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Sample records for bioturbation

  1. [Bioturbation of macrobenthos on estuarine sediment].

    Science.gov (United States)

    Qin, Xue-Bo; Sun, Hong-Wen; Wu, Ji-Zhou; Wang, Ruo-Nan; Sun, Tie-Heng

    2010-02-01

    By using microcosm tracer technique, the bioturbation of macrobenthos Helice tientsinensis, Nereis diversicolor, Bullacta exarata, and Cyclina sinensis on the sediment in Beitang Estuary of Tianjin, China was quantitatively studied. The bioturbation of test macrobenthos had obvious effects on the distribution of the sediment, and the effects differed with the macrobenthos. The disturbed intensity (diffusion coefficient, 10(-3) cm2 x d(-1)) of surface sediment under the effects of the macrobenthos was in order of N. diversicolor (2.95) > H. tientsinensis (1.00) > C. sinensis ( 0.78) > B. exarata. (0.35) > control (0.05), and that of deep sediment was H. tientsinensis (3.10) > N. diversicolor (2.33) > C. sinensis (0.28) > B. exarata (0.15) > control (0.05), which was mainly due to that the macrobenthos were belonged to different functional groups. There was a significant relationship between the bio-volume of test macrobentos and the diffusion coefficient of surface sediment (P < 0.05), suggesting that the bio-volume of macrobenthos could be used as an indicator to predict their bioturbation capacity on esturaine sediment. PMID:20462020

  2. Impact of oil on bacterial community structure in bioturbated sediments

    OpenAIRE

    Stauffert, Magali; Cravo-Laureau, Cristiana; Jezequel, Ronan; Barantal, Sandra; Cuny, Philippe; Gilbert, Franck; Cagnon, Christine; Militon, Cécile; Amouroux, David; Mahdaoui, Fatima; Bouyssiere, Brice; Stora, Georges; Merlin, François-Xavier; Duran, Robert

    2013-01-01

    Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In t...

  3. 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

  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. Remobilisation of uranium from contaminated freshwater sediments by bioturbation

    Science.gov (United States)

    Lagauzère, S.; Motelica-Heino, M.; Viollier, E.; Stora, G.; Bonzom, J. M.

    2014-06-01

    Benthic macro-invertebrate bioturbation can influence the remobilisation of uranium (U) initially associated with freshwater sediments, resulting in a high release of this pollutant through the overlying water column. Given the potential negative effects on aquatic biocenosis and the global ecological risk, it appears crucial to improve our current knowledge concerning the biogeochemical behaviour of U in sediments. The present study aimed to assess the biogeochemical modifications induced by Tubifex tubifex (Annelida, Clitellata, Tubificidae) bioturbation within the sediment in order to explain such a release of U. To reach this goal, U 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. "diffusive equilibrium in thin-films" DET gel probes for porewater, bioaccumulation in worms) of U and main chemical species (iron, sulfate, nitrate and nitrite), this work (i) confirmed that the removal of bottom sediment particles to the surface through the digestive tract of worms greatly favoured oxidative loss of U in the water column, and (ii) demonstrated that both U contamination and bioturbation of T. tubifex substantially influenced 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 U-contaminated sediments.

  7. 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

  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. 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

  10. Can benthic community structure be used to predict the process of bioturbation in real ecosystems?

    Science.gov (United States)

    Queirós, Ana M.; Stephens, Nicholas; Cook, Richard; Ravaglioli, Chiara; Nunes, Joana; Dashfield, Sarah; Harris, Carolyn; Tilstone, Gavin H.; Fishwick, James; Braeckman, Ulrike; Somerfield, Paul J.; Widdicombe, Stephen

    2015-09-01

    Disentangling the roles of environmental change and natural environmental variability on biologically mediated ecosystem processes is paramount to predict future marine ecosystem functioning. Bioturbation, the biogenic mixing of sediments, has a regulating role in marine biogeochemical processes. However, our understanding of bioturbation as a community level process and of its environmental drivers is still limited by loose use of terminology, and a lack of consensus about what bioturbation is. To help resolve these challenges, this empirical study investigated the links between four different attributes of bioturbation (bioturbation depth, activity and distance, and biodiffusive transport); the ability of an index of bioturbation (BPc) to predict each of them; and their relation to seasonality, in a shallow coastal system - the Western Channel Observatory, UK. Bioturbation distance depended on changes in benthic community structure, while the other three attributes were more directly influenced by seasonality in food availability. In parallel, BPc successfully predicted bioturbation distance but not the other attributes of bioturbation. This study therefore highlights that community bioturbation results from this combination of processes responding to environmental variability at different time-scales. However, community level measurements of bioturbation across environmental variability are still scarce, and BPc is calculated using commonly available data on benthic community structure and the functional classification of invertebrates. Therefore, BPc could be used to support the growth of landscape scale bioturbation research, but future uses of the index need to consider which bioturbation attributes the index actually predicts. As BPc predicts bioturbation distance, estimated here using a random-walk model applicable to community settings, studies using either of the metrics should be directly comparable and contribute to a more integrated future for

  11. 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.

  12. Remobilisation of uranium from contaminated freshwater sediments by bioturbation

    OpenAIRE

    Lagauzère, S.; M. Motelica-Heino; E. Viollier; Stora, G.; Bonzom, J.M.

    2014-01-01

    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 ass...

  13. Impact of oil on bacterial community structure in bioturbated sediments.

    Directory of Open Access Journals (Sweden)

    Magalie Stauffert

    Full Text Available Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In this study, an experimental laboratory device maintaining pristine collected mudflat sediments in microcosms closer to true environmental conditions--with tidal cycles and natural seawater--was used to simulate an oil spill under bioturbation conditions. Different conditions were applied to the microcosms including an addition of: standardized oil (Blend Arabian Light crude oil, 25.6 mg.g⁻¹ wet sediment, the common burrowing organism Hediste (Nereis diversicolor and both the oil and H. diversicolor. The addition of H. diversicolor and its associated bioturbation did not affect the removal of petroleum hydrocarbons. After 270 days, 60% of hydrocarbons had been removed in all microcosms irrespective of the H. diversicolor addition. However, 16S-rRNA gene and 16S-cDNA T-RFLP and RT-PCR-amplicon libraries analysis showed an effect of the condition on the bacterial community structure, composition, and dynamics, supported by PerMANOVA analysis. The 16S-cDNA libraries from microcosms where H. diversicolor was added (oiled and un-oiled showed a marked dominance of sequences related to Gammaproteobacteria. However, in the oiled-library sequences associated to Deltaproteobacteria and Bacteroidetes were also highly represented. The 16S-cDNA libraries from oiled-microcosms (with and without H. diversicolor addition revealed two distinct microbial communities characterized by different phylotypes associated to known hydrocarbonoclastic bacteria and dominated by

  14. Impact of oil on bacterial community structure in bioturbated sediments.

    Science.gov (United States)

    Stauffert, Magalie; Cravo-Laureau, Cristiana; Jézéquel, Ronan; Barantal, Sandra; Cuny, Philippe; Gilbert, Franck; Cagnon, Christine; Militon, Cécile; Amouroux, David; Mahdaoui, Fatima; Bouyssiere, Brice; Stora, Georges; Merlin, François-Xavier; Duran, Robert

    2013-01-01

    Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In this study, an experimental laboratory device maintaining pristine collected mudflat sediments in microcosms closer to true environmental conditions--with tidal cycles and natural seawater--was used to simulate an oil spill under bioturbation conditions. Different conditions were applied to the microcosms including an addition of: standardized oil (Blend Arabian Light crude oil, 25.6 mg.g⁻¹ wet sediment), the common burrowing organism Hediste (Nereis) diversicolor and both the oil and H. diversicolor. The addition of H. diversicolor and its associated bioturbation did not affect the removal of petroleum hydrocarbons. After 270 days, 60% of hydrocarbons had been removed in all microcosms irrespective of the H. diversicolor addition. However, 16S-rRNA gene and 16S-cDNA T-RFLP and RT-PCR-amplicon libraries analysis showed an effect of the condition on the bacterial community structure, composition, and dynamics, supported by PerMANOVA analysis. The 16S-cDNA libraries from microcosms where H. diversicolor was added (oiled and un-oiled) showed a marked dominance of sequences related to Gammaproteobacteria. However, in the oiled-library sequences associated to Deltaproteobacteria and Bacteroidetes were also highly represented. The 16S-cDNA libraries from oiled-microcosms (with and without H. diversicolor addition) revealed two distinct microbial communities characterized by different phylotypes associated to known hydrocarbonoclastic bacteria and dominated by Gammaproteobacteria

  15. 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

  16. 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

  17. 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....

  18. Imaging Oxygen Distribution in Marine Sediments. The Importance of Bioturbation and Sediment Heterogeneity

    OpenAIRE

    Pischedda, Laura; Poggiale, Jean-Christophe; Cuny, Philippe; Gilbert, Franck

    2008-01-01

    The influence of sediment oxygen heterogeneity, due to bioturbation, on diffusive oxygen flux was investigated. Laboratory experiments were carried out with 3 macrobenthic species presenting different bioturbation behaviour patterns:the polychaetes Nereis diversicolor and Nereis virens, both constructing ventilated galleries in the sediment column, and the gastropod Cyclope neritea, a burrowing species which does not build any structure. Oxygen two-dimensional distribution in sediments was qu...

  19. 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

  20. 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.

  1. 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

    Animal burrowing and sediment-mixing (bioturbation) began during the run up to the Ediacaran/Cambrian boundary(1-3), initiating a transition(4,5) between the stratified Precambrian(6) and more well-mixed Phanerozoic(7) sedimentary records, against the backdrop of a variable(8,9) global oxygen...... reservoir probably smaller in size than present(10,11). Phosphorus is the long-term(12) limiting nutrient for oxygen production via burial of organic carbon(13), and its retention (relative to carbon) within organic matter in marine sediments is enhanced by bioturbation(14-18). Here we explore the...

  2. 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; Andersen, Thorbjørn J.; Pejrup, Morten

    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...

  3. 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.

  4. Carbon storage in post-mining forest soil, the role of tree biomass and soil bioturbation

    Czech Academy of Sciences Publication Activity Database

    Frouz, Jan; Pižl, Václav; Cienciala, E.; Kalčík, Jiří

    2009-01-01

    Roč. 94, č. 2 (2009), s. 111-121. ISSN 0168-2563 R&D Projects: GA MŠk 2B08023; GA AV ČR 1QS600660505 Institutional research plan: CEZ:AV0Z60660521 Keywords : soil formation * bioturbation * carbon cycling Subject RIV: EH - Ecology, Behaviour Impact factor: 2.771, year: 2009

  5. Earthworm bioturbation influences the phytoavailability of metals released by particles in cultivated soils

    International Nuclear Information System (INIS)

    The influence of earthworm activity on soil-to-plant metal transfer was studied by carrying out six weeks mesocosms experiments with or without lettuce and/or earthworms in soil with a gradient of metal concentrations due to particles fallouts. Soil characteristics, metal concentrations in lettuce and earthworms were measured and soil porosity in the mesocosms was determined. Earthworms increased the soil pH, macroporosity and soil organic matter content due to the burying of wheat straw provided as food. Earthworm activities increased the metals concentrations in lettuce leaves. Pb and Cd concentrations in lettuce leaves can increase up to 46% with earthworm activities … These results and the low correlation between estimated by CaCl2 and EDTA and measured pollutant phytoavailability suggest that earthworm bioturbation was the main cause of the increase. Bioturbation could affect the proximity of pollutants to the roots and soil organic matter. - Highlights: • Earthworm bioturbation increases phytoavailability of Pb, Cd, Zn and Cu. • Earthworm activity influences soil structure and increases pH. • Plant metal uptake was not correlated with CaCl2, EDTA estimated phytoavailability. • Increased metal phytoavailability with bioturbation could increase human exposure. - Earthworm activities can increase metal phytoavailability and subsequent human exposure to metals in consumed vegetables

  6. 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

  7. 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

  8. 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.

  9. The influence of Cu contamination on Nereis diversicolor bioturbation

    OpenAIRE

    Fernandes, S.; Meysman, F.J.R.; Sobral, P.

    2006-01-01

    Aquatic sediments feature a two-way interaction between contaminants and benthic macrofauna. The effect of the macrofauna community on the transport of contaminants in sediment has received considerable attention. Yet, few studies have investigated the reverse effect, i.e., the influence of contaminants on bioturbation activity. To this end, we performed laboratory experiments to investigate the effect of copper contamination on sediment reworking activity of the ragworm Nereis diversicolor. ...

  10. 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.

  11. 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.

  12. Effects of benthic macrofauna bioturbation on the bacterial community composition in lake sediments.

    Science.gov (United States)

    Zeng, Jin; Zhao, Da-Yong; Liu, Peng; Yu, Zhong-Bo; Huang, Rui; Wu, Qinglong L

    2014-08-01

    Benthic macrofauna are considered to be an important part of the lacustrine ecosystem, and bioturbation may greatly affect the biogeochemical processes and microbial activities in sediments. In the present study, the bacterial community composition in sediments inhabited by 3 different types of benthic macrofauna (Corbicula fluminea, Chironomidae larvae, and tubificid worms) in the shallow and eutrophic Lake Taihu was studied to investigate the different effects of bioturbation on the composition of these communities. Microcosms were constructed, and culture-independent methods, including terminal restriction fragment length polymorphism (T-RFLP) and clone library analysis, were performed to evaluate the bacterial communities. Analysis of similarities (ANOSIM) and multidimensional scaling (MDS) analysis of T-RFLP patterns demonstrated that differences in the bacterial community composition between the control and the macrofauna-inhabited sediments were not as great as expected, although the chemical properties of the sediments changed remarkably. Nevertheless, the dominant bacterial group in each type of macrofauna-inhabited sediment was different. Acidobacteria, Betaproteobacteria, and Deltaproteobacteria were the dominant bacterial groups in sediments inhabited by C. fluminea, tubificid worms, and Chironomidae larvae, respectively. The data obtained in this study are helpful for understanding the effects of bioturbation in a shallow, eutrophic lake. PMID:25070418

  13. Bioturbation of surficial sediments on the continental slope, east of Newfoundland

    International Nuclear Information System (INIS)

    Data on regional sedimentary processes, in conjunction with measurements of Pb-210 activity distributions in short cores, facilitate the differentiation of local bioturbation regimes on the continental slope, east of Newfoundland, and provide insight into the factors controlling sediment mixing in these and comparable environments. Excess Pb-210 is confined to the upper 2 cm of sediments underlying the southerly-flowing, Western Boundary Undercurrent (WBU) at 2600 m indicating that minimal contemporary biological reworking of material has occurred at this location. This regime represents an inhospitable environment for the establishment of bioturbating communities because: (1) deposition of fine-grained, organic-rich material which serves as a food source for benthic infauna is inhibited by bottom currents which attain speeds of at least 20 cm s-1, and (2) the variable current regime produces an unstable bottom substrate in which smaller organisms (e.g. meiofauna) are frequently buried and their burrows are rapidly infilled. In contrast, the higher flux of fine-grained, organic-rich material to the middle slope (700 to 2000 m), and the more stable sedimentary conditions which prevail in this low energy regime, are conducive to active colonization of this substrate by bioturbating macrofauna. Maxima in Pb-210 activity profiles at depths of 7 cm to 11 cm in sediment cores are suggestive of heterogeneous, down-ward transport of surface material, possibly through infilling of macrofaunal burrows

  14. 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...

  15. Bioturbating shrimp alter the structure and diversity of bacterial communities in coastal marine sediments.

    Science.gov (United States)

    Laverock, Bonnie; Smith, Cindy J; Tait, Karen; Osborn, A Mark; Widdicombe, Steve; Gilbert, Jack A

    2010-12-01

    Bioturbation is a key process in coastal sediments, influencing microbially driven cycling of nutrients as well as the physical characteristics of the sediment. However, little is known about the distribution, diversity and function of the microbial communities that inhabit the burrows of infaunal macroorganisms. In this study, terminal-restriction fragment length polymorphism analysis was used to investigate variation in the structure of bacterial communities in sediment bioturbated by the burrowing shrimp Upogebia deltaura or Callianassa subterranea. Analyses of 229 sediment samples revealed significant differences between bacterial communities inhabiting shrimp burrows and those inhabiting ambient surface and subsurface sediments. Bacterial communities in burrows from both shrimp species were more similar to those in surface-ambient than subsurface-ambient sediment (R=0.258, P<0.001). The presence of shrimp was also associated with changes in bacterial community structure in surrounding surface sediment, when compared with sediments uninhabited by shrimp. Bacterial community structure varied with burrow depth, and also between individual burrows, suggesting that the shrimp's burrow construction, irrigation and maintenance behaviour affect the distribution of bacteria within shrimp burrows. Subsequent sequence analysis of bacterial 16S rRNA genes from surface sediments revealed differences in the relative abundance of bacterial taxa between shrimp-inhabited and uninhabited sediments; shrimp-inhabited sediment contained a higher proportion of proteobacterial sequences, including in particular a twofold increase in Gammaproteobacteria. Chao1 and ACE diversity estimates showed that taxon richness within surface bacterial communities in shrimp-inhabited sediment was at least threefold higher than that in uninhabited sediment. This study shows that bioturbation can result in significant structural and compositional changes in sediment bacterial communities, increasing

  16. Benzo(a)pyrene inhibits the role of the bioturbator Tubifex tubifex in river sediment biogeochemistry.

    Science.gov (United States)

    Mermillod-Blondin, F; Foulquier, A; Gilbert, F; Navel, S; Montuelle, B; Bellvert, F; Comte, G; Grossi, V; Fourel, F; Lecuyer, C; Simon, L

    2013-04-15

    The interactions between invertebrates and micro-organisms living in streambed sediments often play key roles in the regulation of nutrient and organic matter fluxes in aquatic ecosystems. However, benthic sediments also constitute a privileged compartment for the accumulation of persistent organic pollutants such as PAHs or PCBs that may affect the diversity, abundance and activity of benthic organisms. The objective of this study was to quantify the impact of sediment contamination with the PAH benzo(a)pyrene on the interaction between micro-organisms and the tubificid worm, Tubifex tubifex, which has been recognized as a major bioturbator in freshwater sediments. Sedimentary microcosms (slow filtration columns) contaminated or not with benzo(a)pyrene (3 tested concentrations: 0, 1 and 5 mg kg(-1)) at the sediment surface were incubated under laboratory conditions in the presence (100 individuals) or absence of T. tubifex. Although the surface sediment contaminations with 1 mg kg(-1) and 5 mg kg(-1) of benzo(a)pyrene did not affect tubificid worm survival, these contaminations significantly influenced the role played by T. tubifex in biogeochemical processes. Indeed, tubificid worms stimulated aerobic respiration, denitrification, dehydrogenase and hydrolytic activities of micro-organisms in uncontaminated sediments whereas such effects were inhibited in sediments polluted with benzo(a)pyrene. This inhibition was due to contaminant-induced changes in bioturbation (and especially bio-irrigation) activities of worms and their resulting effects on microbial processes. This study reveals the importance of sublethal concentrations of a contaminant on ecological processes in river sediments through affecting bioturbator-microbe interactions. Since they affect microbial processes involved in water purification processes, such impacts of sublethal concentrations of pollutants should be more often considered in ecosystem health assessment. PMID:23500821

  17. 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...... animals that directly or indirectly affect sediment matrices. These processes include both particle reworking and burrow ventilation. With this definition, bioturbation acts as an ‘umbrella’ term that covers all transport processes and their physical effects on the substratum. Particle reworking occurs...

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. Imaging oxygen distribution in marine sediments. The importance of bioturbation and sediment heterogeneity.

    Science.gov (United States)

    Pischedda, L; Poggiale, J C; Cuny, P; Gilbert, F

    2008-06-01

    The influence of sediment oxygen heterogeneity, due to bioturbation, on diffusive oxygen flux was investigated. Laboratory experiments were carried out with 3 macrobenthic species presenting different bioturbation behaviour patterns: the polychaetes Nereis diversicolor and Nereis virens, both constructing ventilated galleries in the sediment column, and the gastropod Cyclope neritea, a burrowing species which does not build any structure. Oxygen two-dimensional distribution in sediments was quantified by means of the optical planar optode technique. Diffusive oxygen fluxes (mean and integrated) and a variability index were calculated on the captured oxygen images. All species increased sediment oxygen heterogeneity compared to the controls without animals. This was particularly noticeable with the polychaetes because of the construction of more or less complex burrows. Integrated diffusive oxygen flux increased with oxygen heterogeneity due to the production of interface available for solute exchanges between overlying water and sediments. This work shows that sediment heterogeneity is an important feature of the control of oxygen exchanges at the sediment-water interface. PMID:18247133

  3. Conveyor belt biomantles: Centripetal bioturbation coupled with erosional downwasting -- an explanatory model

    Science.gov (United States)

    Johnson, D. L.; Johnson, D. N.

    2012-12-01

    Science advances on the strength of clarifying and unifying concepts, models, and methodologies that enhance and expand our explanatory paradigms. If valid, such structures allow us to accurately understand and appreciate how the world works. To aid in this task, new term-concepts must sometimes be coined and formalized. To understand certain ubiquitously occurring -- though as yet un-conceptualized -- surface processes that operate non-stop, and assessing their efficacies, is a desirable goal in landscape evolution studies. All near-surface processes are, of course, biological, chemical, and or physical in nature, and many if not most operate in combination. But of this triumvirate, biological processes, both biochemical and biomechanical (bioturbations), are perhaps least understood. Combinations of ubiquitously and semi-continuously occurring poorly understood processes that are both obscure and yet obvious have collectively produced Earth's biomantle. The biomantle occupies the uppermost Pedosphere, is a planet-wide layer, and unique to Earth. It thus functions as the biogenically habitable interface between the Atmosphere, Biosphere, Hydrosphere, and Lithosphere. The biomantle is defined as the organic-bearing bioturbated upper part of soil, including the topsoil, and of subaqueous substrates (lake, stream, ocean floor sediments) where most biota live, operate, move, wriggle, rest, sleep, estivate, seek food, eat, compete, fight, hide, reproduce, die, and assimilate. Its position and function in the uppermost soil layer of the Critical Zone must modulate and mediate much or most of what takes place above and below in ways yet to be established. In an attempt to increase understanding of this complicated biodynamic pedomembrane, and to identify the main processes that produce it, we present an iterative process model that pits ongoing cyclic bioturbation driven constructional processes against ongoing cyclic physically driven destructional processes. More

  4. 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

  5. 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

  6. The impact of sediment bioturbation by secondary organisms on metal bioavailability, bioaccumulation and toxicity to target organisms in benthic bioassays: Implications for sediment quality assessment.

    Science.gov (United States)

    Remaili, Timothy M; Simpson, Stuart L; Amato, Elvio D; Spadaro, David A; Jarolimek, Chad V; Jolley, Dianne F

    2016-01-01

    Bioturbation alters the properties of sediments and modifies contaminant bioavailability to benthic organisms. These naturally occurring disturbances are seldom considered during the assessment of sediment quality. We investigated how the presence (High bioturbation) and absence (Low bioturbation) of a strongly bioturbating amphipod within three different sediments influenced metal bioavailability, survival and bioaccumulation of metals to the bivalve Tellina deltoidalis. The concentrations of dissolved copper decreased and manganese increased with increased bioturbation. For copper a strong correlation was observed between increased bivalve survival (53-100%) and dissolved concentrations in the overlying water. Increased bioturbation intensity resulted in greater tissue concentrations for chromium and zinc in some test sediments. Overall, the results highlight the strong influence that the natural bioturbation activities from one organism may have on the risk contaminants pose to other organisms within the local environment. The characterisation of field-based exposure conditions concerning the biotic or abiotic resuspension of sediments and the rate of attenuation of released contaminants through dilution or readsorption may enable laboratory-based bioassay designs to be adapted to better match those of the assessed environment. PMID:26589100

  7. 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

  8. 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...

  9. Geostatistical modeling and upscaling permeability for reservoir scale modeling in bioturbated, heterogeneous tight reservoir rock: Viking Fm, Provost Field, Alberta

    OpenAIRE

    Hsieh, Amy I-Ju

    2015-01-01

    While burrow-affected permeability must be considered for characterizing reservoir flow, the marked variability generated at the bed/bedset scale makes bioturbated media difficult to model. Study of 28 cored wells of the Lower Cretaceous Viking Formation in the Provost Field, Alberta, Canada integrated sedimentologic and ichnologic features to define recurring hydrofacies possessing distinct permeability grades. Transition probability analysis was employed to model spatial variations in bioge...

  10. 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 ...

  11. 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

  12. 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.

  13. Effects of bioturbation on the fate of oil in coastal sandy sediments--an in situ experiment.

    Science.gov (United States)

    Timmermann, Karen; Banta, Gary T; Klinge, Lars; Andersen, Ole

    2011-03-01

    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 enhanced oil persistence. Conversely, A. marina stimulated both the physical removal and microbial degradation of oil compounds in uniformly oil contaminated sediments especially in deeper sediment layers (10-20 cm below the surface), whereas the fate of oil compounds deposited in surface layers (0-5 cm) mainly was affected by removal processes induced by wave actions and other bioturbating infauna such as Nereis diversicolor, Corophium volutator and Hydrobia spp. present in the experimental plots. PMID:21186046

  14. 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.

  15. 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.

  16. 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.

  17. 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)

  18. 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;

    of NH4+ from the sediment to the water phase (Tátrai 1986; Andersen et al. 2006), increase the uptake of oxygen and NO3- in the sediment (Andersen & Jensen, 1991), reduce P release or enhance P uptake (Andersen & Jensen 1991; Lewandowski & Hupfer 2005), or sometimes release P from the sediment......Many shallow lakes are affected by high internal nutrient loading and several techniques of lake restoration are being applied for the purpose of stabilizing a clear water state in the lakes. One such method is addition of Al [Al2(SO4)3 or AlCl3] to the lake for binding P in the sediment. Such...... treatment was conducted in Lake Nordborg (DK, 55 ha, depth: mean 5.0 m, max 8.5 m) in October 2006. In parts of the lake a visible layer of Al is now seen in the sediment whereas other parts of the lake received very little Al. Benthic macroinvertebrates in the sediment (bioturbation) increase the release...

  19. Establishing the Temporal Resolution of High-Latitude Paleoclimatic and Paleomagnetic Signals in Bioturbated Gulf of Alaska Continental Margin Sediments

    Science.gov (United States)

    Rosen, G. P.; Jaeger, J. M.; Stoner, J. S.; Channell, J. E.

    2005-12-01

    Under the right depositional conditions, continental margin strata may preserve valuable records of climatic, tectonic and geochemical changes in the adjacent landscapes. Whereas anoxic basins containing laminated strata are a preferred depositional environment for paleoclimate records, they are geographically limited, thus diminishing their usefulness at examining global landscape changes. Bioturbated margin strata are far more ubiquitous, but under slow sediment accumulation, proxies of decadal-scale climate changes, which may have a large impact on landscape modification, may not be preserved. Additionally, paleosecular variations (PSV) and relative paleointensity of natural remanent magnetization (NRM) in sediments are increasingly being used as global chronometers, but little field data exists from continental margins to examine the use of these tools in rapidly bioturbated strata common to this setting. When utilizing marine sedimentary proxies and strata to interpret paleoclimatic and paleomagnetic signals, respectively, it is necessary to consider the temporal resolution and fidelity of those signals and the conditions under which they are emplaced and preserved. Specifically, to what degree is bioturbation degrading or time-integrating the signal? The degree of degradation is proposed to vary with the transit time (TT) through the biologically mixed surface layer (TT= layer thickness/sediment accumulation rate) and the intensity of bioturbation in this layer, as represented by the biodiffusivity coefficient, Db, which has been shown to be highly variable (10~100 cm2/yr) on continental margins. Theoretically, weakly mixed strata undergoing rapid accumulation provide the best signal preservation. To quantify preservation potential, samples were collected along the Gulf of Alaska (GoA) margin aboard the R/V Maurice Ewing in 2004 (EW0408). Coring locations included fjord, shelf and fan sites and spanned a range of depositional environments from glacimarine to

  20. Lattice-automaton bioturbation simulator (LABS): implementation for small deposit feeders

    Science.gov (United States)

    Choi, Jae; Francois-Carcaillet, Fréderique; Boudreau, Bernard P.

    2002-02-01

    A new model for biological activity and its effects in sediments is presented. Sediment is represented as a random 2D collection of solid and water "particles", distributed on a regular lattice with individually assigned chemical, biological and physical properties, e.g. food versus inert material. Model benthic organisms move through the lattice (the virtual sediment) as programmable entities, i.e., automatons, by displacing or ingesting-defecating particles. Each type of automaton obeys a different set of rules, both deterministic and stochastic, designed to mimic real infauna. In the present version of the model code, the organisms are simple small deposit feeders, resembling capitellids. The results from the model are 2D visualizations of the movement of the animals and the particles with time. The latter provide immediate appreciation of the consequences of animal actions on sediment fabric and composition, including both the mixing, traditionally associated with bioturbation, and the development of biologically-induced heterogeneities, which are observed in real sediments. The output is readily amenable to presentation as computer-generated (QuickTime TM) movies, for which links are provided to such examples. As a particular case, we present a simulation of the mixing of a sand plug in a muddy sediment which shows that this is process not accomplished by counter-diffusion of sand and mud but by displacement and dilution of the sand with mud that is defecated as feces therein; this mode of mixing appears to be far more favorable to preservation of this sand feature than traditional diffusive models.

  1. 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.

  2. Effects of uranium-contaminated sediments on the bioturbation activity of Chironomus riparius larvae (Insecta, Diptera) and Tubifex tubifex worms (Annelida, Tubificidae).

    Science.gov (United States)

    Lagauzère, S; Boyer, P; Stora, G; Bonzom, J-M

    2009-07-01

    Freshwater sediments represent a compartment for accumulation of toxic substances, notably of metallic pollutants such as uranium. However, they also constitute a privileged habitat for many benthic macro-invertebrate species with important roles in the functioning of these ecosystems, particularly through their bioturbation activities. Uranium accumulation in sediments can thus have harmful effects on these organisms (e.g., developmental delay, malformations, mortality). The present study aimed to evaluate the consequences of these effects on the bioturbation activity of Chironomus riparius larvae and Tubifex tubifex worms. These two species, which are widespread in freshwater ecosystems, are characteristic of two different modes of bioturbation: bioirrigation and upward bioconveying, respectively. By quantifying the burial and redistribution of fluorescent particulate tracers (microspheres), sediment reworking induced by these macro-invertebrates was measured after 12d of exposure. Biodiffusion D(b) and bioadvection W rates, as well as several other parameters, were estimated to assess and compare the bioturbation activity of the two species, separately and in combination, between uncontaminated and uranium-spiked sediments. The results reveal that C. riparius larvae were more sensitive to uranium, but their bioturbation activity, even under uncontaminated conditions, had little effect on sediment reworking. Particle mixing was mainly induced by T. tubifex worms, which were only affected by uranium at high concentrations in the sediment. Finally, bioturbation by T. tubifex led to a high degree of uranium release from sediment to the overlying water, which highlights the crucial role of this mostly dominant species on uranium biogeochemical cycles at concentrations existing in naturally contaminated sites. PMID:19403158

  3. 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.

