WorldWideScience

Sample records for deep ocean sediments

  1. Geotechnical properties of deep-ocean sediments: a critical state approach

    International Nuclear Information System (INIS)

    Ho, E.W.L.

    1988-11-01

    The possible disposal of high-level radioactive waste using the sediments of the deep-ocean floor as repositories has initiated research to establish an understanding of the fundamental behaviour of deep-ocean sediments. The work described in this thesis consisted of a series of triaxial stress path tests using microcomputer controlled hydraulic triaxial cells to investigate the strength and stress-strain behaviour for mainly anisotropically (K o ) consolidated 'undisturbed' (tubed) and reconstituted specimens of deep-ocean sediments taken from two study areas in the North Atlantic Ocean. The test results have been analysed within the framework of critical state soil mechanics to investigate sediment characteristics such as the state boundary surface, drained and undrained strength and stress-strain behaviour. While marked anisotropic behaviour is found in a number of respects, the results indicate that analysis in a critical state framework is as valid as for terrestrial sediments. Differences in behaviour between tubed and reconstituted specimens have been observed and the effect of the presence of carbonate has been investigated. An attempt has been made to develop an elasto-plastic constitutive K o model based on critical state concepts. This model has been found to agree reasonably well with experimental data for kaolin and deep-ocean sediments. (author)

  2. Deep ocean ventilation, carbon isotopes, marine sedimentation and the deglacial CO2 rise

    Directory of Open Access Journals (Sweden)

    C. Heinze

    2011-07-01

    Full Text Available The link between the atmospheric CO2 level and the ventilation state of the deep ocean is an important building block of the key hypotheses put forth to explain glacial-interglacial CO2 fluctuations. In this study, we systematically examine the sensitivity of atmospheric CO2 and its carbon isotope composition to changes in deep ocean ventilation, the ocean carbon pumps, and sediment formation in a global 3-D ocean-sediment carbon cycle model. Our results provide support for the hypothesis that a break up of Southern Ocean stratification and invigorated deep ocean ventilation were the dominant drivers for the early deglacial CO2 rise of ~35 ppm between the Last Glacial Maximum and 14.6 ka BP. Another rise of 10 ppm until the end of the Holocene is attributed to carbonate compensation responding to the early deglacial change in ocean circulation. Our reasoning is based on a multi-proxy analysis which indicates that an acceleration of deep ocean ventilation during early deglaciation is not only consistent with recorded atmospheric CO2 but also with the reconstructed opal sedimentation peak in the Southern Ocean at around 16 ka BP, the record of atmospheric δ13CCO2, and the reconstructed changes in the Pacific CaCO3 saturation horizon.

  3. Earthquakes drive large-scale submarine canyon development and sediment supply to deep-ocean basins.

    Science.gov (United States)

    Mountjoy, Joshu J; Howarth, Jamie D; Orpin, Alan R; Barnes, Philip M; Bowden, David A; Rowden, Ashley A; Schimel, Alexandre C G; Holden, Caroline; Horgan, Huw J; Nodder, Scott D; Patton, Jason R; Lamarche, Geoffroy; Gerstenberger, Matthew; Micallef, Aaron; Pallentin, Arne; Kane, Tim

    2018-03-01

    Although the global flux of sediment and carbon from land to the coastal ocean is well known, the volume of material that reaches the deep ocean-the ultimate sink-and the mechanisms by which it is transferred are poorly documented. Using a globally unique data set of repeat seafloor measurements and samples, we show that the moment magnitude ( M w ) 7.8 November 2016 Kaikōura earthquake (New Zealand) triggered widespread landslides in a submarine canyon, causing a powerful "canyon flushing" event and turbidity current that traveled >680 km along one of the world's longest deep-sea channels. These observations provide the first quantification of seafloor landscape change and large-scale sediment transport associated with an earthquake-triggered full canyon flushing event. The calculated interevent time of ~140 years indicates a canyon incision rate of 40 mm year -1 , substantially higher than that of most terrestrial rivers, while synchronously transferring large volumes of sediment [850 metric megatons (Mt)] and organic carbon (7 Mt) to the deep ocean. These observations demonstrate that earthquake-triggered canyon flushing is a primary driver of submarine canyon development and material transfer from active continental margins to the deep ocean.

  4. Bacterial Diversity in Deep-Sea Sediments from Afanasy Nikitin Seamount, Equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Khandeparker, R.; Meena, R.M.; Deobagkar, D.D.

    Deep-sea sediments can reveal much about the last 200 million years of Earth history, including the history of ocean life and climate. Microbial diversity in Afanasy Nikitin seamount located at Equatorial East Indian Ocean (EEIO) was investigated...

  5. Exploring frontiers of the deep biosphere through scientific ocean drilling

    Science.gov (United States)

    Inagaki, F.; D'Hondt, S.; Hinrichs, K. U.

    2015-12-01

    Since the first deep biosphere-dedicated Ocean Drilling Program (ODP) Leg 201 using the US drill ship JOIDES Resolution in 2002, scientific ocean drilling has offered unique opportunities to expand our knowledge of the nature and extent of the deep biosphere. The latest estimate of the global subseafloor microbial biomass is ~1029cells, accounting for 4 Gt of carbon and ~1% of the Earth's total living biomass. The subseafloor microbial communities are evolutionarily diverse and their metabolic rates are extraordinarily slow. Nevertheless, accumulating activity most likely plays a significant role in elemental cycles over geological time. In 2010, during Integrated Ocean Drilling Program (IODP) Expedition 329, the JOIDES Resolutionexplored the deep biosphere in the open-ocean South Pacific Gyre—the largest oligotrophic province on our planet. During Expedition 329, relatively high concentrations of dissolved oxygen and significantly low biomass of microbial populations were observed in the entire sediment column, indicating that (i) there is no limit to life in open-ocean sediment and (ii) a significant amount of oxygen reaches through the sediment to the upper oceanic crust. This "deep aerobic biosphere" inhabits the sediment throughout up to ~37 percent of the world's oceans. The remaining ~63 percent of the oceans is comprised of higher productivity areas that contain the "deep anaerobic biosphere". In 2012, during IODP Expedition 337, the Japanese drill ship Chikyu explored coal-bearing sediments down to 2,466 meters below the seafloor off the Shimokita Peninsula, Japan. Geochemical and microbiological analyses consistently showed the occurrence of methane-producing communities associated with the coal beds. Cell concentrations in deep sediments were notably lower than those expected from the global regression line, implying that the bottom of the deep biosphere is approached in these beds. Taxonomic composition of the deep coal-bearing communities profoundly

  6. Geotechnical aspects of deep ocean radioactive waste disposal

    International Nuclear Information System (INIS)

    Freeman, T.J.

    1990-01-01

    The methods that might be used to bury radioactive waste in the deep ocean, and their likely effect on the sediment barrier, have been the subject of an international research program performed during the last ten years. This paper reviews the geotechnical aspects of deep ocean disposal and discusses how far the research performed has gone towards providing the information needed to assess this form of disposal. Considerable progress has been made during the course of the international program towards understanding the processes involved in the emplacement of heat generating waste (HGW) into the deep ocean bed and the subsequent interactions between the waste and the sediments. These processes do not appear to have a deleterious effect on the barrier properties of the sediments, and it is concluded that it is likely that HGW could be emplaced in the deep ocean in such a way that the seabed would provide an effective containment for the radionuclides

  7. Bacterial Production and Enzymatic Activities in Deep-Sea Sediments of the Pacific Ocean: Biogeochemical Implications of Different Temperature Constraints

    Science.gov (United States)

    Danovaro, R.; Corinaldesi, C.; dell'Anno, A.

    2002-12-01

    The deep-sea bed, acting as the ultimate sink for organic material derived from the upper oceans primary production, is now assumed to play a key role in biogeochemical cycling of organic matter on global scale. Early diagenesis of organic matter in marine sediments is dependent upon biological processes (largely mediated by bacterial activity) and by molecular diffusion. Organic matter reaching the sea floor by sedimentation is subjected to complex biogeochemical transformations that make organic matter largely unsuitable for direct utilization by benthic heterotrophs. Extracellular enzymatic activities in the sediment is generally recognized as the key step in the degradation and utilization of organic polymers by bacteria and a key role in biopolymeric carbon mobilization is played by aminopeptidase, alkaline phosphatase and glucosidase activities. In the present study we investigated bacterial density, bacterial C production and exo-enzymatic activities (aminopeptidase, glucosidase and phosphatase activity) in deep-sea sediments of the Pacific Ocean in relation with the biochemical composition of sediment organic matter (proteins, carbohydrates and lipids), in order to gather information on organic matter cycling and diagenesis. Benthic viral abundance was also measured to investigate the potential role of viruses on microbial loop functioning. Sediment samples were collected at eight stations (depth ranging from 2070-3100 m) along two transects located at the opposite side (north and south) of ocean seismic ridge Juan Fernandez (along latitudes 33° 20' - 33° 40'), constituted by the submerged vulcanoes, which connects the Chilean coasts to Rapa Nui Island. Since the northern and southern sides of this ridge apparently displayed small but significant differences in deep-sea temperature (related to the general ocean circulation), this sampling strategy allowed also investigating the role of different temperature constraints on bacterial activity and

  8. The oceanic sediment barrier

    International Nuclear Information System (INIS)

    Francis, T.J.G.; Searle, R.C.; Wilson, T.R.S.

    1986-01-01

    Burial within the sediments of the deep ocean floor is one of the options that have been proposed for the disposal of high-level radioactive waste. An international research programme is in progress to determine whether oceanic sediments have the requisite properties for this purpose. After summarizing the salient features of this programme, the paper focuses on the Great Meteor East study area in the Northeast Atlantic, where most oceanographic effort has been concentrated. The geological geochemical and geotechnical properties of the sediments in the area are discussed. Measurements designed to determine the rate of pore water movement through the sediment column are described. Our understanding of the chemistry of both the solid and pore-water phases of the sediment are outlined, emphasizing the control that redox conditions have on the mobility of, for example, naturally occurring manganese and uranium. The burial of instrumented free-fall penetrators to depths of 30 m beneath the ocean floor is described, modelling one of the methods by which waste might be emplaced. Finally, the nature of this oceanic environment is compared with geological environments on land and attention is drawn to the gaps in our knowledge that must be filled before oceanic burial can be regarded as an acceptable disposal option. (author)

  9. Bacterial diversity and biogeography in deep-sea sediments of the South Atlantic Ocean

    DEFF Research Database (Denmark)

    Schauer, Regina; Bienhold, Christina; Ramette, Alban

    2010-01-01

    in 1051 sequences. Phylotypes affiliated with Gammaproteobacteria, Deltaproteobacteria and Acidobacteria were present in all three basins. The distribution of these shared phylotypes seemed to be influenced neither by the Walvis Ridge nor by different deep water masses, suggesting a high dispersal......Microbial biogeographic patterns in the deep sea depend on the ability of microorganisms to disperse. One possible limitation to microbial dispersal may be the Walvis Ridge that separates the Antarctic Lower Circumpolar Deep Water from the North Atlantic Deep Water. We examined bacterial...... communities in three basins of the eastern South Atlantic Ocean to determine diversity and biogeography of bacterial communities in deep-sea surface sediments. The analysis of 16S ribosomal RNA (rRNA) gene clone libraries in each basin revealed a high diversity, representing 521 phylotypes with 98% identity...

  10. ISHTE deep-ocean corers and heater-implant system. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Olson, L. O.; Harrison, J. G.

    1982-09-01

    Seafloor instrumentation systems are being developed for the In-Situ Heat Transfer Experiment (ISHTE) to determine the thermal conductivity of deep ocean sediments. As part of the experiment, a heat canister will be implanted into the sediment. Also, after about one year on the seafloor, core samplers are to be actuated to gather sediment samples. This report describes the deep ocean piston corers and the heater-implant drive system.

  11. Deep ocean model penetrator experiments

    International Nuclear Information System (INIS)

    Freeman, T.J.; Burdett, J.R.F.

    1986-01-01

    Preliminary trials of experimental model penetrators in the deep ocean have been conducted as an international collaborative exercise by participating members (national bodies and the CEC) of the Engineering Studies Task Group of the Nuclear Energy Agency's Seabed Working Group. This report describes and gives the results of these experiments, which were conducted at two deep ocean study areas in the Atlantic: Great Meteor East and the Nares Abyssal Plain. Velocity profiles of penetrators of differing dimensions and weights have been determined as they free-fell through the water column and impacted the sediment. These velocity profiles are used to determine the final embedment depth of the penetrators and the resistance to penetration offered by the sediment. The results are compared with predictions of embedment depth derived from elementary models of a penetrator impacting with a sediment. It is tentatively concluded that once the resistance to penetration offered by a sediment at a particular site has been determined, this quantity can be used to sucessfully predict the embedment that penetrators of differing sizes and weights would achieve at the same site

  12. Dynamic hole closure behind a deep ocean sediment penetrator

    International Nuclear Information System (INIS)

    Dzwilewski, P.T.; Karnes, C.H.

    1982-01-01

    A freefall or boosted penetrator is one concept being considered to dispose of nuclear waste in the deep ocean seabed. For this technique to be acceptable, the sediment must be an effective barrier to the migration of radioactive nuclides, which means that the hole behind the advancing penetrator must close. One mechanism which can cause the hole to close immediately behind the penetrator is the reduction in water pressure in the wake as water tries to follow the penetrator into the sediment. An approximate solution to this complex problem is presented which analyzes the deformation of the sediment with a nonlinear, large displacement and strain, Lagrangian finite-difference computer code (STEALTH). The water was treated by Bernoulli's Principle for flow in a pipe resulting in a pressure boundary condition applied to the sediment surface along the path after passage of the penetrator. Two one-dimensional and eight two-dimensional calculations were performed with various penetrator velocities (15, 30, and 60 m/s) and sediment shear strengths. In two of the calculations, the dynamic pressure reduction was neglected to see if geostatic stresses alone would close the hole. The results of this study showed that geostatic stresses alone would not close the hole but the dynamic pressure reduction would. The largest uncertainty in the analysis was the pressure conditions in the water behind the penetrator in which frictionless, steady-state flow, in a uniform diameter pipe was assumed. A more sophisticated and realistic pressure condition has been formulated and will be implemented in the computer code in the near future

  13. Eddy correlation measurements of oxygen uptake in deep ocean sediments

    DEFF Research Database (Denmark)

    Berg, P.; Glud, Ronnie Nøhr; Hume, A.

    2010-01-01

    .62 +/- 0.23 (SE, n = 7), 1.65 +/- 0.33 (n = 2), and 1.43 +/- 0.15 (n = 25) mmol m(-2) d(-1). The very good agreement between the eddy correlation flux and the chamber flux serves as a new, important validation of the eddy correlation technique. It demonstrates that the eddy correlation instrumentation......Abstract: We present and compare small sediment-water fluxes of O-2 determined with the eddy correlation technique, with in situ chambers, and from vertical sediment microprofiles at a 1450 m deep-ocean site in Sagami Bay, Japan. The average O-2 uptake for the three approaches, respectively, was 1...... available today is precise and can resolve accurately even very small benthic O-2 fluxes. The correlated fluctuations in vertical velocity and O-2 concentration that give the eddy flux had average values of 0.074 cm s(-1) and 0.049 mu M. The latter represents only 0.08% of the 59 mu M mean O-2 concentration...

  14. Micrometer- and nanometer-sized platinum group nuggets in micrometeorites from deep-sea sediments of the Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Rudraswami, N.G.; Parashar, K.; ShyamPrasad, M.

    We examined 378 micrometeorites collected from deep-sea sediments of the Indian Ocean of which 175, 180, and 23 are I-type, S-type, and G-type, respectively. Of the 175 I-type spherules, 13 contained platinum group element nuggets (PGNs...

  15. Applying machine learning to global surface ocean and seabed data to reveal the controls on the distribution of deep-sea sediments

    Science.gov (United States)

    Dutkiewicz, Adriana; Müller, Dietmar; O'Callaghan, Simon

    2017-04-01

    World's ocean basins contain a rich and nearly continuous record of environmental fluctuations preserved as different types of deep-sea sediments. The sediments represent the largest carbon sink on Earth and its largest geological deposit. Knowing the controls on the distribution of these sediments is essential for understanding the history of ocean-climate dynamics, including changes in sea-level and ocean circulation, as well as biological perturbations. Indeed, the bulk of deep-sea sediments comprises the remains of planktonic organisms that originate in the photic zone of the global ocean implying a strong connection between the seafloor and the sea surface. Machine-learning techniques are perfectly suited to unravelling these controls as they are able to handle large sets of spatial data and they often outperform traditional spatial analysis approaches. Using a support vector machine algorithm we recently created the first digital map of seafloor lithologies (Dutkiewicz et al., 2015) based on 14,400 surface samples. This map reveals significant deviations in distribution of deep-sea lithologies from hitherto hand-drawn maps based on far fewer data points. It also allows us to explore quantitatively, for the first time, the relationship between oceanographic parameters at the sea surface and lithologies on the seafloor. We subsequently coupled this global point sample dataset of 14,400 seafloor lithologies to bathymetry and oceanographic grids (sea-surface temperature, salinity, dissolved oxygen and dissolved inorganic nutrients) and applied a probabilistic Gaussian process classifier in an exhaustive combinatorial fashion (Dutkiewicz et al., 2016). We focused on five major lithologies (calcareous sediment, diatom ooze, radiolarian ooze, clay and lithogenous sediment) and used a computationally intensive five-fold cross-validation, withholding 20% of the data at each iteration, to assess the predictive performance of the machine learning method. We find that

  16. Thermophysical properties of deep ocean sediments

    International Nuclear Information System (INIS)

    Hadley, G.R.; McVey, D.F.; Morin, R.

    1980-01-01

    Here we report measurements of the thermal conductivity and diffusivity of reconsolidated illite and smectite ocean sediments at a pore pressure of 600 bars and temperatures ranging from 25 to 420 0 C. The conductivity and diffusivity were found to be in the range of 0.8 to 1.0 W/m-K and 2.2 to 2.8 x 10 -7 m 2 /s, respectively. These data are consistent with a mixture model which predicts sediment thermal properties as a function of constituent properties and porosity. Comparison of pre- and post-test physical properties indicated a decrease in pore water content and an order of magnitude increase in shear strength and permeability

  17. Avalanches of sediment form deep-marine depositions

    NARCIS (Netherlands)

    Pohl, Florian|info:eu-repo/dai/nl/34309424X

    2017-01-01

    The deep ocean is the largest sedimentary system basin on the planet. It serves as the primary storage point for all terrestrially weathered sediment that makes it beyond the near-shore environment. These deep-marine offshore deposits have become a focus of attention in exploration due to the

  18. Impact of open-ocean convection on particle fluxes and sediment dynamics in the deep margin of the Gulf of Lions

    Directory of Open Access Journals (Sweden)

    M. Stabholz

    2013-02-01

    Full Text Available The deep outer margin of the Gulf of Lions and the adjacent basin, in the western Mediterranean Sea, are regularly impacted by open-ocean convection, a major hydrodynamic event responsible for the ventilation of the deep water in the western Mediterranean Basin. However, the impact of open-ocean convection on the flux and transport of particulate matter remains poorly understood. The variability of water mass properties (i.e., temperature and salinity, currents, and particle fluxes were monitored between September 2007 and April 2009 at five instrumented mooring lines deployed between 2050 and 2350-m depth in the deepest continental margin and adjacent basin. Four of the lines followed a NW–SE transect, while the fifth one was located on a sediment wave field to the west. The results of the main, central line SC2350 ("LION" located at 42°02.5′ N, 4°41′ E, at 2350-m depth, show that open-ocean convection reached mid-water depth (≈ 1000-m depth during winter 2007–2008, and reached the seabed (≈ 2350-m depth during winter 2008–2009. Horizontal currents were unusually strong with speeds up to 39 cm s−1 during winter 2008–2009. The measurements at all 5 different locations indicate that mid-depth and near-bottom currents and particle fluxes gave relatively consistent values of similar magnitude across the study area except during winter 2008–2009, when near-bottom fluxes abruptly increased by one to two orders of magnitude. Particulate organic carbon contents, which generally vary between 3 and 5%, were abnormally low (≤ 1% during winter 2008–2009 and approached those observed in surface sediments (≈ 0.6%. Turbidity profiles made in the region demonstrated the existence of a bottom nepheloid layer, several hundred meters thick, and related to the resuspension of bottom sediments. These observations support the view that open-ocean deep convection events in the Gulf of Lions can cause significant remobilization

  19. Development of an assessment methodology for the disposal of high-level radioactive waste into deep ocean sediments

    International Nuclear Information System (INIS)

    Murray, C.N.; Stanners, D.A.

    1982-01-01

    This paper presents the results of a theoretical study concerning the option of disposal of vitrified high activity waste (HAW) into deep ocean sediments. The development of a preliminary methodology is presented which concerns the assessment of the possible effects of a release of radioactivity on the ecosystem and eventually on man. As the long-term hazard is considered basically to be due to transuranic elements (and daughter products) the period studied for the assessment is from 10 3 to 10 6 years. A simple ecosystem model is developed so that the transfer of activity between different compartments of the systems, e.g. the sediment column, sediment-water interface, deep sea water column, can be estimated. A critical pathway analysis is made for an imaginary critical group in order to complete the assessment. A sensitivity analysis is undertaken using the computed minimum-maximum credible values for the different parameters used in the calculations in order to obtain a minimum-maximum dose range for a critical group. (Auth.)

  20. Geotechnical parameters for three deep ocean study areas

    International Nuclear Information System (INIS)

    Nicholson, D.P.

    1989-01-01

    This chapter summarizes the results of geotechnical measurements made on cores taken at the three deep ocean sites that have been studied in detail as part of the international programme assessing the feasibility of deep ocean disposal of heat-generating radioactive waste. The capabilities of existing sampling methods and the adequacy of the available data for providing the geotechnical parameters needed to evaluate the technical feasibility of deep ocean disposal are discussed. It is concluded that, while it has not been possible to obtain core samples of sufficient quality and depth to provide all the parameters needed for the assessment, no fundamental differences between the sediments at the study areas and those found on land or in shallow water have been identified. (author)

  1. Finite element analysis of thermal convection in deep ocean sediments

    International Nuclear Information System (INIS)

    Gartling, D.K.

    1980-01-01

    Of obvious importance to the study and engineering of a seabed disposal is the determination of the temperature and fluid flow fields existing in the sediment layer and the perturbation of these fields due to the implantation of localized heat sources. The fluid mechanical and heat transfer process occurring in oceanic sediments may be characterized as free (or natural) convection in a porous material. In the case of an undisturbed sediment layer, the driving force for the natural circulation of pore water comes from the geothermal heat flux. Current theories for heat flow from the sea floor suggest the possibility of large scale hydrothermal circulation in the oceanic crust (see e.g., Ribando, et al. 1976) which is in turn coupled with a convection process in the overlying sediment layer (Anderson 1980, Anderson, et al. 1979). The introduction of a local heat source, such as a waste canister, into a saturated sediment layer would by itself initiate a convection process due to buoyancy forces. Since the mathematical description of natural convection in a porous medium is of sufficient complexity to preclude the use of most analytic methods of analysis, approximate numerical procedures are often employed. In the following sections, a particular type of numerical method is described that has proved useful in the solution of a variety of porous flow problems. However, rather than concentrate on the details of the numerical algorithm the main emphasis of the presentation will be on the types of problems and results that are encountered in the areas of oceanic heat flow and seabed waste disposal

  2. Study of elementary absorption in the marine sediments of the North Atlantic ocean deeps

    International Nuclear Information System (INIS)

    Rancon, D.; Guegueniat, P.

    1984-01-01

    We have studied the retention of actinide elements (Np, Pu, Am) and of Cs in the sediments of the ocean deeps around Cap-Vert. Plutonium: retention increases with temperatures of 4 to 30 0 C, then stays constant from 30 to 80 0 C. Desorption is slow. Americium: absorption is very strong at any temperature. Measurements of a wide variety of sediments show that retention is not affected by facies (including carbonated sediments). Neptunium: retention is more or less constant between 4 and 15 0 C, and distinctly higher at 30-50 0 C. It is reversible. Caesium: absorption decreases slightly from 4 to 30 0 C, but increases rapidly at 50 to 80 0 C. At the lowest temperatures it is reversible, but it appears to be irreversible at 50 0 . Cs absorption is subject to ponderal concentration. With equal amounts of activity, retention of Cs-135 is weaker than that of Cs-137: likewise the addition of the stable isotope causes in the amounts of Kd in Cs-137. Finally, this paper presents preliminary results showing the natural metallic element content of the sediments

  3. Experimental studies on behaviour of long-lived radionuclides in relation to deep-ocean disposal of nuclear waste

    International Nuclear Information System (INIS)

    Aston, S.R.; Fowler, S.W.

    1984-01-01

    Laboratory experiments have been carried out to investigate the interactions of long-lived radionuclides with sediments from present or potential deep-ocean radioactive waste disposal sites. The studies have been concerned with both geochemical aspects and sediment/animal radioecology. Examples drawn from the comparative behaviour of technetium and three transuranium nuclides (neptunium, plutonium and americium) are presented in relation to their uptake from sea water by deep-ocean sediments, ease of desorption and transfer from contaminated sediments to benthic invertebrates. The results provide information for the prediction of the behaviour of long-lived radionuclides in the deep-sea water/sediment boundary after their release from wastes. (author)

  4. Clay mineralogical and Sr, Nd isotopic investigations in two deep-sea sediment cores from Northeast Indian Ocean

    International Nuclear Information System (INIS)

    Anil Babu, G.; Masood Ahmad, S.; Padmakumari, V.M.; Dayal, A.M.

    2004-01-01

    Sr and Nd isotopic studies in terrigenous component of the ocean sediments provide useful information about weathering patterns near source rock and climatic conditions existed on the continents. Variations in 87 Sr/ 86 Sr and 143 Nd/ 144 Nd isotopic ratios in clastic sediments depend on the source from the continents, volcanic input and circulation changes. The composition of clay minerals mainly depends on climate, geology and topography of the surrounding region. Chlorite and Illite are formed under physical weathering in arid cold climate and kaolinite and smectite are the characteristic products of chemical weathering in humid wet climatic conditions. Therefore, the variations in clay mineral composition in deep-sea sediments can be interpreted in terms of changes in the climatic conditions prevailed in the continental source areas

  5. High rates of microbial carbon turnover in sediments in the deepest oceanic trench on Earth

    DEFF Research Database (Denmark)

    Glud, Ronnie N.; Wenzhoefer, Frank; Middelboe, Mathias

    2013-01-01

    Microbes control the decomposition of organic matter in marine sediments. Decomposition, in turn, contributes to oceanic nutrient regeneration and influences the preservation of organic carbon(1). Generally, rates of benthic decomposition decline with increasing water depth, although given the vast...... extent of the abyss, deep-sea sediments are quantitatively important for the global carbon cycle(2,3). However, the deepest regions of the ocean have remained virtually unexplored(4). Here, we present observations of microbial activity in sediments at Challenger Deep in the Mariana Trench in the central...

  6. Widespread Anthropogenic Nitrogen in Northwestern Pacific Ocean Sediment.

    Science.gov (United States)

    Kim, Haryun; Lee, Kitack; Lim, Dhong-Il; Nam, Seung-Il; Kim, Tae-Wook; Yang, Jin-Yu T; Ko, Young Ho; Shin, Kyung-Hoon; Lee, Eunil

    2017-06-06

    Sediment samples from the East China and Yellow seas collected adjacent to continental China were found to have lower δ 15 N values (expressed as δ 15 N = [ 15 N: 14 N sample / 15 N: 14 N air - 1] × 1000‰; the sediment 15 N: 14 N ratio relative to the air nitrogen 15 N: 14 N ratio). In contrast, the Arctic sediments from the Chukchi Sea, the sampling region furthest from China, showed higher δ 15 N values (2-3‰ higher than those representing the East China and the Yellow sea sediments). Across the sites sampled, the levels of sediment δ 15 N increased with increasing distance from China, which is broadly consistent with the decreasing influence of anthropogenic nitrogen (N ANTH ) resulting from fossil fuel combustion and fertilizer use. We concluded that, of several processes, the input of N ANTH appears to be emerging as a new driver of change in the sediment δ 15 N value in marginal seas adjacent to China. The present results indicate that the effect of N ANTH has extended beyond the ocean water column into the deep sedimentary environment, presumably via biological assimilation of N ANTH followed by deposition. Further, the findings indicate that N ANTH is taking over from the conventional paradigm of nitrate flux from nitrate-rich deep water as the primary driver of biological export production in this region of the Pacific Ocean.

  7. Creep of ocean sediments resulting from the isolation of radioactive wastes

    International Nuclear Information System (INIS)

    Dawson, P.R.; Chavez, P.F.; Lipkin, J.; Silva, A.J.

    1980-01-01

    Predictive models for the creep of deep ocean sediments resulting from the disposal of radioactive wastes are presented and preliminary observations of a program for evaluation of creep constitutive equation parameters are discussed. The models are used to provide calculated response of sediments under waste disposal conditions

  8. Sediments and fossiliferous rocks from the eastern side of the Tongue of the Ocean, Bahamas

    Science.gov (United States)

    Gibson, T.G.; Schlee, J.

    1967-01-01

    In August 1966, two dives were made with the deep-diving submersible Alvin along the eastern side of the Tongue of the Ocean to sample the rock and sediment. Physiographically, the area is marked by steep slopes of silty carbonate sediment and precipitous rock cliffs dusted by carbonate debris. Three rocks, obtained from the lower and middle side of the canyon (914-1676 m depth), are late Miocene-early Pliocene to late Pleistocene-Recent in age; all are deep-water pelagic limestones. They show (i) that the Tongue of the Ocean has been a deep-water area at least back into the Miocene, and (ii) that much shallow-water detritus has been swept off neighbouring banks to be incorporated with the deep-water fauna in the sediment. ?? 1967 Pergamon Press Ltd.

  9. Predicting Sediment Thickness on Vanished Ocean Crust Since 200 Ma

    Science.gov (United States)

    Dutkiewicz, A.; Müller, R. D.; Wang, X.; O'Callaghan, S.; Cannon, J.; Wright, N. M.

    2017-12-01

    Tracing sedimentation through time on existing and vanished seafloor is imperative for constraining long-term eustasy and for calculating volumes of subducted deep-sea sediments that contribute to global geochemical cycles. We present regression algorithms that incorporate the age of the ocean crust and the mean distance to the nearest passive margin to predict sediment thicknesses and long-term decompacted sedimentation rates since 200 Ma. The mean sediment thickness decreases from ˜220 m at 200 Ma to a minimum of ˜140 m at 130 Ma, reflecting the replacement of old Panthalassic ocean floor with young sediment-poor mid-ocean ridges, followed by an increase to ˜365 m at present-day. This increase reflects the accumulation of sediments on ageing abyssal plains proximal to passive margins, coupled with a decrease in the mean distance of any parcel of ocean crust to the nearest passive margin by over 700 km, and a doubling of the total passive margin length at present-day. Mean long-term sedimentation rates increase from ˜0.5 cm/ky at 160 Ma to over 0.8 cm/ky today, caused by enhanced terrigenous sediment influx along lengthened passive margins, superimposed by the onset of ocean-wide carbonate sedimentation. Our predictive algorithms, coupled to a plate tectonic model, provide a framework for constraining the seafloor sediment-driven eustatic sea-level component, which has grown from ˜80 to 210 m since 120 Ma. This implies a long-term sea-level rise component of 130 m, partly counteracting the contemporaneous increase in ocean basin depth due to progressive crustal ageing.

  10. Earth system feedback statistically extracted from the Indian Ocean deep-sea sediments recording Eocene hyperthermals.

    Science.gov (United States)

    Yasukawa, Kazutaka; Nakamura, Kentaro; Fujinaga, Koichiro; Ikehara, Minoru; Kato, Yasuhiro

    2017-09-12

    Multiple transient global warming events occurred during the early Palaeogene. Although these events, called hyperthermals, have been reported from around the globe, geologic records for the Indian Ocean are limited. In addition, the recovery processes from relatively modest hyperthermals are less constrained than those from the severest and well-studied hothouse called the Palaeocene-Eocene Thermal Maximum. In this study, we constructed a new and high-resolution geochemical dataset of deep-sea sediments clearly recording multiple Eocene hyperthermals in the Indian Ocean. We then statistically analysed the high-dimensional data matrix and extracted independent components corresponding to the biogeochemical responses to the hyperthermals. The productivity feedback commonly controls and efficiently sequesters the excess carbon in the recovery phases of the hyperthermals via an enhanced biological pump, regardless of the magnitude of the events. Meanwhile, this negative feedback is independent of nannoplankton assemblage changes generally recognised in relatively large environmental perturbations.

  11. A feasibility study of the disposal of radioactive waste in deep ocean sediments by drilled emplacement

    International Nuclear Information System (INIS)

    Bury, M.R.C.

    1983-08-01

    This report describes the second phase of a study of the feasibility of disposal and isolation of high level radioactive waste in holes drilled deep into the sediments of the ocean. In this phase, work has concentrated on establishing the state of the art of the various operations and developing the design, in particular the drilling operation, the loading of flasks containing waste canisters from supply vessels onto the platform, the handling of radioactive waste on board, and its emplacement into predrilled holes. In addition, an outline design of the offshore platform has been prepared. (author)

  12. The permeability and consolidation of deep-sea sediments

    International Nuclear Information System (INIS)

    Schultheiss, P.J.; Gunn, D.E.

    1985-01-01

    This report presents permeability and consolidation data for a wide range of sediment types. Permeability is one of the two parameters which are needed to directly quantify pore water advection in deep sea sediments and which are being investigated in high-level radioactive waste study areas. While it is desirable that these parameters should be measured in situ it is argued that values of permeability can be measured sufficiently accurately in the laboratory from core samples. Consequently, an apparatus has been developed which enables sediment permeability to be measured at decreasing void ratios during a back-pressured consolidation test. Data presented in this report from over 60 samples have established the major differences in permeability between various sediment types and how permeability changes as a function of burial depth and void ratio. Samples from two study areas in the North Atlantic Ocean, King's Trough Flank (KTF) and Great Meteor East (GME), have been compared with samples of Red Clay (RC) obtained from the NW Pacific Ocean. Results are presented and discussed. (author)

  13. High-level radioactive waste disposal in the deep ocean

    International Nuclear Information System (INIS)

    Hill, H.W.

    1977-01-01

    A joint programme has begun between the Fisheries Laboratory, Lowestoft and the Institute of Oceanographic Sciences, Wormley to study the dispersion of radioactivity in the deep ocean arising from the possible dumping of high level waste on the sea bed in vitrified-glass form which would permit slow leakage over a long term scale. The programme consists firstly of the development of a simple diffusion/advection model for the dispersion of radioactivity in a closed and finite ocean, which overcomes many of the criticisms of the earlier model proposed by Webb and Morley. Preliminary results from this new model are comparable to those of the Webb-Morley model for radio isotopes with half-lives of 10-300 years but are considerably more restrictive outside this range, particularly for those which are much longer-lived. The second part of the programme, towards which the emphasis is directed, concerns the field programme planned to measure the advection and diffusion parameters in the deeper layers of the ocean to provide realistic input parameters to the model and increase our fundamental understanding of the environment in which the radioactive materials may be released. The first cruises of the programme will take place in late 1976 and involve deep current meter deployments and float dispersion experiments around the present NEA dump site with some sediment sampling, so that adsorption experiments can be started on typical deep sea sediments. The programme will expand the number of long-term deep moored stations over the next five years and include further float experiments, CTD profiling, and other physical oceanography. In the second half of the 5-year programme, attempts will be made to measure diffusion parameters in the deeper layers of the ocean using radioactive tracers

  14. Ocean Sediment Thickness Contours

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Ocean sediment thickness contours in 200 meter intervals for water depths ranging from 0 - 18,000 meters. These contours were derived from a global sediment...

  15. Particle fluxes in the deep Eastern Mediterranean basins: the role of ocean vertical velocities

    Directory of Open Access Journals (Sweden)

    L. Patara

    2009-03-01

    Full Text Available This paper analyzes the relationship between deep sedimentary fluxes and ocean current vertical velocities in an offshore area of the Ionian Sea, the deepest basin of the Eastern Mediterranean Sea. Sediment trap data are collected at 500 m and 2800 m depth in two successive moorings covering the period September 1999–May 2001. A tight coupling is observed between the upper and deep traps and the estimated particle sinking rates are more than 200 m day−1. The current vertical velocity field is computed from a 1/16°×1/16° Ocean General Circulation Model simulation and from the wind stress curl. Current vertical velocities are larger and more variable than Ekman vertical velocities, yet the general patterns are alike. Current vertical velocities are generally smaller than 1 m day−1: we therefore exclude a direct effect of downward velocities in determining high sedimentation rates. However we find that upward velocities in the subsurface layers of the water column are positively correlated with deep particle fluxes. We thus hypothesize that upwelling would produce an increase in upper ocean nutrient levels – thus stimulating primary production and grazing – a few weeks before an enhanced vertical flux is found in the sediment traps. High particle sedimentation rates may be attained by means of rapidly sinking fecal pellets produced by gelatinous macro-zooplankton. Other sedimentation mechanisms, such as dust deposition, are also considered in explaining large pulses of deep particle fluxes. The fast sinking rates estimated in this study might be an evidence of the efficiency of the biological pump in sequestering organic carbon from the surface layers of the deep Eastern Mediterranean basins.

  16. Distribution of PAHs and the PAH-degrading bacteria in the deep-sea sediments of the high-latitude Arctic Ocean

    Science.gov (United States)

    Dong, C.; Bai, X.; Sheng, H.; Jiao, L.; Zhou, H.; Shao, Z.

    2015-04-01

    Polycyclic aromatic hydrocarbons (PAHs) are common organic pollutants that can be transferred long distances and tend to accumulate in marine sediments. However, less is known regarding the distribution of PAHs and their natural bioattenuation in the open sea, especially the Arctic Ocean. In this report, sediment samples were collected at four sites from the Chukchi Plateau to the Makarov Basin in the summer of 2010. PAH compositions and total concentrations were examined with GC-MS. The concentrations of 16 EPA-priority PAHs varied from 2.0 to 41.6 ng g-1 dry weight and decreased with sediment depth and movement from the southern to the northern sites. Among the targeted PAHs, phenanthrene was relatively abundant in all sediments. The 16S rRNA gene of the total environmental DNA was analyzed with Illumina high-throughput sequencing (IHTS) to determine the diversity of bacteria involved in PAH degradation in situ. The potential degraders including Cycloclasticus, Pseudomonas, Halomonas, Pseudoalteromonas, Marinomonas, Bacillus, Dietzia, Colwellia, Acinetobacter, Alcanivorax, Salinisphaera and Shewanella, with Dietzia as the most abundant, occurred in all sediment samples. Meanwhile, enrichment with PAHs was initiated onboard and transferred to the laboratory for further enrichment and to obtain the degrading consortia. Most of the abovementioned bacteria in addition to Hahella, Oleispira, Oceanobacter and Hyphomonas occurred alternately as predominant members in the enrichment cultures from different sediments based on IHTS and PCR-DGGE analysis. To reconfirm their role in PAH degradation, 40 different bacteria were isolated and characterized, among which Cycloclasticus Pseudomonas showed the best degradation capability under low temperatures. Taken together, PAHs and PAH-degrading bacteria were widespread in the deep-sea sediments of the Arctic Ocean. We propose that bacteria of Cycloclasticus, Pseudomonas, Pseudoalteromonas, Halomonas, Marinomonas and Dietzia may

  17. Deciphering Equatorial Pacific Deep Sea Sediment Transport Regimes by Core-Log-Seismic Integration

    Science.gov (United States)

    Ortiz, E.; Tominaga, M.; Marcantonio, F.

    2017-12-01

    Investigating deep-sea sediment transportation and deposition regimes is a key to accurately understand implications from geological information recorded by pelagic sediments, e.g. climate signals. However, except for physical oceanographic particle trap experiments, geochemical analyses of in situsediments, and theoretical modeling of the relation between the bottom currents and sediment particle flux, it has remained a challenging task to document the movement of deep sea sediments, that takes place over time. We utilized high-resolution, multichannel reflection seismic data from the eastern equatorial Pacific region with drilling and logging results from two Integrated Ocean Drilling Program (IODP) sites, the Pacific Equatorial Age Transect (PEAT) 7 (Site U1337) and 8 (Site U1338), to characterize sediment transportation regimes on 18-24 Ma oceanic crust. Site U1337, constructed by a series of distinct abyssal hills and abyssal basins; Site U1338, located 570 km SE from Site U1337 site and constructed by a series of ridges, seamounts, and abyssal hills. These sites are of particular interest due to their proximity to the equatorial productivity zone, areas with high sedimentation rates and preservation of carbonate-bearing sediment that provide invaluable insights on equatorial Pacific ecosystems and carbon cycle. We integrate downhole geophysical logging data as well as geochemistry and physical properties measurements on recovered cores from IODP Sites U1337 and U1338 to comprehensively examine the mobility of deep-sea sediments and sediment diagenesis over times in a quasi-3D manner. We also examine 1100 km of high resolution underway seismic surveys from site survey lines in between PEAT 7 and 8 in order to investigate changes in sediment transportation between both sites. Integrating detailed seismic interpretations, high resolution core data, and 230Th flux measurements we aim to create a detailed chronological sedimentation and sediment diagenesis history

  18. Metagenomic profiles of antibiotic resistance genes (ARGs) between human impacted estuary and deep ocean sediments.

    Science.gov (United States)

    Chen, Baowei; Yang, Ying; Liang, Ximei; Yu, Ke; Zhang, Tong; Li, Xiangdong

    2013-11-19

    Knowledge of the origins and dissemination of antibiotic resistance genes (ARGs) is essential for understanding modern resistomes in the environment. The mechanisms of the dissemination of ARGs can be revealed through comparative studies on the metagenomic profiling of ARGs between relatively pristine and human-impacted environments. The deep ocean bed of the South China Sea (SCS) is considered to be largely devoid of anthropogenic impacts, while the Pearl River Estuary (PRE) in south China has been highly impacted by intensive human activities. Commonly used antibiotics (sulfamethazine, norfloxacin, ofloxacin, tetracycline, and erythromycin) have been detected through chemical analysis in the PRE sediments, but not in the SCS sediments. In the relatively pristine SCS sediments, the most prevalent and abundant ARGs are those related to resistance to macrolides and polypeptides, with efflux pumps as the predominant mechanism. In the contaminated PRE sediments, the typical ARG profiles suggest a prevailing resistance to antibiotics commonly used in human health and animal farming (including sulfonamides, fluoroquinolones, and aminoglycosides), and higher diversity in both genotype and resistance mechanism than those in the SCS. In particular, antibiotic inactivation significantly contributed to the resistance to aminoglycosides, β-lactams, and macrolides observed in the PRE sediments. There was a significant correlation in the levels of abundance of ARGs and those of mobile genetic elements (including integrons and plasmids), which serve as carriers in the dissemination of ARGs in the aquatic environment. The metagenomic results from the current study support the view that ARGs naturally originate in pristine environments, while human activities accelerate the dissemination of ARGs so that microbes would be able to tolerate selective environmental stress in response to anthropogenic impacts.

  19. A comparison of microbial communities in deep-sea polymetallic nodules and the surrounding sediments in the Pacific Ocean

    Science.gov (United States)

    Wu, Yue-Hong; Liao, Li; Wang, Chun-Sheng; Ma, Wei-Lin; Meng, Fan-Xu; Wu, Min; Xu, Xue-Wei

    2013-09-01

    Deep-sea polymetallic nodules, rich in metals such as Fe, Mn, and Ni, are potential resources for future exploitation. Early culturing and microscopy studies suggest that polymetallic nodules are at least partially biogenic. To understand the microbial communities in this environment, we compared microbial community composition and diversity inside nodules and in the surrounding sediments. Three sampling sites in the Pacific Ocean containing polymetallic nodules were used for culture-independent investigations of microbial diversity. A total of 1013 near full-length bacterial 16S rRNA gene sequences and 640 archaeal 16S rRNA gene sequences with ~650 bp from nodules and the surrounding sediments were analyzed. Bacteria showed higher diversity than archaea. Interestingly, sediments contained more diverse bacterial communities than nodules, while the opposite was detected for archaea. Bacterial communities tend to be mostly unique to sediments or nodules, with only 13.3% of sequences shared. The most abundant bacterial groups detected only in nodules were Pseudoalteromonas and Alteromonas, which were predicted to play a role in building matrix outside cells to induce or control mineralization. However, archaeal communities were mostly shared between sediments and nodules, including the most abundant OTU containing 290 sequences from marine group I Thaumarchaeota. PcoA analysis indicated that microhabitat (i.e., nodule or sediment) seemed to be a major factor influencing microbial community composition, rather than sampling locations or distances between locations.

  20. Bacterial Sulfate Reduction Above 100-Degrees-C in Deep-Sea Hydrothermal Vent Sediments

    DEFF Research Database (Denmark)

    JØRGENSEN, BB; ISAKSEN, MF; JANNASCH, HW

    1992-01-01

    -reducing bacteria was done in hot deep-sea sediments at the hydrothermal vents of the Guaymas Basin tectonic spreading center in the Gulf of California. Radiotracer studies revealed that sulfate reduction can occur at temperatures up to 110-degrees-C, with an optimum rate at 103-degrees to 106-degrees......-C. This observation expands the upper temperature limit of this process in deep-ocean sediments by 20-degrees-C and indicates the existence of an unknown groUp of hyperthermophilic bacteria with a potential importance for the biogeochemistry of sulfur above 100-degrees-C....

  1. Enrichments in authigenic uranium in glacial sediments of the Southern Ocean; Enrichissement en uranium authigene dans les sediments glaciaires de l'ocean Austral

    Energy Technology Data Exchange (ETDEWEB)

    Dezileau, L. [Universidad de Conception, Programa Regional de Oceanografia Fisica y Climat PROFC, Y Centro de Investigacion Oceanografica (Chile); Bareille, G. [Pau Univ., Lab. de Chimie Analytique Bio-Inorganique et Environnement, EP-CNRS 132, 64 (France); Reyss, J.L. [CEA Saclay, Direction des Sciences de la Matiere, Lab. des Sciences du Climat et de L' environnement, Lab. Mixte CEA-CNRS, 91 - Gif-sur-Yvette (France)

    2002-11-01

    Four sediment cores from the Polar frontal zone and the Antarctic zone in the Indian sector of the Southern Ocean present an increase of authigenic uranium during glacial periods. We show that this increase in uranium is due to a combination of (i) an increase in the lateral transport of organic matter, (ii) a decrease in the oxygen in deep waters, and (iii) a process of diagenesis. It appears that uranium concentration cannot be used as a proxy of paleo-productivity in the Southern Ocean, as previously suggested by Kumar et al. in 1995. (authors)

  2. The deep ocean under climate change

    Science.gov (United States)

    Levin, Lisa A.; Le Bris, Nadine

    2015-11-01

    The deep ocean absorbs vast amounts of heat and carbon dioxide, providing a critical buffer to climate change but exposing vulnerable ecosystems to combined stresses of warming, ocean acidification, deoxygenation, and altered food inputs. Resulting changes may threaten biodiversity and compromise key ocean services that maintain a healthy planet and human livelihoods. There exist large gaps in understanding of the physical and ecological feedbacks that will occur. Explicit recognition of deep-ocean climate mitigation and inclusion in adaptation planning by the United Nations Framework Convention on Climate Change (UNFCCC) could help to expand deep-ocean research and observation and to protect the integrity and functions of deep-ocean ecosystems.

  3. Energy Gradients Structure Microbial Communities Across Sediment Horizons in Deep Marine Sediments of the South China Sea

    Science.gov (United States)

    Graw, Michael F.; D'Angelo, Grace; Borchers, Matthew; Thurber, Andrew R.; Johnson, Joel E.; Zhang, Chuanlun; Liu, Haodong; Colwell, Frederick S.

    2018-01-01

    The deep marine subsurface is a heterogeneous environment in which the assembly of microbial communities is thought to be controlled by a combination of organic matter deposition, electron acceptor availability, and sedimentology. However, the relative importance of these factors in structuring microbial communities in marine sediments remains unclear. The South China Sea (SCS) experiences significant variability in sedimentation across the basin and features discrete changes in sedimentology as a result of episodic deposition of turbidites and volcanic ashes within lithogenic clays and siliceous or calcareous ooze deposits throughout the basin's history. Deep subsurface microbial communities were recently sampled by the International Ocean Discovery Program (IODP) at three locations in the SCS with sedimentation rates of 5, 12, and 20 cm per thousand years. Here, we used Illumina sequencing of the 16S ribosomal RNA gene to characterize deep subsurface microbial communities from distinct sediment types at these sites. Communities across all sites were dominated by several poorly characterized taxa implicated in organic matter degradation, including Atribacteria, Dehalococcoidia, and Aerophobetes. Sulfate-reducing bacteria comprised only 4% of the community across sulfate-bearing sediments from multiple cores and did not change in abundance in sediments from the methanogenic zone at the site with the lowest sedimentation rate. Microbial communities were significantly structured by sediment age and the availability of sulfate as an electron acceptor in pore waters. However, microbial communities demonstrated no partitioning based on the sediment type they inhabited. These results indicate that microbial communities in the SCS are structured by the availability of electron donors and acceptors rather than sedimentological characteristics. PMID:29696012

  4. In-situ detection of microbial life in the deep biosphere in igneous ocean crust

    Directory of Open Access Journals (Sweden)

    Everett Cosio Salas

    2015-11-01

    Full Text Available The deep biosphere is a major frontier to science. Recent studies have shown the presence and activity of cells in deep marine sediments and in the continental deep biosphere. Volcanic lavas in the deep ocean subsurface, through which substantial fluid flow occurs, present another potentially massive deep biosphere. We present results from the deployment of a novel in-situ logging tool designed to detect microbial life harbored in a deep, native, borehole environment within igneous oceanic crust, using deep ultraviolet native fluorescence spectroscopy. Results demonstrate the predominance of microbial-like signatures within the borehole environment, with densities in the range of 105 cells/mL. Based on transport and flux models, we estimate that such a concentration of microbial cells could not be supported by transport through the crust, suggesting in situ growth of these communities.

  5. In situ Detection of Microbial Life in the Deep Biosphere in Igneous Ocean Crust.

    Science.gov (United States)

    Salas, Everett C; Bhartia, Rohit; Anderson, Louise; Hug, William F; Reid, Ray D; Iturrino, Gerardo; Edwards, Katrina J

    2015-01-01

    The deep biosphere is a major frontier to science. Recent studies have shown the presence and activity of cells in deep marine sediments and in the continental deep biosphere. Volcanic lavas in the deep ocean subsurface, through which substantial fluid flow occurs, present another potentially massive deep biosphere. We present results from the deployment of a novel in situ logging tool designed to detect microbial life harbored in a deep, native, borehole environment within igneous oceanic crust, using deep ultraviolet native fluorescence spectroscopy. Results demonstrate the predominance of microbial-like signatures within the borehole environment, with densities in the range of 10(5) cells/mL. Based on transport and flux models, we estimate that such a concentration of microbial cells could not be supported by transport through the crust, suggesting in situ growth of these communities.

  6. Supernova-produced radionuclides in deep-sea sediments measured with AMS

    International Nuclear Information System (INIS)

    Feige, J.

    2014-01-01

    This thesis is dedicated to computational micromagnetics, where several new numerical methods are In this work a set of long-lived radionuclides is measured to detect supernova-traces presumably deposited on Earth 2-3 Myr ago. Approximately 100 samples of four deep-sea sediment cores (Indian Ocean) were analyzed for 26 Al, 53Mn, and 60 Fe with accelerator mass spectrometry (AMS). Additionally, 10 Be was measured to confirm the existing paleomagnetic chronology of the sediments. A signal of extraterrestrial 60 Fe, which is not produced in-situ on Earth, was detected in a time period of 1.7-3.2 Myr in the sediments used for this work. 60 Fe/ 26 Al ratios were used to calculate limits on theoretical nucleosynthesis models. A supernova-signature of 26 Al is hidden behind a terrestrial background. The measured 26 Al/ 10 Be ratios indicate, that the major source of 26 Al detected in the sediments is of atmospheric origin. Because of the extraordinarily good depth profile for the deep-sea sediments from the measured 26 Al data, this radionuclide was used for dating. (author) [de

  7. The deep ocean under climate change.

    Science.gov (United States)

    Levin, Lisa A; Le Bris, Nadine

    2015-11-13

    The deep ocean absorbs vast amounts of heat and carbon dioxide, providing a critical buffer to climate change but exposing vulnerable ecosystems to combined stresses of warming, ocean acidification, deoxygenation, and altered food inputs. Resulting changes may threaten biodiversity and compromise key ocean services that maintain a healthy planet and human livelihoods. There exist large gaps in understanding of the physical and ecological feedbacks that will occur. Explicit recognition of deep-ocean climate mitigation and inclusion in adaptation planning by the United Nations Framework Convention on Climate Change (UNFCCC) could help to expand deep-ocean research and observation and to protect the integrity and functions of deep-ocean ecosystems. Copyright © 2015, American Association for the Advancement of Science.

  8. A record of deep-ocean dissolved O2 from the oxidation state of iron in submarine basalts

    Science.gov (United States)

    Stolper, Daniel A.; Keller, C. Brenhin

    2018-01-01

    The oxygenation of the deep ocean in the geological past has been associated with a rise in the partial pressure of atmospheric molecular oxygen (O2) to near-present levels and the emergence of modern marine biogeochemical cycles. It has also been linked to the origination and diversification of early animals. It is generally thought that the deep ocean was largely anoxic from about 2,500 to 800 million years ago, with estimates of the occurrence of deep-ocean oxygenation and the linked increase in the partial pressure of atmospheric oxygen to levels sufficient for this oxygenation ranging from about 800 to 400 million years ago. Deep-ocean dissolved oxygen concentrations over this interval are typically estimated using geochemical signatures preserved in ancient continental shelf or slope sediments, which only indirectly reflect the geochemical state of the deep ocean. Here we present a record that more directly reflects deep-ocean oxygen concentrations, based on the ratio of Fe3+ to total Fe in hydrothermally altered basalts formed in ocean basins. Our data allow for quantitative estimates of deep-ocean dissolved oxygen concentrations from 3.5 billion years ago to 14 million years ago and suggest that deep-ocean oxygenation occurred in the Phanerozoic (541 million years ago to the present) and potentially not until the late Palaeozoic (less than 420 million years ago).

  9. A record of deep-ocean dissolved O2 from the oxidation state of iron in submarine basalts.

    Science.gov (United States)

    Stolper, Daniel A; Keller, C Brenhin

    2018-01-18

    The oxygenation of the deep ocean in the geological past has been associated with a rise in the partial pressure of atmospheric molecular oxygen (O 2 ) to near-present levels and the emergence of modern marine biogeochemical cycles. It has also been linked to the origination and diversification of early animals. It is generally thought that the deep ocean was largely anoxic from about 2,500 to 800 million years ago, with estimates of the occurrence of deep-ocean oxygenation and the linked increase in the partial pressure of atmospheric oxygen to levels sufficient for this oxygenation ranging from about 800 to 400 million years ago. Deep-ocean dissolved oxygen concentrations over this interval are typically estimated using geochemical signatures preserved in ancient continental shelf or slope sediments, which only indirectly reflect the geochemical state of the deep ocean. Here we present a record that more directly reflects deep-ocean oxygen concentrations, based on the ratio of Fe 3+ to total Fe in hydrothermally altered basalts formed in ocean basins. Our data allow for quantitative estimates of deep-ocean dissolved oxygen concentrations from 3.5 billion years ago to 14 million years ago and suggest that deep-ocean oxygenation occurred in the Phanerozoic (541 million years ago to the present) and potentially not until the late Palaeozoic (less than 420 million years ago).

  10. Analytical investigation of high temperature 1 kW solid oxide fuel cell system feasibility in methane hydrate recovery and deep ocean power generation

    International Nuclear Information System (INIS)

    Azizi, Mohammad Ali; Brouwer, Jacob; Dunn-Rankin, Derek

    2016-01-01

    Highlights: • A dynamic Solid Oxide Fuel Cell (SOFC) model was developed. • Hydrate bed methane dissociation model was integrated with the SOFC model. • SOFC operated steadily for 120 days at high pressure deep ocean environment. • Burning some of the dissociated gas for SMR heat leads to more net methane produced. • Higher SOFC fuel utilization produces higher integrated system efficiency. - Abstract: Methane hydrates are potential valuable energy resources. However, finding an efficient method for methane gas recovery from hydrate sediments is still a challenge. New challenges arise from increasing environmental protection. This is due in part to the technical difficulties involved in the efficient dissociation of methane hydrates at high pressures. In this study, a new approach is proposed to produce valuable products of: 1. Net methane gas recovery from the methane hydrate sediment, and 2. Deep ocean power generation. We have taken the first steps toward utilization of a fuel cell system in methane gas recovery from deep ocean hydrate sediments. An integrated high pressure and high temperature solid oxide fuel cell (SOFC) and steam methane reformer (SMR) system is analyzed for this application and the recoverable amount of methane from deep ocean sediments is measured. System analysis is accomplished for two major cases regarding system performance: 1. Energy for SMR is provided by the burning part of the methane gas dissociated from the hydrate sediment. 2. Energy for SMR is provided through heat exchange with fuel cell effluent gases. We found that the total production of methane gas is higher in the first case compared to the second case. The net power generated by the fuel cell system is estimated for all cases. The primary goal of this study is to evaluate the feasibility of integrated electrochemical devices to accomplish energy efficient dissociation of methane hydrate gases in deep ocean sediments. Concepts for use of electrochemical devices

  11. Energy Gradients Structure Microbial Communities Across Sediment Horizons in Deep Marine Sediments of the South China Sea

    Directory of Open Access Journals (Sweden)

    Michael F. Graw

    2018-04-01

    Full Text Available The deep marine subsurface is a heterogeneous environment in which the assembly of microbial communities is thought to be controlled by a combination of organic matter deposition, electron acceptor availability, and sedimentology. However, the relative importance of these factors in structuring microbial communities in marine sediments remains unclear. The South China Sea (SCS experiences significant variability in sedimentation across the basin and features discrete changes in sedimentology as a result of episodic deposition of turbidites and volcanic ashes within lithogenic clays and siliceous or calcareous ooze deposits throughout the basin's history. Deep subsurface microbial communities were recently sampled by the International Ocean Discovery Program (IODP at three locations in the SCS with sedimentation rates of 5, 12, and 20 cm per thousand years. Here, we used Illumina sequencing of the 16S ribosomal RNA gene to characterize deep subsurface microbial communities from distinct sediment types at these sites. Communities across all sites were dominated by several poorly characterized taxa implicated in organic matter degradation, including Atribacteria, Dehalococcoidia, and Aerophobetes. Sulfate-reducing bacteria comprised only 4% of the community across sulfate-bearing sediments from multiple cores and did not change in abundance in sediments from the methanogenic zone at the site with the lowest sedimentation rate. Microbial communities were significantly structured by sediment age and the availability of sulfate as an electron acceptor in pore waters. However, microbial communities demonstrated no partitioning based on the sediment type they inhabited. These results indicate that microbial communities in the SCS are structured by the availability of electron donors and acceptors rather than sedimentological characteristics.

