hidalgo, E.; Sierro, F. J.; Sagnotti, L.; Urgeles, R.; Melis, R.; Morigi, C.; Bárcena, M.-A.; Giorgetti, G.; Villa, G.; Persico, D.; Flores, J.-A.; Rigual-Hernández, A. S.; Pedrosa, M. T.; Macri, P.; Caburlotto, A.

    2013-12-01

    The depositional history of the Storfjorden and Kveithola trough-mouth fans (TMFs) in the northwestern Barents Sea has been investigated within two coordinated Spanish and Italian projects in the framework of the International Polar Year (IPY) Activity 367, NICE STREAMS. The investigation has been conducted using a multidisciplinary approach to the study of sediment cores positioned on high-resolution multibeam bathymetry and TOPAS/CHIRP sub-bottom profiles. Core correlation and the age model were based on 27 AMS 14C samples, rock magnetic parameters, lithofacies sequences, and the presence of marker beds including two oxidized layers marking the post Last Glacial Maximum (LGM) inception of deglaciation (OX-2) and the Younger Dryas cold climatic event (OX-1). Sediment facies analysis allowed the distinction of a number of depositional processes whose onset appears closely related to ice stream dynamics and oceanographic patterns in response to climate change. The glacigenic diamicton with low water content, high density, and high shear strength, deposited during glacial maxima, indicates ice streams grounded at the shelf edge. Massive release of IRD occurred at the inception of deglaciation in response to increased calving rates with possible outer ice streams lift off and collapse. The presence of a several-meter-thick sequence of interlaminated sediments deposited by subglacial outbursts of turbid meltwater (plumites) indicates rapid ice streams' melting and retreat. Crudely-layered and heavily-bioturbated sediments were deposited by contour currents under climatic/environmental conditions favorable to bioproductivity. The extreme sedimentation rate of 3.4 cm a- 1 calculated for the plumites from the upper-slope area indicates a massive, nearly instantaneous (less than 150 years), terrigenous input corresponding to an outstanding meltwater event. We propose these interlaminated sediments to represent the high-latitude marine record of MeltWater Pulse 1a (MWP-1a

  19. Detrital thermochronology and sedimentology of the Sabine Bay and Assistance formations, Ellesmere Island: insights into the source of the Melvilian Disturbance event

    Science.gov (United States)

    Chau, Y.; Leier, A.; Guest, B.; Beauchamp, B.; Morris, N.

    2011-12-01

    The Melvillian Disturbance in the Sverdrup Basin of the Canadian Arctic occurred between early and middle Permian time and is characterized by angular unconfomities, basaltic flows, and is linked to a broader mid-Permian circum-Arctic tectonic event.We examined the lower-middle Permian Sabine Bay and Assistance formations exposed in northwestern Ellesmere Island in order to better understand the depositional and tectonic history of this region during the middle Permian time. Detailed sections of these units were measured at multiple locations and samples were collected for zircon/apatite thermochronology. The Sabine Bay Formation is present in limited locations where it consists of white, medium-grained, quartzose sediments. Beds contain trough cross-strata with drapes of mud-sized organic material, ripples, and rare bioturbation. Preliminary paleocurrent data indicate transport to the west. We interpret the Sabine Bay Formation to have been deposited in a fluvial environment, possibly with some tidal influence. The Assistance Formation unconformably overlies the Sabine Bay Formation and appears to be more regionally extensive than the Sabine Bay Formation. The Assistance Formation consists of fine-grained quartzose sandstone with abundant Zoophycos burrows, shell biota and other marine trace fossils. The character of the Assistance Formation varies between locations, but in some locations the formation contains hummocky and swaley cross-stratification bedding. Vertically, the Assistance Formation grades from sandstone beds into mudstone beds with deeper-water marine trace fossils. We interpret the Assistance Formation to have been deposited in a lower-shoreface, storm-influenced, shelf setting that was progressively transgressed during deposition. The isolated occurrences of the Sabine Bay Formation and large lateral thickness variations of the Assistance Formation suggest these units were deposited in fault-bounded sub-basins within the Sverdrup Basin. The larger

  20. Spatially limited mud turbidites on the Cascadia margin: segmented earthquake ruptures?

    Directory of Open Access Journals (Sweden)

    C. Goldfinger

    2013-08-01

    Full Text Available A series of 23 thin, mostly mud-silt turbidites are found interspersed between larger, well-dated and regionally correlated paleoseismic sandy turbidites that extend along most of the Cascadia margin, northwestern United States. Investigation of the structure, distribution, and sedimentology of these thin mud-silt units supports the interpretation of these units as turbidites originating on the continental slope. Interpretation of mud turbidites is inhibited by bioturbation and lower response to analytical and imaging techniques; nevertheless most of the 23 interpreted beds exhibit most of the characteristics of coarser turbidites. These characteristics include sharp bases, fining upward sequences, darker color, increased gamma and CT density and magnetic susceptibility relative to the hemipelagic background, sparse microfossils, high lithic content, and evidence of transport from marine sources on the continental slope. New core data from sites south of Rogue Apron indicate that sandy and muddy turbidites may be correlated at least 150 km south to Trinidad Plunge Pool for the period ~ 4800 yr BP to present. Many of the mud turbidites initially described at Rogue Apron coarsen southward, becoming sandy turbidites. High-resolution Chirp seismic profiles reveal that turbidite stratigraphy along the base of the southern Cascadia continental slope is continuous, with little variation for at least 240 km along strike. The Chirp data show that turbidites along the Cascadia base of slope are ubiquitous, and likely not sourced solely from submarine canyon mouths, but may also have been delivered to the proximal abyssal plain as sheet flows from the open continental slope and coalescing local sources. Regional stratigraphy reveals that hemipelagic sedimentation rates and total Holocene turbidite thickness and mass are similar at widely separated sites, yet the total thickness of the Holocene section is greater by a factor of two in southern Cascadia

  1. Hummocky cross-stratification-like structures and combined-flow ripples in the Punta Negra Formation (Lower-Middle Devonian, Argentine Precordillera): A turbiditic deep-water or storm-dominated prodelta inner-shelf system?