  4. Assessing bioturbation using micromorphology and biosilicate evidence: A case study of the early-Holocene Brady Soil, central Great Plains, USA

    Science.gov (United States)

    Woodburn, T. L.; Hasiotis, S. T.; Johnson, W. C.

    2012-12-01

    The Old Wauneta Roadcut site in southwestern Nebraska exhibits a 1.2 meter-thick exposure of the Brady Soil, a buried paleosol which formed within loess during the Pleistocene-Holocene transition. Excavation of the loess-paleosol sequence has revealed considerable bioturbation by plant roots, invertebrates, and small vertebrates. Bioturbation was not restricted to a single time period, but occurred continually throughout soil development, as evidenced by differing sediment fills and crosscutting relationships. The Brady Soil is an accretionary soil within the uppermost part of the Last Glacial Maximum Peoria Loess. At the base of the solum, the Bkb horizon exhibits an increased illuvial clay and carbonate content, and contains extensive, small (~2cm width), backfilled burrows typically produced by cicada nymphs (Cicadidae) or beetle larvae. The most stable period of the Brady Soil is expressed by the dark (9.8 YR 4/1), thick Ab horizon. This is overlain by an ACb horizon, where soil formation was being extinguished by the onset of Holocene-age Bignell Loess deposition. Within the upper solum and Bignell Loess, a shift in biota activity occurs as indicated by the large burrow (6-12 cm width) and chamber (30-40 cm width) systems observed. Trace sizes suggest that a burrowing rodent, such as the prairie dog (Cynomys sp.) or ground squirrel (Spermophilus sp.), was responsible for their creation. Soil micromorphology was used to distinguish sediment-size classes, mineralogy, and clay morphology of specific loess deposits and soil horizons in order to track displacement of sediment through the profile due to bioturbation. Five block samples were taken in undisturbed sediment and soil horizons for thin-section analysis. Twelve additional samples of burrow cross-sections or bioturbated sediment were analyzed for comparison. Soil features produced by faunal and floral activity were differentiated from features produced by pedologic processes through the identification and

  5. Influence of bioturbation by the amphipod Corophium volutator on fluoranthene uptake in the marine polychaete Nereis virens

    Energy Technology Data Exchange (ETDEWEB)

    Ciarelli, S.; Kater, B.J.; Straalen, N.M. van

    2000-06-01

    The uptake kinetics of fluoranthene in the polychaete worm Nereis virens were investigated in the presence and in the absence of amphipods to examine the effects of sediment bioturbation by the benthic amphipod Corophium volutator on the uptake in worms. Worms only and worms together with two different densities of amphipods were exposed to fluoranthene-spiked sediment for 12 d. Worms and overlying water samples for fluoranthene analyses were taken and total suspended solids in water column were measured after 1, 2, 5, 8, and 12 d. Results showed that in all treatments fluoranthene was rapidly accumulated by N. virens during the first two days and a steady state was reached within five days of exposure. Biota to sediment accumulation factors normalized to lipid concentration and to sediment organic carbon (BAF{sub ioc}) or worms exposed with the highest number of amphipods were significantly higher (two to three times) compared to worms exposed with fewer or without amphipods after one and two days of exposure. Bioconcentration factors (BCFs), calculated as the ratio between the uptake (k{sub 1}) and elimination (k{sub 2}) rate constants were not significantly different among treatments. When BCFs were calculated on the basis of dissolved fluoranthene concentrations (BCF{sub diss}), values of the treatments where worms were exposed with 100 and 300 amphipods were slightly higher than those calculated on the basis of total (dissolved + particle-bound) aqueous fluoranthene (BCF{sub tot}). However, the presence of fluoranthene bound to dissolved organic matter could have accounted for lower than expected BCF{sub diss} values. The results suggest that bioturbation by amphiopoc, affected the concentration of fluoranthene in the worms not by changing the worm to water partitioning (k{sub 1}/k{sub 2}) but by changing the worm to sediment partitioning (BAF{sub ioc}). In the treatments with worms a higher mortality of amphipods was found compared to those without worms. The

  6. Long-term distribution of Cs-137 in freshwater ecosystem and the effect of bioturbation on leakage of Cs-137 from the sediments

    International Nuclear Information System (INIS)

    The first aim of the project was to make a literature compilation regarding Cs-137 in freshwater systems. Secondly, in order to follow up the long-term behaviour of Cs-137 in Lake Hillesjoen, sediment and water was sampled with respect to Cs-137. Finally, an experiment was done with chironomids, with the aim to assess the impact of bioturbation on the leakage of Cs-137 from the sediment, since this is one of the factors contributing to the uncertainties in radioecological models. Some aspects of long-term distribution of Cs-137 in freshwater lakes is discussed. In lake Hillesjoen the pool of Cs-137 in sediments (225 kBq/m2, 1993) has gradually increased since the Chernobyl accident, and now exceeds the initial deposition (100 kBq/m2). The effect of bioturbation on the leakage from the sediment to the water could not be clarified in this experiment, but is discussed. 40 refs

  7. 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.

  8. Influence of benthic macro-invertebrate bioturbation on the biogeochemical behaviour of uranium within freshwater sediments; Influence de la bioturbation des macro-invertebres benthiques sur le comportement biogeochimique de l'uranium au sein des sediments d'eau douce

    Energy Technology Data Exchange (ETDEWEB)

    Lagauzere, S.

    2008-06-15

    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

  9. 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

  10. 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

  11. 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

  12. Cadmium sulfide nanoparticles trigger DNA alterations and modify the bioturbation activity of tubificidae worms exposed through the sediment.

    Science.gov (United States)

    Dedeh, Amina; Ciutat, Aurélie; Lecroart, Pascal; Treguer-Delapierre, Mona; Bourdineaud, Jean-Paul

    2016-04-01

    To address the impact of cadmium sulfide nanoparticles (CdS NPs) in freshwater ecosystems, aquatic oligochaete Tubifex tubifex were exposed through the sediment to a low dose (0.52 mg of 8 nm in size of CdS NPs/kg) for 20 days using microcosms. Cadmium (Cd) was released from the CdS NPs-contaminated sediment to the water column, and during this period the average concentrations of Cd in the filtered water fraction were 0.026 ± 0.006 µg/L in presence of oligochaetes. Similar experiments with microparticular CdS and cadmium chloride (CdCl2) were simultaneously performed for comparative purposes. CdS NPs exposure triggered various effects on Tubifex worms compared to control, microsized and ionic reference, including modification of genome composition as assessed using RAPD-PCR genotoxicity tests. Bioaccumulation levels showed that CdS NPs were less bioavailable than CdCl2 to oligochaetes and reached 0.08 ± 0.01 µg Cd/g for CdS NPs exposure versus 0.76 ± 0.3 µg Cd/g for CdCl2 exposure (fresh weight). CdS NPs altered worm's behavior by decreasing significantly the bioturbation activity as assessed after the exposure period using conservative fluorescent particulate tracers. This study demonstrated the high potential harm of the CdS nanoparticular form despite its lower bioavailability for Tubifex worms. PMID:26618487

  13. Quantification by image analysis on thin sections of lessivage and bioturbation rates in soils in response to land use change and recycling of organic residues

    Science.gov (United States)

    Sauzet, Ophélie; Montagne, David; Cammas, Cécilia; Gilliot, Jean Marc

    2014-05-01

    Land agricultural management has strongly influenced soil evolution during the so-called anthropocene and agricultural practices have to be now assessed according to their influence on soil processes. However, there is a lack of quantitative data about agricultural effect on soil processes and their dynamics especially at generational time scale (10-100 years). Lessivage (i.e. clay translocation) and bioturbation by burrowing animals (mesofauna and macrofauna) are two major pedologic processes in temperate climate. They are of crucial importance as they imply the clay size fraction. This study aims at characterizing the dynamics of these processes and quantifying their intensity after (i) a change in land use and (ii) the introduction of a widespread agricultural practice i.e. organic amendments spreading. In our investigation, we built an anthropo-chrono-sequence of three Luvisols located on a plateau in Feucherolles (Yvelines, France). The first one is under a deciduous forest and the second one is under conventional agricultural management both with no change in land-use for the past two centuries. The last one is a cultivated Luvisol with regular manure spreading since 1998. Undisturbed soil samples were collected in each horizon of the three Luvisols and large thin sections (57 cm2) prepared according to the method of Guilloré (1985). Clay illuviation features and macropores of biological origin (>100 µm) were quantified by image analysis on the thin sections to evaluate the intensity of lessivage and bioturbation respectively. Size and shape of the macroporosity were used to quantify the activity of mesofauna and of endogeic and anecic worms. In case of cultivation, we can note a global increase of macroporosity and clay coatings abundance. The greater macroporosity observed on cultivated profiles was undoubtedly due to endogeic and anecic worm activities. Moreover, whereas macroporosity is preferentially located on soil surface under forest, it is better

  14. Integrating the impact of bioturbation to landscape-scale modeling of soil carbon dynamics: a case study of chernozems in Central Saskatchewan

    Science.gov (United States)

    Viaud, V.; Pennock, D.

    2010-12-01

    Plant-soil interactions and the addition of organic matter from grass have long been the only processes identified to explain soil organic carbon (SOC) distribution and the origin of the A-horizon of chernozemic soils (Dokutchaiev, 1967). But recent studies have suggested that the role of burrowing animals in soil mixing and its consequences on SOC distribution in chernozemic soils have been underestimated (Wilkinson et al., 2009). This work aims at modelling the spatio-temporal evolution of SOC stocks across a catena in a hummocky landscape of Central Saskatchewan. The catena was represented as a 2-dimensional system, divided into 1-m cells in the lateral dimension, and into 6 increments in the vertical dimension (0-to-10, 10-to-20, 20-to-30, 30-to-60, 60-to-90, and 90-to-120 cm). The carbon module of the CENTURY model was used to simulate SOC dynamics in each soil horizon, and the effect of bioturbation on soil vertical mixing in the top soil layers was explicitly modeled. The model also included a simulation of the water budget and water fluxes in soils that partly control SOC dynamics across a catena. The study was based on a detailed dataset from St Denis Wildlife Area (SK, Canada), including climate data, above- and belowground biomass measurements, soil survey, topography, and quantitative data on soil properties and C input in several landscape locations. The model was run over 10000 years. Precipitation and temperature were simulated stochastically. Simulation results, with and without bioturbation, were compared to the current values of SOC stocks.

  15. 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...

  16. 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

  17. Modelling the reworking effects of bioturbation on the incorporation of radionuclides into the sediment column: implications for the fate of particle-reactive radionuclides in Irish Sea sediments.

    Science.gov (United States)

    Cournane, S; León Vintró, L; Mitchell, P I

    2010-11-01

    A microcosm laboratory experiment was conducted to determine the impact of biological reworking by the ragworm Nereis diversicolor on the redistribution of particle-bound radionuclides deposited at the sediment-water interface. Over the course of the 40-day experiment, as much as 35% of a (137)Cs-labelled particulate tracer deposited on the sediment surface was redistributed to depths of up to 11 cm by the polychaete. Three different reworking models were employed to model the profiles and quantify the biodiffusion and biotransport coefficients: a gallery-diffuser model, a continuous sub-surface egestion model and a biodiffusion model. Although the biodiffusion coefficients obtained for each model were quite similar, the continuous sub-surface egestion model provided the best fit to the data. The average biodiffusion coefficient, at 1.8 +/- 0.9 cm(2) y(-1), is in good agreement with the values quoted by other workers on the bioturbation effects of this polychaete species. The corresponding value for the biotransport coefficient was found to be 0.9 +/- 0.4 cm y(-1). The effects of non-local mixing were incorporated in a model to describe the temporal evolution of measured (99)Tc and (60)Co radionuclide sediment profiles in the eastern Irish Sea, influenced by radioactive waste discharged from the Sellafield reprocessing plant. Reworking conditions in the sediment column were simulated by considering an upper mixed layer, an exponentially decreasing diffusion coefficient, and appropriate biotransport coefficients to account for non-local mixing. The diffusion coefficients calculated from the (99)Tc and (60)Co cores were in the range 2-14 cm(2) y(-1), which are consistent with the values found by other workers in the same marine area, while the biotransport coefficients were similar to those obtained for a variety of macrobenthic organisms in controlled laboratories and field studies. PMID:20732733

  18. Bioturbation et biogéochimie des sédiments marins côtiers : cycle de l’azote et devenir de la matière organique

    OpenAIRE

    Gilbert, Franck

    2003-01-01

    La bioturbation est un phénomène ubiquiste présent dans tous les écosystèmes terrestres et aquatiques. Dans les fonds marins, l’activité de la faune benthique va intervenir sur les caractéristiques physiques, chimiques et biologiques des sédiments et jouer de ce fait un rôle majeur dans le fonctionnement de la couche limite benthique. En particulier, les mouvements de particules et de solutés au sein de la colonne sédimentaire provoqués par les organismes et la présence de galeries vont gouve...

  19. Modelling the reworking effects of bioturbation on the incorporation of radionuclides into the sediment column: implications for the fate of particle-reactive radionuclides in Irish Sea sediments

    International Nuclear Information System (INIS)

    A microcosm laboratory experiment was conducted to determine the impact of biological reworking by the ragworm Nereis diversicolor on the redistribution of particle-bound radionuclides deposited at the sediment-water interface. Over the course of the 40-day experiment, as much as 35% of a 137Cs-labelled particulate tracer deposited on the sediment surface was redistributed to depths of up to 11 cm by the polychaete. Three different reworking models were employed to model the profiles and quantify the biodiffusion and biotransport coefficients: a gallery-diffuser model, a continuous sub-surface egestion model and a biodiffusion model. Although the biodiffusion coefficients obtained for each model were quite similar, the continuous sub-surface egestion model provided the best fit to the data. The average biodiffusion coefficient, at 1.8 ± 0.9 cm2 y-1, is in good agreement with the values quoted by other workers on the bioturbation effects of this polychaete species. The corresponding value for the biotransport coefficient was found to be 0.9 ± 0.4 cm y-1. The effects of non-local mixing were incorporated in a model to describe the temporal evolution of measured 99Tc and 60Co radionuclide sediment profiles in the eastern Irish Sea, influenced by radioactive waste discharged from the Sellafield reprocessing plant. Reworking conditions in the sediment column were simulated by considering an upper mixed layer, an exponentially decreasing diffusion coefficient, and appropriate biotransport coefficients to account for non-local mixing. The diffusion coefficients calculated from the 99Tc and 60Co cores were in the range 2-14 cm2 y-1, which are consistent with the values found by other workers in the same marine area, while the biotransport coefficients were similar to those obtained for a variety of macrobenthic organisms in controlled laboratories and field studies. -- Research highlights: →N. diversicolor redistributes up to 35% particle-bound radionuclide over 40

  20. Modelling the reworking effects of bioturbation on the incorporation of radionuclides into the sediment column: implications for the fate of particle-reactive radionuclides in Irish Sea sediments

    Energy Technology Data Exchange (ETDEWEB)

    Cournane, S., E-mail: sean.cournane@gmail.co [UCD School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Leon Vintro, L.; Mitchell, P.I. [UCD School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)

    2010-11-15

    A microcosm laboratory experiment was conducted to determine the impact of biological reworking by the ragworm Nereis diversicolor on the redistribution of particle-bound radionuclides deposited at the sediment-water interface. Over the course of the 40-day experiment, as much as 35% of a {sup 137}Cs-labelled particulate tracer deposited on the sediment surface was redistributed to depths of up to 11 cm by the polychaete. Three different reworking models were employed to model the profiles and quantify the biodiffusion and biotransport coefficients: a gallery-diffuser model, a continuous sub-surface egestion model and a biodiffusion model. Although the biodiffusion coefficients obtained for each model were quite similar, the continuous sub-surface egestion model provided the best fit to the data. The average biodiffusion coefficient, at 1.8 {+-} 0.9 cm{sup 2} y{sup -1}, is in good agreement with the values quoted by other workers on the bioturbation effects of this polychaete species. The corresponding value for the biotransport coefficient was found to be 0.9 {+-} 0.4 cm y{sup -1}. The effects of non-local mixing were incorporated in a model to describe the temporal evolution of measured {sup 99}Tc and {sup 60}Co radionuclide sediment profiles in the eastern Irish Sea, influenced by radioactive waste discharged from the Sellafield reprocessing plant. Reworking conditions in the sediment column were simulated by considering an upper mixed layer, an exponentially decreasing diffusion coefficient, and appropriate biotransport coefficients to account for non-local mixing. The diffusion coefficients calculated from the {sup 99}Tc and {sup 60}Co cores were in the range 2-14 cm{sup 2} y{sup -1}, which are consistent with the values found by other workers in the same marine area, while the biotransport coefficients were similar to those obtained for a variety of macrobenthic organisms in controlled laboratories and field studies. -- Research highlights: {yields

  1. 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)

  2. Influence de la Bioturbation sur l'Activité Dénitrifiante dans des Sédiments Marins Côtiers. Effet d'un Apport Exogène de Matière Organique: les Hydrocarbures

    OpenAIRE

    Gilbert, Franck

    1994-01-01

    L'objectif principal de ce travail était de mettre en évidence l'influence de la bioturbation induite par le macrobenthos sur la dénitrification dans un sédiment marin soumis à un apport ponctuel massif de matière organique (hydrocarbures). Deux types d'expérimentations complémentaires ont été réalisées: - In vitro, pour étudier les effets d'une population de Polychètes galéricoles Nereis diversicolor, - In situ (golfe de Fos) afin de mettre en évidence l'influence de la macrofaune autochtone...

  3. 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...

  4. 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

  5. Assessment of metal lability in freshwater sediments by passive sampling method in response to bioturbation

    OpenAIRE

    Dabrin, A.; Etienne, R.; Ferrari, B.J.D.; Coquery, M.

    2013-01-01

    The bioavailability of trace metals in sediments is function of many factors such as the targeted metal, its colloidal, dissolved and particulate partition, sediment physico-chemical characteristics or Acid Volatile Sulphide (AVS) contents. Moreover, organisms activity in sediments induce both a modification of redox conditions disturbing particulate and dissolved partition and an increase of metal diffusion at the sediment interface. It was shown that passive samplers such as Diffusive Gradi...

  6. Redistribution of fallout radionuclides in Enewetak Atoll lagoon sediments by callianassid bioturbation

    International Nuclear Information System (INIS)

    The lagoon sediments of Enewetak Atoll in the Marshall Islands contain a large selection of fallout radionuclides as a result of 43 nuclear weapon tests conducted there between 1948 and 1958. The authors report elevated fallout radionuclide concentrations buried more deeply in the lagoon sediments and evidence of burrowing into the sediment by several species of callianassid ghost shrimp (Crustacea: Thalassinidea) which has displaced highly radioactive sediment. The burrowing activities of callianassids, which are ubiquitous on the lagoon floor, facilitate radionuclide redistribution and complicate the fallout radionuclide inventory of the lagoon. (author)

  7. 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.

  8. 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

  9. Bioturbation of sediments by benthic macroinvertebrates and fish and its implication for pond ecosystems: a review

    Czech Academy of Sciences Publication Activity Database

    Adámek, Z.; Maršálek, Blahoslav

    2013-01-01

    Roč. 21, č. 1 (2013), s. 1-17. ISSN 0967-6120 R&D Projects: GA MPO FR-TI3/196 Institutional research plan: CEZ:AV0Z60050516 Institutional support: RVO:67985939 Keywords : benthic macroinverttebrates * benthivorous fish * bottom- water interface * nutrient cycling * pond management Subject RIV: EF - Botanics Impact factor: 0.960, year: 2013

  10. 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; Kristensen, Erik

    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 of...

  11. Benzo(a)pyrene inhibits the role of the bioturbator Tubifex tubifex in river sediment biogeochemistry

    OpenAIRE

    Mermillod-Blondin, Florian; Foulquier, Arnaud; Gilbert, Franck; Navel, Simon; Montuelle, Bernard; Bellvert, Floriant; Comte, Gilles; Grossi, Vincent; Fourel, François; Lecuyer, Christophe; Simon, Laurent

    2013-01-01

    The interactions between invertebrates and micro-organisms living in streambed sediments often play key roles in the regulation of nutrient and organic matter fluxes in aquatic ecosystems. However, benthic sedi- ments also constitute a privileged compartment for the accumulation of persistent organic pollutants such as PAHs or PCBs that may affect the diversity, abundance and activity of benthic organisms. The objective of this study was to quantify the impact of sediment contamination with t...

  12. CONTAMINANT FLUXES FROM SEDIMENT DUE TO TUBIFEX BIOTURBATION. (R825513C011)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  13. Sedimentary context controls the influence of ecosystem engineering by bioturbators on microbial processes in river sediments

    OpenAIRE

    Navel, Simon; Mermillod-Blondin, Florian; Montuelle, Bernard; Chauvet, Eric; Marmonier, Pierre

    2012-01-01

    By modifying the physical environment, ecosystem engineers can have inordinately large effects on surrounding communi- ties and ecosystem functioning. However, the significance of engineering in ecosystems greatly depends on the physical characteristics of the engineered habitats. Mechanisms underlying such context-dependent impact of engineers remain poorly understood even though they are crucial to establish general predictions concerning the contribution of engineers to ecosystem structure...

  14. Preliminary Data on the Bioturbation Activity of Hediste Diversicolor (Polychaeta, Nereididae) from the Loire Estuary, France

    OpenAIRE

    Gillet, Patrick; Mouloud, Mohammed; Mouneyrac, Catherine; Simo, Pablo; Gilbert, Franck

    2012-01-01

    The ragworm Hediste diversicolor (O. F. Müller, 1776) plays a key role in the estuarine water-sediment interface. This scientific project comes under the framework of the International network Nereis Park Experiment gathering 27 laboratories from all over the world. The experiments were carried out concurrently in spring 2007 using a common protocol. In the Loire estuary, the samples were collected in the intertidal zone of the Saint-Nazaire Bridge. During the field experiment, we estimated t...

  15. Functional PCA of measures for investigating the influence of bioturbation on sediment structure

    OpenAIRE

    Manté, Claude; Stora, Georges

    2012-01-01

    After describing the main characteristics of grain-size curves, we recall previous results about Principal Components Analysis of absolutely continuous measures, in connection with grain-size curves analysis. This method simultaneously takes into account a chosen reference probability (r.p.) μ (associated with a Radon-Nikodym derivation operator), and the imposed sampling mesh Tp. The point is that it amounts to usual PCA in some metrics M− (Tp; μ); consequently, analyzing a set of grain-size...

  16. Study of the influence of bioturbation on covers and contaminated materials on radon shielding using the lead tracing method; Untersuchung des Einflusses der Bioturbation von Abdeckungen und kontaminierten Materialien auf Radondaemmwirkung mittels Bleispurmethode

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, H.; Funke, L.; Schellenberger, A. [IAF-Radiooekologie GmbH, Dresden (Germany); Loebner, W.; Leichsenring, B.; Regner, J. [Wismuth GmbH, Chemnitz (Germany)

    2004-07-01

    For geological reasons, mining activities in Thuringia and Saxony have almost always been associated with the excavation of radioactive rock material. The legacy left behind by mining operations, such as waste heaps, industrial settling ponds, abandoned industrial areas and underground mines have posed and for some part still pose a considerable pollution burden for the environment and the population. At the present state of the art in science and technology the best possible remediation solution for these mining leftovers is to retain them in situ by means of a sealing cover(and where necessary provide seepage water retention and treatment). The purpose of such measures is to ensure that the environmental hazards emanating from abandoned mining sites are durably reduced to a tolerable level and the areas concerned can be converted for suitable subsequent uses in a manner adapted to the site in question and with relatively little aftercare required. The sealing systems to be designed and manufactured for this purpose must meet high requirements in terms of long-term effectiveness, since mining leftovers such as waste heaps and settling ponds are subject to the environmental conditions prevailing at the site and hence, over time, to changes in their properties. Having a fundamental knowledge of patterns of pollutant release behaviour is a crucial prerequisite for formulating the specifications for such sealing systems. Radon (Rn-222) is an element which in some cases attains crucial importance in this regard (Rn-222), since it can make a significant contribution to overall human radiation exposure. This has been confirmed, for example, by studies in preparation of pollution maps as well as by studies conducted by WISMUT GmbH at its Schlema-Alberoda site. In some cases sealing covers for mining leftovers involving elevated radon release rates must be dimensioned such that they effectively shield off radon radiation. Furthermore, suitable methods are needed for monitoring the effectiveness of such sealing covers. [German] Aufgrund der geologischen Gegebenheiten wurden in Sachsen und Thueringen im Zuge unterschiedlicher Bergbautaetigkeiten fast immer auch radioaktive Gesteine zu Tage gefoerdert. Die dabei entstandenen Hinterlassenschaften in Form von Halden, industriellen Absetzanlagen (IAA), Betriebsflaechen, Grubenbauen fuehrten/fuehren z.T. zu einer erheblichen Belastung fuer die Umwelt und die Bevoelkerung. Gemaessdem derzeitigen Stand von Wissenschaft und Technik stellt fuer zahlreiche dieser bergbauliche Hinterlassenschaften die Verwahrung vor Ort mit einer Abdeckung (ggf. komplettiert durch eine Sickerwasserfassung und -behandlung) die optimale Sanierungsloesung dar. Damit soll gesichert werden, dass die von den bergbaulichen Hinterlassenschaften ausgehenden Umweltbeeintraechtigungen langzeitwirksam auf ein vertretbares Massreduziert werden und die betroffenen Flaechen mit vergleichsweise geringem Nachsorgeaufwand einer dem jeweiligen Standort entsprechenden geeigneten Nachnutzung zugefuehrt werden koennen. An die zu konzipierenden und zu realisierenden Abdecksysteme sind dabei hohe Anforderungen hinsichtlich der langzeitwirksamen Funktionalitaet gestellt, da Bergbauobjekte, wie z.B. Halden und IAA's, den an ihrem Standort typischen Umwelteinfluessen unterliegen und somit hinsichtlich ihrer Eigenschaften zeitlichen Veraenderungen unterliegen. Fuer die technische Dimensionierung der Abdecksysteme sind grundlegende Kenntnisse zum Schadstofffreisetzungsverhalten von zentraler Bedeutung. Hierbei nimmt das Radon (Rn-222), dessen Zerfallsprodukte nicht unwesentlich zur Strahlenexposition des Menschen beitragen koennen, z.T. eine Schluesselstellung ein. Dies belegen z.B. die Untersuchungen zum Altlastenkataster und die Untersuchungen der Wismut GmbH fuer den Standort Schlema-Alberoda. Abdeckungen von Bergbauobjekten mit erhoehter Rn-Freisetzung sind deshalb in einigen Faellen so zu dimensionieren, dass sie die Funktion der Radondaemmung ausueben. Des weiteren sind geeignete Methoden zur Kontrolle der Funktionstuechtigkeit solcher Abdeckungen erforderlich.

  17. Study of the influence of bioturbation on covers and contaminated materials on radon shielding using the lead tracing method

    International Nuclear Information System (INIS)

    For geological reasons, mining activities in Thuringia and Saxony have almost always been associated with the excavation of radioactive rock material. The legacy left behind by mining operations, such as waste heaps, industrial settling ponds, abandoned industrial areas and underground mines have posed and for some part still pose a considerable pollution burden for the environment and the population. At the present state of the art in science and technology the best possible remediation solution for these mining leftovers is to retain them in situ by means of a sealing cover(and where necessary provide seepage water retention and treatment). The purpose of such measures is to ensure that the environmental hazards emanating from abandoned mining sites are durably reduced to a tolerable level and the areas concerned can be converted for suitable subsequent uses in a manner adapted to the site in question and with relatively little aftercare required. The sealing systems to be designed and manufactured for this purpose must meet high requirements in terms of long-term effectiveness, since mining leftovers such as waste heaps and settling ponds are subject to the environmental conditions prevailing at the site and hence, over time, to changes in their properties. Having a fundamental knowledge of patterns of pollutant release behaviour is a crucial prerequisite for formulating the specifications for such sealing systems. Radon (Rn-222) is an element which in some cases attains crucial importance in this regard (Rn-222), since it can make a significant contribution to overall human radiation exposure. This has been confirmed, for example, by studies in preparation of pollution maps as well as by studies conducted by WISMUT GmbH at its Schlema-Alberoda site. In some cases sealing covers for mining leftovers involving elevated radon release rates must be dimensioned such that they effectively shield off radon radiation. Furthermore, suitable methods are needed for monitoring the effectiveness of such sealing covers

  18. 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...

  19. Influence of bioturbation by the polychaete Nereis diversicolor on the structure of bacterial communities in oil contaminated coastal sediments

    OpenAIRE

    Cuny, Philippe; Miralles, Gilles; Cornet-Barthaux, Véronique; Acquaviva, Monique; Stora, Georges; Grossi, Vincent; Gilbert, Franck

    2007-01-01

    Patterns of change in the structure of bacterial communities monitored by ribosomal intergenic spacer analysis (RISA) in oil contaminated sediments inhabited or not by the marine polychaete Nereis diversicolor were studied during 45 days under laboratory conditions. Results supported by principal component analysis showed a marked response of the bacterial communities to the oil contamination and to the presence of N. diversicolor. Phylogenetic affiliation of specific RISA bands showed that, ...

  20. Influence of bioturbation by the polychaete Nereis diversicolor on the structure of bacterial communities in oil contaminated coastal sediments.

    Science.gov (United States)

    Cuny, Philippe; Miralles, Gilles; Cornet-Barthaux, Véronique; Acquaviva, Monique; Stora, Georges; Grossi, Vincent; Gilbert, Franck

    2007-04-01

    Patterns of change in the structure of bacterial communities monitored by ribosomal intergenic spacer analysis (RISA) in oil contaminated sediments inhabited or not by the marine polychaete Nereis diversicolor were studied during 45 days under laboratory conditions. Results supported by principal component analysis showed a marked response of the bacterial communities to the oil contamination and to the presence of N. diversicolor. Phylogenetic affiliation of specific RISA bands showed that, in the contaminated sediments, the presence of the marine polychaetes favoured the development of bacteria which may play an active role in natural bioremediation processes of oil polluted environments. PMID:17254615

  1. 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.

  2. Biodégradation des herbicides en sols tempérés - Contrôle des communautés bactériennes dégradantes par la bioturbation du sol

    OpenAIRE

    Monard, Cécile

    2008-01-01

    L'intensification de l'agriculture s'est accompagnée d'une utilisation importante de pesticides qui a généré une pollution généralisée des sols et des eaux, problème environnemental majeur et actuel. Sous la pression de sélection liée à l'usage régulier de pesticides (molécules xénobiotiques) des bactéries du sol se sont adaptées à ces molécules et ont acquis la capacité de les utiliser comme source nutritive et donc de les dégrader. La biodégradation constitue un service écologique majeur fo...

  3. 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.

  4. 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...