  12. Biogeographical distribution and diversity of microbes in methane hydrate-bearing deep marine sediments, on the Pacific Ocean Margin

    DEFF Research Database (Denmark)

    Inagaki, F.; Nunoura, T.; Nakagawa, S.

    2006-01-01

    The deep subseafloor biosphere is among the least-understood habitats on Earth, even though the huge microbial biomass therein plays an important role for potential long-term controls on global biogeochemical cycles. We report here the vertical and geographical distribution of microbes and their ......The deep subseafloor biosphere is among the least-understood habitats on Earth, even though the huge microbial biomass therein plays an important role for potential long-term controls on global biogeochemical cycles. We report here the vertical and geographical distribution of microbes...... of the uncultivated Deep-Sea Archaeal Group were consistently the dominant phylotype in sediments associated with methane hydrate. Sediment cores lacking methane hydrates displayed few or no Deep-Sea Archaeal Group phylotypes. Bacterial communities in the methane hydrate-bearing sediments were dominated by members...

  13. Constitutive relationships for ocean sediments subjected to stress and temperature gradients

    International Nuclear Information System (INIS)

    Davies, T.G.; Banerjee, P.K.

    1980-08-01

    The disposal of low-level nuclear wastes by burial in deep sea sediments is an option currently being considered. This report lays the groundwork for an investigation of the stability of canisters containing nuclear wastes against movement due to fluidisation of the surrounding sediments, where such fluidisation may result from thermally induced stresses. The requisite constitutive relationships for ocean sediments under stress and temperature gradients are derived from the theory of critical state soil mechanics. A parametric survey has been made of the behaviour of an element of soil in order to assess various models and the importance of the governing parameters, The formulation of a finite element algorithm is given for the solution of the sediment stability problem. (author)

  14. Sinking rates and ballast composition of particles in the Atlantic Ocean: implications for the organic carbon fluxes to the deep ocean

    Science.gov (United States)

    Fischer, G.; Karakaş, G.

    2009-01-01

    The flux of materials to the deep sea is dominated by larger, organic-rich particles with sinking rates varying between a few meters and several hundred meters per day. Mineral ballast may regulate the transfer of organic matter and other components by determining the sinking rates, e.g. via particle density. We calculated particle sinking rates from mass flux patterns and alkenone measurements applying the results of sediment trap experiments from the Atlantic Ocean. We have indication for higher particle sinking rates in carbonate-dominated production systems when considering both regional and seasonal data. During a summer coccolithophorid bloom in the Cape Blanc coastal upwelling off Mauritania, particle sinking rates reached almost 570 m per day, most probably due the fast sedimentation of densely packed zooplankton fecal pellets, which transport high amounts of organic carbon associated with coccoliths to the deep ocean despite rather low production. During the recurring winter-spring blooms off NW Africa and in opal-rich production systems of the Southern Ocean, sinking rates of larger particles, most probably diatom aggregates, showed a tendency to lower values. However, there is no straightforward relationship between carbonate content and particle sinking rates. This could be due to the unknown composition of carbonate and/or the influence of particle size and shape on sinking rates. It also remains noticeable that the highest sinking rates occurred in dust-rich ocean regions off NW Africa, but this issue deserves further detailed field and laboratory investigations. We obtained increasing sinking rates with depth. By using a seven-compartment biogeochemical model, it was shown that the deep ocean organic carbon flux at a mesotrophic sediment trap site off Cape Blanc can be captured fairly well using seasonal variable particle sinking rates. Our model provides a total organic carbon flux of 0.29 Tg per year down to 3000 m off the NW African upwelling

  15. Climate, carbon cycling, and deep-ocean ecosystems.

    Science.gov (United States)

    Smith, K L; Ruhl, H A; Bett, B J; Billett, D S M; Lampitt, R S; Kaufmann, R S

    2009-11-17

    Climate variation affects surface ocean processes and the production of organic carbon, which ultimately comprises the primary food supply to the deep-sea ecosystems that occupy approximately 60% of the Earth's surface. Warming trends in atmospheric and upper ocean temperatures, attributed to anthropogenic influence, have occurred over the past four decades. Changes in upper ocean temperature influence stratification and can affect the availability of nutrients for phytoplankton production. Global warming has been predicted to intensify stratification and reduce vertical mixing. Research also suggests that such reduced mixing will enhance variability in primary production and carbon export flux to the deep sea. The dependence of deep-sea communities on surface water production has raised important questions about how climate change will affect carbon cycling and deep-ocean ecosystem function. Recently, unprecedented time-series studies conducted over the past two decades in the North Pacific and the North Atlantic at >4,000-m depth have revealed unexpectedly large changes in deep-ocean ecosystems significantly correlated to climate-driven changes in the surface ocean that can impact the global carbon cycle. Climate-driven variation affects oceanic communities from surface waters to the much-overlooked deep sea and will have impacts on the global carbon cycle. Data from these two widely separated areas of the deep ocean provide compelling evidence that changes in climate can readily influence deep-sea processes. However, the limited geographic coverage of these existing time-series studies stresses the importance of developing a more global effort to monitor deep-sea ecosystems under modern conditions of rapidly changing climate.

  16. Systems analysis approach to the disposal of high-level waste in deep ocean sediments

    International Nuclear Information System (INIS)

    Marsily, G. de; Hill, M.D.; Murray, C.N.; Talbert, D.M.; Van Dorp, F.; Webb, G.A.M.

    1980-01-01

    Among the different options being studied for disposal of high-level solidified waste, increasing attention is being paid to that of emplacement of glasses incorporating the radioactivity in deep oceanic sediments. This option has the advantage that the areas of the oceans under investigation appear to be relatively unproductive biologically, are relatively free from cataclysmic events, and are areas in which the natural processes are slow. Thus the environment is stable and predictable so that a number of barriers to the release and dispersion of radioactivity can be defined. Task Groups set up in the framework of the International Seabed Working Group have been studying many aspects of this option since 1976. In order that the various parts of the problem can be assessed within an integrated framework, the methods of systems analysis have been applied. In this paper the Systems Analysis Task Group members report the development of an overall system model. This will be used in an iterative process in which a preliminary analysis, together with a sensitivity analysis, identifies the parameters and data of most importance. The work of the other task groups will then be focussed on these parameters and data requirements so that improved results can be fed back into an improved overall systems model. The major requirements for the development of a preliminary overall systems model are that the problem should be separated into identified elements and that the interfaces between the elements should be clearly defined. The model evolved is deterministic and defines the problem elements needed to estimate doses to man

  17. Deep Ocean Contribution to Sea Level Rise

    Science.gov (United States)

    Chang, L.; Sun, W.; Tang, H.; Wang, Q.

    2017-12-01

    The ocean temperature and salinity change in the upper 2000m can be detected by Argo floats, so we can know the steric height change of the ocean. But the ocean layers above 2000m represent only 50% of the total ocean volume. Although the temperature and salinity change are small compared to the upper ocean, the deep ocean contribution to sea level might be significant because of its large volume. There has been some research on the deep ocean rely on the very sparse situ observation and are limited to decadal and longer-term rates of change. The available observational data in the deep ocean are too spares to determine the temporal variability, and the long-term changes may have a bias. We will use the Argo date and combine the situ data and topographic data to estimate the temperature and salinity of the sea water below 2000m, so we can obtain a monthly data. We will analyze the seasonal and annual change of the steric height change due to the deep ocean between 2005 and 2016. And we will evaluate the result combination the present-day satellite and in situ observing systems. The deep ocean contribution can be inferred indirectly as the difference between the altimetry minus GRACE and Argo-based steric sea level.

  18. U- and Th-series nuclides in settling particles: implications to sediment transport through surface waters and interior ocean

    International Nuclear Information System (INIS)

    Sarin, M.M.

    2012-01-01

    The Bay of Bengal is a unique ocean basin receiving large quantities of fresh water and sediment supply from several rivers draining the Indian subcontinent. The annual flux of suspended sediments discharged into the Bay of Bengal is one billion tons, about one-tenth of the global sediment discharge into the ocean. The water and sediment discharge to the Bay, show significant seasonal variation, with maximum transport coinciding with the SW-monsoon (July-September). Earlier studies on the distribution of clay minerals in sediments have led to the suggestion that the sediments of the western Bengal Fan are mainly derived from the Peninsular rivers, whereas rest of the Fan sediments is influenced by the Himalayan rivers. Settling fluxes of particulate matter through the water column of the Bay of Bengal show seasonal trends resulting from monsoon enhanced sediment supply via rivers and biological processes in the water column. It is, thus, important to understand the influence of the seasonally varying particle fluxes on the solute-particle interactions and chemical scavenging processes in the surface and deep waters of the Bay of Bengal. In this context, measurements of U- and Th-series nuclides in the settling particles are most relevant. The radionuclide fluxes ( 230 Th, 228 Th and 210 Pb) in the settling particles provide insight into the role of their removal by vertical particle flux and/or lateral transport (removal at the ocean boundaries). A study carried out in the Northern Bay of Bengal documents that the authigenic flux of 230 Th, as measured in sediment trap samples from deep waters, is balanced by its production in the overhead water column. The sediment mass flux, Al and 228 Th fluxes are similar in the settling particles through shallow and deep waters, suggesting predominant removal by vertical particle flux in the North Bay of Bengal. In the Central Bay, particulate mass, Al and 228 Th fluxes are higher in the trap material from deep waters relative

  19. Radiological aspects of sea bed dumping in the deep oceans

    International Nuclear Information System (INIS)

    Templeton, W.L.

    1979-01-01

    In order to control coastal discharges or ocean dumping of any kind of material, it is necessary to determine a release rate. This can only come from a knowledge of the composition and chemical form of the source materials, the distribution and bioavailability of these materials in the ocean ecosystem, the degree and rates of bioaccumulation and the actual or potential use of the ocean resources. With this information release rates within acceptable limits for man and the ecosystem can then be determined. Today, probably the only situations which apply this approach are the controlled disposal of radioactive wastes. In this paper a recent radiological assessment of the dumping of packaged radioactive wastes on the seabed is discussed and some environmental aspects of the United States Department of Energy program are described examining the feasibility of the emplacement of contained radioactive wastes within the deep ocean sediments

  20. Microbial processes in North Atlantic pelagic sediments, and potential risks of deep-sea waste disposal

    International Nuclear Information System (INIS)

    Bolliger, R.; Hanselmann, K.W.; Bachofen, R.

    1989-01-01

    From the results for waste disposal on deep sea sediments, it was concluded: As waste canisters are buried in the sediment to a depth of 15 to 20 cm, they are in contact with the zone that contains the highest potential bacterial activity through a relatively large surface. An input of oxidizable organic matter to the sediment surface zone will stimulate microbial activity and therefore increase the risk for solubilization and redistribution of elements in the ocean water. Waste canisters lying on the sediment surface cut off the oxygen supply from the ocean water and ease the shift to anaerobiosis. This initiates microbial activities through which metals are changed into their mobile species as a consequence of the altered environmental redox potential. The risk for steel corrosion by hydrogen sulfide, which could be produced by sulfate reducing bacteria, is minimal since this physiological group is not active in the North Atlantic sediments examined

  1. Early Paleogene variations in the calcite compensation depth: new constraints using old borehole sediments from across Ninetyeast Ridge, central Indian Ocean

    Science.gov (United States)

    Slotnick, B. S.; Lauretano, V.; Backman, J.; Dickens, G. R.; Sluijs, A.; Lourens, L.

    2015-03-01

    Major variations in global carbon cycling occurred between 62 and 48 Ma, and these very likely related to changes in the total carbon inventory of the ocean-atmosphere system. Based on carbon cycle theory, variations in the mass of the ocean carbon should be reflected in contemporaneous global ocean carbonate accumulation on the seafloor and, thereby, the depth of the calcite compensation depth (CCD). To better constrain the cause and magnitude of these changes, the community needs early Paleogene carbon isotope and carbonate accumulation records from widely separated deep-sea sediment sections, especially including the Indian Ocean. Several CCD reconstructions for this time interval have been generated using scientific drill sites in the Atlantic and Pacific oceans; however, corresponding information from the Indian Ocean has been extremely limited. To assess the depth of the CCD and the potential for renewed scientific drilling of Paleogene sequences in the Indian Ocean, we examine lithologic, nannofossil, carbon isotope, and carbonate content records for late Paleocene - early Eocene sediments recovered at three sites spanning Ninetyeast Ridge: Deep Sea Drilling Project (DSDP) Sites 213 (deep, east), 214 (shallow, central), and 215 (deep, west). The disturbed, discontinuous sediment sections are not ideal, because they were recovered in single holes using rotary coring methods, but remain the best Paleogene sediments available from the central Indian Ocean. The δ13C records at Sites 213 and 215 are similar to those generated at several locations in the Atlantic and Pacific, including the prominent high in δ13C across the Paleocene carbon isotope maximum (PCIM) at Site 215, and the prominent low in δ13C across the early Eocene Climatic Optimum (EECO) at both Site 213 and Site 215. The Paleocene-Eocene thermal maximum (PETM) and the K/X event are found at Site 213 but not at Site 215, presumably because of coring gaps. Carbonate content at both Sites 213 and

  2. The feasibility of heat generating waste disposal into deep ocean sedimentary formations

    International Nuclear Information System (INIS)

    Murray, C.N.

    1986-01-01

    The paper briefly reviews the work undertaken to date by the Commission of European Communities ''Sub-Seabed Program'' in collaboration with national programmes of member countries. Special emphasis has been placed on the studies of the characteristics of deep ocean sediments to act as a barrier to the dispersion of radionuclides and the technical investigations carried out to demonstrate engineering feasibility of the option. (author)

  3. An instrument to measure differential pore pressures in deep ocean sediments: Pop-Up-Pore-Pressure-Instrument (PUPPI)

    International Nuclear Information System (INIS)

    Schultheiss, P.J.; McPhail, S.D.; Packwood, A.R.; Hart, B.

    1985-01-01

    A Pop-Up-Pore-Pressure-Instrument (PUPPI) has been developed to measure differential pore pressures in sediments. The differential pressure is the pressure above or below normal hydrostatic pressure at the depth of the measurement. It is designed to operate in water depths up to 6000 metres for periods of weeks or months, if required, and measures differential pore pressures at depths of up to 3 metres into the sediments with a resolution of 0.05 kPa. It is a free-fall device with a lance which penetrates the sediments. This lance and the ballast weight is disposed when the PUPPI is acoustically released from the sea floor. When combined with permeability and porosity values of deep-sea sediments the pore pressure measurements made using the PUPPI suggest advection velocities as low as 8.8 mm/yr. The mechanical, electrical and acoustic systems are described together with data obtained from both shallow and deep water trials. (author)

  4. Biodiversity of nematode assemblages from deep-sea sediments of the Atacama Slope and Trench (South Pacific Ocean)

    Science.gov (United States)

    Gambi, C.; Vanreusel, A.; Danovaro, R.

    2003-01-01

    Nematode assemblages were investigated (in terms of size spectra, sex ratio, Shannon diversity, trophic structure and diversity, rarefaction statistics, maturity index, taxonomic diversity and taxonomic distinctness) at bathyal and hadal depths (from 1050 to 7800 m) in the deepest trench of the South Pacific Ocean: the Trench of Atacama. This area, characterised by very high concentrations of nutritionally-rich organic matter also at 7800-m depth, displayed characteristics typical of eutrophic systems and revealed high nematode densities (>6000 ind. 10 cm -2). Nematode assemblages from the Atacama Trench displayed a different composition than at bathyal depths. At bathyal depths 95 genera and 119 species were found (Comesomatidae, Cyatholaimidae, Microlaimidae, Desmodoridae and Xyalidae being dominant), whereas in the Atacama Trench only 29 genera and 37 species were encountered (dominated by Monhysteridae, Chromadoridae, Microlaimidae, Oxystominidae and Xyalidae). The genus Monhystera (24.4%) strongly dominated at hadal depths and Neochromadora, and Trileptium were observed only in the Atacama Trench, but not at bathyal depths. A reduction of the mean nematode size (by ca. 67%) was observed between bathyal and hadal depths. Since food availability was not a limiting factor in the Atacama Trench sediments, other causes are likely to be responsible for the reduction of nematode species richness and body size. The presence of a restricted number of families and genera in the Atacama Trench might indicate that hadal sediments limited nematode colonisation. Most of the genera reaching very high densities in Trench sediments (e.g., Monhystera) are opportunistic and were responsible for the significant decrease of the maturity index. The dominance of opportunists, which are known to be characterised by small sizes, might have contributed to the reduced nematode size at hadal depths. Shannon diversity and species richness decreased in hadal water depth and this pattern

  5. Thorium content in bottom sediments of Pacific and Indian oceans

    International Nuclear Information System (INIS)

    Gurvich, E.G.; Lisitsyn, A.P.

    1980-01-01

    Presented are the results of 232 Th distribution study in different substance-genetic types of bottom sediments of Pacific and Indian oceans. Th content determination has been carried out by the method of instrumental neutron activation analysis. Th distribution maps in the surface layer of bottom sediments of Pacific and Indian oceans are drawn. It is noted that Indian ocean sediments are much richer with Th moreover Th distribution in different types of sediments is very non-uniform. Non-uniformity of Th distribution in different types of Pacific ocean sediments is considerably less than that of Indian ocean and exceeds it only in red oozes

  6. Bacterial Community Response in Deep Faroe-Shetland Channel Sediments Following Hydrocarbon Entrainment With and Without Dispersant Addition

    Directory of Open Access Journals (Sweden)

    Luis J. Perez Calderon

    2018-05-01

    Full Text Available Deep sea oil exploration is increasing and presents environmental challenges for deep ocean ecosystems. Marine oil spills often result in contamination of sediments with oil; following the Deepwater Horizon (DwH disaster up to 31% of the released oil entrained in the water column was deposited as oily residues on the seabed. Although the aftermath of DwH was studied intensely, lessons learned may not be directly transferable to other deep-sea hydrocarbon exploration areas, such as the Faroe-Shetland Channel (FSC which comprises cold temperatures and a unique hydrodynamic regime. Here, transport of hydrocarbons into deep FSC sediments, subsequent responses in benthic microbial populations and effects of dispersant application on hydrocarbon fate and microbial communities were investigated. Sediments from 1,000 m in the FSC were incubated at 0°C for 71 days after addition of a 20-hydrocarbon component oil-sediment aggregate. Dispersant was added periodically from day 4. An additional set of cores using sterilized and homogenized sediment was analyzed to evaluate the effects of sediment matrix modification on hydrocarbon entrainment. Sediment layers were independently analyzed for hydrocarbon content by gas chromatography with flame ionization detection and modeled with linear mixed effects models. Oil was entrained over 4 cm deep into FSC sediments after 42 days and dispersant effectiveness on hydrocarbon removal from sediment to the water column decreased with time. Sterilizing and homogenizing sediment resulted in hydrocarbon transport over 4 cm into sediments after 7 days. Significant shifts in bacterial populations were observed (DGGE profiling in response to hydrocarbon exposure after 42 days and below 2 cm deep. Dispersant application resulted in an accelerated and modified shift in bacterial communities. Bacterial 16S rRNA gene sequencing of oiled sediments revealed dominance of Colwellia and of Fusibacter when dispersant was applied over

  7. Age-dependent mixing of deep-sea sediments

    International Nuclear Information System (INIS)

    Smith, C.R.; Maggaard, L.; Pope, R.H.; DeMaster, D.J.

    1993-01-01

    Rates of bioturbation measured in deep-sea sediments commonly are tracer dependent; in particular, shorter lived radiotracers (such as 234 Th) often yield markedly higher diffusive mixing coefficients than their longer-lived counterparts (e.g., 210 Pb). At a single station in the 1,240-m deep Santa Catalina Basin, the authors document a strong negative correlation between bioturbation rate and tracer half-life. Sediment profiles of 234 Th (half-life = 24 days) yield an average mixing coefficient (60 cm 2 y -1 ) two orders of magnitude greater than that for 210 Pb (half-life = 22 y, mean mixing coefficient = 0.4 cm 2 y -1 ). A similar negative relationship between mixing rate and tracer time scale is observed at thirteen other deep-sea sites in which multiple radiotracers have been used to assess diffusive mixing rates. This relationship holds across a variety of radiotracer types and time scales. The authors hypothesize that this negative relationship results from age-dependent mixing, a process in which recently sedimented, food-rich particles are ingested and mixed at higher rates by deposit feeders than are older, food-poor particles. Results from an age-dependent mixing model demonstrate that this process indeed can yield the bioturbation-rate vs. tracer-time-scale correlations observed in deep-sea sediments. Field data on mixing rates of recently sedimented particles, as well as the radiotracer activity of deep-sea deposit feeders, provide strong support for the age-dependent mixing model. The presence of age-dependent mixing in deep-sea sediments may have major implications for diagenetic modeling, requiring a match between the characteristic time scales of mixing tracers and modeled reactants. 102 refs., 6 figs., 5 tabs

  8. Transport and deposition of plutonium in the ocean: Evidence from Gulf of Mexico sediments

    International Nuclear Information System (INIS)

    Scott, M.R.; Salter, P.F.; Halverson, J.E.

    1983-01-01

    A study of sediments in the Gulf of Mexico shows dramatic gradients in Pu content and isotope ratios from the continental shelf to the Sigsbee Abyssal Plain. In terms of predicted direct fallout inventory of Pu, one shelf core contains 745% of the predicted inventory, while abyssal plain sediments contain only 15-20% of the predicted value. Absolute Pu concentrations of shelf sediments are also conspicuously high, up to 110 dpm/kg, compared to 13.5 dpm/kg in Mississippi River suspended sediment. There is no evidence of Pu remobilization in Gulf of Mexico shelf sediments, based on comparison of Pu profiles with Mn/Al and Fe/Al profiles. Horizontal transport of fallout nuclides from the open ocean to removal sites in ocean margin sediments is concluded to be the source of both the high concentrations and high inventories of Pu reported here. The shelf sediments show 240 Pu/ 239 Pu ratios close to 0.179, the average stratospheric fallout value, but the ratios decrease progressively across the Gulf to low values of 0.06 in abyssal plain sediments. The source of low-ratio Pu in deep-water sediments may be debris from low yield tests transported in the troposphere. Alternatively, it may represent a fraction of the Pu from global stratospheric fallout which has been separated in the water column from the remainder of the Pu in the ocean. In either case, the low-ratio material must have been removed rapidly to the sea floor where it composes a major fraction of the Pu in abyssal plain sediments. Pu delivered by global atmospheric fallout from the stratosphere has apparently remained for the most part in the water or has been transported horizontally and removed into shallow-water sediments. (orig.)

  9. Global Ocean Sedimentation Patterns: Plate Tectonic History Versus Climate Change

    Science.gov (United States)

    Goswami, A.; Reynolds, E.; Olson, P.; Hinnov, L. A.; Gnanadesikan, A.

    2014-12-01

    Global sediment data (Whittaker et al., 2013) and carbonate content data (Archer, 1996) allows examination of ocean sedimentation evolution with respect to age of the underlying ocean crust (Müller et al., 2008). From these data, we construct time series of ocean sediment thickness and carbonate deposition rate for the Atlantic, Pacific, and Indian ocean basins for the past 120 Ma. These time series are unique to each basin and reflect an integrated response to plate tectonics and climate change. The goal is to parameterize ocean sedimentation tied to crustal age for paleoclimate studies. For each basin, total sediment thickness and carbonate deposition rate from 0.1 x 0.1 degree cells are binned according to basement crustal age; area-corrected moments (mean, variance, etc.) are calculated for each bin. Segmented linear fits identify trends in present-day carbonate deposition rates and changes in ocean sedimentation from 0 to 120 Ma. In the North and South Atlantic and Indian oceans, mean sediment thickness versus crustal age is well represented by three linear segments, with the slope of each segment increasing with increasing crustal age. However, the transition age between linear segments varies among the three basins. In contrast, mean sediment thickness in the North and South Pacific oceans are numerically smaller and well represented by two linear segments with slopes that decrease with increasing crustal age. These opposing trends are more consistent with the plate tectonic history of each basin being the controlling factor in sedimentation rates, rather than climate change. Unlike total sediment thickness, carbonate deposition rates decrease smoothly with crustal age in all basins, with the primary controls being ocean chemistry and water column depth.References: Archer, D., 1996, Global Biogeochem. Cycles 10, 159-174.Müller, R.D., et al., 2008, Science, 319, 1357-1362.Whittaker, J., et al., 2013, Geochem., Geophys., Geosyst. DOI: 10.1002/ggge.20181

  10. Hard substrate in the deep ocean: How sediment features influence epibenthic megafauna on the eastern Canadian margin

    Science.gov (United States)

    Lacharité, Myriam; Metaxas, Anna

    2017-08-01

    Benthic habitats on deep continental margins (> 1000 m) are now considered heterogeneous - in particular because of the occasional presence of hard substrate in a matrix of sand and mud - influencing the distribution of megafauna which can thrive on both sedimented and rocky substrates. At these depths, optical imagery captured with high-definition cameras to describe megafauna can also describe effectively the fine-scale sediment properties in the immediate vicinity of the fauna. In this study, we determined the relationship between local heterogeneity (10-100 sm) in fine-scale sediment properties and the abundance, composition, and diversity of megafauna along a large depth gradient (1000-3000 m) in a previously-unexplored habitat: the Northeast Fan, which lies downslope of submarine canyons off the Gulf of Maine (northwest Atlantic). Substrate heterogeneity was quantified using a novel approach based on principles of computer vision. This approach proved powerful in detecting gradients in sediment, and sporadic complex features (i.e. large boulders) in an otherwise homogeneous environment because it characterizes sediment properties on a continuous scale. Sediment heterogeneity influenced megafaunal diversity (morphospecies richness and Shannon-Wiener Index) and community composition, with areas of higher substrate complexity generally supported higher diversity. However, patterns in abundance were not influenced by sediment properties, and may be best explained by gradients in food supply. Our study provides a new approach to quantify fine-scale sediment properties and assess their role in shaping megafaunal communities in the deep sea, which should be included into habitat studies given their potential ecological importance.

  11. Enhanced deep ocean ventilation and oxygenation with global warming

    Science.gov (United States)

    Froelicher, T. L.; Jaccard, S.; Dunne, J. P.; Paynter, D.; Gruber, N.

    2014-12-01

    Twenty-first century coupled climate model simulations, observations from the recent past, and theoretical arguments suggest a consistent trend towards warmer ocean temperatures and fresher polar surface oceans in response to increased radiative forcing resulting in increased upper ocean stratification and reduced ventilation and oxygenation of the deep ocean. Paleo-proxy records of the warming at the end of the last ice age, however, suggests a different outcome, namely a better ventilated and oxygenated deep ocean with global warming. Here we use a four thousand year global warming simulation from a comprehensive Earth System Model (GFDL ESM2M) to show that this conundrum is a consequence of different rates of warming and that the deep ocean is actually better ventilated and oxygenated in a future warmer equilibrated climate consistent with paleo-proxy records. The enhanced deep ocean ventilation in the Southern Ocean occurs in spite of increased positive surface buoyancy fluxes and a constancy of the Southern Hemisphere westerly winds - circumstances that would otherwise be expected to lead to a reduction in deep ocean ventilation. This ventilation recovery occurs through a global scale interaction of the Atlantic Meridional Overturning Circulation undergoing a multi-centennial recovery after an initial century of transient decrease and transports salinity-rich waters inform the subtropical surface ocean to the Southern Ocean interior on multi-century timescales. The subsequent upwelling of salinity-rich waters in the Southern Ocean strips away the freshwater cap that maintains vertical stability and increases open ocean convection and the formation of Antarctic Bottom Waters. As a result, the global ocean oxygen content and the nutrient supply from the deep ocean to the surface are higher in a warmer ocean. The implications for past and future changes in ocean heat and carbon storage will be discussed.

  12. DEEP BIOSPHERE. Exploring deep microbial life in coal-bearing sediment down to ~2.5 km below the ocean floor.

    Science.gov (United States)

    Inagaki, F; Hinrichs, K-U; Kubo, Y; Bowles, M W; Heuer, V B; Hong, W-L; Hoshino, T; Ijiri, A; Imachi, H; Ito, M; Kaneko, M; Lever, M A; Lin, Y-S; Methé, B A; Morita, S; Morono, Y; Tanikawa, W; Bihan, M; Bowden, S A; Elvert, M; Glombitza, C; Gross, D; Harrington, G J; Hori, T; Li, K; Limmer, D; Liu, C-H; Murayama, M; Ohkouchi, N; Ono, S; Park, Y-S; Phillips, S C; Prieto-Mollar, X; Purkey, M; Riedinger, N; Sanada, Y; Sauvage, J; Snyder, G; Susilawati, R; Takano, Y; Tasumi, E; Terada, T; Tomaru, H; Trembath-Reichert, E; Wang, D T; Yamada, Y

    2015-07-24

    Microbial life inhabits deeply buried marine sediments, but the extent of this vast ecosystem remains poorly constrained. Here we provide evidence for the existence of microbial communities in ~40° to 60°C sediment associated with lignite coal beds at ~1.5 to 2.5 km below the seafloor in the Pacific Ocean off Japan. Microbial methanogenesis was indicated by the isotopic compositions of methane and carbon dioxide, biomarkers, cultivation data, and gas compositions. Concentrations of indigenous microbial cells below 1.5 km ranged from <10 to ~10(4) cells cm(-3). Peak concentrations occurred in lignite layers, where communities differed markedly from shallower subseafloor communities and instead resembled organotrophic communities in forest soils. This suggests that terrigenous sediments retain indigenous community members tens of millions of years after burial in the seabed. Copyright © 2015, American Association for the Advancement of Science.

  13. Application of systems analysis to the disposal of high level waste in deep ocean sediments

    International Nuclear Information System (INIS)

    De Marsily, G.; Dorp, F. van

    1982-01-01

    Emplacement in deep ocean sediments is one of the disposal options being considered for solidified high level radioactive waste. Task groups set up within the framework of the NEA Seabed Working Group have been studying many aspects of this option since 1976. The methods of systems analysis have been applied to enable the various parts of the problem to be assessed within an integrated framework. This paper describes the progress made by the Systems Analysis Task Group towards the development of an overall system model. The Task Group began by separating the problem into elements and defining the interfaces between these elements. A simple overall system model was then developed and used in both a preliminary assessment and a sensitivity analysis to identify the most important parameters. These preliminary analyses used a very simple model of the overall system and therefore the results cannot be used to draw any conclusions as to the acceptability of the sub-seabed disposal option. However they served to show the utility of the systems analysis method. The work of the other task groups will focus on the important parameters so that improved results can be fed back into an improved system model. Subsequent iterations will eventually provide an input to an acceptability decision. (Auth.)

  14. Active microbial community structure of deep subsurface sediments within Baltic Sea Basin

    Science.gov (United States)

    Reese, B. K.; Zinke, L.; Carvalho, G.; Lloyd, K. G.; Marshall, I.; Shumaker, A.; Amend, J.

    2014-12-01

    The Baltic Sea Basin (BSB) is a unique depositional setting that has experienced periods of glaciation and deglaciation as a result of climatic fluctuations over past tens of thousands of years. This has resulted in laminated sediments formed during periods with strong permanent salinity stratification. The high sedimentation rates make this an ideal setting to understand the microbial structure of a deep biosphere community in a relatively high carbon, and thus high-energy environment, compared to other deep subsurface sites. Samples were collected through scientific drilling during the International Ocean Discovery Program (IODP) Expedition 347 on board the Greatship Manisha, September-November 2013. We examined the active microbial community structure using the 16S rRNA gene transcript and active functional genes through metatranscriptome sequencing. Major biogeochemical shifts have been observed in response to the depositional history between the limnic, brackish, and marine phases. The active microbial community structure in the BSB is diverse and reflective of the unique changes in the geochemical profile. These data further refine our understanding of the existence life in the deep subsurface and the survival mechanisms required for this extreme environment.

  15. Feasibility of high level radioactive waste disposal in deep sea sediments

    International Nuclear Information System (INIS)

    Buckley, D.E.

    1987-01-01

    For the past ten years, an international program has been conducted to investigate the concept feasibility for disposing of spent nuclear fuel waste in deep ocean sediments. These studies by the Seabed Working Group were coordinated by the Nuclear Energy Agency of the Organization for Economic Cooperation and Development. Penetrators have been considered as the primary method of waste emplacement. This required emphasis on studies of the nature of the plastic sediments which would form the primary barrier to the release of radionuclides into the biosphere. Site qualification guidelines, included criteria for tectonic and sedimentary stability over periods of at least 10 5 years. Using these guidelines two potential areas were identified: one in the Madeira Abyssal Plain; and one in the Southern Nares Abyssal Plain, both in the North Atlantic

  16. Ocean floor sediment as a repository barrier: comparative diffusion data for selected radionuclides in sediments from the Atlantic and Pacific Oceans

    International Nuclear Information System (INIS)

    Schreiner, F.; Sabau, C.; Friedman, A.; Fried, S.

    1986-01-01

    Effective diffusion coefficients for selected radionuclides have been measured in ocean floor sediments to provide data for the assessment of barrier effectiveness in subseabed repositories for nuclear waste. The sediments tested include illite-rich and smectite-rich red clays from the mid plate gyre region of the Pacific Ocean, reducing sediment from the continental shelf of the northwest coast of North America, and Atlantic Ocean sediments from the Southern Nares Abyssal Plain and the Great Meteor East region. Results show extremely small effective diffusion coefficients with values less than 10 -14 m 2 s -1 for plutonium, americium, curium, thorium, and tin. Radionuclides with high diffusion coefficients of approximately 10 -10 m 2 s - include the anionic species pertechnetate, TcO 4 - , iodide, I - , and selenite, SO 3 -2 . Uranyl(VI) and neptunyl(V) ions, which are stable in solution, have diffusion coefficients around 10 -12 m 2 s -1 . The diffusion behavior of most radionuclides is similar in the oxygenated Pacific sediments and in the anoxic sediments from the Atlantic. An exception is neptunium, which is immobilized by Great Meteor East sediment, but has high mobility in Southern Nares Abyssal Plain sediment. Under stagnant conditions a 30 m thick sediment layer forms an effective geologic barrier isolating radionuclides in a subseabed repository from the biosphere

  17. Ocean floor sediment as a repository barrier: comparative diffusion data for selected radionuclides in sediments from the Atlantic and Pacific Oceans

    International Nuclear Information System (INIS)

    Schreiner, F.; Sabau, C.; Friedman, A.; Fried, S.

    1985-01-01

    Effective diffusion coefficients for selected radionuclides have been measured in ocean floor sediments to provide data for the assessment of barrier effectiveness in subseabed repositories for nuclear waste. The sediments tested include illite-rich and smectite-rich red clays from the mid-plate gyre region of the Pacific Ocean, reducing sediment from the continental shelf of the northwest coast of North America, and Atlantic Ocean sediments from the Southern Nares Abyssal Plain and the Great Meteor East region. Results show extremely small effective diffusion coefficients with values less than 10 -14 m 2 s -1 for plutonium, americium, curium, thorium, and tin. Radionuclides with high diffusion coefficients of approximately 10 -10 m 2 s -1 include the anionic species pertechnetate, TcO 4 - , iodide, I - , and selenite, SeO 3 -2 . Uranyl(VI) and neptunyl(V) ions, which are stable in solution, have diffusion coefficients around 10 -12 m 2 s -1 . The diffusion behavior of most radionuclides is similar in the oxygenated Pacific sediments and in the anoxic sediments from the Atlantic. An exception is neptunium, which is immobilized by Great Meteor East sediment, but has high mobility in Southern Nares Abyssal Plain sediment. Under stagnant conditions a 30 m thick sediment layer forms an effective geologic barrier isolating radionuclides in a subseabed repository from the biosphere. 13 refs., 5 figs., 1 tab

  18. Impacts of ocean acidification on sediment processes in shallow waters of the Arctic Ocean.

    Science.gov (United States)

    Gazeau, Frédéric; van Rijswijk, Pieter; Pozzato, Lara; Middelburg, Jack J

    2014-01-01

    Despite the important roles of shallow-water sediments in global biogeochemical cycling, the effects of ocean acidification on sedimentary processes have received relatively little attention. As high-latitude cold waters can absorb more CO2 and usually have a lower buffering capacity than warmer waters, acidification rates in these areas are faster than those in sub-tropical regions. The present study investigates the effects of ocean acidification on sediment composition, processes and sediment-water fluxes in an Arctic coastal system. Undisturbed sediment cores, exempt of large dwelling organisms, were collected, incubated for a period of 14 days, and subject to a gradient of pCO2 covering the range of values projected for the end of the century. On five occasions during the experimental period, the sediment cores were isolated for flux measurements (oxygen, alkalinity, dissolved inorganic carbon, ammonium, nitrate, nitrite, phosphate and silicate). At the end of the experimental period, denitrification rates were measured and sediment samples were taken at several depth intervals for solid-phase analyses. Most of the parameters and processes (i.e. mineralization, denitrification) investigated showed no relationship with the overlying seawater pH, suggesting that ocean acidification will have limited impacts on the microbial activity and associated sediment-water fluxes on Arctic shelves, in the absence of active bio-irrigating organisms. Only following a pH decrease of 1 pH unit, not foreseen in the coming 300 years, significant enhancements of calcium carbonate dissolution and anammox rates were observed. Longer-term experiments on different sediment types are still required to confirm the limited impact of ocean acidification on shallow Arctic sediment processes as observed in this study.

  19. Human-associated fungi in deep subseafloor sediment?

    Science.gov (United States)

    Fulfer, V. M.; Kirkpatrick, J. B.; D'Hondt, S.

    2015-12-01

    Recent studies have reported fungi in marine sediment samples from depths as great as 1740 meters below seafloor (mbsf) (Rédou et al., 2014). Such studies have utilized a variety of techniques to identify fungi, including cultivation of isolates, amplicon sequencing, and metagenomics. Six recent studies of marine sediment collectively identify nearly 100 fungal taxa at the genus and species levels (Damare et al., 2006; Lai et al., 2007; Edgcomb et al., 2010; Singh et al., 2010; Orsi et al., 2013; Rédou et al., 2014). Known marine taxa are rarely identified by these studies. For individual studies with more than two taxa, between 16% and 57% of the fungal taxa are human microflora or associated with human environments (e.g., human skin or indoor air). For example, three of the six studies identified Malassezia species that are common skin inhabitants of humans and dogs. Although human-associated taxa have been identified in both shallow and deep sediment, they pose a particularly acute problem for deep subseafloor samples, where claims of a eukaryotic deep biosphere are most striking; depending on the study, 25% to 38% of species identified in sediment taken at depths greater than 40 meters are human-associated. Only one to three species have been reported from each of the four samples taken at depths greater than one km (eight species total; Rédou et al., 2014). Of these eight species, three are human-associated. This ubiquity of human-associated microflora is very problematic for interpretations of an indigenous deep subseafloor fungal community; either human-associated taxa comprise a large fraction of marine sedimentary fungi, or sample and analytical contamination is so widespread that the extent and ubiquity of a deep subseafloor fungal community remains uncertain. This highlights the need for stringent quality control measures throughout coring, sampling, and recovery of marine sediment, and when cultivating, extracting, and/or sequencing fungi from

  20. Reverse transcriptase directs viral evolution in a deep ocean methane seep

    Science.gov (United States)

    Paul, B. G.; Bagby, S. C.

    2013-12-01

    Deep ocean methane seeps are sites of intense microbial activity, with complex communities fueled by aerobic and anaerobic methanotrophy. Methane consumption in these communities has a substantial impact on the global carbon cycle, yet little is known about their evolutionary history or their likely evolutionary trajectories in a warming ocean. As in other marine systems, viral predation and virally mediated horizontal gene transfer are expected to be major drivers of evolutionary change in these communities; however, the host cells' resistance to cultivation has impeded direct study of the viral population. We conducted a metagenomic study of viruses in the anoxic sediments of a deep methane seep in the Santa Monica Basin in the Southern California Bight. We retrieved 1660 partial viral genomes, tentatively assigning 1232 to bacterial hosts and 428 to archaea. One abundant viral genome, likely hosted by Clostridia species present in the sediment, was found to encode a diversity-generating retroelement (DGR), a module for reverse transcriptase-mediated directed mutagenesis of a distal tail fiber protein. While DGRs have previously been described in the viruses of human pathogens, where diversification of viral tail fibers permits infection of a range of host cell types, to our knowledge this is the first description of such an element in a marine virus. By providing a mechanism for massively broadening potential host range, the presence of DGRs in these systems may have a major impact on the prevalence of virally mediated horizontal gene transfer, and even on the phylogenetic distances across which genes are moved.

  1. Ocean floor sediment as a repository barrier: comparative diffusion data for selected radionuclides in sediments from the Atlantic and Pacific Oceans

    Energy Technology Data Exchange (ETDEWEB)

    Schreiner, F.; Sabau, C.; Friedman, A.; Fried, S.

    1985-01-01

    Effective diffusion coefficients for selected radionuclides have been measured in ocean floor sediments to provide data for the assessment of barrier effectiveness in subseabed repositories for nuclear waste. The sediments tested include illite-rich and smectite-rich red clays from the mid-plate gyre region of the Pacific Ocean, reducing sediment from the continental shelf of the northwest coast of North America, and Atlantic Ocean sediments from the Southern Nares Abyssal Plain and the Great Meteor East region. Results show extremely small effective diffusion coefficients with values less than 10/sup -14/ m/sup 2/s/sup -1/ for plutonium, americium, curium, thorium, and tin. Radionuclides with high diffusion coefficients of approximately 10/sup -10/ m/sup 2/s/sup -1/ include the anionic species pertechnetate, TcO/sub 4//sup -/, iodide, I/sup -/, and selenite, SeO/sub 3//sup -2/. Uranyl(VI) and neptunyl(V) ions, which are stable in solution, have diffusion coefficients around 10/sup -12/ m/sup 2/s/sup -1/. The diffusion behavior of most radionuclides is similar in the oxygenated Pacific sediments and in the anoxic sediments from the Atlantic. An exception is neptunium, which is immobilized by Great Meteor East sediment, but has high mobility in Southern Nares Abyssal Plain sediment. Under stagnant conditions a 30 m thick sediment layer forms an effective geologic barrier isolating radionuclides in a subseabed repository from the biosphere. 13 refs., 5 figs., 1 tab.

  2. Beryllium-10 in continental sediments

    International Nuclear Information System (INIS)

    Brown, L.; Sacks, I.S.; Tera, F.; Klein, J.; Middleton, R.

    1981-01-01

    The concentration of 10 Be has been measured in 10 samples taken from a transect of surface sediments beginning in the Atchafalaya River and extending across the Bay 136 km into the Gulf of Mexico. If corrected for a lower retentivity of sand for Be, they have a concentration that is constant within 13%. This concentration is about an order of magnitude smaller than that of deep ocean sediments. For comparison, measurements of 10 Be in rainwater, in a sample of soil and in a deep ocean core were made. (orig.)

  3. Fungi and macroaggregation in deep-sea sediments

    Digital Repository Service at National Institute of Oceanography (India)

    Damare, S.R.; Raghukumar, C.

    Whereas fungi in terrestrial soils have been well studied, little is known of them in deep-sea sediments. Recent studies have demonstrated the presence of fungal hyphae in such sediments but in low abundance. We present evidence in this study...

  4. Feasibility of high level radioactive waste disposal in deep sea sediments

    International Nuclear Information System (INIS)

    Buckley, D.E.

    1987-01-01

    For the past ten years, an international program has been conducted to investigate the concept feasibility for disposing of spent nuclear fuel waste in deep ocean sediments. These studies by the Seabed Working Group were coordinated by the Nuclear Energy Agency of the Organization for Economic Cooperation and Development. Penetrators have been considered as the primary method of waste emplacement. This required emphasis on studies of the nature of the plastic sediments which would form the primary barrier to the release of radionuclides into the biosphere. Site qualification guidelines, included criteria for tectonic and sedimentary stability over periods of at least 10 5 years. Using these guidelines two potential areas were identified: one in the Madeira Abyssal Plain; and one in the Southern Nares Abyssal Plain, both in the North Atlantic. The sediment barrier properties are quite different in terms of dominant mineralogy (carbonates in MAP, and silicous clays in SNAP). The MAP is dominated by thick wide-spread turbidites, but SNAP is dominated by thin discontinuous turbidites

  5. The role of the sediment barrier

    International Nuclear Information System (INIS)

    Freeman, T.J.; Schultheiss, P.J.; Searle, R.C.; Sills, G.C.; Toolan, F.E.

    1989-01-01

    The conference 'Disposal of radioactive wastes in seabed sediments' was organized by the Society for Underwater Technology to review the potential of certain seabed sediments to provide a long-term containment for radioactive wastes. Its objectives were to assess: (1) what has been learned about the properties and nature of the sediments of the deep ocean; (2) the merits and demerits of the conceptual techniques that have been developed to dispose of waste; and (3) whether what has been learned about deep ocean disposal has any relevance to other areas of marine science. This chapter introduces the subject matter of the conference in the framework of the international research programme and discusses what has been learned about the role of the sediment barrier. (author)

  6. Characterization of Paleoredox Changes In Nw-pacific Deep-sea Sediments Using Environmental Magnetic In Combination With Geochemical-mineralogic Data

    Science.gov (United States)

    Urbat, M.; Pletsch, T.

    The understanding of environmental and oceanic controls on deep-sea sediments in the NW Pacific Ocean (ODP Site 1149A, Nadezhda Basin) benefits from the inte- gration of environmental magnetic methodology with geochemical-mineralogic XRD (x-ray defraction) and XRF (x-ray fluorescence) data. Crucially, the inherently grad- ual diagenetic processes related to paleo-redox changes in the sediment column may be more sensitively monitored using the integration of non-magnetic and magnetic data, because they do reflect various aspects of the entire postdepositional alteration. The studied 32 m long quaternary interval at Hole ODP 1149A provides an expanded record of eolian dust supply from the Asian continent, siliceous plankton accumulation and varying contributions of both discrete ash layers and disperse ash to a truly deep- sea environment (Plank et al. 2000). Recurrent diagenetic intervals appear to be related to changes in the Ocean water circulation (Kuriosho current) and concomitant produc- tivity variations as a function of glacial-interglacial paleoclimatic changes. Diagenetic intervals correspond to paleo-redox boundaries, where suboxic conditions promoted the destruction of the primary magnetic signal (iron oxides) and the precipitation of rhodochrosite (MnCO3). We used simple normative calculations on the basis of of Al and Cr contents to discriminate between the major groups of components (terrigenous, volcanogenic, biogenic, diagenetic) in combination with our magnetic results. These results form the grounds for the discrimation and independent interpretation of the genetically various sediment components in the paleoceanograhic context.

  7. Deep-Sea Corals: A New Oceanic Archive

    National Research Council Canada - National Science Library

    Adkins, Jess

    1998-01-01

    Deep-sea corals are an extraordinary new archive of deep ocean behavior. The species Desmophyllum cristagalli is a solitary coral composed of uranium rich, density banded aragonite that I have calibrated for several paleoclimate tracers...

  8. Single photon light detector for deep ocean applications

    International Nuclear Information System (INIS)

    Matsuno, S.; Babson, J.; Learned, J.G.; O'Connor, D.; Grieder, P.K.F.; Wilson, C.

    1989-01-01

    We have developed a single photon sensitive light detector module which can be operated in the ocean to a depth of 5000 m. It was designed primarily to be used as a Cherenkov light detector in conjunction with the DUMAND (Deep Underwater Muon And Neutrino Detector) experiment. After calibration in the laboratory, seven detectors, assembled in a vertical string geometry, have been operated simultaneously in the deep ocean off the coast of the island of Hawaii. Cosmic ray muons have been recorded successfully at dephts ranging from 2000 to 4000 m. The results have demonstrated the capability of the detector; it fulfills the specifications required for the modules to be used in a deep ocean muon and neutrino detector. (orig.)

  9. Quantitative and phylogenetic study of the Deep Sea Archaeal Group in sediments of the arctic mid-ocean spreading ridge

    Directory of Open Access Journals (Sweden)

    Steffen Leth eJørgensen

    2013-10-01

    Full Text Available In marine sediments archaea often constitute a considerable part of the microbial community, of which the Deep Sea Archaeal Group (DSAG is one of the most predominant. Despite their high abundance no members from this archaeal group have so far been characterized and thus their metabolism is unknown. Here we show that the relative abundance of DSAG marker genes can be correlated with geochemical parameters, allowing prediction of both the potential electron donors and acceptors of these organisms. We estimated the abundance of 16S rRNA genes from Archaea, Bacteria and DSAG in 52 sediment horizons from two cores collected at the slow-spreading Arctic Mid-Ocean Ridge, using qPCR. The results indicate that members of the DSAG make up the entire archaeal population in certain horizons and constitute up to ~ 50% of the total microbial community. The quantitative data were correlated to 30 different geophysical and geochemical parameters obtained from the same sediment horizons. We observed a significant correlation between the relative abundance of DSAG 16S rRNA genes and the content of organic carbon (p < 0.0001. Further, significant co-variation with iron oxide, and dissolved iron and manganese (all p < 0.0000, indicated a direct or indirect link to iron and manganese cycling. Neither of these parameters correlated with the relative abundance of archaeal or bacterial 16S rRNA genes, nor did any other major electron donor or acceptor measured. Phylogenetic analysis of DSAG 16S rRNA gene sequences reveals three monophyletic lineages with no apparent habitat-specific distribution. In this study we support the hypothesis that members of the DSAG are tightly linked to the content of organic carbon and directly or indirectly involved in the cycling of iron and/or manganese compounds. Further, we provide a molecular tool to assess their abundance in environmental samples and enrichment cultures.

  10. Investigation of hurricane Ivan using the coupled ocean-atmosphere-wave-sediment transport (COAWST) model

    Science.gov (United States)

    Zambon, Joseph B.; He, Ruoying; Warner, John C.

    2014-01-01

    The coupled ocean–atmosphere–wave–sediment transport (COAWST) model is used to hindcast Hurricane Ivan (2004), an extremely intense tropical cyclone (TC) translating through the Gulf of Mexico. Sensitivity experiments with increasing complexity in ocean–atmosphere–wave coupled exchange processes are performed to assess the impacts of coupling on the predictions of the atmosphere, ocean, and wave environments during the occurrence of a TC. Modest improvement in track but significant improvement in intensity are found when using the fully atmosphere–ocean-wave coupled configuration versus uncoupled (e.g., standalone atmosphere, ocean, or wave) model simulations. Surface wave fields generated in the fully coupled configuration also demonstrates good agreement with in situ buoy measurements. Coupled and uncoupled model-simulated sea surface temperature (SST) fields are compared with both in situ and remote observations. Detailed heat budget analysis reveals that the mixed layer temperature cooling in the deep ocean (on the shelf) is caused primarily by advection (equally by advection and diffusion).

  11. A Moessbauer study of deep sea sediments

    International Nuclear Information System (INIS)

    Minai, Y.; Tominaga, T.; Furuta, T.; Kobayashi, K.

    1981-01-01

    In order to determine the chemical states of iron in deep sea sediments, Moessbauer spectra of the sediments collected from various areas of the Pacific have been measured. The Moessbauer spectra were composed of paramagnetic ferric, high-spin ferrous, and magnetic components. The correlation of their relative abundance to the sampling location and the kind of sediments may afford clues to infer the origin of each iron-bearing phase. (author)

  12. Feasibility of deep ocean disposal of heat generating waste. V.1

    International Nuclear Information System (INIS)

    Hemming, C.R.

    1988-06-01

    This report summarises the research performed in the UK during the period 1977 to 1987 as part of the international programme investigating the feasibility of ocean disposal of heat generating radioactive waste. This study has involved: (i) the definition of the disposal operations needed to meet the minimum requirements for safely emplacing waste on or under the floor of the deep ocean; (ii) the identification and characterisation of areas of the deep ocean that might be suitable for containing heat generating waste; (iii) a study of the processes by which radionuclides might migrate through the multiple barriers that isolate the waste from man's environment; and (iv) a calculation of the radiological impact of the conceptual deep ocean repository. It is concluded that, from a technical and scientific viewpoint, disposal of heat generating waste in the deep ocean could provide a safe, economic and feasible alternative to deep disposal on land. (author)

  13. Let's Bet on Sediments! Hudson Canyon Cruise--Grades 9-12. Focus: Sediments of Hudson Canyon.

    Science.gov (United States)

    National Oceanic and Atmospheric Administration (DOC), Rockville, MD.

    These activities are designed to teach about the sediments of Hudson Canyon. Students investigate and analyze the patterns of sedimentation in the Hudson Canyon, observe how heavier particles sink faster than finer particles, and learn that submarine landslides are avalanches of sediment in deep ocean canyons. The activity provides learning…

  14. Biogeochemical malfunctioning in sediments beneath a deep-water fish farm.

    Science.gov (United States)

    Valdemarsen, Thomas; Bannister, Raymond J; Hansen, Pia K; Holmer, Marianne; Ervik, Arne

    2012-11-01

    We investigated the environmental impact of a deep water fish farm (190 m). Despite deep water and low water currents, sediments underneath the farm were heavily enriched with organic matter, resulting in stimulated biogeochemical cycling. During the first 7 months of the production cycle benthic fluxes were stimulated >29 times for CO(2) and O(2) and >2000 times for NH(4)(+), when compared to the reference site. During the final 11 months, however, benthic fluxes decreased despite increasing sedimentation. Investigations of microbial mineralization revealed that the sediment metabolic capacity was exceeded, which resulted in inhibited microbial mineralization due to negative feed-backs from accumulation of various solutes in pore water. Conclusions are that (1) deep water sediments at 8 °C can metabolize fish farm waste corresponding to 407 and 29 mmol m(-2) d(-1) POC and TN, respectively, and (2) siting fish farms at deep water sites is not a universal solution for reducing benthic impacts. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. Suspended sediment dynamics in a large-scale turbidity current: Direct measurements from the deep-water Congo Canyon

    Science.gov (United States)

    Simmons, S.; Azpiroz, M.; Cartigny, M.; Clare, M. A.; Parsons, D. R.; Sumner, E.; Talling, P. J.

    2016-12-01

    Turbidity currents that transport sediment to the deep ocean deposit a greater volume of sediment than any other process on Earth. To date, only a handful of studies have directly measured turbidity currents, with flow durations ranging from a few minutes to a few hours. Our understanding of turbidity current dynamics is therefore largely derived from scaled laboratory experiments and numerical modelling. Recent years have seen the first field-scale measurements of depth-resolved velocity profiles, but sediment concentration (a key parameter for turbidity currents) remains elusive. Here, we present high resolution measurements of deep-water turbidity currents from the Congo Canyon; one of the world's largest submarine canyons. Direct measurements using acoustic Doppler current profilers (ADCPs) show that flows can last for many days, rather than hours as seen elsewhere, and provide the first quantification of concentration and grain size within deep-water turbidity currents.Velocity and backscatter were measured at 5 second intervals by an ADCP suspended 80 m above the canyon floor, at 2000 m water depth. A novel inversion method using multiple ADCP frequencies enabled quantification of sediment concentration and grain size within the flows. We identify high concentrations of coarse sediment within a thin frontal cell, which outruns a thicker, trailing body. Thus, the flows grow in length while propagating down-canyon. This is distinct from classical models and other field-scale measurements of turbidity currents. The slow-moving body is dominated by suspended fine-grained sediment. The body mixes with the surrounding fluid leaving diffuse clouds of sediment that persist for days after initial entrainment. Ambient tidal flow also controls the mixing within the body and the surrounding fluid. Our results provide a new quantification of suspended sediment within flows and the interaction with the surrounding fluid.

  16. Dilution limits dissolved organic carbon utilization in the deep ocean

    KAUST Repository

    Arrieta, Jesus

    2015-03-19

    Oceanic dissolved organic carbon (DOC) is the second largest reservoir of organic carbon in the biosphere. About 72% of the global DOC inventory is stored in deep oceanic layers for years to centuries, supporting the current view that it consists of materials resistant to microbial degradation. An alternative hypothesis is that deep-water DOC consists of many different, intrinsically labile compounds at concentrations too low to compensate for the metabolic costs associated to their utilization. Here, we present experimental evidence showing that low concentrations rather than recalcitrance preclude consumption of a substantial fraction of DOC, leading to slow microbial growth in the deep ocean. These findings demonstrate an alternative mechanism for the long-term storage of labile DOC in the deep ocean, which has been hitherto largely ignored. © 2015, American Association for the Advancement of Science. All rights reserved.

  17. Dilution limits dissolved organic carbon utilization in the deep ocean

    KAUST Repository

    Arrieta, J M; Mayol, Eva; Hansman, Roberta L.; Herndl, Gerhard J.; Dittmar, Thorsten; Duarte, Carlos M.

    2015-01-01

    Oceanic dissolved organic carbon (DOC) is the second largest reservoir of organic carbon in the biosphere. About 72% of the global DOC inventory is stored in deep oceanic layers for years to centuries, supporting the current view that it consists of materials resistant to microbial degradation. An alternative hypothesis is that deep-water DOC consists of many different, intrinsically labile compounds at concentrations too low to compensate for the metabolic costs associated to their utilization. Here, we present experimental evidence showing that low concentrations rather than recalcitrance preclude consumption of a substantial fraction of DOC, leading to slow microbial growth in the deep ocean. These findings demonstrate an alternative mechanism for the long-term storage of labile DOC in the deep ocean, which has been hitherto largely ignored. © 2015, American Association for the Advancement of Science. All rights reserved.