    Science.gov (United States)

    Basilici, Giorgio; de Luca, Pedro Henrique Vieira; Poiré, Daniel G.

    2012-08-01

    sandstone composition, and the relative scarcity of bioturbation, which was likely controlled by fresh-water input and a high rate of sedimentation. Storm-influenced, hyperpycnal flows generated subaqueous channelised forms at the mouth of the river deltas, which later filled with sand. At the distal end of the channelised forms, lobe-shaped sandstone beds were deposited, evolving distally into thin sandstone beds alternating with sandy mudstone.

  2. Generic reactive transport codes as flexible tools to integrate soil organic matter degradation models with water, transport and geochemistry in soils

    Science.gov (United States)

    Jacques, Diederik; Gérard, Fréderic; Mayer, Uli; Simunek, Jirka; Leterme, Bertrand

    2016-04-01

    and inorganic carbon in the aqueous and gaseous phases, as well as different decomposition functions with first-order, linear dependence or nonlinear dependence on a biomass pool. In addition, we show how processes such as local bioturbation (bio-diffusion) can be included implicitly through a Fickian formulation of transport of soil organic matter. Coupling soil organic matter models with generic and flexible reactive transport codes offers a valuable tool to enhance insights into coupled physico-chemical processes at different scales within the scope of C-biogeochemical cycles, possibly linked with other chemical elements such as plant nutrients and pollutants.

  3. Dynamic modelling of radionuclide uptake by Fukushima coastal biota - Dynamic modelling of radionuclide uptake by marine biota: application to Fukushima assessment

    Energy Technology Data Exchange (ETDEWEB)

    Vives i Batlle, Jordi [Belgian Nuclear Research Centre, Boeretang 200, 2400 Mol (Belgium)

    2014-07-01

    Radiological assessments to non-human marine biota are usually carried out by assuming that the activity concentration in an organism is proportional to the activity concentration in an adjacent volume of water, via a concentration factor (CF). It is also assumed that radionuclides in the water are in isotopic equilibrium with the sediments via a sediment distribution coefficient (K{sub d}). These assumptions are not valid in accidental situations where the biota and the sediments react with a time delay to large variations of activity concentration in seawater. A simple dynamic model was developed to factorise the dynamics of radionuclide uptake and turnover in biota and sediments, as determined by a balance between the residence time of radionuclides in seawater/sediments and the biological half-life of elimination in the biota. The model calculates activity concentration of {sup 131}I, {sup 134}Cs, {sup 137}Cs and {sup 90}Sr in seabed sediment, fish, crustaceans, molluscs and macro-algae from surrounding activity concentrations in seawater, with which to derive internal and external dose rates. A central element of this new model is the inclusion of sediment processes in dynamic transfer modelling. The model is adapted to include depletion of radionuclides adsorbed onto suspended particulates (particle scavenging), molecular diffusion, pore water mixing and bioturbation (modelled effectively as a diffusive process) represented by a simple set of differential equations that is coupled with the biological uptake/turnover processes. In this way, the model is capable of reproducing activity concentration in sediment to give a more realistic calculation of the external dose to biota compared with the simpler approach based on CF and K{sub d} values used in previous assessments. The model is applied to the assessment of the radiological impact of the Fukushima accident on marine biota in the early phase of the accident. It is shown that previous assessment of the

  4. Sedimentary facies and paleoenvironmental interpretation of a Holocene marsh in the Gironde Estuary in France

    Institute of Scientific and Technical Information of China (English)

    WANG Jianhua; MASSE Laurent; TASTET Jean-Pierre

    2006-01-01

    sedimentary facies show an obvious surficial and vertical banding distribution in which the texture and structure, authigenic mineral, foraminifera distribution and bioturbation indicate many distinct difference characteristics.

  5. A first attempt to reproduce basaltic soil chronosequences using a process-based soil profile model: implications for our understanding of soil evolution

    Science.gov (United States)

    Johnson, M.; Gloor, M.; Lloyd, J.

    2012-04-01

    model, followed by a description of novel methods using tracers such as optically stimulated luminescence (OSL) dates and meteoric 10Be to evaluate the modelled processes of bioturbation and surface erosion. We will also discuss comparisons of modelled properties with observations and conclude with implications on our understanding of soil evolution.

  6. Complex variations during a caldera-forming Plinian eruption, including precursor deposits, thick pumice fallout, co-ignimbrite breccias and climactic lag breccias: The 184 ka Lower Pumice 1 eruption sequence, Santorini, Greece

    Science.gov (United States)

    Simmons, J. M.; Cas, R. A. F.; Druitt, T. H.; Fol