  5. Polychaete burrows harbour distinct microbial communities in oil-contaminated coastal sediments.

    Science.gov (United States)

    Taylor, Joe D; Cunliffe, Michael

    2015-08-01

    Previous studies have shown that the bioturbating polychaete Hediste (Nereis) diversicolor can affect the composition of bacterial communities in oil-contaminated sediments, but have not considered diversity specifically within bioturbator burrows or the impact on microbial eukaryotes. We tested the hypothesis that H. diversicolor burrows harbour different eukaryotic and bacterial communities compared with un-bioturbated sediment, and that bioturbation stimulates oil degradation. Oil-contaminated sediment was incubated with or without H. diversicolor for 30 days, after which sediment un-affected by H. diversicolor and burrow DNA/RNA samples were analysed using quantitative reverse transcription PCR (Q-RT-PCR) and high-throughput sequencing. Fungi dominated both burrow and un-bioturbated sediment sequence libraries; however, there was significant enrichment of bacterivorous protists and nematodes in the burrows. There were also significant differences between the bacterial communities in burrows compared with un-bioturbated sediment. Increased activity and relative abundance of aerobic hydrocarbon-degrading bacteria in the burrows coincided with the significant reduction in hydrocarbon concentration in the bioturbated sediment. This study represents the first detailed assessment of the effect of bioturbation on total microbial communities in oil-contaminated sediments. In addition, it further shows that bioturbation is a significant factor in determining microbial diversity within polluted sediments and plays an important role in stimulating bioremediation. PMID:25858418

  6. 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/...

  7. Impact of polychaetes (Nereis spp. and Arenicola marina) on carbon biogeochemistry in coastal marine sediments†

    OpenAIRE

    Kristensen Erik

    2001-01-01

    Known effects of bioturbation by common polychaetes (Nereis spp. and Arenicola marina) in Northern European coastal waters on sediment carbon diagenesis is summarized and assessed. The physical impact of irrigation and reworking activity of the involved polychaete species is evaluated and related to their basic biology. Based on past and present experimental work, it is concluded that effects of bioturbation on carbon diagenesis from manipulated laboratory experiments cannot be directly extr...

  8. Destabilization of cohesive intertidal sediments by infauna

    OpenAIRE

    De Deckere, E.M.G.T.; Tolhurst, T. J.; de Brouwer, J.F.C.

    2001-01-01

    Bioturbation activity was reduced in four plots on an intertidal mudflat in the Humber estuary (UK) during 4 days, by spraying the sediment with an insecticide, namely vydate. Macrofaunal, especially Nereis diversicolor and oligochaeta, and meiofaunal densities decreased, while the diatom biomass did not change. This resulted in a 300% increase in sediment stability, caused by a reduction in bioturbation and grazing pressure and a decrease in the water content.

  9. Destabilization of Cohesive Intertidal Sediments by Infauna

    Science.gov (United States)

    de Deckere, E. M. G. T.; Tolhurst, T. J.; de Brouwer, J. F. C.

    2001-11-01

    Bioturbation activity was reduced in four plots on an intertidal mudflat in the Humber estuary (UK) during 4 days, by spraying the sediment with an insecticide, namely vydate. Macrofaunal, especially Nereis diversicolor and oligochaeta, and meiofaunal densities decreased, while the diatom biomass did not change. This resulted in a 300% increase in sediment stability, caused by a reduction in bioturbation and grazing pressure and a decrease in the water content.

  10. 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.

  11. 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.

  12. Influence of Chironomus riparius (Diptera, Chironomidae) and Tubifex tubifex (Annelida, Oligochaeta) on oxygen uptake by sediments. Consequences of uranium contamination.

    Science.gov (United States)

    Lagauzère, S; Pischedda, L; Cuny, P; Gilbert, F; Stora, G; Bonzom, J-M

    2009-04-01

    The diffusive oxygen uptake (DOU) of sediments inhabited by Chironomus riparius and Tubifex tubifex was investigated using a planar oxygen optode device, and complemented by measurements of bioturbation activity. Additional experiments were performed within contaminated sediments to assess the impact of uranium on these processes. After 72h, the two invertebrate species significantly increased the DOU of sediments (13-14%), and no temporal variation occurred afterwards. Within contaminated sediments, it was already 24% higher before the introduction of the organisms, suggesting that uranium modified the sediment biogeochemistry. Although the two species firstly reacted by avoidance of contaminated sediment, they finally colonized it. Their bioturbation activity was reduced but, for T. tubifex, it remained sufficient to induce a release of uranium to the water column and an increase of the DOU (53%). These results highlight the necessity of further investigations to take into account the interactions between bioturbation, microbial metabolism and pollutants. PMID:19121883

  13. The usefullness of KD models for the description of the migration of radionuclides in soils

    International Nuclear Information System (INIS)

    For radionuclides which are reversibly adsorbed and the KD (ratio between the amount of radionuclides adsorbed on a soil and the amount present in the liquid phase) is so small that migration due to bioturbation is small compared to physical chemical migration, the KD concept is valid. Irreversible adsorption phenomena decrease the usefulness of the KD concept. For very high KD values the concept cannot be used for the upper layers of soil because migration due to bioturbation dominates in this case. (orig./HP)

  14. The Glossifungites and Trypanites Ichnofacies on a weathered (and subsequently re-compacted) metavolcanic rock (Cretaceous, Czech Republic)

    Czech Academy of Sciences Publication Activity Database

    Mikuláš, Radek; Němečková, Monika; Adamovič, Jiří

    Barcelona : Universitat de Barcelona, 2000, s. 25-26. [International Bioerosion Workshop /3./. Barcelona (ES), 28.08.2000-03.09.2000] Institutional research plan: CEZ:AV0Z3013912 Keywords : bioerosion * bioturbation * transgressive sediments Subject RIV: DB - Geology ; Mineralogy

  15. 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

  16. Influence of Chironomus riparius (Diptera, Chironomidae) and Tubifex tubifex (Annelida, Oligochaeta) on oxygen uptake by sediments. Consequences of uranium contamination

    Energy Technology Data Exchange (ETDEWEB)

    Lagauzere, S. [Laboratoire de Radioecologie et d' Ecotoxicologie, Institut de Radioprotection et de Surete Nucleaire (IRSN), DEI/SECRE/LRE, Cadarache 186, BP 3, F-13115 Cedex, Saint Paul Lez Durance (France)], E-mail: lagauzere@gmail.com; Pischedda, L.; Cuny, P. [Laboratoire de Microbiologie, Geochimie et Ecologie Marines, UMR 6117 CNRS/COM/Universite de la Mediterranee, Campus de Luminy, Case 901, F-13288 Cedex 09, Marseille (France); Gilbert, F. [EcoLab, Laboratoire d' Ecologie Fonctionnelle, UMR 5245 CNRS/INP/Universite Paul Sabatier, 29 Rue Jeanne Marvig, F-31055 Cedex 4, Toulouse (France); Stora, G. [Laboratoire de Microbiologie, Geochimie et Ecologie Marines, UMR 6117 CNRS/COM/Universite de la Mediterranee, Campus de Luminy, Case 901, F-13288 Cedex 09, Marseille (France); Bonzom, J.-M. [Laboratoire de Radioecologie et d' Ecotoxicologie, Institut de Radioprotection et de Surete Nucleaire (IRSN), DEI/SECRE/LRE, Cadarache 186, BP 3, F-13115 Cedex, Saint Paul Lez Durance (France)

    2009-04-15

    The diffusive oxygen uptake (DOU) of sediments inhabited by Chironomus riparius and Tubifex tubifex was investigated using a planar oxygen optode device, and complemented by measurements of bioturbation activity. Additional experiments were performed within contaminated sediments to assess the impact of uranium on these processes. After 72 h, the two invertebrate species significantly increased the DOU of sediments (13-14%), and no temporal variation occurred afterwards. Within contaminated sediments, it was already 24% higher before the introduction of the organisms, suggesting that uranium modified the sediment biogeochemistry. Although the two species firstly reacted by avoidance of contaminated sediment, they finally colonized it. Their bioturbation activity was reduced but, for T. tubifex, it remained sufficient to induce a release of uranium to the water column and an increase of the DOU (53%). These results highlight the necessity of further investigations to take into account the interactions between bioturbation, microbial metabolism and pollutants. - This study highlights the ecological importance of bioturbation in metal-contaminated sediments.

  17. Influence of Chironomus riparius (Diptera, Chironomidae) and Tubifex tubifex (Annelida, Oligochaeta) on oxygen uptake by sediments. Consequences of uranium contamination

    International Nuclear Information System (INIS)

    The diffusive oxygen uptake (DOU) of sediments inhabited by Chironomus riparius and Tubifex tubifex was investigated using a planar oxygen optode device, and complemented by measurements of bioturbation activity. Additional experiments were performed within contaminated sediments to assess the impact of uranium on these processes. After 72 h, the two invertebrate species significantly increased the DOU of sediments (13-14%), and no temporal variation occurred afterwards. Within contaminated sediments, it was already 24% higher before the introduction of the organisms, suggesting that uranium modified the sediment biogeochemistry. Although the two species firstly reacted by avoidance of contaminated sediment, they finally colonized it. Their bioturbation activity was reduced but, for T. tubifex, it remained sufficient to induce a release of uranium to the water column and an increase of the DOU (53%). These results highlight the necessity of further investigations to take into account the interactions between bioturbation, microbial metabolism and pollutants. - This study highlights the ecological importance of bioturbation in metal-contaminated sediments

  18. Types of soft-sediment deformation structures in a lacustrine Ploužnice member (Stephanian, Gzhelian, Pennsylvanian, Bohemian Massif), their timing, and possible trigger mechanism

    Czech Academy of Sciences Publication Activity Database

    Stárková, M.; Martínek, K.; Mikuláš, Radek; Rosenau, N.

    2015-01-01

    Roč. 104, č. 5 (2015), s. 1277-1298. ISSN 1437-3254 Institutional support: RVO:67985831 Keywords : soft-sediment deformation structures * bioturbation * early diagenetic carbonate * lacustrine facies * Bohemian Massif * Stephanian C * Krkonoše Piedmont Basin Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.093, year: 2014

  19. 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

  20. A Large Trace Fossil in Nodular Limestones (Lower Devonian, Czech Republic): Sedimentological Consequences, Ethology and Taphonomy

    Czech Academy of Sciences Publication Activity Database

    Mikuláš, Radek; Hladil, Jindřich

    2015-01-01

    Roč. 22, č. 2 (2015), s. 69-76. ISSN 1042-0940 R&D Projects: GA ČR GA14-18183S Institutional support: RVO:67985831 Keywords : bioturbation * Fodinichnia * carbonate * nodules * Devonian * Czech Republic Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.077, year: 2014

  1. Insect burrows (dwelling/brending chambers and tunnels) in the archaeological context of Abusir

    Czech Academy of Sciences Publication Activity Database

    Mikuláš, Radek; Cílek, Václav

    Vol. 2. Prague : Czech Institute of Egyptology , Faculty of Arts, Charles University in Prague, 2011 - (Bárta, M.; Coppens, F.; Krejčí, J.), s. 635-650 ISBN 978-80-7308-385-4 Institutional research plan: CEZ:AV0Z30130516 Keywords : insect burrows * Hymenoptera * ichnology * Abusir * bioerosion * bioturbation Subject RIV: DB - Geology ; Mineralogy

  2. 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...

  3. Punctuated sediment record resulting from channel migration in a shallow sand-dominated micro-tidal lagoon, Northern Wadden Sea, Denmark

    DEFF Research Database (Denmark)

    Fruergaard, Mikkel; Andersen, Thorbjørn Joest; Nielsen, Lars Henrik;

    2011-01-01

    caused the formation of a punctuated lagoonal fill. Frequent and comprehensive reworking of the sand flat sediments by tidal channel migration entails loss of sedimentary structures and bioturbation related to sand flat deposits, and old sand flat sediments are only very sparsely preserved. We further...

  4. 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

    be covalently bound to, e.g. DNA, RNA or proteins, thus reducing pyrene bioavailability to arm-cropping predators. The sedimentary pyrene distribution and metabolism was species-dependent, but correlated poorly with prevailing knowledge on species-specific bioturbation patterns. This was attributed...

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

    DEFF Research Database (Denmark)

    Mangano, M. Gabriela; Bromley, Richard Granville; Harper, David A.T.; Nielsen, Arne Thorshøj; Smith, M. Paul; Vinther, Jakob

    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-c...... served as the primary food for small macrofauna and meiofauna....

  6. 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-...

  7. Is the effect of trees on soil properties mediated by soil fauna? A case study from post-mining sites

    Czech Academy of Sciences Publication Activity Database

    Frouz, J.; Livečková, M.; Albrechtová, J.; Chroňáková, Alica; Cajthaml, Tomáš; Pižl, Václav; Háněl, Ladislav; Starý, Josef; Baldrian, Petr; Lhotáková, Z.; Šimáčková, H.; Cepáková, Šárka

    2013-01-01

    Roč. 309, December (2013), s. 87-95. ISSN 0378-1127 R&D Projects: GA ČR GAP504/12/1288; GA MŠk LC06066 Institutional support: RVO:60077344 ; RVO:61388971 Keywords : bioturbation * earthworms * foliage chemistry * microorganisms * reclamation * soil fauna Subject RIV: EH - Ecology, Behaviour Impact factor: 2.667, year: 2013

  8. Effects of copper on invertebrate–sediment interactions

    International Nuclear Information System (INIS)

    Toxicants potentially decouple links between biodiversity and ecosystem processes. This study aimed to evaluate how toxicants affect invertebrate bioturbation and decomposition. Effects of copper on functionally distinct macrofaunal species (Asellus aquaticus and Tubifex spp.), decomposition (release of dissolved organic carbon, DOC) and Average Metabolic Response (AMR) and Community Metabolic Diversity (CMD) of bacteria were determined in 5-day microcosm experiments. Bioturbation was assessed as sediment redox potential (Eh) profiles. Concentration–response curves of the functional parameters DOC, and the faunal mediated AMR and CMD in the presence of Tubifex spp. depended on Tubifex spp. survival, i.e. similar EC50 values for both endpoints. In contrast, functional parameters in the presence of A. aquaticus were more sensitive than survival. Sediment Eh-profiles showed that reduced decomposition was caused by reduced sediment reworking by A. aquaticus at sub-lethal copper concentrations. These observations hint at a decoupling of invertebrate community structure and ecosystem functioning upon stress. -- Highlights: •We compared invertebrate survival and functional responses to copper amendment. •Differential functional responses depending on invertebrate species. •Reduced functional responses with A. aquaticus at sub-lethal copper concentrations. •Sub-lethal copper concentrations reduced the bioturbating activities of A. aquaticus. •Stress decouples invertebrate community structure and ecosystem functioning. -- Sub-lethal copper concentrations reduced the bioturbating activities of A. aquaticus and invertebrate effects on decomposition, bacterial activity and community metabolic diversity

  9. 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...

  10. Do soil fauna really hasten litter decomposition? A meta-analysis of enclosure studies

    Czech Academy of Sciences Publication Activity Database

    Frouz, J.; Roubíčková, A.; Heděnec, P.; Tajovský, Karel

    2015-01-01

    Roč. 68, May-June (2015), s. 18-24. ISSN 1164-5563 Grant ostatní: GA ČR(CZ) GAP504/12/1288 Institutional support: RVO:60077344 Keywords : Invertebrates * bioturbation * soil organic matter * carbon cycle * litter bag Subject RIV: DF - Soil Science Impact factor: 1.719, year: 2014

  11. 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

  12. Impact of polychaetes (Nereis spp. and Arenicola marina on carbon biogeochemistry in coastal marine sediments†

    Directory of Open Access Journals (Sweden)

    Kristensen Erik

    2001-10-01

    Full Text Available Known effects of bioturbation by common polychaetes (Nereis spp. and Arenicola marina in Northern European coastal waters on sediment carbon diagenesis is summarized and assessed. The physical impact of irrigation and reworking activity of the involved polychaete species is evaluated and related to their basic biology. Based on past and present experimental work, it is concluded that effects of bioturbation on carbon diagenesis from manipulated laboratory experiments cannot be directly extrapolated to in situ conditions. The 45–260% flux (e.g., CO2 release enhancement found in the laboratory is much higher than usually observed in the field (10–25%. Thus, the faunal induced enhancement of microbial carbon oxidation in natural sediments instead causes a reduction of the organic matter inventory rather than an increased release of CO2 across the sediment/water interface. The relative decrease in organic inventory (Gb/Gu is inversely related to the relative increase in microbial capacity for organic matter decay (kb/ku. The equilibrium is controlled by the balance between organic input (deposition of organic matter at the sediment surface and the intensity of bioturbation. Introduction of oxygen to subsurface sediment and removal of metabolites are considered the two most important underlying mechanisms for the stimulation of carbon oxidation by burrowing fauna. Introduction of oxygen to deep sediment layers of low microbial activity, either by downward irrigation transport of overlying oxic water or by upward reworking transport of sediment to the oxic water column will increase carbon oxidation of anaerobically refractory organic matter. It appears that the irrigation effect is larger than and to a higher degree dependent on animal density than the reworking effect. Enhancement of anaerobic carbon oxidation by removal of metabolites (reduced diffusion scale may cause a significant increase in total sediment metabolism. This is caused by three

  13. 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.

  14. 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...

  15. 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.

  16. Animal burrowing attributes affecting hazardous waste management

    International Nuclear Information System (INIS)

    Animal burrowing is critical to the formation of soils and contributes to the interface between geological materials and organic life. It also influences the management of hazardous materials at nuclear waste facilities and elsewhere. For example, residues and waste products from the production of nuclear weapons are released onto the ground surface and within engineered burial structures. Soil bioturbation has exposed radionuclides and other hazardous materials to wind and rain, thereby risking inhalation and injury to humans and wildlife on and off site. Soil bioturbation can expand soil depths and spatial distributions of the source term of hazardous waste, potentially increasing chronic exposures to wildlife and humans over the long term. Ample evidence indicates that some of the large quantities of hazardous materials around the world have been released from soil repositories, where they have also contaminated and harmed biota

  17. Meiofauna increases bacterial denitrification in marine sediments.

    Science.gov (United States)

    Bonaglia, S; Nascimento, F J A; Bartoli, M; Klawonn, I; Brüchert, V

    2014-01-01

    Denitrification is a critical process that can alleviate the effects of excessive nitrogen availability in aquatic ecosystems subject to eutrophication. An important part of denitrification occurs in benthic systems where bioturbation by meiofauna (invertebrates macrofauna, on nitrate reduction, carbon mineralization and methane fluxes. In sediments with abundant and diverse meiofauna, denitrification is double that in sediments with low meiofauna, suggesting that meiofauna bioturbation has a stimulating effect on nitrifying and denitrifying bacteria. However, high meiofauna densities in the presence of bivalves do not stimulate denitrification, while dissimilatory nitrate reduction to ammonium rate and methane efflux are significantly enhanced. We demonstrate that the ecological interactions between meio-, macrofauna and bacteria are important in regulating nitrogen cycling in soft-sediment ecosystems. PMID:25318852

  18. 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...... known. The well-documented decline of soft-bodied preservation following the Middle Cambrian represents the closure of a taphonomic window that was only intermittently open in marine environments thereafter. The prevailing hypothesis for this secular shift in taphonomic conditions of outer shelf......, 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...

  19. Macrofaunal diversity in the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pavithran, S.; Ingole, B.S.; Nanajkar, M.; Nath, B.N.

    faunal assemblages. The high diversity of most deep-sea communities is well known (Gage 1996). These animals are adapted to high pressure, low temperature, stable oxygen and salinity conditions. Any mining activities in the deep-sea are expected.... Bioturbation may also change sediment surface topography and the pits and mounds created by benthic fauna can impact where particles are likely to collect on the seafloor (Yager et al. 1993). Individual deep-sea animals mix the sediment at about the same...

  20. Biotic interaction between earthworms and pesticide degrading bacteria - Impact on the detoxification service of soil

    OpenAIRE

    Monard, Cécile; Vandenkoornhuyse, Philippe; Martin-Laurent, Fabrice; Binet, Françoise

    2010-01-01

    Earthworms are efficient soil engineers that change the physical and chemical properties of soil and act in turn on soil microbial communities. Earthworm bioturbation will thus impact microbial processes in soil and also the generated ecosystemic services such as detoxification function. By using RNA based Stable Isotope Probing we demonstrated that the bacterial communities responsive to 13 C enrichments in earthworm casts were different from those in bulk soil resulting in different degrada...

  1. 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...

  2. 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 ...

  3. 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.

  4. 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

  5. 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

  6. 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...

  7. 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...

  8. 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)

  9. 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...

  10. 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 ...

  11. 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.

  12. 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...

  13. 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...

  14. 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.

  15. Phytopigments as biomarkers of selectivity in abyssal holothurians; interspecific differences in response to a changing food supply

    OpenAIRE

    FitzGeorge-Balfour, Tania; Billett, David S.M.; Wolff, George A.; Thompson, Anu; Tyler, Paul A.

    2010-01-01

    Holothurians dominate the abyssal megabenthos. They are key consumers and bioturbators of surficial sediment. Compounds essential for holothurian reproduction, such as carotenoids, are in short supply in the deep ocean. Holothurians cannot synthesise carotenoids de novo; the compounds are supplied with the flux of phytodetritus. Therefore, the supply of these compounds may play an important role in regulating processes on the seafloor. This study examines the link between the diet of abyssal ...

  16. Analysis and application of ichnofabrics

    Science.gov (United States)

    Taylor, Andrew; Goldring, Roland; Gowland, Stuart

    2003-02-01

    Bioturbation at all scales, which tends to replace the primary fabric of a sediment by the ichnofabric (the overall fabric of a sediment that has been bioturbated), is now recognised as playing a major role in facies interpretation. The manner in which the substrate may be colonized, and the physical, chemical and ecological controls (grainsize, sedimentation rate, oxygenation, nutrition, salinity, ethology, community structure and succession), together with the several ways in which the substrate is tiered by bioturbators, are the factors and processes that determine the nature of the ichnofabric. Eleven main styles of substrate tiering are described, ranging from single, pioneer colonization to complex tiering under equilibria, their modification under environmental deterioration and amelioration, and diagenetic enhancement or obscuration. Ichnofabrics may be assessed by four attributes: primary sedimentary factors, Bioturbation Index (BI), burrow size and frequency, and ichnological diversity. Construction of tier and ichnofabric constituent diagrams aid visualization and comparison. The breaks or changes in colonization and style of tiering at key stratal surfaces accentuate the surfaces, and many reflect a major environmental shift of the trace-forming biota due to change in hydrodynamic regime (leading to non-deposition and/or erosion and/or lithification), change in salinity regime, or subaerial exposure. The succession of gradational or abrupt changes in ichnofabric through genetically related successions, together with changes in colonization and tiering across event beds, may also be interpreted in terms of changes in environmental parameters. It is not the ichnotaxa per se that are important in discriminating between ichnofabrics, but rather the environmental conditions that determine the overall style of colonization. Fabrics composed of different ichnotaxa (and different taphonomies) but similar tier structure and ichnoguild may form in similar

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

    OpenAIRE

    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. Unde...

  18. Cross-stratigraphies from a seismically active mud lens off Peru indicate horizontal extensions of laminae, missing sequences, and a need for multiple cores for high resolution records

    OpenAIRE

    R. Salvatteci; Field, D.; Sifeddine, Abdelfettah; Ortlieb, Luc; Ferreira, V.; Baumgartner, T.; Caquineau, Sandrine; Velazco, F.; Reyss, J. L.; Sanchez-Cabeza, J. A.; Gutierrez, D.

    2014-01-01

    Marine laminated sediments in dysoxic areas of the ocean floor are an excellent archive for high-resolution climate reconstructions. While the existence of discontinuities produced by natural events, such as underwater landslides (slumps), strong bottom currents, and/or bioturbation is usually acknowledged for long records, the extent of their influence on high-resolution sequences is usually not considered. In the present work we show strong evidence for multiple stratigraphic discontinuitie...

  19. 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...

  20. 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-...

  1. 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...

  2. Influence of Chironomus riparius (Diptera, Chironomidae) and Tubifex tubifex (Annelida, Oligochaeta) on oxygen uptake by sediments. Consequences of uranium contamination

    OpenAIRE

    Lagauzère, Sandra; Pischedda, Laura; Cuny, Philippe; Gilbert, Franck; Stora, Georges; Bonzom, Jean-Marc

    2009-01-01

    The diffusive oxygen uptake (DOU) of sediments inhabited by Chironomus riparius and Tubifex tubifex was investigated using a planar oxygen optode device, and complemented by measurements of bioturbation activity. Additional experiments were performed within contaminated sediments to assess the impact of uranium on these processes. After 72 h, the two invertebrate species significantly increased the DOU of sediments (13–14%), and no temporal variation occurred afterwards. Within contaminated s...

  3. 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...

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

    OpenAIRE

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

    2015-01-01

    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 und...

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

    OpenAIRE

    I. Ferro; 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 marine 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 rates as reflected in pore-water and solid phase profiles, and in sediment-water exchange fluxes. We also studied the effect of Nereis diversicolor on iron and manganese biogeochemistry. The pres...

  6. Effects of population density on the sediment mixing induced by the gallery-diffusor Hediste (Nereis) diversicolor O.F. Müller, 1776

    OpenAIRE

    Duport, Eric; Stora, Georges; Tremblay, Pierre; Gilbert, Franck

    2006-01-01

    The aim of this work was to quantify the intensity of sediment mixing induced by the gallery-diffusor (functional bioturbation group) Hediste diversicolor as a function of density, using particles tracers (luminophores). In order to assess the impact of density on sediment reworking, a 1-D model was used to obtain sediment reworking coefficients such as Db (biodiffusion-like) and r (biotransport). Densities used in this experiment corresponded to population densities observed in the sampling ...

  7. Characterization of specificity of bacterial community structure within the burrow environment of the marine polychaete Hediste (Nereis) diversicolor

    OpenAIRE

    Pischedda, Laura; Militon, Cécile; Gilbert, Franck; Cuny, Philippe

    2011-01-01

    Bioturbation is known to stimulate microbial communities, especially in macrofaunal burrows where the abundance and activities of bacteria are increased. Until now, these microbial communities have been poorly characterized and an important ecological question remains: do burrow walls harbor similar or specific communities compared with anoxic and surface sediments? The bacterial community structure of coastal sediments inhabited by the polychaete worm Hediste diversicolor was investigated. S...

  8. Implications for oxygen, nutrient fluxes and denitrification rates during the early stage of sediment colonisation by the polychaete Nereis spp. in four estuaries

    Science.gov (United States)

    Nizzoli, Daniele; Bartoli, Marco; Cooper, Martin; Welsh, David T.; Underwood, Graham J. C.; Viaroli, Pierluigi

    2007-10-01

    In this work, bioturbation effects by the polychaete Nereis spp. on oxygen demand, denitrification and solute fluxes in four European coastal areas (Goro lagoon in Italy, Tagus estuary in Portugal, Colne estuary in England and Tjärnö bay in Sweden) are compared. The studied areas are very heterogeneous with respect to tidal regimes, primary producers communities, sediment composition and organic matter content and nutrient concentrations in the water column. At each site, with the same methodological approach, undisturbed sediment cores and cores with different numbers of polychaetes added were incubated in the dark. Oxygen, inorganic nutrients (NH 4+, NO 3-, Dissolved Reactive Silica-SiO 2 and Soluble Reactive Phosphorous-SRP) fluxes and coupled-uncoupled denitrification rates were quantified on the same set of cores. Nereis bioturbation had a considerable effect on biogeochemical processes and, at all sites, resulted in an immediate stimulation (from 1.5- to 4-fold higher) of oxygen and ammonium fluxes between the sediment and the water column; on the contrary bioturbation had site specific effects on reactive silica and phosphorus fluxes. Bioturbation also stimulated denitrification of water column nitrate ( Dw, from 1.3 to 3 times higher than in control sediments); this process removed a major fraction (>50%) of the nitrogen lost through denitrification. Overall, the strong relationship between benthic macrofauna activity and sediment biogeochemistry is confirmed by this study. Comparison of the relative stimulation of processes in different geographical areas reveals that the degree by which processes and fluxes (intensity and direction) are affected are site specific and influenced by initial macrofauna densities and sediment and water chemistry.

  9. Indications of low macrobenthic activity in the deep sediments of the Eastern Mediterranean Sea

    OpenAIRE

    Basso, D; Thomson, J; C. Corselli

    2004-01-01

    The fluxes and budget of organic matter from the oligotrophic surface waters of the eastern Mediterranean to the deep waters are poorly known, and little information is available on past and present macrobenthic activity on the sea floor. Evidence of macrobenthic activity can be direct, through recovery of living organisms or their autochthonous skeletal remains, or indirect, through bioturbation and trace fossils. The evidence of biological activity in deep eastern Mediterranean sediments ha...

  10. 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

  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. Changes in benthic ecosystems and ocean circulation in the Southeast Atlantic across Eocene Thermal Maximum 2

    Science.gov (United States)

    Jennions, S. M.; Thomas, E.; Schmidt, D. N.; Lunt, D.; Ridgwell, A.

    2015-08-01

    Eocene Thermal Maximum 2 (ETM2) occurred ~1.8 Myr after the Paleocene-Eocene Thermal Maximum (PETM) and, like the PETM, was characterized by a negative carbon isotope excursion and warming. We combined benthic foraminiferal and sedimentological records for Southeast Atlantic Sites 1263 (1500 m paleodepth) and 1262 (3600 m paleodepth) to show that benthic foraminiferal diversity and accumulation rates declined more precipitously and severely at the shallower site during peak ETM2. As the sites are in close proximity, differences in surface productivity cannot have caused this differential effect. Instead, we infer that changes in ocean circulation across ETM2 may have produced more pronounced warming at intermediate depths (Site 1263). The effects of warming include increased metabolic rates, a decrease in effective food supply and increased deoxygenation, thus potentially explaining the more severe benthic impacts at Site 1263. In response, bioturbation may have decreased more at Site 1263 than at Site 1262, differentially affecting bulk carbonate records. We use a sediment-enabled Earth system model to test whether a reduction in bioturbation and/or the likely reduced carbonate saturation of more poorly ventilated waters can explain the more extreme excursion in bulk δ13C and sharper transition in wt % CaCO3 at Site 1263. We find that both enhanced acidification and reduced bioturbation during the ETM2 peak are needed to account for the observed features. Our combined ecological and modeling analysis illustrates the potential role of ocean circulation changes in amplifying local environmental changes and driving temporary, but drastic, loss of benthic biodiversity and abundance.

  14. Recently studied sedimentary records from the eastern Arabian Sea: Implications to Holocene monsoonal variability

    Digital Repository Service at National Institute of Oceanography (India)

    Agnihotri, R.; Kurian, S.

    ://www.earthscienceindia.info/Agnihotri.htm 1 of 14 10/15/2008 9:41 AM Earth Science India Vol.1 (IV), October, 2008, pp. 258-287 http://www.earthscienceindia.info/ Recently studied sedimentary records from the eastern Arabian Sea: Implications to Holocene monsoonal variability Rajesh... biogenic (organic and inorganic) proxies with minimal particle reworking through bioturbation. Agnihotri http://www.earthscienceindia.info/Agnihotri.htm 2 of 14 10/15/2008 9:41 AM Figure 1: Satellite pictures of the Arabian Sea revealing seasonal contrast...