  18. Rare earth element geochemistry of oceanic ferromanganese nodules and associated sediments

    Science.gov (United States)

    Elderfield, H.; Hawkesworth, C. J.; Greaves, M. J.; Calvert, S. E.

    1981-04-01

    Analyses have been made of REE contents of a well-characterized suite of deep-sea (> 4000 m.) principally todorokite-bearing ferromanganese nodules and associated sediments from the Pacific Ocean. REE in nodules and their sediments are closely related: nodules with the largest positive Ce anomalies are found on sediments with the smallest negative Ce anomalies; in contrast, nodules with the highest contents of other rare earths (3 + REE) are found on sediments with the lowest 3 + REE contents and vice versa. 143Nd /144Nd ratios in the nodules (˜0.51244) point to an original seawater source but an identical ratio for sediments in combination with the REE patterns suggests that diagenetic reactions may transfer elements into the nodules. Analysis of biogenic phases shows that the direct contribution of plankton and carbonate and siliceous skeletal materials to REE contents of nodules and sediments is negligible. Inter-element relationships and leaching tests suggest that REE contents are controlled by a P-rich phase with a REE pattern similar to that for biogenous apatite and an Fe-rich phase with a pattern the mirror image of that for sea water. It is proposed that 3 + REE concentrations are controlled by the surface chemistry of these phases during diagenetic reactions which vary with sediment accumulation rate. Processes which favour the enrichment of transition metals in equatorial Pacific nodules favour the depletion of 3 + REE in nodules and enrichment of 3 + REE in associated sediments. In contrast, Ce appears to be added both to nodules and sediments directly from seawater and is not involved in diagenetic reactions.

  19. Deep-water chemosynthetic ecosystem research during the census of marine life decade and beyond: a proposed deep-ocean road map.

    Directory of Open Access Journals (Sweden)

    Christopher R German

    Full Text Available The ChEss project of the Census of Marine Life (2002-2010 helped foster internationally-coordinated studies worldwide focusing on exploration for, and characterization of new deep-sea chemosynthetic ecosystem sites. This work has advanced our understanding of the nature and factors controlling the biogeography and biodiversity of these ecosystems in four geographic locations: the Atlantic Equatorial Belt (AEB, the New Zealand region, the Arctic and Antarctic and the SE Pacific off Chile. In the AEB, major discoveries include hydrothermal seeps on the Costa Rica margin, deepest vents found on the Mid-Cayman Rise and the hottest vents found on the Southern Mid-Atlantic Ridge. It was also shown that the major fracture zones on the MAR do not create barriers for the dispersal but may act as trans-Atlantic conduits for larvae. In New Zealand, investigations of a newly found large cold-seep area suggest that this region may be a new biogeographic province. In the Arctic, the newly discovered sites on the Mohns Ridge (71 °N showed extensive mats of sulfur-oxidisng bacteria, but only one gastropod potentially bears chemosynthetic symbionts, while cold seeps on the Haakon Mossby Mud Volcano (72 °N are dominated by siboglinid worms. In the Antarctic region, the first hydrothermal vents south of the Polar Front were located and biological results indicate that they may represent a new biogeographic province. The recent exploration of the South Pacific region has provided evidence for a sediment hosted hydrothermal source near a methane-rich cold-seep area. Based on our 8 years of investigations of deep-water chemosynthetic ecosystems worldwide, we suggest highest priorities for future research: (i continued exploration of the deep-ocean ridge-crest; (ii increased focus on anthropogenic impacts; (iii concerted effort to coordinate a major investigation of the deep South Pacific Ocean - the largest contiguous habitat for life within Earth's biosphere, but

  20. Deep-water chemosynthetic ecosystem research during the census of marine life decade and beyond: a proposed deep-ocean road map.

    Science.gov (United States)

    German, Christopher R; Ramirez-Llodra, Eva; Baker, Maria C; Tyler, Paul A

    2011-01-01

    The ChEss project of the Census of Marine Life (2002-2010) helped foster internationally-coordinated studies worldwide focusing on exploration for, and characterization of new deep-sea chemosynthetic ecosystem sites. This work has advanced our understanding of the nature and factors controlling the biogeography and biodiversity of these ecosystems in four geographic locations: the Atlantic Equatorial Belt (AEB), the New Zealand region, the Arctic and Antarctic and the SE Pacific off Chile. In the AEB, major discoveries include hydrothermal seeps on the Costa Rica margin, deepest vents found on the Mid-Cayman Rise and the hottest vents found on the Southern Mid-Atlantic Ridge. It was also shown that the major fracture zones on the MAR do not create barriers for the dispersal but may act as trans-Atlantic conduits for larvae. In New Zealand, investigations of a newly found large cold-seep area suggest that this region may be a new biogeographic province. In the Arctic, the newly discovered sites on the Mohns Ridge (71 °N) showed extensive mats of sulfur-oxidisng bacteria, but only one gastropod potentially bears chemosynthetic symbionts, while cold seeps on the Haakon Mossby Mud Volcano (72 °N) are dominated by siboglinid worms. In the Antarctic region, the first hydrothermal vents south of the Polar Front were located and biological results indicate that they may represent a new biogeographic province. The recent exploration of the South Pacific region has provided evidence for a sediment hosted hydrothermal source near a methane-rich cold-seep area. Based on our 8 years of investigations of deep-water chemosynthetic ecosystems worldwide, we suggest highest priorities for future research: (i) continued exploration of the deep-ocean ridge-crest; (ii) increased focus on anthropogenic impacts; (iii) concerted effort to coordinate a major investigation of the deep South Pacific Ocean - the largest contiguous habitat for life within Earth's biosphere, but also the

  1. Deep ocean communities impacted by changing climate over 24 y in the abyssal northeast Pacific Ocean.

    Science.gov (United States)

    Smith, Kenneth L; Ruhl, Henry A; Kahru, Mati; Huffard, Christine L; Sherman, Alana D

    2013-12-03

    The deep ocean, covering a vast expanse of the globe, relies almost exclusively on a food supply originating from primary production in surface waters. With well-documented warming of oceanic surface waters and conflicting reports of increasing and decreasing primary production trends, questions persist about how such changes impact deep ocean communities. A 24-y time-series study of sinking particulate organic carbon (food) supply and its utilization by the benthic community was conducted in the abyssal northeast Pacific (~4,000-m depth). Here we show that previous findings of food deficits are now punctuated by large episodic surpluses of particulate organic carbon reaching the sea floor, which meet utilization. Changing surface ocean conditions are translated to the deep ocean, where decadal peaks in supply, remineralization, and sequestration of organic carbon have broad implications for global carbon budget projections.

  2. Ocean disposal of heat generating radioactive waste

    International Nuclear Information System (INIS)

    1984-08-01

    The operational and technical feasibility of the penetrator option for HGW disposal has been reviewed and the areas where research is required to confirm feasibility have been identified. The research requirements have been presented against the Department's ocean disposal programme timescale on a series of bar charts. The bar charts show the need for theoretical and experimental studies of the basic mechanisms governing hole closure and the development of suitable instrumentation to assess the actual behaviour of the remoulded sediment in deep ocean trials. Detailed planning of deep ocean trials in sufficient time to develop strategy, models and instrumentation, identification of site investigation requirements and thermal response studies of sediments are also required. (author)

  3. Evidence for infragravity wave-tide resonance in deep oceans.

    Science.gov (United States)

    Sugioka, Hiroko; Fukao, Yoshio; Kanazawa, Toshihiko

    2010-10-05

    Ocean tides are the oscillatory motions of seawater forced by the gravitational attraction of the Moon and Sun with periods of a half to a day and wavelengths of the semi-Pacific to Pacific scale. Ocean infragravity (IG) waves are sea-surface gravity waves with periods of several minutes and wavelengths of several dozen kilometres. Here we report the first evidence of the resonance between these two ubiquitous phenomena, mutually very different in period and wavelength, in deep oceans. The evidence comes from long-term, large-scale observations with arrays of broadband ocean-bottom seismometers located at depths of more than 4,000 m in the Pacific Ocean. This observational evidence is substantiated by a theoretical argument that IG waves and the tide can resonantly couple and that such coupling occurs over unexpectedly wide areas of the Pacific Ocean. Through this resonant coupling, some of ocean tidal energy is transferred in deep oceans to IG wave energy.

  4. Geochemical behavior of beryllium isotopes in the ocean

    International Nuclear Information System (INIS)

    Kusakabe, M.; Ku, T.L.; Cusimano, G.L.; Southon, J.R.; Measures, C.I.

    1989-01-01

    9 Be and 10 Be have been measured in a variety of geological samples: sea water, marine particulate, bottom sediment and river water. While the 10 Be/ 9 Be ratio in the Pacific deep water seems to be constant, ∼ 1 x 10 -7 , the deep water in the Atlantic Ocean has significantly lower and variable ratio (0.7 x 10 -7 or less), reflecting larger input of riverine 9 Be to the Atlantic Ocean. The study of Be isotopes in river water, sea water, and sediment pore water from the southern California borderland shows that coastal areas play an important role in the removal of Be isotopes from the ocean. The behavior of particulate Be isotopes in the ocean is also discussed

  5. Decadal trends in deep ocean salinity and regional effects on steric sea level

    Science.gov (United States)

    Purkey, S. G.; Llovel, W.

    2017-12-01

    We present deep (below 2000 m) and abyssal (below 4000 m) global ocean salinity trends from the 1990s through the 2010s and assess the role of deep salinity in local and global sea level budgets. Deep salinity trends are assessed using all deep basins with available full-depth, high-quality hydrographic section data that have been occupied two or more times since the 1980s through either the World Ocean Circulation Experiment (WOCE) Hydrographic Program or the Global Ship-Based Hydrographic Investigations Program (GO-SHIP). All salinity data is calibrated to standard seawater and any intercruise offsets applied. While the global mean deep halosteric contribution to sea level rise is close to zero (-0.017 +/- 0.023 mm/yr below 4000 m), there is a large regional variability with the southern deep basins becoming fresher and northern deep basins becoming more saline. This meridional gradient in the deep salinity trend reflects different mechanisms driving the deep salinity variability. The deep Southern Ocean is freshening owing to a recent increased flux of freshwater to the deep ocean. Outside of the Southern Ocean, the deep salinity and temperature changes are tied to isopycnal heave associated with a falling of deep isopycnals in recent decades. Therefore, regions of the ocean with a deep salinity minimum are experiencing both a halosteric contraction with a thermosteric expansion. While the thermosteric expansion is larger in most cases, in some regions the halosteric compensates for as much as 50% of the deep thermal expansion, making a significant contribution to local sea level rise budgets.

  6. Sorption of americium and neptunium by deep-sea sediments

    International Nuclear Information System (INIS)

    Higgo, J.J.W.; Rees, L.V.C.; Cronan, D.S.

    1983-01-01

    The sorption and desorption of americium and neptunium by a wide range of deep-sea sediments from natural sea water at 4 0 C has been studied using a carefully controlled batch technique. All the sediments studied should form an excellent barrier to the migration of americium since distribution coefficients were uniformly greater than 10 5 and the sorption-desorption reaction may not be reversible. The sorption of neptunium was reversible and, except for one red clay, the distribution coefficients were greater than 10 3 for all the sediments investigated. Nevertheless the migration of neptunium should also be effectively retarded by most deep-sea sediments even under relatively oxidizing conditions. The neptunium in solution remained in the V oxidation state throughout the experiments. Under the experimental conditions used colloidal americium was trapped by the sediment and solubility did not seem to be the controlling factor in the desorption of americium. (Auth.)

  7. Total Sediment Thickness of the World's Oceans & Marginal Seas

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A digital total-sediment-thickness database for the world's oceans and marginal seas has been compiled by the NOAA National Geophysical Data Center (NGDC). The data...

  8. Culturable prokaryotic diversity of deep, gas hydrate sediments: first use of a continuous high-pressure, anaerobic, enrichment and isolation system for subseafloor sediments (DeepIsoBUG)

    OpenAIRE

    Parkes, R John; Sellek, Gerard; Webster, Gordon; Martin, Derek; Anders, Erik; Weightman, Andrew J; Sass, Henrik

    2009-01-01

    Deep subseafloor sediments may contain depressurization-sensitive, anaerobic, piezophilic prokaryotes. To test this we developed the DeepIsoBUG system, which when coupled with the HYACINTH pressure-retaining drilling and core storage system and the PRESS core cutting and processing system, enables deep sediments to be handled without depressurization (up to 25 MPa) and anaerobic prokaryotic enrichments and isolation to be conducted up to 100 MPa. Here, we describe the system and its first use...

  9. Summary of Results from Analyses of Deposits of the Deep-Ocean Impact of the Eltanin Asteroid

    Science.gov (United States)

    Kyte, Frank T.; Kuhn, Gerhard; Gersonde, Rainer

    2005-01-01

    Deposits of the late Pliocene (2.5 Ma) Eltanin impact are unique in the known geological record. The only known example of a km-sized asteroid to impact a deep-ocean (5 km) basin, is the most meterorite-rich locality known. This was discovered as an Ir anomaly in sediments from three cores collected in 1965 by the USNS Eltanin. These cores contained mm-sized shock-melted asteroid materials and unmelted meteorite fragments. Mineral chemistry of meteorite fragments, and siderophole concentrations in melt rocks, indicate that the parent asteroid was a low-metal (4\\%) mesosiderite. A geological exploration of the impact in 1995 by Polarstern expedition ANT-XIV4 was near the Freeden Seamounts (57.3S, 90.5 W), and successfully collected three cores with impact deposits. Analyses showed that sediments as old as Eocene were eroded by the impact disturbance and redeposited in three distinct units. The lowermost is a chaotic assemblage of sediment fragments up to 50 cm in size. Above this is a laminated sand-rich unit that deposited as a turbulent flow, and this is overlain by a more fine-grained deposit of silts and clays that settled from a cloud of sediment suspended in the water column. Meteoritic ejecta particles were concentrated near the base of the uppermost unit, where coarse ejecta caught up with the disturbed sediment. Here we will present results from a new suite of cores collected on Polarstern expedition ANT-XVIIU5a. In 2001, the Polarstern returned to the impact area and explored a region of 80,000 sq-km., collecting at least 16 sediment cores with meteoritic ejecta. The known strewn field extends over a region 660 by 200 km. The meteoritic ejecta is most concentrated in cores on the Freeden seamounts, and in the basins to the north, where the amount of meteoritic material deposited on the ocean floor was as much as 3 g/sq-cm. These concentrations drop off to the north and the east to levels as low as approximately 0.1 g/sq-cm. We were unable to sample the

  10. Deep-sea mud in the Pacific Ocean as a potential resource for rare-earth elements

    Science.gov (United States)

    Kato, Yasuhiro; Fujinaga, Koichiro; Nakamura, Kentaro; Takaya, Yutaro; Kitamura, Kenichi; Ohta, Junichiro; Toda, Ryuichi; Nakashima, Takuya; Iwamori, Hikaru

    2011-08-01

    World demand for rare-earth elements and the metal yttrium--which are crucial for novel electronic equipment and green-energy technologies--is increasing rapidly. Several types of seafloor sediment harbour high concentrations of these elements. However, seafloor sediments have not been regarded as a rare-earth element and yttrium resource, because data on the spatial distribution of these deposits are insufficient. Here, we report measurements of the elemental composition of over 2,000 seafloor sediments, sampled at depth intervals of around one metre, at 78 sites that cover a large part of the Pacific Ocean. We show that deep-sea mud contains high concentrations of rare-earth elements and yttrium at numerous sites throughout the eastern South and central North Pacific. We estimate that an area of just one square kilometre, surrounding one of the sampling sites, could provide one-fifth of the current annual world consumption of these elements. Uptake of rare-earth elements and yttrium by mineral phases such as hydrothermal iron-oxyhydroxides and phillipsite seems to be responsible for their high concentration. We show that rare-earth elements and yttrium are readily recovered from the mud by simple acid leaching, and suggest that deep-sea mud constitutes a highly promising huge resource for these elements.

  11. Application of deep convolutional neural networks for ocean front recognition

    Science.gov (United States)

    Lima, Estanislau; Sun, Xin; Yang, Yuting; Dong, Junyu

    2017-10-01

    Ocean fronts have been a subject of study for many years, a variety of methods and algorithms have been proposed to address the problem of ocean fronts. However, all these existing ocean front recognition methods are built upon human expertise in defining the front based on subjective thresholds of relevant physical variables. This paper proposes a deep learning approach for ocean front recognition that is able to automatically recognize the front. We first investigated four existing deep architectures, i.e., AlexNet, CaffeNet, GoogLeNet, and VGGNet, for the ocean front recognition task using remote sensing (RS) data. We then propose a deep network with fewer layers compared to existing architecture for the front recognition task. This network has a total of five learnable layers. In addition, we extended the proposed network to recognize and classify the front into strong and weak ones. We evaluated and analyzed the proposed network with two strategies of exploiting the deep model: full-training and fine-tuning. Experiments are conducted on three different RS image datasets, which have different properties. Experimental results show that our model can produce accurate recognition results.

  12. Ion migration in ocean sediments: subseafloor radioactive waste disposal

    International Nuclear Information System (INIS)

    Nuttall, H.E.; Ray, A.K.; Davis, E.J.

    1980-01-01

    In this study of seabed disposal, analytical ion transport models were developed and used to elucidate ion migration through ocean sediments and to study the escape of ions from the ocean floor into the water column. An unsteady state isothermal diffusion model was developed for the region far from the canister to examine the effects of ion diffusion, adsorption, radioactive decay, sediment thickness and canister position. Analytical solutions were derived to represent the transient concentration profiles within the sediment, ion flux and the ion discharge rate to the water column for two types of initial conditions: instantaneous dissolution of the canister and constant canister leakage. Generalized graphs showing ion migration and behavior are presented

  13. Pathways of upwelling deep waters to the surface of the Southern Ocean

    Science.gov (United States)

    Tamsitt, Veronica; Drake, Henri; Morrison, Adele; Talley, Lynne; Dufour, Carolina; Gray, Alison; Griffies, Stephen; Mazloff, Matthew; Sarmiento, Jorge; Wang, Jinbo; Weijer, Wilbert

    2017-04-01

    Upwelling of Atlantic, Indian and Pacific deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of anthropogenic carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. Here we go beyond the two-dimensional view of Southern Ocean upwelling, to show detailed Southern Ocean upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution ocean and climate models. The northern deep waters enter the Antarctic Circumpolar Current (ACC) via narrow southward currents along the boundaries of the three ocean basins, before spiraling southeastward and upward through the ACC. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the southern ACC boundary, with a spatially nonuniform distribution, regionalizing warm water supply to Antarctic ice shelves and the delivery of nutrient and carbon-rich water to the sea surface. The timescale for half of the deep water to upwell from 30°S to the mixed layer is on the order of 60-90 years, which has important implications for the timescale for signals to propagate through the deep ocean. In addition, we quantify the diabatic transformation along particle trajectories, to identify where diabatic processes are important along the upwelling pathways.

  14. Ca Isotope Geochemistry in Marine Deep Sea Sediments of the Eastern Pacific

    Science.gov (United States)

    Wittke, A.; Gussone, N. C.; Derigs, D.; Schälling, M.; Teichert, B. M.

    2017-12-01

    Ca isotope ratio analysis (δ44/40Ca) is a powerful tool to investigate diagenetic reactions in marine sedimentary porewater systems, as it is sensitive to processes such as carbonate dissolution, precipitation, recrystallization, ion exchange and deep fluid sources, due to the isotopic difference between dissolved Ca and solid carbonate minerals (e.g. [1];[2]). We analyzed eight sediment cores of the (paleo-) Pacific equatorial age transect. Two sediment cores show decreasing Ca isotope profiles starting at the sediment/water interface with seawater-like values down to sediment-like values due to recrystallization and an increasing in the bottom part again to seawater-like values. The other studied cores show different degrees of flattening of this middle bulge. We interpret this pattern either as an effect of sediment composition and thickness, decreasing recrystallization rates and/or fluid flux or a combination of all of these factors at the respective sampling sites. Element concentration profiles and Sr-isotope variations on some of these sediment cores show a similar behavior, supporting our findings ([3]; [4]). Seawater influx at (inactive) seamounts is supposed to cause seawater-like values at the bottom of the sediment cores by fluids migrating through the oceanic basement (e.g. [5]). While [6] hypothesizes that two seamounts or bathymetric pits are connected, with a recharge and a discharge site [7] say that uptaken fluids could be released through the surrounding seafloor as well due to diffusive exchange with the underlying oceanic crust. Our Ca isotope results combined with a transport reaction model approach support the latter hypothesis. References: [1] Teichert B. M., Gussone N. and Torres M. E. (2009) [2] Ockert C., Gussone N., Kaufhold S. and Teichert B. (2013) [3] Pälike H., Lyle M., Nishi H., Raffi I., Gamage K. and Klaus A. (eds.) (2010) [4] Voigt J., Hathorne E. C., Frank M., Vollstaedt H. and Eisenhauer A. (2015) [5] Villinger H. W

  15. Hydrothermal Fe cycling and deep ocean organic carbon scavenging: Model-based evidence for significant POC supply to seafloor sediments

    Digital Repository Service at National Institute of Oceanography (India)

    German, C.R.; Legendre, L.L.; Sander, S.G.;; Niquil, N.; Luther-III, G.W.; LokaBharathi, P.A.; Han, X.; LeBris, N.

    by more than ~10% over background values, what the model does indicate is that scavenging of carbon in association with Fe-rich hydrothermal plume particles should play a significant role in the delivery of particulate organic carbon to deep ocean...

  16. Atmospheric and Oceanic Response to Southern Ocean Deep Convection Oscillations on Decadal to Centennial Time Scales in Climate Models

    Science.gov (United States)

    Martin, T.; Reintges, A.; Park, W.; Latif, M.

    2014-12-01

    Many current coupled global climate models simulate open ocean deep convection in the Southern Ocean as a recurring event with time scales ranging from a few years to centennial (de Lavergne et al., 2014, Nat. Clim. Ch.). The only observation of such event, however, was the occurrence of the Weddell Polynya in the mid-1970s, an open water area of 350 000 km2 within the Antarctic sea ice in three consecutive winters. Both the wide range of modeled frequency of occurrence and the absence of deep convection in the Weddell Sea highlights the lack of understanding concerning the phenomenon. Nevertheless, simulations indicate that atmospheric and oceanic responses to the cessation of deep convection in the Southern Ocean include a strengthening of the low-level atmospheric circulation over the Southern Ocean (increasing SAM index) and a reduction in the export of Antarctic Bottom Water (AABW), potentially masking the regional effects of global warming (Latif et al., 2013, J. Clim.; Martin et al., 2014, Deep Sea Res. II). It is thus of great importance to enhance our understanding of Southern Ocean deep convection and clarify the associated time scales. In two multi-millennial simulations with the Kiel Climate Model (KCM, ECHAM5 T31 atmosphere & NEMO-LIM2 ~2˚ ocean) we showed that the deep convection is driven by strong oceanic warming at mid-depth periodically overriding the stabilizing effects of precipitation and ice melt (Martin et al., 2013, Clim. Dyn.). Sea ice thickness also affects location and duration of the deep convection. A new control simulation, in which, amongst others, the atmosphere grid resolution is changed to T42 (~2.8˚), yields a faster deep convection flip-flop with a period of 80-100 years and a weaker but still significant global climate response similar to CMIP5 simulations. While model physics seem to affect the time scale and intensity of the phenomenon, the driving mechanism is a rather robust feature. Finally, we compare the atmospheric and

  17. Phosphate solubilizing bacteria: Comparison between coastal and deep sea sediments

    Digital Repository Service at National Institute of Oceanography (India)

    Biche, S.; Pandey, S.; Gonsalves, M.J.B.D.; Das, A.; Mascarenhas-Pereira, M.B.L.; LokaBharathi, P.A.

    in the CIB sediments (r=0.59) than in the coastal sediments (r= 0.22). It is apparent that the enzyme activity in the coastal sediments could be more for P mobilization and in the oligotrophic deep sea it could be both for P and C mobilization....

  18. Ship track for Life on the Edge 2003: Exploring Deep Ocean Habitats - Office of Ocean Exploration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Ship track of the R/V Seward Johnson during the "Life on the Edge 2003: Exploring Deep Ocean Habitats" expedition sponsored by the National Oceanic and Atmospheric...

  19. Microbially-mediated fluorescent organic matter transformations in the deep ocean

    DEFF Research Database (Denmark)

    Aparicio, Fran L.; Nieto-Cid, Mar; Borrull, Encarna

    2015-01-01

    The refractory nature of marine dissolved organic matter (DOM) increases while it travels from surface waters to the deep ocean. This resistant fraction is in part composed of fluorescent humic-like material, which is relatively difficult to metabolize by deep water prokaryotes, and it can also b....... These findings contribute to the understanding of FDOM variability in deep waters and provide valuable information for studies where fluorescent compounds are used in order to track water masses and/or microbial processes.......The refractory nature of marine dissolved organic matter (DOM) increases while it travels from surface waters to the deep ocean. This resistant fraction is in part composed of fluorescent humic-like material, which is relatively difficult to metabolize by deep water prokaryotes, and it can also...

  20. Feasibility of disposal of high-level radioactive waste into the seabed. volume 7: Review of laboratory investigations of radionuclide migration through deep-sea sediments

    International Nuclear Information System (INIS)

    Brush, L.H.

    1988-01-01

    One of the options suggested for disposal of high-level radioactive waste resulting from the generation of nuclear power is burial beneath the deep ocean floor in geologically stable sediment formations which have no economic value. The 8-volume series provides an assessment of the technical feasibility and radiological safety of this disposal concept based on the results obtained by ten years of co-operation and information exchange among the Member countries participating in the NEA Seabed Working Group. This volume contains a review of the laboratory investigations of radionuclide migration through deep-sea sediments. In addition, it discusses the data selected for the radiological assessment, on the basis of both field and laboratory studies

  1. Oceanic ferromanganese deposits: Future resources and past-ocean recorders

    Digital Repository Service at National Institute of Oceanography (India)

    Banakar, V.K.; Nair, R.R.; Parthiban, G.; Pattan, J.N.

    decades following the Mero's publication witnessed global "Nodule Rush". The technological leaders of those years like US, Germany, Japan, France, New-Zealand, and USSR have conducted major scientific expeditions to the Central Pacific to map...-Mn-(Cu+Ni+Co) in ferromanganese deposits from the Central Indian Ocean (Source: Jauhari, 1987). OCEANIC FERROMANGANESE DEPOSITS 45 DISTRIBUTION The nodules occur invariably in almost all the deep-sea basins witnessing low sedimentation rates. But abundant ore grade deposits...

  2. Deep-Ocean Assessment and Reporting of Tsunamis (DART(R))

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — As part of the U.S. National Tsunami Hazard Mitigation Program (NTHMP), the Deep Ocean Assessment and Reporting of Tsunamis (DART(R)) Project is an ongoing effort to...

  3. Methods in mooring deep sea sediment traps

    Digital Repository Service at National Institute of Oceanography (India)

    Venkatesan, R.; Fernando, V.; Rajaraman, V.S.; Janakiraman, G.

    The experience gained during the process of deployment and retrieval of nearly 39 sets of deep sea sediment trap moorings on various ships like FS Sonne, ORV Sagarkanya and DSV Nand Rachit are outlined. The various problems encountered...

  4. Habitat filtering of bacterioplankton communities above polymetallic nodule fields and sediments in the Clarion-Clipperton zone of the Pacific Ocean.

    Science.gov (United States)

    Lindh, Markus V; Maillot, Brianne M; Smith, Craig R; Church, Matthew J

    2018-04-01

    Deep-sea mining of commercially valuable polymetallic nodule fields will generate a seabed sediment plume into the water column. Yet, the response of bacterioplankton communities, critical in regulating energy and matter fluxes in marine ecosystems, to such disturbances is unknown. Metacommunity theory, traditionally used in general ecology for macroorganisms, offers mechanistic understanding on the relative role of spatial differences compared with local environmental conditions (habitat filtering) for community assembly. We examined bacterioplankton metacommunities using 16S rRNA amplicons from the Clarion-Clipperton Zone (CCZ) in the eastern Pacific Ocean and in global ocean transect samples to determine sensitivity of these assemblages to environmental perturbations. Habitat filtering was the main assembly mechanism of bacterioplankton community composition in the epi- and mesopelagic waters of the CCZ and the Tara Oceans transect. Bathy- and abyssopelagic bacterioplankton assemblages were mainly assembled by undetermined metacommunity types or neutral and dispersal-driven patch-dynamics for the CCZ and the Malaspina transect. Environmental disturbances may alter the structure of upper-ocean microbial assemblages, with potentially even more substantial, yet unknown, impact on deep-sea communities. Predicting such responses in bacterioplankton assemblage dynamics can improve our understanding of microbially-mediated regulation of ecosystem services in the abyssal seabed likely to be exploited by future deep-sea mining operations. © 2018 Society for Applied Microbiology and John Wiley & Sons Ltd.

  5. Measurement of penetration depths of plutonium and americium in sediment from the ocean floor

    International Nuclear Information System (INIS)

    Fried, S.; Friedman, A.; Hines, J.; Sjoblom, R.; Schmitz, G.; Schreiner, F.

    1979-01-01

    The clay-like sediment covering the ocean floor constitutes the last barrier that shields the biosphere from contamination by radionuclides stemming from the nuclear wastes of a subseabed repository. In the event of a failure of the engineered barriers the mobility of the released radionuclides in the sediment determines the rate and the extent of entry into the water of the ocean. The initial results of measurements designed to determine the mobility of transuranium elements in sediment from the ocean floor are presented. Data indicate very low migration rates and imply strong chemisorptive interaction with the sediment

  6. Composition, oxygen isotope geochemistry, and origin of smectite in the metalliferous sediments of the Bauer Deep, southeast Pacific

    Energy Technology Data Exchange (ETDEWEB)

    Cole, T G [Imperial Coll. of Science and Technology, London (UK). Geology Dept.

    1985-01-01

    The sediments of the Bauer Deep, an open ocean basin situated on the northwest Nazca Plate in the southeast Pacific, constitute a regional metalliferous deposit dominated by authigenic smectite. Two 2-metre long cores from the Bauer Deep were examined to investigate the nature and origin of the smectite. Infra-red and Mossbauer spectroscopy, and wet chemical analysis (LiBO/sub 2/ fusion) of isolated smectite, indicate the mineral is a Mg-rich, Al-rich nontronite. Oxygen isotopic compositions for isolated smectite are uniform and translate to a non-hydrothermal temperature of formation of about 3 deg C. SEM observations show an abundance of well-preserved biogenic opal in surface and near surface sediment but postburial dissolution and transformation of this phase to smectite is evident at depth. Smectite formation is the result of interaction between iron oxyhydroxide, ponded in the Bauer Deep following a hydrothermal origin at the adjacent East Pacific Rise, and biogenic opal. A reaction mechanism is proposed. Regional factors control smectite formation. In particular, formation is inhibited in areas of CaCO/sub 3/ accumulation (topographic elevations) but favoured in areas of oxyhydroxide and opal ponding (topographic depressions.)

  7. Composition, oxygen isotope geochemistry, and origin of smectite in the metalliferous sediments of the Bauer Deep, southeast Pacific

    International Nuclear Information System (INIS)

    Cole, T.G.

    1985-01-01

    The sediments of the Bauer Deep, an open ocean basin situated on the northwest Nazca Plate in the southeast Pacific, constitute a regional metalliferous deposit dominated by authigenic smectite. Two 2-metre long cores from the Bauer Deep were examined to investigate the nature and origin of the smectite. Infra-red and Mossbauer spectroscopy, and wet chemical analysis (LiBO 2 fusion) of isolated smectite, indicate the mineral is a Mg-rich, Al-rich nontronite. Oxygen isotopic compositions for isolated smectite are uniform and translate to a non-hydrothermal temperature of formation of about 3 deg C. SEM observations show an abundance of well-preserved biogenic opal in surface and near surface sediment but postburial dissolution and transformation of this phase to smectite is evident at depth. Smectite formation is the result of interaction between iron oxyhydroxide, ponded in the Bauer Deep following a hydrothermal origin at the adjacent East Pacific Rise, and biogenic opal. A reaction mechanism is proposed. Regional factors control smectite formation. In particular, formation is inhibited in areas of CaCO 3 accumulation (topographic elevations) but favoured in areas of oxyhydroxide and opal ponding (topographic depressions.) (author)

  8. Near-inertial waves and deep ocean mixing

    Science.gov (United States)

    Shrira, V. I.; Townsend, W. A.

    2013-07-01

    For the existing pattern of global oceanic circulation to exist, there should be sufficiently strong turbulent mixing in the abyssal ocean, the mechanisms of which are not well understood as yet. The review discusses a plausible mechanism of deep ocean mixing caused by near-inertial waves in the abyssal ocean. It is well known how winds in the atmosphere generate near-inertial waves in the upper ocean, which then propagate downwards losing their energy in the process; only a fraction of the energy at the surface reaches the abyssal ocean. An open question is whether and, if yes, how these weakened inertial motions could cause mixing in the deep. We review the progress in the mathematical description of a mechanism that results in an intense breaking of near-inertial waves near the bottom of the ocean and thus enhances the mixing. We give an overview of the present state of understanding of the problem covering both the published and the unpublished results; we also outline the key open questions. For typical ocean stratification, the account of the horizontal component of the Earth's rotation leads to the existence of near-bottom wide waveguides for near-inertial waves. Due to the β-effect these waveguides are narrowing in the poleward direction. Near-inertial waves propagating poleward get trapped in the waveguides; we describe how in the process these waves are focusing more and more in the vertical direction, while simultaneously their group velocity tends to zero and wave-induced vertical shear significantly increases. This causes the development of shear instability, which is interpreted as wave breaking. Remarkably, this mechanism of local intensification of turbulent mixing in the abyssal ocean can be adequately described within the framework of linear theory. The qualitative picture is similar to wind wave breaking on a beach: the abyssal ocean always acts as a surf zone for near-inertial waves.

  9. Near-inertial waves and deep ocean mixing

    International Nuclear Information System (INIS)

    Shrira, V I; Townsend, W A

    2013-01-01

    For the existing pattern of global oceanic circulation to exist, there should be sufficiently strong turbulent mixing in the abyssal ocean, the mechanisms of which are not well understood as yet. The review discusses a plausible mechanism of deep ocean mixing caused by near-inertial waves in the abyssal ocean. It is well known how winds in the atmosphere generate near-inertial waves in the upper ocean, which then propagate downwards losing their energy in the process; only a fraction of the energy at the surface reaches the abyssal ocean. An open question is whether and, if yes, how these weakened inertial motions could cause mixing in the deep. We review the progress in the mathematical description of a mechanism that results in an intense breaking of near-inertial waves near the bottom of the ocean and thus enhances the mixing. We give an overview of the present state of understanding of the problem covering both the published and the unpublished results; we also outline the key open questions. For typical ocean stratification, the account of the horizontal component of the Earth's rotation leads to the existence of near-bottom wide waveguides for near-inertial waves. Due to the β-effect these waveguides are narrowing in the poleward direction. Near-inertial waves propagating poleward get trapped in the waveguides; we describe how in the process these waves are focusing more and more in the vertical direction, while simultaneously their group velocity tends to zero and wave-induced vertical shear significantly increases. This causes the development of shear instability, which is interpreted as wave breaking. Remarkably, this mechanism of local intensification of turbulent mixing in the abyssal ocean can be adequately described within the framework of linear theory. The qualitative picture is similar to wind wave breaking on a beach: the abyssal ocean always acts as a surf zone for near-inertial waves. (paper)

  10. Spiraling pathways of global deep waters to the surface of the Southern Ocean.

    Science.gov (United States)

    Tamsitt, Veronica; Drake, Henri F; Morrison, Adele K; Talley, Lynne D; Dufour, Carolina O; Gray, Alison R; Griffies, Stephen M; Mazloff, Matthew R; Sarmiento, Jorge L; Wang, Jinbo; Weijer, Wilbert

    2017-08-02

    Upwelling of global deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. However, the exact pathways and role of topography in Southern Ocean upwelling remain largely unknown. Here we show detailed upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution models. The analysis reveals that the northern-sourced deep waters enter the Antarctic Circumpolar Current via southward flow along the boundaries of the three ocean basins, before spiraling southeastward and upward through the Antarctic Circumpolar Current. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the Antarctic Circumpolar Current, with a spatially nonuniform distribution. The timescale for half of the deep water to upwell from 30° S to the mixed layer is ~60-90 years.Deep waters of the Atlantic, Pacific and Indian Oceans upwell in the Southern Oceanbut the exact pathways are not fully characterized. Here the authors present a three dimensional view showing a spiralling southward path, with enhanced upwelling by eddy-transport at topographic hotspots.

  11. Deep oceans may acidify faster than anticipated due to global warming

    Science.gov (United States)

    Chen, Chen-Tung Arthur; Lui, Hon-Kit; Hsieh, Chia-Han; Yanagi, Tetsuo; Kosugi, Naohiro; Ishii, Masao; Gong, Gwo-Ching

    2017-12-01

    Oceans worldwide are undergoing acidification due to the penetration of anthropogenic CO2 from the atmosphere1-4. The rate of acidification generally diminishes with increasing depth. Yet, slowing down of the thermohaline circulation due to global warming could reduce the pH in the deep oceans, as more organic material would decompose with a longer residence time. To elucidate this process, a time-series study at a climatically sensitive region with sufficient duration and resolution is needed. Here we show that deep waters in the Sea of Japan are undergoing reduced ventilation, reducing the pH of seawater. As a result, the acidification rate near the bottom of the Sea of Japan is 27% higher than the rate at the surface, which is the same as that predicted assuming an air-sea CO2 equilibrium. This reduced ventilation may be due to global warming and, as an oceanic microcosm with its own deep- and bottom-water formations, the Sea of Japan provides an insight into how future warming might alter the deep-ocean acidification.

  12. A Stratification Boomerang: Nonlinear Dependence of Deep Southern Ocean Ventilation on PCO2

    Science.gov (United States)

    Galbraith, E. D.; Merlis, T. M.

    2014-12-01

    Strong correlations between atmospheric CO2, Antarctic temperatures, and marine proxy records have hinted that ventilation of the deep Southern Ocean may have played a central role in the variations of CO2 over glacial-interglacial cycles. One proposition is that, in general, the Southern Ocean ventilates the deep more strongly under higher CO2, due to a change in winds and/or the dominance of thermal stratification in a warm ocean, which weakens ocean biological carbon storage. Here, we explore this idea with a suite of multi-millennial simulations using the GFDL CM2Mc global coupled model. The results are, indeed, consistent with increasing ventilation of the Southern Ocean as pCO2 increases above modern. However, they reveal a surprising twist under low pCO2: increased salinity of the Southern Ocean, due in part to weakening atmospheric moisture transport, actually increases ventilation rate of the deep ocean under low pCO2 as well. This implies that a nadir of Southern Ocean ventilation occurs at intermediate pCO2, which the model estimates as being close to that of the present-day. This is at odds with the interpretation that weak ventilation of the deep Southern Ocean was the unifying coupled mechanism for the glacial pCO2 cycles. Rather, it suggests that factors other than the ventilation rate of the deep Southern Ocean, such as iron fertilization, ecosystem changes, water mass distributions, and sea ice cover, were key players in the glacial-interglacial CO2 changes.

  13. Tropical teleconnections via the ocean and atmosphere induced by Southern Ocean deep convective events

    Science.gov (United States)

    Marinov, I.; Cabre, A.; Gunn, A.; Gnanadesikan, A.

    2016-12-01

    The current generation (CMIP5) of Earth System Models (ESMs) shows a huge variability in their ability to represent Southern Ocean (SO) deep-ocean convection and Antarctic Bottom Water, with a preference for open-sea convection in the Weddell and Ross gyres. A long control simulation in a coarse 3o resolution ESM (the GFDL CM2Mc model) shows a highly regular multi-decadal oscillation between periods of SO open sea convection and non-convective periods. This process also happens naturally, with different frequencies and durations of convection across most CMIP5 models under preindustrial forcing (deLavergne et al, 2014). Here we assess the impact of SO deep convection and resulting sea surface temperature (SST) anomalies on the tropical atmosphere and ocean via teleconnections, with a focus on interannual to multi-decadal timescales. We combine analysis of our low-resolution coupled model with inter-model analysis across historical CMIP5 simulations. SST cooling south of 60S during non-convective decades triggers a stronger, northward shifted SH Hadley cell, which results in intensified northward cross-equatorial moist heat transport and a poleward shift in the ITCZ. Resulting correlations between the cross-equatorial atmospheric heat transport and ITCZ location are in good agreement with recent theories (e.g. Frierson et al. 2013; Donohoe et al. 2014). Lagged correlations between a SO convective index and cross-equatorial heat transports (in the atmosphere and ocean), as well as various tropical (and ENSO) climate indices are analyzed. In the ocean realm, we find that non-convective decades result in weaker AABW formation and weaker ACC but stronger Antarctic Intermediate Water (AAIW) formation, likely as a result of stronger SO westerlies (more positive SAM). The signals of AABW and AAIW are seen in the tropics on short timescales of years to decades in the temperature, heat storage and heat transport anomalies and also in deep and intermediate ocean oxygen. Most

  14. Magnetic Hysteresis of Deep-Sea Sediments in Korea Deep Ocean Study(KODOS) Area, NE Pacific

    Science.gov (United States)

    Kim, K.; Park, C.; Yoo, C.

    2001-12-01

    The KODOS area within the Clarion-Clipperton fracture zone (C-C zone) is surrounded by the Hawaiian and Line Island Ridges to the west and the central American continent to the east. Topography of the seafloor consists of flat-topped abyssal hills and adjacent abyssal troughs, both of which run parallel in N-S direction. Sediments from the study area consist mainly of biogenic sediments. Latitudinal zonation of sedimentary facies was caused by the accumulation of biogenic materials associated with the equatorial current system and movement of the Pacific plate toward the north or northwest. The KODOS area belongs to the latitudinal transition zone having depositional characteristics between non-fossiliferous pelagic clay-dominated zone and calcareous sediment-dominated zone. The box core sediments of the KODOS area are analyzed in an attempt to obtain magnetic hysteresis information and to elucidate the relationship between hysteresis property and lithological facies. Variations in magnetic hysteresis parameters with unit layers reflect the magnetic grain-size and concentrations within the sediments. The ratios of remanant coercivity/coercive force (Hcr/Hc) and saturation remnance/saturation magnetization (Mrs/Ms) indicate that coarse magnetic grains are mainly distributed in dark brown sediments (lower part of the sediment core samples) reflecting high Hcr/Hc and low Mrs/Ms ratios. These results are mainly caused by dissolution differences with core depth. From the plotting of the ratios of hyteresis parameters, it is indicated that magnetic minerals in cubic samples are in pseudo-single domain (PSD) state.

  15. Distribution of artificial radionuclides in deep sediments of the Mediterranean Sea

    International Nuclear Information System (INIS)

    Garcia-Orellana, J.; Pates, J.M.; Masque, P.; Bruach, J.M.; Sanchez-Cabeza, J.A.

    2009-01-01

    Artificial radionuclides enter the Mediterranean Sea mainly through atmospheric deposition following nuclear weapons tests and the Chernobyl accident, but also through the river discharge of nuclear facility effluents. Previous studies of artificial radionuclides impact of the Mediterranean Sea have focussed on shallow, coastal sediments. However, deep sea sediments have the potential to store and accumulate pollutants, including artificial radionuclides. Deep sea marine sediment cores were collected from Mediterranean Sea abyssal plains (depth > 2000 m) and analysed for 239,240 Pu and 137 Cs to elucidate the concentrations, inventories and sources of these radionuclides in the deepest areas of the Mediterranean. The activity - depth profiles of 210 Pb, together with 14 C dating, indicate that sediment mixing redistributes the artificial radionuclides within the first 2.5 cm of the sedimentary column. The excess 210 Pb inventory was used to normalize 239,240 Pu and 137 Cs inventories for variable sediment fluxes. The 239,240 Pu/ 210 Pb xs ratio was uniform across the entire sea, with a mean value of 1.24 x 10 -3 , indicating homogeneous fallout of 239,240 Pu. The 137 Cs/ 210 Pb xs ratio showed differences between the eastern (0.049) and western basins (0.030), clearly significant impact of deep sea sediments from the Chernobyl accident. The inventory ratios of 239,240 Pu/ 137 Cs were 0.041 and 0.025 in the western and eastern basins respectively, greater than the fallout ratio, 0.021, showing more efficient scavenging of 239,240 Pu in the water column and major sedimentation of 137 Cs in the eastern basin. Although areas with water depths of > 2000 m constitute around 40% of the entire Mediterranean basin, the sediments in these regions only contained 2.7% of the 239,240 Pu and 0.95% of the 137 Cs deposited across the Sea in 2000. These data show that the accumulation of artificial radionuclides in deep Mediterranean environments is much lower than predicted by

  16. Ejecta from Ocean Impacts

    Science.gov (United States)

    Kyte, Frank T.

    2003-01-01

    Numerical simulations of deep-ocean impact provide some limits on the size of a projectile that will not mix with the ocean floor during a deep-ocean impact. For a vertical impact at asteroidal velocities (approx. 20 km/s), mixing is only likely when the projectile diameter is greater than 112 of the water depth. For oblique impacts, even larger projectiles will not mix with ocean floor silicates. Given the typical water depths of 4 to 5 km in deep-ocean basins, asteroidal projectiles with diameters as large as 2 or 3 km may commonly produce silicate ejecta that is composed only of meteoritic materials and seawater salts. However, the compressed water column beneath the projectile can still disrupt and shock metamorphose the ocean floor. Therefore, production of a separate, terrestrial ejecta component is not ruled out in the most extreme case. With increasing projectile size (or energy) relative to water depths, there must be a gradation between oceanic impacts and more conventional continental impacts. Given that 60% of the Earth's surface is covered by oceanic lithosphere and 500 m projectiles impact the Earth on 10(exp 5) y timescales, there must be hundreds of oceanic impact deposits in the sediment record awaiting discovery.

  17. Total Sediment Thickness of the World's Oceans & Marginal Seas, Version 2

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NGDC's global ocean sediment thickness grid (Divins, 2003) has been updated for the Australian-Antarctic region (60?? -155?? E, 30?? -70?? S). New seismic reflection...

  18. Exploring fungal diversity in deep-sea sediments from Okinawa Trough using high-throughput Illumina sequencing

    Science.gov (United States)

    Zhang, Xiao-Yong; Wang, Guang-Hua; Xu, Xin-Ya; Nong, Xu-Hua; Wang, Jie; Amin, Muhammad; Qi, Shu-Hua

    2016-10-01

    The present study investigated the fungal diversity in four different deep-sea sediments from Okinawa Trough using high-throughput Illumina sequencing of the nuclear ribosomal internal transcribed spacer-1 (ITS1). A total of 40,297 fungal ITS1 sequences clustered into 420 operational taxonomic units (OTUs) with 97% sequence similarity and 170 taxa were recovered from these sediments. Most ITS1 sequences (78%) belonged to the phylum Ascomycota, followed by Basidiomycota (17.3%), Zygomycota (1.5%) and Chytridiomycota (0.8%), and a small proportion (2.4%) belonged to unassigned fungal phyla. Compared with previous studies on fungal diversity of sediments from deep-sea environments by culture-dependent approach and clone library analysis, the present result suggested that Illumina sequencing had been dramatically accelerating the discovery of fungal community of deep-sea sediments. Furthermore, our results revealed that Sordariomycetes was the most diverse and abundant fungal class in this study, challenging the traditional view that the diversity of Sordariomycetes phylotypes was low in the deep-sea environments. In addition, more than 12 taxa accounted for 21.5% sequences were found to be rarely reported as deep-sea fungi, suggesting the deep-sea sediments from Okinawa Trough harbored a plethora of different fungal communities compared with other deep-sea environments. To our knowledge, this study is the first exploration of the fungal diversity in deep-sea sediments from Okinawa Trough using high-throughput Illumina sequencing.

  19. 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 ...... volume-specific carbon degradation rates were 0.3–1.5 µmol cm−3 d−1; bioturbation coefficient near the sediment surface was 3–8 cm2 yr−1. These results indicate that carbon cycling in large freshwater systems conforms to many of the same trends as in marine systems.......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...

  20. Organophosphate Ester Flame Retardants and Plasticizers in Ocean Sediments from the North Pacific to the Arctic Ocean.

    Science.gov (United States)

    Ma, Yuxin; Xie, Zhiyong; Lohmann, Rainer; Mi, Wenying; Gao, Guoping

    2017-04-04

    The presence of organophosphate ester (OPE) flame retardants and plasticizers in surface sediment from the North Pacific to Arctic Ocean was observed for the first time during the fourth National Arctic Research Expedition of China in the summer of 2010. The samples were analyzed for three halogenated OPEs [tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), and tris(dichloroisopropyl) phosphate], three alkylated OPEs [triisobutyl phosphate (TiBP), tri-n-butyl phosphate, and tripentyl phosphate], and triphenyl phosphate. Σ 7 OPEs (total concentration of the observed OPEs) was in the range of 159-4658 pg/g of dry weight. Halogenated OPEs were generally more abundant than the nonhalogenated OPEs; TCEP and TiBP dominated the overall concentrations. Except for that of the Bering Sea, Σ 7 OPEs values increased with increasing latitudes from Bering Strait to the Central Arctic Ocean, while the contributions of halogenated OPEs (typically TCEP and TCPP) to the total OPE profile also increased from the Bering Strait to the Central Arctic Ocean, indicating they are more likely to be transported to the remote Arctic. The median budget of 52 (range of 17-292) tons for Σ 7 OPEs in sediment from the Central Arctic Ocean represents only a very small amount of their total production volume, yet the amount of OPEs in Arctic Ocean sediment was significantly larger than the sum of polybrominated diphenyl ethers (PBDEs) in the sediment, indicating they are equally prone to long-range transport away from source regions. Given the increasing level of production and usage of OPEs as substitutes of PBDEs, OPEs will continue to accumulate in the remote Arctic.

  1. Biogeographic patterns of bacterial microdiversity in Arctic deep-sea sediments (HAUSGARTEN, Fram Strait).

    Science.gov (United States)

    Buttigieg, Pier Luigi; Ramette, Alban

    2014-01-01

    Marine bacteria colonizing deep-sea sediments beneath the Arctic ocean, a rapidly changing ecosystem, have been shown to exhibit significant biogeographic patterns along transects spanning tens of kilometers and across water depths of several thousand meters (Jacob et al., 2013). Jacob et al. (2013) adopted what has become a classical view of microbial diversity - based on operational taxonomic units clustered at the 97% sequence identity level of the 16S rRNA gene - and observed a very large microbial community replacement at the HAUSGARTEN Long Term Ecological Research station (Eastern Fram Strait). Here, we revisited these data using the oligotyping approach and aimed to obtain new insight into ecological and biogeographic patterns associated with bacterial microdiversity in marine sediments. We also assessed the level of concordance of these insights with previously obtained results. Variation in oligotype dispersal range, relative abundance, co-occurrence, and taxonomic identity were related to environmental parameters such as water depth, biomass, and sedimentary pigment concentration. This study assesses ecological implications of the new microdiversity-based technique using a well-characterized dataset of high relevance for global change biology.

  2. Distribution of 137Cs in samples of ocean bottom sediments of the baltic sea in 1982-1983

    International Nuclear Information System (INIS)

    Gedenov, L.I.; Flegontov, V.M.; Ivanova, L.M.; Kostandov, K.A.

    1986-01-01

    The concentration of Cs-137 in samples of ocean bottom sediments picked up in 1979 in the Gulf of Finland with a geological nozzle pipe varied within a wide interval of values. The results could indicate nonuniformity of the Cs-137 distribution in ocean bottom sediments as well as the penetration of significant amounts of Cs-137 to large depths. The main error resulted from the sampling technique employed because the upper part of the sediment could be lost. In 1982, a special ground-sampling device, with which the upper layer of sediments in the water layer close to the ocean bottom could be sampled, was tested in the Gulf of Finland and the Northeastern part of the Baltic Sea. The results of a layerwise determination of the Cs-137 concentration in samples of ocean bottom sediments of the Gulf of Finland and of the Baltic Sea are listed. The new soil-sampling device for picking samples of ocean sediments of undisturbed stratification will allow a correct determination of the radionuclide accumulation in the upper layers of ocean bottom sediments in the Baltic Sea

  3. Subsurface Hybrid Power Options for Oil & Gas Production at Deep Ocean Sites

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J C; Haut, R; Jahn, G; Goldman, J; Colvin, J; Karpinski, A; Dobley, A; Halfinger, J; Nagley, S; Wolf, K; Shapiro, A; Doucette, P; Hansen, P; Oke, A; Compton, D; Cobb, M; Kopps, R; Chitwood, J; Spence, W; Remacle, P; Noel, C; Vicic, J; Dee, R

    2010-02-19

    An investment in deep-sea (deep-ocean) hybrid power systems may enable certain off-shore oil and gas exploration and production. Advanced deep-ocean drilling and production operations, locally powered, may provide commercial access to oil and gas reserves otherwise inaccessible. Further, subsea generation of electrical power has the potential of featuring a low carbon output resulting in improved environmental conditions. Such technology therefore, enhances the energy security of the United States in a green and environmentally friendly manner. The objective of this study is to evaluate alternatives and recommend equipment to develop into hybrid energy conversion and storage systems for deep ocean operations. Such power systems will be located on the ocean floor and will be used to power offshore oil and gas exploration and production operations. Such power systems will be located on the oceans floor, and will be used to supply oil and gas exploration activities, as well as drilling operations required to harvest petroleum reserves. The following conceptual hybrid systems have been identified as candidates for powering sub-surface oil and gas production operations: (1) PWR = Pressurized-Water Nuclear Reactor + Lead-Acid Battery; (2) FC1 = Line for Surface O{sub 2} + Well Head Gas + Reformer + PEMFC + Lead-Acid & Li-Ion Batteries; (3) FC2 = Stored O2 + Well Head Gas + Reformer + Fuel Cell + Lead-Acid & Li-Ion Batteries; (4) SV1 = Submersible Vehicle + Stored O{sub 2} + Fuel Cell + Lead-Acid & Li-Ion Batteries; (5) SV2 = Submersible Vehicle + Stored O{sub 2} + Engine or Turbine + Lead-Acid & Li-Ion Batteries; (6) SV3 = Submersible Vehicle + Charge at Docking Station + ZEBRA & Li-Ion Batteries; (7) PWR TEG = PWR + Thermoelectric Generator + Lead-Acid Battery; (8) WELL TEG = Thermoelectric Generator + Well Head Waste Heat + Lead-Acid Battery; (9) GRID = Ocean Floor Electrical Grid + Lead-Acid Battery; and (10) DOC = Deep Ocean Current + Lead-Acid Battery.

  4. Benthic Oxygen Uptake in the Arctic Ocean Margins - A Case Study at the Deep-Sea Observatory HAUSGARTEN (Fram Strait.

    Directory of Open Access Journals (Sweden)

    Cecile Cathalot

    Full Text Available The past decades have seen remarkable changes in the Arctic, a hotspot for climate change. Nevertheless, impacts of such changes on the biogeochemical cycles and Arctic marine ecosystems are still largely unknown. During cruises to the deep-sea observatory HAUSGARTEN in July 2007 and 2008, we investigated the biogeochemical recycling of organic matter in Arctic margin sediments by performing shipboard measurements of oxygen profiles, bacterial activities and biogenic sediment compounds (pigment, protein, organic carbon, and phospholipid contents. Additional in situ oxygen profiles were performed at two sites. This study aims at characterizing benthic mineralization activity along local bathymetric and latitudinal transects. The spatial coverage of this study is unique since it focuses on the transition from shelf to Deep Ocean, and from close to the ice edge to more open waters. Biogeochemical recycling across the continental margin showed a classical bathymetric pattern with overall low fluxes except for the deepest station located in the Molloy Hole (5500 m, a seafloor depression acting as an organic matter depot center. A gradient in benthic mineralization rates arises along the latitudinal transect with clearly higher values at the southern stations (average diffusive oxygen uptake of 0.49 ± 0.18 mmol O2 m-2 d-1 compared to the northern sites (0.22 ± 0.09 mmol O2 m-2 d-1. The benthic mineralization activity at the HAUSGARTEN observatory thus increases southward and appears to reflect the amount of organic matter reaching the seafloor rather than its lability. Although organic matter content and potential bacterial activity clearly follow this gradient, sediment pigments and phospholipids exhibit no increase with latitude whereas satellite images of surface ocean chlorophyll a indicate local seasonal patterns of primary production. Our results suggest that predicted increases in primary production in the Arctic Ocean could induce a larger

  5. Pollutants' Release, Redistribution and Remediation of Black Smelly River Sediment Based on Re-Suspension and Deep Aeration of Sediment.

    Science.gov (United States)

    Zhu, Lin; Li, Xun; Zhang, Chen; Duan, Zengqiang

    2017-04-01

    Heavily polluted sediment is becoming an important part of water pollution, and this situation is particularly acute in developing countries. Sediment has gradually changed from being the pollution adsorbent to the release source and has influenced the water environment and public health. In this study, we evaluated the pollutant distribution in sediment in a heavily polluted river and agitated the sediment in a heavily polluted river to re-suspend it and re-release pollutants. We found that the levels of chemical oxygen demand (COD), NH₄⁺-N, total nitrogen (TN), and total phosphorus (TP) in overlying water were significantly increased 60 min after agitation. The distribution of the pollutants in the sediment present high concentrations of pollutants congregated on top of the sediment after re-settling, and their distribution decreased with depth. Before agitation, the pollutants were randomly distributed throughout the sediment. Secondly, deep sediment aeration equipment (a micro-porous air diffuser) was installed during the process of sedimentation to study the remediation of the sediment by continuous aeration. The results revealed that deep sediment aeration after re-suspension significantly promoted the degradation of the pollutants both in overlying water and sediment, which also reduced the thickness of the sediment from 0.9 m to 0.6 m. Therefore, sediment aeration after suspension was efficient, and is a promising method for sediment remediation applications.

  6. Ocean disposal of heat generating radioactive waste

    International Nuclear Information System (INIS)

    1984-12-01

    A study of container designs for heat generating radioactive waste disposal in the deep ocean sediments is presented. The purpose of the container would be to isolate the waste from the environment for a period of 500 to 1000 years. The container designs proposed are based on the use of either corrosion allowance or corrosion resistant metals. Appropriate overpack wall thicknesses are suggested for each design using the results of corrosion studies and experiments but these are necessarily preliminary and data relevant to corrosion in deep ocean sediments remain sparse. It is concluded that the most promising design concept involves a thin titanium alloy overpack in which all internal void spaces are filled with lead or cement grout. In situ temperatures for the sediment adjacent to the emplaced 50 year cooled waste containers are calculated to reach about 260 deg C. The behaviour of the sediments at such a high temperature is not well understood and the possibility of 100 years interim storage is recommended for consideration to allow further cooling. Further corrosion data and sediment thermal studies would be required to fully confirm the engineering feasibility of these designs. (author)

  7. Ship Sensor Observations for Life on the Edge 2003: Exploring Deep Ocean Habitats - Office of Ocean Exploration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Hourly measurements made by selected ship sensors on the R/V Seward Johnson during the "Life on the Edge 2003: Exploring Deep Ocean Habitats" expedition sponsored by...

  8. Fluvial fingerprints in northeast Pacific sediments: Unravelling terrestrial-ocean climate linkages

    Science.gov (United States)

    Vanlaningham, S. J.; Duncan, R.; Pisias, N.

    2004-12-01

    As the earth's climate history becomes better understood, it becomes clear that the terrestrial and oceanic systems interact in complex ways. This is seen in core sites offshore the Pacific Northwest (PNW) of North America. A correlation can be seen in oceanic biostratigraphic assemblages and down-core changes in terrestrial pollen types. However, it is difficult to determine whether this relationship is the result of a coupled migration of terrestrial vegetation and oceanic fauna on millennial timescales or the result of changes in ocean circulation patterns that create more complex pollen pathways to the core sites. This research begins to unravel the answers to this problem by examining down-core changes in sediment provenance on millennial timescales. Preliminary data characterize sediment of 24 rivers from ten geologic provinces between latitudes 36° N - 47° N. Through clay mineralogy, major and trace element geochemistry and Ar-Ar "province" ages, ten of the 24 rivers can be uniquely identified, while six of the ten geologic provinces can be uniquely constrained geochemically. With further Nd, Sr and Pb isotopic analyses, we hope to constrain the non-unique sediment sources. We will also be presenting initial down-core geochemical results from cores EW 9504-17PC and EW9504-13PC, offshore southern Oregon and central California, respectively.

  9. Ship Track for Operation Deep Scope 2005 - Office of Ocean Exploration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Ship track of R/V Seward Johnson during the "Operation Deep Scope 2005" expedition sponsored by the National Oceanic and Atmospheric Administration (NOAA) Office of...

  10. Short-chain alkane cycling in deep Gulf of Mexico cold-seep sediments

    Science.gov (United States)

    Sibert, R.; Joye, S. B.; Hunter, K.

    2015-12-01

    Mixtures of light hydrocarbon gases are common in deep Gulf of Mexico cold-seep sediments, and are typically dissolved in pore fluids, adsorbed to sediment particles, trapped in methane ice, or as free gas. The dominant component in these natural gas mixtures is usually methane (>80% C1), but ethane (C2) and propane (C3) are nearly always present in trace amounts (95% of the methane produced at depth never reaches the water column. Production of C1 and C2 in deep-sea sediments has been historically attributed only to thermocatalytic processes, though limited data suggests production of C2/C3 compounds through the activity of archaea at depth. Furthermore, carbon isotopic data on ethane and propane from deep cores of Gulf of Mexico sediments suggest alkanogenesis at >3 m depth in the sediment column and alkane oxidation in uppermost oxidant-rich sediments. Additional studies have also isolated microorganisms capable of oxidizing ethane and propane in the laboratory, but field studies of microbial-driven dynamics of C2/C3 gases in cold-seep sediments are rare. Here, we present the results of a series of incubation experiments using sediment slurries culled from surface sediments from one of the most prolific natural oil and gas seeps in the Gulf of Mexico. Rates of alkane oxidation were measured under a variety of conditions to assess the surface-driven microbial controls on C2/C3 cycling in cold-seep environments. Such microbial processes are important in terms of the possible 'oxidative overprinting' of alkane isotopic signatures produced at depth, possibly obscuring typical microbial isotopic signals.

  11. Dilution limits dissolved organic carbon utilization in the deep ocean

    NARCIS (Netherlands)

    Arrieta, J.M.; Mayol, E.; Hansman, R.L.; Herndl, G.J.; Dittmar, T.; Duarte, C.M.

    2015-01-01

    Oceanic dissolved organic carbon (DOC) is the second largest reservoir of organic carbon in the biosphere. About 72% of the global DOC inventory is stored in deep oceanic layers for years to centuries, supporting the current view that it consists of materials resistant to microbial degradation. An

  12. Behavior of candidate canister materials in deep ocean environments

    International Nuclear Information System (INIS)

    Smyrl, W.H.; Stephenson, L.L.; Braithwaite, J.W.

    1977-04-01

    Corrosion tests have been conducted under simulated deep ocean conditions for nine months. The materials tested were base alloys of titanium, zirconium, and nickel. All materials tested showed corrosion rates that were very low even at the highest test temperature. None showed susceptibility to either stress corrosion cracking or differential aeration corrosion. Ambient electrochemical tests confirmed the findings that none should be sensitive to differential oxygen effects. The zirconium alloys may be more susceptible to pitting corrosion than the others, although the pitting conditions are unlikely to be found in service, unless higher temperatures are encountered. All the alloys tested could give long life under deep ocean conditions and are candidates for more detailed corrosion studies

  13. Radium 226 in the deep north-eastern Atlantic Ocean

    International Nuclear Information System (INIS)

    Rhein, M.

    1986-01-01

    With reference to the distribution of radium-226 in the western equatorial and north-eastern deep Atlantic Ocean it was possible to establish structures in the correlations of radium-226 to its chemical homologue Ba and dissolved SiO 2 . An 11-box model of the deep Atlantic Ocean was used to obtain information on the size of the radium-226 and Ba sources. The soil source derives mainly from the dissolution of barite. For the first time, an evaluation of the radium-226 flow resulting from the dissolution of particulate matter is presented. The box model and the radium-226 concentrations measured put down the value as 23-46·10 -21 mol/m 2 s. (DG) [de

  14. Dispersal from deep ocean sources: physical and related scientific processes

    International Nuclear Information System (INIS)

    Robinson, A.R.; Kupferman, S.L.

    1985-02-01

    This report presents the results of the workshop ''Dispersal from Deep Ocean Sources: Physical and Related Scientific Processes,'' together with subsequent developments and syntheses of the material discussed there. The project was undertaken to develop usable predictive descriptions of dispersal from deep oceanic sources. Relatively simple theoretical models embodying modern ocean physics were applied, and observational and experimental data bases were exploited. All known physical processes relevant to the dispersal of passive, conservative tracers were discussed, and contact points for inclusion of nonconservative processes (biological and chemical) were identified. Numerical estimates of the amplitude, space, and time scales of dispersion were made for various mechanisms that control the evolution of the dispersal as the material spreads from a bottom point source to small-, meso-, and world-ocean scales. Recommendations for additional work are given. The volume is presented as a handbook of dispersion processes. It is intended to be updated as new results become available

  15. Ship Track for Deep Sea Medicines 2003 - Office of Ocean Exploration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Ship track of the Ronald H. Brown during the "Deep Sea Medicines 2003: Exploring the Gulf of Mexico" expedition sponsored by the National Oceanic and Atmospheric...

  16. /sup 226/Ra in the western Indian Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Y.

    1987-09-01

    /sup 226/Ra profiles have been measured in the western Indian Ocean as part of the 1977-78 Indian Ocean GEOSECS program. These profiles show a general increase in deep and bottom water Ra concentration from the Circumpolar region to the Arabian Sea. A deep Ra maximum which originates in the Arabian Sea and in the Somali basin at about 3000 m depth spreads southward into the Mascarene basin and remains discernible in the Madagascar and Crozet basins. In the western Indian Ocean, the cold Antarctic Bottom Water spreads northward under the possibly southward-flowing deep water, forming a clear benthic front along the Crozet basin across the Southwest Indian Ridge into the Madagascar and Mascarene basins. The Antarctic Bottom Water continues to spread farther north to the Somali basin through the Amirante Passage at 10/sup 0/S as a western boundary current. The benthic front and other characteristic features in the western Indian Ocean are quite similar to those observed in the western Pacific where the benthic front as a distinctive feature was first described by Craig et al. Across the Mid-Indian Ridge toward the Ceylon abyssal plain near the triple junction, Ra profiles display a layered structure, reflecting the topographic effect of the mid-ocean ridge system on the mixing and circulation of the deep and bottom waters. Both Ra and Si show a deep maximum north of the Madagascar Basin. Linear relationships between these two elements are observed in the deep and bottom water with slopes increasing northward. This suggests a preferential input of Ra over Si from the bottom sediments of the Arabian Sea and also from the flank sediments of the Somali basin.

  17. Production of fluorescent dissolved organic matter in Arctic Ocean sediments

    Science.gov (United States)

    Chen, Meilian; Kim, Ji-Hoon; Nam, Seung-Il; Niessen, Frank; Hong, Wei-Li; Kang, Moo-Hee; Hur, Jin

    2016-12-01

    Little is known about the production of fluorescent dissolved organic matter (FDOM) in the anoxic oceanic sediments. In this study, sediment pore waters were sampled from four different sites in the Chukchi-East Siberian Seas area to examine the bulk dissolved organic carbon (DOC) and their optical properties. The production of FDOM, coupled with the increase of nutrients, was observed above the sulfate-methane-transition-zone (SMTZ). The presence of FDOM was concurrent with sulfate reduction and increased alkalinity (R2 > 0.96, p  0.95, p CDOM and FDOM to the overlying water column, unearthing a channel of generally bio-refractory and pre-aged DOM to the oceans.

  18. Deep-sea bioluminescence blooms after dense water formation at the ocean surface.

    Directory of Open Access Journals (Sweden)

    Christian Tamburini

    Full Text Available The deep ocean is the largest and least known ecosystem on Earth. It hosts numerous pelagic organisms, most of which are able to emit light. Here we present a unique data set consisting of a 2.5-year long record of light emission by deep-sea pelagic organisms, measured from December 2007 to June 2010 at the ANTARES underwater neutrino telescope in the deep NW Mediterranean Sea, jointly with synchronous hydrological records. This is the longest continuous time-series of deep-sea bioluminescence ever recorded. Our record reveals several weeks long, seasonal bioluminescence blooms with light intensity up to two orders of magnitude higher than background values, which correlate to changes in the properties of deep waters. Such changes are triggered by the winter cooling and evaporation experienced by the upper ocean layer in the Gulf of Lion that leads to the formation and subsequent sinking of dense water through a process known as "open-sea convection". It episodically renews the deep water of the study area and conveys fresh organic matter that fuels the deep ecosystems. Luminous bacteria most likely are the main contributors to the observed deep-sea bioluminescence blooms. Our observations demonstrate a consistent and rapid connection between deep open-sea convection and bathypelagic biological activity, as expressed by bioluminescence. In a setting where dense water formation events are likely to decline under global warming scenarios enhancing ocean stratification, in situ observatories become essential as environmental sentinels for the monitoring and understanding of deep-sea ecosystem shifts.

  19. Deep-sea bioluminescence blooms after dense water formation at the ocean surface.

    Science.gov (United States)

    Tamburini, Christian; Canals, Miquel; Durrieu de Madron, Xavier; Houpert, Loïc; Lefèvre, Dominique; Martini, Séverine; D'Ortenzio, Fabrizio; Robert, Anne; Testor, Pierre; Aguilar, Juan Antonio; Samarai, Imen Al; Albert, Arnaud; André, Michel; Anghinolfi, Marco; Anton, Gisela; Anvar, Shebli; Ardid, Miguel; Jesus, Ana Carolina Assis; Astraatmadja, Tri L; Aubert, Jean-Jacques; Baret, Bruny; Basa, Stéphane; Bertin, Vincent; Biagi, Simone; Bigi, Armando; Bigongiari, Ciro; Bogazzi, Claudio; Bou-Cabo, Manuel; Bouhou, Boutayeb; Bouwhuis, Mieke C; Brunner, Jurgen; Busto, José; Camarena, Francisco; Capone, Antonio; Cârloganu, Christina; Carminati, Giada; Carr, John; Cecchini, Stefano; Charif, Ziad; Charvis, Philippe; Chiarusi, Tommaso; Circella, Marco; Coniglione, Rosa; Costantini, Heide; Coyle, Paschal; Curtil, Christian; Decowski, Patrick; Dekeyser, Ivan; Deschamps, Anne; Donzaud, Corinne; Dornic, Damien; Dorosti, Hasankiadeh Q; Drouhin, Doriane; Eberl, Thomas; Emanuele, Umberto; Ernenwein, Jean-Pierre; Escoffier, Stéphanie; Fermani, Paolo; Ferri, Marcelino; Flaminio, Vincenzo; Folger, Florian; Fritsch, Ulf; Fuda, Jean-Luc; Galatà, Salvatore; Gay, Pascal; Giacomelli, Giorgio; Giordano, Valentina; Gómez-González, Juan-Pablo; Graf, Kay; Guillard, Goulven; Halladjian, Garadeb; Hallewell, Gregory; van Haren, Hans; Hartman, Joris; Heijboer, Aart J; Hello, Yann; Hernández-Rey, Juan Jose; Herold, Bjoern; Hößl, Jurgen; Hsu, Ching-Cheng; de Jong, Marteen; Kadler, Matthias; Kalekin, Oleg; Kappes, Alexander; Katz, Uli; Kavatsyuk, Oksana; Kooijman, Paul; Kopper, Claudio; Kouchner, Antoine; Kreykenbohm, Ingo; Kulikovskiy, Vladimir; Lahmann, Robert; Lamare, Patrick; Larosa, Giuseppina; Lattuada, Dario; Lim, Gordon; Presti, Domenico Lo; Loehner, Herbert; Loucatos, Sotiris; Mangano, Salvatore; Marcelin, Michel; Margiotta, Annarita; Martinez-Mora, Juan Antonio; Meli, Athina; Montaruli, Teresa; Moscoso, Luciano; Motz, Holger; Neff, Max; Nezri, Emma Nuel; Palioselitis, Dimitris; Păvălaş, Gabriela E; Payet, Kevin; Payre, Patrice; Petrovic, Jelena; Piattelli, Paolo; Picot-Clemente, Nicolas; Popa, Vlad; Pradier, Thierry; Presani, Eleonora; Racca, Chantal; Reed, Corey; Riccobene, Giorgio; Richardt, Carsten; Richter, Roland; Rivière, Colas; Roensch, Kathrin; Rostovtsev, Andrei; Ruiz-Rivas, Joaquin; Rujoiu, Marius; Russo, Valerio G; Salesa, Francisco; Sánchez-Losa, Augustin; Sapienza, Piera; Schöck, Friederike; Schuller, Jean-Pierre; Schussler, Fabian; Shanidze, Rezo; Simeone, Francesco; Spies, Andreas; Spurio, Maurizio; Steijger, Jos J M; Stolarczyk, Thierry; Taiuti, Mauro G F; Toscano, Simona; Vallage, Bertrand; Van Elewyck, Véronique; Vannoni, Giulia; Vecchi, Manuela; Vernin, Pascal; Wijnker, Guus; Wilms, Jorn; de Wolf, Els; Yepes, Harold; Zaborov, Dmitry; De Dios Zornoza, Juan; Zúñiga, Juan

    2013-01-01

    The deep ocean is the largest and least known ecosystem on Earth. It hosts numerous pelagic organisms, most of which are able to emit light. Here we present a unique data set consisting of a 2.5-year long record of light emission by deep-sea pelagic organisms, measured from December 2007 to June 2010 at the ANTARES underwater neutrino telescope in the deep NW Mediterranean Sea, jointly with synchronous hydrological records. This is the longest continuous time-series of deep-sea bioluminescence ever recorded. Our record reveals several weeks long, seasonal bioluminescence blooms with light intensity up to two orders of magnitude higher than background values, which correlate to changes in the properties of deep waters. Such changes are triggered by the winter cooling and evaporation experienced by the upper ocean layer in the Gulf of Lion that leads to the formation and subsequent sinking of dense water through a process known as "open-sea convection". It episodically renews the deep water of the study area and conveys fresh organic matter that fuels the deep ecosystems. Luminous bacteria most likely are the main contributors to the observed deep-sea bioluminescence blooms. Our observations demonstrate a consistent and rapid connection between deep open-sea convection and bathypelagic biological activity, as expressed by bioluminescence. In a setting where dense water formation events are likely to decline under global warming scenarios enhancing ocean stratification, in situ observatories become essential as environmental sentinels for the monitoring and understanding of deep-sea ecosystem shifts.

  20. Waste disposal in the deep ocean: An overview

    International Nuclear Information System (INIS)

    O'Connor, T.P.; Kester, D.R.; Burt, W.V.; Capuzzo, J.M.; Park, P.K.; Duedall, I.W.

    1985-01-01

    Incineration at sea, industrial and sewage waste disposal in the surface mixing zone, and disposal of low-level nuclear wastes, obsolete munitions, and nerve gas onto the seafloor have been the main uses of the deep sea for waste management. In 1981 the wastes disposed of in the deep sea consisted of 48 X 10/sup 4/ t of liquid industrial wastes and 2 X 10/sup 4/ t of sewage sludge by the United States; 1.5 X 10/sup 4/ t (solids) of sewage sludge by the Federal Republic of German; 5300 t of liquid industrial wastes by Denmark; 99 t of solid industrial wastes by the United Kingdom; and 9400 t of low-level radioactive wastes by several European countries. Also in 1981 at-sea incineration of slightly more than 10/sup 5/ t of organic wastes from Belgium, France, the Federal Republic of Germany, the Netherlands, Norway, Sweden, and the United Kingdom was carried out in the North Sea. Unique oceanographic features of the deep sea include its large dilution capacity; the long residence time of deep-sea water (on the order of 10/sup 2/ y); low biological productivity in the surface water of the open ocean (≅50 g m/sup -2/ of carbon per year); the existence of an oxygen minimum zone at several hundred meters deep in the mid-latitudes; and the abyssal-clay regions showing sedimentary records of tens of millions of years of slow, uninterrupted deposition of fine-grained clay. Any deep-sea waste disposal strategy must take into account oceanic processes and current scientific knowledge in order to attain a safe solution that will last for centuries

  1. Bacterial niche-specific genome expansion is coupled with highly frequent gene disruptions in deep-sea sediments

    KAUST Repository

    Wang, Yong; Yang, Jiang Ke; Lee, On On; Li, Tie Gang; Al-Suwailem, Abdulaziz M.; Danchin, Antoine; Qian, Pei-Yuan

    2011-01-01

    The complexity and dynamics of microbial metagenomes may be evaluated by genome size, gene duplication and the disruption rate between lineages. In this study, we pyrosequenced the metagenomes of microbes obtained from the brine and sediment of a deep-sea brine pool in the Red Sea to explore the possible genomic adaptations of the microbes in response to environmental changes. The microbes from the brine and sediments (both surface and deep layers) of the Atlantis II Deep brine pool had similar communities whereas the effective genome size varied from 7.4 Mb in the brine to more than 9 Mb in the sediment. This genome expansion in the sediment samples was due to gene duplication as evidenced by enrichment of the homologs. The duplicated genes were highly disrupted, on average by 47.6% and 70% for the surface and deep layers of the Atlantis II Deep sediment samples, respectively. The disruptive effects appeared to be mainly due to point mutations and frameshifts. In contrast, the homologs from the Atlantis II Deep brine sample were highly conserved and they maintained relatively small copy numbers. Likely, the adaptation of the microbes in the sediments was coupled with pseudogenizations and possibly functional diversifications of the paralogs in the expanded genomes. The maintenance of the pseudogenes in the large genomes is discussed. © 2011 Wang et al.

  2. Bacterial niche-specific genome expansion is coupled with highly frequent gene disruptions in deep-sea sediments

    KAUST Repository

    Wang, Yong

    2011-12-21

    The complexity and dynamics of microbial metagenomes may be evaluated by genome size, gene duplication and the disruption rate between lineages. In this study, we pyrosequenced the metagenomes of microbes obtained from the brine and sediment of a deep-sea brine pool in the Red Sea to explore the possible genomic adaptations of the microbes in response to environmental changes. The microbes from the brine and sediments (both surface and deep layers) of the Atlantis II Deep brine pool had similar communities whereas the effective genome size varied from 7.4 Mb in the brine to more than 9 Mb in the sediment. This genome expansion in the sediment samples was due to gene duplication as evidenced by enrichment of the homologs. The duplicated genes were highly disrupted, on average by 47.6% and 70% for the surface and deep layers of the Atlantis II Deep sediment samples, respectively. The disruptive effects appeared to be mainly due to point mutations and frameshifts. In contrast, the homologs from the Atlantis II Deep brine sample were highly conserved and they maintained relatively small copy numbers. Likely, the adaptation of the microbes in the sediments was coupled with pseudogenizations and possibly functional diversifications of the paralogs in the expanded genomes. The maintenance of the pseudogenes in the large genomes is discussed. © 2011 Wang et al.

  3. Bacterial niche-specific genome expansion is coupled with highly frequent gene disruptions in deep-sea sediments.

    Directory of Open Access Journals (Sweden)

    Yong Wang

    Full Text Available The complexity and dynamics of microbial metagenomes may be evaluated by genome size, gene duplication and the disruption rate between lineages. In this study, we pyrosequenced the metagenomes of microbes obtained from the brine and sediment of a deep-sea brine pool in the Red Sea to explore the possible genomic adaptations of the microbes in response to environmental changes. The microbes from the brine and sediments (both surface and deep layers of the Atlantis II Deep brine pool had similar communities whereas the effective genome size varied from 7.4 Mb in the brine to more than 9 Mb in the sediment. This genome expansion in the sediment samples was due to gene duplication as evidenced by enrichment of the homologs. The duplicated genes were highly disrupted, on average by 47.6% and 70% for the surface and deep layers of the Atlantis II Deep sediment samples, respectively. The disruptive effects appeared to be mainly due to point mutations and frameshifts. In contrast, the homologs from the Atlantis II Deep brine sample were highly conserved and they maintained relatively small copy numbers. Likely, the adaptation of the microbes in the sediments was coupled with pseudogenizations and possibly functional diversifications of the paralogs in the expanded genomes. The maintenance of the pseudogenes in the large genomes is discussed.

  4. Crystal-chemical characteristics of nontronites from bottom sediments of Pacific ocean

    International Nuclear Information System (INIS)

    Palchik, N. A.; Moroz, T. N.; Grigorieva, T. N.; Nikandrova, N. K.; Miroshnichenko, L. V.

    2017-01-01

    A crystal-chemical analysis of the nontronite samples formed in deep-water sediments of the underwater Juan-de-Fuca ridge in the Pacific ocean has been performed using powder X-ray diffraction, IR spectroscopy, and Mössbauer spectroscopy. A comparison with the previously investigated nontronites from different regions of the Sea of Okhotsk showed that the structural features of these formations are due to the difference in the physicochemical parameters of their crystallization. The values of the basal interplanar spacing d_0_0_1 (within 11–13 Å) in the samples analyzed are determined by the degree of hydration and cation filling of the interlayer space, while the differences in the IR spectra are due to isomorphic substitutions in the structure. The character of cation distribution and the nature and concentration of stacking faults in nontronite structures are determined. The differences in the composition, structure, and properties of nontronites of different origin are confirmed by theoretical calculations of their structural parameters.

  5. Crystal-chemical characteristics of nontronites from bottom sediments of Pacific ocean

    Energy Technology Data Exchange (ETDEWEB)

    Palchik, N. A., E-mail: nadezhda@igm.nsc.ru; Moroz, T. N.; Grigorieva, T. N. [Russian Academy of Sciences, Sobolev Institute of Geology and Mineralogy, Siberian Branch (Russian Federation); Nikandrova, N. K. [Russian Academy of Sciences, Institute of Mineralogy, Ural Branch (Russian Federation); Miroshnichenko, L. V. [Russian Academy of Sciences, Sobolev Institute of Geology and Mineralogy, Siberian Branch (Russian Federation)

    2017-01-15

    A crystal-chemical analysis of the nontronite samples formed in deep-water sediments of the underwater Juan-de-Fuca ridge in the Pacific ocean has been performed using powder X-ray diffraction, IR spectroscopy, and Mössbauer spectroscopy. A comparison with the previously investigated nontronites from different regions of the Sea of Okhotsk showed that the structural features of these formations are due to the difference in the physicochemical parameters of their crystallization. The values of the basal interplanar spacing d{sub 001} (within 11–13 Å) in the samples analyzed are determined by the degree of hydration and cation filling of the interlayer space, while the differences in the IR spectra are due to isomorphic substitutions in the structure. The character of cation distribution and the nature and concentration of stacking faults in nontronite structures are determined. The differences in the composition, structure, and properties of nontronites of different origin are confirmed by theoretical calculations of their structural parameters.

  6. Biogeographic patterns of bacterial microdiversity in Arctic deep-sea sediments (Hausgarten, Fram Strait

    Directory of Open Access Journals (Sweden)

    Pier Luigi eButtigieg

    2015-01-01

    Full Text Available Marine bacteria colonising deep-sea sediments beneath the Arctic ocean, a rapidly changing ecosystem, have been shown to exhibit significant biogeographic patterns along transects spanning tens of kilometres and across water depths reaching several thousands of metres (Jacob et al., 2013. Jacob et al. adopted what has become a classical view of microbial diversity based on operational taxonomic units clustered at the 97% sequence identity level of the 16S rRNA gene and observed a very large microbial community replacement at the Hausgarten Long-Term Ecological Research station (Eastern Fram Strait. Here, we revisited these data using the oligotyping approach with the aims of obtaining new insights into ecological and biogeographic patterns associated with bacterial microdiversity in marine sediments and of assessing the level of concordance of these insights with previously obtained results. Variation in oligotype dispersal range, relative abundance, co-occurrence, and taxonomic identity were related to environmental parameters such as water depth, biomass, and sedimentary pigment concentration. This study assesses ecological implications of the new microdiversity-based technique using a well-characterised dataset of high relevance for global change biology.

  7. Open ocean pelago-benthic coupling: cyanobacteria as tracers of sedimenting salp faeces

    Science.gov (United States)

    Pfannkuche, Olaf; Lochte, Karin

    1993-04-01

    Coupling between surface water plankton and abyssal benthos was investigated during a mass development of salps ( Salpa fusiformis) in the Northeast Atlantic. Cyanobacteria numbers and composition of photosynthetic pigments were determined in faeces of captured salps from surface waters, sediment trap material, detritus from plankton hauls, surface sediments from 4500-4800 m depth and Holothurian gut contents. Cyanobacteria were found in all samples containing salp faeces and also in the guts of deep-sea Holothuria. The ratio between zeaxanthin (typical of cyanobacteria) and sum of chlorophyll a pigments was higher in samples from the deep sea when compared to fresh salp faeces, indicating that this carotenoid persisted longer in the sedimenting material than total chlorophyll a pigments. The microscopic and chemical observations allowed us to trace sedimenting salp faeces from the epipelagial to the abyssal benthos, and demonstrated their role as a fast and direct link between both systems. Cyanobacteria may provide a simple tracer for sedimenting phytodetritus.

  8. Ion transport in deep-sea sediments

    International Nuclear Information System (INIS)

    Heath, G.R.

    1979-01-01

    Initial assessment of the ability of deep-sea clays to contain nuclear waste is optimistic. Yet, the investigators have no delusions about the complexity of the natural geochemical system and the perturbations that may result from emplacement of thermally-hot waste cannisters. Even though they may never be able to predict the exact nature of all these perturbations, containment of the nuclides by the waste form/cannister system until most of the heat has decayed, and burial of the waste to a sufficient depth that the altered zone can be treated as a black box source of dissolved nuclides to the enclosing unperturbed sediment, encourage them to believe that ion migration in the deep seabed can be modeled accurately and that our preliminary estimates of migration rates are likely to be reasonably realistic

  9. Impacts of ocean acidification on sediment processes in shallow waters of the Arctic Ocean

    NARCIS (Netherlands)

    Gazeau, F.; van Rijswijk, P.; Pozzato, L.; Middelburg, J.J.

    Despite the important roles of shallow-water sediments in global biogeochemical cycling, the effects of ocean acidification on sedimentary processes have received relatively little attention. As high-latitude cold waters can absorb more CO2 and usually have a lower buffering capacity than warmer

  10. Impacts of Ocean Acidification on Sediment Processes in Shallow Waters of the Arctic Ocean

    NARCIS (Netherlands)

    Gazeau, F.; van Rijswijk, P.; Pozzato, L.; Middelburg, J.J.

    2014-01-01

    Despite the important roles of shallow-water sediments in global biogeochemical cycling, the effects of ocean acidification on sedimentary processes have received relatively little attention. As high-latitude cold waters can absorb more CO2 and usually have a lower buffering capacity than warmer

  11. Archive of Geosample Information from the British Ocean Sediment Core Research Facility (BOSCORF)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The British Ocean Sediment Core Research Facility (BOSCORF), National Oceanography Centre, is a contributor to the Index to Marine and Lacustrine Geological Samples...

  12. Deep ocean nutrients during the Last Glacial Maximum deduced from sponge silicon isotopic compositions

    Science.gov (United States)

    Hendry, Katharine R.; Georg, R. Bastian; Rickaby, Rosalind E. M.; Robinson, Laura F.; Halliday, Alex N.

    2010-04-01

    The relative importance of biological and physical processes within the Southern Ocean for the storage of carbon and atmospheric pCO 2 on glacial-interglacial timescales remains uncertain. Understanding the impact of surface biological production on carbon export in the past relies on the reconstruction of the nutrient supply from upwelling deep waters. In particular, the upwelling of silicic acid (Si(OH) 4) is tightly coupled to carbon export in the Southern Ocean via diatom productivity. Here, we address how changes in deep water Si(OH) 4 concentrations can be reconstructed using the silicon isotopic composition of deep-sea sponges. We report δ30Si of modern deep-sea sponge spicules and show that they reflect seawater Si(OH) 4 concentration. The fractionation factor of sponge δ30Si compared to seawater δ30Si shows a positive relationship with Si(OH) 4, which may be a growth rate effect. Application of this proxy in two down-core records from the Scotia Sea reveals that Si(OH) 4 concentrations in the deep Southern Ocean during the Last Glacial Maximum (LGM) were no different than today. Our result does not support a coupling of carbon and nutrient build up in an isolated deep ocean reservoir during the LGM. Our data, combined with records of stable isotopes from diatoms, are only consistent with enhanced LGM Southern Ocean nutrient utilization if there was also a concurrent reduction in diatom silicification or a shift from siliceous to organic-walled phytoplankton.

  13. Deep-ocean Assessment and Reporting of Tsunamis (DART) Stations

    Data.gov (United States)

    Department of Homeland Security — As part of the U.S. National Tsunami Hazard Mitigation Program (NTHMP), the Deep Ocean Assessment and Reporting of Tsunamis (DART(R)) Project is an ongoing effort to...

  14. Three dimensional investigation of oceanic active faults. A demonstration survey

    Energy Technology Data Exchange (ETDEWEB)

    Nakao, Seizo; Kishimoto, Kiyoyuki; Ikehara, Ken; Kuramoto, Shinichi; Sato, Mikio [Geological Survey of Japan, Kawasaki, Kanagawa (Japan)

    1999-02-01

    Oceanic active faults were classified into trench and in-land types, and a bottom survey was conducted on an aim of estimation on activity of a trench type oceanic active faults. For both sides of an oceanic active fault found at high precision sonic investigations in 1996 fiscal year, it was attempted from a record remained in sediments how a fault changed by a fault motion and how long time it acted. And, construction of a data base for evaluation of the active faults was promoted by generalizing the issued publications. As a result, it was found that a method to estimate a fault activity using turbidite in success at shallow sea could not easily be received at deep sea, and that as sedimentation method in deep sea changed largely by topography and so on, the turbidite did not play always a rule of key layer. (G.K.)

  15. The effects of post-accretion sedimentation on the magnetization of oceanic crust

    Science.gov (United States)

    Dyment, J.; Granot, R.

    2016-12-01

    The presence of marine magnetic anomalies related to seafloor spreading is often considered a key evidence to locate the continent-ocean boundary (COB) at passive margins. Conversely, thermal demagnetization is also advocated to explain the poor shape of such oceanic anomalies under thick sedimentary cover. To investigate the effects of post-accretion sedimentation on marine magnetic anomalies, we focus our study on two conjugate regions of the southern South Atlantic Ocean (Anomalies M4 to M0) that, although formed at the same time and along the same spreading segments, reveal contrasting characters. The anomalies exhibit strong amplitudes (>400 nT) and a well-marked shape off South Africa, where the sediments are less than 3 km-thick, but become weaker ( 200 nT) and much smoother off northern Argentina, where the sedimentary cover is thicker than 5 km. We interpret this observation as reflecting thermal demagnetization of the extrusive layer and its low Curie temperature titanomagnetite. We perform a series of thermo-magnetic models (Dyment and Arkani-Hamed, Geophys. J. Int., 1995, modified to include the sedimentary cover) to simulate the acquisition and loss of remanent magnetization in the oceanic lithosphere. We assume that most of the sediments accumulated shortly after crustal accretion. We investigate a range of possible thermal demagnetization temperatures for the extrusive layer and find that 200°C to 280ºC best explains the observations, in reasonable agreement with Curie temperatures of titanomagnetite, suggesting that most of the extrusive layer may be demagnetized under sediments thicker than 5 km. Thermal demagnetization should therefore be considered while interpreting marine magnetic anomalies for the age and nature of the crust (i.e., continental versus oceanic) in regions with thick sedimentary cover.

  16. Ship Sensor Observations for Operation Deep Scope 2007 - Office of Ocean Exploration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Hourly measurements made by selected ship sensors on the R/V Seward Johnson during the "Operation Deep Scope 2007" expedition sponsored by the National Oceanic and...

  17. Sediment plume monitoring in the Clarion-Clipperton Zone

    OpenAIRE

    Van den Eynde, D.; Baeye, M.; Fettweis, M.; Francken, F.; Naudts, L.; Van Lancker, V.

    2014-01-01

    OD Nature has a vast experience in monitoring and modelling Suspended Particulate Matter concentration in shelf areas. In the framework of the JPI-Oceans cruise with the RV Sonne in the Belgian, French and German concession zones for deep-sea mining in the Clarion-Clipperton Zone, this experience will be used to monitor sediments plumes, caused by deep-sea mning exploration activities.

  18. Global ocean conveyor lowers extinction risk in the deep sea

    Science.gov (United States)

    Henry, Lea-Anne; Frank, Norbert; Hebbeln, Dierk; Wienberg, Claudia; Robinson, Laura; van de Flierdt, Tina; Dahl, Mikael; Douarin, Mélanie; Morrison, Cheryl L.; López Correa, Matthias; Rogers, Alex D.; Ruckelshausen, Mario; Roberts, J. Murray

    2014-06-01

    General paradigms of species extinction risk are urgently needed as global habitat loss and rapid climate change threaten Earth with what could be its sixth mass extinction. Using the stony coral Lophelia pertusa as a model organism with the potential for wide larval dispersal, we investigated how the global ocean conveyor drove an unprecedented post-glacial range expansion in Earth's largest biome, the deep sea. We compiled a unique ocean-scale dataset of published radiocarbon and uranium-series dates of fossil corals, the sedimentary protactinium-thorium record of Atlantic meridional overturning circulation (AMOC) strength, authigenic neodymium and lead isotopic ratios of circulation pathways, and coral biogeography, and integrated new Bayesian estimates of historic gene flow. Our compilation shows how the export of Southern Ocean and Mediterranean waters after the Younger Dryas 11.6 kyr ago simultaneously triggered two dispersal events in the western and eastern Atlantic respectively. Each pathway injected larvae from refugia into ocean currents powered by a re-invigorated AMOC that led to the fastest postglacial range expansion ever recorded, covering 7500 km in under 400 years. In addition to its role in modulating global climate, our study illuminates how the ocean conveyor creates broad geographic ranges that lower extinction risk in the deep sea.

  19. Radiocarbon in particulate matter from the eastern sub-arctic Pacific Ocean: evidence of source of terrestrial carbon to the deep sea

    International Nuclear Information System (INIS)

    Druffel, E.R.M.; Honjo, S.; Griffin, S.; Wong, C.S.

    1986-01-01

    Carbon isotope ratios were measured in organic and inorganic carbon of settling particulate matter collected with a sediment trap at Ocean Station P in the Gulf of Alaska from March to October, 1983. Dissolved inorganic carbon (DIC) in surface sea water collected during two different seasons in 1984 were analyzed using large gas proportional counters and revealed a minimum seasonal Δ 14 C variation of 14 per thousand. Results show that the Δ 14 C of calcium carbonate sedimenting to the deep sea is the same as that measured in surface water DIC. In contrast, particulate organic carbon (POC) had significantly higher Δ 14 C values (by 25-70 per thousand) than that in surface water DIC. Also, the Δ 13 C of the POC was markedly lower than previously reported values from other trap stations and marine particulate matter in general. Results from this study suggest that a significant amount of the POC settling to the deep sea at this pelagic station is of terrestrial origin, not strictly of marine origin as had previously been believed

  20. Environmental monitoring and deep ocean disposal of packaged radioactive waste

    International Nuclear Information System (INIS)

    Mitchell, N.T.; Preston, A.

    1980-01-01

    Environmental monitoring in the context of the dumping of packaged radioactive waste in the deep ocean is discussed in detail. The principles and objectives laid down by the IAEA and the ICRP are reviewed. Monitoring and its relationships to radiation exposure, research, control measures and public information are described. Finally, the actual practice in the UK of environmental monitoring is detailed for the measurable case of liquid wastes in coastal waters and also for package waste in deep oceans which has to be calculated. It is concluded that better mathematical models are needed to predict the dose to man and that more research into oceanographic and biological transfer processes should be carried out. (UK)

  1. Picocyanobacteria and deep-ocean fluorescent dissolved organic matter share similar optical properties

    Science.gov (United States)

    Zhao, Zhao; Gonsior, Michael; Luek, Jenna; Timko, Stephen; Ianiri, Hope; Hertkorn, Norbert; Schmitt-Kopplin, Philippe; Fang, Xiaoting; Zeng, Qinglu; Jiao, Nianzhi; Chen, Feng

    2017-05-01

    Marine chromophoric dissolved organic matter (CDOM) and its related fluorescent components (FDOM), which are widely distributed but highly photobleached in the surface ocean, are critical in regulating light attenuation in the ocean. However, the origins of marine FDOM are still under investigation. Here we show that cultured picocyanobacteria, Synechococcus and Prochlorococcus, release FDOM that closely match the typical fluorescent signals found in oceanic environments. Picocyanobacterial FDOM also shows comparable apparent fluorescent quantum yields and undergoes similar photo-degradation behaviour when compared with deep-ocean FDOM, further strengthening the similarity between them. Ultrahigh-resolution mass spectrometry (MS) and nuclear magnetic resonance spectroscopy reveal abundant nitrogen-containing compounds in Synechococcus DOM, which may originate from degradation products of the fluorescent phycobilin pigments. Given the importance of picocyanobacteria in the global carbon cycle, our results indicate that picocyanobacteria are likely to be important sources of marine autochthonous FDOM, which may accumulate in the deep ocean.

  2. The onset of fabric development in deep marine sediments

    NARCIS (Netherlands)

    Maffione, Marco; Morris, Antony

    2017-01-01

    Post-depositional compaction is a key stage in the formation of sedimentary rocks that results in porosity reduction, grain realignment and the production of sedimentary fabrics. The progressive time-depth evolution of the onset of fabric development in deep marine sediments is poorly constrained

  3. Geotechnical deep ocean research apparatus (DORA)

    International Nuclear Information System (INIS)

    1986-01-01

    As part of the research programme on radioactive waste disposal in seabed geological formations, a Deep Ocean Research Apparatus (DORA) seabed machine has been conceptually designed and prototypes of principal subsystems built and tested by four DORA Project partners. The DORA is designed to operate in 6000 m of water and drive a string of test rods and a piezocone about 50 m into soft soil. Partner responsibility was Fugro for project management and the penetration apparatus; ISMES for data acquisition and control; Laboratorium voor Grondmechanica for the piezocone probe and its sensors; and Marine Structure Consultants for the mission profile and DORA handling requirements. The DORA will have a maximum thrust of 50 kN. The probe will measure cone resistance, sleeve friction, pore pressure and inclination. Stability on the seabed will be assisted by using a combination of polyester and polypropylene-nylon (double) braided rope. A continuous wheel-drive subsystem will drive the test rods. Gelled or lead-acid batteries can power a hydraulic powerpack. Acoustic data transmission will be used. Software for data processing automation has been tested with simulation of all input channels. Successful operation of subsystem prototypes indicates that a DORA can be constructed at any future time for use on fundamental or applied deep ocean science and seafloor engineering investigations by industry, government and universities

  4. Ploughing the deep sea floor.

    Science.gov (United States)

    Puig, Pere; Canals, Miquel; Company, Joan B; Martín, Jacobo; Amblas, David; Lastras, Galderic; Palanques, Albert

    2012-09-13

    Bottom trawling is a non-selective commercial fishing technique whereby heavy nets and gear are pulled along the sea floor. The direct impact of this technique on fish populations and benthic communities has received much attention, but trawling can also modify the physical properties of seafloor sediments, water–sediment chemical exchanges and sediment fluxes. Most of the studies addressing the physical disturbances of trawl gear on the seabed have been undertaken in coastal and shelf environments, however, where the capacity of trawling to modify the seafloor morphology coexists with high-energy natural processes driving sediment erosion, transport and deposition. Here we show that on upper continental slopes, the reworking of the deep sea floor by trawling gradually modifies the shape of the submarine landscape over large spatial scales. We found that trawling-induced sediment displacement and removal from fishing grounds causes the morphology of the deep sea floor to become smoother over time, reducing its original complexity as shown by high-resolution seafloor relief maps. Our results suggest that in recent decades, following the industrialization of fishing fleets, bottom trawling has become an important driver of deep seascape evolution. Given the global dimension of this type of fishery, we anticipate that the morphology of the upper continental slope in many parts of the world’s oceans could be altered by intensive bottom trawling, producing comparable effects on the deep sea floor to those generated by agricultural ploughing on land.

  5. Bacterial biogeography influenced by shelf-basin exchange in the Arctic surface sediment at the Chukchi Borderland.

    Science.gov (United States)

    Han, Dukki; Nam, Seung-Il; Ha, Ho Kyung; Kim, Hyoungjun; Sadowsky, Michael J; Lee, Yoo Kyung; Hur, Hor-Gil

    2016-02-01

    It has been known that continental shelves around the Arctic Ocean play a major role in the ventilation of the deep basins as a consequence of shelf-basin exchange. In the present study, we found that bacterial assemblage of the surface sediment was different from that of seawater while seawater harboured local bacterial assemblages in response to the Arctic hydrography. This finding suggests that the Arctic seafloor sediments may have distinctive bacterial biogeography. Moreover, the distribution of bacterial assemblages and physicochemical properties in surface sediments changed gradually from the Arctic continental shelf to deep-sea basin. Based on the results, bacterial biogeography in the Arctic seafloor sediments may be influenced by winnowing and re-deposition of surface sediments through the sediment gravity flow. The present study offers a deeper understanding of shelf convection and its role for the construction of bacterial assemblages in the Arctic Ocean. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

  6. The oceanic chemistry of the U- and Th-series nuclides

    International Nuclear Information System (INIS)

    Cochran, J.K.

    1982-01-01

    The subject is discussed under the headings: input and removal of U- and Th-series nuclides in the oceans; uranium (input to the oceans; in the coastal ocean; in the open ocean; in sediment pore water; removal from the oceans; sources and sinks of 234 U in the oceans); thorium (scavenging in the deep sea; 230 Th and 231 Pa balance; removal from the coastal and surface ocean); Ra-226 and Ra-228; radon (in surface waters; near bottom 222 Rn as a tracer for vertical mixing); lead-210; polonium-210. (U.K.)

  7. Astronomical calibration of the first Toba super-eruption from deep-sea sediments

    Science.gov (United States)

    Lee, M.; Chen, C.; Wei, K.; Iizuka, Y.

    2003-04-01

    Correlations between tephra layers interbedded within deep-sea cores and radiometrically dated volcanic eruptions provide an independent means of verifying dating techniques developed for sediment cores. Alternatively, the chronostratigraphic framework developed from marine sediments can be used to calibrate ages of land-base eruptions, if geochemical correlations can be established. In this study, we examined three deep-sea cores along an east-west transection across the South China Sea, with a distance of ~1800 to 2500 km away from the Toba caldera. The occurrence of the Oldest Toba Tuff was recognized on the basis of its geochemical characteristics, such as a high-silicate, high-potassium content and a distinct strontium isotope composition. The correlative tephra layer occurs slightly above the Australasian microtektite layer and below the Brunhes/Matuyama boundary, which in constitute three time-parallel markers for correlation and dating of Quaternary stratigraphic records. Against the astronomically tuned oxygen isotope chronostratigraphy, the rhyolitic ignimbrite erupted during the transition from marine isotope stage 20 (glacial) to stage 19 (interglacial) with an estimated age of 788 ka. The refined age is in good agreement with the radiometric age of 800+20 ka for Layer D of ODP Site 758 (Hall and Farrell, 1995), but significantly younger than the commonly referred age of 840+30 ka (Diehl et al., 1987). The mid-Pleistocene eruption expelled at least 800-1000 km3 dense-rock-equivalent of rhyolitic magma taking into account the widespread ashfall deposits in the Indian Ocean and the South China Sea basins. In spite of its exceptional magnitude, the timing of the first Toba super-eruption disputes a possible causal linkage between a major volcanic eruption and a long-term global climatic deterioration.

  8. Role of time series sediment traps in understanding the Indian summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Guptha, M.V.S.

    particles or sediment or larger accumulations called marine snow – which are comprised of organic matter, dead organisms, tiny shells, dust particles, minerals etc. These sediment traps are capable of collecting settling particles hourly to yearly time... were demonstrated by Honjo (1982) and Deuser et al. (1983). Analysis of the samples helps in understanding how fast various particulate matter, nutrients etc move from the ocean surface to the deep ocean. Because, these materials are largely used...

  9. A new macrofaunal limit in the deep biosphere revealed by extreme burrow depths in ancient sediments.

    Science.gov (United States)

    Cobain, S L; Hodgson, D M; Peakall, J; Wignall, P B; Cobain, M R D

    2018-01-10

    Macrofauna is known to inhabit the top few 10s cm of marine sediments, with rare burrows up to two metres below the seabed. Here, we provide evidence from deep-water Permian strata for a previously unrecognised habitat up to at least 8 metres below the sediment-water interface. Infaunal organisms exploited networks of forcibly injected sand below the seabed, forming living traces and reworking sediment. This is the first record that shows sediment injections are responsible for hosting macrofaunal life metres below the contemporaneous seabed. In addition, given the widespread occurrence of thick sandy successions that accumulate in deep-water settings, macrofauna living in the deep biosphere are likely much more prevalent than considered previously. These findings should influence future sampling strategies to better constrain the depth range of infaunal animals living in modern deep-sea sands. One Sentence Summary: The living depth of infaunal macrofauna is shown to reach at least 8 metres in new habitats associated with sand injections.

  10. Restricted Inter-ocean Exchange and Attenuated Biological Export Caused Enhanced Carbonate Preservation in the PETM Ocean

    Science.gov (United States)

    Luo, Y.; Boudreau, B. P.; Dickens, G. R.; Sluijs, A.; Middelburg, J. J.

    2015-12-01

    Carbon dioxide (CO2) release during the Paleocene-Eocene Thermal Maximum (PETM, 55.8 Myr BP) acidified the oceans, causing a decrease in calcium carbonate (CaCO3) preservation. During the subsequent recovery from this acidification, the sediment CaCO3 content came to exceed pre-PETM values, known as over-deepening or over-shooting. Past studies claim to explain these trends, but have failed to reproduce quantitatively the time series of CaCO3 preservation. We employ a simple biogeochemical model to recreate the CaCO3 records preserved at Walvis Ridge of the Atlantic Ocean. Replication of the observed changes, both shallowing and the subsequent over-deepening, requires two conditions not previously considered: (1) limited deep-water exchange between the Indo-Atlantic and Pacific oceans and (2) a ~50% reduction in the export of CaCO3 to the deep sea during acidification. Contrary to past theories that attributed over-deepening to increased riverine alkalinity input, we find that over-deepening is an emergent property, generated at constant riverine input when attenuation of CaCO3 export causes an unbalanced alkalinity input to the deep oceans (alkalinization) and the development of deep super-saturation. Restoration of CaCO3 export, particularly in the super-saturated deep Indo-Atlantic ocean, later in the PETM leads to greater accumulation of carbonates, ergo over-shooting, which returns the ocean to pre-PETM conditions over a time scale greater than 200 kyr. While this feedback between carbonate export and the riverine input has not previously been considered, it appears to constitute an important modification of the classic carbonate compensation concept used to explain oceanic response to acidification.

  11. Narrowing the uncertainty for deep-ocean injection efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Orr, J.C.; Aumont, O. [Laboratoire des Sciences du Climat et de l' Environnement, CEA-CNRS, Gif-sur-Yvette (France); Yool, A. [Southampton Oceanography Centre, Southampton (United Kingdom); Plattner, G.K.; Joos, F. [Bern Univ., Bern (Switzerland). Physics Inst.; Maier-Reimer, E. [Max Planck Inst. fuer Meteorologie, Hamburg (Germany); Weirig, M.F.; Schlitzer, R. [Alfred Wegener Inst. for Polar and Marine Research, Bremerhaven (Germany); Caldeira, K.; Wickett, M.E. [Lawrence Livermore National Laboratory, CA (United States); Matear, R.J. [Australian Commonwealth Scientific and Research Organization, Hobart (Australia); Mignone, B.K.; Sarmiento, J.L. [Princeton Univ., Princeton, NJ (United States). AOS Program

    2005-07-01

    Ten ocean general circulation models (OCGMs) were compared as part of an international study investigating the ocean's ability to efficiently sequester carbon dioxide (CO{sub 2}). The models were selected for their ability to simulate radiocarbon and CFC-11. All of the model simulations neglected the influence of marine biota, and the simulations used only dissolved inorganic carbon (DIC) as a tracer in order to conserve computing resources. The models were integrated using standard ocean carbon-cycle model intercomparison project (OCMIP) formulations for gas exchange boundary conditions to obtain pre-industrial conditions. All models used the same predefined atmospheric CO{sub 2} records compiled from 1765 to 2000, as well as future scenarios in which atmospheric CO{sub 2} was stabilized at 650 ppm. Injections occurred over a period of 100 years. Results of the study showed that global budgets for CFC-11 and radiocarbon were correlated with global efficiencies for a 3000 m injection simulation. The 3000 m injection efficiency was then correlated with the global mean for deep natural radiocarbon. Results showed that simultaneously accounting for constraints from both CFC-11 and natural radiocarbon narrowed the range for a 3000 m injection efficiency in the year 2500 by a factor of 4. The study showed that models must be able to simulate global inventories for CFC-11 as well as global means for radiocarbon in deep ocean scenarios in order to be credible. It was concluded that models using both constraints will more accurately simulate global injection efficiencies.

  12. Residual β activity of particulate 234Th as a novel proxy for tracking sediment resuspension in the ocean

    Science.gov (United States)

    Lin, Wuhui; Chen, Liqi; Zeng, Shi; Li, Tao; Wang, Yinghui; Yu, Kefu

    2016-01-01

    Sediment resuspension occurs in the global ocean, which greatly affects material exchange between the sediment and the overlying seawater. The behaviours of carbon, nutrients, heavy metals, and other pollutants at the sediment-seawater boundary will further link to climate change, eutrophication, and marine pollution. Residual β activity of particulate 234Th (RAP234) is used as a novel proxy to track sediment resuspension in different marine environments, including the western Arctic Ocean, the South China Sea, and the Southern Ocean. Sediment resuspension identified by high activity of RAP234 is supported by different lines of evidence including seawater turbidity, residence time of total 234Th, Goldschmidt’s classification, and ratio of RAP234 to particulate organic carbon. A conceptual model is proposed to elucidate the mechanism for RAP234 with dominant contributions from 234Th-238U and 212Bi-228Th. The ‘slope assumption’ for RAP234 indicated increasing intensity of sediment resuspension from spring to autumn under the influence of the East Asian monsoon system. RAP234 can shed new light on 234Th-based particle dynamics and should benefit the interpretation of historical 234Th-238U database. RAP234 resembles lithophile elements and has broad implications for investigating particle dynamics in the estuary-shelf-slope-ocean continuum and linkage of the atmosphere-ocean-sediment system. PMID:27252085

  13. Residual β activity of particulate (234)Th as a novel proxy for tracking sediment resuspension in the ocean.

    Science.gov (United States)

    Lin, Wuhui; Chen, Liqi; Zeng, Shi; Li, Tao; Wang, Yinghui; Yu, Kefu

    2016-06-02

    Sediment resuspension occurs in the global ocean, which greatly affects material exchange between the sediment and the overlying seawater. The behaviours of carbon, nutrients, heavy metals, and other pollutants at the sediment-seawater boundary will further link to climate change, eutrophication, and marine pollution. Residual β activity of particulate (234)Th (RAP234) is used as a novel proxy to track sediment resuspension in different marine environments, including the western Arctic Ocean, the South China Sea, and the Southern Ocean. Sediment resuspension identified by high activity of RAP234 is supported by different lines of evidence including seawater turbidity, residence time of total (234)Th, Goldschmidt's classification, and ratio of RAP234 to particulate organic carbon. A conceptual model is proposed to elucidate the mechanism for RAP234 with dominant contributions from (234)Th-(238)U and (212)Bi-(228)Th. The 'slope assumption' for RAP234 indicated increasing intensity of sediment resuspension from spring to autumn under the influence of the East Asian monsoon system. RAP234 can shed new light on (234)Th-based particle dynamics and should benefit the interpretation of historical (234)Th-(238)U database. RAP234 resembles lithophile elements and has broad implications for investigating particle dynamics in the estuary-shelf-slope-ocean continuum and linkage of the atmosphere-ocean-sediment system.

  14. Reactive Fe(II) layers in deep-sea sediments

    Science.gov (United States)

    König, Iris; Haeckel, Matthias; Drodt, Matthias; Suess, Erwin; Trautwein, Alfred X.

    1999-05-01

    The percentage of the structural Fe(II) in clay minerals that is readily oxidized to Fe(III) upon contact with atmospheric oxygen was determined across the downcore tan-green color change in Peru Basin sediments. This latent fraction of reactive Fe(II) was only found in the green strata, where it proved to be large enough to constitute a deep reaction layer with respect to the pore water O 2 and NO 3-. Large variations were detected in the proportion of the reactive Fe(II) concentration to the organic matter content along core profiles. Hence, the commonly observed tan-green color change in marine sediments marks the top of a reactive Fe(II) layer, which may represent the major barrier to the movement of oxidation fronts in pelagic subsurface sediments. This is also demonstrated by numerical model simulations. The findings imply that geochemical barriers to pore water oxidation fronts form diagenetically in the sea floor wherever the stage of iron reduction is reached, provided that the sediments contain a significant amount of structural iron in clay minerals.

  15. Dissolution of methane bubbles with hydrate armoring in deep ocean conditions

    Science.gov (United States)

    Kovalchuk, Margarita; Socolofsky, Scott

    2017-11-01

    The deep ocean is a storehouse of natural gas. Methane bubble moving upwards from marine sediments may become trapped in gas hydrates. It is uncertain precisely how hydrate armoring affects dissolution, or mass transfer from the bubble to the surrounding water column. The Texas A&M Oilspill Calculator was used to simulate a series of gas bubble dissolution experiments conducted in the United States Department of Energy National Energy Technology Laboratory High Pressure Water Tunnel. Several variations of the mass transfer coefficient were calculated based on gas or hydrate phase solubility and clean or dirty bubble correlations. Results suggest the mass transfer coefficient may be most closely modeled with gas phase solubility and dirty bubble correlation equations. Further investigation of hydrate bubble dissolution behavior will refine current numeric models which aid in understanding gas flux to the atmosphere and plumes such as oil spills. Research funded in part by the Texas A&M University 2017 Undergraduate Summer Research Grant and a Grant from the Methane Gas Hydrates Program of the US DOE National Energy Technology Laboratory.

  16. Increased particle flux to the deep ocean related to monsoons

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, R.R.; Ittekkot, V.; Manganini, S.J.; Ramaswamy, V.; Haake, B.; Degens, E.T.; Desai, B.N.; Honjo, S.

    . To assess the impact of monsoon-driven processes on the downward particle flux variations in the open ocean we deployed three moored arrays consisting of six time-series sediment traps at selected locations in the western, central and eastern parts...

  17. Siderophile element concentrations in magnetic spherules from deep sea sediments revealed by instrumental neutron activation analysis

    International Nuclear Information System (INIS)

    Nogami, Ken-ichi; Shimamura, Tadashi; Tazawa, Yuji; Yamakoshi, Kazuo.

    1980-01-01

    For the purpose of deciding the extraterrestrial origin of the magnetic spherules found in deep sea sediments, the siderophile elements Co, Ni, Ir and/or Au etc., were measured by instrumental neutron activation analysis. Spherules were collected from red clay samples which were dredged from Mid Pacific Ocean. Only spherules which had smooth surfaces and relatively high specific gravities were chosen for analysis. Existence of Co, Ni and Ir in most spherules suggests the possibility of an extraterrestrial origin for these spherules. It is not clear whether these spherules are droplets ablated from iron meteorites entering into the Earth's atmosphere or they are cosmic iron grains themselves. X-ray diffraction analysis suggested that these spherules are the products of rapid cooling materials. (author)

  18. Event sedimentation in low-latitude deep-water carbonate basins, Anegada passage, northeast Caribbean

    Science.gov (United States)

    Chaytor, Jason D.; ten Brink, Uri S.