  15. 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

  16. 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.

  17. 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...

  18. 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.

  19. Simultaneous loss of soil biodiversity and functions along a copper contamination gradient

    DEFF Research Database (Denmark)

    Naveed, Muhammad; Moldrup, Per; Arthur, Emmanuel;

    2014-01-01

    recycling of nutrients and organic waste) along a legacy copper (Cu) pollution gradient. Increasing Cu concentrations had detrimental impact on both plant growth and species richness. Belowground soil biota showed similar response with their sensitivity to elevated Cu concentrations decreasing in the...... following order: earthworms > bacteria > nematodes > fungi. The observed loss of soil biota adversely affected natural soil bioturbation, aggregate formation/stabilization, decomposition and mineralization processes, and therefore resulted in compacted soil with narrow pore size distributions and overall...... different soil biodiversity and functional indicators started to decline (10% loss) within a copper concentration range of 110-800 mg total Cu kg-1....

  20. 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)

  1. 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

  2. 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.

  3. 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

  4. Be-7 and Th-234 as tracers of sediment mixing on seasonal time at the water-sediment interface of the Thau pond

    International Nuclear Information System (INIS)

    We report detailed depth profiles of the particle-reactive radionuclides 234Th (24.1 days) and 7Be (53.3 days) in sediment cores collected at different seasons in the Thau Lagoon, located in the south of France. Cores were collected at two selected sites with contrasting characteristics: C4 in the middle of the lagoon and C5 nearby oyster farming. Both sites were visited six times between December 2001 and May 2003. 234Th in excess (234Thxs; i.e. supplied to sediment by settling particles) and 7Be both show seasonal variations in activities and in penetration within the sediment. Uppermost activities of 234Thxs and 7Be range between 20 and 72 mBq g-1 at site C4 and between 30 and 166 mBq g-1 at site C5. With their very short half-lives and moderate sedimentation rates at both sites (around 0.1 - 0.3 cm per year), 234Thxs and 7Be should be present only at the water-sediment interface. However all the profiles show penetration of both short-lived radionuclides to variable depths, from 1 up to 8 cm, that indicates efficient mixing of upper sediments, usually referred as bioturbation. The simplest way to calculate Db from radionuclide profiles assumes bioturbation as a diffusive process occurring at a constant rate within a surface mixed layer under steady state. For site C4, steady-state bioturbation rates range between 1 and 12 cm2 yr-1, with a weak seasonal signal. The mixing of surface sediments at site C5 presents a greater range (1 34 cm2 yr-1) with the highest values observed in summer. Such a time-series of short radionuclides at the water sediment is most unusual. It provides the opportunity to develop a non-steady state modeling in order to test the significance of bioturbation rates based on steady state assumption. Results of this test will be discussed. (author)

  5. Biological processes influencing contaminant release from sediments

    International Nuclear Information System (INIS)

    The influence of biological processes, including bioturbation, on the mobility of contaminants in freshwater sediments is described. Effective mass coefficients are estimated for tubificid oligochaetes as a function of worm behavior and biomass density. The mass transfer coefficients were observed to be inversely proportional to water oxygen content and proportional to the square root of biomass density. The sediment reworking and contaminant release are contrasted with those of freshwater amphipods. The implications of these and other biological processes for contaminant release and i n-situ remediation of soils and sediments are summarized. 4 figs., 1 tab

  6. 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

  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. 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.

  9. Coastal marine sediment sampling for radionuclide analysis

    International Nuclear Information System (INIS)

    January 1968, a B52 plane carrying 4 nuclear weapons crashed on the sea ice ∼12 km from the Thule Air Base, Northwest Greenland. The benthic marine environment in the 180-230 m deep Bylot Sound was then contaminated with ∼1.4 TBq 239,240Pu (∼0.5 kg). The site was revisited August 1997. Due to the single plutonium injection well defined in time the site is an interesting test case for sediment dating. The present data support an earlier quantification of the sedimentation rate as 3-4 mm per year, i.e. 8-12 cm during the 29 years since the accident. Biological activity has mixed accident plutonium much deeper, down to 20-30 cm, and the 8-12 cm new sediment have been efficiently mixed into the contaminated layer. In addition to the classical bioturbation mixing the upper ∼ 5 cm, the plutonium data indicates the existence of a deeper mixing, probably also caused by bioturbation. This could have implications for the use of excess 210Pb as a sedimentation rate chronometer in coastal environments with rich biological activity. (author)

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. Plutonium in an arctic marine environment 29 years after the Thule accident

    International Nuclear Information System (INIS)

    The nuclear weapons contaminated benthic marine environment in the 180-230 m deep Bylot Sound of Thule Airbase, NW Greenland, was revisited August 1997. Data on water and on brown algae indicates that plutonium from the contaminated sediments is not transported 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 ealier quantification of the sedimentation rate as 3-4 mm per year, i.e. 8-12 cm during the 29 years since the accident. Biological activity has mixed accident plutonium much deeper, down to 20-30 cm, and the 8-12 cm new sediment have been efficiently mixed into the contaminated layer. In addition to the classical bioturbation efficiently mixing the upper ≅ 5 cm, the plutonium data indicates the existence of a deeper bioturbation gradualy decreasing with depth. Transfer of plutonium to benthic biota is low leading to lower concentrations in biota than in sediments. (au)

  15. Factors Influencing Internal Phosphorus Loading in Spring Lake, Michigan

    Science.gov (United States)

    Steinman, A.; Nemeth, L.; Rediske, R.

    2005-05-01

    Spring Lake is a eutrophic, drowned river mouth lake that drains into the Grand River about 1 km upstream from Lake Michigan. In 2003, we determined that internal P loading accounted for approximately 65% of the total annual P load to this lake, and that an alum concentration of 24 mg/L effectively inactivated P release in experimental sediment core tubes. In 2004, we studied the influence of alum concentration, sediment resuspension, and bioturbation on P release rates from the sediments. Based on laboratory incubations, we determined that P release rates were no different at alum concentrations of 15 mg alum/L than at concentrations of 25 mg/L. Resuspension of sediments substantially increased TP concentrations, even at high alum concentrations, although total soluble phosphorus concentrations remained low in the water provided alum was present. Bioturbation did not appear to play a major factor with respect to P release in these sediments. Given the current concentration of phosphorus in the Spring Lake sediments, internal P loading can continue for another 40 years, even if all external P sources were immediately eliminated.

  16. Effects of copper on invertebrate-sediment interactions.

    Science.gov (United States)

    Hunting, E R; Mulder, C; Kraak, M H S; Breure, A M; Admiraal, W

    2013-09-01

    Toxicants potentially decouple links between biodiversity and ecosystem processes. This study aimed to evaluate how toxicants affect invertebrate bioturbation and decomposition. Effects of copper on functionally distinct macrofaunal species (Asellus aquaticus and Tubifex spp.), decomposition (release of dissolved organic carbon, DOC) and Average Metabolic Response (AMR) and Community Metabolic Diversity (CMD) of bacteria were determined in 5-day microcosm experiments. Bioturbation was assessed as sediment redox potential (Eh) profiles. Concentration-response curves of the functional parameters DOC, and the faunal mediated AMR and CMD in the presence of Tubifex spp. depended on Tubifex spp. survival, i.e. similar EC50 values for both endpoints. In contrast, functional parameters in the presence of A. aquaticus were more sensitive than survival. Sediment Eh-profiles showed that reduced decomposition was caused by reduced sediment reworking by A. aquaticus at sub-lethal copper concentrations. These observations hint at a decoupling of invertebrate community structure and ecosystem functioning upon stress. PMID:23747821

  17. 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.)

  18. 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

  19. 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

  20. 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

  1. 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

  2. Depth profiles of environmental radionuclides (40K, 226Ra, 210Pb and 137Cs) in temperate forest soils in Germany

    International Nuclear Information System (INIS)

    Depth profiles of environmental radionuclides (40K, 226Ra, 210Pb and 137Cs) were investigated in several temperate forest soils in Germany to estimate heterogeneity of the soil horizon of interest. Absolute values of the activity concentrations of these nuclides varied to a large extent depending on the properties of individual forests as well as local geology. Activity concentrations of 40K increased with increasing soil density reflecting that most potassium is contained in mineral components of the soil. The variations in the 40K activity with depth may relate to biological activities in subsoil, such as root uptake of the nutrients. Consequences of bioturbation could be deduced from variability in vertical profiles of the environmental radionuclides like 137Cs and 210Pb. (author)

  3. Survey of the marine benthic infauna collected from the United States radioactive waste disposal sites off the Farallon Islands, California. Final report

    International Nuclear Information System (INIS)

    Benthic biological samples were taken in 1977 from the vicinity of the Farallon Islands radioactive waste disposal sites for characterization of the infaunal macroinvertebrates and foraminifera. A total of 120 invertebrate species were collected, of which 75 species (63 percent) were polychaetes. Forty-three of these polychaete species have not previously been reported from depths greater than 1000m. A total of 1044 macroinvertebrate specimens were collected of which 54 percent were polychates. Only the nematods were present at all six benthic stations, but the community structure was dominated by the polychaetes Tauberia gracilis, Allia pulchra, Chaetozone setosa, and Cossura candida. Living and dead foraminifera were reported. The possible role of polychaetes in bioturbation and in the marine food chain is briefly discussed with respect to the various polychaete feeding mechanisms

  4. 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

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

    DEFF Research Database (Denmark)

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

    2012-01-01

    initial deglaciation. Both the slope and outer shelf were deglaciated and strongly influenced by the WGC at 14,070 cal kyr BP, as evidenced by a correlative Northern Baffin Bay detrital carbonate event dated in two of the cores. The radiocarbon dates provide the minimum age of ice retreat and the...... analyses, lithofacies changes, mineralogy and IRD. The sediment sequence in the cores is comprised of basal diamictons that represent either glacigenic debris flows or glacial till that transition to stratified and massive pebbly mud to an upper bioturbated unit. Radiocarbon dates on foraminifers and...... molluscs constrain 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...

  6. 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...

  7. Unsaturated zone transport modeling of the Greater Confinement Disposal Site

    International Nuclear Information System (INIS)

    Unsaturated zone transport modeling is being conducted as part of the performance assessment of the Greater Confinement Disposal (GCD) facility which is located on the Nevada Test Site. This performance assessment is based on an iterative process of modeling and data collection to assess the likelihood the site will meet the US Environmental Protection Agency's containment, individual protection and groundwater protection requirements for the disposal of transuranic wastes, high-level wastes and spent fuel. The current iteration of the performance assessment evaluates the potential impact of future events on the transport system. The future events included in this analysis are subsidence, bioturbation, erosion, climate change, irrigated farming and drilling. This paper presents the unsaturated transport model, how it fits into the performance assessment and how the future events are incorporated in the model

  8. 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.

  9. The anaerobic degradation of organic matter in Danish coastal sediments: iron reduction, manganese reduction, and sulfate reduction

    DEFF Research Database (Denmark)

    Canfield, Donald Eugene; Thamdrup, B; Hansen, Jens Würgler

    1993-01-01

    We used a combination of porewater and solid phase analysis, as well as a series of sediment incubations, to quantify organic carbon oxidation by dissimilatory Fe reduction, Mn reduction, and sulfate reduction, in sediments from the Skagerrak (located off the northeast coast of Jutland, Denmark......). In the deep portion of the basin, surface Mn enrichments reached 3.5 wt%, and Mn reduction was the only important anaerobic carbon oxidation process in the upper 10 cm of the sediment. In the less Mn-rich sediments from intermediate depths in the basin, Fe reduction ranged from somewhat less, to far......, encouraged by bioturbation. Recycling was so rapid that the residence time of Fe and Mn oxides, with respect to reduction, ranged from 70-250 days. These results require that, on average, an atom of Fe or Mn is oxidized and reduced between 100-300 times before ultimate burial into the sediment. We observed...

  10. Assessment of benthic disturbance associated with stingray foraging for ghost shrimp by aerial survey over an intertidal sandflat

    Science.gov (United States)

    Takeuchi, Seiji; Tamaki, Akio

    2014-08-01

    One notable type of bioturbation in marine soft sediments involves the excavation of large pits and displacement of sediment associated with predator foraging for infaunal benthos. Batoids are among the most powerful excavators, yet their impact on sediment has been poorly studied. For expansive tidal flats, only relatively small proportions of the habitat can be sampled due to physical and logistical constraints. The knowledge of the dynamics of these habitats, including the spatial and temporal distribution of ray bioturbation, thus remains limited. We combined the use of aerial photogrammetry and in situ benthic sampling to quantify stingray feeding pits in Tomioka Bay, Amakusa, Japan. Specifically, we mapped newly-formed pits over an 11-ha section of an intertidal sandflat over two consecutive daytime low tides. Pit size and distribution patterns were assumed to scale with fish size and reflect size-specific feeding behaviors, respectively. In situ benthic surveys were conducted for sandflat-surface elevation and prey density (callianassid shrimp). The volume versus area relationship was established as a logistic function for pits of varying sizes by photographing and refilling them with sediment. This relationship was applied to the area of every pit detected by air to estimate volume, in which special attention was paid to ray ontogenetic change in space utilization patterns. In total, 18,103 new pits were formed per day, with a mean individual area of 1060 cm2. The pits were divided into six groups (G1 to G6 in increasing areas), with abundances of G1, G2+G3, and G4-G6 being medium, high, and low, respectively. Statistical analyses using generalized linear models revealed a marked preference for the higher prey-density areas in G1 and the restriction of feeding grounds of G4-G6 to the lower shore, with G2+G3 being generalists for prey density and sandflat elevation. The lower degrees of overall bioturbation by G1 and G4-G6 were spatially structured for the

  11. Trace fossils assemblage and depositional environment of Turonian calcareous sandstones in the southern Benue Trough, Nigeria

    Science.gov (United States)

    Akpan, Etie B.; Nyong, Eyo E.

    A calcareous sandstone sequence that forms part of the Eze-Aku Formation (Reyment) features an assemblage of ichnofossils in a section exposed on a quarry face. The traces encountered include horizontal burrows, some of which are preserved as casts, lined with organic matter and belonging to the ichnogenera Gyrolithes, Pholeus and Arthrophycus. Three other types of trace fossils are described as horizontal crawling trails, flat impressions and cylindrical shafts without formal names. Gyrolithes are by far the dominant traces in this sequence. The degree of bioturbation is high in every horizon. Body fossils are very rare except for scattered occurrence of fragments of calcitic pelecypod shells. Ichnological and lithological considerations suggest that the sediments were deposited in an aerated shallow shelf environment which supported an assemblage of decapods, worms and other shallow water marine benthos. Deposition was generally below wave base under a continuous but relatively slow rate of sedimentation.

  12. Distribution of radioactivity in the Esk Estuary and its relationship to sedimentary processes

    International Nuclear Information System (INIS)

    In the Esk Estuary, Cumbria, the distribution of sediment lithology and facies has been determined and related to radionuclide surface and sub-surface distribution. The total volume of sediment contaminated with artificial radionuclides is estimated at 1.2 Mm3 and the inventory of 137Cs at 4.5 TBq. The fine grained sediments of the bank facies are the main reservoir for radionuclides, comprising 73% of the 137Cs inventory. Time scales for the reworking of these sediments are estimated at tens to hundreds of years. Measurements of sediment and radionuclide deposition demonstrate that direct sediment deposition is the main method for radionuclide recruitment to the deposits but solution labelling can also occur. Bioturbation and other diagenetic processes modify the distribution of radionuclides in the deposits. Gamma dose rates in air can be related to the sediment grain size and sedimentation rate. (Author)

  13. Diagenesis of silica-rich mounded chalk, the Coniacian Arnager Limestone, Denmark

    DEFF Research Database (Denmark)

    Buus Madsen, Heine; Stemmerik, Lars; Surlyk, Finn

    precipitation of opal-CT. The opal-CT formed at temperatures around 17°C, the precipitation lowered the silica activity and the Si/Al ratio of the pore water, resulting in precipitation of clinoptilolite, feldspar and smectite. Calcite formed synchronouslywith the latest clinoptilolite.Minoramounts of quartz...... precipitated in pore water with low silica activity during maximum burial, probably to depths of 200-250 m. The dissolution of sponge spicules and decomposition of the sponge tissue also resulted in the release of Ba2+, Sr2+,Mg2+, Ca2+ and CO3 2-, facilitating precipitation of barite and dolomite...... consist of twomicrofacies, spiculiticwackestone and bioturbated spiculitic wackestone, containing 10-22% and 7-12% moulds after spicules, respectively. Subsequent to deposition and shallow burial, dissolution of siliceous sponge spicules increased the silica activity of the pore water and initiated...

  14. 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

  15. 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.

  16. Nereis diversicolor and copper contamination effect on the erosion of cohesive sediments: A flume experiment

    Science.gov (United States)

    Fernandes, S.; Sobral, P.; Alcântara, F.

    2009-04-01

    The effect of bioturbation on the erodability of natural and manipulated copper spiked sediments (3 μmol Cu g -1 dw) was investigated using sediments collected in the Tagus estuary and Nereis diversicolor (900 ind m -2). The input of particulate matter and Cu into the water column as a result of erosion was quantified in an annular flume at 7 shear velocities (1-13 cm s -1). The biogeochemical characteristics of the sediment were analysed in depth down to 8 cm. Cu contamination elicited lower levels of eroded matter and lower shear strength profiles. Eroded matter and sediment shear strength values were higher (up to 1.7 kg m -2) in the presence of N. diversicolor, whose effect was less pronounced under contamination. Sediment erodability was not only related to hydrodynamics but was highly affected by the biogeochemical characteristics and contamination of the sediments.

  17. Freshwater springs on intertidal sand flats cause a switch in dominance among polychaete worms

    Science.gov (United States)

    Zipperle, Andreas; Reise, Karsten

    2005-08-01

    Effects of freshwater seepage on benthic macrofauna were investigated on the sandy tidal flats near the island of Sylt (German Wadden Sea) in 2002. Several permanent seepage areas (50 to 200 m offshore; up to 200 m 2 in area) were examined, in which salinity ranged from 22-29 outside to 0-16 psu inside seepage areas in the upper 20 cm of sediment during summer low tides. The freshwater seepage areas were characterised by an absence of lugworms ( Arenicola marina) and a twelve-fold increase in nereid polychaetes ( Nereis diversicolor and N. virens) relative to non-seepage areas. Lugworms and ragworms were scarce in a transition zone, which was colonised by juvenile lugworms. We suggest that nereid polychaetes avoid competition with bioturbating lugworms by adapting to areas of low salinity (freshwater seepage).

  18. 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.

  19. Distributions of transuranium nuclides in sediment and biota of the North Atlantic Ocean

    International Nuclear Information System (INIS)

    The effects of the interaction of marine sediments with their biotic population on the penetration, redistribution, sediment association and biotic availability of delivered transuranium nuclides are discussed as a function of both sedimentation regimes and in-fauna populations. Data on the penetration and redistribution patterns of fall-out transuranium nuclides in the shallow sediments of Buzzards Bay, Massachusetts, are discussed in terms of the known parameters of sedimentation and 'in sediment' biological activity. In this (and most common) type of sedimentation regime, translocation of bioturbationally downmixed transuranium nuclides back toward (and probable loss from) the sediment surface is demonstrated. Various biological and biochemical mechanisms are advanced that may act on these nuclides within sediments. The increased availability to marine biota of sediment transuranium nuclides by these remobilization processes, is indicated by data showing accumulations of these nuclides in marine invertebrates and fish. (author)

  20. Distributions of transuranium nuclides in sediments and biota of the North Atlantic Ocean

    International Nuclear Information System (INIS)

    The effects of the interaction of marine sediments with their biotic population on the penetration, redistribution, sediment association and biotic availability of delivered transuranium nuclides are discussed as a function of both sedimentation regimes and in-fauna populations. Data on the penetration and redistribution patterns of fallout transuranium nuclides in the shallow sediments of Buzzards Bay, Massachusetts, are discussed in terms of the known parameters of sedimentation and in sediment biological activity. In this (and most common) type of sedimentation regime, translocation of bioturbationally downmixed transuranium nuclides back toward (and probable loss from) the sediment surface is demonstrated. Various biological and biochemical mechanisms are advanced that may act on these nuclides within sediments. The increased availability to marine biota of sediment transuranium nuclides by these remobilization processes is indicated by data showing accumulations of these nuclides in marine invertebrates and fish. Data are included on the distribution of 239Pu, 240Pu, 241Am, 137Cs, and 55Fe in the samples

  1. 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)

  2. Mesoscale variability of vertical profiles of environmental radionuclides (40K, 226Ra, 210Pb and 137Cs) in temperate forest soils in Germany

    International Nuclear Information System (INIS)

    Vertical profiles of environmental radionuclides (40K, 226Ra, 210Pb and 137Cs) were investigated in several temperate forest soils in Germany to estimate heterogeneity of the soil horizon of interest. Absolute values of the activity concentrations of these nuclides varied to a large extent depending on the properties of individual forests as well as local geology. Several trends were generally observed independent of the location: (1) Activity concentrations of 40K increased with increasing soil density reflecting that most potassium is contained in mineral components of the soil. The variations in the 40K activity with depth may relate to biological activities in subsoil, such as root uptake of the nutrients. (2) Profiles of 226Ra with depth could be an indicator for evaluating soil heterogeneity within a horizon of interest. They are also useful to estimate anthropogenic 210Pb (210Pbexc) derived from the atmosphere via dry fallout or wet deposition. In several forests, there appeared surface enrichment of 210Pb down to a depth of approximately 10 cm, in which the 210Pb would have come from the atmosphere by combustion of fossil fuels. (3) Depth profiles of 137Cs were roughly divided into three types in which (a) the activity concentration decreased exponentially with soil depth, (b) small amounts of 137Cs existed only in the upper-most layer of the soil (0-5 cm) and (c) 137Cs disappeared at certain depths and appeared again at deeper portions of the soil. Consequences of bioturbation could be deduced from variability in vertical profiles of the environmental radionuclides. It is probable that a site showing an exponential decrease of the 137Cs activity with depth and also having a surface enrichment of 210Pb is not significantly influenced by bioturbation

  3. Examination of abyssal sea floor and near-bottom water mixing processes using Ra-226 and Rn-222

    International Nuclear Information System (INIS)

    Since Broecker's (1965) original work, extensive studies have been made on abyssal near-bottom water-mixing processes using the radioactive parent-daughter pair radium-226 (Ra) - radon-222 (Rn). One assumption critical to all of these studies is that sediments immediately under a given water column are the source of excess radon (=Rn concentration - Ra concentration) found in bottom waters. Since 1965 theoretical works of increasing complexity have tried to explain areal variations of excess radon and radium. However, Key et al. (1979b) have reported the only extensive measurements of radium and radon in bottom water and sediments at the same location. This dissertation is an expansion of that work both in theory and in scope. A diagenetic sediment model based on the work of Schink and Guinasso (1978), Cochran (1979), and Key et al. (1979b) was developed to model Ra-Rn in near-surface abyssal sediments. In order to maximize model application information, the degrees of freedom were minimized by measuring as many of the model parameters as possible. The most glaring discrepancy found was that measured near-surface total radium profiles could not be fit using plutonium-derived bioturbation rates. There is an implication that plutonium profiles modeled with currently accepted bioturbation models do not give a true indication of the real biologically induced mixing process. After adjusting for this problem in the source function, diagenetic theory explains near-surface radon-distributions adequately. Using both the adjusted diagenetic model and the empirical model developed by Key et al. (1979b), reasonable agreement was found between the sedimentary radon deficit and near-bottom water surplus. Inadequacy of present diagenetic theory makes any attempt to differentiate sedimentary radium sources academic

  4. 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.

  5. Geomorphological implications of engineering bed sediments by lotic animals

    Science.gov (United States)

    Statzner, Bernhard

    2012-07-01

    Recent developments in zoogeomorphology in combination with the increasing interest of ecologists in ecosystem engineering by organisms initiated considerable research on the impact of running water (i.e., lotic) animals (and other organisms) on fluvial bed sediments and the transport of solids. This research provided multiple evidence from field and laboratory observations and experiments that many species among mammals, amphibians, fish, insects, crustaceans, mollusks, and worms engineer bed sediments of running waters with diverse mechanistic "tools", thereby perturbing or consolidating the sediments in many types of running waters across continents, seasons, habitat types, particle sizes, and discharge levels (baseflow vs. flood). Furthermore, many animals modify the bed-sediment engineering by plants (algae, larger macrophytes, riparian vegetation). Modeling effects of bioturbating lotic animals across species and relatively simple environmental conditions (in mesocosms) provided highly significant results (P-range: interact non-linearly in a patchy pattern in small parts of real river beds, where baseflow bed-sediment engineering by lotic animals prevents or fosters mass erosion during subsequent floods. Despite these complications, these problems must be solved, as bioturbators such as crayfish and bioconsolidators such as silk-spinning caddisflies may locally modify (i) rates of transport of fluvial sediments over three orders of magnitude and (ii) frequencies of mass transport events over five orders of magnitude. The fastest way to identify promising subsequent research routes in this field would be through a variety of abundance manipulations of lotic organisms (animals and plants having different mechanistic sediment-engineering abilities) in real rivers in combination with a simple approach to assess the critical shear stress in situ for varying types of sediments. This would require joint research by fluvial geomorphologists, hydrologists, and

  6. 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).

  7. 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.

  8. 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

  9. 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.

  10. Recent aquatic ecosystem response to environmental events revealed from 210Pb sediment profiles

    International Nuclear Information System (INIS)

    The 210Pb dating method was first introduced by , and since then has been applied to study sediment from lakes, estuaries and coastal marine environments. Hundreds of studies around the world have used 210Pb as a geochronological tool in aquatic ecosystems. However little attention has been paid to the potential of this naturally occurring isotope as an environmental tracer of ecological events. Here we report three instances in which 210Pb profiles measured on undisturbed sediment cores from lakes, rivers and fjords show us the potential of 210Pb profile as a tracer of natural and anthropogenic processes. The methodology used here is a suite of techniques combining biogeochemistry (micro-electrodes), paleomagnetism (susceptibility), sediment characteristics (LOI) and visualization (SPI and X-ray) applied to the interpretation of 210Pb profiles. We measured 210Pb profiles on sediments from a river, Cruces River (Chile), which recorded a clear shift in the water chemistry caused by a pulp mill effluent to the river. Here metal mobilization and remobilization of the tracer may be the cause of the observed profile. We also measured 210Pb profiles in sediment from two fjords of Southern Chile (Pillan and Renihue), the sudden deposition change of fresh 210Pb with depth observed could very well be the result of bioturbation but it occurred in a seafloor area deprived of bioturbators. In this case, 210Pb recorded the onset of aquaculture activities (fish farming) that took place two decades ago. Finally, 210Pb profiles measured in two lakes in the 'pampa Argentina': Epecuen and Venado showed a particular shape with depth. These profiles apparently registered a sudden depositional event with recent 210Pb material, probably related to strong shifts in precipitation and drought cycles in that part of the world. These three examples show that 210Pb profiles provide valuable information not only on geochronology, but also related to natural and anthropogenic short term

  11. 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.

  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. 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

  14. 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

  15. 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.

  16. Sedimentary fabrics of the macrotidal, mud-dominated, inner estuary to fluvio-tidal transition zone, Petitcodiac River estuary, New Brunswick, Canada

    Science.gov (United States)

    Shchepetkina, Alina; Gingras, Murray K.; Zonneveld, John-Paul; Pemberton, S. George

    2016-03-01

    The study provides a detailed description of mud-dominated sedimentary fabrics and their application for the rock record within the inner estuary to the fluvial zone of the Petitcodiac River estuary, New Brunswick, Canada. Sedimentological characteristics and facies distributions of the clay- and silt-rich deposits are reported. The inner estuary is characterized by thick accumulations of interbedded silt and silty clay on intertidal banks that flank the tidally influenced channel. The most common sedimentary structures observed are parallel and wavy lamination, small-scale soft-sediment deformation with microfaults, and clay and silt current ripples. The tidal channel contains sandy silt and clayey silt with planar lamination, massive and convolute bedding. The fluvio-tidal transition zone is represented by interbedded trough cross-stratified sand and gravel beds with planar laminated to massive silty mud. The riverine, non-tidal reach of the estuary is characterized by massive, planar tabular and trough cross-stratified gravel-bed deposits. The absence of bioturbation within the inner estuary to the fluvio-tidal transition zone can be explained by the following factors: low water salinities (0-5 ppt), amplified tide and current speeds, and high concentrations of flocculated material in the water body. Notably, downstream in the middle and outer estuary, bioturbation is seasonally pervasive: in those locales the sedimentary conditions are similar, but salinity is higher. In this study, the sedimentological (i.e., grain size, bedding characters, sedimentary structures) differences between the tidal estuary and the fluvial setting are substantial, and those changes occur over only a few hundred meters. This suggests that the widely used concept of an extensive fluvio-tidal transition zone and its depositional character may not be a geographically significant component of fluvial or estuary deposits, which can go unnoticed in the study of the ancient rocks.

  17. 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

  18. 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

  19. 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

  20. 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.

  1. 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.