    2015-01-01

    The Virgin Islands and Whiting basins in the Northeast Caribbean are deep, structurally controlled depocentres partially bound by shallow-water carbonate platforms. Closed basins such as these are thought to document earthquake and hurricane events through the accumulation of event layers such as debris flow and turbidity current deposits and the internal deformation of deposited material. Event layers in the Virgin Islands and Whiting basins are predominantly thin and discontinuous, containing varying amounts of reef- and slope-derived material. Three turbidites/sandy intervals in the upper 2 m of sediment in the eastern Virgin Islands Basin were deposited between ca. 2000 and 13 600 years ago, but do not extend across the basin. In the central and western Virgin Islands Basin, a structureless clay-rich interval is interpreted to be a unifite. Within the Whiting Basin, several discontinuous turbidites and other sand-rich intervals are primarily deposited in base of slope fans. The youngest of these turbidites is ca. 2600 years old. Sediment accumulation in these basins is low (−1) for basin adjacent to carbonate platform, possibly due to limited sediment input during highstand sea-level conditions, sediment trapping and/or cohesive basin walls. We find no evidence of recent sediment transport (turbidites or debris flows) or sediment deformation that can be attributed to the ca. M7.2 1867 Virgin Islands earthquake whose epicentre was located on the north wall of the Virgin Islands Basin or to recent hurricanes that have impacted the region. The lack of significant appreciable pebble or greater size carbonate material in any of the available cores suggests that submarine landslide and basin-wide blocky debris flows have not been a significant mechanism of basin margin modification in the last several thousand years. Thus, basins such as those described here may be poor recorders of past natural hazards, but may provide a long-term record of past oceanographic

  19. Persistence of deeply sourced iron in the Pacific Ocean.

    Science.gov (United States)

    Horner, Tristan J; Williams, Helen M; Hein, James R; Saito, Mak A; Burton, Kevin W; Halliday, Alex N; Nielsen, Sune G

    2015-02-03

    Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe-Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface.

  20. Amino acid stable isotope applications to deep-sea corals: A molecular geochemistry approach to reconstructing past ocean conditions

    Science.gov (United States)

    McMahon, K.; McCarthy, M. D.; Guilderson, T. P.; Sherwood, O.; Williams, B.; Larsen, T.; Glynn, D. S.

    2017-12-01

    Future climate change is predicted to alter ocean productivity, food web dynamics, biogeochemical cycling, and the efficacy of the biological pump. Proteinaceous deep-sea corals act as "living sediment traps," providing long-term, high-resolution records of exported surface ocean production and a window into past changes in ocean condition as a historical context for potential future changes. Here, we present recent work developing the application of compound-specific stable isotope analysis of individual amino acids to proteinaceous deep-sea corals to reconstruct past changes in phytoplankton community composition and biogeochemical cycling. We present new calibrations for molecular isotope comparisons between metabolically active coral polyp tissue and bioarchival proteinaceous skeleton. We then applied these techniques to deep-sea corals from the North Pacific Subtropical Gyre (NPSG) to reconstruct centennial to millennial time scale changes in phytoplankton community composition and biogeochemical cycling as a function of regional climate change. This work suggests that the NPSG has undergone multiple major phytoplankton regime shifts over the last millennium between prokaryotic and eukaryotic phytoplankton communities and associated sources of nitrogen fueling production. The most recent regime, which started around the end of the Little Ice Age and the onset of the Industrial era, is unprecedented in the last 1000 years and resulted in a 30-50% increase in diazotrophic cyanobacteria contribution to export production and an associated 17-27% increase in N2-fixation in the NPSG over last century. By offering the first direct phylogenetic context for long-term shifts in isotopic records of exported particulate organic matter, our data represent a major step forward in understanding the evolution of marine plankton community dynamics, food web architecture, biogeochemical cycling, and the climate feedback loops through the biological pump.

  1. Impact of sinking carbon flux on accumulation of deep-ocean carbon in the Northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, V.V.S.S.; DileepKumar, M.; Saino, T.

    calculations using 14 C activity arises from the separation of natural 90 Biogeochemistry (2007) 82:89–100 123 and bomb-produced 14 C. Rubin and Key (2002) proposed the potential alkalinity method to achieve the separation. However, they found anomalous scatter... in the relationship between 14 C and potential alkalinity caused by data from the northern Indian Ocean (north of equator) and attributed that to the possible transportation of bomb radiocarbon, as carbonate particles from the surface ocean to the sediment...

  2. Processes governing transient responses of the deep ocean buoyancy budget to a doubling of CO2

    Science.gov (United States)

    Palter, J. B.; Griffies, S. M.; Hunter Samuels, B. L.; Galbraith, E. D.; Gnanadesikan, A.

    2012-12-01

    Recent observational analyses suggest there is a temporal trend and high-frequency variability in deep ocean buoyancy in the last twenty years, a phenomenon reproduced even in low-mixing models. Here we use an earth system model (GFDL's ESM2M) to evaluate physical processes that influence buoyancy (and thus steric sea level) budget of the deep ocean in quasi-steady state and under a doubling of CO2. A new suite of model diagnostics allows us to quantitatively assess every process that influences the buoyancy budget and its temporal evolution, revealing surprising dynamics governing both the equilibrium budget and its transient response to climate change. The results suggest that the temporal evolution of the deep ocean contribution to sea level rise is due to a diversity of processes at high latitudes, whose net effect is then advected in the Eulerian mean flow to mid and low latitudes. In the Southern Ocean, a slowdown in convection and spin up of the residual mean advection are approximately equal players in the deep steric sea level rise. In the North Atlantic, the region of greatest deep steric sea level variability in our simulations, a decrease in mixing of cold, dense waters from the marginal seas and a reduction in open ocean convection causes an accumulation of buoyancy in the deep subpolar gyre, which is then advected equatorward.

  3. Use of a free ocean CO₂ enrichment (FOCE) system to evaluate the effects of ocean acidification on the foraging behavior of a deep-sea urchin.

    Science.gov (United States)

    Barry, James P; Lovera, Chris; Buck, Kurt R; Peltzer, Edward T; Taylor, Josi R; Walz, Peter; Whaling, Patrick J; Brewer, Peter G

    2014-08-19

    The influence of ocean acidification in deep-sea ecosystems is poorly understood but is expected to be large because of the presumed low tolerance of deep-sea taxa to environmental change. We used a newly developed deep-sea free ocean CO2 enrichment (dp-FOCE) system to evaluate the potential consequences of future ocean acidification on the feeding behavior of a deep-sea echinoid, the sea urchin, Strongylocentrotus fragilis. The dp-FOCE system simulated future ocean acidification inside an experimental enclosure where observations of feeding behavior were performed. We measured the average movement (speed) of urchins as well as the time required (foraging time) for S. fragilis to approach its preferred food (giant kelp) in the dp-FOCE chamber (-0.46 pH units) and a control chamber (ambient pH). Measurements were performed during each of 4 trials (days -2, 2, 24, 27 after CO2 injection) during the month-long period when groups of urchins were continuously exposed to low pH or control conditions. Although urchin speed did not vary significantly in relation to pH or time exposed, foraging time was significantly longer for urchins in the low-pH treatment. This first deep-sea FOCE experiment demonstrated the utility of the FOCE system approach and suggests that the chemosensory behavior of a deep-sea urchin may be impaired by ocean acidification.

  4. 10Be in marine sediments: applications in geophysics and palaeo-oceanography

    International Nuclear Information System (INIS)

    Henken-Mellies, W.U.

    1990-01-01

    Two problems are investigated in this study: 1. Cosmogenic isotopes (such as 10 Be) are produced by nuclear reactions of cosmic rays with atoms of the earth's atmosphere and uppermost lithosphere. Due to the shielding effect of the earth's magnetic field against cosmic rays the production of cosmogenic nuclides is inversely related to the geomagnetic field intensity. During geomagnetic reversals, when the field intensity is strongly reduced, the production of cosmogenic isotopes should increase. There is no unambiguous evidence yet, whether this increase is reflected in higher concentrations of 10 Be at reversal horizons in deep sea sediments. This relationship is analysed in detail across four magnetic reversals. 2. The influence of climatic and paleographic factors on the distribution of 10 Be in the ocean is as yet only poorly known. 10 Be profiles in deep sea sediments spanning several climatic cycles are used to evaluate the influence of the Quaternary climatic cycles on the distribution of 10 Be in oceanic sediments. (author) figs., tabs., refs

  5. The role of ocean currents for carbonate platform stratigraphy (Invited)

    Science.gov (United States)

    Betzler, C.; Lindhorst, S.; Luedmann, T.; Eberli, G. P.; Reijmer, J.; Huebscher, C. P.

    2013-12-01

    Breaks and turnovers in carbonate bank growth and development record fluctuations in sea-level and environmental changes. For the carbonate banks of the Bahamas, the Maldives, the Queensland, and the Marion Plateau, sea-level changes and synchronous oceanographic and atmospheric circulation events were recorded through compositional and architectural changes. Most of these major carbonate edifices contain drift deposits, indicating that oceanic currents were a major driver of carbonate-bank evolution. It is proposed that such currents have a larger imprint on the growth patterns and the stratigraphic packaging of carbonates than previously thought. In the Bahamas, slope facies of carbonate banks exposed to deep oceanic currents are not arranged into sediment-texture controlled and depth-dependant strike-continuous facies belts. Facies patterns are controlled by the interplay of shallow-water input, succeeding sediment sorting as well as redistribution and erosion processes. This complements the classical windward - leeward classification of carbonate platform slopes and accounts for the significant and potentially dominant process of alongslope sediment transport and dispersal. Deep oceanic currents also have the potential to steepen the carbonate bank slopes, through sediment winnowing at the distal slope, such as for example in the Maldives. This process can be enhanced as the bank grows and expands in size which may accelerate currents. Oceanic current onset or amplification, however, may also account for slope steepening as an externally, i.e. climate-driven agent, thus forcing the banks into an aggradation mode of growth which is not a response to sea-level fluctuations or a result of the windward / leeward exposure of the bank edge. Ignorance of the impact of currents on platforms and platform slopes may lead to an erroneous conclusion that changes in sediment production, distribution, and morphologies of sediment bodies are features solely related to sea

  6. Southern Ocean Circulation: a High Resolution Examination of the Last Deglaciation from Deep-Sea Corals

    Science.gov (United States)

    Robinson, L. F.; Li, T.; Chen, T.; Burke, A.; Pegrum Haram, A.; Stewart, J.; Rae, J. W. B.; van de Flierdt, T.; Struve, T.; Wilson, D. J.

    2017-12-01

    Two decades ago it was first noted that the skeletal remains of deep-sea corals had the potential to provide absolutely dated archives of past ocean conditions. In the intervening twenty years this field has developed to the point where strategic collections and high throughput dating techniques now allow high resolution, well dated records of past deep sea behaviour to be produced. Likewise, efforts to improve understanding of biomineralisation and growth rates are leading to refinements in proxy tools useful for examining circulation, nutrient and carbon cycling, temperature and weathering processes. Deep-sea corals are particularly valuable archives in high latitude regions where radiocarbon-based age models are susceptible to large changes in surface reservoir ages. In this presentation we show new high resolution multiproxy records of the Southern Ocean (Drake Passage) made on U-Th dated corals spanning the last glacial cycle. With more than seventeen hundred reconnaissance ages, and around 200 precise isotope dilution U-Th ages, subtle changes in ocean behaviour can be identified during times of abrupt climate change. The geochemical signature of corals from the deepest sites, closest to modern day Lower Circumpolar Deep Waters, typically show a gradual shift from glacial to Holocene values during deglaciation, likely related to ventilation of the deep ocean. By contrast for the samples collected shallower in the water column (within sites currently bathed by Upper Circumpolar Deep Waters and Antarctic Intermediate and Mode Waters) the evidence points to a more complicated picture. Vertical zonation in the geochemical data suggests that periods of stratification are interspersed with mixing events within the upper 1500m of the water column. At the same time comparison to U-Th dated records from the low latitude Pacific and Atlantic points to an important role for the Southern Ocean in feeding the intermediate waters of both ocean basins throughout the

  7. A feasibility study of the disposal of radioactive waste in deep ocean sediments by drilled emplacement: 1. A review of alternatives

    International Nuclear Information System (INIS)

    1983-01-01

    This report describes the first stage of an engineering study of the disposal of high level radioactive waste in holes formed deep in the ocean floor. In this phase, the emphasis has been on establishing reference criteria, assessing the problems and evaluating potential solutions. The report concludes that there are no aspects that appear technically infeasible, but questions of safety and reliability of certain aspects require further investigation. (author)

  8. A numerical study on oceanic dispersion and sedimentation of radioactive cesium-137 from Fukushima Daiichi Nuclear Power Plant

    International Nuclear Information System (INIS)

    Higashi, Hironori; Morino, Yu; Ohara, Toshimasa

    2014-01-01

    We discussed a numerical model for oceanic dispersion and sedimentation of radioactive cesium-137 (Cs-137) in shallow water regions to clarify migration behavior of Cs-137 from Fukushima Daiichi Nuclear Power Plant. Our model considered oceanic transport by three dimensional ocean current, adsorption with large particulate matter (LPM), sedimentation and resuspension. The simulation well reproduced the spatial characteristics of sea surface concentration and sediment surface concentration of Cs-137 off Miyagi, Fukushima, and Ibaraki Prefectures during May-December 2011. The simulated results indicated that the adsorption-sedimentation of Cs-137 significantly occurred during strong wind events because the large amount of LPM was transported to upward layer by resuspension and vertical mixing. (author)

  9. Late quaternary palaeo-oceanography and palaeo-climatology from sediment cores of the eastern Arctic Ocean

    International Nuclear Information System (INIS)

    Pagels, U.; Koehler, S.

    1991-01-01

    Box cores recovered along a N-S transect in the Eurasian Basin allow the establishment of a time scale for the Late Quaternary history of the Arctic Ocean, based on stable oxygen isotope stratigraphy and AMS 14 C dating of planktonic foraminifers (N. pachyderma I.c.). This high resolution stratigraphy, in combination with sedimentological investigations (e.g. coarse fraction analysis, carbonate content, productivity of foraminifers), was carried out to reconstruct the glacial and inter-glacial Arctic Ocean palaeo-environment The sediment cores, which can be correlated throughout the sampling area in the Eastern Arctic Ocean, were dated as representing oxygen isotope stages 1 to 4/5. The sedimentation rates varied between a few mm/ka in glacials and approximately one cm/ka during the Holocene. The sediments allow a detailed sedimentological description of the depositional regime and the palaeo-oceanography of the Eastern Arctic Ocean. Changing ratios of biogenic and lithogenic components in the sediments reflect variations in the oceanographic circulation pattern in the Eurasian Basin during the Late Quaternary. Carbonate content (1-9wt.%), productivity of foraminifers (high in interglacial, low in glacial stages) and the terrigenous components are in good correlation with glacial and inter-glacial climatic fluctuations

  10. Creep of ocean sediments resulting from the isolation of radioactive wastes

    International Nuclear Information System (INIS)

    Dawson, P.R.; Chavez, P.F.; Lipkin, J.; Silva, A.J.

    1983-01-01

    Long-term disposal of high-level radioactive wastes in subseabed sediments requires that the sediments constitute the principal barrier to the release of radionuclides over very long times. In this chapter the development of the components for mathematical modelling of creep deformations of marine sediments is presented. This development includes formulation of the conservation equations and constitutive equations that describe coupled movement and heating of the fully saturated porous sediments. Numerical methods for solving the system of governing equations for complicated two-dimensional geometrics are discussed, and the program of laboratory tests for understanding the mechanical behavior of the ocean sediments is presented. Using properties taken from published literature on the creep of clays, two problems were analyzed to obtain preliminary estimates of the behavior. Analysis of cavity closure following emplacement showed that the sediment would flow around the canister before heating would significantly alter the temperature field. Large-scale motion caused by density gradients in the sediment was predicted to be small

  11. Science Potential of a Deep Ocean Antineutrino Observatory

    International Nuclear Information System (INIS)

    Dye, S.T.

    2007-01-01

    This paper presents science potential of a deep ocean antineutrino observatory being developed at Hawaii. The observatory design allows for relocation from one site to another. Positioning the observatory some 60 km distant from a nuclear reactor complex enables precision measurement of neutrino mixing parameters, leading to a determination of neutrino mass hierarchy and θ 13 . At a mid-Pacific location the observatory measures the flux and ratio of uranium and thorium decay neutrinos from earth's mantle and performs a sensitive search for a hypothetical natural fission reactor in earth's core. A subsequent deployment at another mid-ocean location would test lateral heterogeneity of uranium and thorium in earth's mantle

  12. The stable carbon isotope biogeochemistry of acetate and other dissolved carbon species in deep subseafloor sediments at the northern Cascadia Margin

    Science.gov (United States)

    Heuer, Verena B.; Pohlman, John W.; Torres, Marta E.; Elvert, Marcus; Hinrichs, Kai-Uwe

    2009-01-01

    Ocean drilling has revealed the existence of vast microbial populations in the deep subseafloor, but to date little is known about their metabolic activities. To better understand the biogeochemical processes in the deep biosphere, we investigate the stable carbon isotope chemistry of acetate and other carbon-bearing metabolites in sediment pore-waters. Acetate is a key metabolite in the cycling of carbon in anoxic sediments. Its stable carbon isotopic composition provides information on the metabolic processes dominating acetate turnover in situ. This study reports our findings for a methane-rich site at the northern Cascadia Margin (NE Pacific) where Expedition 311 of the Integrated Ocean Drilling Program (IODP) sampled the upper 190 m of sediment. At Site U1329, δ13C values of acetate span a wide range from −46.0‰ to −11.0‰ vs. VPDB and change systematically with sediment depth. In contrast, δ13C values of both the bulk dissolved organic carbon (DOC) (−21.6 ± 1.3‰ vs. VPDB) and the low-molecular-weight compound lactate (−20.9 ± 1.8‰ vs. VPDB) show little variability. These species are interpreted to represent the carbon isotopic composition of fermentation products. Relative to DOC, acetate is up to 23.1‰ depleted and up to 9.1‰ enriched in 13C. Broadly, 13C-depletions of acetate relative to DOC indicate flux of carbon from acetogenesis into the acetate pool while 13C-enrichments of pore-water acetate relative to DOC suggest consumption of acetate by acetoclastic methanogenesis. Isotopic relationships between acetate and lactate or DOC provide new information on the carbon flow and the presence and activity of specific functional microbial communities in distinct biogeochemical horizons of the sediment. In particular, they suggest that acetogenic CO2-reduction can coexist with methanogenic CO2-reduction, a notion contrary to the hypothesis that hydrogen levels are controlled by the thermodynamically most favorable electron

  13. Subduction recycling of continental sediments and the origin of geochemically enriched reservoirs in the deep mantle

    Energy Technology Data Exchange (ETDEWEB)

    Rapp, R.P.; Irifune, T.; Shimizu, N.; Nishiyama, N.; Norman, M.D.; Inoue, T. (Ehime U); (WHOI); (UC); (ANU)

    2008-10-08

    Isotopic and trace element geochemical studies of ocean island basalts (OIBs) have for many years been used to infer the presence of long-lived ({approx} 1-2 Ga old) compositional heterogeneities in the deep mantle related to recycling of crustal lithologies and marine and terrigenous sediments via subduction [e.g., Zindler, A., Hart, S.R., 1986. Chemical geodynamics. Annu. Rev. Earth Planet. Sci. 14, 493-571; Weaver, B.L., 1991. The origin of ocean island basalt end-member compositions: trace element and isotopic constraints. Earth Planet. Sci. Lett. 104, 381-397; Chauvel, C., Hofmann, A.W., Vidal, P., 1992. HIMU-EM: the French Polynesian connection. Earth Planet. Sci. Lett. 110, 99-119; Hofmann, A.W., 1997. Mantle geochemistry: the message from oceanic volcanism. Nature 385, 219-229; Willbold, M., Stracke, A., 2006. Trace element composition of mantle end-members: Implications for recycling of oceanic and upper and lower continental crust. Geochem. Geophys. Geosyst. Q04004. 7, doi:10.1029/2005GC001005]. In particular, models for the EM-1 type ('enriched mantle') OIB reservoir have invoked the presence of subducted, continental-derived sediment to explain high {sup 87}Sr/{sup 86}Sr ratios, low {sup 143}Nd/{sup 144}Nd and {sup 206}Pb/{sup 204}Pb ratios, and extreme enrichments in incompatible elements observed in OIB lavas from, for example, the Pitcairn Island group in the South Pacific [Woodhead, J.D., McCulloch, M.T., 1989; Woodhead, J.D., Devey, C.W., 1993. Geochemistry of the Pitcairn seamounts, I: source character and temporal trends. Earth Planet. Sci. Lett. 116, 81-99; Eisele, J., Sharma, M., Galer, S.J.G., Blichert-Toft, J., Devey, C.W., Hofmann, A.W., 2002. The role of sediment recycling in EM-1 inferred from Os, Pb, Hf, Nd, Sr isotope and trace element systematics of the Pitcairn hotspot. Earth Planet. Sci. Lett. 196, 197-212]. More recently, ultrapotassic, mantle-derived lavas (lamproites) from Gaussberg, Antarctica have been interpreted as

  14. Deep-Sea, Deep-Sequencing: Metabarcoding Extracellular DNA from Sediments of Marine Canyons.

    Directory of Open Access Journals (Sweden)

    Magdalena Guardiola

    Full Text Available Marine sediments are home to one of the richest species pools on Earth, but logistics and a dearth of taxonomic work-force hinders the knowledge of their biodiversity. We characterized α- and β-diversity of deep-sea assemblages from submarine canyons in the western Mediterranean using an environmental DNA metabarcoding. We used a new primer set targeting a short eukaryotic 18S sequence (ca. 110 bp. We applied a protocol designed to obtain extractions enriched in extracellular DNA from replicated sediment corers. With this strategy we captured information from DNA (local or deposited from the water column that persists adsorbed to inorganic particles and buffered short-term spatial and temporal heterogeneity. We analysed replicated samples from 20 localities including 2 deep-sea canyons, 1 shallower canal, and two open slopes (depth range 100-2,250 m. We identified 1,629 MOTUs, among which the dominant groups were Metazoa (with representatives of 19 phyla, Alveolata, Stramenopiles, and Rhizaria. There was a marked small-scale heterogeneity as shown by differences in replicates within corers and within localities. The spatial variability between canyons was significant, as was the depth component in one of the canyons where it was tested. Likewise, the composition of the first layer (1 cm of sediment was significantly different from deeper layers. We found that qualitative (presence-absence and quantitative (relative number of reads data showed consistent trends of differentiation between samples and geographic areas. The subset of exclusively benthic MOTUs showed similar patterns of β-diversity and community structure as the whole dataset. Separate analyses of the main metazoan phyla (in number of MOTUs showed some differences in distribution attributable to different lifestyles. Our results highlight the differentiation that can be found even between geographically close assemblages, and sets the ground for future monitoring and conservation

  15. Sediments in Arctic sea ice: Implications for entrainment, transport and release

    Science.gov (United States)

    Nurnberg, D.; Wollenburg, I.; Dethleff, D.; Eicken, H.; Kassens, H.; Letzig, T.; Reimnitz, E.; Thiede, Jorn

    1994-01-01

    maximum in sea ice sediment samples repeatedly occurred between 81??N and 83??N along the Arctic 91 transect, indicating a rather stable and narrow smectite rich ice drift stream of the Transpolar Drift. The smectite concentrations are comparable to those found in both Laptev Sea shelf sediments and anchor ice sediments, pointing to this sea as a potential source area for sea ice sediments. In the central Arctic Ocean sea ice clay mineralogy is significantly different from deep-sea clay mineral distribution patterns. The contribution of sea ice sediments to the deep sea is apparently diluted by sedimentary material provided by other transport mechanisms. ?? 1994.

  16. Viruses-to-mobile genetic elements skew in the deep Atlantis II brine pool sediments

    KAUST Repository

    Adel, Mustafa

    2016-09-06

    The central rift of the Red Sea has 25 brine pools with different physical and geochemical characteristics. Atlantis II (ATIID), Discovery Deeps (DD) and Chain Deep (CD) are characterized by high salinity, temperature and metal content. Several studies reported microbial communities in these brine pools, but few studies addressed the brine pool sediments. Therefore, sediment cores were collected from ATIID, DD, CD brine pools and an adjacent brine-influenced site. Sixteen different lithologic sediment sections were subjected to shotgun DNA pyrosequencing to generate 1.47 billion base pairs (1.47 × 109 bp). We generated sediment-specific reads and attempted to annotate all reads. We report the phylogenetic and biochemical uniqueness of the deepest ATIID sulfur-rich brine pool sediments. In contrary to all other sediment sections, bacteria dominate the deepest ATIID sulfur-rich brine pool sediments. This decrease in virus-to-bacteria ratio in selected sections and depth coincided with an overrepresentation of mobile genetic elements. Skewing in the composition of viruses-to-mobile genetic elements may uniquely contribute to the distinct microbial consortium in sediments in proximity to hydrothermally active vents of the Red Sea and possibly in their surroundings, through differential horizontal gene transfer.

  17. Spiraling pathways of global deep waters to the surface of the Southern Ocean

    OpenAIRE

    Tamsitt, Veronica; Drake, Henri F.; Morrison, Adele K.; Talley, Lynne D.; Dufour, Carolina O.; Gray, Alison R.; Griffies, Stephen M.; Mazloff, Matthew R.; Sarmiento, Jorge L.; Wang, Jinbo; Weijer, Wilbert

    2017-01-01

    Upwelling of global deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. However, the exact pathways and role of topography in Southern Ocean upwelling remain largely unknown. Here we show detailed upwelling pathways in three dimensions, using hydrographic observations and particle trac...

  18. Rare earth element and neodymium isotope tracing of element input and past ocean circulation. Study from north and south pacific seawater and sediments

    Energy Technology Data Exchange (ETDEWEB)

    Froellje, Henning

    2016-08-09

    Hawaiian Islands on coastal waters and the open ocean at Station ALOHA (chapter 2). These results indicate that contributions from volcanic islands (e.g., Hawaii) cannot be disregarded when investigating element budgets in the North Pacific. It is further shown that seasonal variability of Asian dust input most likely has significant influence on the Nd isotope signature of central North Pacific surface waters. New results from measurements of colloidal and truly dissolved REE concentrations indicate for the first time the absence of colloidal-bound REEs in open ocean waters at different depths. Further, a complete water column profile from Station ALOHA allows tracing of North Pacific water masses based on Nd isotopes. This study presents an adjustment of the Nd isotope signature and Nd concentration of North Pacific Deep Water (NPDW), which is considered the radiogenic endmember in the global overturning circulation, and therefore of particular importance for paleoceanographic studies. Moreover, REE patterns demonstrate that vertical processes overprint the REE concentrations in deep and bottom waters, precluding their use to trace water masses in the deep Pacific. Sedimentary Nd isotopes from the last 30,000 years demonstrate the variability in water mass structure in the South Pacific and the evolution of water mass mixing in Circumpolar Deep Water (CDW) during the last glacial-interglacial transition (chapter 3). Combined results from five sediment cores show an expansion of glacial bottom water and its isolation from CDW during the Last Glacial Maximum (LGM) based on differences in the Nd isotope signatures in cores below and above ∝4000 m. Admixture of bottom water into CDW during the early deglaciation is suggested based on the early deglacial decrease of Nd isotope signatures in CDW-bathed cores before the re-strengthening of North Atlantic Deep Water (NADW) advection. This is related to Southern Hemisphere climate and only later during the deglaciation did the

  19. Rare earth element and neodymium isotope tracing of element input and past ocean circulation. Study from north and south pacific seawater and sediments

    International Nuclear Information System (INIS)

    Froellje, Henning

    2016-01-01

    Hawaiian Islands on coastal waters and the open ocean at Station ALOHA (chapter 2). These results indicate that contributions from volcanic islands (e.g., Hawaii) cannot be disregarded when investigating element budgets in the North Pacific. It is further shown that seasonal variability of Asian dust input most likely has significant influence on the Nd isotope signature of central North Pacific surface waters. New results from measurements of colloidal and truly dissolved REE concentrations indicate for the first time the absence of colloidal-bound REEs in open ocean waters at different depths. Further, a complete water column profile from Station ALOHA allows tracing of North Pacific water masses based on Nd isotopes. This study presents an adjustment of the Nd isotope signature and Nd concentration of North Pacific Deep Water (NPDW), which is considered the radiogenic endmember in the global overturning circulation, and therefore of particular importance for paleoceanographic studies. Moreover, REE patterns demonstrate that vertical processes overprint the REE concentrations in deep and bottom waters, precluding their use to trace water masses in the deep Pacific. Sedimentary Nd isotopes from the last 30,000 years demonstrate the variability in water mass structure in the South Pacific and the evolution of water mass mixing in Circumpolar Deep Water (CDW) during the last glacial-interglacial transition (chapter 3). Combined results from five sediment cores show an expansion of glacial bottom water and its isolation from CDW during the Last Glacial Maximum (LGM) based on differences in the Nd isotope signatures in cores below and above ∝4000 m. Admixture of bottom water into CDW during the early deglaciation is suggested based on the early deglacial decrease of Nd isotope signatures in CDW-bathed cores before the re-strengthening of North Atlantic Deep Water (NADW) advection. This is related to Southern Hemisphere climate and only later during the deglaciation did the

  20. Science Potential of a Deep Ocean Antineutrino Observatory

    Energy Technology Data Exchange (ETDEWEB)

    Dye, S.T. [Department of Physics and Astronomy, University of Hawaii, 2505 Correa Road, Honolulu, Hawaii, 96822 (United States); College of Natural Sciences, Hawaii Pacific University, 45-045 Kamehameha Highway, Kaneohe, Hawaii 96744 (United States)

    2007-06-15

    This paper presents science potential of a deep ocean antineutrino observatory being developed at Hawaii. The observatory design allows for relocation from one site to another. Positioning the observatory some 60 km distant from a nuclear reactor complex enables precision measurement of neutrino mixing parameters, leading to a determination of neutrino mass hierarchy and {theta}{sub 13}. At a mid-Pacific location the observatory measures the flux and ratio of uranium and thorium decay neutrinos from earth's mantle and performs a sensitive search for a hypothetical natural fission reactor in earth's core. A subsequent deployment at another mid-ocean location would test lateral heterogeneity of uranium and thorium in earth's mantle.

  1. On the assimilation of absolute geodetic dynamic topography in a global ocean model: impact on the deep ocean state

    Science.gov (United States)

    Androsov, Alexey; Nerger, Lars; Schnur, Reiner; Schröter, Jens; Albertella, Alberta; Rummel, Reiner; Savcenko, Roman; Bosch, Wolfgang; Skachko, Sergey; Danilov, Sergey

    2018-05-01

    General ocean circulation models are not perfect. Forced with observed atmospheric fluxes they gradually drift away from measured distributions of temperature and salinity. We suggest data assimilation of absolute dynamical ocean topography (DOT) observed from space geodetic missions as an option to reduce these differences. Sea surface information of DOT is transferred into the deep ocean by defining the analysed ocean state as a weighted average of an ensemble of fully consistent model solutions using an error-subspace ensemble Kalman filter technique. Success of the technique is demonstrated by assimilation into a global configuration of the ocean circulation model FESOM over 1 year. The dynamic ocean topography data are obtained from a combination of multi-satellite altimetry and geoid measurements. The assimilation result is assessed using independent temperature and salinity analysis derived from profiling buoys of the AGRO float data set. The largest impact of the assimilation occurs at the first few analysis steps where both the model ocean topography and the steric height (i.e. temperature and salinity) are improved. The continued data assimilation over 1 year further improves the model state gradually. Deep ocean fields quickly adjust in a sustained manner: A model forecast initialized from the model state estimated by the data assimilation after only 1 month shows that improvements induced by the data assimilation remain in the model state for a long time. Even after 11 months, the modelled ocean topography and temperature fields show smaller errors than the model forecast without any data assimilation.

  2. Metagenomic Signatures of Microbial Communities in Deep-Sea Hydrothermal Sediments of Azores Vent Fields.

    Science.gov (United States)

    Cerqueira, Teresa; Barroso, Cristina; Froufe, Hugo; Egas, Conceição; Bettencourt, Raul

    2018-01-21

    The organisms inhabiting the deep-seafloor are known to play a crucial role in global biogeochemical cycles. Chemolithoautotrophic prokaryotes, which produce biomass from single carbon molecules, constitute the primary source of nutrition for the higher organisms, being critical for the sustainability of food webs and overall life in the deep-sea hydrothermal ecosystems. The present study investigates the metabolic profiles of chemolithoautotrophs inhabiting the sediments of Menez Gwen and Rainbow deep-sea vent fields, in the Mid-Atlantic Ridge. Differences in the microbial community structure might be reflecting the distinct depth, geology, and distance from vent of the studied sediments. A metagenomic sequencing approach was conducted to characterize the microbiome of the deep-sea hydrothermal sediments and the relevant metabolic pathways used by microbes. Both Menez Gwen and Rainbow metagenomes contained a significant number of genes involved in carbon fixation, revealing the largely autotrophic communities thriving in both sites. Carbon fixation at Menez Gwen site was predicted to occur mainly via the reductive tricarboxylic acid cycle, likely reflecting the dominance of sulfur-oxidizing Epsilonproteobacteria at this site, while different autotrophic pathways were identified at Rainbow site, in particular the Calvin-Benson-Bassham cycle. Chemolithotrophy appeared to be primarily driven by the oxidation of reduced sulfur compounds, whether through the SOX-dependent pathway at Menez Gwen site or through reverse sulfate reduction at Rainbow site. Other energy-yielding processes, such as methane, nitrite, or ammonia oxidation, were also detected but presumably contributing less to chemolithoautotrophy. This work furthers our knowledge of the microbial ecology of deep-sea hydrothermal sediments and represents an important repository of novel genes with potential biotechnological interest.

  3. Biostratigraphic analysis of the top layer of sediment cores from the reference and test sites of the INDEX area

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, S.M.

    Radiolarian fossil study in the sediment cores collected during the pre- and postdisturbance cruises of the Environmental Impact Assessment (EIA) Indian Ocean Experiment (INDEX) program of deep sea mining in the Central Indian Ocean Basin suggests a...

  4. Piracicaba River Basin: evaluation of chemical elements in deep sediment profile by INAA

    Energy Technology Data Exchange (ETDEWEB)

    França, Elvis J. de; Santos, Robson A.; Santos, Katarine M. Barbosa; Silva, Gleyce K. A. [Centro Regional de Ciencias Nucleares do Nordeste (DIAMB/CRCN-NE/CNEN-PE), Recife, PE (Brazil). Div, de Monitoração Ambiental; Fernandes, Elisabete A. de Nadai; Rodrigues, Vanessa S.; Cavalca, Isabel P.O., E-mail: ejfranca@cnen.gov.br, E-mail: lis@cena.usp.br [Centro de Energia Nuclear na Agricultura (CENA/USP), Piracicaba, SP (Brazil)

    2017-07-01

    Many hydrographic basins have been impacted by anthropogenic sources, the Piracicaba River Basin of the State of São Paulo, is one of that. The total concentrations of chemical elements in deep sediments of basin may be indicate those available in ecosystem. Therefore, in this research concentration of chemical elements on deep sediment profile sampled of Piracicaba River Basin was determined by k0-Instrumental Neutron Activation Analysis. After collecting the 60 cm depth profile, samples were obtained by sectioning the sediment profile in 5 cm layers, totalizing 12 samples. Analytical portions were transferred to polyethylene vials for neutron irradiation at the Nuclear Research Reactor IEA-R1 from the Instituto de Pesquisas Energéticas e Nucleares IPEN/CNEN. After waiting for radiation safe levels, irradiated samples were transported to the Radioisotopes Laboratory from the Centro de Energia Nuclear na Agricultura CENA/USP. High Resolution Gamma-Ray Spectrometry using HPGe detectors was applied to measure the induced radioactivity. The chemical element mass fractions and their respective expanded analytical uncertainties (95% confidence level) were determined by k0-INAA using the in-house software Quantu. Geological reference materials were analyzed with samples to evaluate the quality of the analytical procedure. Results indicated the presence of enriched surface sediments (0-10 cm depth) for As, Ba, Ca, Co, Cs, Fe, Sb, Sc, Sr, Yb and Zn, despite no alteration was observed for Eu, Ta and Tb. Therefore, the evaluation of deep sediment profile afford the chemical element dynamics for the Piracicaba Basin. (author)

  5. Piracicaba River Basin: evaluation of chemical elements in deep sediment profile by INAA

    International Nuclear Information System (INIS)

    França, Elvis J. de; Santos, Robson A.; Santos, Katarine M. Barbosa; Silva, Gleyce K. A.

    2017-01-01

    Many hydrographic basins have been impacted by anthropogenic sources, the Piracicaba River Basin of the State of São Paulo, is one of that. The total concentrations of chemical elements in deep sediments of basin may be indicate those available in ecosystem. Therefore, in this research concentration of chemical elements on deep sediment profile sampled of Piracicaba River Basin was determined by k0-Instrumental Neutron Activation Analysis. After collecting the 60 cm depth profile, samples were obtained by sectioning the sediment profile in 5 cm layers, totalizing 12 samples. Analytical portions were transferred to polyethylene vials for neutron irradiation at the Nuclear Research Reactor IEA-R1 from the Instituto de Pesquisas Energéticas e Nucleares IPEN/CNEN. After waiting for radiation safe levels, irradiated samples were transported to the Radioisotopes Laboratory from the Centro de Energia Nuclear na Agricultura CENA/USP. High Resolution Gamma-Ray Spectrometry using HPGe detectors was applied to measure the induced radioactivity. The chemical element mass fractions and their respective expanded analytical uncertainties (95% confidence level) were determined by k0-INAA using the in-house software Quantu. Geological reference materials were analyzed with samples to evaluate the quality of the analytical procedure. Results indicated the presence of enriched surface sediments (0-10 cm depth) for As, Ba, Ca, Co, Cs, Fe, Sb, Sc, Sr, Yb and Zn, despite no alteration was observed for Eu, Ta and Tb. Therefore, the evaluation of deep sediment profile afford the chemical element dynamics for the Piracicaba Basin. (author)

  6. The effects of natural iron fertilisation on deep-sea ecology: the Crozet Plateau, Southern Indian Ocean.

    Directory of Open Access Journals (Sweden)

    George A Wolff

    Full Text Available The addition of iron to high-nutrient low-chlorophyll (HNLC oceanic waters stimulates phytoplankton, leading to greater primary production. Large-scale artificial ocean iron fertilization (OIF has been proposed as a means of mitigating anthropogenic atmospheric CO(2, but its impacts on ocean ecosystems below the photic zone are unknown. Natural OIF, through the addition of iron leached from volcanic islands, has been shown to enhance primary productivity and carbon export and so can be used to study the effects of OIF on life in the ocean. We compared two closely-located deep-sea sites (∼400 km apart and both at ∼4200 m water depth to the East (naturally iron fertilized; +Fe and South (HNLC of the Crozet Islands in the southern Indian Ocean. Our results suggest that long-term geo-engineering of surface oceanic waters via artificial OIF would lead to significant changes in deep-sea ecosystems. We found that the +Fe area had greater supplies of organic matter inputs to the seafloor, including polyunsaturated fatty acid and carotenoid nutrients. The +Fe site also had greater densities and biomasses of large deep-sea animals with lower levels of evenness in community structuring. The species composition was also very different, with the +Fe site showing similarities to eutrophic sites in other ocean basins. Moreover, major differences occurred in the taxa at the +Fe and HNLC sites revealing the crucial role that surface oceanic conditions play in changing and structuring deep-sea benthic communities.

  7. Ocean anoxia and the concentrations of molybdenum and vanadium in seawater

    International Nuclear Information System (INIS)

    Emerson, S.R.; Huested, S.S.

    1991-01-01

    Molybdenum and vanadium are relatively unreactive in seawater and are preferentially concentrated in sediments overlain by anoxic or near-anoxic water. The geochemistry of these metals is investigated by interpreting measurements from anoxic basins and sediment porewater. The concentrations of Mo and V in the water column of anoxic basins are usually lower than in oxic seawater because of uptake into highly anoxic sediments. The mechanism of removal from solution appears to be diffusion across the sediment-water interface and immobilization within the sediments. Measurements from open ocean porewater imply fluxes of vanadium from sediments that are greater than 10 times the dissolved and particulate river inflow, which is consistent with the distribution of vanadium in deep waters of the ocean and previous geochemical studies; this inconsistency shows that early diagenesis of this element is poorly understood. The authors estimate that the area of ocean sediment at present overlain by anoxic and near-anoxic water is accumulating 25±15% and 8±5% of the river influx of Mo and V, respectively. This fraction is 17±10% for uranium, which has been shown to share some of the redox behavior of Mo and V. A case is made that changes in the concentrations of these elements in the ocean should be sensitive indicators of the portion of the ocean bottom overlain by anoxic seawater through geologic time. (author). 65 refs.; 3 figs.; 5 tabs

  8. Fungal diversity in deep-sea sediments of a hydrothermal vent system in the Southwest Indian Ridge

    Science.gov (United States)

    Xu, Wei; Gong, Lin-feng; Pang, Ka-Lai; Luo, Zhu-Hua

    2018-01-01

    Deep-sea hydrothermal sediment is known to support remarkably diverse microbial consortia. In deep sea environments, fungal communities remain less studied despite their known taxonomic and functional diversity. High-throughput sequencing methods have augmented our capacity to assess eukaryotic diversity and their functions in microbial ecology. Here we provide the first description of the fungal community diversity found in deep sea sediments collected at the Southwest Indian Ridge (SWIR) using culture-dependent and high-throughput sequencing approaches. A total of 138 fungal isolates were cultured from seven different sediment samples using various nutrient media, and these isolates were identified to 14 fungal taxa, including 11 Ascomycota taxa (7 genera) and 3 Basidiomycota taxa (2 genera) based on internal transcribed spacers (ITS1, ITS2 and 5.8S) of rDNA. Using illumina HiSeq sequencing, a total of 757,467 fungal ITS2 tags were recovered from the samples and clustered into 723 operational taxonomic units (OTUs) belonging to 79 taxa (Ascomycota and Basidiomycota contributed to 99% of all samples) based on 97% sequence similarity. Results from both approaches suggest that there is a high fungal diversity in the deep-sea sediments collected in the SWIR and fungal communities were shown to be slightly different by location, although all were collected from adjacent sites at the SWIR. This study provides baseline data of the fungal diversity and biogeography, and a glimpse to the microbial ecology associated with the deep-sea sediments of the hydrothermal vent system of the Southwest Indian Ridge.

  9. Can we constrain postglacial sedimentation in the western Arctic Ocean by ramped pyrolysis 14C? A case study from the Chukchi-Alaskan margin.

    Science.gov (United States)

    Suzuki, K.; Yamamoto, M.; Rosenheim, B. E.; Omori, T.; Polyak, L.; Nam, S. I.

    2017-12-01

    The Arctic Ocean underwent dramatic climate changes in the past. Variations in sea-ice extent and ocean current system in the Arctic cause changes in surface albedo and deep water formation, which have global climatic implications. However, Arctic paleoceanographic studies are lagging behind the other oceans due largely to chronostratigraphic difficulties. One of the reasons for this is a scant presence of material suitable for 14C dating in large areas of the Arctic seafloor. To enable improved age constraints for sediments impoverished in datable material, we apply ramped pyrolysis 14C method (Ramped PyrOx 14C, Rosenheim et al., 2008) to sedimentary records from the Chukchi-Alaska margin recovering Holocene to late-glacial deposits. Samples were divided into five fraction products by gradual heating sedimentary organic carbon from ambient laboratory temperature to 1000°C. The thermographs show a trimodal pattern of organic matter decomposition over temperature, and we consider that CO2 generated at the lowest temperature range was derived from autochthonous organic carbon contemporaneous with sediment deposition, similar to studies in the Antarctic margin and elsewhere. For verification of results, some of the samples treated for ramped pyrolysis 14C were taken from intervals dated earlier by AMS 14C using bivalve mollusks. Ultimately, our results allow a new appraisal of deglacial to Holocene deposition at the Chukchi-Alaska margin with potential to be applied to other regions of the Arctic Ocean.

  10. Deep-Sea Bioluminescence Blooms after Dense Water Formation at the Ocean Surface

    NARCIS (Netherlands)

    Tamburini, C.; Canals, M.; de Madron, X.D.; Houpert, L.; Lefevre, D.; Martini, V.; D'Ortenzio, F.; Robert, A.; Testor, P.; Aguilar, J.A.; Al Samarai, I.; Albert, A.; Andre, M.; Anghinolfi, M.; Anton, G.; Anvar, S.; Ardid, M.; Jesus, A.C.A.; Astraatmadja, T.L.; Aubert, J.J.; Baret, B.; Basa, S.; Bertin, V.; Biagi, S.; Bigi, A.; Bigongiari, C.; Bogazzi, C.; Bou-Cabo, M.; Bouhou, B.; Bouwhuis, M.C.; Brunner, J.; Busto, J.; Camarena, F.; Capone, A.; Carloganu, C.; Carminati, G.; Carr, J.; Cecchini, S.; Charif, Z.; Charvis, P.; Chiarusi, T.; Circella, M.; Coniglione, R.; Costantini, H.; Coyle, P.; Curtil, C.; Decowski, P.; Dekeyser, I.; Deschamps, A.; Donzaud, C.; Dornic, D.; Dorosti, H.Q.; Drouhin, D.; Eberl, T.; Emanuele, U.; Ernenwein, J.P.; Escoffier, S.; Fermani, P.; Ferri, M.; Flaminio, V.; Folger, F.; Fritsch, U.; Fuda, J.L.; Galata, S.; Gay, P.; Giacomelli, G.; Giordano, V.; Gomez-Gonzalez, J.P.; Graf, K.; Guillard, G.; Halladjian, G.; Hallewell, G.; van Haren, H.; Hartman, J.; Heijboer, A.J.; Hello, Y.; Hernandez-Rey, J.J.; Herold, B.; Hossl, J.; Hsu, C.C.; De Jong, M.; Kadler, M.; Kalekin, O.; Kappes, A.; Katz, U.; Kavatsyuk, O.; Kooijman, P.; Kopper, C.; Kouchner, A.; Kreykenbohm, I.; Kulikovskiy, V.; Lahmann, R.; Lamare, P.; Larosa, G.; Lattuada, D.; Lim, G.; Lo Presti, D.; Loehner, H.; Loucatos, S.; Mangano, S.; Marcelin, M.; Margiotta, A.; Martinez-Mora, J.A.; Meli, A.; Montaruli, T.; Moscoso, L.; Motz, H.; Neff, M.; Nezri, E.N.; Palioselitis, D.; Pavalas, G.E.; Payet, K.; Payre, P.; Petrovic, J.; Piattelli, P.; Picot-Clemente, N.; Popa, V.; Pradier, T.; Presani, E.; Racca, C.; Reed, C.; Riccobene, G.; Richardt, C.; Richter, R.; Riviere, C.; Roensch, K.; Rostovtsev, A.; Ruiz-Rivas, J.; Rujoiu, M.; Russo, V.G.; Salesa, F.; Sanchez-Losa, A.; Sapienza, P.; Schock, F.; Schuller, J.P.; Schussler, F.; Shanidze, R.; Simeone, F.; Spies, A.; Spurio, M.; Steijger, J.J.M.; Stolarczyk, T.; Taiuti, M.G.F.; Toscano, S.; Vallage, B.; Van Elewyck, V.; Vannoni, G.; Vecchi, M.; Vernin, P.; Wijnker, G.; Wilms, J.; de Wolf, E.; Yepes, H.; Zaborov, D.; Zornoza, J.D.; Zuniga, J.

    2013-01-01

    The deep ocean is the largest and least known ecosystem on Earth. It hosts numerous pelagic organisms, most of which are able to emit light. Here we present a unique data set consisting of a 2.5-year long record of light emission by deep-sea pelagic organisms, measured from December 2007 to June

  11. Sediment Monitoring and Benthic Faunal Sampling Adjacent to the Barbers Point Ocean Outfall, Oahu, Hawaii, 1986-2010 (NODC Accession 9900098)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Benthic fauna and sediment in the vicinity of the Barbers Point (Honouliuli) ocean outfall were sampled from 1986-2010. To assess the environmental quality, sediment...

  12. Iron oxide reduction in methane-rich deep Baltic Sea sediments

    DEFF Research Database (Denmark)

    Egger, Matthias; Hagens, Mathilde; Sapart, Celia J.

    2017-01-01

    /L transition. Our results reveal a complex interplay between production, oxidation and transport of methane showing that besides organoclastic Fe reduction, oxidation of downward migrating methane with Fe oxides may also explain the elevated concentrations of dissolved ferrous Fe in deep Baltic Sea sediments...... profiles and numerical modeling, we propose that a potential coupling between Fe oxide reduction and methane oxidation likely affects deep Fe cycling and related biogeochemical processes, such as burial of phosphorus, in systems subject to changes in organic matter loading or bottom water salinity....

  13. LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model v2.0.4

    Directory of Open Access Journals (Sweden)

    R. E. Zeebe

    2012-01-01

    Full Text Available The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. LOSCAR's configuration of ocean geometry is flexible and allows for easy switching between modern and paleo-versions. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

  14. Long-term viability of carbon sequestration in deep-sea sediments

    Science.gov (United States)

    Teng, Y.; Zhang, D.

    2017-12-01

    Sequestration of carbon dioxide in deep-sea sediments has been proposed for the long-term storage of anthropogenic CO2, due to the negative buoyancy effect and hydrate formation under conditions of high pressure and low temperature. However, the multi-physics process of injection and post-injection fate of CO2 and the feasibility of sub-seabed disposal of CO2 under different geological and operational conditions have not been well studied. On the basis of a detailed study of the coupled processes, we investigate whether storing CO2 into deep-sea sediments is viable, efficient, and secure over the long term. Also studied are the evolution of the multiphase and multicomponent flow and the impact of hydrate formation on storage efficiency during the upward migration of the injected CO2. It is shown that low buoyancy and high viscosity slow down the ascending plume and the forming of the hydrate cap effectively reduces the permeability and finally becomes an impermeable seal, thus limiting the movement of CO2 towards the seafloor. Different flow patterns at varied time scales are identified through analyzing the mass distribution of CO2 in different phases over time. Observed is the formation of a fluid inclusion, which mainly consists of liquid CO2 and is encapsulated by an impermeable hydrate film in the diffusion-dominated stage. The trapped liquid CO2 and CO2 hydrate finally dissolve into the pore water through diffusion of the CO2 component. Sensitivity analyses are performed on storage efficiency under variable geological and operational conditions. It is found that under a deep-sea setting, CO2 sequestration in intact marine sediments is generally safe and permanent.

  15. Abrupt pre-Bølling-Allerød warming and circulation changes in the deep ocean.

    Science.gov (United States)

    Thiagarajan, Nivedita; Subhas, Adam V; Southon, John R; Eiler, John M; Adkins, Jess F

    2014-07-03

    Several large and rapid changes in atmospheric temperature and the partial pressure of carbon dioxide in the atmosphere--probably linked to changes in deep ocean circulation--occurred during the last deglaciation. The abrupt temperature rise in the Northern Hemisphere and the restart of the Atlantic meridional overturning circulation at the start of the Bølling-Allerød interstadial, 14,700 years ago, are among the most dramatic deglacial events, but their underlying physical causes are not known. Here we show that the release of heat from warm waters in the deep North Atlantic Ocean probably triggered the Bølling-Allerød warming and reinvigoration of the Atlantic meridional overturning circulation. Our results are based on coupled radiocarbon and uranium-series dates, along with clumped isotope temperature estimates, from water column profiles of fossil deep-sea corals in a limited area of the western North Atlantic. We find that during Heinrich stadial 1 (the cool period immediately before the Bølling-Allerød interstadial), the deep ocean was about three degrees Celsius warmer than shallower waters above. This reversal of the ocean's usual thermal stratification pre-dates the Bølling-Allerød warming and must have been associated with increased salinity at depth to preserve the static stability of the water column. The depleted radiocarbon content of the warm and salty water mass implies a long-term disconnect from rapid surface exchanges, and, although uncertainties remain, is most consistent with a Southern Ocean source. The Heinrich stadial 1 ocean profile is distinct from the modern water column, that for the Last Glacial Maximum and that for the Younger Dryas, suggesting that the patterns we observe are a unique feature of the deglacial climate system. Our observations indicate that the deep ocean influenced dramatic Northern Hemisphere warming by storing heat at depth that preconditioned the system for a subsequent abrupt overturning event during the

  16. Sediment monitoring and benthic faunal sampling adjacent to the Sand Island ocean outfall, Oahu, Hawaii, 1986-2010 (NODC Accession 9900088)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Benthic fauna and sediment in the vicinity of the Sand Island ocean outfall were sampled from 1986-2010. To assess the environmental quality, sediment grain size and...

  17. Early diagenesis of phosphorus in continental margin sediments

    NARCIS (Netherlands)

    Slomp, C.P.

    1997-01-01

    Most of the organic material in the oceans that reaches the sea floor is deposited on continental margins and not in the deep sea. This organic matter is the principal carrier of phosphorus (P) to sediments. A part of the organic material is buried definitely. The other part decomposes,

  18. Extreme diving behaviour in devil rays links surface waters and the deep ocean

    KAUST Repository

    Thorrold, Simon R.

    2014-07-01

    Ecological connections between surface waters and the deep ocean remain poorly studied despite the high biomass of fishes and squids residing at depths beyond the euphotic zone. These animals likely support pelagic food webs containing a suite of predators that include commercially important fishes and marine mammals. Here we deploy pop-up satellite archival transmitting tags on 15 Chilean devil rays (Mobula tarapacana) in the central North Atlantic Ocean, which provide movement patterns of individuals for up to 9 months. Devil rays were considered surface dwellers but our data reveal individuals descending at speeds up to 6.0 ms-1 to depths of almost 2,000 m and water temperatures <4 C. The shape of the dive profiles suggests that the rays are foraging at these depths in deep scattering layers. Our results provide evidence of an important link between predators in the surface ocean and forage species occupying pelagic habitats below the euphotic zone in ocean ecosystems. 2014 Macmillan Publishers Limited. All rights reserved.

  19. Relationship between chemical composition and magnetic susceptibility in sediment cores from Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.; Parthiban, G.; Banakar, V.K.; Tomer, A.; Kulkarni, M.

    Three sediment cores in a north–south transect (3 degrees N to 13 degrees S) from different sediment types of the Central Indian Ocean Basin (CIOB) are studied to understand the possible relationship between magnetic susceptibility (Chi) and Al, Fe...

  20. New insights into the mineralogy of the Atlantis II Deep metalliferous sediments, Red Sea

    Science.gov (United States)

    Laurila, Tea E.; Hannington, Mark D.; Leybourne, Matthew; Petersen, Sven; Devey, Colin W.; Garbe-Schönberg, Dieter

    2015-12-01

    The Atlantis II Deep of the Red Sea hosts the largest known hydrothermal ore deposit on the ocean floor and the only modern analog of brine pool-type metal deposition. The deposit consists mainly of chemical-clastic sediments with input from basin-scale hydrothermal and detrital sources. A characteristic feature is the millimeter-scale layering of the sediments, which bears a strong resemblance to banded iron formation (BIF). Quantitative assessment of the mineralogy based on relogging of archived cores, detailed petrography, and sequential leaching experiments shows that Fe-(oxy)hydroxides, hydrothermal carbonates, sulfides, and authigenic clays are the main "ore" minerals. Mn-oxides were mainly deposited when the brine pool was more oxidized than it is today, but detailed logging shows that Fe-deposition and Mn-deposition also alternated at the scale of individual laminae, reflecting short-term fluctuations in the Lower Brine. Previous studies underestimated the importance of nonsulfide metal-bearing components, which formed by metal adsorption onto poorly crystalline Si-Fe-OOH particles. During diagenesis, the crystallinity of all phases increased, and the fine layering of the sediment was enhanced. Within a few meters of burial (corresponding to a few thousand years of deposition), biogenic (Ca)-carbonate was dissolved, manganosiderite formed, and metals originally in poorly crystalline phases or in pore water were incorporated into diagenetic sulfides, clays, and Fe-oxides. Permeable layers with abundant radiolarian tests were the focus for late-stage hydrothermal alteration and replacement, including deposition of amorphous silica and enrichment in elements such as Ba and Au.

  1. Gene expression in the deep biosphere.

    Science.gov (United States)

    Orsi, William D; Edgcomb, Virginia P; Christman, Glenn D; Biddle, Jennifer F

    2013-07-11

    Scientific ocean drilling has revealed a deep biosphere of widespread microbial life in sub-seafloor sediment. Microbial metabolism in the marine subsurface probably has an important role in global biogeochemical cycles, but deep biosphere activities are not well understood. Here we describe and analyse the first sub-seafloor metatranscriptomes from anaerobic Peru Margin sediment up to 159 metres below the sea floor, represented by over 1 billion complementary DNA (cDNA) sequence reads. Anaerobic metabolism of amino acids, carbohydrates and lipids seem to be the dominant metabolic processes, and profiles of dissimilatory sulfite reductase (dsr) transcripts are consistent with pore-water sulphate concentration profiles. Moreover, transcripts involved in cell division increase as a function of microbial cell concentration, indicating that increases in sub-seafloor microbial abundance are a function of cell division across all three domains of life. These data support calculations and models of sub-seafloor microbial metabolism and represent the first holistic picture of deep biosphere activities.

  2. Paleocorrosion studies in deep sea sediments and the geological disposal of nuclear wastes

    International Nuclear Information System (INIS)

    Fehrenbach, L.; Maurette, M.; Guichard, F.; Havette, A.; Monaco, A.

    1984-01-01

    Uncertainties still surround assessment of the safety of disposal of nuclear wastes incorporated into 'radwaste' matrices. This is mostly due to the long time required for radioactive decay of 237 Np. The present work explores the usefulness of an experimental approach in 'paleocorrosion', which should help in minimizing such uncertainties. In this approach, polished sections of sediments containing high concentrations of natural analogues of radwaste matrices are subjected to element micromapping. Thus it is possible to characterize the long-term interactions of such analogues in their geological repositories, and to identify which generate reaction aureoles and protective and/or unprotective coatings. These analogues include grains incorporated in deep sea sediments (uraninite and quartz from the Oklo uranium ore deposit; volcanic ash particles; magnetic cosmic spherules). The present results indicate that uraninite should be a much more durable radwaste matrix than any type of glass in deep sea sediments. (orig./TWO)

  3. Hidden cycle of dissolved organic carbon in the deep ocean.

    Science.gov (United States)

    Follett, Christopher L; Repeta, Daniel J; Rothman, Daniel H; Xu, Li; Santinelli, Chiara

    2014-11-25

    Marine dissolved organic carbon (DOC) is a large (660 Pg C) reactive carbon reservoir that mediates the oceanic microbial food web and interacts with climate on both short and long timescales. Carbon isotopic content provides information on the DOC source via δ(13)C and age via Δ(14)C. Bulk isotope measurements suggest a microbially sourced DOC reservoir with two distinct components of differing radiocarbon age. However, such measurements cannot determine internal dynamics and fluxes. Here we analyze serial oxidation experiments to quantify the isotopic diversity of DOC at an oligotrophic site in the central Pacific Ocean. Our results show diversity in both stable and radio isotopes at all depths, confirming DOC cycling hidden within bulk analyses. We confirm the presence of isotopically enriched, modern DOC cocycling with an isotopically depleted older fraction in the upper ocean. However, our results show that up to 30% of the deep DOC reservoir is modern and supported by a 1 Pg/y carbon flux, which is 10 times higher than inferred from bulk isotope measurements. Isotopically depleted material turns over at an apparent time scale of 30,000 y, which is far slower than indicated by bulk isotope measurements. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Collectively these results provide an unprecedented view of the ways in which DOC moves through the marine carbon cycle.

  4. Predicted peak temperature-rises around a high-level radioactive waste canister emplaced in the deep ocean bed

    International Nuclear Information System (INIS)

    Kipp, K.L.

    1978-06-01

    A simple mathematical model of heat conduction was used to evaluate the peak temperature-rise along the wall of a canister of high-level radioactive waste buried in deep ocean sediment. Three different amounts of vitrified waste, corresponding to standard Harvest, large Harvest, and AVM canisters, and three different waste loadings were studied. Peak temperature-rise was computed for the nine cases as a function of canister geometry and storage time between reprocessing and burial. Lower waste loadings or longer storage times than initially envisaged are necessary to prevent the peak temperature-rise from exceeding 200 0 C. The use of longer, thinner cylinders only modestly reduces the storage time for a given peak temperature. Effects of stacking of waste canisters and of close-packing were also studied. (author)

  5. Diffusive transfer of oxygen from seamount basaltic crust into overlying sediments: An example from the Clarion–Clipperton Fracture Zone

    NARCIS (Netherlands)

    Mewes, K.; Mogollón, J.M.; Picard, A.; Rühlemann, C.; Eisenhauer, A.; Kuhn, T.; Ziebis, W.; Kasten, S.

    2016-01-01

    The Clarion–Clipperton Fracture Zone (CCFZ) in the Pacific Ocean is characterized by organic carbon-starved sediments and meter-scale oxygen penetration into the sediment. Furthermore, numerous seamounts occur throughout its deep-sea plain, which may serve as conduits for low-temperature

  6. Seasonal and interannual variability in deep ocean particle fluxes at the Oceanic Flux Program (OFP)/Bermuda Atlantic Time Series (BATS) site in the western Sargasso Sea near Bermuda

    Science.gov (United States)

    Conte, Maureen H.; Ralph, Nate; Ross, Edith H.

    Since 1978, the Oceanic Flux Program (OFP) time-series sediment traps have measured particle fluxes in the deep Sargasso Sea near Bermuda. There is currently a 20+yr flux record at 3200-m depth, a 12+yr flux at 1500-m depth, and a 9+yr record at 500-m depth. Strong seasonality is observed in mass flux at all depths, with a flux maximum in February-March and a smaller maximum in December-January. There is also significant interannual variability in the flux, especially with respect to the presence/absence of the December-January flux maximum and in the duration of the high flux period in the spring. The flux records at the three depths are surprisingly coherent, with no statistically significant temporal lag between 500 and 3200-m fluxes at our biweekly sample resolution. Bulk compositional data indicate an extremely rapid decrease in the flux of organic constituents with depth between 500 and 1500-m, and a smaller decrease with depth between 1500 and 3200-m depth. In contrast, carbonate flux is uniform or increases slightly between 500 and 1500-m, possibly reflecting deep secondary calcification by foraminifera. The lithogenic flux increases by over 50% between 500 and 3200-m depth, indicating strong deep water scavenging/repackaging of suspended lithogenic material. Concurrent with the rapid changes in flux composition, there is a marked reduction in the heterogeneity of the sinking particle pool with depth, especially within the mesopelagic zone. By 3200-m depth, the bulk composition of the sinking particle pool is strikingly uniform, both seasonally and over variations in mass flux of more than an order of magnitude. These OFP results provide strong indirect evidence for the intensity of reprocessing of the particle pool by resident zooplankton within mesopelagic and bathypelagic waters. The rapid loss of organic components, the marked reduction in the heterogeneity of the bulk composition of the flux, and the increase in terrigenous fluxes with depth are most

  7. Planktonic foraminifera-derived environmental DNA extracted from abyssal sediments preserves patterns of plankton macroecology

    Directory of Open Access Journals (Sweden)

    R. Morard

    2017-06-01

    Full Text Available Deep-sea sediments constitute a unique archive of ocean change, fueled by a permanent rain of mineral and organic remains from the surface ocean. Until now, paleo-ecological analyses of this archive have been mostly based on information from taxa leaving fossils. In theory, environmental DNA (eDNA in the sediment has the potential to provide information on non-fossilized taxa, allowing more comprehensive interpretations of the fossil record. Yet, the process controlling the transport and deposition of eDNA onto the sediment and the extent to which it preserves the features of past oceanic biota remains unknown. Planktonic foraminifera are the ideal taxa to allow an assessment of the eDNA signal modification during deposition because their fossils are well preserved in the sediment and their morphological taxonomy is documented by DNA barcodes. Specifically, we re-analyze foraminiferal-specific metabarcodes from 31 deep-sea sediment samples, which were shown to contain a small fraction of sequences from planktonic foraminifera. We confirm that the largest portion of the metabarcode originates from benthic bottom-dwelling foraminifera, representing the in situ community, but a small portion (< 10 % of the metabarcodes can be unambiguously assigned to planktonic taxa. These organisms live exclusively in the surface ocean and the recovered barcodes thus represent an allochthonous component deposited with the rain of organic remains from the surface ocean. We take advantage of the planktonic foraminifera portion of the metabarcodes to establish to what extent the structure of the surface ocean biota is preserved in sedimentary eDNA. We show that planktonic foraminifera DNA is preserved in a range of marine sediment types, the composition of the recovered eDNA metabarcode is replicable and that both the similarity structure and the diversity pattern are preserved. Our results suggest that sedimentary eDNA could preserve the ecological structure of

  8. Biotic and a-biotic Mn and Fe cycling in deep sediments across a gradient of sulfate reduction rates along the California margin

    Science.gov (United States)

    Schneider-Mor, A.; Steefel, C.; Maher, K.

    2011-12-01

    The coupling between the biological and a-biotic processes controlling trace metals in deep marine sediments are not well understood, although the fluxes of elements and trace metals across the sediment-water interface can be a major contribution to ocean water. Four marine sediment profiles (ODP leg 167 sites 1011, 1017, 1018 and 1020)were examined to evaluate and quantify the biotic and abiotic reaction networks and fluxes that occur in deep marine sediments. We compared biogeochemical processes across a gradient of sulfate reduction (SR) rates with the objective of studying the processes that control these rates and how they affect major elements as well as trace metal redistribution. The rates of sulfate reduction, methanogenesis and anaerobic methane oxidation (AMO) were constrained using a multicomponent reactive transport model (CrunchFlow). Constraints for the model include: sediment and pore water concentrations, as well as %CaCO3, %biogenic silica, wt% carbon and δ13C of total organic carbon (TOC), particulate organic matter (POC) and mineral associated carbon (MAC). The sites are distinguished by the depth of AMO: a shallow zone is observed at sites 1018 (9 to 19 meters composite depth (mcd)) and 1017 (19 to 30 mcd), while deeper zones occur at sites 1011 (56 to 76 mcd) and 1020 (101 to 116 mcd). Sulfate reduction rates at the shallow AMO sites are on the order 1x10-16 mol/L/yr, much faster than rates in the deeper zone sulfate reduction (1-3x10-17 mol/L/yr), as expected. The dissolved metal ion concentrations varied between the sites, with Fe (0.01-7 μM) and Mn (0.01-57 μM) concentrations highest at Site 1020 and lowest at site 1017. The highest Fe and Mn concentrations occurred at various depths, and were not directly correlated with the rates of sulfate reduction and the maximum alkalinity values. The main processes that control cycling of Fe are the production of sulfide from sulfate reduction and the distribution of Fe-oxides. The Mn distribution

  9. Desiccation-crack-induced salinization in deep clay sediment

    Directory of Open Access Journals (Sweden)

    S. Baram

    2013-04-01

    Full Text Available A study on water infiltration and solute transport in a clayey vadose zone underlying a dairy farm waste source was conducted to assess the impact of desiccation cracks on subsurface evaporation and salinization. The study is based on five years of continuous measurements of the temporal variation in the vadose zone water content and on the chemical and isotopic composition of the sediment and pore water in it. The isotopic composition of water stable isotopes (δ18O and δ2H in water and sediment samples, from the area where desiccation crack networks prevail, indicated subsurface evaporation down to ~ 3.5 m below land surface, and vertical and lateral preferential transport of water, following erratic preferential infiltration events. Chloride (Cl− concentrations in the vadose zone pore water substantially increased with depth, evidence of deep subsurface evaporation and down flushing of concentrated solutions from the evaporation zones during preferential infiltration events. These observations led to development of a desiccation-crack-induced salinization (DCIS conceptual model. DCIS suggests that thermally driven convective air flow in the desiccation cracks induces evaporation and salinization in relatively deep sections of the subsurface. This conceptual model supports previous conceptual models on vadose zone and groundwater salinization in fractured rock in arid environments and extends its validity to clayey soils in semi-arid environments.

  10. The Nicobar Fan and sediment provenance: preliminary results from IODP Expedition 362, NE Indian Ocean

    Science.gov (United States)

    Pickering, K. T.; Pouderoux, H.; Milliken, K. L.; Carter, A.; Chemale, F., Jr.; Kutterolf, S.; Mukoyoshi, H.; Backman, J.; McNeill, L. C.; Dugan, B.; Expedition 362 Scientists, I.

    2017-12-01

    IODP Expedition 362 (6 Aug-6 Oct 2016) was designed to drill the input materials of the north Sumatran subduction zone, part of the 5000 km long Sunda subduction system and to understand the origin of the Mw 9.2 earthquake and tsunami that devastated coastal communities around the Indian Ocean in 2004 linked to unexpectedly shallow seismogenic slip and a distinctive forearc prism structure (1,2,3). Two sites, U1480 and U1481 on the Indian oceanic plate 250 km SW of the subduction zone on the eastern flank of the Ninetyeast Ridge, were drilled, cored, and logged to a maximum depth of 1500 m below seafloor. The input materials of the north Sumatran subduction zone are a thick (up to 4-5 km) succession mainly of Bengal-Nicobar Fan siliciclastic sediments overlying a mainly pelagic/hemipelagic succession, with igneous and volcaniclastic material above oceanic basement. At Sites U1480 and U1481, above the igneous basement ( 60-70 Ma), the sedimentary succession comprises deep-marine tuffaceous deposits with igneous intrusions, overlain by pelagic deposits, including chalk, and a thick Nicobar Fan succession of sediment gravity-flow (SGF) deposits, mainly turbidites and muddy debrites. The Nicobar Fan deposits (estimated total volume of 9.2 x 106 km3: 3) represent >90% of the input section at the drill sites and many of the beds are rich in plant material. These beds are intercalated with calcareous clays. Sediment accumulation rates reached 10-40 cm/kyr in the late Miocene to Pliocene, but were much reduced since 1.6 Ma. The onset of Nicobar Fan deposition at the drill sites ( 9.5 Ma; 2) is much younger than was anticipated precruise ( 30-40 Ma), based on previous regional analyses of Bengal-Nicobar Fan history and presumptions of gradual fan progradation. Our preliminary results suggest that the Nicobar Fan was active between 1.6 and 9.5 Ma, and possibly since 30 Ma (3). The observed mineralogical assemblage of the SGF deposits and zircon age dating are consistent with

  11. The Oceanic Flux Program: A three decade time-series of particle flux in the deep Sargasso Sea

    Science.gov (United States)

    Weber, J. C.; Conte, M. H.

    2010-12-01

    The Oceanic Flux Program (OFP), 75 km SE of Bermuda, is the longest running time-series of its kind. Initiated in 1978, the OFP has produced an unsurpassed, nearly continuous record of temporal variability in deep ocean fluxes, with a >90% temporal coverage at 3200m depth. The OFP, in conjunction with the co-located Bermuda-Atlantic Time Series (BATS) and the Bermuda Testbed Mooring (BTM) time-series, has provided key observations enabling detailed assessment of how seasonal and non-seasonal variability in the deep ocean is linked with the overlying physical and biogeochemical environment. This talk will focus on the short-term flux variability that overlies the seasonal flux pattern in the Sargasso Sea, emphasizing episodic extreme flux events. Extreme flux events are responsible for much of the year-to-year variability in mean annual flux and are most often observed during early winter and late spring when surface stratification is weak or transient. In addition to biological phenomena (e.g. salp blooms), passage of productive meso-scale features such as eddies, which alter surface water mixing characteristics and surface export fluxes, may initiate some extreme flux events. Yet other productive eddies show a minimal influence on the deep flux, underscoring the importance of upper ocean ecosystem structure and midwater processes on the coupling between the surface ocean environment and deep fluxes. Using key organic and inorganic tracers, causative processes that influence deep flux generation and the strength of the coupling with the surface ocean environment can be identified.

  12. The global marine phosphorus cycle: sensitivity to oceanic circulation

    Directory of Open Access Journals (Sweden)

    C. P. Slomp

    2007-01-01

    Full Text Available A new mass balance model for the coupled marine cycles of phosphorus (P and carbon (C is used to examine the relationships between oceanic circulation, primary productivity, and sedimentary burial of reactive P and particulate organic C (POC, on geological time scales. The model explicitly represents the exchanges of water and particulate matter between the continental shelves and the open ocean, and it accounts for the redox-dependent burial of POC and the various forms of reactive P (iron(III-bound P, particulate organic P (POP, authigenic calcium phosphate, and fish debris. Steady state and transient simulations indicate that a slowing down of global ocean circulation decreases primary production in the open ocean, but increases that in the coastal ocean. The latter is due to increased transfer of soluble P from deep ocean water to the shelves, where it fuels primary production and causes increased reactive P burial. While authigenic calcium phosphate accounts for most reactive P burial ocean-wide, enhanced preservation of fish debris may become an important reactive P sink in deep-sea sediments during periods of ocean anoxia. Slower ocean circulation globally increases POC burial, because of enhanced POC preservation under anoxia in deep-sea depositional environments and higher primary productivity along the continental margins. In accordance with geological evidence, the model predicts increased accumulation of reactive P on the continental shelves during and following periods of ocean anoxia.

  13. Investigating Deep-Marine Sediment Waves in the Northern Gulf of Mexico Using 3D Seismic Data

    Science.gov (United States)

    Wang, Z.; Gani, M. R.

    2016-12-01

    Deep-water depositional elements have been studied for decades using outcrop, flume tank, sidescan sonar, and seismic data. Even though they have been well recognized by researchers, the improvements in the quality of 3D seismic data with increasingly larger dimension allow detailed analysis of deep-water depositional elements with new insights. This study focuses on the deep-marine sediment waves in the northern Gulf of Mexico. By interpreting a 3D seismic dataset covering 635 km2 at Mississippi Canyon and Viosca Knoll areas, large sediment waves, generated by sediment gravity flows, were mapped and analyzed with various seismic attributes. A succession of sediment waves, approximately 100 m in thickness, is observed on the marine slope that tapers out at the toe of the slope. The individual sediment wave exhibits up to 500 m in wavelength and up to 20 m in height. The wave crests oriented northeast-southwest are broadly aligned parallel to the regional slope-strike, indicating their sediment gravity flow origin. The crestlines are straight or slightly sinuous, with sinuosity increasing downslope. Their anti-dune patterns likely imply the presence of supercritical flows. The sediment waves have a retrogradational stacking pattern. Seismic amplitude maps of each sediment wave revealed that after depositing the majority of sheet-like sands on the upper slope, sediment gravity flows started to form large sediment waves on the lower slope. The steep and narrow upcurrent flanks of the sediment waves always display higher amplitudes than the gentle and wide downcurrent flanks, indicating that the sands were likely preferentially trapped along the upcurrent flanks, whereas the muds spread along the downcurrent flanks. The formation of sediment waves likely requires a moderate sand-mud ratio, as suggested by these observations: (1) absence of sediment waves on the upper slope where the sands were mainly deposited as unconfined sheets with a high sand-mud ratio; (2

  14. Meridional overturning circulation conveys fast acidification to the deep Atlantic Ocean

    Science.gov (United States)

    Perez, Fiz F.; Fontela, Marcos; García-Ibáñez, Maribel I.; Mercier, Herlé; Velo, Anton; Lherminier, Pascale; Zunino, Patricia; de La Paz, Mercedes; Alonso-Pérez, Fernando; Guallart, Elisa F.; Padin, Xose A.

    2018-02-01

    Since the Industrial Revolution, the North Atlantic Ocean has been accumulating anthropogenic carbon dioxide (CO2) and experiencing ocean acidification, that is, an increase in the concentration of hydrogen ions (a reduction in pH) and a reduction in the concentration of carbonate ions. The latter causes the ‘aragonite saturation horizon’—below which waters are undersaturated with respect to a particular calcium carbonate, aragonite—to move to shallower depths (to shoal), exposing corals to corrosive waters. Here we use a database analysis to show that the present rate of supply of acidified waters to the deep Atlantic could cause the aragonite saturation horizon to shoal by 1,000-1,700 metres in the subpolar North Atlantic within the next three decades. We find that, during 1991-2016, a decrease in the concentration of carbonate ions in the Irminger Sea caused the aragonite saturation horizon to shoal by about 10-15 metres per year, and the volume of aragonite-saturated waters to reduce concomitantly. Our determination of the transport of the excess of carbonate over aragonite saturation (xc[CO32-])—an indicator of the availability of aragonite to organisms—by the Atlantic meridional overturning circulation shows that the present-day transport of carbonate ions towards the deep ocean is about 44 per cent lower than it was in preindustrial times. We infer that a doubling of atmospheric anthropogenic CO2 levels—which could occur within three decades according to a ‘business-as-usual scenario’ for climate change—could reduce the transport of xc[CO32-] by 64-79 per cent of that in preindustrial times, which could severely endanger cold-water coral habitats. The Atlantic meridional overturning circulation would also export this acidified deep water southwards, spreading corrosive waters to the world ocean.

  15. Light penetration structures the deep acoustic scattering layers in the global ocean

    DEFF Research Database (Denmark)

    Aksnes, Dag L.; Rostad, Anders; Kaartvedt, Stein

    2017-01-01

    The deep scattering layer (DSL) is a ubiquitous acoustic signature found across all oceans and arguably the dominant feature structuring the pelagic open ocean ecosystem. It is formed by mesopelagic fishes and pelagic invertebrates. The DSL animals are an important food source for marine megafauna...... distributions with hypoxic waters. In enhancing understanding of this phenomenon, our results should improve the ability to predict and model the dynamics of one of the largest animal biomass components on earth, with key roles in the oceanic biological carbon pump and food web....

  16. Ocean disposal of heat generating radioactive waste

    International Nuclear Information System (INIS)

    1985-11-01

    The detailed radiological assessment of any proposed operations for the disposal of heat-generating radioactive waste in deep ocean sediments would require data describing expected embedment depths and spacing of the waste. In this study a theoretical model which predicts penetrator trajectories from launch through to rest in the sediment has been produced and has been used to generate data for environmental models. The trajectory model has been used to study the effects of small imperfections and launch parameters on the motion of a reference penetrator through water and sediment. The model predicts that the horizontal displacements of the penetrators' final resting places in the sediment from their launch positions at the ocean surface could be limited to less than 15m by twisting their tail fins uniformly by just one degree to induce spinning. The reference penetrator is predicted to achieve satisfactory embedment depth for all the cases considered including allowance for the effect of curved penetration paths in the seabed. However, the ability of the model to represent highly non-linear sediment penetration paths is demonstrated. Distribution histograms of seabed impact points relative to specific release points are presented. The area of seabed required is calculated. (author)

  17. Microbial diversity in Cenozoic sediments recovered from the Lomonosov Ridge in the Central Arctic basin.

    Science.gov (United States)

    Forschner, Stephanie R; Sheffer, Roberta; Rowley, David C; Smith, David C

    2009-03-01

    The current understanding of microbes inhabiting deeply buried marine sediments is based largely on samples collected from continental shelves in tropical and temperate latitudes. The geographical range of marine subsurface coring was expanded during the Integrated Ocean Drilling Program Arctic Coring Expedition (IODP ACEX). This expedition to the ice-covered central Arctic Ocean successfully cored the entire 428 m sediment stack on the Lomonosov Ridge during August and September 2004. The recovered cores vary from siliciclastic sediment low in organic carbon ( 200 m below sea floor) sulfate reduction zone. The diversity of microbes within each zone was assessed using 16S rRNA phylogenetic markers. Bacterial 16S rRNA genes were successfully amplified from each of the biogeochemical zones, while archaea was only amplified from the deep sulfate reduction zone. The microbial communities at each zone are phylogenetically different and are most closely related to those from other deep subsurface environments.

  18. The Evolution of Deep Ocean Chemistry and Respired Carbon in the Eastern Equatorial Pacific Over the Last Deglaciation

    Science.gov (United States)

    de la Fuente, Maria; Calvo, Eva; Skinner, Luke; Pelejero, Carles; Evans, David; Müller, Wolfgang; Povea, Patricia; Cacho, Isabel

    2017-12-01

    It has been shown that the deep Eastern Equatorial Pacific (EEP) region was poorly ventilated during the Last Glacial Maximum (LGM) relative to Holocene values. This finding suggests a more efficient biological pump, which indirectly supports the idea of increased carbon storage in the deep ocean contributing to lower atmospheric CO2 during the last glacial. However, proxies related to respired carbon are needed in order to directly test this proposition. Here we present Cibicides wuellerstorfi B/Ca ratios from Ocean Drilling Program Site 1240 measured by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) as a proxy for deep water carbonate saturation state (Δ[CO32-], and therefore [CO32-]), along with δ13C measurements. In addition, the U/Ca ratio in foraminiferal coatings has been analyzed as an indicator of oxygenation changes. Our results show lower [CO32-], δ13C, and [O2] values during the LGM, which would be consistent with higher respired carbon levels in the deep EEP driven, at least in part, by reduced deep water ventilation. However, the difference between LGM and Holocene [CO32-] observed at our site is relatively small, in accordance with other records from across the Pacific, suggesting that a "counteracting" mechanism, such as seafloor carbonate dissolution, also played a role. If so, this mechanism would have increased average ocean alkalinity, allowing even more atmospheric CO2 to be "sequestered" by the ocean. Therefore, the deep Pacific Ocean very likely stored a significant amount of atmospheric CO2 during the LGM, specifically due to a more efficient biological carbon pump and also an increase in average ocean alkalinity.

  19. Organic carbon mass accumulation rate regulates the flux of reduced substances from the sediments of deep lakes

    Directory of Open Access Journals (Sweden)

    T. Steinsberger

    2017-07-01

    Full Text Available The flux of reduced substances, such as methane and ammonium, from the sediment to the bottom water (Fred is one of the major factors contributing to the consumption of oxygen in the hypolimnia of lakes and thus crucial for lake oxygen management. This study presents fluxes based on sediment porewater measurements from different water depths of five deep lakes of differing trophic states. In meso- to eutrophic lakes Fred was directly proportional to the total organic carbon mass accumulation rate (TOC-MAR of the sediments. TOC-MAR and thus Fred in eutrophic lakes decreased systematically with increasing mean hypolimnion depth (zH, suggesting that high oxygen concentrations in the deep waters of lakes were essential for the extent of organic matter mineralization leaving a smaller fraction for anaerobic degradation and thus formation of reduced compounds. Consequently, Fred was low in the 310 m deep meso-eutrophic Lake Geneva, with high O2 concentrations in the hypolimnion. By contrast, seasonal anoxic conditions enhanced Fred in the deep basin of oligotrophic Lake Aegeri. As TOC-MAR and zH are based on more readily available data, these relationships allow estimating the areal O2 consumption rate by reduced compounds from the sediments where no direct flux measurements are available.

  20. The detection of magnetotactic bacteria in deep sea sediments from the east Pacific Manganese Nodule Province.

    Science.gov (United States)

    Dong, Yi; Li, Jinhua; Zhang, Wuchang; Zhang, Wenyan; Zhao, Yuan; Xiao, Tian; Wu, Long-Fei; Pan, Hongmiao

    2016-04-01

    Magnetotactic bacteria (MTB) are distributed ubiquitously in sediments from coastal environments to the deep sea. The Pacific Manganese Nodule Province contains numerous polymetallic nodules mainly composed of manganese, iron, cobalt, copper and nickel. In the present study we used Illumina MiSeq sequencing technology to assess the communities of putative MTB in deep sea surface sediments at nine stations in the east Pacific Manganese Nodule Province. A total of 402 sequence reads from MTB were classified into six operational taxonomic units (OTUs). Among these, OTU113 and OTU759 were affiliated with the genus Magnetospira, OTU2224 and OTU2794 were affiliated with the genus Magnetococcus and Magnetovibrio, respectively, OTU3017 had no known genus affiliation, and OTU2556 was most similar to Candidatus Magnetananas. Interestingly, OTU759 was widely distributed, occurring at all study sites. Magnetism measurements revealed that all sediments were dominated by low coercivity, non-interacting single domain magnetic minerals. Transmission electron microscopy confirmed that the magnetic minerals were magnetosomes. Our data suggest that diverse putative MTB are widely distributed in deep sea surface sediments from the east Pacific Manganese Nodule Province. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  1. Molecular Phylogeny Of Microbes In The Deep-Sea Sediments From Tropical West Pacific Warm Pool

    Science.gov (United States)

    Wang, F.; Xiao, X.; Wang, P.

    2005-12-01

    The presence and phylogeny of bacteria and archaea in five deep-sea sediment samples collected from west Pacific Warm Pool area (WP-0, WP-1, WP-2, WP-3, WP-4), and in five sediment layers (1cm-, 3cm-, 6cm-, 10cm-, 12cm- layer) of the 12-cm sediment core of WP-0 were checked and compared. The microbial diversity in the five deep-sea sediments were similar as revealed by denaturing gradient gel electrophoresis, and all of them contained members of non-thermophilic marine group I crenarchaeota as the predominant archaeal group. The composition of methylotrophs including methanotrophs, sulfate reducing bacteria in the WP-0 sediment core were further investigated by molecular marker based analysis of mxaF, pmoA, dsrAB, specific anoxic methane oxidation archaeal and sulfate reducing bacterial 16S rRNA genes. From MxaF amino acid sequence analysis, it was demonstrated that microbes belonging to α - Proteobacteria most related to Hyphomicrobium and Methylobacterium were dominant aerobic methylotrophs in this deep-sea sediment; and small percentage of type II methanotrophs affiliating closest to Methylocystis and Methylosinus were also detected in this environment. mxaF quantitative PCR results showed that in the west Pacific WP sediment there existed around 3× 10 4-5 methylotrophs per gram sediment, 10-100 times more than that in samples collected from several other deep-sea Pacific sediment sample, but about 10 times less than that present in samples collected from rice and flower garden soil. Diverse groups of novel archaea (named as WPA), not belonging to any known archaeal lineages were checked out. They could be placed in the euryarchaeota kingdom, separated into two distinct groups, the main group was peripherally related with methanogens, the other group related with Thermoplasma. Possible sulfate reducing bacterial related with Desulfotomaculum, Desulfacinum, Desulfomonile and Desulfanuticus were also detected in our study. The vertical distributions of WPA

  2. Shelf erosion and submarine river canyons: implications for deep-sea oxygenation and ocean productivity during glaciation

    Directory of Open Access Journals (Sweden)

    I. Tsandev

    2010-06-01

    Full Text Available The areal exposure of continental shelves during glacial sea level lowering enhanced the transfer of erodible reactive organic matter to the open ocean. Sea level fall also activated submarine canyons thereby allowing large rivers to deposit their particulate load, via gravity flows, directly in the deep-sea. Here, we analyze the effects of shelf erosion and particulate matter re-routing to the open ocean during interglacial to glacial transitions, using a coupled model of the marine phosphorus, organic carbon and oxygen cycles. The results indicate that shelf erosion and submarine canyon formation may significantly lower deep-sea oxygen levels, by up to 25%, during sea level low stands, mainly due to the supply of new material from the shelves, and to a lesser extent due to particulate organic matter bypassing the coastal zone. Our simulations imply that deep-sea oxygen levels can drop significantly if eroded shelf material is deposited to the seafloor. Thus the glacial ocean's oxygen content could have been significantly lower than during interglacial stages. Primary production, organic carbon burial and dissolved phosphorus inventories are all affected by the erosion and rerouting mechanisms. However, re-routing of the continental and eroded shelf material to the deep-sea has the effect of decoupling deep-sea oxygen demand from primary productivity in the open ocean. P burial is also not affected showing a disconnection between the biogeochemical cycles in the water column and the P burial record.

  3. Paleoenvironments of the Jurassic and Cretaceous Oceans: Selected Highlights

    Science.gov (United States)

    Ogg, J. G.

    2007-12-01

    There are many themes contributing to the sedimentation history of the Mesozoic oceans. This overview briefly examines the roles of the carbonate compensation depth (CCD) and the associated levels of atmospheric carbon dioxide, of the evolution of marine calcareous microplankton, of major transgressive and regressive trends, and of super-plume eruptions. Initiation of Atlantic seafloor spreading in the Middle Jurassic coincided with an elevated carbonate compensation depth (CCD) in the Pacific-Tethys mega-ocean. Organic-rich sediments that would become the oil wealth of regions from Saudi Arabia to the North Sea were deposited during a continued rise in CCD during the Oxfordian-early Kimmeridgian, which suggests a possible increase in carbon dioxide release by oceanic volcanic activity. Deep-sea deposits in near-equatorial settings are dominated by siliceous shales or cherts, which reflect the productivity of siliceous microfossils in the tropical surface waters. The end-Jurassic explosion in productivity by calcareous microplankton contributed to the lowering of the CCD and onset of the chalk ("creta") deposits that characterize the Tithonian and lower Cretaceous in all ocean basins. During the mid-Cretaceous, the eruption of enormous Pacific igneous provinces (Ontong Java Plateau and coeval edifices) increased carbon dioxide levels. The resulting rise in CCD terminated chalk deposition in the deep sea. The excess carbon was progressively removed in widespread black-shale deposits in the Atlantic basins and other regions - another major episode of oil source rock. A major long-term transgression during middle and late Cretaceous was accompanied by extensive chalk deposition on continental shelves and seaways while the oceanic CCD remained elevated. Pacific guyots document major oscillations (sequences) of global sea level superimposed on this broad highstand. The Cretaceous closed with a progressive sea-level regression and lowering of the CCD that again enabled

  4. Late Eocene to present isotopic (Sr-Nd-Pb) and geochemical evolution of sediments from the Lomonosov Ridge, Arctic Ocean: Implications for continental sources and linkage with the North Atlantic Ocean

    Science.gov (United States)

    Stevenson, Ross; Poirier, André; Véron, Alain; Carignan, Jean; Hillaire-Marcel, Claude

    2015-09-01

    New geochemical and isotopic (Sr, Nd, Pb) data are presented for a composite sedimentary record encompassing the past 50 Ma of history of sedimentation on the Lomonosov Ridge in the Arctic Ocean. The sampled sediments encompass the transition of the Arctic basin from an enclosed anoxic basin to an open and ventilated oxidized ocean basin. The transition from anoxic basin to open ventilated ocean is accompanied by at least three geochemical and isotopic shifts and an increase in elements (e.g., K/Al) controlled by detrital minerals highlighting significant changes in sediment types and sources. The isotopic compositions of the sediments prior to ventilation are more variable but indicate a predominance of older crustal contributions consistent with sources from the Canadian Shield. Following ventilation, the isotopic compositions are more stable and indicate an increased contribution from younger material consistent with Eurasian and Pan-African crustal sources. The waxing and waning of these sources in conjunction with the passage of water through Fram Strait underlines the importance of the exchange of water mass between the Arctic and North Atlantic Oceans.

  5. Ocean disposal of heat generating waste

    International Nuclear Information System (INIS)

    1985-06-01

    A number of options for the disposal of vitrified heat generating waste are being studied to ensure that safe methods are available when the time comes for disposal operations to commence. This study has considered the engineering and operational aspects of the Penetrator Option for ocean disposal to enable technical comparisons with other options to be made. In the Penetrator Option concept, waste would be loaded into carefully designed containers which would be launched at a suitable deep ocean site where they would fall freely through the water and would embed themselves completely within the seabed sediments. Radiological protection would be provided by a multi-barrier system including the vitrified waste form, the penetrator containment, the covering sediment and the ocean. Calculations and demonstration have shown that penetrators could easily achieve embedment depths in excess of 30m and preliminary radiological assessments indicate that 30m of intact sediment would be an effective barrier for radionuclide isolation. The study concludes that a 75mm thickness of low carbon steel appears to be sufficient to provide a containment life of 500 to 1000 years during which time the waste heat output would have decayed to an insignificant level. Disposal costs have been assessed. (author)

  6. Formation of carbonate concretions in deep-sea sediment below the CCD and above an active gas hydrate system

    Science.gov (United States)

    Dicus, C. M.; Snyder, G. T.; Dickens, G. R.

    2004-12-01

    Site 1230 of the Ocean Drilling Program targeted the chemistry and microbiology of an active deep-water gas hydrate system in the Peru Trench. The site is noteworthy because, at nearly 6000 m water depth, it lies well below the carbonate compensation depth and the sediments comprise mostly terrigenous clays and biogenic silica. Shipboard work at this site delineated a prominent sulfate-methane transition (SMT) at 8-10 m below seafloor (mbsf) as well as some carbonate horizons. In this study, we present calcium and strontium data for pore waters and sediments at this site, including across the SMT. Concentration profiles show that dissolved Ca2+ diffuses downward from the seafloor toward the SMT, where a sharp inflection indicates consumption of Ca2+ into an authigenic phase. Dissolved Sr2+, on the other hand, diffuses upward from depth toward the SMT. Again, however, a prominent inflection suggests removal of Sr2+ to sediment. The inferences from pore water profiles are borne out by sediment chemistry. Large peaks in the calcium and strontium content of sediment mark the SMT. The calcium and strontium fronts reach ˜2700 and ˜5 mmol/kg, respectively, at 9 mbsf, which are much greater than average background values of ˜10 and ˜1 mmol/kg. These authigenic fronts are primarily composed of carbonate minerals, as determined by acetic acid extractions and x-ray diffraction. Because the calcium and strontium fronts coincide with both the SMT and changes in dissolved chemistry, it is proposed that the carbonates are currently forming as follows: methane rising from the underlying gas hydrate system reacts with dissolved sulfate through anaerobic oxidation of methane which releases HCO3- and alkalinity and causes carbonate precipitation. The overall process has been observed elsewhere; the Peru Trench is interesting, however, because the process leads to carbonate in sediments otherwise devoid of carbonate.

  7. Consolidation properties and stress history of some deep sea sediments

    International Nuclear Information System (INIS)

    Silva, A.J.; Jordan, S.A.

    1983-09-01

    This paper summarizes results of 180 consolidation tests on samples from 52 cores taken with a variety of samplers in deep sea regimes of the North Western Atlantic and North Central Pacific. Most of the samplers were of large cross sectional area (over 10-cm dia) and attention was given to improving field techniques and reducing structural disturbance to the sediments. Good quality samples have been recovered to depths in excess of 25 m in several locations. The sediments were primarily fine-grained clays and silty clays with the predominant clay mineral being illite; however, the presence of smectite and calcium carbonate in some samples had significant influence on the properties. 34 references, 11 figures, 2 tables

  8. Ship Sensor Observations for Deep Sea Medicines 2003 - Office of Ocean Exploration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Hourly measurements made by selected ship sensors on the NOAA ship Ronald H. Brown during the "Deep Sea Medicines 2003: Exploration of the Gulf of Mexico" expedition...

  9. Frequency of Tropical Ocean Deep Convection and Global Warming

    Science.gov (United States)

    Aumann, H. H.; Behrangi, A.; Ruzmaikin, A.

    2017-12-01

    The average of 36 CMIP5 models predicts about 3K of warming and a 4.7% increase in precipitation for the tropical oceans with a doubling of the CO2 by the end of this century. For this scenario we evaluate the increase in the frequency of Deep Convective Clouds (DCC) in the tropical oceans. We select only DCC which reach or penetrate the tropopause in the 15 km AIRS footprint. The evaluation is based on Probability Distribution Functions (PDFs) of the current temperatures of the tropical oceans, those predicted by the mean of the CMIP5 models and the PDF of the DCC process. The PDF of the DCC process is derived from the Atmospheric Infrared Sounder (AIRS) between the years 2003 and 2016. During this time the variability due Enso years provided a 1 K p-p change in the mean tropical SST. The key parameter is the SST associated with the onset of the DCC process. This parameter shifts only 0.5 K for each K of warming of the oceans. As a result the frequency of DCC is expected to increases by the end of this century by about 50% above the current frequency.

  10. Ammolagena clavata (Jones and Parker, 1860), an agglutinated benthic foraminiferal species - first report from the Recent sediments, Arabian Sea, Indian Ocean region

    Digital Repository Service at National Institute of Oceanography (India)

    Nigam, R.; Mazumder, A.; Saraswat, R.

    The rare presence of the agglutinated foraminiferal species Ammolagena clavata is presented for the first time from the Recent sediments of the Indian Ocean region. This species has previously been reported in Recent sediments from all other oceans...

  11. Photo-lability of deep ocean dissolved black carbon

    Directory of Open Access Journals (Sweden)

    A. Stubbins

    2012-05-01

    Full Text Available Dissolved black carbon (DBC, defined here as condensed aromatics isolated from seawater via PPL solid phase extraction and quantified as benzenepolycarboxylic acid (BPCA oxidation products, is a significant component of the oceanic dissolved organic carbon (DOC pool. These condensed aromatics are widely distributed in the open ocean and appear to be tens of thousands of years old. As such DBC is regarded as highly refractory. In the current study, the photo-lability of DBC, DOC and coloured dissolved organic matter (CDOM; ultraviolet-visible absorbance were determined over the course of a 28 day irradiation of North Atlantic Deep Water under a solar simulator. During the irradiation DBC fell from 1044 ± 164 nM-C to 55 ± 15 nM-C, a 20-fold decrease in concentration. Dissolved black carbon photo-degradation was more rapid and more extensive than for bulk CDOM and DOC. The concentration of DBC correlated with CDOM absorbance and the quality of DBC indicated by the ratios of different BPCAs correlated with CDOM absorbance spectral slope, suggesting the optical properties of CDOM may provide a proxy for both DBC concentrations and quality in natural waters. Further, the photo-lability of components of the DBC pool increased with their degree of aromatic condensation. These trends indicate that a continuum of compounds of varying photo-lability exists within the marine DOC pool. In this continuum, photo-lability scales with aromatic character, specifically the degree of condensation. Scaling the rapid photo-degradation of DBC to rates of DOC photo-mineralisation for the global ocean leads to an estimated photo-chemical half-life for oceanic DBC of less than 800 years. This is more than an order of magnitude shorter than the apparent age of DBC in the ocean. Consequently, photo-degradation is posited as the primary sink for oceanic DBC and the apparent survival of DBC molecules in the oceans for millennia appears to be facilitated not by their

  12. Suspended sediment concentration and optical property observations of mixed-turbidity, coastal waters through multispectral ocean color inversion

    Science.gov (United States)

    Multispectral satellite ocean color data from high-turbidity areas of the coastal ocean contain information about the surface concentrations and optical properties of suspended sediments and colored dissolved organic matter (CDOM). Empirical and semi-analytical inversion algorit...

  13. 10Be and 9Be in South Atlantic DSDP Site 519: Relation to geomagnetic reversals and to sediment composition

    International Nuclear Information System (INIS)

    Henken-Mellies, W.U.; Hsue, K.J.; Bonani, G.; Hofmann, H.J.; Woelfli, W.; Beer, J.; Heller, F.; Shen, C.; Suter, M.

    1990-01-01

    A high-resolution 10 Be profile has been measured on DSDP Site 519 (central South Atlantic) in order to search for changes in the flux of 10 Be into a pelagic sediment during geomagnetic reversals as compared with times of constant magnetic polarity. The decay corrected 10 Be concentrations range from 1 to 9x10 8 at/g. The average 10 Be flux rate is 5x10 8 [at cm -2 kyr -1 ]. 9 Be and CaCO 3 were measured on the same samples. The 10 Be vs. depth curve is overall similar to the 9 Be vs. depth curve, while the CaCO 3 vs. depth curve anticorrelates the beryllium isotope curves closely, implying that Be is carried mainly by the non-CaCO 3 phases of the sediment. The positive correlation between 10 Be along with the fact that the average 10 Be/ 9 Be ratio of 5.5x10 -8 is within the range of 10 Be/ 9 Be ratios reported for deep ocean water leads us to conclude (1) that the beryllium isotopes come close to an equilibrium in the open ocean, and (2) that the 10 Be/ 9 Be in deep sea sediments with a low detrital component monitors the 10 Be/ 9 Be of deep ocean water trough time. Relative increases of the 10 Be/ 9 Be ratio are observed in the vicinity of the geomagnetic reversals, but the relationship between reversals and higher 10 Be/ 9 Be remains doubtful. Other mechanisms which could alter the 10 Be/ 9 Be ratio are discussed (input of 10 Be by melting of glacial ice; changing input of 9 Be due to changes in continental erosion; changing deep ocean circulation; changing scavenging activity at ocean margins), but as yet no conclusive explanation for the observed behavior of the beryllium isotopes can be given. (orig.)

  14. Putting the Deep Biosphere and Gas Hydrates on the Map

    Science.gov (United States)

    Sikorski, Janelle J.; Briggs, Brandon R.

    2016-01-01

    Microbial processes in the deep biosphere affect marine sediments, such as the formation of gas hydrate deposits. Gas hydrate deposits offer a large source of natural gas with the potential to augment energy reserves and affect climate and seafloor stability. Despite the significant interdependence between life and geology in the ocean, coverage…

  15. Alterations in geochemical associations in artificially disturbed deep-sea sediments

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B.N.; Parthiban, G.; Banaulikar, S.; Sarkar, S.

    Alterations in Geochemical Associations in Artificially Disturbed Deep-Sea Sediments B. NAGENDER NATH, G. PARTHIBAN, AND S. BANAULIKAR National Institute of Oceanography, Dona Paula, Goa, India SUBHADEEP SARKAR Department of Geology and Geophysics, Indian... the lithogenic component by transporting it from other locations within the Basin during commercial mining operations. Keywords manganese nodule mining, artificial benthic disturbance experiment, environmental impact assessment, metals Trace metals in marine...

  16. Geochemistry of deep-sea sediment cores from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Mudholkar, A.V.; Pattan, J.N.; Parthiban, G.

    , thought to be of diagenetic origin. Metals are suppliEd. by upward migration from a suboxic to anoxic zone at an intermediate depth of 12-35 cm below the sediment-water interface in all the cores. Buried maxima in transition metal concentration at depth...

  17. The discovery of new deep-sea hydrothermal vent communities in the southern ocean and implications for biogeography.

    Directory of Open Access Journals (Sweden)

    Alex D Rogers

    2012-01-01

    Full Text Available Since the first discovery of deep-sea hydrothermal vents along the Galápagos Rift in 1977, numerous vent sites and endemic faunal assemblages have been found along mid-ocean ridges and back-arc basins at low to mid latitudes. These discoveries have suggested the existence of separate biogeographic provinces in the Atlantic and the North West Pacific, the existence of a province including the South West Pacific and Indian Ocean, and a separation of the North East Pacific, North East Pacific Rise, and South East Pacific Rise. The Southern Ocean is known to be a region of high deep-sea species diversity and centre of origin for the global deep-sea fauna. It has also been proposed as a gateway connecting hydrothermal vents in different oceans but is little explored because of extreme conditions. Since 2009 we have explored two segments of the East Scotia Ridge (ESR in the Southern Ocean using a remotely operated vehicle. In each segment we located deep-sea hydrothermal vents hosting high-temperature black smokers up to 382.8°C and diffuse venting. The chemosynthetic ecosystems hosted by these vents are dominated by a new yeti crab (Kiwa n. sp., stalked barnacles, limpets, peltospiroid gastropods, anemones, and a predatory sea star. Taxa abundant in vent ecosystems in other oceans, including polychaete worms (Siboglinidae, bathymodiolid mussels, and alvinocaridid shrimps, are absent from the ESR vents. These groups, except the Siboglinidae, possess planktotrophic larvae, rare in Antarctic marine invertebrates, suggesting that the environmental conditions of the Southern Ocean may act as a dispersal filter for vent taxa. Evidence from the distinctive fauna, the unique community structure, and multivariate analyses suggest that the Antarctic vent ecosystems represent a new vent biogeographic province. However, multivariate analyses of species present at the ESR and at other deep-sea hydrothermal vents globally indicate that vent biogeography is more

  18. Extraction of seawater-derived neodymium from different phases of deep sea sediments by selective leaching

    Science.gov (United States)

    Blaser, P.; Lippold, J. A.; Frank, N.; Gutjahr, M.; Böhm, E.

    2014-12-01

    In order to deduce reliable information about the interaction of the oceans with the climate system as a whole in the past, the reconstruction of water mass circulation is crucial. The analysis of seawater-derived neodymium isotopes (143Nd/144Nd, expressed as ɛNd) in marine sediments provides a unique proxy for deep water provenance in particular in the Atlantic [1]. The ɛNd signature and thus the mixing proportion of the local bottom water masses is archived in authigenic phases in the sediment. Obtaining seawater ɛNd from authigenic accretions bound to foraminiferal tests has lately become the preferred since most reliable method [2]. Attempts have also been made to extract the Nd-rich authigenic metal fraction by leaching it off the bulk sediment and thereby use this proxy with less effort, in the highest possible resolution and in sediments where foraminifera are not sufficiently present. However, often other sedimentary components are also leached in the process and contaminate the extracted Nd [3,4]. In this project several core-top and older sediments across the Atlantic have been leached in ten consecutive steps with either dilute buffered acetic acid or an acid-reductive solution. The leachates were analysed on their elemental and Nd isotope compositions, as well as rare earth element (REE) distributions. By graduating the total leaching procedure into smaller stages the results display which processes take place in the course of sediment leaching in the laboratory and which components of the sediment are most reactive. Thus, they help to better evaluate the quality of sediment leaches for ɛNd analysis. Clearly, organic calcite acts as a fast reacting buffer and at the point where its amount is sufficiently reduced the leaching of other components commences and the Nd concentration peaks. Corruption of the extracted ɛNd signal by non-authigenic sources in many cases occured early in the leaching sequence, indicating that only very cautious leaching

  19. Difference of nitrogen-cycling microbes between shallow bay and deep-sea sediments in the South China Sea.

    Science.gov (United States)

    Yu, Tiantian; Li, Meng; Niu, Mingyang; Fan, Xibei; Liang, Wenyue; Wang, Fengping

    2018-01-01

    In marine sediments, microorganisms are known to play important roles in nitrogen cycling; however, the composition and quantity of microbes taking part in each process of nitrogen cycling are currently unclear. In this study, two different types of marine sediment samples (shallow bay and deep-sea sediments) in the South China Sea (SCS) were selected to investigate the microbial community involved in nitrogen cycling. The abundance and composition of prokaryotes and seven key functional genes involved in five processes of the nitrogen cycle [nitrogen fixation, nitrification, denitrification, dissimilatory nitrate reduction to ammonium (DNRA), and anaerobic ammonia oxidation (anammox)] were presented. The results showed that a higher abundance of denitrifiers was detected in shallow bay sediments, while a higher abundance of microbes involved in ammonia oxidation, anammox, and DNRA was found in the deep-sea sediments. Moreover, phylogenetic differentiation of bacterial amoA, nirS, nosZ, and nrfA sequences between the two types of sediments was also presented, suggesting environmental selection of microbes with the same geochemical functions but varying physiological properties.

  20. Moving beyond the age-depth model paradigm in deep sea palaeoclimate archives: dual radiocarbon and stable isotope analysis on single foraminifera

    NARCIS (Netherlands)

    Lougheed, Bryan C.; Metcalfe, Brett; Ninnemann, Ulysses S.; Wacker, Lukas

    2017-01-01

    Late-glacial palaeoclimate reconstructions from deep-sea sediment archives provide valuable insight into past rapid changes in ocean chemistry, but only a small proportion of the ocean floor is suitable for such reconstructions using the existing state-of-the-art using the age-depth approach. We

  1. From the Surface to the Deep-Sea: Bacterial Distributions across Polymetallic Nodule Fields in the Clarion-Clipperton Zone of the Pacific Ocean.

    Science.gov (United States)

    Lindh, Markus V; Maillot, Brianne M; Shulse, Christine N; Gooday, Andrew J; Amon, Diva J; Smith, Craig R; Church, Matthew J

    2017-01-01

    Marine bacteria regulate fluxes of matter and energy essential for pelagic and benthic organisms and may also be involved in the formation and maintenance of commercially valuable abyssal polymetallic nodules. Future mining of these nodule fields is predicted to have substantial effects on biodiversity and physicochemical conditions in mined areas. Yet, the identity and distributions of bacterial populations in deep-sea sediments and associated polymetallic nodules has received relatively little attention. We examined bacterial communities using high-throughput sequencing of bacterial 16S rRNA gene fragments from samples collected in the water column, sediment, and polymetallic nodules in the Pacific Ocean (bottom depth ≥4,000 m) in the eastern Clarion-Clipperton Zone. Operational taxonomic units (OTUs; defined at 99% 16S rRNA gene identity) affiliated with JTB255 (Gammaproteobacteria) and Rhodospirillaceae (Alphaproteobacteria) had higher relative abundances in the nodule and sediment habitats compared to the water column. Rhodobiaceae family and Vibrio OTUs had higher relative abundance in nodule samples, but were less abundant in sediment and water column samples. Bacterial communities in sediments and associated with nodules were generally similar; however, 5,861 and 6,827 OTUs found in the water column were retrieved from sediment and nodule habitats, respectively. Cyanobacterial OTUs clustering among Prochlorococcus and Synechococcus were detected in both sediments and nodules, with greater representation among nodule samples. Such results suggest that vertical export of typically abundant photic-zone microbes may be an important process in delivery of water column microorganisms to abyssal habitats, potentially influencing the structure and function of communities in polymetallic nodule fields.

  2. Lithogenic fluxes to the deep Arabian Sea measurEd. by sediment traps

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Nair, R.R; Manganini, S.J.; Haake, B.; Ittekkot, V.

    . 38. No. 2. pp 1~g-\\[~44 It,lqt. fllC~g...4)i49tql $31~) 4- 0.till Pnnted m Great Britain. ~ lg~t Pergamon Press pie Lithogenic fluxes to the deep Arabian Sea measured by sediment traps V. RAMASWAMY,* R. R. NAIR,* S. MANGANINI,# B. HAAKE~. and V... (MIct, lrdAN et al., 1984). Most of the present suspended sediment discharge is in July and August, during the peak of the southwest monsoon period, with negligible discharge during other times (I'rrEKKO'r and ARAIN, 1986). The Narmada and Tapti...

  3. Contrasting impacts of light reduction on sediment biogeochemistry in deep- and shallow-water tropical seagrass assemblages (Green Island, Great Barrier Reef).

    Science.gov (United States)

    Schrameyer, Verena; York, Paul H; Chartrand, Kathryn; Ralph, Peter J; Kühl, Michael; Brodersen, Kasper Elgetti; Rasheed, Michael A

    2018-05-01

    Seagrass meadows increasingly face reduced light availability as a consequence of coastal development, eutrophication, and climate-driven increases in rainfall leading to turbidity plumes. We examined the impact of reduced light on above-ground seagrass biomass and sediment biogeochemistry in tropical shallow- (∼2 m) and deep-water (∼17 m) seagrass meadows (Green Island, Australia). Artificial shading (transmitting ∼10-25% of incident solar irradiance) was applied to the shallow- and deep-water sites for up to two weeks. While above-ground biomass was unchanged, higher diffusive O 2 uptake (DOU) rates, lower O 2 penetration depths, and higher volume-specific O 2 consumption (R) rates were found in seagrass-vegetated sediments as compared to adjacent bare sand (control) areas at the shallow-water sites. In contrast, deep-water sediment characteristics did not differ between bare sand and vegetated sites. At the vegetated shallow-water site, shading resulted in significantly lower hydrogen sulphide (H 2 S) levels in the sediment. No shading effects were found on sediment biogeochemistry at the deep-water site. Overall, our results show that the sediment biogeochemistry of shallow-water (Halodule uninervis, Syringodium isoetifolium, Cymodocea rotundata and C. serrulata) and deep-water (Halophila decipiens) seagrass meadows with different species differ in response to reduced light. The light-driven dynamics of the sediment biogeochemistry at the shallow-water site could suggest the presence of a microbial consortium, which might be stimulated by photosynthetically produced exudates from the seagrass, which becomes limited due to lower seagrass photosynthesis under shaded conditions. Copyright © 2018 Elsevier Ltd. All rights reserved.

  4. The Cenozoic western Svalbard margin: sediment geometry and sedimentary processes in an area of ultraslow oceanic spreading

    Science.gov (United States)

    Amundsen, Ingrid Marie Hasle; Blinova, Maria; Hjelstuen, Berit Oline; Mjelde, Rolf; Haflidason, Haflidi

    2011-12-01

    The northeastern high-latitude North Atlantic is characterised by the Bellsund and Isfjorden fans on the continental slope off west Svalbard, the asymmetrical ultraslow Knipovich spreading ridge and a 1,000 m deep rift valley. Recently collected multichannel seismic profiles and bathymetric records now provide a more complete picture of sedimentary processes and depositional environments within this region. Both downslope and alongslope sedimentary processes are identified in the study area. Turbidity currents and deposition of glacigenic debris flows are the dominating downslope processes, whereas mass failures, which are a common process on glaciated margins, appear to have been less significant. The slide debrite observed on the Bellsund Fan is most likely related to a 2.5-1.7 Ma old failure on the northwestern Barents Sea margin. The seismic records further reveal that alongslope current processes played a major role in shaping the sediment packages in the study area. Within the Knipovich rift valley and at the western rift flank accumulations as thick as 950-1,000 m are deposited. We note that oceanic basement is locally exposed within the rift valley, and that seismostratigraphic relationships indicate that fault activity along the eastern rift flank lasted until at least as recently as 1.5 Ma. A purely hemipelagic origin of the sediments in the rift valley and on the western rift flank is unlikely. We suggest that these sediments, partly, have been sourced from the western Svalbard—northwestern Barents Sea margin and into the Knipovich Ridge rift valley before continuous spreading and tectonic activity caused the sediments to be transported out of the valley and westward.

  5. Numerical investigations of the fluid flows at deep oceanic and arctic permafrost-associated gas hydrate deposits

    Science.gov (United States)

    Frederick, Jennifer Mary

    older than the host sediment. Old pore fluid age may reflect complex flow patterns, such a fluid focusing, which can cause significant lateral migration as well as regions where downward flow reverses direction and returns toward the seafloor. Longer pathlines can produce pore fluid ages much older than that expected with a one-dimensional compaction model. For steady-state models with geometry representative of Blake Ridge (USA), a well-studied hydrate province, pore fluid ages beneath regions of topography and within fractured zones can be up to 70 Ma old. Results suggest that the measurements of 129-I/127-I reflect a mixture of new and old pore fluid. However, old pore fluid need not originate at great depths. Methane within pore fluids can travel laterally several kilometers, implying an extensive source region around the deposit. Iodine age measurements support the existence of fluid focusing beneath regions of seafloor topography at Blake Ridge, and suggest that the methane source at Blake Ridge is likely shallow. The response of methane hydrate reservoirs to warming is poorly understood. The great depths may protect deep oceanic hydrates from climate change for the time being because transfer of heat by conduction is slow, but warming will eventually be felt albeit in the far future. On the other hand, unique permafrost-associated methane hydrate deposits exist at shallow depths within the sediments of the circum-Arctic continental shelves. Arctic hydrates are thought to be a relict of cold glacial periods, aggrading when sea levels are much lower and shelf sediments are exposed to freezing air temperatures. During interglacial periods, rising sea levels flood the shelf, bringing dramatic warming to the permafrost- and hydrate-bearing sediments. Permafrost-associated methane hydrate deposits have been responding to warming since the last glacial maximum ~18 kaBP as a consequence of these natural glacial cycles. This `experiment,' set into motion by nature itself

  6. Biological, physical, nutrients, sediment, and other data from sediment sampler-grab, bottle, and CTD casts in the Arabian Sea, Equatorial Pacific Ocean, Northeast Atlantic Ocean, and Southern Oceans as part of the Long Term Monitoring East-West Flower Garden Banks project from 08 January 1995 to 08 April 1998 (NODC Accession 0001155)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Biological, physical, nutrients, sediment, and other data were collected using sediment sampler-grab, bottle and CTD casts in the Arabian Sea, North/South Pacific...

  7. Archaeal Viruses Contribute to the Novel Viral Assemblage Inhabiting Oceanic, Basalt-Hosted Deep Subsurface Crustal Fluids

    Science.gov (United States)

    Nigro, O. D.; Rappe, M. S.; Jungbluth, S.; Lin, H. T.; Steward, G.