  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. 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

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

    Science.gov (United States)

    Granberg, Maria E; Selck, Henriette

    2007-09-01

    Sediment dwelling macrofauna (infauna) are important vectors for the transfer of sediment-associated contaminants to higher trophic levels. Sedimenting organic matter constitutes an important food source for all benthic organisms and changes seasonally in terms of quantity and quality. Sediment organic matter (SOM) quality affects organism activity and feeding behaviour, and is therefore also likely to affect contaminant fate in benthic systems. We investigated the impact of SOM quality (enrichment with either labile Tetraselmis sp. or refractory lignin) on the accumulation and metabolism 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 in both species, while pyrene metabolism remained unaffected. Metabolites comprised approximately 80% of the total tissue pyrene in N. diversicolor and approximately 40% in A. filiformis. A. filiformis arms contained one fifth of the disk pyrene concentration. Approximately 20% of the pyrene found in A. filiformis arms was found to be covalently bound to, e.g. DNA, RNA or proteins, thus reducing pyrene bioavailability to arm-cropping predators. The sedimentary pyrene distribution and metabolism was species-dependent, but correlated poorly with prevailing knowledge on species-specific bioturbation patterns. This was attributed to the comparably high biodegradability of the contaminant thus altering its sorptive characteristics and function as inert tracer. Subduction of pyrene and metabolites occurred, and the fraction of pyrene covalently bound to SOM increased with depth, thereby removing pyrene from the bioavailable pool. Our results imply that bioaccumulation and trophic transfer of sediment-associated PAH should increase following fresh organic matter input, e.g. after

  5. 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

  6. Mineralogical and geochemical influences on sediment color of Amazon wetlands analyzed by visible spectrophotometry Influências mineralógicas e geoquímicas na cor dos sedimentos das zonas úmidas da Amazônia analisada através da espectrofotometria no visível

    Directory of Open Access Journals (Sweden)

    José Tasso Felix Guimarães

    2013-09-01

    Full Text Available Based on sedimentological and geochemical data, this work relates spectrophotometric measurements with sediment composition and its application in palaeoecological studies of Amazon wetlands. The CIELAB values are directly related to mineralogical and chemical composition, mostly involving quartz, iron oxyhydroxides and sulfides (e.g. pyrite, and total organic carbon. Total organic carbon contents between 0.4-1%, 1-2%, 3-5% and 15-40% were related to L* (lightness data of 27, 26-15, 7-10 and 7 or less, respectively. The CIELAB values of a deposit in Marabá, Pará, were proportional to variations in quartz and total organic carbon contents, but changes in zones of similar color, mainly in the +a* (red and +b* (yellow values of deposits in Calçoene, Amapá and Soure, Pará, indicate a close relationship between total organic carbon content and iron oxyhydroxides and sulfides. Furthermore, the Q7/4 diagram (ratio between the % re?ectance value at 700 nm to that at 400 nm, coupled with L* indicated iron-rich sediments in the bioturbated mud facies of the Amapá deposit, bioturbated mud and bioturbated sand facies of Soure deposit, and cross-laminated sand and massive sand facies of the Marabá core. Also, organic-rich sediments were found in the bioturbated mud facies of the Amapá deposit, lenticular heterolithic and bioturbated mud facies of the Soure deposit, and laminated mud and peat facies of the Marabá deposit. At the Marabá site, the data suggest an autochthonous influence with peat formation. The coastal wetland sites at Marajó and Amapá represent the development of a typical tidal flat setting with sulfide and iron oxyhydroxides formation during alternated flooding and drying.Com base em dados sedimentológicos e geoquímicos, este trabalho relaciona medições espectrofotométricas com a composição do sedimento, e sua aplicação em estudos paleoecológicos das áreas alagáveis da Amazônia. Os dados CIELAB estão diretamente

  7. Irrigation in dose assessments models

    International Nuclear Information System (INIS)

    dominating contribution to resulting concentrations of radionuclides in vegetation due to irrigation. Finally a proposal is given how to model irrigation in future assessments by using an expression taking into account the leaf area index (LAI) and a specific storage capacity. In addition differentiation of retention on vegetation surfaces for various elements is proposed due to information in the literature. It has been stated that cations are retained more effectively than anions. Most radioecological models describe migration of radionuclides in soils by an expression including advection and bioturbation as main processes. A sensitivity and uncertainty analysis was performed for the expression used in SR 97 and SAFE to describe this. The results show, as expected, that for immobile radionuclides bioturbation causes a higher transport than advection, while for mobile radionuclides bioturbation is negligible. Irrigation is important from an exposure point of view. The importance varies due to element and consumption rates. Interception on vegetation surfaces and subsequent retention give the highest contamination for elements with low bioavailability

  8. 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

  9. 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

  10. Irrigation in dose assessments models

    Energy Technology Data Exchange (ETDEWEB)

    Bergstroem, Ulla; Barkefors, Catarina [Studsvik RadWaste AB, Nykoeping (Sweden)

    2004-05-01

    dominating contribution to resulting concentrations of radionuclides in vegetation due to irrigation. Finally a proposal is given how to model irrigation in future assessments by using an expression taking into account the leaf area index (LAI) and a specific storage capacity. In addition differentiation of retention on vegetation surfaces for various elements is proposed due to information in the literature. It has been stated that cations are retained more effectively than anions. Most radioecological models describe migration of radionuclides in soils by an expression including advection and bioturbation as main processes. A sensitivity and uncertainty analysis was performed for the expression used in SR 97 and SAFE to describe this. The results show, as expected, that for immobile radionuclides bioturbation causes a higher transport than advection, while for mobile radionuclides bioturbation is negligible. Irrigation is important from an exposure point of view. The importance varies due to element and consumption rates. Interception on vegetation surfaces and subsequent retention give the highest contamination for elements with low bioavailability.

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  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. 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

  18. 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

  19. 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

  20. Recent aquatic ecosystem response to environmental events revealed from 210Pb sediment profiles.

    Science.gov (United States)

    Mulsow, S; Piovano, E; Cordoba, F

    2009-01-01

    The (210)Pb dating method was first introduced by Goldberg (1963), and since then has been applied to study sediment from lakes, estuaries and coastal marine environments. Hundreds of studies around the world have used (210)Pb as a geochronological tool in aquatic ecosystems. However little attention has been paid to the potential of this naturally occurring isotope as an environmental tracer of ecological events. Here we report three instances in which (210)Pb profiles measured on undisturbed sediment cores from lakes, rivers and fjords show us the potential of (210)Pb profile as a tracer of natural and anthropogenic processes. The methodology used here is a suite of techniques combining biogeochemistry (micro-electrodes), paleomagnetism (susceptibility), sediment characteristics (LOI) and visualization (SPI and X-ray) applied to the interpretation of (210)Pb profiles. We measured (210)Pb profiles on sediments from a river, Cruces River (Chile), which recorded a clear shift in the water chemistry caused by a pulp mill effluent to the river. Here metal mobilization and remobilization of the tracer may be the cause of the observed profile. We also measured (210)Pb profiles in sediment from two fjords of Southern Chile (Pillan and Reñihue), the sudden deposition change of fresh (210)Pb with depth observed could very well be the result of bioturbation but it occurred in a seafloor area deprived of bioturbators. In this case, (210)Pb recorded the onset of aquaculture activities (fish farming) that took place two decades ago. Finally, (210)Pb profiles measured in two lakes in the "pampa Argentina": Epecuen and Venado showed a particular shape with depth. These profiles apparently registered a sudden depositional event with recent (210)Pb material, probably related to strong shifts in precipitation and drought cycles in that part of the world. These three examples show that (210)Pb profiles provide valuable information not only on geochronology, but also related to

  1. 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

  2. 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

  3. 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

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

    Directory of Open Access Journals (Sweden)

    H. de Moel

    2009-09-01

    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

  5. 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

  6. 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

  7. 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.

  8. 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

  9. 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)

  10. Migration of fallout radiocaesium in a grassland soil from 1986 to 2001

    International Nuclear Information System (INIS)

    The vertical migration of 134Cs, deposited by the Chernobyl fallout (1986), and 137Cs, deposited by the Chernobyl and the global fallout, in the soil of an undisturbed Bavarian grassland in Germany was investigated from 1986 to 2001. The activity-depth profiles of both isotopes at ten sampling dates were evaluated by the classical convection-dispersion equation and a random walk particle model. In both models, the apparent migration velocity v and the apparent dispersion coefficient D were assumed to be independent of time. However, optimized values of v and D were significantly different for the different locations sampled at different times. If nevertheless constant values of v and D were used, the simulated activity densities per soil layer were out of the range of the spatial variability of the observed activity densities determined in 2001. It is concluded that without further simultaneous investigations e.g. on bioturbation at the study site, migration parameters of radiocaesium determined by classical transport models based on convection and dispersion during the first years after the deposition of the activity cannot be used for predictive purposes

  11. Spongy-like porosity in peritidal carbonates: An interaction of cyclic sea-level oscillations, fresh water supply and sediment texture

    Science.gov (United States)

    Todaro, S.; Hollis, C.; Di Stefano, P.

    2016-03-01

    This paper focuses upon the analysis of a complex paleokarstic system recorded within uppermost Triassic peritidal cycles in northwestern Sicily. Besides documenting spectacular karstification at the Triassic/Jurassic boundary, it provides an example of stratabound 'spongy' or 'swiss-cheese' dissolution. On the base of field observations, microfacies analysis, transmitted-light and cathodoluminescence petrography and stable-isotope analyses we put forward an original model for the formation of this peculiar stratabound dissolution. It implies a complex interaction of several controlling factors at the interface between the marine and meteoric diagenetic realms during the relative cyclic oscillations of sea-level. The presence of a fresh water supply from an adjacent emerged area is the key for the periodic formation of a mixing water lens during the relative sea level lowstand that brought about the subaerial exposure of the platform. The resulting dissolution pattern in the subtidal unit of a specific cycle is strongly controlled by the textural features of the sediments. In the case of bioturbated wackestones the 'spongy' or 'swiss-cheese' pattern develops, while in mollusk-rich beds biomoldic porosity occurs. In well-sorted subtidal members, such as algal grainstones, the dissolution originates as randomly distributed vuggy porosity. During periodic flooding of the platform, a new subtidal unit is formed and the dissolution stops as fully marine phreatic conditions are re-established.

  12. 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

  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 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.

  15. 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.

  16. Stratigraphy and palaeoceanography of upper Masstrichtian chalks, southern Danish Central Graben

    Energy Technology Data Exchange (ETDEWEB)

    Ineson, J.R.; Buchardt, B.; Lassen, Susanne; Rasmussen, Jan A.; Schioeler, P.; Schovsbo, N.H.; Sheldon, E.; Surlyk, F. [Geological Survey of Denmark and Greenland, Copenhagen (Denmark)

    2006-07-01

    Upper Maastrichtian chalks form important hydrocarbon reservoirs in the Danish sector of the North Sea and have been intensively studied, yet their lithological uniformity can frustrate attempts to develop a high-resolution stratigraphic subdivision and a genetic understanding of the factors controlling production and sedimentation of the pelagic carbonate ooze. Recent research into these topics, by means of a multidisciplinary study involving quantitative/semiquantitative palynology, micropalaeontology (nannofossils, foraminifers) and isotope geochemistry, integrated with detailed sedimentology. Two key wells were selected, the M-1OX well from the Dan Field and the E-5X well from the Tyra SE Field, based on the extensive core coverage in these wells and on their position in the southern part of the Danish Central Graben where evidence of large-scale resedimentation (and consequent stratigraphic complexity) is uncommon within the Maastrichtian section. This study concentrated on a number of palaeoceanographic signals that can be derived from the sedimentary record. Planktonic organisms, both phytoplankton (e.g. coccolithophores, some dinoflagellates) and zooplankton (e.g. foraminifers) provide a record of conditions in the upper watermasses, largely within the photic zone, while bottom conditions are indicated by epifaunal/infaunal organisms (e.g. benthic foraminifers) and bioturbation, and by the sedimentological evidence of depositional processes at the sea floor. (LN)

  17. Benthic phosphorus and iron budgets for three NW African slope sediments: a balance approach

    Directory of Open Access Journals (Sweden)

    K. Küster-Heins

    2010-02-01

    Full Text Available Despite intensive research on the different domains of the marine phosphorus (P cycle during the last decades, frequently discussed open questions still exist especially on controlling factors for the benthic behaviour of P and its general distribution in sediment-pore water systems. Steady state or the internal balance of all relevant physical and (biogeochemical processes are amongst the key issues. In this study we present and discuss an extended data set from surface sediments recovered from three locations on the NW African continental slope. Pore water data and results from sequential sediment extractions give clear evidence to the well-known close relationship between the benthic cycles of P and iron. Accordingly, most of the dissolved phosphate must have been released by microbially catalyzed reductive dissolution of iron (oxhydroxides. However, rates of release and association of P and iron, respectively, are not directly represented in profiles of element specific sediment compositions. Results from steady-state based transport-reaction modelling suggest that particle mixing due to active bioturbation, or rather a physical net downward transport of P associated to iron (oxyhydroxides, is an essential process for the balance of the inspected benthic cycles. This study emphasizes the importance of balancing analytical data for a comprehensive understanding of all processes involved in biogeochemical cycles.

  18. 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.

  19. Sediment accumulation in San Leandro Bay, Alameda County, California, during the 20th century - A preliminary report

    International Nuclear Information System (INIS)

    Major changes made in the configuration of San Leandro Bay, Alameda County, California, during the 20th century have caused rapid sedimentation within parts of the Bay. Comparison of bathymetric surveys indicates that sedimentation in the vicinity of the San Leandro Bay channel averaged 0.7 cm/annum between 1856 and 1984. Lead-210 data collected at four shallow water sites east of the San Leandro Bay channel indicated that sedimentation rates have averaged between 0.06 and 0.28 cm/annum. Because bioturbation of bottom sediments cannot be discounted, better definition of this range in sedimentation rates would require measuring the activity of lead-210 on incoming sediments. In addition to sediment deposited in the vicinity of the San Leandro Bay channel and open, shallow areas to the east, 850,740 cu m of sediment was deposited between 1948 and 1983 in an area dredged at the mouth of San Leandro Creek. All available data indicate that between 1,213,000 and 1,364,000 cu m of sediment was deposited in San Leandro Bay between 1948 and 1983. Sediment yield data from an adjacent drainage basin, when combined with inventories of lead-210 and cesium-137, indicate that most of the sediment deposited in San Leandro Bay is coming from resuspension of bottom sediments or from erosion of marshes or shorelines of San Leandro or San Francisco Bay. 31 refs., 7 figs., 4 tabs

  20. 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)

  1. 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.

  2. 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.

  3. 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.

  4. The behaviour of certain long-lived radionuclides in the marine environment

    International Nuclear Information System (INIS)

    The research recently conducted is summarized. Methods have been developed for analysis of 99Tc, 222Rn, 226Ra, 228Ra, 210Pb, 210Po, 230Th, 234Th, U nuclides in fish tissue, different oxidation states of Pu, Am and Np. Shelf sea research, much in the Irish sea, has studied the latter elements and Tc, and provided information about distribution and speciation in water. Pu isotope ratios give information on the source (Sellafield, Cap La Hague or fallout). The possibility of memory effects in shipboard sampling systems is pointed out. At least 240TBq of sup(239,240)Pu and 290 TBq of 241Am are associated with the upper 30 cm of the seabed within a 30 km belt of the Cumbrian coast. Bioturbation has been studied using 14C, 210Pb, 234Th,Pu, Am, Cm, and redistribution down to 140 cm demonstrated. Interstitial water studies showed partial reduction of Pu and Np isotopes, and the presence of artifacts due to subsequent exposure to oxidising conditions was shown to be important, and to be avoided. Organic complexation is also being studied. Studies of biological distribution of many of the above isotopes gave quotients for principal modes of entry. Parallel laboratory experiments on uptake of sup(95m)Tc, 237Pu and 235Np by lobsters have also been carried out. Studies of radionuclide scavenging in the deep sea, relevant to waste disposal have produced a review of Ksub(d) and CF values. (author)

  5. Radioactivity in sediments of the Great Lakes: post-depositional redistribution by deposit-feeding organisms

    International Nuclear Information System (INIS)

    At two locations in southern Lake Huron (U.S.A.), twelve 35.5-cm diameter cores of fine-grained sediments were taken for comparison of the vertical distribution of 210Pb and fallout 137Cs with the distribution of benthic macroinvertebrates, mainly oligochaete worms (Tubificidae) and the amphipod, Pontoporeia affinis. Locations were selected on the basis of 210Pb distributions measured a year earlier which indicated contrasting depths of mixing of surface sediments. At one location the activity of 210Pb is uniform down to about 6 cm and 95% of total invertebrates occur within this zone; at the other location the zone of constant activity is only 3 cm deep but 90% of the invertebrates occur within it. Comparison of published tubificid defecation rates with sediment accumulation rates based on 210Pb shows that oligochaetes alone can account for mixing in one case while the effects of amphipods may be required in the case of shallower mixing. If mixing is represented as a diffusional process, eddy diffusion coefficients are at least 5.8 and 3.3 cm2 yr-1 at respective locations. In comparison with bioturbation, molecular diffusion is of minor importance in the post-depositional mobility of 137Cs. The necessity for introducing a diffusion coefficient varying continuously with depth is indicated by characteristics of the distribution of 137Cs. Biological reworking of near-surface sediments is an important process affecting radioactivity and chemical profiles in profundal deposits of this and probably other Great Lakes. (Auth.)

  6. 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

  7. 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.)

  8. 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.

  9. 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

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

    International Nuclear Information System (INIS)

    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 re workers (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. Bio geographic 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 10000 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.

  11. 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.)

  12. Demographic indicators of change in a deposit-feeding abyssal holothurian community (Station M, 4000 m)

    Science.gov (United States)

    Huffard, Christine L.; Kuhnz, Linda A.; Lemon, Larissa; Sherman, Alana D.; Smith, Kenneth L.

    2016-03-01

    Holothurians are among the most abundant benthic megafauna at abyssal depths, and important consumers and bioturbators of organic carbon on the sea floor. Significant fluctuations in abyssal holothurian density are often attributed to species-specific responses to variable particulate organic carbon flux (food supply) stemming from surface ocean events. We report changes in densities of 19 holothurian species at the abyssal monitoring site Station M in the northeast Pacific, recorded during 11 remotely operated vehicle surveys between Dec 2006 and Oct 2014. Body size demographics are presented for Abyssocucumis abyssorum, Synallactidae sp. 1, Paelopatides confundens, Elpidia sp. A, Peniagone gracilis, Peniagone papillata, Peniagone vitrea, Peniagone sp. A, Peniagone sp. 1, and Scotoplanes globosa. Densities were lower and species evenness was higher from 2006-2009 compared to 2011-2014. Food supply of freshly-settled phytodetritus was exceptionally high during this latter period. Based on relationships between median body length and density, numerous immigration and juvenile recruitment events of multiple species appeared to take place between 2011 and 2014. These patterns were dominated by elpidiids (Holothuroidea: Elasipodida: Elpidiidae), which consistently increased in density during a period of high food availability, while other groups showed inconsistent responses. We considered minimum body length to be a proxy for size at juvenile recruitment. Patterns in density clustered by this measure, which was a stronger predictor of maximum density than median and mean body length.

  13. 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.

  14. Radiocarbon

    Science.gov (United States)

    Broecker, W. S.

    2003-12-01

    Willard Libby's invention of the radiocarbon dating method revolutionized the fields of archeology and Quaternary geology because it brought into being a means to correlate events that occurred during the past 3.5×104 years on a planet-wide scale (Libby et al., 1949). This contribution was recognized with the award of the Nobel Prize for Chemistry. In addition, radiocarbon measurements have been a boon to the quantification of many processes taking place in the environment, to name a few: the rate of "ventilation" of the deep ocean, the turnover time of humus in soils, the rate of growth of cave deposits, the source of carbon-bearing atmospheric particulates, the rates of gas exchange between the atmosphere and water bodies, the replacement time of carbon atoms in human tissue, and depths of bioturbation in marine sediment. Some of these applications have been greatly aided by the creation of excess 14C atoms as the result of nuclear tests conducted in the atmosphere. Since the 1960s, this so-called bomb radiocarbon has made its way into all of the Earth's active carbon reservoirs. To date, tens of thousands of radiocarbon measurements have been made in laboratories throughout the world.

  15. Late Quaternary glacially influenced sedimentation on the north-west Irish margin: facies, sediment delivery and link to glacial history

    Science.gov (United States)

    Benetti, Sara; Sacchetti, Fabio; Georgiopoulou, Aggeliki; Cofaigh, Colm Ó.; Edwards, Robin; Toms, Lee; McCarron, Steve

    2013-04-01

    This presentation will discuss the sedimentary processes that took place since the last glaciation on the north-eastern margin of the Rockall Trough, offshore Ireland. With the use of seventeen sediment cores collected along the axes of two major canyons and across the northern Rockall Trough, changes in sedimentary processes from shelf edge to basin floor are revealed and examined. The aim is to better understand the sedimentary processes that occurred along the canyons and in the trough during the last glaciation, through the deglaciation and into the Holocene. On the basis of sedimentary structures, texture, grain size, X-radiograph character and physical properties thirteen depositional facies are recognised. These facies are interpreted in terms of depositional processes as: (1) Massive diamicton deposited as subglacial till on the continental shelf during the last glacial advance; (2) Fining upward gravels and sands, related to rise in sea level and changing of hydrographic conditions on the shelf over time; (3) Plumites deposited during deglaciation on the upper slope; (4) Widespread hemipelagites of Holocene and glacial age; (5) Heavily bioturbated, foraminiferal rich contourites of Holocene and glacial age; (6) coarse- and fine-grained turbidites deposited mainly on the lower slope and trough during the last glacial period; (7) diamicton and chaotic mud beds deposited in the trough by glaciogenic debris flows. Margin physiography, distance from the ice sheet grounding zone, style of glaciation on the shelf and strength of deep sea circulation are the main controlling factors for these depositional processes.

  16. Isotopic constraints (210Pb, 228Th) on the sedimentary dynamics of contaminated sediments from a subtropical coastal lagoon (NW Mexico)

    Science.gov (United States)

    Ruiz-Fernandez, A.; Hillaire-Marcel, C.; Ghaleb, B.; Paez-Osuna, F.; Soto-Jimenez, M.

    2001-11-01

    Six sediment push-cores were collected at a coastal lagoon system affected by urban and agriculture wastes. The sediments were analyzed for 228Th, 230Th, 232Th, 210Pb, 226Ra, and 137Cs. 137Cs activities were at background level for all samples. The 210Pbtot activities found in the area varied from 0.5 to 4.5 dpm g-1 with 210Pbsup levels ranging between 1.2-1.8 dpm g-1. Cores CHI and EPC showed flat profiles depleted of 210Pbxs, indicating the absence of recent sedimentation. Core CAI shows a flat 210Pbxs profile that seems to be bioturbated. Cores ERC and BRI show chaotic profiles with layers totally depleted in 210Pbxs, likely caused by resuspension triggered by storm conditions. High 228Th/232Th values observed at core ERC suggest that the resuspension event occurred less than 10 years ago. The contaminated sediment of the lagoon are frequently resuspended, re-oxygenated, and therefore the contaminating trace metals will continue to be easily remobilized in the food chain.

  17. Organic matter quality and supply to deep-water coral/mound systems of the NW European Continental Margin

    Science.gov (United States)

    Kiriakoulakis, K.; Freiwald, A.; Fisher, E.; Wolff, G. A.

    2007-02-01

    Comparison of five deep-water coral (DWC)/mound ecosystems along the European Continental Margin shows that suspended particulate organic matter (sPOM), a potential food source, is lipid rich and of high quality. However, there are differences between the sites. The Darwin and Pelagia Mounds (N. Rockall Trough and N. Porcupine Bank, respectively) have higher proportions of labile particulate lipids (including high proportions of polyunsaturated fatty acids) in the benthic boundary layer than Logachev, Hovland and Belgica Mounds (Rockall Bank, S. Porcupine Bank and Porcupine Seabight, respectively). The high quality sPOM could be transported downslope from the euphotic zone. There is some evidence for inter-annual variability at some sites (e.g. Hovland and Logachev Mounds) as large differences in suspended lipid and particulate organic carbon concentrations were observed over the sampling period. Elevated total organic carbon contents of sediments at mound sites, relative to control sites in some cases (particularly Darwin Mounds), probably reflect local hydrodynamic control and the trapping of sPOM by the DWC. Fresh POM can be relatively rapidly transferred to significant depth (up to 8 cm) through bioturbation that is evident at all sites. There is no clear evidence of present day hydrocarbon seepage at any of the sites.

  18. 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.

  19. 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.

  20. 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.

  1. Biogeochemical cycling in an organic-rich coastal marine basin. 7. Sulfur mass balance, oxygen uptake and sulfide retention

    Science.gov (United States)

    Chanton, J.P.; Martens, C.S.; Goldhaber, M.B.

    1987-01-01

    Sulfur and oxygen fluxes were quantified in the seasonally varying anoxic marine sedimentary system of Cape Lookout Bight, N.C., U.S.A. Over the three year study period, 1981-1983, the mean annual sulfate reduction rate was determined to be 18.2 ?? 1.6 moles ?? m-2 ?? y-1. This value, added to the estimate of the detrital sulfur input of 1.2 ?? 4.4 gave a total sulfur input of 19.4 ?? 4.7 moles ?? m-2 ?? y-1. The sulfide flux to the sediment-water interface, measured in anaerobic benthic chambers was 4.6 ?? 0.5 moles ?? m-2 ?? y-1, and represented 37% of the annual oxygen uptake rate of 25.2 ?? 2.8 moles ?? m-2 ?? y-1. The sulfide burial rate, determined to be 15.5 ?? 3.1 moles ?? m-2 ?? y-1, was within 5% of the value predicted by summing the fluxes at the sediment-water interface. The C S weight ratio of sediment below the depth of diagenetic reaction was determined to be 2.75. The sulfide retention rate in these rapidly accumulating sediments (10 cm/yr) was 77 ?? 19%. Comparison of this result with previous studies shows that rapid sediment accumulation and the lack of bioturbation control this unusually high degree of sulfide retention. ?? 1987.

  2. The biomechanics of burrowing and boring.

    Science.gov (United States)

    Dorgan, Kelly M

    2015-01-15

    Burrowers and borers are ecosystem engineers that alter their physical environments through bioturbation, bioirrigation and bioerosion. The mechanisms of moving through solid substrata by burrowing or boring depend on the mechanical properties of the medium and the size and morphology of the organism. For burrowing animals, mud differs mechanically from sand; in mud, sediment grains are suspended in an organic matrix that fails by fracture. Macrofauna extend burrows through this elastic mud by fracture. Sand is granular and non-cohesive, enabling grains to more easily move relative to each other, and macrofaunal burrowers use fluidization or plastic rearrangement of grains. In both sand and mud, peristaltic movements apply normal forces and reduce shear. Excavation and localized grain compaction are mechanisms that plastically deform sediments and are effective in both mud and sand, with bulk excavation being used by larger organisms and localized compaction by smaller organisms. Mechanical boring of hard substrata is an extreme form of excavation in which no compaction of burrow walls occurs and grains are abraded with rigid, hard structures. Chemical boring involves secretion to dissolve or soften generally carbonate substrata. Despite substantial differences in the mechanics of the media, similar burrowing behaviors are effective in mud and sand. PMID:25609781

  3. In situ tensile fracture toughness of surficial cohesive marine sediments

    Science.gov (United States)

    Johnson, Bruce D.; Barry, Mark A.; Boudreau, Bernard P.; Jumars, Peter A.; Dorgan, Kelly M.

    2012-02-01

    This study reports the first in situ measurements of tensile fracture toughness, K IC, of soft, surficial, cohesive marine sediments. A newly developed probe continuously measures the stress required to cause tensile failure in sediments to depths of up to 1 m. Probe measurements are in agreement with standard laboratory methods of K IC measurements in both potter's clay and natural sediments. The data comprise in situ depth profiles from three field sites in Nova Scotia, Canada. Measured K IC at two muddy sites (median grain size of 23-50 μm) range from near zero at the sediment surface to >1,800 Pa m1/2 at 0.2 m depth. These profiles also appear to identify the bioturbated/mixed depth. K IC for a sandy site (>90% sand) is an order of magnitude lower than for the muddy sediments, and reflects the lack of cohesion/adhesion. A comparison of K IC, median grain size, and porosity in muddy sediments indicates that consolidation increases fracture strength, whereas inclusion of sand causes weakening; thus, sand-bearing layers can be easily identified in K IC profiles. K IC and vane-measured shear strength correlate strongly, which suggests that the vane measurements should perhaps be interpreted as shear fracture toughness, rather than shear strength. Comparison of in situ probe-measured values with K IC of soils and gelatin shows that sediments have a K IC range intermediate between denser compacted soils and softer, elastic gelatin.

  4. 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.

  5. 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.

  6. 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.

  7. Lithostratigraphy and depositional environments of the Pyeongan Supergroup (Carboniferous Permian) in the Taebaek area, mid-east Korea

    Science.gov (United States)

    Lee, H. S.; Chough, S. K.

    2006-03-01

    The Pyeongan Supergroup (Carboniferous-Permian) consists of a thick siliciclastic sequence (1700 m thick). Recent sedimentological work in the Taebaek area has refined the lithostratigraphic units: Manhang, Geumcheon-Jangseong, Hambaeksan, Dosagok, Gohan and Donggo formations in ascending order. The entire sequence is represented by thirteen sedimentary facies, which can be organized into seven facies associations (FA). The lower part of the Manhang Formation (FA 1) (Moscovian) consists of crudely cross-stratified conglomerate, massive sandstone and gray homogeneous siltstone, formed in shoreface off river mouth, whereas purple siltstone and grainstone of the upper part (FA 2) probably formed in a coastal plain environment. The Geumcheon-Jangseong Formation (Moscovian-Artinskian) consists of dark gray sandstone, dark gray shale, coal and bioturbated wackestone (FA 3) formed in a lagoonal environment. The Hambaeksan Formation (Kungurian) comprises milky white, crudely stratified, conglomerate, gray coarse sandstone and partly laminated black shale (FA 4), representing a shoreface progradation. The Dosagok Formation (Late Permian) is characterized by an alternation of purple fine sandstone and conglomerate (FA 5), formed in a bedload-dominated fluvial system. The Gohan Formation (Late Permian) is mostly composed of upward-fining units (massive sandstone to dark gray siltstone) (FA 6), suggesting a restricted inter-distributary bay environment. The Donggo Formation (?Late Permian) consists of cross-stratified coarse sandstone and purple sandstone (FA 7), interpreted as deposits of perennial, sandy braided river system.

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. 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

  13. 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

  14. Species composition of a soil invertebrate multi-species test system determines the level of ecotoxicity

    International Nuclear Information System (INIS)

    A soil multi-species, SMS, experimental test system consisting of the natural microbial community, five collembolan species and a predatory mite along with either Enchytraeus crypticus or the earthworm Eisenia fetida were exposed to α-cypermethrin. A comparison of the performance of these two types of SMSs is given to aid the development of a standard test system. E. fetida had a positive effect on the majority of the species, reducing the negative insecticide effect. E. fetida affected the species sensitivity and decreased the degradation of the insecticide due to the organic matter incorporation of earthworm food. After 8 weeks, the EC50 was 0.76 mg kg−1 for enchytraeids and ranged between 2.7 and 18.9 mg kg−1 for collembolans, more sensitive than previously observed with single species. Changes observed in the community structure and function illustrates the strength of a multi-species test system as an ecotoxicological tool compared to single species tests. -- Highlights: • Degradation of alpha-cypermethrin was faster with enchytraeids than with earthworms. • Lumbricid castings and bioturbation explains bioavailability of α-cypermethrin. • Pesticide effects on soil arthropods alter with the community composition. • Multispecies test systems are feasible with either an enchytraeid or a lumbricid. • Collembolans are more sensitive to cypermethrin with enchytraeids than with earthworms. -- Soil ecotoxicological fate and effects in multispecies test systems are affected by earthworm activity

  15. 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.

  16. Ecogeochemical fate of coarse organic particles in sediments of the Rhône River prodelta

    Science.gov (United States)

    Charles, François; Coston-Guarini, Jennifer; Lantoine, François; Guarini, Jean-Marc; Yücel, Mustafa

    2014-03-01

    Coarse particulate organic matter (CPOM) represents a small portion of the inner shelf sediments but occurs across all river outlets. To consider the ecogeochemical fate of CPOM in such an environment, we examined both the infauna community and secondary evidence of geochemical reactions preserved in the surface sediments of the Rhône prodelta. ICP-AES, scanning electron microscopy and energy dispersive X-ray spectrometry of the CPOM showed that the fate of organic matter in this environment is driven by sulphate reduction and geochemical reactions resulting from the precipitation of sulfide due to the presence of large amounts of iron-bearing minerals. Leaf litter debris contained such high quantities of iron that after dry ashing the remaining material is easily attracted by a magnet. The observed geochemical trade-off was proposed as a mechanism that helps to maintain a bioturbating animal community that in turn contributes to the mineralization of organic matter within this suboxic environment. This study showed that the accumulation of refractory organic carbon in sediments was intimately associated with the sequestering of iron and sulphur by providing a nucleation point for mineral deposition and also that the extent of decomposition of the organic materials did not necessarily increase progressively from coarser to finer particles.