    2015-12-01

    Fluids contained in the basalt-hosted deep subsurface of the world's oceans represent one of the most inaccessible and understudied biospheres on earth. Recent improvements in sampling infrastructure have allowed us to collect large volumes of crustal fluids (~104 L) from Circulation Obviation Retrofit Kits (CORKs) placed in boreholes located on the eastern flank of the Juan de Fuca Ridge (JdFR). We detected viruses within these fluids by TEM and epifluorescence microscopy in samples collected from 2010 to 2014. Viral abundance, determined by epifluorescence counts, indicated that concentrations of viruses in subsurface basement fluids (~105 ml-1) are lower than the overlying seawater, but are higher in abundance than microbial cells in the same samples. Analysis of TEM images revealed distinct viral morphologies (rod and spindle-shaped) that resemble the morphologies of viral families infecting archaea. There are very few, if any, direct observations of these viral morphologies in marine samples, although they have been observed in enrichment cultures and their signature genes detected in metagenomic studies from hydrothermal vents and marine sediments. Analysis of metagenomes from the JdFR crustal fluids revealed sequences with homology to archaeal viruses from the rudiviridae, bicaudaviridae and fuselloviridae. Prokaryotic communities in fluids percolating through the basaltic basement rock of the JdFR flank are distinct from those inhabiting the overlying sediments and seawater. Similarly, our data support the idea that the viral assemblage in these fluids is distinct from viral assemblages in other marine and terrestrial aquatic environments. Our data also suggest that viruses contribute to the mortality of deep subsurface prokaryotes through cell lysis, and viruses may alter the genetic potential of their hosts through the processes of lysogenic conversion and horizontal gene transfer.

  8. Unexpected and novel putative viruses in the sediments of a deep-dark permanently anoxic freshwater habitat

    OpenAIRE

    Borrel, Guillaume; Colombet, Jonathan; Robin, Agnès; Lehours, Anne-Catherine; Prangishvili, David; Sime-Ngando, Télesphore

    2012-01-01

    Morphological diversity, abundance and community structure of viruses were examined in the deep and anoxic sediments of the volcanic Lake Pavin (France). The sediment core, encompassing 130 years of sedimentation, was subsampled every centimeter. High viral abundances were recorded and correlated to prokaryotic densities. Abundances of viruses and prokaryotes decreased with the depth, contrasting the pattern of virus-to-prokaryote ratio. According to fingerprint analyses, the community struct...

  9. Sediment tracing by `customised' magnetic fingerprinting: from the sub-catchment to the ocean scale

    Science.gov (United States)

    Maher, B.

    2009-04-01

    Robust identification of catchment suspended sediment sources is a prerequisite both for understanding sediment delivery processes and targeting of effective mitigation measures. Fine sediment delivery can pose management problems, especially with regard to nutrient run-off and siltation of water courses and bodies. Suspended sediment load constitutes the dominant mode of particulate material loss from catchments but its transport is highly episodic. Identification of suspended sediment sources and fluxes is therefore a prerequisite both for understanding of fluvial geomorphic process and systems and for designing strategies to reduce sediment transport, delivery and yields. Here will be discussed sediment ‘fingerprinting', using the magnetic properties of soils and sediments to characterise sediment sources and transport pathways over a very wide variety of spatial scales, from Lake Bassenthwaite in the English Lake District to the Burdekin River in Queensland and even the North Atlantic Ocean during the last glacial maximum. The applicability of magnetic ‘fingerprinting' to such a range of scales and environments has been significantly improved recently through use of new and site-appropriate magnetic measurement techniques, statistical processing and sample treatment options.

  10. Boldness in a deep sea hermit crab to simulated tactile predator attacks is unaffected by ocean acidification

    Science.gov (United States)

    Kim, Tae Won; Barry, James P.

    2016-09-01

    Despite rapidly growing interest in the effects of ocean acidification on marine animals, the ability of deep-sea animals to acclimate or adapt to reduced pH conditions has received little attention. Deep-sea species are generally thought to be less tolerant of environmental variation than shallow-living species because they inhabit relatively stable conditions for nearly all environmental parameters. To explore whether deep-sea hermit crabs ( Pagurus tanneri) can acclimate to ocean acidification over several weeks, we compared behavioral "boldness," measured as time taken to re-emerge from shells after a simulated predatory attack by a toy octopus, under ambient (pH ˜7.6) and expected future (pH ˜7.1) conditions. The boldness measure for crab behavioral responses did not differ between different pH treatments, suggesting that future deep-sea acidification would not influence anti-predatory behavior. However, we did not examine the effects of olfactory cues released by predators that may affect hermit crab behavior and could be influenced by changes in the ocean carbonate system driven by increasing CO2 levels.

  11. Improving Sediment Transport Prediction by Assimilating Satellite Images in a Tidal Bay Model of Hong Kong

    Directory of Open Access Journals (Sweden)

    Peng Zhang

    2014-03-01

    Full Text Available Numerical models being one of the major tools for sediment dynamic studies in complex coastal waters are now benefitting from remote sensing images that are easily available for model inputs. The present study explored various methods of integrating remote sensing ocean color data into a numerical model to improve sediment transport prediction in a tide-dominated bay in Hong Kong, Deep Bay. Two sea surface sediment datasets delineated from satellite images from the Moderate Resolution Imaging Spectra-radiometer (MODIS were assimilated into a coastal ocean model of the bay for one tidal cycle. It was found that remote sensing sediment information enhanced the sediment transport model ability by validating the model results with in situ measurements. Model results showed that root mean square errors of forecast sediment both at the surface layer and the vertical layers from the model with satellite sediment assimilation are reduced by at least 36% over the model without assimilation.

  12. Dive Activities for Expedition to the Deep Slope 2007 - Office of Ocean Exploration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Information about dive activities were recorded by personnel during the "Expedition to the Deep Slope 2007" expedition, June 4 through July 6, 2007. Additional...

  13. Dive Activities for Expedition to the Deep Slope 2006 - Office of Ocean Exploration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Information about dive activities were recorded by personnel during the "Expedition to the Deep Slope 2006" expedition, May 7 through June 2, 2006. Additional...

  14. Metagenomic analysis and metabolite profiling of deep-sea sediments from the Gulf of Mexico following the Deepwater Horizon oil spill

    Directory of Open Access Journals (Sweden)

    Nikole Elizabeth Kimes

    2013-03-01

    Full Text Available Marine subsurface environments, such as deep-sea sediments, house abundant and diverse microbial communities that are believed to influence large-scale geochemical processes. These processes include the biotransformation and mineralization of numerous petroleum constituents. Thus, microbial communities in the Gulf of Mexico are thought to be responsible for the intrinsic bioremediation of crude oil released by the Deepwater Horizon (DWH oil spill. While hydrocarbon contamination is known to enrich for aerobic, oil-degrading bacteria in deep-seawater habitats, relatively little is known about the response of communities in deep-sea sediments, where low oxygen levels may hinder such a response. Here, we examined the hypothesis that increased hydrocarbon exposure results in an altered sediment microbial community structure that reflects the prospects for oil biodegradation under the prevailing conditions. We explore this hypothesis using metagenomic analysis and metabolite profiling of deep-sea sediment samples following the DWH oil spill. The presence of aerobic microbial communities and associated functional genes was consistent among all samples, whereas, a greater number of Deltaproteobacteria and anaerobic functional genes were found in sediments closest to the DWH blowout site. Metabolite profiling also revealed a greater number of putative metabolites in sediments surrounding the blowout zone relative to a background site located 127 km away. The mass spectral analysis of the putative metabolites revealed that alkylsuccinates remained below detection levels, but a homologous series of benzylsuccinates (with carbon chain lengths from 5 to 10 could be detected. Our findings suggest that increased exposure to hydrocarbons enriches for Deltaproteobacteria, which are known to be capable of anaerobic hydrocarbon metabolism. We also provide evidence for an active microbial community metabolizing aromatic hydrocarbons in deep-sea sediments of the

  15. A new eyeless species of Neanthes (Annelida: Nereididae) associated with a whale-fall community from the deep Southwest Atlantic Ocean

    Science.gov (United States)

    Shimabukuro, Maurício; Santos, Cinthya S. G.; Alfaro-Lucas, Joan M.; Fujiwara, Yoshihiro; Sumida, Paulo Y. G.

    2017-12-01

    A new whale-fall community was discovered in the abyssal SW Atlantic Ocean (4204 m depth) during the Iatá-piúna expedition. Several specimens of a new nereidid were found living in sediments around and immediately below whalebones. This new species, Neanthes shinkai, is described here. The most interesting feature of the new species is the absence of eyes on the prostomium. Although three other deep-sea Neanthes species are also eyeless, the arrangement of paragnaths on the pharynx, the shape of parapodia and the type of neuropodial falcigers chaetae can distinguish N. shinkai n. sp. from these other species. In addition, interspecific comparisons using COI fragment shown a high genetic divergence (23.6-24.9% K2P) from other Neanthes species. Some nereidids have been already known to live in association with deep-sea organic falls and other reducing environments, however this is the first record and description of a Neanthes species in a deep-sea whale-fall community. Observed behavioral and carbon and nitrogen isotopes suggest that N. shinkai n. sp. is an omnivore relying mainly on whale carcass with slightly contribution of chemosynthetic bacterial mats, suggesting that it is an inhabitant of whale-falls from SW Atlantic.

  16. Nitrogen Fixation By Sulfate-Reducing Bacteria in Coastal and Deep-Sea Sediments

    Science.gov (United States)

    Bertics, V. J.; Löscher, C.; Salonen, I.; Schmitz-Streit, R.; Lavik, G.; Kuypers, M. M.; Treude, T.

    2011-12-01

    Sulfate-reducing bacteria (SRB) can greatly impact benthic nitrogen (N) cycling, by for instance inhibiting coupled denitrification-nitrification through the production of sulfide or by increasing the availability of fixed N in the sediment via dinitrogen (N2)-fixation. Here, we explored several coastal and deep-sea benthic habitats within the Atlantic Ocean and Baltic Sea, for the occurrence of N2-fixation mediated by SRB. A combination of different methods including microbial rate measurements of N2-fixation and sulfate reduction, geochemical analyses (porewater nutrient profiles, mass spectrometry), and molecular analyses (CARD-FISH, HISH-SIMS, "nested" PCR, and QPCR) were applied to quantify and identify the responsible processes and organisms, respectively. Furthermore, we looked deeper into the question of whether the observed nitrogenase activity was associated with the final incorporation of N into microbial biomass or whether the enzyme activity served another purpose. At the AGU Fall Meeting, we will present and compare data from numerous stations with different water depths, temperatures, and latitudes, as well as differences in key geochemical parameters, such as organic carbon content and oxygen availability. Current metabolic and molecular data indicate that N2-fixation is occurring in many of these benthic environments and that a large part of this activity may linked to SRB.

  17. Disposal in sea-bed geological formations. Properties of ocean sediments in relation to the disposal of radioactive waste

    International Nuclear Information System (INIS)

    Schultheiss, P.J.; Thomson, J.

    1984-01-01

    Work on the permeability and consolidation characteristics of sediment cores from the north-east Atlantic has shown that each sediment type studied has a unique void ratio/permeability relationship and that the permeability decreases with effective stress more rapidly for fine than for coarser grained material. Significant over-consolidation is also present in Pacific red clays from the deep-sea drilling project. Their permeability is less for a given void ratio than that of their Atlantic counterparts. A theoretical analysis is given of the effects on permeability of deep open burrows revealed by improved core handling techniques. Mineralogy and sediment and water chemistry of six cores from the Nares Abyssal Plain have demonstrated the effects of lateral sediment redistribution and have shown only mildly reducing conditions. Pore water studies on a 4 m Kasten core from Great Meteor East show oxygen falling to zero within 30 cm of the sediment surface

  18. Growth of sulfate reducers in deep-subseafloor sediments stimulated by crustal fluids

    Directory of Open Access Journals (Sweden)

    Katja eFichtel

    2012-02-01

    Full Text Available On a global scale, crustal fluids fuel a substantial part of the deep subseafloor biosphere by providing electron acceptors for microbial respiration. In this study, we examined bacterial cultures from a sediment column of the Juan de Fuca Ridge, Northeast Pacific (IODP Site U1301 which is divided into three distinctive compartments: an upper sulfate-containing zone, formed by bottom-seawater diffusion, a sulfate-depleted zone and a second (~140 m thick sulfate-containing zone influenced by fluid diffusion from the basaltic aquifer. Sulfate reducers were isolated from near-surface and near-basement sediments. All initial enrichments harboured specific communities of heterotrophic microorganisms. Among those, the number of isolated spore-forming Firmicutes decreased from 60% to 21% with sediment depth. Strains affiliated to Desulfosporosinus lacus, Desulfotomaculum sp. and Desulfovibrio aespoeensis were recovered from the upper sediment layers (1.3-9.1 meters below seafloor, mbsf. Several strains of Desulfovibrio indonesiensis and one relative of Desulfotignum balticum were isolated from near-basement sediments (240-262 mbsf. The physiological investigation of strains affiliated to D. aespoeensis, D. indonesiensis and D. balticum indicated that they were all able to use sulfate, thiosulfate and sulfite as electron acceptors. In the presence of sulfate, they grew strain-specifically on a few short-chain n-alcohols and fatty acids, only. The strains fermented either ethanol, pyruvate or betaine. Interestingly, all strains utilized hydrogen and the isolate affiliated to D. indonesiensis even exhibited an autotrophic life-mode. Thus, in the deep subseafloor where organic substrates are limited or hardly degradable, hydrogen might become an essential electron donor. The isolation of non-sporeforming sulfate reducers from fluid-influenced layers indicates that they have survived the long-term burial as active populations even after the separation from

  19. Submersible Data (Dive Trackpoints) for Operation Deep Scope 2005 - Office of Ocean Exploration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Data and information collected by the submersible Johnson Sea-Link I along its track during thirteen dives of the 2005 "Operation Deep Scope" expedition sponsored by...

  20. Occurrence of @iNeogloboquadrina pachyderma@@ new subspecies in the shelf-slope sediments of northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G.A.P.

    ~'N in the Bay of Bengal. Studies of hydrological conditions in the Indian Ocean reveal that the Subtropical Subsurface Water Mass is traceable as far north as the Gulf of Aden, and the Indian Ocean Deep Bottom Water Mass originating in the deepest...

  1. Fossil manganese nodules from Timor: geochemical and radiochemical evidence for deep-sea origin

    International Nuclear Information System (INIS)

    Margolis, S.V.; Fein, C.D.; Glasby, G.P.; Audley-Charles, M.G.

    1978-01-01

    Fossil Mn nodules of Cretaceous age from western Timor exhibit chemical, structural and radioisotope compositions consistent with their being of deep-sea origin. These nodules show characteristics similar to nodules now found at depths of 3,500-5,000 m in the Pacific and Indian Oceans. Slight differences in the fine structure and chemistry of these nodules and modern deep-sea nodules are attributed to diagenetic alteration after uplift of enclosing sediments

  2. Chemosynthetic activity prevails in deep-sea sediments of the Central Indian Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Das, A.; Sujith, P.P.; Mourya, B.S.; Biche, S.U.; LokaBharathi, P.A.

    difference between the results at 4±2°C, 1 atm and 4±2°C, 500 atm. The difference could not be discerned in the time frame used for the experiment (Table 1). C/N ratios, TOC, TIC, LOM and bacterial counts In the CIB sediments, elemental C/N ratios... varied from 0.7 to infinitely large values due to very low levels of total nitrogen. TOC varied from <0.05-1.54%, TIC varied from non detectable in most of the deep-sea sediment to 10% in carbonaceous oozes. LOM varied from 0.025-0.14%. Bacterial...

  3. Dynamics of a Marine Turbine for Deep Ocean Currents

    Directory of Open Access Journals (Sweden)

    Ling-Yuan Chang

    2016-09-01

    Full Text Available For most of the ocean currents, such as the Kuroshio at east Taiwan, the Gulf Stream at east Florida and the Agulhas Current at southeast Africa, the depth of the seabed is generally deeper than one hundred meters, some waters of which can even reach one thousand meters. In such deep waters, the design of the turbine, as well as the anchoring system shall have special features so that existing ocean engineering technologies can be applied and the engineering cost can be lowered. Thus, as regards design, in addition to the analysis of the interaction between turbine and current, priority shall also be given to the design of the anchoring system of the turbine. To address the concerns, the authors propose an ocean turbine featured as follows: (1 it can be anchored in deep waters with a single cable; (2 it can generate high power in a current of moderate flow speed while producing low drag; (3 it can be self-balanced against current disturbance; (4 it is shrouded to enhance power efficiency; (5 the dynamic variations due to the interaction between the turbine and current are small. All of these features are confirmed with the computational results, leading to a detailed design of the turbine structure. If the easy-to-install high-efficiency shrouded turbines, having the capability to self-balance and requiring minimum maintenance effort, are successfully developed, the power supply pressure in Taiwan can be greatly alleviated. The Kuroshio was chosen as the typical current for the present dynamic analysis because, firstly, the flow characteristics of Kuroshio are similar to those of other large-scale currents mentioned above, and secondly, the data of Kuroshio are highly available to us so that a thorough analysis can be done.

  4. Extreme diving behaviour in devil rays links surface waters and the deep ocean

    KAUST Repository

    Thorrold, Simon R.; Afonso, Pedro; Fontes, Jorge; Braun, Camrin D.; Santos, Ricardo S.; Skomal, Gregory B.; Berumen, Michael L.

    2014-01-01

    Ecological connections between surface waters and the deep ocean remain poorly studied despite the high biomass of fishes and squids residing at depths beyond the euphotic zone. These animals likely support pelagic food webs containing a suite

  5. Cold-seep-like macrofaunal communities in organic- and sulfide-rich sediments of the Congo deep-sea fan

    Science.gov (United States)

    Olu, K.; Decker, C.; Pastor, L.; Caprais, J.-C.; Khripounoff, A.; Morineaux, M.; Ain Baziz, M.; Menot, L.; Rabouille, C.

    2017-08-01

    Methane-rich fluids arising from organic matter diagenesis in deep sediment layers sustain chemosynthesis-based ecosystems along continental margins. This type of cold seep develops on pockmarks along the Congo margin, where fluids migrate from deep-buried paleo-channels of the Congo River, acting as reservoirs. Similar ecosystems based on shallow methane production occur in the terminal lobes of the present-day Congo deep-sea fan, which is supplied by huge quantities of primarily terrestrial material carried by turbiditic currents along the 800 km channel, and deposited at depths of up to nearly 5000 m. In this paper, we explore the effect of this carbon enrichment of deep-sea sediments on benthic macrofauna, along the prograding lobes fed by the current active channel, and on older lobes receiving less turbiditic inputs. Macrofaunal communities were sampled using either USNEL cores on the channel levees, or ROV blade cores in the chemosynthesis-based habitats patchily distributed in the active lobe complex. The exceptionally high organic content of the surface sediment in the active lobe complex was correlated with unusual densities of macrofauna for this depth, enhanced by a factor 7-8, compared with those of the older, abandoned lobe, whose sediment carbon content is still higher than in Angola Basin at same depth. Macrofaunal communities, dominated by cossurid polychaetes and tanaids were also more closely related to those colonizing low-flow cold seeps than those of typical deep-sea sediment. In reduced sediments, microbial mats and vesicomyid bivalve beds displayed macrofaunal community patterns that were similar to their cold-seep counterparts, with high densities, low diversity and dominance of sulfide-tolerant polychaetes and gastropods in the most sulfidic habitats. In addition, diversity was higher in vesicomyid bivalve beds, which appeared to bio-irrigate the upper sediment layers. High beta-diversity is underscored by the variability of geochemical

  6. From the Surface to the Deep-Sea: Bacterial Distributions across Polymetallic Nodule Fields in the Clarion-Clipperton Zone of the Pacific Ocean

    Directory of Open Access Journals (Sweden)

    Markus V. Lindh

    2017-09-01

    Full Text Available Marine bacteria regulate fluxes of matter and energy essential for pelagic and benthic organisms and may also be involved in the formation and maintenance of commercially valuable abyssal polymetallic nodules. Future mining of these nodule fields is predicted to have substantial effects on biodiversity and physicochemical conditions in mined areas. Yet, the identity and distributions of bacterial populations in deep-sea sediments and associated polymetallic nodules has received relatively little attention. We examined bacterial communities using high-throughput sequencing of bacterial 16S rRNA gene fragments from samples collected in the water column, sediment, and polymetallic nodules in the Pacific Ocean (bottom depth ≥4,000 m in the eastern Clarion-Clipperton Zone. Operational taxonomic units (OTUs; defined at 99% 16S rRNA gene identity affiliated with JTB255 (Gammaproteobacteria and Rhodospirillaceae (Alphaproteobacteria had higher relative abundances in the nodule and sediment habitats compared to the water column. Rhodobiaceae family and Vibrio OTUs had higher relative abundance in nodule samples, but were less abundant in sediment and water column samples. Bacterial communities in sediments and associated with nodules were generally similar; however, 5,861 and 6,827 OTUs found in the water column were retrieved from sediment and nodule habitats, respectively. Cyanobacterial OTUs clustering among Prochlorococcus and Synechococcus were detected in both sediments and nodules, with greater representation among nodule samples. Such results suggest that vertical export of typically abundant photic-zone microbes may be an important process in delivery of water column microorganisms to abyssal habitats, potentially influencing the structure and function of communities in polymetallic nodule fields.

  7. Numerical modeling of pore-scale phenomena during CO2 sequestration in oceanic sediments

    International Nuclear Information System (INIS)

    Kang, Qinjun; Tsimpanogiannis, Ioannis N.; Zhang, Dongxiao; Lichtner, Peter C.

    2005-01-01

    Direct disposal of liquid CO 2 on the ocean floor is one of the approaches considered for sequestering CO 2 in order to reduce its concentration in the atmosphere. At oceanic depths deeper than approximately 3000 m, liquid CO 2 density is higher than the density of seawater and CO 2 is expected to sink and form a pool at the ocean floor. In addition to chemical reactions between CO 2 and seawater to form hydrate, fluid displacement is also expected to occur within the ocean floor sediments. In this work, we consider two different numerical models for hydrate formation at the pore scale. The first model consists of the Lattice Boltzmann (LB) method applied to a single-phase supersaturated solution in a constructed porous medium. The second model is based on the Invasion Percolation (IP) in pore networks, applied to two-phase immiscible displacement of seawater by liquid CO 2 . The pore-scale results are upscaled to obtain constitutive relations for porosity, both transverse and for the entire domain, and for permeability. We examine deposition and displacement patterns, and changes in porosity and permeability due to hydrate formation, and how these properties depend on various parameters including a parametric study of the effect of hydrate formation kinetics. According to the simulations, the depth of CO 2 invasion in the sediments is controlled by changes in the pore-scale porosity close to the hydrate formation front. (author)

  8. An Ocean Sediment Core-Top Calibration of Foraminiferal (Cibicides) Stable Carbon Isotope Ratios

    Science.gov (United States)

    Schmittner, A.; Mix, A. C.; Lisiecki, L. E.; Peterson, C.; Mackensen, A.; Cartapanis, O. A.

    2015-12-01

    Stable carbon isotope ratios (δ13C) measured on calcium carbonate shells of benthic foraminifera (cibicides) from late Holocene sediments (δ13CCib) are compiled and compared with newly updated datasets of contemporary water-column δ13C observations of dissolved inorganic carbon (δ13CDIC) as the initial core-top calibration of the international Ocean Circulation and CarbonCycling (OC3) project. Using selection criteria based on the spatial distance between samples we find high correlation between δ13CCib and natural (pre-industrial) δ13CDIC, confirming earlier work. However, our analysis reveals systematic differences such as higher (lower) δ13CCib values in the Atlantic (Indian and Pacific) oceans. Regression analyses are impacted by anthropogenic carbon and suggest significant carbonate ion, temperature, and pressure effects, consistent with lab experiments with planktonic foraminifera and theory. The estimated standard error of core-top sediment data is generally σ ~= 0.25 ‰, whereas modern foram data from the South Atlantic indicate larger errors (σ ~= 0.4 ‰).

  9. Persistence profile of polyaromatic hydrocarbons in shallow and deep Gulf waters and sediments: Effect of water temperature and sediment–water partitioning characteristics

    International Nuclear Information System (INIS)

    Tansel, B.; Fuentes, C.; Sanchez, M.; Predoi, K.; Acevedo, M.

    2011-01-01

    Highlights: ► The half-lives of PAHs in the deep waters (over 1000 m) are about twice longer than the shallow areas (100–150 m). ► In the water column, anthracene levels can decrease by 50% within 1–2 days. ► The half-lives of the PAHs in the sediments are significantly longer than those in the water column. ► The half-life of pyrene in the shallow and deep sediments is 9 and 16 years, respectively. - Abstract: Persistence profiles of selected polyaromatic hydrocarbons (PAHs) were analyzed depending on temperature variations in the water column and water–sediment interactions in the Gulf of Mexico. The PAHs studied include anthracene, fluoranthene, pyrene, and chrysene. The half-lives of PAHs in the deep waters (over 1000 m) are about twice as long as those in the shallow areas (100–150 m), and almost 2.5 times as long as those in the top layer (0–10 m) of the water column. The half-lives of the PAHs in the sediments are significantly longer. Among the PAHs studied, chrysene is the most persistent in the water column, and pyrene is the most persistent in the sediments. The half-life of chrysene in the shallow and deep waters is over 2.5 and about 5 years, respectively. For pyrene, the half-life in the shallow and deep sediments is about 9 and 16 years, respectively.

  10. Tracing the Ventilation Pathways of the Deep North Pacific Ocean Using Lagrangian Particles and Eulerian Tracers

    NARCIS (Netherlands)

    Syed, H.A.M.S.; Primeau, F.W.; Deleersnijder, E.L.C.; Heemink, A.W.

    2017-01-01

    Lagrangian forward and backward models are introduced into a coarse-grid ocean global circulation model to trace the ventilation routes of the deep North Pacific Ocean. The random walk aspect in the Lagrangian model is dictated by a rotated isopycnal diffusivity tensor in the circulation model,

  11. Viral infections as controlling factors for the deep biosphere? (Invited)

    Science.gov (United States)

    Engelen, B.; Engelhardt, T.; Sahlberg, M.; Cypionka, H.

    2009-12-01

    biogeography? Can viral infections tell us something about the physiological state of indigenous microorganisms? Finally, we will obtain estimates for the viral shunt as an important factor for sustaining the deep biosphere. References: Batzke A, Engelen B, Sass H, Cypionka H (2007) Phylogenetic and physiological diversity of cultured deep-biosphere bacteria from Equatorial Pacific Ocean and Peru Margin sediments. Geomicrobiology J 24:261-273 Danovaro R, Dell'Anno A, Corinaldesi C, Magagnini M, Noble R, Tamburini C, Weinbauer M (2008) Major viral impact on the functioning of benthic deep-sea ecosystems. Nature 454: 1084-U1027.

  12. A geotechnical investigation of a deep ocean site

    International Nuclear Information System (INIS)

    Freeman, T.J.; Schuttenhelm, R.T.E.

    1990-01-01

    A site investigation in deep water often relies solely on laboratory tests to evaluate the geotechnical properties of the sediments. This imposes two fundamental limitations on the investigation: The maximum depth to which the properties can be profiled and the uncertainty of sample disturbance and de-pressurization effects on the measured data. This paper uses results from investigations performed in a water depth of 5.4 km at an abyssal plain site, Great Meteor East (GME), to illustrate how ambiguities can arise in laboratory measurements of strength, and discusses how a simple in-situ test, the expendable penetrator, can be used to corroborate the laboratory data

  13. Diversity, abundance and distribution of amoA-encoding archaea in deep-sea methane seep sediments of the Okhotsk Sea.

    Science.gov (United States)

    Dang, Hongyue; Luan, Xi-Wu; Chen, Ruipeng; Zhang, Xiaoxia; Guo, Lizhong; Klotz, Martin G

    2010-06-01

    The ecological characteristics of amoA-encoding archaea (AEA) in deep-sea sediments are largely unsolved. This paper aimed to study the diversity, structure, distribution and abundance of the archaeal community and especially its AEA components in the cold seep surface sediments of the Okhotsk Sea, a marginal sea harboring one of the largest methane hydrate reservoirs in the world. Diverse archaeal 16S rRNA gene sequences were identified, with the majority being related to sequences from other cold seep and methane-rich sediment environments. However, the AEA diversity and abundance were quite low as revealed by amoA gene analyses. Correlation analysis indicates that the abundance of the archaeal amoA genes was correlated with the sediment organic matter content. Thus, it is possible that the amoA-carrying archaea here might utilize organic matter for a living. The affiliation of certain archaeal amoA sequences to the GenBank sequences originally obtained from deep-sea hydrothermal vent environments indicated that the related AEA either have a wide range of temperature adaptation or they have a thermophilic evolutionary history in the modern cold deep-sea sediments of the Okhotsk Sea. The dominance of ammonia-oxidizing bacteria over AEA may indicate that bacteria play a significant role in nitrification in the Okhotsk Sea cold seep sediments.

  14. CO sub(2) and N sub(2) O fluxes from the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Narvekar, P.V.; Naqvi, S.W.A.; DileepKumar, M.

    and the deep water concentrations signify quantities of N sub(2)O to be consumed within the sediments. The northern Indian Ocean as a source of CO sub(2) to the atmosphere is poorly quantified. The N sub(2)O data indicate that the vertical diffusion coefficient...

  15. Carbonate dissolution in the South Atlantic Ocean: evidence from ultrastructure breakdown in Globigerina bulloides

    Science.gov (United States)

    Dittert, Nicolas; Henrich, Rüdiger

    2000-04-01

    Ultrastructure dissolution susceptibility of the planktic foraminifer Globigerina bulloides, carbonate ion content of the water column, calcium carbonate content of the sediment surface, and carbonate/carbon weight percentage ratio derived from sediment surface samples were investigated in order to reconstruct the position of the calcite saturation horizon, the sedimentary calcite lysocline, and the calcium carbonate compensation depth (CCD) in the modern South Atlantic Ocean. Carbonate ion data from the water column refer to the GEOSECS locations 48, 103, and 109 and calcium carbonate data come from 19 GeoB sediment surface samples of 4 transects into the Brazil, the Guinea, and the Cape Basins. We present a new (paleo-) oceanographic tool, namely the Globigerina bulloides dissolution index (BDX). Further, we give evidence (a) for progressive G. bulloides ultrastructural breakdown with increasing carbonate dissolution even above the lysocline; (b) for a sharp BDX increase at the sedimentary lysocline; and (c) for the total absence of this species at the CCD. BDX puts us in the position to distinguish the upper open ocean and the upwelling influenced continental margin above from the deep ocean below the sedimentary lysocline. Carbonate ion data from water column samples, calcite weight percentage data from surface sediment samples, and carbonate/carbon weight percentage ratio appear to be good proxies to confirm BDX. As shown by BDX both the calcite saturation horizon (in the water column) and the sedimentary lysocline (at the sediment-water interface) mark the boundary between the carbonate ion undersaturated and highly corrosive Antarctic Bottom Water and the carbonate ion saturated North Atlantic Deep Water (NADW) of the modern South Atlantic.

  16. Listening to the Deep: Live monitoring of ocean noise and cetacean acoustic signals

    OpenAIRE

    André, Michel; Van der Schaar, Mike Connor Roger Malcolm; Zaugg, Serge Alain; Houégnigan, Ludwig; Sánchez, A.M.; Castell, Joan

    2011-01-01

    The development and broad use of passive acoustic monitoring techniques have the potential to help assessing the large-scale influence of artificial noise on marine organisms and ecosystems. Deep-sea observatories have the potential to play a key role in understanding these recent acoustic changes. LIDO(Listening to the Deep Ocean Environment) is an international project that is allowing the real-time longterm monitoring of marine ambient noise as well as marine mammal sounds at cabled and...

  17. North Atlantic ocean circulation and abrupt climate change during the last glaciation.

    Science.gov (United States)

    Henry, L G; McManus, J F; Curry, W B; Roberts, N L; Piotrowski, A M; Keigwin, L D

    2016-07-29

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ(13)C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change. Copyright © 2016, American Association for the Advancement of Science.

  18. Isoprenoid quinones resolve the stratification of microbial redox processes in a biogeochemical continuum from the photic zone to deep anoxic sediments of the Black Sea.

    Science.gov (United States)

    Becker, Kevin W; Elling, Felix J; Schröder, Jan M; Lipp, Julius S; Goldhammer, Tobias; Zabel, Matthias; Elvert, Marcus; Overmann, Jörg; Hinrichs, Kai-Uwe

    2018-03-09

    The stratified water column of the Black Sea serves as a model ecosystem for studying the interactions of microorganisms with major biogeochemical cycles. Here we provide detailed analysis of isoprenoid quinones to study microbial redox processes in the ocean. In a continuum from the photic zone through the chemocline into deep anoxic sediments of the southern Black Sea, diagnostic quinones and inorganic geochemical parameters indicate niche segregation between redox processes and corresponding shifts in microbial community composition. Quinones specific for oxygenic photosynthesis and aerobic respiration dominate oxic waters, while quinones associated with thaumarchaeal ammonia-oxidation and bacterial methanotrophy, respectively, dominate a narrow interval in suboxic waters. Quinone distributions indicate highest metabolic diversity within the anoxic zone, with anoxygenic photosynthesis being a major process in its photic layer. In the dark anoxic layer, quinone profiles indicate occurrence of bacterial sulfur and nitrogen cycling, archaeal methanogenesis, and archaeal methanotrophy. Multiple novel ubiquinone isomers, possibly originating from unidentified intra-aerobic anaerobes, occur in this zone. The respiration modes found in the anoxic zone continue into shallow subsurface sediments, but quinone abundances rapidly decrease within the upper 50 cm below sea floor, reflecting the transition to lower energy availability. In the deep subseafloor sediments, quinone distributions and geochemical profiles indicate archaeal methanogenesis/methanotrophy and potentially bacterial fermentative metabolisms. We observed that sedimentary quinone distributions track lithology, which supports prior hypotheses that deep biosphere community composition and metabolisms are determined by environmental conditions during sediment deposition. Importance Microorganisms play crucial roles in global biogeochemical cycles. Yet, we have only a fragmentary understanding of the diversity

  19. Timing and preservation mechanism of deglacial pteropod spike from the Andaman Sea, northeastern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sijinkumar, A.V.; Nath, B.N.; Gupta, M.V.S.; Rao, B.R.

    system in the Arabian Sea. Deep-Sea Research II 45, 2225-2252. Milliman, J. S. & Meade, R. H. 1983: World-wide delivery of river sediment to the oceans. Journal of Geology 91, 1-21. Naqvi, W. A., Charles, C. D. & Fairbanks, R. G. 1994: Carbon...

  20. Surface water iron supplies in the Southern Ocean sustained by deep winter mixing

    CSIR Research Space (South Africa)

    Tagliabue, A

    2014-04-01

    Full Text Available Low levels of iron limit primary productivity across much of the Southern Ocean. At the basin scale, most dissolved iron is supplied to surfacewaters from subsurface reservoirs, because land inputs are spatially limited. Deep mixing in winter...

  1. Molecular biological and isotopic biogeochemical prognoses of the nitrification-driven dynamic microbial nitrogen cycle in hadopelagic sediments.

    Science.gov (United States)

    Nunoura, Takuro; Nishizawa, Manabu; Kikuchi, Tohru; Tsubouchi, Taishi; Hirai, Miho; Koide, Osamu; Miyazaki, Junichi; Hirayama, Hisako; Koba, Keisuke; Takai, Ken

    2013-11-01

    There has been much progress in understanding the nitrogen cycle in oceanic waters including the recent identification of ammonia-oxidizing archaea and anaerobic ammonia oxidizing (anammox) bacteria, and in the comprehensive estimation in abundance and activity of these microbial populations. However, compared with the nitrogen cycle in oceanic waters, there are fewer studies concerning the oceanic benthic nitrogen cycle. To further elucidate the dynamic nitrogen cycle in deep-sea sediments, a sediment core obtained from the Ogasawara Trench at a water depth of 9760 m was analysed in this study. The profiles obtained for the pore-water chemistry, and nitrogen and oxygen stable isotopic compositions of pore-water nitrate in the hadopelagic sediments could not be explained by the depth segregation of nitrifiers and nitrate reducers, suggesting the co-occurrence of nitrification and nitrate reduction in the shallowest nitrate reduction zone. The abundance of SSU rRNA and functional genes related to nitrification and denitrification are consistent with the co-occurrence of nitrification and nitrate reduction observed in the geochemical analyses. This study presents the first example of cooperation between aerobic and anaerobic nitrogen metabolism in the deep-sea sedimentary environments. © 2013 Society for Applied Microbiology and John Wiley & Sons Ltd.

  2. The source and distribution of thermogenic dissolved organic matter in the ocean

    Science.gov (United States)

    Dittmar, T.; Suryaputra, I. G. N. A.; Paeng, J.

    2009-04-01

    Thermogenic organic matter (ThOM) is abundant in the environment. ThOM is produced at elevated temperature and pressure in deep sediments and earth's crust, and it is also a residue of fossil fuel and biomass burning ("black carbon"). Because of its refractory character, it accumulates in soils and sediments and, therefore, may sequester carbon from active cycles. It was hypothesized that a significant component of marine dissolved organic matter (DOM) might be thermogenic. Here we present a detailed data set on the distribution of thermogenic DOM in major water masses of the deep and surface ocean. In addition, several potential sources of thermogenic DOM to the ocean were investigated: active seeps of brine fluids in the deep Gulf of Mexico, rivers, estuaries and submarine groundwaters. Studies on deep-sea hydrothermal vents and aerosol deposition are ongoing. All DOM samples were isolated from seawater via solid phase extraction (SPE-DOM). ThOM was quantified in the extracts as benzene-polycarboxylic acids (BPCAs) after nitric acid oxidation via high-performance liquid chromatography and diode array detection (HPLC-DAD). BPCAs are produced exclusively from fused ring systems and are therefore unambiguous molecular tracers for ThOM. In addition to BPCA determination, the molecular composition and structure of ThOM was characterized in detail via ultrahigh resolution mass spectrometry (FT-ICR-MS). All marine and river DOM samples yielded significant amounts of BPCAs. The cold seep system in the deep Gulf of Mexico, but also black water rivers (like the Suwannee River) were particularly rich in ThOM. Up to 10% of total dissolved organic carbon was thermogenic in both systems. The most abundant BPCA was benzene-pentacarboxylic acid (B5CA). The molecular composition of BPCAs and the FT-ICR-MS data indicate a relatively small number (5-8) of fused aromatic rings per molecule. Overall, the molecular BPCA patterns were very similar independent of the source of Th

  3. Assessment of 238Pu and 239+240Pu, in marine sediments of the oceans Atlantic and Pacific of Guatemala

    International Nuclear Information System (INIS)

    Mendez Ochaita, L.

    2000-01-01

    In this investigation samples of marine sediments were taken from 14 places representatives of the oceans coast of Guatemala. For the assesment of 238 Pu and 239+240 Pu in sediments a radiochemical method was used to mineralize sediments and by ionic interchange it was separated from other elements, after that an electrodeposition of plutonium was made in metallic discs. The radioactivity of plutonium was measured by alpha spectrometry system and the alpha spectrums were obtained. The levels of plutonium are not higher than other countries that shown contamination. The contamination of isotope of 239+240 Pu is higher than 238 Pu and the contamination by two isotopes of plutonium is higher in the Atlantic than the Pacific ocean

  4. Unexpected and novel putative viruses in the sediments of a deep-dark permanently anoxic freshwater habitat.

    Science.gov (United States)

    Borrel, Guillaume; Colombet, Jonathan; Robin, Agnès; Lehours, Anne-Catherine; Prangishvili, David; Sime-Ngando, Télesphore

    2012-11-01

    Morphological diversity, abundance and community structure of viruses were examined in the deep and anoxic sediments of the volcanic Lake Pavin (France). The sediment core, encompassing 130 years of sedimentation, was subsampled every centimeter. High viral abundances were recorded and correlated to prokaryotic densities. Abundances of viruses and prokaryotes decreased with the depth, contrasting the pattern of virus-to-prokaryote ratio. According to fingerprint analyses, the community structure of viruses, bacteria and archaea gradually changed, and communities of the surface (0-10 cm) could be discriminated from those of the intermediate (11-27 cm) and deep (28-40 cm) sediment layers. Viral morphotypes similar to virions of ubiquitous dsDNA viruses of bacteria were observed. Exceptional morphotypes, previously never reported in freshwater systems, were also detected. Some of these resembled dsDNA viruses of hyperthermophilic and hyperhalophilic archaea. Moreover, unusual types of spherical and cubic virus-like particles (VLPs) were observed. Infected prokaryotic cells were detected in the whole sediment core, and their vertical distribution correlated with both viral and prokaryotic abundances. Pleomorphic ellipsoid VLPs were visible in filamentous cells tentatively identified as representatives of the archaeal genus Methanosaeta, a major group of methane producers on earth.

  5. Radiological assessment of the disposal of high level radioactive waste on or within the sediments of the deep ocean bed: v. 1

    International Nuclear Information System (INIS)

    Kane, P.

    1987-11-01

    The contract report comprises a main report accompanied by three volumes detailing the probabilistic risk assessments carried out for each proposed mode of HLW emplacement. Following a section describing the methodology employed, the models developed for and used in the assessment are described. Aspects of design, testing and calibration are covered. The data employed are described in relation to components of the disposal system, giving sources and reasons for the distribution used. Uncertainties in model predictions are examined in relation to their origin. Detailed results are presented which illustrate the transport behaviour of radionuclides in deep ocean environments. Conclusions are drawn and recommendations made for further research. (author)

  6. Carbon dioxide, climate and the deep ocean circulation: Carbon chemistry model

    International Nuclear Information System (INIS)

    Menawat, A.S.

    1992-01-01

    The objective of this study was to investigate the role of oceanic carbon chemistry in modulating the atmospheric levels of CO 2 . It is well known that the oceans are the primary sink of the excess carbon pumped into the atmosphere since the beginning of the industrial period. The suspended particulate and the dissolved organic matters in the deep ocean play important roles as carriers of carbon and other elements critical to the fate of CO 2 . In addition, the suspended particulate matter provides sites for oxidation-reduction reactions and microbial activities. The problem is of an intricate system with complex chemical, physical and biological processes. This report describes a methodology to describe the interconversions of different forms of the organic and inorganic nutrients, that may be incorporated in the ocean circulation models. Our approach includes the driving force behind the transfers in addition to balancing the elements. Such thermodynamic considerations of describing the imbalance in the chemical potentials is a new and unique feature of our approach

  7. Titan : A new facility for ultraclean sampling of trace elements and isotopes in the deep oceans in the international Geotraces program

    NARCIS (Netherlands)

    de Baar, H.J.W.; Timmermans, K.R; Laan, P.; De Porto, H.H.; Ober, S.; Blom, J.J.; Bakker, M.C.; Schilling, J; Sarthou, G.; Smit, M. G.; Klunder, M

    2008-01-01

    Towards more rapid ultraclean sampling of deep ocean waters for trace elements, a novel rectangular frame was constructed of titanium, holding two rows of 12 samplers, as well as various sensors. The frame is deployed to deep ocean waters by an 8000 m length Kevlar wire with internal power and

  8. Response to Comment on "Dilution limits dissolved organic carbon utilization in the deep ocean"

    KAUST Repository

    Arrieta, J M; Mayol, E.; Hansman, R. L.; Herndl, G. J.; Dittmar, T.; Duarte, Carlos M.

    2015-01-01

    Our recent finding that dilution limits dissolved organic carbon (DOC) utilization in the deep ocean has been criticized based on the common misconception that lability equates to rapid and complete utilization. Even when considering

  9. Shelf-to-basin iron shuttling enhances vivianite formation in deep Baltic Sea sediments

    Science.gov (United States)

    Reed, Daniel C.; Gustafsson, Bo G.; Slomp, Caroline P.

    2016-01-01

    Coastal hypoxia is a growing and persistent problem largely attributable to enhanced terrestrial nutrient (i.e., nitrogen and phosphorus) loading. Recent studies suggest phosphorus removal through burial of iron (II) phosphates, putatively vivianite, plays an important role in nutrient cycling in the Baltic Sea - the world's largest anthropogenic dead zone - yet the dynamics of iron (II) phosphate formation are poorly constrained. To address this, a reactive-transport model was used to reconstruct the diagenetic and depositional history of sediments in the Fårö basin, a deep anoxic and sulphidic region of the Baltic Sea where iron (II) phosphates have been observed. Simulations demonstrate that transport of iron from shelf sediments to deep basins enhances vivianite formation while sulphide concentrations are low, but that pyrite forms preferentially over vivianite when sulphate reduction intensifies due to elevated organic loading. Episodic reoxygenation events, associated with major inflows of oxic waters, encourage the retention of iron oxyhydroxides and iron-bound phosphorus in sediments, increasing vivianite precipitation as a result. Results suggest that artificial reoxygenation of the Baltic Sea bottom waters could sequester up to 3% of the annual external phosphorus loads as iron (II) phosphates, but this is negligible when compared to potential internal phosphorus loads due to dissolution of iron oxyhydroxides when low oxygen conditions prevail. Thus, enhancing vivianite formation through artificial reoxygenation of deep waters is not a viable engineering solution to eutrophication in the Baltic Sea. Finally, simulations suggest that regions with limited sulphate reduction and hypoxic intervals, such as eutrophic estuaries, could act as important phosphorus sinks by sequestering vivianite. This could potentially alleviate eutrophication in shelf and slope environments.

  10. Nondestructive X-Ray Computed Tomography Analysis of Sediment Cores: A Case Study from the Arctic Ocean

    Science.gov (United States)

    Oti, E.; Polyak, L. V.; Cook, A.; Dipre, G.

    2014-12-01

    Investigation of marine sediment records can help elucidate recent changes in the Arctic Ocean circulation and sea ice conditions. We examine sediment cores from the western Arctic Ocean, representing Late to Early Quaternary age (potentially up to 1 Ma). Previous studies of Arctic sediment cores indicate that interglacial/interstadial periods with relatively high sea levels and reduced ice cover are characterized by vigorous bioturbation, while glacial intervals have little to no bioturbation. Traditional methods for studying bioturbation require physical dissection of the cores, effectively destroying them. To treat this limitation, we evaluate archival sections of the cores using an X-ray Computed Tomography (XCT) scanner, which noninvasively images the sediment cores in three dimensions. The scanner produces density sensitive images suitable for quantitative analysis and for identification of bioturbation based on size, shape, and orientation. We use image processing software to isolate burrows from surrounding sediment, reconstruct them three-dimensionally, and then calculate their surface areas, volumes, and densities. Preliminary analysis of a core extending to the early Quaternary shows that bioturbation ranges from 0 to approximately 20% of the core's volume. In future research, we will quantitatively define the relationship between bioturbation activity and glacial regimes. XCT examination of bioturbation and other sedimentary features has the potential to shed light on paleoceanographic conditions such as sedimentation patterns and food flux. XCT is an alternative, underexplored investigation method that bears implications not only for illustrating paleoclimate variations but also for preserving cores for future, more advanced technologies.

  11. Bacterial profiling of Saharan dust deposition in the Atlantic Ocean using sediment trap moorings – year one results

    Science.gov (United States)

    Munday, Chris; Brummer, Geert-Jan; van der Does, Michelle; Korte, Laura; Stuut, Jan-Berend

    2015-04-01

    Large quantities of dust are transported from the Sahara Desert across the Atlantic Ocean towards the Caribbean each year, with a large portion of it deposited in the ocean. This dust brings an array of minerals, nutrients and organic matter, both living and dead. This input potentially fertilizes phytoplankton growth, with resulting knock-on effects throughout the food chain. The input of terrestrial microbial life may also have an impact on the marine microbial community. The current multi-year project consists of a transect of floating dust collectors and sub-surface sediment traps placed at 12°N across the Atlantic Ocean. Sediment traps are located 1200m and 3500m below the sea surface and all are synchronized to collect samples for a period of two weeks. The aim is to understand the links between dust input and the bacterial community and how this relates to ocean productivity and the carbon cycle. The first set of sediment trap samples were recovered using the RV Pelagia in November 2013 with promising results. Results from 7 sediment traps (three at 1200m and four at 3500m) were obtained. In general, the total mass flux decreased as distance from the source increased and the upper traps generally held more material than those at 3500m. Denaturing Gradient Gel Electrophoresis (DGGE) was used as a screening technique, revealing highly varied profiles, with the upper (1200m) traps generally showing more variation throughout the year. Several samples have been submitted for high throughput DNA sequencing which will identify the variations in these samples.

  12. Distribution and sources of polycyclic aromatic hydrocarbons in surface sediments from the Bering Sea and western Arctic Ocean.

    Science.gov (United States)

    Zhao, Mengwei; Wang, Weiguo; Liu, Yanguang; Dong, Linsen; Jiao, Liping; Hu, Limin; Fan, Dejiang

    2016-03-15

    To analyze the distribution and sources of polycyclic aromatic hydrocarbons (PAHs) and evaluate their potential ecological risks, the concentrations of 16 PAHs were measured in 43 surface sediment samples from the Bering Sea and western Arctic Ocean. Total PAH (tPAH) concentrations ranged from 36.95 to 150.21 ng/g (dry weight). In descending order, the surface sediment tPAH concentrations were as follows: Canada Basin>northern Chukchi Sea>Chukchi Basin>southern Chukchi Sea>Aleutian Basin>Makarov Basin>Bering Sea shelf. The Bering Sea and western Arctic Ocean mainly received PAHs of pyrogenic origin due to pollution caused by the incomplete combustion of fossil fuels. The concentrations of PAHs in the sediments of the study areas did not exceed effects range low (ERL) values. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Moving beyond the age-depth model paradigm in deep-sea palaeoclimate archives: dual radiocarbon and stable isotope analysis on single foraminifera

    Science.gov (United States)

    Lougheed, Bryan C.; Metcalfe, Brett; Ninnemann, Ulysses S.; Wacker, Lukas

    2018-04-01

    Late-glacial palaeoclimate reconstructions from deep-sea sediment archives provide valuable insight into past rapid changes in ocean chemistry. Unfortunately, only a small proportion of the ocean floor with sufficiently high sediment accumulation rate (SAR) is suitable for such reconstructions using the long-standing age-depth model approach. We employ ultra-small radiocarbon (14C) dating on single microscopic foraminifera to demonstrate that the long-standing age-depth model method conceals large age uncertainties caused by post-depositional sediment mixing, meaning that existing studies may underestimate total geochronological error. We find that the age-depth distribution of our 14C-dated single foraminifera is in good agreement with existing bioturbation models only after one takes the possibility of Zoophycos burrowing into account. To overcome the problems associated with the age-depth paradigm, we use the first ever dual 14C and stable isotope (δ18O and δ13C) analysis on single microscopic foraminifera to produce a palaeoclimate time series independent of the age-depth paradigm. This new state of the art essentially decouples single foraminifera from the age-depth paradigm to provide multiple floating, temporal snapshots of ocean chemistry, thus allowing for the successful extraction of temporally accurate palaeoclimate data from low-SAR deep-sea archives. This new method can address large geographical gaps in late-glacial benthic palaeoceanographic reconstructions by opening up vast areas of previously disregarded, low-SAR deep-sea archives to research, which will lead to an improved understanding of the global interaction between oceans and climate.

  14. Moving beyond the age–depth model paradigm in deep-sea palaeoclimate archives: dual radiocarbon and stable isotope analysis on single foraminifera

    Directory of Open Access Journals (Sweden)

    B. C. Lougheed

    2018-04-01

    Full Text Available Late-glacial palaeoclimate reconstructions from deep-sea sediment archives provide valuable insight into past rapid changes in ocean chemistry. Unfortunately, only a small proportion of the ocean floor with sufficiently high sediment accumulation rate (SAR is suitable for such reconstructions using the long-standing age–depth model approach. We employ ultra-small radiocarbon (14C dating on single microscopic foraminifera to demonstrate that the long-standing age–depth model method conceals large age uncertainties caused by post-depositional sediment mixing, meaning that existing studies may underestimate total geochronological error. We find that the age–depth distribution of our 14C-dated single foraminifera is in good agreement with existing bioturbation models only after one takes the possibility of Zoophycos burrowing into account. To overcome the problems associated with the age–depth paradigm, we use the first ever dual 14C and stable isotope (δ18O and δ13C analysis on single microscopic foraminifera to produce a palaeoclimate time series independent of the age–depth paradigm. This new state of the art essentially decouples single foraminifera from the age–depth paradigm to provide multiple floating, temporal snapshots of ocean chemistry, thus allowing for the successful extraction of temporally accurate palaeoclimate data from low-SAR deep-sea archives. This new method can address large geographical gaps in late-glacial benthic palaeoceanographic reconstructions by opening up vast areas of previously disregarded, low-SAR deep-sea archives to research, which will lead to an improved understanding of the global interaction between oceans and climate.

  15. The biomass of the deep-sea benthopelagic plankton

    Science.gov (United States)

    Wishner, K. F.

    1980-04-01

    Deep-sea benthopelagic plankton samples were collected with a specially designed opening-closing net system 10 to 100 m above the bottom in five different oceanic regions at depths from 1000 to 4700 m. Benthopelagic plankton biomasses decrease exponentially with depth. At 1000 m the biomass is about 1% that of the surface zooplankton, at 5000 m about 0.1%. Effects of differences in surface primary productivity on deep-sea plankton biomass are much less than the effect of depth and are detectable only in a few comparisons of extreme oceanic regions. The biomass at 10 m above the bottom is greater than that at 100 m above the bottom (in a three-sample comparison), which could be a consequence of an enriched near-bottom environment. The deep-sea plankton biomass in the Red Sea is anomalously low. This may be due to increased decomposition rates in the warm (22°C) deep Red Sea water, which prevent much detritus from reaching the deep sea. A model of organic carbon utilization in the benthic boundary layer (bottom 100 m), incorporating results from deep-sea sediment trap and respiration studies, indicates that the benthopelagic plankton use only a small amount of the organic carbon flux. A large fraction of the flux is unaccounted for by present estimates of benthic and benthopelagic respiration.

  16. Reconciling surface ocean productivity, export fluxes and sediment composition in a global biogeochemical ocean model

    Directory of Open Access Journals (Sweden)

    M. Gehlen

    2006-01-01

    Full Text Available This study focuses on an improved representation of the biological soft tissue pump in the global three-dimensional biogeochemical ocean model PISCES. We compare three parameterizations of particle dynamics: (1 the model standard version including two particle size classes, aggregation-disaggregation and prescribed sinking speed; (2 an aggregation-disaggregation model with a particle size spectrum and prognostic sinking speed; (3 a mineral ballast parameterization with no size classes, but prognostic sinking speed. In addition, the model includes a description of surface sediments and organic carbon early diagenesis. Model output is compared to data or data based estimates of ocean productivity, pe-ratios, particle fluxes, surface sediment bulk composition and benthic O2 fluxes. Model results suggest that different processes control POC fluxes at different depths. In the wind mixed layer turbulent particle coagulation appears as key process in controlling pe-ratios. Parameterization (2 yields simulated pe-ratios that compare well to observations. Below the wind mixed layer, POC fluxes are most sensitive to the intensity of zooplankton flux feeding, indicating the importance of zooplankton community composition. All model parameters being kept constant, the capability of the model to reproduce yearly mean POC fluxes below 2000 m and benthic oxygen demand does at first order not dependent on the resolution of the particle size spectrum. Aggregate formation appears essential to initiate an intense biological pump. At great depth the reported close to constant particle fluxes are most likely the result of the combined effect of aggregate formation and mineral ballasting.

  17. A unified spectral parameterization for wave breaking: From the deep ocean to the surf zone

    Science.gov (United States)

    Filipot, J.-F.; Ardhuin, F.

    2012-11-01

    A new wave-breaking dissipation parameterization designed for phase-averaged spectral wave models is presented. It combines wave breaking basic physical quantities, namely, the breaking probability and the dissipation rate per unit area. The energy lost by waves is first explicitly calculated in physical space before being distributed over the relevant spectral components. The transition from deep to shallow water is made possible by using a dissipation rate per unit area of breaking waves that varies with the wave height, wavelength and water depth. This parameterization is implemented in the WAVEWATCH III modeling framework, which is applied to a wide range of conditions and scales, from the global ocean to the beach scale. Wave height, peak and mean periods, and spectral data are validated using in situ and remote sensing data. Model errors are comparable to those of other specialized deep or shallow water parameterizations. This work shows that it is possible to have a seamless parameterization from the deep ocean to the surf zone.

  18. Biodiversity and community composition of sediment macrofauna associated with deep-sea Lophelia pertusa habitats in the Gulf of Mexico

    Science.gov (United States)

    Demopoulos, Amanda W.J.; Bourque, Jill R.; Frometa, Janessy

    2014-01-01

    Scleractinian corals create three-dimensional reefs that provide sheltered refuges, facilitate sediment accumulation, and enhance colonization of encrusting fauna. While heterogeneous coral habitats can harbor high levels of biodiversity, their effect on the community composition within nearby sediments remains unclear, particularly in the deep sea. Sediment macrofauna from deep-sea coral habitats (Lophelia pertusa) and non-coral, background sediments were examined at three sites in the northern Gulf of Mexico (VK826, VK906, MC751, 350–500 m depth) to determine whether macrofaunal abundance, diversity, and community composition near corals differed from background soft-sediments. Macrofaunal densities ranged from 26 to 125 individuals 32 cm−2 and were significantly greater near coral versus background sediments only at VK826. Of the 86 benthic invertebrate taxa identified, 16 were exclusive to near-coral habitats, while 14 were found only in background sediments. Diversity (Fisher’s α) and evenness were significantly higher within near-coral sediments only at MC751 while taxon richness was similar among all habitats. Community composition was significantly different both between near-coral and background sediments and among the three primary sites. Polychaetes numerically dominated all samples, accounting for up to 70% of the total individuals near coral, whereas peracarid crustaceans were proportionally more abundant in background sediments (18%) than in those near coral (10%). The reef effect differed among sites, with community patterns potentially influenced by the size of reef habitat. Taxon turnover occurred with distance from the reef, suggesting that reef extent may represent an important factor in structuring sediment communities near L. pertusa. Polychaete communities in both habitats differed from other Gulf of Mexico (GOM) soft sediments based on data from previous studies, and we hypothesize that local environmental conditions found near L

  19. Biodiversity and community composition of sediment macrofauna associated with deep-sea Lophelia pertusa habitats in the Gulf of Mexico

    Science.gov (United States)

    Demopoulos, Amanda W. J.; Bourque, Jill R.; Frometa, Janessy

    2014-11-01

    Scleractinian corals create three-dimensional reefs that provide sheltered refuges, facilitate sediment accumulation, and enhance colonization of encrusting fauna. While heterogeneous coral habitats can harbor high levels of biodiversity, their effect on the community composition within nearby sediments remains unclear, particularly in the deep sea. Sediment macrofauna from deep-sea coral habitats (Lophelia pertusa) and non-coral, background sediments were examined at three sites in the northern Gulf of Mexico (VK826, VK906, MC751, 350-500 m depth) to determine whether macrofaunal abundance, diversity, and community composition near corals differed from background soft-sediments. Macrofaunal densities ranged from 26 to 125 individuals 32 cm-2 and were significantly greater near coral versus background sediments only at VK826. Of the 86 benthic invertebrate taxa identified, 16 were exclusive to near-coral habitats, while 14 were found only in background sediments. Diversity (Fisher's α) and evenness were significantly higher within near-coral sediments only at MC751 while taxon richness was similar among all habitats. Community composition was significantly different both between near-coral and background sediments and among the three primary sites. Polychaetes numerically dominated all samples, accounting for up to 70% of the total individuals near coral, whereas peracarid crustaceans were proportionally more abundant in background sediments (18%) than in those near coral (10%). The reef effect differed among sites, with community patterns potentially influenced by the size of reef habitat. Taxon turnover occurred with distance from the reef, suggesting that reef extent may represent an important factor in structuring sediment communities near L. pertusa. Polychaete communities in both habitats differed from other Gulf of Mexico (GOM) soft sediments based on data from previous studies, and we hypothesize that local environmental conditions found near L. pertusa

  20. Contribution to the study of sedimentation rates in some french Polynesian lakes and lagoon

    International Nuclear Information System (INIS)

    Serra, C.; Poletiko, C.; Badie, C.