  17. The role of Callianassa subterranea (Montagu) (THALASSINIDEA) in sediment resuspension in the North Sea

    Science.gov (United States)

    Rowden, A. A.; Jones, M. B.; Morris, A. W.

    1998-09-01

    The mud shrimp Callianassa subterranea (Montagu) is a common member of the macrobenthic community at the site in the North Sea selected to study the dynamics of suspended sediment behaviour. The extensive burrowing habit of this deposit-feeding species makes it an important contributor to the degree of bioturbation experienced at the site. Individuals recovered from the site were returned to the laboratory to investigate the influence of body size and temperature upon the amount of sediment expelled. A clear relationship between these variables and the quantity of expelled sediment was identified, and a well-defined temporal pattern of expulsion activity and inactivity was demonstrated. These experimental data, together with field information on seawater temperatures and aspects of mud shrimp population dynamics, allow the construction of an estimated annual sediment turnover budget of 11 kg (dry weight) m -2 yr -1. Field observations at the North Sea site show that the sediment expelled by the mud shrimp forms unconsolidated volcano-like mounds, which significantly modify seabed surface topography. The dimensions of these surface features were measured from bottom photographs of the site and used to determine values of boundary roughness length ( Zo). In January Zo was 0.0007 cm, whilst in September Zo equaled 0.79 cm. Callianassa subterranea's maximum contribution to resuspension was assessed by calculating a derived lateral sediment transport rate of 7 kg m -1 month -1 (from values of near-bed current velocity, modified boundary roughness length and sediment turnover rate).

  18. High resolution paleo-geomagnetic field variations as recorded in sediments from Prince William Sound, Alaska

    Science.gov (United States)

    Ziegler, Leah; Stoner, Joseph

    2013-04-01

    The dynamic changes in the Earth's magnetic field, caused by fluid motions in its outer core, can be captured in global marine sediments. Here we extend recent efforts to reconstruct Holocene paleomagnetic secular variation and environmental conditions in the mid-high latitude North Pacific with analyses of a marine sediment core taken from Prince William Sound, southern Alaska. Natural and laboratory remanent magnetizations were studied by progressive alternating field (AF) demagnetization of u-channel samples from jumbo piston core EW0408-95JC (60.66278N, 147.70847W, water depth 745m). The lithology is monitored by physical properties measurements, including CT Scans and core descriptions. The lithology of the upper 8.5 m of the 17.6 meter core consists primarily of magnetically homogenous bioturbated muds. Component directions calculated by PCA analysis are characterized by low MAD values (spatial scale of signal coherence at centennial resolution . The resulting record of paleosecular variation (PSV) and relative paleointensity are consistent with predictions from global geomagnetic field models, yet allow investigations of rates of change of the local field, that cannot be accessed from global field models.

  19. 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.

  20. Quantitative determination of microbial activity and community nutritional status in estuarine sediments: evidence for a disturbance artifact

    Science.gov (United States)

    Findlay, R. H.; Pollard, P. C.; Moriarty, D. J.; White, D. C.

    1985-01-01

    In estuarine sediments with a high degree of vertical heterogeneity in reduced substrate and terminal electron acceptor concentrations, the method of exposure of the microbiota to labeled substrates can introduce a "disturbance artifact" into measures of metabolic activity. The detection of this artifact is based on quantitative measurement of the relative rates of incorporation of [14C]acetate into phospholipid fatty acids (PLFA) and endogenous storage lipid, poly-beta-hydroxyalkanoate (PHA). Previous studies have shown that PLFA synthesis measures cellular growth and that PHA synthesis measures carbon accumulation (unbalanced growth). The "disturbance artifact" of exposure to [14C]acetate was demonstrated by comparing injection of a core with the usual or pore-water replacement or slurry techniques. Only injection of labeled substrate allowed detection of preassay disturbance of the sediment with a garden rake. The raking increased PLFA synthesis with little effect to differences in concentration or distribution of [14C]acetate in the 10-min incubation. Bioturbation induced by sand dollar feeding in estuarine sediment could be detected in an increased PLFA/PHA ratio which was due to decreased PHA synthesis if the addition of labeled substrate was by the injection technique. Addition of labeled precursors to sediment by slurry or pore-water replacement induces greater disturbance artifacts than injection techniques.

  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. Empirical evidence reveals seasonally dependent reduction in nitrification in coastal sediments subjected to near future ocean acidification.

    Science.gov (United States)

    Braeckman, Ulrike; Van Colen, Carl; Guilini, Katja; Van Gansbeke, Dirk; Soetaert, Karline; Vincx, Magda; Vanaverbeke, Jan

    2014-01-01

    Research so far has provided little evidence that benthic biogeochemical cycling is affected by ocean acidification under realistic climate change scenarios. We measured nutrient exchange and sediment community oxygen consumption (SCOC) rates to estimate nitrification in natural coastal permeable and fine sandy sediments under pre-phytoplankton bloom and bloom conditions. Ocean acidification, as mimicked in the laboratory by a realistic pH decrease of 0.3, significantly reduced SCOC on average by 60% and benthic nitrification rates on average by 94% in both sediment types in February (pre-bloom period), but not in April (bloom period). No changes in macrofauna functional community (density, structural and functional diversity) were observed between ambient and acidified conditions, suggesting that changes in benthic biogeochemical cycling were predominantly mediated by changes in the activity of the microbial community during the short-term incubations (14 days), rather than by changes in engineering effects of bioturbating and bio-irrigating macrofauna. As benthic nitrification makes up the gross of ocean nitrification, a slowdown of this nitrogen cycling pathway in both permeable and fine sediments in winter, could therefore have global impacts on coupled nitrification-denitrification and hence eventually on pelagic nutrient availability. PMID:25329898

  3. Seasonal and topographic variations in porewaters of a southeastern USA salt marsh as revealed by voltammetric profiling†

    Directory of Open Access Journals (Sweden)

    Taillefert Martial

    2001-11-01

    Full Text Available We report electrochemical profiles from unvegetated surficial sediments of a Georgia salt marsh. In creek bank sediments, the absence of ΣH2S or FeSaq and the presence of Fe(III–organic complexes suggest that Mn and Fe reduction dominates over at least the top ca. 5 cm of the sediment column, consistent with other recent results. In unvegetated flats, accumulation of ΣH2S indicates that SO42- reduction dominates over the same depth. A summer release of dissolved organic species from the dominant tall form Spartina alterniflora, together with elevated temperatures, appears to result in increased SO42- reduction intensity and hence high summer concentrations of ΣH2S in flat sediments. However, increased bioturbation and/or bioirrigation seem to prevent this from happening in bank sediments. Studies of biogeochemical processes in salt marshes need to take such spatial and temporal variations into account if we are to develop a good understanding of these highly productive ecosystems. Furthermore, multidimensional analyses are necessary to obtain adequate quantitative pictures of such heterogeneous sediments.

  4. 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.)

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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).

  12. 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.

  13. Influence of biological activity on sorption by using 65Zn and 109Cd into mangrove sediment

    International Nuclear Information System (INIS)

    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 65Zn and 109Cd 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 65Zn and 109Cd 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)

  14. 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

  15. The influence of Brachyura on oil polluted subtropical intertidal shores - an example from the Arabian Gulf; Die Bedeutung von Krabben (Brachyura) bei der Regeneration von kohlenwasserstoffkontaminierten subtropischen Flachkuesten am Beispiel des Arabisch Persischen Golfs

    Energy Technology Data Exchange (ETDEWEB)

    Barth, H.J. [Geographisches Inst., Univ. Heidelberg (Germany)

    2006-11-15

    Objectives. The second Gulf War (1991) led to the largest oil spill in human history. Over 770 km of coastline from southern Kuwait to Abu Ali Island (Saudi Arabia) were smothered with oil and tar, erasing most of the local plant and animal communities. This long term study was designed to reveal the processes of natural regeneration within the salt marsh ecosystems as well as the processes counter productive to regeneration. Methods. Field data were collected along permanent transect lines during annual visits from 1994 to 2004. Soil analysis included grain size, carbonate, pH and total hydrocarbon (Soxhlet extraction). Heavy metals were determined by Inductively Coupled Plasma Atomic Emission Spectroscopy. Hydrocarbons were analysed by High Performance Liquid Chromatography. Results. The dominant processes of regeneration are characterized by four types of indicators. These are (1) the composition of hydrocarbon compounds remaining in the soil, (2) the hardness of the soil surface, (3) the abundance of laminated cyanobacterial mats, and (4) the abundance and diversity of macrofauna. Cyanobacteria turned out to conserve the oil within the soil where they built laminated mats sealing the surface and thus, preventing oxygen from penetrating the substrate. On the other hand, crustaceans were the first macrofauna returning to contaminated soils. Following bioturbation by the crustaceans significantly accelerates the biodegradation of the hydrocarbons. Since the occurrence of the crabs (mainly Cleistotoma dotilliforme) is primarily restricted to tidal channels the density of the channel network between the affected salt marshes determines the time which is needed for regeneration. (orig.)

  16. Effect of acid deposition on soil animals and microorganisms: influence on structures and processes

    International Nuclear Information System (INIS)

    Principal effects of acid stress on the soil subsystem are increase or decrease in faunal and microfloral populations, changes in species assemblages and overall reductions in several soil microbiological processes. Little is known about the effects on nitrogen transformation (ammonification, nitrification, denitrification). Some possible but hypothetical scenarios for the effect of acidification stress on the forest ecosystem level are: (1) Inhibition of decomposition leads to an accumulation of litter. Immission and other disturbances may lead to humus disintegration and nitrate leaching; (2) Inhibition of mineralization reduces the availability of plant nutrients; (3) Decrease of the microfauna may cause disturbances of matter microcycling in the root zone; (4) Increase of the mesofauna may enhance the gracing pressure on mycorrhizal mycelia for even fine roots; (5) Decrease of the macrofauna (especially earthworms) lead to less bioturbation which impairs the buffer capacity of the litter and topsoil. A general outcome of liming experiments is stimulation of decomposition and mineralization: (1) Increased in nutrient arailability could lead to increased productivityin nutrient limited stands; (2) More irregular effects of animals on microbial activity may result in low stability of the soil-litter system and high liability to perturbations. (orig./vhe)

  17. 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.

  18. The effect of turbation on zinc relocation in a vertical floodplain soil profile

    International Nuclear Information System (INIS)

    Turbation is hypothesized to affect the redistribution of heavy metals in polluted floodplain soils by effects on mobility. This hypothesis was tested in microcosms by turbation of zinc-spiked sediment top layers. Manual turbation caused a fast decrease of the zinc content in the upper 15 cm of the soil, even though turbation was only applied to the upper two centimetres. It was especially zinc attached to colloid and organic matter particles that was redistributed from the top layer. Percolation processes resulted in the attached zinc being drained to depths of more than 15 cm. The decrease in zinc content of the topsoil was even stronger in combination with inundation. No indications were found for the redistribution of zinc as a result of an increase of the extractability with 0.01 M CaCl2 or changes in pH. The findings suggest that mechanical turbation and bioturbation may redistribute heavy metals from topsoils in polluted floodplains just after inundation as observed in these turbation experiments. - Intensive turbation of a zinc-polluted topsoil induces zinc transport to the subsoil by soil water transport of colloid and organic matter particles

  19. Permeability anisotropy and heterogeneity of a sandstone reservoir analogue : an estuarine to shoreface depositional system in the Virgelle Member, Milk River Formation, Writing-on-Stone Provincial Park, southern Alberta

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, R. [Memorial Univ. of Newfoundland, St. John' s, NL (Canada). Dept. of Earth Sciences; Krause, F.F. [Calgary Univ., AB (Canada). Dept. of Geology and Geophysics

    2006-12-15

    Permeability is an important property of reservoir rocks. Small-scale laminar structures within sandstones can influence highly anisotropic permeability fields which control single-phase fluid flow and two-phase mobility of immiscible phases such as oil-water. This study compared permeability trends from horizontal and vertical plugs of the Upper Santonian Virgelle Member sandstone at Writing-on-Stone Provincial Park in southern Alberta. It presented the results of probe permeameter gas flow measurements taken in different orientations on 2 samples from the Viking Formation cored at depth. Permeability anisotropy of laminated sandstones, initially established during deposition, can still be recognized at depth, along with the equivalent relative homogeneity of vertical permeability (kV). Permeability data tied to sedimentological/stratigraphic models is used to examine the controls on permeability distribution and their applicability to subsurface reservoirs. The general permeability trend responded to upward increasing grain size, locally modified by macroburrows, micro-bioturbation and calcareous cements. The results suggest that careful definition of lithofacies can provide the foundation for fluid flow models. The relative homogeneity of vertical permeability structure documented in this study may result from the baffling effect of laminar structure acting as filter. It is expected that cross-laminar fluid flow in such facies will form a uniform and efficient displacement front, by passing fewer pores relative to heterogeneous, fingering layer-parallel flow profile. 49 refs., 2 tabs., 17 figs.

  20. Recent sediment transport and deposition in the Cap-Ferret Canyon, South-East margin of Bay of Biscay

    Science.gov (United States)

    Schmidt, Sabine; Howa, Hélène; Diallo, Amy; Martín, Jacobo; Cremer, Michel; Duros, Pauline; Fontanier, Christophe; Deflandre, Bruno; Metzger, Edouard; Mulder, Thierry

    2014-06-01

    The Cap-Ferret Canyon (CFC), a major morphologic feature of the eastern margin of the Bay of Biscay, occupies a deep structural depression that opens about 60 km southwest of the Gironde Estuary. Detailed depth profiles of the particle-reactive radionuclides 234Th and 210Pb in interface sediments were used to characterise the present sedimentation (bioturbation, sediment mass accumulation, and focusing) in the CFC region. Two bathymetric transects were sampled along the CFC axis and the southern adjacent margin. Particle fluxes were recorded from the nearby Landes Plateau by means of sediment traps in 2006 and 2007. This dataset provides a new and comprehensive view of particulate matter transfer in the Cap-Ferret Canyon region, through a direct comparison of the canyon with the adjacent southern margin. Radionuclide profiles (234Th and 210Pb) and mass fluxes demonstrate that significant particle dynamics occur on the SE Aquitanian margin in comparison with nearby margins. The results also suggest show three distinct areas in terms of sedimentary activity. In the upper canyon (2000 m) can be considered inactive at annual or decadal scales. In contrast with the slow and continuous accumulation of relatively fresh material that characterises the middle canyon, the lower canyon receives pulses of sediment via gravity flows on longer time scales. At decadal scale, the CFC can be considered as a relatively quiescent canyon. The disconnection of the CFC from major sources of sediment delivery seems to limit its efficiency in particle transfer from coastal areas to the adjacent ocean basin.

  1. 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.

  2. Enantioselective bioaccumulation and dissipation of soil-associated metalaxyl enantiomers in tubifex.

    Science.gov (United States)

    Di, Shanshan; Liu, Tiantian; Lu, Yuele; Zhou, Zhiqiang; Diao, Jinling

    2014-01-01

    Many pesticides are chiral compounds and stereochemistry is an important factor for any reaction of chiral structures in biological systems. In this study, experiment about bioaccumulation of the two metalaxyl enantiomers in Tubifex (Oligochaeta, Tubificida) was conducted in laboratory aquatic ecosystems. Terrestrial soil spiked with two dose levels of metalaxyl was employed as the artificial bottom substrate. A method of determination of metalaxyl enantiomers in tubifex tissue, soil and overlying water were developed by HPLC. During a 14-day exposure, concentrations of metalaxyl in tubifex increased with the of soil concentration, however, the enantioselective bioaccumulation was only detected at high-dose exposure group, with the preferential accumulation of (-)-(R)-metalaxyl. The bioturbation activity of tubifex decreased water clarity and released soil-associated metalaxyl to overlying water. In those experiments where tubifex was exposed to metalaxyl from soil, pore water and overlying water, each route contributed to the total body burden, and our results indicated the pore water and soil are the primary exposure routes for high-dose exposure concentration treatment. PMID:24174372

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Facies and mechanical stratigraphy of the Middle Bakken, Mountrail county, North Dakota

    Energy Technology Data Exchange (ETDEWEB)

    Canter, Lyn; Skinner, Orion; Sonnenfeld, Mark; Williams, Mark [Whiting Oil and Gas Corp., Denver, CO (United States)

    2011-07-01

    Five facies are recognized in Middle Bakken cores from Sanish and Parshall fields of North Dakota. Facies E overlies the Lower Bakken shale; it is very thin and characterized by wackestone. Facies D is the thickest; it is a bioturbated, argillaceous, calcareous, very fine-grained sandstone/siltstone showing poor to fair reservoir quality. Facies C is composed of rhythmic, well-sorted, very fine-grained sandstone and siltstone; it is confined to middle Bakken paleolows. Facies B forms the Middle Bakken {sup c}lean bench{sup ;} its Gamma Ray log signature is the cleanest in the Middle Bakken. It has two sub-facies, B1 having the highest energy and coarsest grain in the Middle Bakken. This facies is not present at Parshall Field. Facies A contains four sub-facies. The mechanical stratigraphy produced by facies successions and event stratification seems to influence fracture height and spacing. Facies A, B, and C, having greater porosity, fracture susceptibility and permeability, remain the main horizontal target.

  8. Wave-influenced deltaic sandstone bodies and offshore deposits in the Viking Formation, Hamilton Lake area, south-central Alberta, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Dafoe, L.T.; Gingras, M.K.; Pemberton, S.G. [Alberta Univ., Edmonton, AB (Canada). Dept. of Earth and Atmospheric Sciences

    2010-06-15

    This analytical study incorporated sedimentological, ichnological and stratigraphic data to provide a framework for both deltaic and offshore deposition in the Hamilton Lake (HL) area in south-central Alberta. Fourty-one drill cores were logged within the area to conduct a comprehensive facies analysis of the Cretaceous Viking deposits at HL to refine the depositional history. The Viking deposits include a delta front, prodelta, upper offshore, lower offshore, shelf, slump and transgressive lag deposits. Various bioturbate textures proved useful in interpreting the paleoenvironment. Particular facies within HL strata contain physical and biogenic indicators of riverine discharge, and are considered to be deltaic in origin. This study focused on distinguishing between these deltaic deposits and strata reflecting normal-marine depositional conditions and relating facies within the stratigraphic framework. Four major bounding discontinuities and 2 major transgressive flooding surfaces separate units reflecting predominantly deltaic deposition, strictly offshore deposition, and mixed offshore and deltaic deposition. The implications of this study for petroleum exploration and development include better recognition of wave-influenced deltaic deposits in ancient successions. This paper presented a model that provided a better understanding of the nature of potential reservoirs in terms of lithology and morphology. In contrast to wave-dominated deltas or shoreface strata, sandy deposits in these wave-influenced systems are expected to contain higher proportions of mud, particularly mudstone laminae that reduce overall permeability between sandstone beds. 55 refs., 2 tabs., 15 figs.

  9. 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

  10. Characterization of specificity of bacterial community structure within the burrow environment of the marine polychaete Hediste (Nereis) diversicolor.

    Science.gov (United States)

    Pischedda, Laura; Militon, Cécile; Gilbert, Franck; Cuny, Philippe

    2011-12-01

    Bioturbation is known to stimulate microbial communities, especially in macrofaunal burrows where the abundance and activities of bacteria are increased. Until now, these microbial communities have been poorly characterized and an important ecological question remains: do burrow walls harbor similar or specific communities compared with anoxic and surface sediments? The bacterial community structure of coastal sediments inhabited by the polychaete worm Hediste diversicolor was investigated. Surface, burrow wall and anoxic sediments were collected at the Carteau beach (Gulf of Fos, Mediterranean Sea). Bacterial diversity was determined by analyzing small subunit ribosomal RNA (16S rRNA) sequences from three clone libraries (168, 179 and 129 sequences for the surface, burrow wall and anoxic sediments, respectively). Libraries revealed 306 different operational taxonomic units (OTUs) belonging to at least 15 bacterial phyla. Bioinformatic analyses and comparisons between the three clone libraries showed that the burrow walls harbored a specific bacterial community structure which differed from the surface and anoxic environments. More similarities were nevertheless found with the surface assemblage. Inside the burrow walls, the bacterial community was characterized by high biodiversity, which probably results from the biogeochemical heterogeneity of the burrow system. PMID:21946148

  11. Capping efficiency of various carbonaceous and mineral materials for in situ remediation of polychlorinated dibenzo-p-dioxin and dibenzofuran contaminated marine sediments: sediment-to-water fluxes and bioaccumulation in boxcosm tests.

    Science.gov (United States)

    Josefsson, Sarah; Schaanning, Morten; Samuelsson, Göran S; Gunnarsson, Jonas S; Olofsson, Ida; Eek, Espen; Wiberg, Karin

    2012-03-20

    The efficiency of thin-layer capping in reducing sediment-to-water fluxes and bioaccumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans, hexachlorobenzene, and octachlorostyrene was investigated in a boxcosm experiment. The influence of cap thickness (0.5-5 cm) and different cap materials was tested using a three-factor experimental design. The cap materials consisted of a passive material (coarse or fine limestone or a marine clay) and an active material (activated carbon (AC) or kraft lignin) to sequester the contaminants. The cap thickness and the type of active material were significant factors, whereas no statistically significant effects of the type of passive material were observed. Sediment-to-water fluxes and bioaccumulation by the two test species, the surface-dwelling Nassarius nitidus and the deep-burrowing Nereis spp., decreased with increased cap thickness and with addition of active material. Activated carbon was more efficient than lignin, and a ~90% reduction of fluxes and bioaccumulation was achieved with 3 cm caps with 3.3% AC. Small increases in fluxes with increased survival of Nereis spp. indicated that bioturbation by Nereis spp. affected the fluxes. PMID:22339559

  12. Effects of eutrophication on contaminant cycling in marine benthic systems

    Energy Technology Data Exchange (ETDEWEB)

    Gunnarsson, Jonas; Granberg, Maria; Rosenberg, Rutger [Goeteborg Univ. (Sweden). Dept. of Marine Ecology; Bjoerk, Mikael; Gilek, Michael [Stockholm Univ. (Sweden). Dept. of Systems Ecology

    2000-08-01

    Effects of inputs of organic matter were studied on bioavailability and cycling of hydrophobic organic contaminants (HOCs) in benthic ecosystems of the Baltic and Kattegat Seas. In laboratory experiments, effects of microalgae additions were studied on the bioaccumulation of HOCs (PCBs and PAHs) by the blue mussel Mytilus edulis, the brittle star Amphiura filiformis, and the polychaete Nereis diversicolor. Contrary to the equilibrium partitioning theory, bioaccumulation was proportional to the concentrations of algae and organic carbon. This was attributed to the high nutritional quality of the algal organic carbon and suggests that feeding rather than equilibrium partitioning governed bioaccumulation in these species. In the field, annual mass fluxes of PCBs in blue mussels and in brittle stars were estimated, as well as contaminant transfer to higher trophic levels. Our results suggest that: i) Eutrophication processes may contribute to increase HOC accumulation in benthic species. ii) Temporal variation in the quantity and quality of organic carbon needs to be considered when assessing contamination of benthic systems. iii) Macrofaunal feeding activities are important for the benthic-pelagic coupling of HOCs. iv) Bioturbation enhances the release of HOCs from sediment to overlying water.

  13. Interactions between macro-algal mats and invertebrates in the Ythan estuary, Aberdeenshire, Scotland

    Science.gov (United States)

    Raffaelli, D.

    2000-07-01

    Blooms of opportunistic green macro-algae are a common feature of coastal areas and their effects on mudflat invertebrates can be dramatic. On the Ythan estuary, Aberdeenshire, Scotland, we have carried out a number of manipulative field experiments designed to evaluate the effects on invertebrates of different species of macro-algae with contrasting ecologies, and the effects of invertebrates on the development of the blooms. Macro-algal mats were found to have dramatic nega- tive effects on the density of the amphipod Corophium volutator, with higher algal biomasses having greater impact. The mechanism for this interaction seems to be interference by the algal filaments with the feeding behaviour of the amphipod. In contrast, the polychaete Capitella spp. increases in abundance under macro-algal mats due to enrichment of the sediment with organic material. These two interactions are seen at all scales, in areas of less than 1 m2 to the scale of the entire estuary, irrespective of the species composition of the macro- algal mats. Bioturbation by Corophium and grazing by the snail Hydrobia ulvae had little effect on macro-algal biomass, but there were less algae when the polychaete Nereis diversicolor was present. The most significant interaction in this system is the pronounced negative impact of algal mats on the abundance of Corophium, probably the most important invertebrate species in the diets of the estuary's shorebirds, fish and epibenthic crustaceans.

  14. Temporal variability of denitrification in estuarine sediments

    Science.gov (United States)

    Law, C. S.; Rees, A. P.; Owens, N. J. P.

    1991-07-01

    Sediment denitrification rates and fluxes of nitrous oxide, nitrate, nitrite and ammonium were determined at two intertidal sites in the Tamar estuary (S.W. England). High sediment nitrate uptake rates were recorded throughout the year, whereas the nitrite and ammonium fluxes were positive (from sediment to water column), with the former resulting from nitrification. Nitrous oxide flux was also positive, being largely attributable to denitrification with some contribution from nitrification or nitrification-denitrification coupling. No relationship was apparent between denitrification rate and nitrate concentration in the overlying water, invalidating the notion that denitrification automatically regulates nitrate during periods of elevated ambient concentration. However, denitrification exhibited a strong covariance with the degree of sediment bioturbation ( Nereis diversicolor), which was considered to be attributable to increased transport and supply of nitrate via Nereis burrows. Denitrification accounted for 8·5% of the annual total nitrate loading to the Tamar estuary, although a maximum of 100% was observed in summer when the phytoplankton nutrient requirement would also be highest.

  15. Sedimentary environment inferred from sedimentation rates by 210Pb and 137Cs and their inventories in Mutsu Bay, Japan

    International Nuclear Information System (INIS)

    Fourteen sediment cores were collected from Mutsu Bay, Aomori in Japan, and excess 210Pb and 137Cs were measured γ-spectrometrically. The spatial distributions of sedimentation rates by 210Pbex and 137Cs and their inventories were studied in order to clarify whole pictures about the sedimentary environment of Mutsu Bay. Excessively post-depositional mixing (up to a depth of 10-15 cm) of surface sediments by bioturbation was observed on the 210Pbex depth profiles in cores from the offshore areas. The sedimentation rates calculated varied in the wide range from 0.04 to 0.2 g/cm2/y. The sedimentation rates using 137Cs method could not be applied. Apart from the 210Pbex inventories from the nearshore area, the responding inventories (17-30 kBq/m2) from the offshore area were higher than the reported value of ca.15 kBq/m2 in the surrounding soils, indicating that the sediment focusing due to the inner current etc., to the deeper area from the surrounding nearshore area, affects the sediment accumulation in the offshore area. (author)

  16. The geochemistry of uranium and thorium in coastal marine sediments and sediment pore waters

    International Nuclear Information System (INIS)

    Pore water profiles of uranium and thorium isotopes in the muddy sediments of Buzzards Bay, MA permit an assessment of the effect of diagenetic redox reactions on the geochemical behaviour of these elements. Uranium shows a pronounced minimum pore water concentration (approx. 1.2dpm/kg) near the sediment water interface (0-3 cm) which coincides with the pore water Fe maximum. U concentrations increase with depth to a broad maximum which is greater than the overlying seawater value, then decrease. The coincidence of the pore water uranium and Fe maximum is consistent with the hypothesis of reduction of U(VI) to U(IV) and removal from solution at about the same depth (or pe) as Fe is reduced. Increases in pore water U with depth appear to be related to release of authigenic (seawater) U(VI) to solution, possibly as alkalinity and pH increase and organic matter with which the U is associated is oxidized. In contrast, pore water profiles of the long-lived Th isotopes 232Th and 230Th show low activities (234Th shows greatest pore water activities in the upper 5 cm and is present at virtually zero activities elsewhere in the sediment column. The upper few centimeters of the sediment generally contain excess 234Th scavenged from the overlying water column and distributed by bioturbation. (author)

  17. 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)

  18. 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.

  19. 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

  20. 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

  1. 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

  2. Integrating models to simulate emergent behaviour: effects of organic matter on soil hydraulics in the ICZ-1D soil-vegetation model

    Science.gov (United States)

    Valstar, Johan; Rowe, Ed; Konstantina, Moirogiorgou; Giannakis, Giorgos; Nikolaidis, Nikolaos

    2014-05-01

    Soil develops as a result of interacting processes, many of which have been described in more or less detailed models. A key challenge in developing predictive models of soil function is to integrate processes that operate across a wide range of temporal and spatial scales. Many soil functions could be classified as "emergent", since they result from the interaction of subsystems. For example, soil organic matter (SOM) dynamics are commonly considered in relation to carbon storage, but can have profound effects on soil hydraulic properties that are conventionally considered to be static. Carbon fixed by plants enters the soil as litterfall, root turnover or via mycorrhizae. Plants need water and nutrients to grow, and an expanding root system provides access to a larger volume of soil for uptake of water and nutrients. Roots also provide organic exudates, such as oxalate, which increase nutrient availability. Carbon inputs are transformed at various rates into soil biota, CO2, and more persistent forms of organic matter. The SOM is partly taken up into soil aggregates of variable sizes, which slows down degradation. Water availability is an important factor as both plant growth and SOM degradation can be limited by shortage of water. Water flow is the main driver for transport of nutrients and other solutes. The flow of water in turn is influenced by the presence of SOM as this influences soil water retention and hydraulic conductivity. Towards the top of the unsaturated zone, bioturbation by the soil fauna transports both solid material and solutes. Weathering rates of minerals determine the availability of many nutrients and are in turn dependent on parameters such as pH, water content, CO2 pressure and oxalate concentration. Chemical reactions between solutes, dissolution and precipitation, and exchange on adsorption sites further influence solute concentrations. Within the FP7 SoilTrEC project, we developed a model that incorporates all of these processes, to

  3. 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

  4. 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.

  5. Morphology of submarine canyon system and geotechnical properties of surficial sediments across the Peru-Chile forearc

    Energy Technology Data Exchange (ETDEWEB)

    Bergersen, D.D.; Coulbourn, W.T.; Moberly, R.

    1989-03-01

    During August 1987, a SeaMARC II side-scan and sampling survey was conducted across the Peru-Chile forearc from 17/degrees/30'S to 19/degrees/30'S. Side-scan images reveal a complex submarine canyon system. Incised canyons meander across the Arequipa basin; their sinuosity results from erosion and cutbank slumping of the basin sediments. Lenticular packets of strata visible in reprocessed digital single-channel seismic profiles are interpreted to be buried channels. Tributary canyons coalesce into a single canyon at the structural high that deviates from its north-south course to a northeast-southwest course as a result of stream piracy. A dendritic drainage basin forming on the midslope may be the rejuvenation of an abandoned channel. Sediment properties were measured on 42 free-fall cores and 7 piston cores recovered both in and around the submarine canyon. Olive-gray (5Y 3/2) hemipelagic mud is the predominant sediment across the forearc. Most cores exhibit a small degree of bioturbation and thin laminae of sand; the number of sand laminae increases as the distance away from the canyon decreases. Shear strengths, averaged over a 1-m core length, decrease slightly with water depth. Carbonate content in all samples from this area is negligible with the exception of one piston core recovered from the upper reaches of the canyon, the bottom of which is composed of gravel- and sand-size shell fragments. Bulk mineralogy, determined from semiquantitative analysis of x-ray diffraction patterns, shows a decrease in relative feldspar percent and an increase in total clay content with increasing water depth. Preliminary analysis of core tops shows a mean grain size in the medium to very fine silt class, with increasing grain size toward the canyon. Smear slide counts generally show a surprisingly low abundance of volcanic glass and biogenic material, particularly diatoms.

  6. 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

  7. 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.

  8. 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

  9. Characteristics and origin of Earth-mounds on the Eastern Snake River Plain, Idaho

    International Nuclear Information System (INIS)

    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 floorclose 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

  10. 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.

  11. 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.

  12. 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.

  13. {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.

  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. Dynamic modelling of radionuclide uptake by marine biota: application to the Fukushima nuclear power plant accident.

    Science.gov (United States)

    Vives i Batlle, Jordi

    2016-01-01

    The dynamic model D-DAT was developed to study the dynamics of radionuclide uptake and turnover in biota and sediments in the immediate aftermath of the Fukushima accident. This dynamics is determined by the interplay between the residence time of radionuclides in seawater/sediments and the biological half-lives of elimination by the biota. The model calculates time-variable activity concentration of (131)I, (134)Cs, (137)Cs and (90)Sr in seabed sediment, fish, crustaceans, molluscs and macroalgae from surrounding activity concentrations in seawater, with which to derive internal and external dose rates. A central element of the model is the inclusion of dynamic transfer of radionuclides to/from sediments by factorising the depletion of radionuclides adsorbed onto suspended particulates, molecular diffusion, pore water mixing and bioturbation, represented by a simple set of differential equations coupled with the biological uptake/turnover processes. In this way, the model is capable of reproducing activity concentration in sediment more realistically. The model was used to assess the radiological impact of the Fukushima accident on marine biota in the acute phase of the accident. Sediment and biota activity concentrations are within the wide range of actual monitoring data. Activity concentrations in marine biota are thus shown to be better calculated by a dynamic model than with the simpler equilibrium approach based on concentration factors, which tends to overestimate for the acute accident period. Modelled dose rates from external exposure from sediment are also significantly below equilibrium predictions. The model calculations confirm previous studies showing that radioactivity levels in marine biota have been generally below the levels necessary to cause a measurable effect on populations. The model was used in mass-balance mode to calculate total integrated releases of 103, 30 and 3 PBq for (131)I, (137)Cs and (90)Sr, reasonably in line with previous

  16. 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)

  17. 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

  18. 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.

  19. 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.

  20. 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

  1. Sediment budget-based estimates of trace metal inputs to a Chesapeake estuary

    Science.gov (United States)

    Marcus, W. A.; Nielsen, C. C.; Cornwell, J. C.

    1993-09-01

    This article evaluates whether a sediment budget for the South River, Maryland, can be coupled with metals data from sediment cores to identify and quantify sources of historic metal inputs to marsh and subtidal sediments along the estuary. Metal inputs to estuarine marsh sediments come from fluvial runoff and atmospheric deposition. Metal inputs to subtidal sediments come from atmospheric deposition, fluvial runoff, coastal erosion, and estuarine waters. The metals budget for the estuary indicates that metal inputs from coastal erosion have remained relatively constant since 1840. Historical variations in metal contents of marsh sediments have probably resulted primarily from increasing atmospheric deposition in this century, but prior to 1900 may reflect changing fluvial sources, atmospheric inputs, or factors not quantified by the budget. Residual Pb, Cu, and Zn in the marsh sediments not accounted for by fluvial inputs was low to moderate in 1840, decreased to near zero circa 1910, and by 1987 had increased to levels that were one to ten times greater than those of 1840. Sources of variability in subtidal cores could not be clearly discerned because of geochemical fluxes, turbulent mixing, and bioturbation within the cores. The sediment-metal budgeting approach appears to be a viable method for delineating metal sources in small, relatively simple estuarine systems like the South River and in systems where recent deposition (for example, prograding marshes) prevents use of deep core analysis to identify “background” levels of metal. In larger systems or systems with more variable sources of sediment and metal input, however, assumptions and measurement errors in the metal budgeting approach suggest that deep core analysis and normalization techniques are probably preferable for identifying anthropogenic impacts.

  2. Sedimentation rates and fluxes in the continental shelf mud fields in the Bay of Biscay (France)

    Science.gov (United States)

    Lesueur, P.; Jouanneau, J.-M.; Boust, D.; Tastet, J.-P.; Weber, O.

    2001-08-01

    Sedimentation rates in shelf mud fields of the Bay of Biscay (the Gironde shelf mud patches and "La Grande Vasière") were investigated for a 100-yr time scale, using 210Pb geochronology of nine cores. The distribution of apparent sedimentation rates reveals a general trend along the terrigenous dispersal system from the Gironde outlet of: no or negligible (sedimentation in the inner zone of the mud fields; 0.1-0.2 cm yr -1 in the outer zone where the supply is reduced; and a maximum value of about 0.5 cm yr -1 in the depocentre of the main mud field. Except for the latter value, the 210Pb sedimentation rates are of the same magnitude as longer-term rates based on 14C, and although slightly higher, are in good agreement with an earlier estimation determined for the rate of accumulation of surficial sediments, using pollen analyses. These differences are interpreted as being due to an increase in the supply of fine-grained sediment over the last century (from 0.2 to 0.5 cm yr -1), perhaps as a result of an intensification of estuarine suspended matter supply to the shelf. Compilation of a sediment budget shows that about one third of the annual Gironde solid discharge is trapped in the Gironde nearshore shelf mud fields. The mid-shelf muddy belt (i.e. "La Grande Vasière") is the site of accumulation of fine-grained material from various terrigenous sources (mainly from the Gironde and Loire rivers). Two cores from the latter area yielded a maximum rate of sedimentation of 0.2 cm yr -1. Mixing processes dominate in this open middle shelf, due to the periodic sediment removal by long-period swells and bioturbation.

  3. 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.

  4. 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

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

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    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

  6. New possibilities for soil and landscape evolution modelling by coupling LAPSUS and MILESD

    Science.gov (United States)

    Vanwalleghem, Tom; Temme, Arnaud

    2014-05-01

    The formation of soils and evolution of landscapes over time are closely coupled. Erosion and lateral sediment redistribution impact soil profiles in hilly and mountainous areas and changes can be very rapid due to human-induced land use changes. On the other hand, key soil properties, such as depth and texture, are crucial for understanding the geomorphic response of landscapes. Also for understanding biogeochemical fluxes at the soil profile and landscape scale, a coupled approach is crucial. At present, it is hypothesized that many of these processes are controlled by thresholds and respond in a non-linear manner. There is therefore an increasing need for models that integrate both processes and mimic this complexity. Here, we present a new coupled model of the co-evolution of soils and landscapes. This model is based on landscape evolution model LAPSUS and includes the soil forming processes represented in the model MILESD. The model allows the formation of a vertical soil profile with a user-specified number of layers. The main soil forming processes included are soil formation from bedrock, physical and chemical weathering, bioturbation, clay neoformation and clay lessivage. Landscape evolution processes represented are water erosion, tillage erosion, landsliding, creep, solifluction and simplified tectonics. We analyze the effect of different climatic and land use scenarios on 1) the spatial and vertical distribution of key soil properties 2) the dynamics of landscape evolution and feedbacks of soil properties on erosion 3) the temporal dynamics of sediment flux, sediment grading and carbon fluxes. The results clearly illustrate the potential of coupling soil and landscape formation for an improved understanding of long-term soil and landscape dynamics.

  7. 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

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

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    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.

  9. 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.

  10. Nitrate reduction functional genes and nitrate reduction potentials persist in deeper estuarine sediments. Why?

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    Sokratis Papaspyrou

    Full Text Available Denitrification and dissimilatory nitrate reduction to ammonium (DNRA are processes occurring simultaneously under oxygen-limited or anaerobic conditions, where both compete for nitrate and organic carbon. Despite their ecological importance, there has been little investigation of how denitrification and DNRA potentials and related functional genes vary vertically with sediment depth. Nitrate reduction potentials measured in sediment depth profiles along the Colne estuary were in the upper range of nitrate reduction rates reported from other sediments and showed the existence of strong decreasing trends both with increasing depth and along the estuary. Denitrification potential decreased along the estuary, decreasing more rapidly with depth towards the estuary mouth. In contrast, DNRA potential increased along the estuary. Significant decreases in copy numbers of 16S rRNA and nitrate reducing genes were observed along the estuary and from surface to deeper sediments. Both metabolic potentials and functional genes persisted at sediment depths where porewater nitrate was absent. Transport of nitrate by bioturbation, based on macrofauna distributions, could only account for the upper 10 cm depth of sediment. A several fold higher combined freeze-lysable KCl-extractable nitrate pool compared to porewater nitrate was detected. We hypothesised that his could be attributed to intracellular nitrate pools from nitrate accumulating microorganisms like Thioploca or Beggiatoa. However, pyrosequencing analysis did not detect any such organisms, leaving other bacteria, microbenthic algae, or foraminiferans which have also been shown to accumulate nitrate, as possible candidates. The importance and bioavailability of a KCl-extractable nitrate sediment pool remains to be tested. The significant variation in the vertical pattern and abundance of the various nitrate reducing genes phylotypes reasonably suggests differences in their activity throughout the

  11. Spatial partitioning between species of the phytoplankton-feeding guild on an estuarine intertidal sand flat and its implication on habitat carrying capacity

    Science.gov (United States)

    Tamaki, Akio; Nakaoka, Ayumi; Maekawa, Hideki; Yamada, Fumihiko

    2008-07-01

    The fishery yield of Manila clams, Ruditapes philippinarum, increased considerably in the 1970s but has decreased rapidly since the middle 1980s on extensive intertidal sand flats in Ariake Sound (Kyushu, Japan). A survey conducted in 2004 on a 3.4-km 2 sand flat located in the central part of the Sound (Shirakawa sand flat) revealed four dominant species: two thalassinidean shrimps ( Upogebia major and Nihonotrypaea japonica), which are deep-reaching burrow dwellers with strong bioturbation activities, and two bivalves ( Mactra veneriformis and R. philippinarum). All four species belong to a phytoplankton (diatom)-feeding guild. In the late 1970s, the Manila clam population prevailed in high densities over the entire sand flat, whereas its distribution was restricted to the lowest quarter of the shore in 2004. In contrast, the population sizes and zones of occurrence of the other phytoplankton feeders have expanded in the absence of R. philippinarum, perhaps an indication of competitive release. After establishment, effects of the thalassinidean shrimps on sediment stability appear to have further reduced clam abundances. Across the sand flat in 2004, wet weight population biomass estimates for N. japonica, U. major, M. veneriformis, and R. philippinarum (whole body for shrimps and soft tissue for bivalves) were 304, 111, 378, and 234 tonnes, respectively. Based on Manila clam fishery yield records from Shirakawa, the carrying capacity of the Shirakawa sand flat in the late 1970s was estimated to be two times greater than the sum value for the whole phytoplankton-feeding guild in 2004. It is hypothesized that (1) the amount of phytoplankton determines the carrying capacity for the benthic community on the Shirakawa sand flat, with both phytoplankton and benthic biomass at maxima in the late 1970s, and (2) the subsequent increases in competition for space have caused further declines in the Manila clam population biomass to approximately one-eighth of its past

  12. 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.

  13. Inorganic geochemical indicators of glacial-interglacial changes in productivity and anoxia on the California continental margin

    Science.gov (United States)

    Dean, W.E.; Gardner, J.V.; Piper, D.Z.

    1997-01-01

    Evidence from sediments in cores collected from within the present oxygen-minimum zone (OMZ; 600-1200 m) on the central and northern California margins record several episodes during the last interstadial (OIS-3, ca. 60-24 ka) of deposition of laminated sediments containing elevated concentrations of several trace elements indicative of anoxic conditions (e.g., Mo, Ni, Zn, and Cu). The presence of abundant well-preserved organic matter, as well as lack of bioturbation and the presence of elevated concentrations of Mo and other trace elements, all support the theory that the OMZ in the northeastern Pacific Ocean was more intense, possibly anoxic, at several times during the late Pleistocene. Sediments of all ages in cores from the southern California margin contain elevated concentrations of Mo, suggesting that this area has always had higher rates of sulfate reduction than either the central or northern California areas. Most of the Ba in sediments in all cores collected on the upper continental slope (200-2700 m) off California and southern Oregon is derived from detrital clastic material, and this source did not change much in time. However, the amount of biogenic Ba did vary with time, and these variations closely follow the temporal variations in organic C (Corg) mass accumulation rate. Using Ba and Corg mass accumulation rates as proxy variables for productivity, all cores show that organic productivity under the California Current upwelling system was highest during OIS-3 and the Holocene, and lowest during the last glacial interval (LGI, ca. 24-10 ka). All paleoproductivity proxy variables indicate that the southern California area has always experienced higher productivity than other areas under the California Current, at least over the last 50 ky. Copyright ?? 1997 Elsevier Science Ltd.

  14. 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

  15. A High-Resolution Record of Early Miocene Antarctic Glacial History From Downhole Logs, Site 1165, ODP Leg 188

    Science.gov (United States)

    Williams, T.; Barr, S.; Handwerger, D.

    2002-12-01

    ODP Site 1165, located 400 km NW of Prydz Bay, contains the most detailed record yet obtained of Early Miocene Antarctic glacial history. The 520-m-thick Early Miocene consists of dark grey claystone with silt laminae (contourites) alternating with decimeter-scale layers of greenish-grey bioturbated claystone that contain common ice rafted debris (IRD). These sediments are interpreted to record pulses of IRD from the continent, and alternations in the position or strength of the currents at the site. Downhole logs of electrical resistivity, natural gamma radiation, and density also record the alternations between the two facies. Here we assess the lithological significance of the logs by examining the opal, IRD, and susceptibility of two short intervals at high resolution, with samples taken every 10 cm, or about 1250 yr. The IRD-bearing greenish-grey claystone corresponds to higher resistivity and density because of increased cementation by silica, and corresponds to lower natural gamma radiation because of decreased clay content. Thus, using the logs, lithology can be inferred for intervals where no core was recovered. Based mainly on magnetostratigraphy, the age of the base of the hole is 22 Ma, and the sedimentation rate for the Early Miocene about 9 cm/kyr. The regular spacing of the facies alternations in the logs suggests they are astronomically paced. Between 18-20 Ma, the main periodicity is in the precessional range, and between 20-22 Ma, the logs have a saw-toothed form, with a major peak in IRD at the beginning of each, repeating about every 100 kyr. We think that the IRD pulses represent deglaciations. Hence our data suggest that the Antarctic continent, at least around the Prydz Bay region, was glaciated in the Early Miocene, and that the size of the ice sheet oscillated on Milankovitch time scales.

  16. Paleomagnetic Dating of Holocene Rapidly Deposited Layers From the Saguenay Fjord, Quebec, Canada

    Science.gov (United States)

    St-Onge, G.; Mulder, T.; Piper, D. J.; Hillaire-Marcel, C.; Stoner, J. S.

    2006-12-01

    The Saguenay Fjord (Quebec, Canada) area has been struck by several natural disasters in the last 350 years. Among these disasters are the 1663 (M~7) and 1988 (M=6) earthquakes as well as the flood of 1996. These events triggered the deposition of thick layers, ranging from a few centimetres to about sixteen metres in the Saguenay Fjord inner basin. A 38 m-long piston core (core MD99-2222) was sampled from the deepest part of the Saguenay Fjord inner basin as part of the 1999 IMAGES-V (International Marine Past Global Change Study) program in order to determine the frequency of natural hazards such as earthquakes during the Holocene. Based on physical, magnetic and sedimentological data, we identified at least 14 rapidly deposited layers (RDL) in core MD99-2222. These layers contrast sharply from the dark grey bioturbated "background" sediments and are visually recognizable by their light color due to higher CaCO3 content resulting from the incorporation of light grey, slightly calcareous, Laflamme Sea Clays. In addition, most RDL have a sandy base with corresponding peaks in density and magnetic susceptibility, along with generally lower paleomagnetic inclinations that indicate an energetic depositional process where the magnetic particles are plastered horizontally because of high flow velocity and rapid sediment accumulation. Homogeneous, light grey, clayey silt beds generally overlie the sandy bases. Unfortunately, because CaCO3 dissolution occurs in the Saguenay Fjord sediments, little material is available for radiocarbon dating, making the setting of a robust chronology difficult. Here, we will show how changes in the Earth's magnetic field intensity and direction were used, in conjunction with 210Pb dating, one AMS 14C date and the recognition of a turbidite associated with the 1663 earthquake, to construct the age model for core MD99-2222 and thus to date all the RDL.

  17. 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.

  18. 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.

  19. Temporal and spatial distribution patterns of 210Po/210Pb and their implication in biogeochemical cycle along coastal region of China

    International Nuclear Information System (INIS)

    The natural radionuclide 210Po and 210Pb were analyzed in samples of atmospheric deposition (dry+wet), river water, tidal flat sediments and seawater along the coastal region of China. The results showed that the atmospheric deposition fluxes of 210Po and 210Pb with a similar trend in yearly time scale, changing seasonally with a higher value in spring and winter. As the river input (XLJ, fresh water end- number of the Chanjiang River), approximately 86% and 78% of the total 210Po and 210Pb in the water column were in particulate phrase, demonstrating that 210Po and 210Pb was easily absorbed and scavenged by the riverine particles. Except in Feb., Apr. and Oct., the ratio 210Po/210Pb of water column was less than 1.0 showing a deficiency 210Po relative to 210Pb. In surface sediments of east Chongming tidal flat of the Changjiang Estuary, the activities of 210Po and 210Pb were decreasing with the height of tidal flat (from land to seaward), due to the variations of the sediments grain size, the vegetational areas and the hydrodynamics force. Although a bit different from 2009 to 2010, the ratios of 210Po/210Pb were over 1.0 in both of two years, suggesting that 210Po was absorbed onto organic matter in the frequent bioturbation processes. In the coastal water, all the results showed a 210Po-deficiency relative to 210Pb in Yellow Sea since the atmospheric deposition source and bio-scavenge in water column. (author)

  20. Early Eocene volcanic ashes on Greifswalder Oie and their depositional environment, with an overview of coeval ash-bearing deposits in northern Germany and Denmark

    Science.gov (United States)

    Obst, Karsten; Ansorge, Jörg; Matting, Sabine; Hüneke, Heiko

    2015-11-01

    Unconsolidated bentonites and carbonate-cemented volcanic ashes occur in northern Germany within the clay sequence of the Lamstedt and Schlieven Formations documented by several wells. Ash-bearing carbonate concretions (so-called cementstones) are also known from glacially transported rafts and erratic boulders on the Baltic Sea island Greifswalder Oie, representing the easternmost exposures of early Eocene sediments in the North Sea Basin. The ashes can be correlated with water-lain ashes of the Danish Fur and Ølst Formations (mo-clay) generated during the opening of the North Atlantic Ocean about 55 Ma ago. Two types of cementstones can be distinguished on the basis of the mineralogical composition, sedimentary features and fossil content. Greifswalder Oie type I contains a black, up to 12-cm-thick ash deposit that follows above two distinct thin grey ash layers. The major ash unit has a rather homogeneous lower part; only a very weak normal grading and faint lamination are discernible. In the upper part, however, intercalations with light mudstone, in part intensively bioturbated, together with parallel and cross-lamination suggest reworking of the ash in a shallow marine environment. Major and trace element compositions are used to correlate type I ashes with those of the Danish-positive series which represent rather uniform ferrobasalts of the Danish stage 4, probably related to the emergence of proto-Iceland. In contrast, type II ash comprises a single, normally graded, about 5-cm-thick layer of water-lain air-fall tuff, which is embedded in fine-grained sandstone to muddy siltstone. Type II ash is characterised by very high TiO2 but low MgO contents. Exceptional REE patterns with a pronounced positive Eu anomaly suggest intense leaching of the glass that hampers exact correlation with pyroclastic deposits within the North Atlantic Igneous Province.

  1. Large organic-walled Protista ( Gromia) in the Arabian Sea: Density, diversity, distribution and ecology

    Science.gov (United States)

    Aranda da Silva, A.; Gooday, A. J.

    2009-03-01

    The genus Gromia includes large marine protists ('gromiids') with filose pseudopodia and sack-like organic tests. The first deep-water species were discovered in the 1990s on the Oman Margin of the Arabian Sea and subsequently found on the Pakistan Margin. We present a survey of gromiids in samples collected off Oman in 2002 and off Pakistan in 2003. In addition to the two species ( Gromia sphaerica and Gromia pyriformis) already described from this area, at least eight undescribed gromiid species were present. Sausage shaped, grape shaped and spherical morphotypes were represented among this material. On the Oman Margin, gromiids occurred in densities up to several thousand individuals m -2 at 1400 and 1700 m but were much less common at 1100 and 2000 m. Apart from G. pyriformis, which was fairly common (several hundred individuals m -2) at 1000 m, gromiids were uncommon in core samples taken off Pakistan, with 11 indiv. m -2 at 1200 m and 19 indiv. m -2 at 1850 m. On both margins, these protists occurred at depths >1000 m where bottom-water oxygen concentrations exceeded ˜0.2 ml l -1 (=8.92 μM l -1) land sediments were fully bioturbated and oxidised. However, they were not observed at similar oxygen levels above the OMZ. Most gromiids lived on the sediment surface with their apertures facing down and their pseudopodia presumably deployed into the sediment to feed on surficial material and associated bacteria. We conclude that these large protists may play an important ecological role in the bathyal Arabian Sea, particularly in carbon cycling but also in structuring the surficial sediments. In addition, their tests, particularly those of G. sphaerica, provide substrates for attached Foraminifera.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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)

  7. Coupled Environmental Processes in the Mojave Desert and Implications for ET Covers as Stable Landforms

    International Nuclear Information System (INIS)

    Monolayer evapotranspiration (ET) covers are the baseline method for closure of disposal sites for low-level radioactive waste (LLW), mixed LLW, and transuranic (TRU) waste at the Nevada Test Site (NTS). The regulatory timeline is typically 1,000 years for LLW and 10,000 years for TRU waste. Covers for such waste have different technical considerations than those with shorter timelines because they are subject to environmental change for longer periods of time, and because the environmental processes are often coupled. To evaluate these changes, four analog sites (approximately 30, 1,000 to 2,000, 7,000 to 12,500, and 125,000 years in age) on the NTS were analyzed to address the early post-institutional control period (the youngest site), the 1,000-year compliance period for disposal of LLW, and the 10,000-year period for TRU waste. Tests included soil texture, structure, and morphology; surface soil infiltration and hydraulic conductivity; vegetation and faunal surveys; and literature reviews. Separate measurements were made in plant undercanopy and intercanopy areas. The results showed a progressive increase in silt and clay content of surface soils with age. Changes in soil texture and structure led to a fivefold decline in saturated hydraulic conductivity in intercanopy areas, but no change in undercanopies, which were subject to bioturbation. These changes may have been responsible for the reduction in total plant cover, most dramatically in intercanopy areas, primarily because more precipitation either runs off the site or is held nearer to the surface where plant roots are less common. The results suggest that covers may evolve over longer timeframes to stable landforms that minimize the need for active maintenance

  8. Oxygen, carbon, and nutrient exchanges at the sediment-water interface in the Mar Piccolo of Taranto (Ionian Sea, southern Italy).

    Science.gov (United States)

    De Vittor, Cinzia; Relitti, Federica; Kralj, Martina; Covelli, Stefano; Emili, Andrea

    2016-07-01

    In the shallow environment, the nutrient and carbon exchanges at the sediment-water interface contribute significantly to determine the trophic status of the whole water column. The intensity of the allochthonous input in a coastal environment subjected to strong anthropogenic pressures determines an increase in the benthic oxygen demand leading to depressed oxygen levels in the bottom waters. Anoxic conditions resulting from organic enrichment can enhance the exchange of nutrients between sediments and the overlying water. In the present study, carbon and nutrient fluxes at the sediment-water interface were measured at two experimental sites, one highly and one moderately contaminated, as reference point. In situ benthic flux measurements of dissolved species (O2, DIC, DOC, N-NO3 (-), N-NO2 (-), N-NH4 (+), P-PO4 (3-), Si-Si(OH)4, H2S) were conducted using benthic chambers. Furthermore, undisturbed sediment cores were collected for analyses of total and organic C, total N, and biopolymeric carbon (carbohydrates, proteins, and lipids) as well as of dissolved species in porewaters and supernatant in order to calculate the diffusive fluxes. The sediments were characterized by suboxic to anoxic conditions with redox values more negative in the highly contaminated site, which was also characterized by higher biopolymeric carbon content (most of all lipids), lower C/N ratios and generally higher diffusive fluxes, which could result in a higher release of contaminants. A great difference was observed between diffusive and in situ benthic fluxes suggesting the enhancing of fluxes by bioturbation and the occurrence of biogeochemically important processes at the sediment-water interface. The multi-contamination of both inorganic and organic pollutants, in the sediments of the Mar Piccolo of Taranto (declared SIN in 1998), potentially transferable to the water column and to the aquatic trophic chain, is of serious concern for its ecological relevance, also considering the

  9. Spatial Variability of Benthic-Pelagic Coupling in an Estuary Ecosystem: Consequences for Microphytobenthos Resuspension Phenomenon

    Science.gov (United States)

    Ubertini, Martin; Lefebvre, Sébastien; Gangnery, Aline; Grangeré, Karine; Le Gendre, Romain; Orvain, Francis

    2012-01-01

    summer than in spring, in turn suggesting an important role of macrofauna bioturbation and filter feeding (Cerastoderma edule). PMID:22952910

  10. 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

  11. 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.

  12. Subtropical denudation rates of granitic regolith along a hill ridge in Longnan, SE China derived from cosmogenic nuclide depth-profiles

    Science.gov (United States)

    Cui, Li-Feng; Liu, Cong-Qiang; Xu, Sheng; Zhao, Zhi-Qi; Liu, Tao-Ze; Liu, Wen-Jing; Zhang, Zhuo-Jun

    2016-03-01

    The denudation rates of granitic regolith are essential to our understanding of the geomorphic changes and landscape evolution of a region and for soil resource management. We present denudation rates derived from four regolith profiles along a granitic slope in Longnan, southeastern China, using depth profiles of in-situ produced cosmogenic 10Be and 26Al. The concentration ranges of 10Be, 26Al, and 26Al/10Be ratio were 2.98 × 104-1.72 × 105 atoms/g, 2.18 × 105-1.12 × 106 atoms/g, and 6.07-7.50, respectively. Analysis of the results shows that the surface-lowering rates are 19 ± 3, 41 ± 4, 47 ± 4, 22 ± 3 m/Ma for the four profiles from the foot of the hill to the top along the hillslope. The mean denudation rate for the four profiles is ∼30 m/Ma. This rate is lower than that derived by other methods in nearby areas and also lower than the mean global denudation rate in basins deduced from 10Be levels in river sediment; this suggests an unevenness of the erosion process on a basin scale. The denudation rate at the ridge is twice that estimated for the summit and the foothill, indicating that the hillslope has not reached its steady state. Thus, the slopes below the ridge may become smoother and the ridge sharper in the long-term landscape evolution. The difference in topography may account for the variance among the profiles. In addition, bioturbation may have contributed to the lower concentration in the surface layer at the foot of the hill, producing a higher denudation rate than the average for the basin. The concentration of insoluble element Zr in the soil surface layer and fresh bedrock suggests that chemical weathering accounts for about one third of the denudation rate.

  13. 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.

  14. 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.

  15. 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.

  16. Changes of soil pore system due to soil macrofauna: an experimental approach to study the contribution of different taxa

    Science.gov (United States)

    Gargiulo, Laura; Buscemi, Gilda; Mele, Giacomo; Terribile, Fabio

    2015-04-01

    Soil fauna contributes to the ecosystem functioning, for example, by means of its direct influence on soil structure which modifies the physical environment of the microbial community. Changes in habitat structure due to soil fauna activities can influence resource availability, species' abundances, and community composition of soil microorganisms. X-ray tomography has been increasingly used to obtain precise and non-destructive analysis mostly of the macroporosity resulting from earthworm activity in repacked soil cores. However also other macrofauna species contribute in different manner and extent to the modification of soil pore system, and then to the soil functioning, by means of their burrows and bioturbation activity. In this work we have developed an experimental approach based on the use of repacked soil mesocosms specifically constructed for the purpose of distinguish separately the contribution to soil structure changes of different organisms naturally present in field or inoculated in laboratory. Six different orders of macrofauna were studied and after four weeks of fauna activity the cores were imaged using a medical X-ray tomograph. Three-dimensional image processing was used in order to obtain 3D reconstructions and preliminary analysis of the identified biopores. In addition to the earthworms (Haplotaxida, genus Lombricus), among the studied taxa, Embioptera showed the most intense burrowing activity, while Coleoptera larvae (sp. Elater sanguineus) and Julida (class Diplopoda) produced the thickest pore network in our mesocosms. The used experimental approach showed a promising potential to provide new useful information about the widely differentiated contribution of many types of macrofauna to the modification of soil pore system.

  17. Effects of antagonistic ecosystem engineers on macrofauna communities in a patchy, intertidal mudflat landscape

    Science.gov (United States)

    Eklöf, J. S.; Donadi, S.; van der Heide, T.; van der Zee, E. M.; Eriksson, B. K.

    2015-03-01

    Ecosystem engineers are organisms that strongly modify abiotic conditions and in the process alter associated communities. Different types of benthic ecosystem engineers have been suggested to facilitate different communities in otherwise similar marine environments, partly because they alter sediment conditions in contrasting ways. However, most studies testing this hypothesis have either not manipulated the presence of engineers, or have transplanted engineers into areas already dominated by other engineers, which limits the ability to assess the relative engineering effects. Here we combined a field survey and a field experiment to investigate if two contrasting ecosystem engineers - the sediment-stabilizing seagrass Zostera noltei and the bioturbating lugworm Arenicola marina - facilitate different macrofauna communities. The study was performed in a sheltered mudflat area of the eastern Dutch Wadden Sea, where seagrasses and lugworms form a mosaic of spatially alternating seagrass-dominated elevations (hummocks) and lugworm-dominated depressions (hollows). Results showed that seagrasses facilitated some organisms (mainly attached epifauna) while lugworms facilitated others (primarily burrowing infauna), generating distinctly different macrofauna communities in hummocks and hollows. However, seagrasses had a much stronger effect on the macrofauna communities than lugworms, and competitively excluded lugworms. This contrasts with results from similar studies in hydrodynamically more exposed sand flats, where lugworms instead dominate communities and exclude seagrass. We therefore propose that effects of ecosystem engineering (acting primarily on a local scale) and variation in abiotic conditions (acting on larger scales, e.g., hydrodynamic gradients along the Dutch coastline) strongly interact to dictate the distribution and fitness of engineering species, and indirectly, the diversity and structure of associated benthic communities.

  18. Modeling the gopher-meadow eco-geomorphic system on montane hillslopes

    Science.gov (United States)

    Winchell, E. W.; Doak, D. F.; Anderson, R. S.

    2013-12-01

    On montane hillslopes of Colorado's Front Range, the transport of soil by gophers can dominate the modern geomorphic system in meadows. Qualitative observations reveal that gophers prefer to forage in meadows over forests, that seedling roots are consumed by gophers, and that trees commonly occupy the rocky crests of hills overlooking open meadow hillslopes. This motivates a numerical model of gopher-mediated transport of soil and the long-term evolution of the coupled ecological-geomorphic system through quantitative observations from a manipulative experiment on meadow-centered plots in the Boulder Creek CZO in the Colorado Front Range montane forest. The ecological and geomorphic processes in the coupled system we wish to model must include: seedling establishment and damage, gopher tunneling geometries and resulting mound generation, mound material transport driven by rain and hail and by ungulate trampling, vegetative lock-down of mound material, and resulting changes in the soil depth and rockiness of the landscape. We must therefore have algorithms to capture the feedback mechanisms between gopher activity and the growth and potential death of trees, the casting of seeds and their likelihood of germination, and the spatial distribution of plants. The ecological component interacts with the soils/critical zone layer through feedbacks that include the dependence of gopher activity on root density, depth, and size, undergrowth availability, and the dependence of the rate of change of soil thickness on gradients in gopher-mediated transport. Results of a preliminary cellular automaton model which captures the essence of these geomorphic-ecological feedbacks can readily address the role of gophers in limiting the encroachment of trees into meadow patches. The bioturbation of the meadows, and the downslope transport of soil within them, is much more efficient than that in the forest, which sees little to no gopher activity. These geomorphic transport hotspots will

  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. Metal/metalloid accumulation/remobilization during aquatic litter decomposition in freshwater: a review.

    Science.gov (United States)

    Schaller, Jörg; Brackhage, Carsten; Mkandawire, Martin; Dudel, E Gert

    2011-11-01

    The focus of this article is to combine two main areas of research activities in freshwater ecosystems: the effect of inorganic pollutants on freshwater ecosystems and litter decomposition as a fundamental ecological process in streams. The decomposition of plant litter in aquatic systems as a main energy source in running water ecosystems proceeds in three distinct temporal stages of leaching, conditioning and fragmentation. During these stages metals and metalloids may be fixed by litter, its decay products and the associated organisms. The global-scale problem of contaminated freshwater ecosystems by metals and metalloids has led to many investigations on the acute and chronic toxicity of these elements to plants and animals as well as the impact on animal activity under laboratory conditions. Where sorption properties and accumulation/remobilization potential of metals in sediments and attached microorganisms are quite well understood, the combination of both research areas concerning the impact of higher trophic levels on the modification of sediment sorption conditions and the influence of metal/metalloid pollution on decomposition of plant litter mediated by decomposer community, as well as the effect of high metal load during litter decay on organism health under field conditions, has still to be elucidated. So far it was found that microbes and invertebrate shredder (species of the genera Gammarus and Asellus) have a significant influence on metal fixation on litter. Not many studies focus on the impact of other functional groups affecting litter decay (e.g. grazer and collectors) or other main processes in freshwater ecosystems like bioturbation (e.g. Tubifex, Chironomus) on metal fixation/release. PMID:21907393

  1. 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.

  2. 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.

  3. Diatom Surface Sediment Assemblages from the Bering Sea Shelf: a Tossed Salad or Faithful Recorder of 50 Years of Environmental Change?

    Science.gov (United States)

    Caissie, B.; Brigham-Grette, J.; Kanamaru-Shinn, K.

    2010-12-01

    Recent environmental change in the Bering Sea includes a shift from the negative to positive phase of the Pacific Decadal Oscillation in 1976/77, a secondary shift in sea level pressure and sea surface temperatures in 1998, increasing sea surface temperatures, an earlier spring, an increase in the number of days that sea ice is present along the shelf-slope break, and a decrease in the number of days that sea ice is present in the Chukchi Sea and Arctic Ocean. These physical changes have manifest biological changes such as a northward migration of invertebrates and fish from the southern Bering Sea and shifts in the timing and duration of sea-ice related primary productivity and the spring bloom. We aim to see if diatom sediment assemblages are faithful recorders of these ecological changes in the Bering Sea or if bioturbation has essentially mixed today’s rapid change down core such that the signal is either muted or no longer apparent. Six continental shelf areas were examined in the Bering Sea ranging from northeast of St. Lawrence Island to the shelf-slope break in the south-central Bering Sea. Diatom assemblages from core tops collected as part of the PROBES program in the 1960s were compared to core tops taken nearby (7 m) multi-year ice so their decline may be related to the decrease in multi-year ice over the past 30 years. Additionally, in most cases, species diversity has declined over the past 50 years with Fragilariopsis oceanica and Fragilariopsis cylindrus accounting for a greater percentage of the sediment assemblages today. These two species are collectively considered indicators of seasonal sea ice; their relative abundance peaks when ice is present for 5 months per year. Ongoing down core analyses in these six areas will further reveal the nature of these assemblage changes.

  4. 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.

  5. 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

  6. 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

  7. 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)

  8. 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

  9. 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

  10. Gulf of Alaska Cryosphere and Paleoceanography in the Neogene: IODP Expedition 341 Southern Alaska

    Science.gov (United States)

    Jaeger, J. M.; Gulick, S. P. S.

    2014-12-01

    Neogene climate reflects the transition into a colder, more variable world dominated by the onset and intensification of major Northern Hemisphere glaciations. Integrated Ocean Drilling Program Expedition 341 recovered a cross-margin transect of pelagic facies from this subarctic, high-nutrient, low-chlorophyll modern setting to glacigenic material from the exhuming coastal mountains. The recovered sedimentary record extends from the late Miocene through the Pleistocene/Holocene. Shipboard results indicate a ~doubling in sediment accumulation rates at ~2.56 Ma at the deep-water distal Site U1417, which is interpreted as the onset of significant glacial coverage in the St. Elias Range after the Pliocene-Pleistocene transition, resulting in the start of deposition in the Surveyor Fan. At all sites, clast-rich mud and/or diamict are prevalent in the Pleistocene, indicating the persistent transport of glacigenic sediment by ice, iceberg or sea-ice rafting. An unanticipated observation is the often sharp transitions between these ice-dominated facies and more biogenic-rich, often bioturbated, muddy lithologies that might be related to increased biological productivity, enhanced nutrient supply, and/or decreased input of terrigenous sediments. All sites contained variable preservation of biosiliceous and calcareous microfossils that indicate dynamic water column productivity and/or variable sediment geochemistry from the late Miocene to the present. At deep-water sites, strong variations in environmentally sensitive planktic foraminifera, radiolarians, and diatoms record alternating warming and cooling intervals during the last 1.2 Ma. At Site U1417, planktic foraminifera and radiolarian taxa abundances indicate cooler conditions in the Pleistocene relative to the Pliocene/late Miocene. Especially high sedimentation rates during the late Pleistocene hold promise for future studies related to suborbital-scale variability in paleoproductivity and glacigenic sedimentation.

  11. 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.

  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. 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

  14. 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

  15. 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.

  16. Caesium-137 distribution, inventories and accumulation history in the Baltic Sea sediments

    International Nuclear Information System (INIS)

    The Baltic Sea is susceptible to pollution by hazardous substances due to limited water exchange, shallowness, and the large catchment area. Radionuclides, particularly 137Cs, are one of the most hazardous anthropogenic substances present in the Baltic environment. This study was conducted to present 137Cs present contamination that should further be a subject of reliable monitoring when the new Nuclear Power Plant is put into operation in the northern Poland. The sea-wide, up to date distribution of 137Cs activities and inventories in the Baltic Sea bottom sediments are presented. The 137Cs activity concentrations were measured in 30 cm long sediment cores collected at 22 sampling stations. Sediment accumulation rates were quantified by 210Pb geochronology to follow the history of 137Cs accumulation. The 137Cs inventories and fluxes were calculated. Most of the Baltic Sea sediments accumulated 137Cs in the range from 750 to 2675 Bq m−2. The Bothnian Bay is severely contaminated by 137Cs with inventories up to 95,191 Bq m−2. This region is moreover characterized by extremely large patchiness of 137Cs inventories. The 137Cs annual fluxes are highest at the two stations located at the Bothnian Bay (342 Bq m−2 and 527 Bq m−2) due to large Chernobyl 137Cs contamination of that region and high sediment accumulation rates. When these stations are excluded, the recent, annual mean value of 137Cs load to the Baltic Sea deposits is 38 ± 22 Bq m−2. The distribution of radio-caesium inventories over the Baltic Sea nowadays reflects the pattern of Chernobyl contamination. The radio-caesium deposited in surface sediments is not permanently buried, but may be resuspended and redeposited by currents, bioturbation or anthropogenic activities. -- Highlights: • 137Cs contamination in the Baltic Sea was studied before the new NPP is put into operation. • Bothnian Sea sediments are severely contaminated by 137Cs (inventories up to 95,191 Bq m−2). • Most of the

  17. 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

  18. Earthworm-induced carboxylesterase activity in soil: Assessing the potential for detoxification and monitoring organophosphorus pesticides.

    Science.gov (United States)

    Sanchez-Hernandez, Juan C; Notario del Pino, J; Domínguez, Jorge

    2015-12-01

    Soil enzyme activities are attracting widespread interest due to its potential use in contaminant breakdown, and as indicators of soil deterioration. However, given the multiple environmental and methodological factors affecting their activity levels, assessment of soil pollution using these biochemical endpoints is still complex. Taking advantage of the well-known stimulatory effect of earthworms on soil microbes, and their associated enzyme activities, we explored some toxicological features of carboxylesterases (CbEs) in soils inoculated with Lumbricus terrestris. A microplate-scale spectrophotometric assay using soil-water suspensions was first optimized, in which kinetic assay parameters (Km, Vmax, dilution of soil homogenate, and duration of soil homogenization) were established for further CbE determinations. Optimal conditions included a soil-to-water ratio of 1:50 (w/v), 30-min of shaking, and 2.5mM of substrate concentration. As expected, CbE activity increased significantly in soils treated with L. terrestris. This bioturbed soil was used for exploring the role of CbE activity as a bioscavenger for organophosphorus (OP) pesticides. Soil treated with two formulations of chlorpyrifos revealed that CbE activity was a significant molecular sink for this pesticide, reducing its impact on soil microbial activity as shown by the unchanged dehydrogenase activity. Dose-dependent curves were adjusted to an exponential kinetic model, and the median ecological dose (ED50) for both pesticide formulations was calculated. ED50 values decreased as the time of pesticide exposure increased (14 d-ED50s=20.4-26.7 mg kg(-1), and 28 d-ED50s=1.8-2.3 mg kg(-1)), which suggested that chlorpyrifos was progressively transformed into its highly toxic metabolite chlorpyrifos-oxon, but simultaneously was inactivated by CbEs. These results were confirmed by in vitro assays that showed chlorpyrifos-oxon was a more potent CbE inhibitor (IC50=35.5-4.67 nM) than chlorpyrifos (0.41-0.84

  19. Pb and Zn and the onset of Anthropocene in floodplain sediments: How and why to quantify weak contamination?

    Science.gov (United States)

    Matys Grygar, T.; Novakova, T.; Lukešová, V.; van der Perk, M.; Middelkoop, H.; Macklin, M. G.

    2012-04-01

    In our laboratory we work on the quantification of heavy metal pollution in fluvial sediments of which sedimentological description, facial assignment, post-depositional stability and dating are incomplete or missing. Without such fundamental knowledge the only robust information is apparently the absolute concentration of heavy metals. Due to local geochemical differences and heavy metal sorting by fluvial transport and pedogenesis, the actual level of anthropogenic contamination is usually considered inconclusive when the enrichment factor EFmissing when only sediment from cores with a small diameter is available. We cannot do extensive OSL, while 210Pb and 137Cs dating can cover decades to a century and 14C datable material is rather rarely caught. Small-scale sedimentological features in floodplain soils are mostly destroyed by bioturbation. There are no large outcrops like sand pits in most of the studied floodplains and hence their architecture is unknown. Erosional banks are exposed to a variety of chemical and sedimentological disturbances and are covered by levee sediments of variable thickness, which devaluates them as sediment archives. We often hardly know the past river channel network, which complicated even simple facial assignment of the sediments from a drill core. The river style (number of channels and their lateral stability) has been changed due to human action in the studied period (it is a common activity in the Anthropocene) but these changes are rather rarely covered by sufficiently detailed maps. We must hence make an unpleasant choice: either study those few rivers of which complete information has already been gathered, or work on any river but simplify our task and search for only "simple" and robust information, which is the EF of overbank fines during the last several centuries. The EF for each sediment sample is a perfectly defined numerical value for a given heavy metal. We propose how to select suitable floodplain profiles and

  20. Spatiotemporal distribution of {sup 137}Cs in the sea surrounding Japanese Islands in the decades before the disaster at the Fukushima Daiichi Nuclear Power Plant in 2011

    Energy Technology Data Exchange (ETDEWEB)

    Watabe, Teruhisa, E-mail: watabe@kaiseiken.or.jp; Oikawa, Shinji; Isoyama, Naohiko; Suzuki, Chiyoshi; Misonoo, Jun; Morizono, Shigemitsu

    2013-10-01

    The historic spatiotemporal distribution of {sup 137}Cs in the seawaters and sea-floor sediments adjacent to nuclear power plants in Japan are summarized, using data obtained over a period of time more than 20 years prior to the disaster at the Fukushima Daiichi Nuclear Power Plant in 2011. Relatively uniform distributions of {sup 137}Cs were observed both in the surface seawaters (1 m in depth) and in deeper seawaters (10 to 30 m above the seabed and ranging from tens to hundreds of meters in depth) independent of the geographical position, although lower concentrations were observed in significantly deeper bottom seawaters. Conversely, there were wide variations in {sup 137}Cs levels between sediments, such that higher {sup 137}Cs concentrations were observed in the deeper sampling locations. A mathematical model describing the successive transfer of {sup 137}Cs from surface waters through deeper waters to sediments suggested that the transfer rate of {sup 137}Cs from deep water to the sediments, and the loss rate from bottom sediments, were both greater than the transfer rate from surface water to deeper water. It was found that the calculated regression lines for {sup 137}Cs depletion rates over time for surface waters, deeper waters, and sediments were approximately parallel when plotted on a semi-logarithmic coordinate system, regardless of the sampling location. A radionuclide depletion half-life was calculated to be 4 months to 16 years with the geometric mean of 2.22 y for the sediments in the Fukushima region, suggesting that nuclear contamination will be remediated over time through sediment redistribution processes such as remobilization, bioturbation, and migration due to sea currents. - Highlights: • We review data of monitoring in the sea over more than 20 years before 2011. • We develop a simplified model on the vertical transfer of {sup 137}Cs in the sea. • Half-lives of {sup 137}Cs in surface waters are larger than those in deeper samples.

  1. Spatiotemporal distribution of 137Cs in the sea surrounding Japanese Islands in the decades before the disaster at the Fukushima Daiichi Nuclear Power Plant in 2011

    International Nuclear Information System (INIS)

    The historic spatiotemporal distribution of 137Cs in the seawaters and sea-floor sediments adjacent to nuclear power plants in Japan are summarized, using data obtained over a period of time more than 20 years prior to the disaster at the Fukushima Daiichi Nuclear Power Plant in 2011. Relatively uniform distributions of 137Cs were observed both in the surface seawaters (1 m in depth) and in deeper seawaters (10 to 30 m above the seabed and ranging from tens to hundreds of meters in depth) independent of the geographical position, although lower concentrations were observed in significantly deeper bottom seawaters. Conversely, there were wide variations in 137Cs levels between sediments, such that higher 137Cs concentrations were observed in the deeper sampling locations. A mathematical model describing the successive transfer of 137Cs from surface waters through deeper waters to sediments suggested that the transfer rate of 137Cs from deep water to the sediments, and the loss rate from bottom sediments, were both greater than the transfer rate from surface water to deeper water. It was found that the calculated regression lines for 137Cs depletion rates over time for surface waters, deeper waters, and sediments were approximately parallel when plotted on a semi-logarithmic coordinate system, regardless of the sampling location. A radionuclide depletion half-life was calculated to be 4 months to 16 years with the geometric mean of 2.22 y for the sediments in the Fukushima region, suggesting that nuclear contamination will be remediated over time through sediment redistribution processes such as remobilization, bioturbation, and migration due to sea currents. - Highlights: • We review data of monitoring in the sea over more than 20 years before 2011. • We develop a simplified model on the vertical transfer of 137Cs in the sea. • Half-lives of 137Cs in surface waters are larger than those in deeper samples. • Variations of 137Cs concentration are parallel on

  2. 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

  3. The use of 210Pb and 137Cs in environmental studies

    International Nuclear Information System (INIS)

    The use of natural radioactivity in environmental studies has proven a very powerful tool to determine the dynamics of both natural and antrophogenic processes in our environment. The use of 14C in archaeology and past climate studies has led to many scientific discoveries (the shroud of Turin and Utze the ice-man from Austria are two examples). The use of the 238U-decay series is of at least equal value to studies in archaeology and of past climates. Some of the Isotopes studied supplement 14C (which is limited to 40,000 years) data and allow dating of samples formed up to 500,000 years ago (see McCullough, this book of abstracts, pages 19-23), others can be utilised to date very young sediments, which can't be dated by 14C.The so-called 210Pb dating method has been used over the past 3 decades to date recent sediment. The method uses the disequilibrium in the 238U decay chain, caused by the escape of the intermediate daughter 222Rn, a noble gas, from the earth's crust. In the atmosphere the 222Rn decays via short-lived daughter isotopes to 210Pb. This 210Pb with a very convenient half-life of 22,3 years decays to stable 206Pb. By measuring the surface activity of a sediment core and subsequent samples at regular intervals, a chronology for the sediment core can be established (relative to the surface). In addition to 210Pb dating one could analyse the samples for l37Cs to establish an independent chronology based on a pulse of radioactive Caesium. The pulse of 137Cs originates from the atmospheric atomic-bomb test of the early sixties. The maximum of Caesium activity found in a core should correspond to the height of the tests (approximately 1963 in the Northern hemisphere). A combination of the two dating methods often leads to more reliable results in the chronology. Another use of 137Cs is to test if the sediment has been subject to bio-turbation or other mixing. In the case of disturbance the proper pulse of Caesium would be smeared out and would not look

  4. Dynamic modelling of radionuclide uptake by Fukushima coastal biota - Dynamic modelling of radionuclide uptake by marine biota: application to Fukushima assessment

    International Nuclear Information System (INIS)

    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 (Kd). 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 131I, 134Cs, 137Cs and 90Sr 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 Kd 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 external doses to marine biota using a

  5. 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

  6. 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.

  7. Benthic response to shellfish farming in Thau lagoon: Pore water signature

    Science.gov (United States)

    Metzger, E.; Simonucci, C.; Viollier, E.; Sarazin, G.; Prévot, F.; Jézéquel, D.

    2007-04-01

    Vertical distributions of dissolved species across the sediment-water interface (SWI), including major cations (sodium, potassium, magnesium, calcium), minor cations (lithium, strontium, barium), redox sensitive species (dissolved manganese, iron, sulfate, sulfide, ammonium) and other chemical parameters (pH, alkalinity, soluble reactive phosphorous, dissolved silica) were studied in a Mediterranean lagoon used for intensive shellfish farming. In order to quantify the impact of this activity on diagenetic processes and the influence of seasonal changes, two stations contrasted with respect to organic carbon fluxes were sampled in Thau lagoon from March 2001 to August 2002 during four field campaigns in winter, spring, summer and fall. Well-defined layers enriched with redox sensitive species were observed following the conventional sequence of early diagenetic reactions. However, differences were observed between both stations in depths and thickness layers. Concentration gradients extended down to more than 92 cm depth at the central position of the lagoon (station C4 - 8 m depth) and down to 40 cm depth inside shellfish farming zones (station C5 - 9 m depth). Station C4 showed an unusual diagenetic signature: sharp dissolved oxygen, iron, nitrate and manganese gradients existed at the SWI but gradients of dissolved sulfide and alkalinity as well as other parameters (dissolved silica, Ba, etc.) were recorded only from 25 to 30 cm depth downward. Seasonal changes were observed in pore water composition as deep as 30-50 cm in station C4 (only 15 cm in station C5). The center of the lagoon is not directly subjected to biodeposits deriving from shellfish activity. Isotopic and bioturbation data allowed to rule out a reworking of the sediment deeper than a few centimeters. In addition to organic content of the sediment, physical parameters were likely to induce the 10-20 cm gap between dissolved iron and sulfide profile as well as the higher vertical extent of

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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.

  13. 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

  14. Shallow Water Euxinia and Density Stratification of the Cenomanian/Turonian Western Interior Seaway in Texas

    Science.gov (United States)

    Wehner, M.; Pope, M. C.; Tice, M. M.; Gardner, R.; Donovan, A. D.; Staerker, S.; Lyon, T.; Maulana, I.; Pramudito, A.; Xu, G.; Zeng, Z.

    2014-12-01

    The Eagle Ford Group was deposited at the south and east side of the Western Interior Seaway (WIS). These sediments contain evidence of anoxia and shallow-water deposition (between storm-wave and fair weather wave-base) in the proximal deposits at Lozier Canyon and Antonio Creek (LC/AC). Shallow-water (above storm wave-base) depositional conditions are mostly based on the suite of primary sedimentary structures that includes: hummocky cross-stratification (HCS), swaley cross-stratification (SCS), symmetric ripples, gutter casts and shell lags. These occur in outcrop and support the interpretation that LC/AC is the most proximal location relative to other study locations. At Hot Springs in Brewster County, Texas, sedimentary structures are limited to shell lags, a few symmetric ripples and low-angle laminations. This is consistent with the distal expression of storm deposits. The primary sedimentary structures from the core from the subsurface in McMullen County, south Texas, are limited to those of low-energy currents, scouring, and reworking, which could indicate it is in the distally steepened portion of the carbonate ramp on which Eagle Ford Groups are deposited. Pelagic foraminifera are the most microfossil and benthic foraminifera only occur in the Upper Eagle Formation at LC/AC. Molybdenum was also used as a proxy for occurrence and persistence of a sulfer-reducing zone. The geochemical data from the subsurface core suggests persistence of anoxia throughout its depositional history. At LC/AC, molybdenum is elevated (up to 5-6 times average shale value) and bioturbation in these zones is limited to the surfaces of symmetric ripples, suggesting that oxygenation events were brief and occurred only immediately after storm events. This is consistent with the hypothesis that the HCS, SCS, and symmetric ripples were caused by storms and temporarily mixed the ocean in a normally stratified water column. At LC/AC, the water column became persistently oxic from the

  15. 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

  16. 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

  17. 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

  18. 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.

  19. 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

  20. 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

  1. 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

  2. High‐throughput collagen fingerprinting of intact microfaunal remains; a low‐cost method for distinguishing between murine rodent bones

    Science.gov (United States)

    Gu, Muxin; Shameer, Sanu; Patel, Soyab; Chamberlain, Andrew T.

    2016-01-01

    Rationale Microfaunal skeletal remains can be sensitive indicators of the contemporary ecosystem in which they are sampled and are often recovered in owl pellets in large numbers. Species identification of these remains can be obtained using a range of morphological criteria established for particular skeletal elements, but typically dominated by a reliance on cranial characters. However, this can induce biases under different environmental and taphonomic conditions. The aim of this research was to develop a high‐throughput method of objectively identifying rodent remains from archaeological deposits using collagen fingerprinting, most notably the identification of rats from other myomorph rodents as a means to identify disturbances in the archaeofauna through the presence of invasive taxa not contemporary with the archaeological deposits. Methods Collagen was extracted from complete microfaunal skeletal remains in such a manner as to leave the bones morphologically intact (i.e., weaker concentration of acid than previously used over shorter length of time). Acid‐soluble collagen was then ultrafiltered into ammonium bicarbonate and digested with trypsin prior to dilution in the MALDI matrix and acquisition of peptide mass fingerprints using a matrix‐assisted laser desorption/ionisation time‐of‐flight (MALDI‐TOF) mass spectrometer. Results Collagen fingerprinting was able to distinguish between Rattus, Mus, Apodemus and Micromys at the genus level; at the species level, R. rattus and R. norvegicus could be separated whereas A. flavicollis and A. sylvaticus could not. A total of 12,317 archaeological microvertebrate samples were screened for myomorph signatures but none were found to be invasive rats (Rattus) or mice (Mus). Of the contemporary murine fauna, no harvest mice (Micromys) were identified and only 24 field mouse (Apodemus) discovered. Conclusions As a result, no evidence of recent bioturbation could be inferred from the faunal remains of these

  3. 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.

  4. 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

  5. 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.

  6. 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

  7. A terrestrial vegetation turnover in the middle of the Early Triassic

    Science.gov (United States)

    Saito, Ryosuke; Kaiho, Kunio; Oba, Masahiro; Takahashi, Satoshi; Chen, Zhong-Qiang; Tong, Jinnan

    2013-06-01

    Land-plant productivity was greatly reduced after the end-Permian mass extinction, causing a pronounced "coal gap" worldwide during the Early Triassic. Newly obtained organic geochemistry data from the Chaohu area, south China, indicated an abrupt and profound terrestrial vegetation change over the middle part of the Early Triassic Smithian-Spathian (S-S) interval. Herbaceous lycopsids and/or bryophytes dominated terrestrial vegetation from Griesbachian to Smithian times. The terrestrial ecosystem underwent an abrupt change, and woody conifers became dominant over the S-S interval. Several important biomarkers, namely retene, simonellite, and dehydroabietane (with multiple sources: conifer, lycopsid, and/or herbaceous bryophyte), were relatively abundant during Griesbachian, Dienerian, and Smithian times. The relatively low C/N ratio values during the Griesbachian-Smithian interval indicate that these biomarkers were likely sourced from herbaceous lycopsids and/or bryophytes. The extremely abundant conifer-sourced pimanthrene, combined with relatively high C/N ratio values, suggested the recovery of woody conifers after the S-S boundary. The new data revealed that the switch from herbaceous vegetation to woody coniferous vegetation marked a terrestrial plant recovery, which occurred globally within 3 million years after the end-Permian crisis rather than at a later date estimated in previous studies. In Chaohu, the S-S terrestrial event was marked by a reappearance of woody vegetation, while the S-S marine event was marked by an increase in ichnodiversity, trace complexity, burrow size, infaunal tiering level, and bioturbation level, and a possible intense upwelling event indicated by the extended tricyclic terpane ratios (ETR). Coeval vegetation changes with comparable patterns have also been documented in Europe and Pakistan based on palynologic studies. The S-S boundaries in Asia and Europe are associated with a positive δ13C excursion, the rebound of woody

  8. {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

  9. 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

  10. Distribution, Character, and Importance of Sedimentary Furrows in South-Central Long Island Sound

    Science.gov (United States)

    Poppe, L.; Doran, E.; Moser, M.; Forfinski, N.; Stewart, H.; Gardner, U.; Keene, J.; Christman, E.; Ackerman, S.

    2005-05-01

    The U.S. Geological Survey, in cooperation with the Connecticut Department of Environmental Protection and the National Oceanic and Atmospheric Administration, is producing detailed geologic interpretations of the sea floor in Long Island Sound to improve our understanding of the processes that control the complex distributions of sedimentary environments and benthic habitats. Although the deeper waters of the south-central Sound are generally characterized by relatively weak bottom currents and by depositional conditions, multibeam data reveal the presence of sedimentary furrows. These erosional bedforms occur in fine-grained cohesive sediments and cover an elongate east-west trending area (~80 km2) that lies approximately 5 km off Herod Point, NY, in water depths of 31-41 m. The furrows are irregularly spaced, trend east-northeast, average 9 m wide and 0.4 m deep, and can exceed 1.9 km long. Although most of the furrows appear to taper out gradually, some furrows show a "tuning fork" joining pattern. Most of these junctions open toward the east, indicating net westward sediment transport, but a few junctions open westward suggesting that the tidal regime is important to furrow formation and that the furrows can form when water flows in either direction. The sedimentary furrows in south-central Long Island Sound, which are similar to those we have previously described along the Connecticut side of the estuary, form under recurring directionally stable tidal currents, constrained by the elongate geometry and regional bathymetry of the Sound. These conditions, in turn, produce the secondary helical and turbulent flow patterns conducive to the formation of erosional furrows. Concurrently, bioturbation by crabs not only suspends sediment, but also nutclam shells and other coarse biogenic debris, which are aligned by the secondary flow and abrade the furrows as they saltate in the oscillating tides. Through resuspension due to biological activity and the subsequent

  11. 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

  12. 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

  13. Microbial mercury transformations in marine, estuarine and freshwater sediment downstream of the Idrija Mercury Mine, Slovenia

    International Nuclear Information System (INIS)

    The Idrija Mine, the second largest Hg mine in the world, ceased operation in 1995, but still delivers large quantities of Hg downstream including into the northern Adriatic Sea, 100 km away. Transformation of Hg species in sediment in sites over 60 km from the mine, including marine sites in the Adriatic Sea, was measured to determine the ability of the system to transform and mobilize Hg and to produce methylmercury (MeHg). Cores from a freshwater impoundment, a brackish estuarine site, and three marine sites in the Gulf of Trieste were sectioned anaerobically, and Hg methylation and MeHg demethylation activities determined using radio-techniques (203Hg for methylation and 14C-MeHg for demethylation). Total and dissolved Hg and MeHg were determined as were other geochemical parameters. In addition, rates of SO4 reduction were determined in marine sediment using a 35S technique. Mercury was readily methylated and demethylated at all sites. Marine sediment was investigated in winter and summer with rates of Hg transformation and SO4 reduction corresponding only in winter. Methylation of Hg in summer displayed subsurface peaks that may have been influenced by bioturbation. Total Hg and MeHg were most abundant in the freshwater, estuarine, and near-shore marine sites, but dissolved pore water Hg and MeHg were highest in the estuarine region where S cycling appeared ideal for the mobilization of Hg. The impoundment sediment also seemed to be a 'hotspot' of Hg transformations. MeHg demethylation occurred via the oxidative demethylation pathway (CO2 produced from MeHg), except in surficial sediment offshore in the Gulf during winter, where sediment was more oxidizing and significant amounts of CH4 were liberated during MeHg degradation via reductive demethylation. The CH4 formation was likely due to an increased influence from the expression of MeHg degradative enzymes encoded by the mer detoxification bacterial genetic system. The freshwater site also liberated CH4

  14. 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

  15. 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

  16. 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

  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. 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.

  19. 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.

  20. Postglacial sedimentary processes on the Storfjorden and Kveithola trough mouth fans: Significance of extreme glacimarine sedimentation

    Science.gov (United States)

    Lucchi, R. G.;