    1991-03-01

    210 Pb measurements using 210 Po deposition technique were performed in several marine and lacustrine sediments of French Polynesia to determine sedimentation rates in lakes and lagoons. Some results in terrigeneous sediments were acceptable and permit rate measurements; on the contrary other sediments, especially coral sands provided a 210 Pb/ 226 Ra disequilibrium (0.33 to 0.69). The occurring phenomena seem to be related to 222 Rn scavenging and geothermal endoupwelling which induces 226 Ra enhancement; this leads to the same 210 Pb/ 226 Ra disequilibrium as in deep ocean waters as described, for instance by Thomson and Turekian (1976) in an upwelling zone on Peru coasts [fr

  1. ESR studies on CaCO3 of deep-sea sediments

    International Nuclear Information System (INIS)

    Mangini, A.; Segl, M.; Schmitz, W.

    1983-01-01

    We have measured depth profiles of the ESR signals on the calcite fraction in 3 deep-sea sediments with a well-established age stratigraphy and CaCO 3 contents around 50 percent. In the ESR spectra of the foraminifera we observe 3 lines (A, B and C, following Ikeya's notation) two of which (A and C) were analysed as depth profiles. The A signal displays a continuous increase with depth over the time periods covered by the sediment cores of 400,000 and 800,000 a B.P. This suggests that a) the lifetime of the electron traps is long compared to these time intervals and b) the traps as yet unsaturated with electrons. Despite our present ignorance of the nature of the traps, these results might indicate the possible future applicability of ESR as a tool for dating sediment cores over time periods up to 1 Ma. The more prominent C signal displays a linear increase over time periods of 100,000 to 200,000 a. Beyond this age we find an overall increase, on which is superimposed short-term noise of similar amplitude that is unrelated to the 232 Th and CaCO 3 contents. (author)

  2. Unique Prokaryotic Consortia in Geochemically Distinct Sediments from Red Sea Atlantis II and Discovery Deep Brine Pools

    Science.gov (United States)

    Siam, Rania; Mustafa, Ghada A.; Sharaf, Hazem; Moustafa, Ahmed; Ramadan, Adham R.; Antunes, Andre; Bajic, Vladimir B.; Stingl, Uli; Marsis, Nardine G. R.; Coolen, Marco J. L.; Sogin, Mitchell; Ferreira, Ari J. S.; Dorry, Hamza El

    2012-01-01

    The seafloor is a unique environment, which allows insights into how geochemical processes affect the diversity of biological life. Among its diverse ecosystems are deep-sea brine pools - water bodies characterized by a unique combination of extreme conditions. The ‘polyextremophiles’ that constitute the microbial assemblage of these deep hot brines have not been comprehensively studied. We report a comparative taxonomic analysis of the prokaryotic communities of the sediments directly below the Red Sea brine pools, namely, Atlantis II, Discovery, Chain Deep, and an adjacent brine-influenced site. Analyses of sediment samples and high-throughput pyrosequencing of PCR-amplified environmental 16S ribosomal RNA genes (16S rDNA) revealed that one sulfur (S)-rich Atlantis II and one nitrogen (N)-rich Discovery Deep section contained distinct microbial populations that differed from those found in the other sediment samples examined. Proteobacteria, Actinobacteria, Cyanobacteria, Deferribacteres, and Euryarchaeota were the most abundant bacterial and archaeal phyla in both the S- and N-rich sections. Relative abundance-based hierarchical clustering of the 16S rDNA pyrotags assigned to major taxonomic groups allowed us to categorize the archaeal and bacterial communities into three major and distinct groups; group I was unique to the S-rich Atlantis II section (ATII-1), group II was characteristic for the N-rich Discovery sample (DD-1), and group III reflected the composition of the remaining sediments. Many of the groups detected in the S-rich Atlantis II section are likely to play a dominant role in the cycling of methane and sulfur due to their phylogenetic affiliations with bacteria and archaea involved in anaerobic methane oxidation and sulfate reduction. PMID:22916172

  3. Unique prokaryotic consortia in geochemically distinct sediments from Red Sea Atlantis II and discovery deep brine pools.

    Directory of Open Access Journals (Sweden)

    Rania Siam

    Full Text Available The seafloor is a unique environment, which allows insights into how geochemical processes affect the diversity of biological life. Among its diverse ecosystems are deep-sea brine pools - water bodies characterized by a unique combination of extreme conditions. The 'polyextremophiles' that constitute the microbial assemblage of these deep hot brines have not been comprehensively studied. We report a comparative taxonomic analysis of the prokaryotic communities of the sediments directly below the Red Sea brine pools, namely, Atlantis II, Discovery, Chain Deep, and an adjacent brine-influenced site. Analyses of sediment samples and high-throughput pyrosequencing of PCR-amplified environmental 16S ribosomal RNA genes (16S rDNA revealed that one sulfur (S-rich Atlantis II and one nitrogen (N-rich Discovery Deep section contained distinct microbial populations that differed from those found in the other sediment samples examined. Proteobacteria, Actinobacteria, Cyanobacteria, Deferribacteres, and Euryarchaeota were the most abundant bacterial and archaeal phyla in both the S- and N-rich sections. Relative abundance-based hierarchical clustering of the 16S rDNA pyrotags assigned to major taxonomic groups allowed us to categorize the archaeal and bacterial communities into three major and distinct groups; group I was unique to the S-rich Atlantis II section (ATII-1, group II was characteristic for the N-rich Discovery sample (DD-1, and group III reflected the composition of the remaining sediments. Many of the groups detected in the S-rich Atlantis II section are likely to play a dominant role in the cycling of methane and sulfur due to their phylogenetic affiliations with bacteria and archaea involved in anaerobic methane oxidation and sulfate reduction.

  4. Unique prokaryotic consortia in geochemically distinct sediments from Red Sea Atlantis II and discovery deep brine pools.

    KAUST Repository

    Siam, Rania

    2012-08-20

    The seafloor is a unique environment, which allows insights into how geochemical processes affect the diversity of biological life. Among its diverse ecosystems are deep-sea brine pools - water bodies characterized by a unique combination of extreme conditions. The \\'polyextremophiles\\' that constitute the microbial assemblage of these deep hot brines have not been comprehensively studied. We report a comparative taxonomic analysis of the prokaryotic communities of the sediments directly below the Red Sea brine pools, namely, Atlantis II, Discovery, Chain Deep, and an adjacent brine-influenced site. Analyses of sediment samples and high-throughput pyrosequencing of PCR-amplified environmental 16S ribosomal RNA genes (16S rDNA) revealed that one sulfur (S)-rich Atlantis II and one nitrogen (N)-rich Discovery Deep section contained distinct microbial populations that differed from those found in the other sediment samples examined. Proteobacteria, Actinobacteria, Cyanobacteria, Deferribacteres, and Euryarchaeota were the most abundant bacterial and archaeal phyla in both the S- and N-rich sections. Relative abundance-based hierarchical clustering of the 16S rDNA pyrotags assigned to major taxonomic groups allowed us to categorize the archaeal and bacterial communities into three major and distinct groups; group I was unique to the S-rich Atlantis II section (ATII-1), group II was characteristic for the N-rich Discovery sample (DD-1), and group III reflected the composition of the remaining sediments. Many of the groups detected in the S-rich Atlantis II section are likely to play a dominant role in the cycling of methane and sulfur due to their phylogenetic affiliations with bacteria and archaea involved in anaerobic methane oxidation and sulfate reduction.

  5. V isotope composition in modern marine hydrothermal sediments

    Science.gov (United States)

    Wu, F.; Owens, J. D.; Nielsen, S.; German, C. R.; Rachel, M.

    2017-12-01

    Vanadium is multivalence transition metal with two isotopes (51V and 50V). Recent work has shown that large V isotope variations occur with oxygen variations in modern sediments (Wu et al., 2016 and 2017 Goldschmidt Abstracts), providing its potential as a promising proxy for determining low oxygen conditions. However, the development of V isotopes as a proxy to probe past redox conditions requires a comprehensive understanding of the modern oceanic isotopic mass balance. Therein, the scavenging of V from the hydrous iron oxides in hydrothermal fluid has been shown to be an important removal process from seawater (Rudnicki and Elderfield, 1993 GCA) but remains unquantified. In this study, we analyzed V isotopic compositions of metalliferous sediments around the active TAG hydrothermal mound from the mid-Atlantic Ridge (26° degrees North) and the Eastern Pacific Zonal Transect (GEOTRACES EPZT cruise GP16). The TAG sediments deposited as Fe oxyhydroxides from plume fall-out, and have δ51V values between -0.3 to 0‰. The good correlation between Fe and V for these metalliferous sediments indicate that the accumulation of V in these samples is directly related to the deposition of Fe oxyhydroxides, which also control their V isotope signature. The EPZT samples cover 8,000 km in the South Pacific Ocean with sedimentary areas that underlie the Peru upwelling region and the well-oxygenated deep South Pacific Ocean influenced by hydtorthermal plume material from southern East Pacific Rise (EPR). The sediments collected at the east of the EPR have δ51V values between -1.2 to -0.7‰, similar to previous δ51V of oxic sediments. In contrast, the sediments from the west of the EPR have δ51V values (-0.4 to 0‰) similar to hydrothermal sediments from the mid-Atlantic Ridge, indicating the long transportation (more than 4,000 km, Fitzsimmons et al., 2017 NG) of Fe and Mn from hydrothermal plume and their incorporation into sediments have a major impact on the cycle of V

  6. Research on the neutron flux, secular equilibrium of chlorine-36 and groundwater age of the deep quaternary sediments, Hebei plain

    International Nuclear Information System (INIS)

    Dong Yuean; He Ming; Jiang Songsheng; Wu Shaoyong; Jiang Shan

    2001-01-01

    For the study of the neutron flux, secular equilibrium of chlorine-36 in the deep quaternary sediments of Hebei plain, the main chemical composition of water sand and confining bed was determined by neutron activation analysis. The mean neutron flux is 2.79 x 10 -5 cm -2 s -1 which was calculated by the chemical composition of the strata. The mean 36 Cl/Cl ratio in secular equilibrium is 1.27 x 10 -14 in the deep quaternary sediments, Hebei Plain. For the study of the groundwater age of the deep Quaternary sediments of Hebei Plain, the 36 Cl/Cl ratio of groundwater samples were determined by tandem accelerator mass spectrometry. The mixed groundwater 36 Cl/Cl ratio of the second and the third aquifer of Quaternary sediments in Baoding district is 247 x 10 -15 , that of the fourth aquifer in Baoding city is 224 x 10 -15 and the third aquifer in Cangzhou district is 40.5 x 10 -15 . The groundwater age of Baoding district was young and that of the third aquifer in Cangzhou was 229.2 ka

  7. Enhanced ocean carbon storage from anaerobic alkalinity generation in coastal sediments

    Directory of Open Access Journals (Sweden)

    H. Thomas

    2009-02-01

    Full Text Available The coastal ocean is a crucial link between land, the open ocean and the atmosphere. The shallowness of the water column permits close interactions between the sedimentary, aquatic and atmospheric compartments, which otherwise are decoupled at long time scales (≅ 1000 yr in the open oceans. Despite the prominent role of the coastal oceans in absorbing atmospheric CO2 and transferring it into the deep oceans via the continental shelf pump, the underlying mechanisms remain only partly understood. Evaluating observations from the North Sea, a NW European shelf sea, we provide evidence that anaerobic degradation of organic matter, fuelled from land and ocean, generates total alkalinity (AT and increases the CO2 buffer capacity of seawater. At both the basin wide and annual scales anaerobic AT generation in the North Sea's tidal mud flat area irreversibly facilitates 7–10%, or taking into consideration benthic denitrification in the North Sea, 20–25% of the North Sea's overall CO2 uptake. At the global scale, anaerobic AT generation could be accountable for as much as 60% of the uptake of CO2 in shelf and marginal seas, making this process, the anaerobic pump, a key player in the biological carbon pump. Under future high CO2 conditions oceanic CO2 storage via the anaerobic pump may even gain further relevance because of stimulated ocean productivity.

  8. Late Cretaceous and Cenozoic seafloor and oceanic basement roughness: Spreading rate, crustal age and sediment thickness correlations

    Science.gov (United States)

    Bird, Robert T.; Pockalny, Robert A.

    1994-05-01

    Single-channel seismic data from the South Australian Basin and Argentine Basin, and bathymetry data from the flanks of the Mid-Atlantic Ridge, East Pacific Rise and Southwest Indian Ridge are analysed to determine the root-mean-square (RMS) roughness of the seafloor and oceanic basement created at seafloor spreading rates ranging from 3 to 80 km/Ma (half-rate). For these data, crustal ages range from near zero to 85 Ma and sediment thicknesses range from near zero to over 2 km. Our results are consistent with a negative correlation of basement roughness and spreading rate where roughness decreases dramatically through the slow-spreading regime (oceanic basement roughness and spreading rate appears to have existed since the late Cretaceous for slow and intermediate spreading rates, suggesting that the fundamental processes creating abyssal hill topography may have remained the same for this time period. Basement roughness does not appear to decrease (smooth) with increasing crustal age, and therefore off-ridge degradation of abyssal hill topography by mass wasting is not detected by our data. Seismic data reveal that sediment thickness increases with increasing crustal age in the South Australian Basin and Argentine Basin, but not monotonically and with significant regional variation. We show that minor accumulations of sediment can affect roughness significantly. Average sediment accumulations of less that 50 m (for our 100 km long sample seismic profiles and half-spreading rates ocean ridges.

  9. Hydrovolcanic activity in the Central Indian Ocean Basin. Does nature mimic laboratory experiments?

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; ShyamPrasad, M.; Gupta, S.M.; Charan, S.N; Mukherjee, A.D.

    of Kilauea Iki, Hawaii (Heiken and Lofgren, 197 l), basaltic hydromagmatic ash (Heiken, 1972; Wohletz, 1983), basaltic microspherules from the eastern Pacific Ocean (#l 1, Table 2; Melson et al., 1988) and the basaltic microlapilli from the Pacific Ocean.... Craters, calderas and hyaloclastites on young Pacific seamounts. J. Geophys. Res. 89, 8371-8390. Blanchard, M.B., Brownlee, D.E., Bunch, T.E., Hodge, P.W.. Kyte, F.T., 1980. Meteoroid ablation spheres from deep-sea sediments. Earth Planet. Sci. Lett...

  10. Mixed layer depth calculation in deep convection regions in ocean numerical models

    Science.gov (United States)

    Courtois, Peggy; Hu, Xianmin; Pennelly, Clark; Spence, Paul; Myers, Paul G.

    2017-12-01

    Mixed Layer Depths (MLDs) diagnosed by conventional numerical models are generally based on a density difference with the surface (e.g., 0.01 kg.m-3). However, the temperature-salinity compensation and the lack of vertical resolution contribute to over-estimated MLD, especially in regions of deep convection. In the present work, we examined the diagnostic MLD, associated with the deep convection of the Labrador Sea Water (LSW), calculated with a simple density difference criterion. The over-estimated MLD led us to develop a new tool, based on an observational approach, to recalculate MLD from model output. We used an eddy-permitting, 1/12° regional configuration of the Nucleus for European Modelling of the Ocean (NEMO) to test and discuss our newly defined MLD. We compared our new MLD with that from observations, and we showed a major improvement with our new algorithm. To show the new MLD is not dependent on a single model and its horizontal resolution, we extended our analysis to include 1/4° eddy-permitting simulations, and simulations using the Modular Ocean Model (MOM) model.

  11. Impacts of the Deepwater Horizon oil spill on deep-sea coral-associated sediment communities

    Science.gov (United States)

    Demopoulos, Amanda W.J.; Bourque, Jill R.; Cordes, Erik E.; Stamler, Katherine

    2016-01-01

    Cold-water corals support distinct populations of infauna within surrounding sediments that provide vital ecosystem functions and services in the deep sea. Yet due to their sedentary existence, infauna are vulnerable to perturbation and contaminant exposure because they are unable to escape disturbance events. While multiple deep-sea coral habitats were injured by the 2010 Deepwater Horizon (DWH) oil spill, the extent of adverse effects on coral-associated sediment communities is unknown. In 2011, sediments were collected adjacent to several coral habitats located 6 to 183 km from the wellhead in order to quantify the extent of impact of the DWH spill on infaunal communities. Higher variance in macrofaunal abundance and diversity, and different community structure (higher multivariate dispersion) were associated with elevated hydrocarbon concentrations and contaminants at sites closest to the wellhead (MC294, MC297, and MC344), consistent with impacts from the spill. In contrast, variance in meiofaunal diversity was not significantly related to distance from the wellhead and no other community metric (e.g. density or multivariate dispersion) was correlated with contaminants or hydrocarbon concentrations. Concentrations of polycyclic aromatic hydrocarbons (PAH) provided the best statistical explanation for observed macrofaunal community structure, while depth and presence of fine-grained mud best explained meiofaunal community patterns. Impacts associated with contaminants from the DWH spill resulted in a patchwork pattern of infaunal community composition, diversity, and abundance, highlighting the role of variability as an indicator of disturbance. These data represent a useful baseline for tracking post-spill recovery of these deep-sea communities.

  12. Isolation of sulfate-reducing bacteria from sediments above the deep-subseafloor aquifer.

    Science.gov (United States)

    Fichtel, Katja; Mathes, Falko; Könneke, Martin; Cypionka, Heribert; Engelen, Bert

    2012-01-01

    On a global scale, crustal fluids fuel a large part of the deep-subseafloor biosphere by providing electron acceptors for microbial respiration. In this study, we examined bacterial cultures from sediments of the Juan de Fuca Ridge, Northeast Pacific (IODP Site U1301). The sediments comprise three distinctive compartments: an upper sulfate-containing zone, formed by bottom-seawater diffusion, a sulfate-depleted zone, and a second (∼140 m thick) sulfate-containing zone influenced by fluid diffusion from the basaltic aquifer. In order to identify and characterize sulfate-reducing bacteria, enrichment cultures from different sediment layers were set up, analyzed by molecular screening, and used for isolating pure cultures. The initial enrichments harbored specific communities of heterotrophic microorganisms. Strains affiliated to Desulfosporosinus lacus, Desulfotomaculum sp., and Desulfovibrio aespoeensis were isolated only from the top layers (1.3-9.1 meters below seafloor, mbsf), while several strains of Desulfovibrio indonesiensis and a relative of Desulfotignum balticum were obtained from near-basement sediments (240-262 mbsf). Physiological tests on three selected strains affiliated to Dv. aespoeensis, Dv. indonesiensis, and Desulfotignum balticum indicated that all reduce sulfate with a limited number of short-chain n-alcohols or fatty acids and were able to ferment either ethanol, pyruvate, or betaine. All three isolates shared the capacity of growing chemolithotrophically with H(2) as sole electron donor. Strain P23, affiliating with Dv. indonesiensis, even grew autotrophically in the absence of any organic compounds. Thus, H(2) might be an essential electron donor in the deep-subseafloor where the availability of organic substrates is limited. The isolation of non-sporeforming sulfate reducers from fluid-influenced layers indicates that they have survived the long-term burial as active populations even after the separation from the seafloor hundreds

  13. Benthic protists and fungi of Mediterranean deep hypsersaline anoxic basin redoxcline sediments.

    Science.gov (United States)

    Bernhard, Joan M; Kormas, Konstantinos; Pachiadaki, Maria G; Rocke, Emma; Beaudoin, David J; Morrison, Colin; Visscher, Pieter T; Cobban, Alec; Starczak, Victoria R; Edgcomb, Virginia P

    2014-01-01

    Some of the most extreme marine habitats known are the Mediterranean deep hypersaline anoxic basins (DHABs; water depth ∼3500 m). Brines of DHABs are nearly saturated with salt, leading many to suspect they are uninhabitable for eukaryotes. While diverse bacterial and protistan communities are reported from some DHAB water-column haloclines and brines, the existence and activity of benthic DHAB protists have rarely been explored. Here, we report findings regarding protists and fungi recovered from sediments of three DHAB (Discovery, Urania, L' Atalante) haloclines, and compare these to communities from sediments underlying normoxic waters of typical Mediterranean salinity. Halocline sediments, where the redoxcline impinges the seafloor, were studied from all three DHABs. Microscopic cell counts suggested that halocline sediments supported denser protist populations than those in adjacent control sediments. Pyrosequencing analysis based on ribosomal RNA detected eukaryotic ribotypes in the halocline sediments from each of the three DHABs, most of which were fungi. Sequences affiliated with Ustilaginomycotina Basidiomycota were the most abundant eukaryotic signatures detected. Benthic communities in these DHABs appeared to differ, as expected, due to differing brine chemistries. Microscopy indicated that only a low proportion of protists appeared to bear associated putative symbionts. In a considerable number of cases, when prokaryotes were associated with a protist, DAPI staining did not reveal presence of any nuclei, suggesting that at least some protists were carcasses inhabited by prokaryotic scavengers.

  14. Vertical suspsended sediment fluxes observed from ocean gliders

    Science.gov (United States)

    Merckelbach, Lucas; Carpenter, Jeffrey

    2016-04-01

    Many studies trying to understand a coastal system in terms of sediment transport paths resort to numerical modelling - combining circulation models with sediment transport models. Two aspects herein are crucial: sediment fluxes across the sea bed-water column interface, and the subsequent vertical mixing by turbulence. Both aspects are highly complex and have relatively short time scales, so that the processes involved are implemented in numerical models as parameterisations. Due to the effort required to obtain field observations of suspended sediment concentrations (and other parameters), measurements are scarce, which makes the development and tuning of parameterisations a difficult task. Ocean gliders (autonomous underwater vehicles propelled by a buoyancy engine) provide a platform complementing more traditional methods of sampling. In this work we present observations of suspended sediment concentration (SSC) and dissipation rate taken by two gliders, each equipped with optical sensors and a microstructure sensor, along with current observations from a bottom mounted ADCP, all operated in the German Bight sector of the North Sea in Summer 2014. For about two weeks of a four-week experiment, the gliders were programmed to fly in a novel way as Lagrangian profilers to water depths of about 40 m. The benefit of this approach is that the rate of change of SSC - and other parameters - is local to the water column, as opposed to an unknown composition of temporal and spatial variability when gliders are operated in the usual way. Therefore, vertical sediment fluxes can be calculated without the need of the - often dubious - assumption that spatial variability can be neglected. During the experiment the water column was initially thermally stratified, with a cross-pycnocline diffusion coefficient estimated at 7\\cdot10-5 m2 s-1. Halfway through the experiment the remnants of tropical storm Bertha arrived at the study site and caused a complete mixing of the water

  15. Modern and ancient geochemical constraints on Proterozoic atmosphere-ocean redox evolution

    Science.gov (United States)

    Hardisty, D. S.; Horner, T. J.; Wankel, S. D.; Lu, Z.; Lyons, T.; Nielsen, S.

    2017-12-01

    A detailed understanding of the spatiotemporal oxygenation of Earth's atmosphere-ocean system through the Precambrian has important implications for the environments capable of sustaining early eukaryotic life and the evolving oxidant budget of subducted sediments. Proxy records suggest an anoxic Fe-rich deep ocean through much of the Precambrian and atmospheric and surface-ocean oxygenation that started in earnest at the Paleoproterozoic Great Oxidation Event (GOE). The marine photic zone represented the initial site of oxygen production and accumulation via cyanobacteria, yet our understanding of surface-ocean oxygen contents and the extent and timing of oxygen propagation and exchange between the atmosphere and deeper ocean are limited. Here, we present an updated perspective of the constraints on atmospheric, surface-ocean, and deep-ocean oxygen contents starting at the GOE. Our research uses the iodine content of Proterozoic carbonates as a tracer of dissolved iodate in the shallow ocean, a redox-sensitive species quantitatively reduced in modern oxygen minimum zones. We supplement our understanding of the ancient record with novel experiments examining the rates of iodate production from oxygenated marine environments based on seawater incubations. Combining new data from iodine with published shallow marine (Ce anomaly, N isotopes) and atmospheric redox proxies, we provide an integrated view of the vertical redox structure of the atmosphere and ocean across the Proterozoic.

  16. Mössbauer investigations to characterize Fe lattice sites in sheet silicates and Peru Basin deep-sea sediments

    Science.gov (United States)

    Lougear, André; König, Iris; Trautwein, Alfred X.; Suess, Erwin

    A procedure to classify different Fe lattice sites, i.e., OH-group geometries, in the clay mineral content of deep-sea sediments was developed using Mössbauer spectroscopy at low temperature (77 K). This speciation is of interest with regard to the redox behavior, reactivity and color of marine sediments, since substantial iron redox transitions (associated with sediment color change) have been documented for the structural sheet silicate iron. Lattice site classification was achieved for the Fe(II) fraction, all of which is structural clay Fe(II) in the sediments under investigation. Whereas the major part of the Fe(III) is structural clay iron as well, there is a small Fe(III) fraction in oxide minerals. Therefore, further elaboration of the procedure would be required to also achieve lattice site classification for the Fe(III) fraction. Analysis of the Mössbauer spectra is based on computer fits, the input parameters of which were derived from a separate study of Fe(II)-rich pure chlorites. The procedure of classification is qualified to investigate, e.g., in laboratory experiments, the site-specific reaction rates and the effects on sediment color of iron redox transitions in the sheet silicate content of sediments. The new skills were successfully applied in environmental impact studies on the mining of polymetallic nodules from the Peru Basin deep-sea floor.

  17. Hydrothermal signature in the axial-sediments from the Carlsberg Ridge in the northwest Indian Ocean

    Science.gov (United States)

    Yu, Zenghui; Li, Huaiming; Li, Mengxing; Zhai, Shikui

    2018-04-01

    30 sediments grabbed from 24 sites between the equator and 10°N along the Carlsberg Ridge (CR) in the northwest Indian Ocean has been analyzed for bulk chemical compositions. Hydrothermal components in the sediments are identified and characterized. They mainly occur at 6.3°N as sulfide debris and at 3.6°N as both sulfide and high temperature water-rock interaction products. The enrichment of chalcophile elements such as Zn, Cu, Pb and the depletion of alkalis metals such as K and Rb are the typical features of hydrothermal components. High U/Fe, low (Nd/Yb)N and negative Ce anomaly infer the uptake of seawater in the hydrothermal deposits by oxidizing after deposition. However, the general enrichment of Mn in hydrothermal plumed-derived materials is not found in the sediments, which may indicate the limited diffusion of fluids or plumes, at least in the direction along the Carlsberg spreading center. The hydrothermal components show their similarity to the hydrothermal deposits from the Indian Ocean Ridge. At 3.6°N ultramafic rocks or gabbroic intrusions, may be involved in the hydrothermal system.

  18. Vertical structure, biomass and topographic association of deep-pelagic fishes in relation to a mid-ocean ridge system

    Science.gov (United States)

    Sutton, T. T.; Porteiro, F. M.; Heino, M.; Byrkjedal, I.; Langhelle, G.; Anderson, C. I. H.; Horne, J.; Søiland, H.; Falkenhaug, T.; Godø, O. R.; Bergstad, O. A.

    2008-01-01

    The assemblage structure and vertical distribution of deep-pelagic fishes relative to a mid-ocean ridge system are described from an acoustic and discrete-depth trawling survey conducted as part of the international Census of Marine Life field project MAR-ECO . The 36-station, zig-zag survey along the northern Mid-Atlantic Ridge (MAR; Iceland to the Azores) covered the full depth range (0 to >3000 m), from the surface to near the bottom, using a combination of gear types to gain a more comprehensive understanding of the pelagic fauna. Abundance per volume of deep-pelagic fishes was highest in the epipelagic zone and within the benthic boundary layer (BBL; 0-200 m above the seafloor). Minimum fish abundance occurred at depths below 2300 m but above the BBL. Biomass per volume of deep-pelagic fishes over the MAR reached a maximum within the BBL, revealing a previously unknown topographic association of a bathypelagic fish assemblage with a mid-ocean ridge system. With the exception of the BBL, biomass per volume reached a water column maximum in the bathypelagic zone between 1500 and 2300 m. This stands in stark contrast to the general "open-ocean" paradigm that biomass decreases exponentially from the surface downwards. As much of the summit of the MAR extends into this depth layer, a likely explanation for this mid-water maximum is ridge association. Multivariate statistical analyses suggest that the dominant component of deep-pelagic fish biomass over the northern MAR was a wide-ranging bathypelagic assemblage that was remarkably consistent along the length of the ridge from Iceland to the Azores. Integrating these results with those of previous studies in oceanic ecosystems, there appears to be adequate evidence to conclude that special hydrodynamic and biotic features of mid-ocean ridge systems cause changes in the ecological structure of deep-pelagic fish assemblages relative to those at the same depths over abyssal plains. Lacking terrigenous input of

  19. The down canyon evolution of submarine sediment density flows

    Science.gov (United States)

    Parsons, D. R.; Barry, J.; Clare, M. A.; Cartigny, M.; Chaffey, M. R.; Gales, J. A.; Gwiazda, R.; Maier, K. L.; McGann, M.; Paull, C. K.; O'Reilly, T. C.; Rosenberger, K. J.; Simmons, S.; Sumner, E. J.; Talling, P.; Xu, J.

    2017-12-01

    Submarine density flows, known as turbidity currents, transfer globally significant volumes of terrestrial and shelf sediments, organic carbon, nutrients and fresher-water into the deep ocean. Understanding such flows has wide implications for global organic carbon cycling, the functioning of deep-sea ecosystems, seabed infrastructure hazard assessments, and interpreting geological archives of Earth history. Only river systems transport comparable volumes of sediment over such large areas of the globe. Despite their clear importance, there are remarkably few direct measurements of these oceanic turbidity currents in action. Here we present results from the multi-institution Coordinated Canyon Experiment (CCE) which deployed multiple moorings along the axis of Monterey Canyon (offshore California). An array of six moorings, with downward looking acoustic Doppler current profilers (ADCP) were positioned along the canyon axis from 290 m to 1850 m water depth. The ADCPs reveal the internal flow structure of submarine density flows at each site. We use a novel inversion method to reconstruct the suspended sediment concentration and flow stratification field during each event. Together the six moorings provide the first ever views of the internal structural evolution of turbidity current events as they evolve down system. Across the total 18-month period of deployment at least 15 submarine sediment density flows were measured with velocities up to 8.1 m/sec, with three of these flows extending 50 kms down the canyon beyond the 1850 m water depth mooring. We use these novel data to highlight the controls on ignition, interval structure and collapse of individual events and discuss the implications for the functioning and deposits produced by these enigmatic flows.

  20. 1.5 My benthic foraminiferal B/Ca record of carbonate chemistry in the deep Atlantic: Implications for ocean alkalinity and atmospheric CO2

    Science.gov (United States)

    Rosenthal, Y.; Sosdian, S. M.; Toggweiler, J. R.

    2017-12-01

    Most hypotheses to explain glacial-interglacial changes in atmospheric CO2 invoke shifts in ocean alkalinity explain roughly half the reduction in glacial CO2 via CaCO3 compensatory mechanism. It follows that changes in CaCO3 burial occur in response to an increase in deep ocean respired carbon content. To date our understanding of this process comes from benthic carbon isotope and %CaCO3 records. However, to understand the nature of the ocean's buffering capacity and its role in modulating pCO2, orbitally resolved reconstructions of the deep ocean carbonate system parameters are necessary. Here we present a 1.5 Myr orbitally resolved deep ocean calcite saturation record (ΔCO32-) derived from benthic foraminiferal B/Ca ratios in the North Atlantic. Glacial B/Ca values decline across the mid-Pleistocene transition (MPT) suggesting increased sequestration of carbon in the deep Atlantic. The magnitude, timing, and structure of deep Atlantic Ocean ΔCO32- and %CaCO3 cycles contrast with the small amplitude, anti-phased swings in IndoPacific ΔCO32- and %CaCO3 during the mid-to-late Pleistocene. Increasing corrosivity of the deep Atlantic causes the locus of CaCO3 burial to shift into the equatorial Pacific where the flux of CaCO3 to the seafloor is high enough to establish and maintain a new "hot spot". We propose that the CO32- in the deep IndoPacific rises in response to the same mechanism that keeps the CO32- in the deep Atlantic low and the atmospheric CO2 low. The increase in interglacial atmospheric pCO2 levels following the Mid-Brunhes event ( 400ka) are associated with increased G/IG ΔCO3 amplitude, expressed by a decrease in the glacial ΔCO32- values. We propose the low persistent ΔCO32- levels at Marine Isotope Stage (MIS) 12 set the stage for the high pCO2 levels at MIS 11 via an increase in whole ocean alkalinity followed by enhanced CaCO3 preservation. Based on this, we suggest that the development of classic (`anticorrelated') CaCO3 patterns was

  1. Application of sediment core modelling to interpreting the glacial-interglacial record of Southern Ocean silica cycling

    Directory of Open Access Journals (Sweden)

    A. Ridgwell

    2007-07-01

    Full Text Available Sediments from the Southern Ocean reveal a meridional divide in biogeochemical cycling response to the glacial-interglacial cycles of the late Neogene. South of the present-day position of the Antarctic Polar Front in the Atlantic sector of the Southern Ocean, biogenic opal is generally much more abundant in sediments during interglacials compared to glacials. To the north, an anti-phased relationship is observed, with maximum opal abundance instead occurring during glacials. This antagonistic response of sedimentary properties provides an important model validation target for testing hypotheses of glacial-interglacial change against, particularly for understanding the causes of the concurrent variability in atmospheric CO2. Here, I illustrate a time-dependent modelling approach to helping understand climates of the past by means of the mechanistic simulation of marine sediment core records. I find that a close match between model-predicted and observed down-core changes in sedimentary opal content can be achieved when changes in seasonal sea-ice extent are imposed, whereas the predicted sedimentary response to iron fertilization on its own is not consistent with sedimentary observations. The results of this sediment record model-data comparison supports previous inferences that the changing cryosphere is the primary driver of the striking features exhibited by the paleoceanographic record of this region.

  2. Ocean uptake of carbon dioxide

    International Nuclear Information System (INIS)

    Peng, Tsung-Hung; Takahashi, Taro

    1993-01-01

    Factors controlling the capacity of the ocean for taking up anthropogenic C0 2 include carbon chemistry, distribution of alkalinity, pCO 2 and total concentration of dissolved C0 2 , sea-air pCO 2 difference, gas exchange rate across the sea-air interface, biological carbon pump, ocean water circulation and mixing, and dissolution of carbonate in deep sea sediments. A general review of these processes is given and models of ocean-atmosphere system based on our understanding of these regulating processes axe used to estimate the magnitude of C0 2 uptake by the ocean. We conclude that the ocean can absorb up to 35% of the fossil fuel emission. Direct measurements show that 55% Of C0 2 from fossil fuel burning remains in the atmosphere. The remaining 10% is not accounted for by atmospheric increases and ocean uptake. In addition, it is estimated that an amount equivalent to 30% of recent annual fossil fuel emissions is released into the atmosphere as a result of deforestation and farming. To balance global carbon budget, a sizable carbon sink besides the ocean is needed. Storage of carbon in terrestrial biosphere as a result of C0 2 fertilization is a potential candidate for such missing carbon sinks

  3. Experimental studies on the geochemical behaviour of 54-Mn considering coastal and deep sea sediments

    International Nuclear Information System (INIS)

    Guegueniat, P.; Boust, D.; Aprosi, G.

    1986-01-01

    In order to study the geochemical behaviour of 54-Mn in the marine environment (Mn 2+ ) 200 sediments gathered in deep sea and in coastal waters were contaminated experimentally. To correlate the various results, the oxidation processes occuring with or without sediments should be specified. Without sediments, in 'blanks', the deposition rate of 54-Mn on the walls brings into play oxidation developing approximately according to a single order linear function. Consequently, it is characterized by a half-life (time for half 54-Mn to be retained) very similar to a residence time (Tsub(R)). In our water samples, Tsub(R) ranged from 12 to 150 days. (author)

  4. Effects of stratification and fluctuations on sound propagation in the deep ocean

    International Nuclear Information System (INIS)

    March, R.H.

    1979-01-01

    It is noted that even in a homogeneous ocean, the effects of non-thermal noise and sound absorption limit the maximum effective range of detection of acoustic signals from particle cascades to distances of 2 to 10 kilometers, depending on the surface conditions prevailing and the directional characteristics of the detector. In the present paper, the effects of stratification and fluctuations in the sound velocity profile in the deep ocean over distances of this order are examined. Attention is given to two effects of potential significance, refraction and scintillation. It is found that neither effect has any significant consequences at ranges of less than 10 km

  5. Turbulence and finestructure in a deep ocean channel with sill overflow on the mid-Atlantic ridge

    Science.gov (United States)

    Tippenhauer, Sandra; Dengler, Marcus; Fischer, Tim; Kanzow, Torsten

    2015-05-01

    Diapycnal mixing in the deep ocean is known to be much stronger in the vicinity of rough topography of mid-ocean ridges than above abyssal plains. In this study a horizontally profiling microstructure probe attached to an autonomous underwater vehicle (AUV) is used to infer the spatial distribution of the dissipation rate of turbulent kinetic energy (ε) in the central valley of the Mid-Atlantic Ridge. To the authors' knowledge, this is the first successful realization of a horizontal, deep-ocean microstructure survey. More than 22 h of horizontal, near-bottom microstructure data from the Lucky Strike segment (37°N) are presented. The study focuses on a channel with unidirectional sill overflow. Density was found to decrease along the channel following the mean northward flow of 3 to 8 cm/s. The magnitude of the rate of turbulent kinetic energy dissipation was distributed asymmetrically relative to the position of the sill. Elevated dissipation rates were present in a segment 1-4 km downstream (north) of the sill with peak values of 1 ×10-7 W/kg. Large flow speeds and elevated density finestructure were observed within this segment. Lowered hydrographic measurements indicated unstable stratification in the same region. The data indicate that hydraulic control was established at least temporarily. Inside the channel at wavelengths between 1 m and 250 m the slopes of AUV-inferred horizontal temperature gradient spectra were found to be consistent with turbulence in the inertial-convective subrange. Integrated temperature gradient variance in this wavelength interval was consistent with an ε2/3 dependence. The results illustrate that deep-reaching AUVs are a useful tool to study deep ocean turbulence over complex terrain where free-falling and lowered turbulence measurements are inefficient and time-consuming.

  6. A New Sensitive GC-MS-based Method for Analysis of Dipicolinic Acid and Quantifying Bacterial Endospores in Deep Marine Subsurface Sediment

    Science.gov (United States)

    Fang, J.

    2015-12-01

    Marine sediments cover more than two-thirds of the Earth's surface and represent a major part of the deep biosphere. Microbial cells and microbial activity appear to be widespread in these sediments. Recently, we reported the isolation of gram-positive anaerobic spore-forming piezophilic bacteria and detection of bacterial endospores in marine subsurface sediment from the Shimokita coalbed, Japan. However, the modern molecular microbiological methods (e.g., DNA-based microbial detection techniques) cannot detect bacterial endospore, because endospores are impermeable and are not stained by fluorescence DNA dyes or by ribosomal RNA staining techniques such as catalysed reporter deposition fluorescence in situ hybridization. Thus, the total microbial cell abundance in the deep biosphere may has been globally underestimated. This emphasizes the need for a new cultivation independent approach for the quantification of bacterial endospores in the deep subsurface. Dipicolinic acid (DPA, pyridine-2,6-dicarboxylic acid) is a universal and specific component of bacterial endospores, representing 5-15wt% of the dry spore, and therefore is a useful indicator and quantifier of bacterial endospores and permits to estimate total spore numbers in the subsurface biosphere. We developed a sensitive analytical method to quantify DPA content in environmental samples using gas chromatography-mass spectrometry. The method is sensitive and more convenient in use than other traditional methods. We applied this method to analyzing sediment samples from the South China Sea (obtained from IODP Exp. 349) to determine the abundance of spore-forming bacteria in the deep marine subsurface sediment. Our results suggest that gram-positive, endospore-forming bacteria may be the "unseen majority" in the deep biosphere.

  7. Progress toward a Km-scale neutrino detector in the deep ocean

    Energy Technology Data Exchange (ETDEWEB)

    Stokstad, R.G.

    1997-11-01

    The best particles for observing distant objects are photons and neutrinos. Because of the neutrino`s weak interaction cross section, detectors suitable for astronomy must be very large and well shielded from cosmic rays. Eventually, a detector with the order of a square km of effective area will be needed for systematic observations of distant point sources such as active galactic nuclei. Prototype detectors are currently being developed at several sites in the ocean, at Lake Baikal, and in Antarctica. This talk summarizes the status of the projects that use the deep ocean for the detector medium and shielding: DUMAND, NESTOR and ANTARES. Technical developments will be needed for a future km-scale detector; progress on one of these, a digital electronic system, is also described.

  8. Progress toward a Km-scale neutrino detector in the deep ocean

    International Nuclear Information System (INIS)

    Stokstad, R.G.

    1997-11-01

    The best particles for observing distant objects are photons and neutrinos. Because of the neutrino's weak interaction cross section, detectors suitable for astronomy must be very large and well shielded from cosmic rays. Eventually, a detector with the order of a square km of effective area will be needed for systematic observations of distant point sources such as active galactic nuclei. Prototype detectors are currently being developed at several sites in the ocean, at Lake Baikal, and in Antarctica. This talk summarizes the status of the projects that use the deep ocean for the detector medium and shielding: DUMAND, NESTOR and ANTARES. Technical developments will be needed for a future km-scale detector; progress on one of these, a digital electronic system, is also described

  9. Buried in time: Culturable fungi in a deep-sea sediment core from the Chagos Trench, Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Raghukumar, C.; Raghukumar, S.; Sheelu, G.; Gupta, S.M.; Nath, B.N.; Rao, B.R.

    of sediments was determined by the ?Karbonat-Bombe? method (M?ller and Gastner, 1971). The DBD is one among the several physical properties of sediment including porosity and is inversely related to porosity as shown by the equation of Garg (1987... Karbonat-Bombe?, a simple device for the determination of carbonate content in sediments, soils and other material. Neues Jahrbuch Minearalogie, 10, 466-469. Mueller, V., Sengbusch, P. V., 1983. Visualization of aquatic fungi (Chytridiales...

  10. Release pathways for deep seabed disposal of radioactive wastes

    International Nuclear Information System (INIS)

    Anderson, D.R.; Bishop, W.P.; Bowen, V.T.; Brannen, J.P.; Caudle, W.N.; Detry, R.J.; Ewart, T.E.; Hayes, D.E.; Heath, G.R.; Hessler, R.R.; Hollister, C.D.; Keil, K.; McGowan, J.A.; Rohde, R.W.; Schimmel, W.P.; Schuster, C.L.; Silva, A.J.; Smyrl, W.H.; Taft, B.A.; Talbert, D.M.

    1975-01-01

    The concept of disposal of high-level solidified and encapsulated radioactive wastes into the deep sea floor has recently been discussed. Such a scheme has conceptual advantages in that the areas of the mid-plate/mid-gyre regions of the oceans are relatively unproductive biologically and relatively devoid of cataclysmic events, and natural processes there are generally quite slow. Given a lack of singular events, a set of barriers against the dispersion of the radioisotopes may be defined. The inverse of these barriers is the set of mechanisms by which the isotopes are transported from the burial site through the barriers to parts of the ocean of immediate significance to mankind. These include: corrosion of the cask; leaching of the waste material; upward transport of the isotopes with the upward moving pore water (mediated by ion-exchange processes); biological transport through bioturbition in the upper sediment layers and lowest water layer; the slow throughput currents of the deep basins; advection and diffusion through the water column; thermally driven transport through the sediments or the water column; biological transport of incorporated isotopes across the seabed or upward through the water column. In principle, the rates of all these processes are measurable or capable of being estimated. Such estimates are given on the basis of present knowledge of the processes in the deep basins. A methodology is discussed for the analytical treatment of the set of processes to give the amount of the isotopes reaching some part of the environment (e.g., and oceanic regime of immediate significance to man) as a function of time. The authors conclude that disposal in the deep seabed is conceptually attractive because of the stability and predictablity of the environment, but that it is not possible to give a firm estimate of the safety of such a scheme from the current knowledge of the mid-plate/mid-gyre regions. (author)

  11. Sediment Microbial Communities Influenced by Cool Hydrothermal Fluid Migration

    Directory of Open Access Journals (Sweden)

    Laura A. Zinke

    2018-06-01

    Full Text Available Cool hydrothermal systems (CHSs are prevalent across the seafloor and discharge fluid volumes that rival oceanic input from rivers, yet the microbial ecology of these systems are poorly constrained. The Dorado Outcrop on the ridge flank of the Cocos Plate in the northeastern tropical Pacific Ocean is the first confirmed CHS, discharging minimally altered <15°C fluid from the shallow lithosphere through diffuse venting and seepage. In this paper, we characterize the resident sediment microbial communities influenced by cool hydrothermal advection, which is evident from nitrate and oxygen concentrations. 16S rRNA gene sequencing revealed that Thaumarchaea, Proteobacteria, and Planctomycetes were the most abundant phyla in all sediments across the system regardless of influence from seepage. Members of the Thaumarchaeota (Marine Group I, Alphaproteobacteria (Rhodospirillales, Nitrospirae, Nitrospina, Acidobacteria, and Gemmatimonadetes were enriched in the sediments influenced by CHS advection. Of the various geochemical parameters investigated, nitrate concentrations correlated best with microbial community structure, indicating structuring based on seepage of nitrate-rich fluids. A comparison of microbial communities from hydrothermal sediments, seafloor basalts, and local seawater at Dorado Outcrop showed differences that highlight the distinct niche space in CHS. Sediment microbial communities from Dorado Outcrop differ from those at previously characterized, warmer CHS sediment, but are similar to deep-sea sediment habitats with surficial ferromanganese nodules, such as the Clarion Clipperton Zone. We conclude that cool hydrothermal venting at seafloor outcrops can alter the local sedimentary oxidation–reduction pathways, which in turn influences the microbial communities within the fluid discharge affected sediment.

  12. Experimental studies on the geochemical behaviour of 54-Mn considering coastal and deep sea sediments

    International Nuclear Information System (INIS)

    Guegueniat, P.; Boust, D.; Dupont, J.P.; Aprosi, G.

    1985-01-01

    In order to study the geochemical behaviour of 54-Mn in the marine environment (Mn/sup 2+/) 200 sediments gathered in deep sea and in coastal waters were contaminated experimentally. To correlate the various results, the oxidation processes occurring with or without sediments should be specified. During this experimental work, the geochemical behaviour of manganese is dealt with using a radioactive tracer (54-Mn) in the divalent state and sediments collected on french littoral (160) in deep sea (30). The latest data published offer an excellent assessment of research findings on manganese in marine and estuary environments and testify to the interest constantly generated by this subject. It is difficult to establish a priori any predictions on the behaviour of manganese based on the properties of a given environment, notably as concerns redox conditions. The oxidation of manganese was found to be governed by a very slow autocatalysis mechanism capable of being concealed by surface catalyses on mineral phases in suspension or oxidation due to bacteria. The residence time in sea water vary considerably depending on the case from a few days to some tens of years

  13. Patterns and trends of macrobenthic abundance, biomass and production in the deep Arctic Ocean

    Directory of Open Access Journals (Sweden)

    Renate Degen

    2015-08-01

    Full Text Available Little is known about the distribution and dynamics of macrobenthic communities of the deep Arctic Ocean. The few previous studies report low standing stocks and confirm a gradient with declining biomass from the slopes down to the basins, as commonly reported for deep-sea benthos. In this study, we investigated regional differences of faunal abundance and biomass, and made for the first time ever estimates of deep Arctic community production by using a multi-parameter artificial neural network model. The underlying data set combines data from recent field studies with published and unpublished data from the past 20 years, to analyse the influence of water depth, geographical latitude and sea-ice concentration on Arctic benthic communities. We were able to confirm the previously described negative relationship of macrofauna standing stock with water depth in the Arctic deep sea, while also detecting substantial regional differences. Furthermore, abundance, biomass and production decreased significantly with increasing sea-ice extent (towards higher latitudes down to values <200 ind m−2, <65 mg C m−2 and <73 mg C m−2 y−1, respectively. In contrast, stations under the seasonal ice zone regime showed much higher standing stock and production (up to 2500 mg C m−2 y−1, even at depths down to 3700 m. We conclude that particle flux is the key factor structuring benthic communities in the deep Arctic Ocean as it explains both the low values in the ice-covered Arctic basins and the higher values in the seasonal ice zone.

  14. An open ocean record of the Toarcian oceanic anoxic event

    Directory of Open Access Journals (Sweden)

    D. R. Gröcke

    2011-11-01

    Full Text Available Oceanic anoxic events were time intervals in the Mesozoic characterized by widespread distribution of marine organic matter-rich sediments (black shales and significant perturbations in the global carbon cycle. These perturbations are globally recorded in sediments as carbon isotope excursions irrespective of lithology and depositional environment. During the early Toarcian, black shales were deposited on the epi- and pericontinental shelves of Pangaea, and these sedimentary rocks are associated with a pronounced (ca. 7 ‰ negative (organic carbon isotope excursion (CIE which is thought to be the result of a major perturbation in the global carbon cycle. For this reason, the lower Toarcian is thought to represent an oceanic anoxic event (the T-OAE. If the T-OAE was indeed a global event, an isotopic expression of this event should be found beyond the epi- and pericontinental Pangaean localities. To address this issue, the carbon isotope composition of organic matter (δ13Corg of lower Toarcian organic matter-rich cherts from Japan, deposited in the open Panthalassa Ocean, was analysed. The results show the presence of a major (>6 ‰ negative excursion in δ13Corg that, based on radiolarian biostratigraphy, is a correlative of the lower Toarcian negative CIE known from Pangaean epi- and pericontinental strata. A smaller negative excursion in δ13Corg (ca. 2 ‰ is recognized lower in the studied succession. This excursion may, within the current biostratigraphic resolution, represent the excursion recorded in European epicontinental successions close to the Pliensbachian/Toarcian boundary. These results from the open ocean realm suggest, in conjunction with other previously published datasets, that these Early Jurassic carbon cycle perturbations affected the active global reservoirs of the exchangeable carbon cycle (deep marine, shallow marine, atmospheric.

  15. Sediment failures within the Peach Slide (Barra Fan, NE Atlantic Ocean) and relation to the history of the British-Irish Ice Sheet

    Science.gov (United States)

    Owen, Matthew J.; Maslin, Mark A.; Day, Simon J.; Long, David

    2018-05-01

    The Peach Slide is the largest known submarine mass movement on the British continental margin and is situated on the northern flank of the glacigenic Barra Fan. The Barra Fan is located on the northwest British continental margin and is subject to cyclonic ocean circulation, with distinct differences between the circulation during stadial and inter-stadial periods. The fan has experienced growth since continental uplift during the mid-Pliocene, with the majority of sediments deposited during the Pleistocene when the fan was a major depocentre for the British-Irish Ice Sheet (BIIS). Surface and shallow sub-surface morphology of the fan has been mapped using newly digitised archival paper pinger and deep towed boomer sub-bottom profile records, side scan sonar and multibeam echosounder data. This process has allowed the interpretation and mapping of a number of different seismic facies, including: contourites, hemipelagites and debrites. Development of a radiocarbon based age model for the seismic stratigraphy constrains the occurrence of two periods of slope failure: the first at circa 21 ka cal BP, shortly after the BIIS's maximum advance during the deglaciation of the Hebrides Ice Stream; and the second between 12 and 11 ka cal BP at the termination of the Younger Dryas stadial. Comparison with other mass movement events, which have similar geological and oceanographic settings, suggests that important roles are played by contouritic and glacigenic sedimentation, deposited in inter-stadial and stadial periods respectively when different thermohaline regimes and sediment sources dominate. The effect of this switch in sedimentation is to rapidly deposit thick, low permeability, glacigenic layers above contourite and hemipelagite units. This process potentially produced excess pore pressure in the fan sediments and would have increased the likelihood of sediment failure via reduced shear strength and potential liquefaction.

  16. Acoustic measurement of sediment dynamics in the coastal zones using wireless sensor networks

    Science.gov (United States)

    Sudhakaran, A., II; Paramasivam, A.; Seshachalam, S.; A, C.

    2014-12-01

    Analyzing of the impact of constructive or low energy waves and deconstructive or high energy waves in the ocean are very much significant since they deform the geometry of seashore. The deformation may lead to productive result and also to the end of deteriorate damage. Constructive waves results deposition of sediment which widens the beach where as deconstructive waves results erosion which narrows the beach. Validation of historic sediment transportation and prediction of the direction of movement of seashore is essential to prevent unrecoverable damages by incorporating precautionary measurements to identify the factors that influence sediment transportation if feasible. The objective of this study is to propose a more reliable and energy efficient Information and communication system to model the Coastal Sediment Dynamics. Various factors influencing the sediment drift at a particular region is identified. Consequence of source depth and frequency dependencies of spread pattern in the presence of sediments is modeled. Property of source depth and frequency on sensitivity to values of model parameters are determined. Fundamental physical reasons for these sediment interaction effects are given. Shallow to deep water and internal and external wave model of ocean is obtained intended to get acoustic data assimilation (ADA). Signal processing algorithms are used over the observed data to form a full field acoustic propagation model and construct sound speed profile (SSP). The inversions of data due to uncertainties at various depths are compared. The impact of sediment drift over acoustic data is identified. An energy efficient multipath routing scheme Wireless sensor networks (WSN) is deployed for the well-organized communication of data. The WSN is designed considering increased life time, decreased power consumption, free of threats and attacks. The practical data obtained from the efficient system to model the ocean sediment dynamics are evaluated with remote

  17. On the possible ''normalization'' of experimental curves of 230Th vertical distribution in abyssal oceanic sediments

    International Nuclear Information System (INIS)

    Kuznetsov, Yu.V.; Al'terman, Eh.I.; Lisitsyn, A.P.; AN SSSR, Moscow. Inst. Okeanologii)

    1981-01-01

    The possibilities of the method of normalization of experimental ionic curves in reference to dating of abyssal sediments and establishing their accumulation rapidities are studied. The method is based on using correlation between ionic curves extrema and variations of Fe, Mn, C org., and P contents in abyssal oceanic sediments. It has been found that the above method can be successfully applied for correction of 230 Th vertical distribution data obtained by low-background γ-spectrometry. The method leads to most reliable results in those cases when the vertical distribution curves in sediments of elements concentrators of 230 Th are symbasic between themselves. The normalization of experimental ionic curves in many cases gives the possibility to realize the sediment age stratification [ru

  18. Submersible Data (Dive Trackpoints) for Expedition to the Deep Slope 2007 - Office of Ocean Exploration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Data and information collected by the ROV Jason along its track during sixteen dives of the 2007 "Expedition to the Deep Slope" expedition sponsored by the National...

  19. Organic geochemistry of continental margin and deep ocean sediments

    Energy Technology Data Exchange (ETDEWEB)

    Whelan, J.K.; Hunt, J.M.; Eglinton, T.; Dickinson, P.; Johnson, C.; Buxton, L.; Tarafa, M.E.

    1990-08-01

    The objective of this research continues to be the understanding of the complex processes of fossil fuel formation and migration. DOE funded research to date has focused on case histories'' of down-hole well profiles of light hydrocarbons, pyrograms, pyrolysis-GC and -GCMS parameters, and biomarker data from wells in the Louisiana and Texas Gulf Coasts the Alaskan North Slope. In the case of the Alaskan North Slope, geological data and one-dimensional maturation modeling have been integrated in order to better constrain possible source rocks, timing, and migration routes for oil and gas generation and expulsion processes.This period, biomarker analyses and organic petrographic analyses were completed for the Ikpikpuk well. In the case of the Gulf Coast, we have obtained a one-dimensional maturation model of the Cost B-1 well in E. Cameron field of the Louisiana Gulf Coast. The completed E. Cameron data set adds to the enigma of the Gulf Coast oils found on the continental shelf of Louisiana. If significant quantities of the oil are coming from relatively organic lean Tertiary rocks, then non-conventional'' expulsion and migration mechanisms, such as gas dissolved in oil must be invoked to explain the Gulf Coast oils reservoired on the Louisiana continental shelf. We are designing and starting to assemble a hydrous pyrolysis apparatus to follow, the laboratory, rates of generation and expulsion of sediment gases. Initiation of some new research to examine {delta}{sup 13}C of individual compounds from pyrolysis is also described. We are beginning to examine both the laboratory and field data from the Gulf Coast in the context of a Global Basin Research Network (GBRN). The purpose is to better understand subsurface fluid flow processes over geologic time in sedimentary basins and their relation to resource accumulation (i.e., petroleum and metal ores). 58 refs.

  20. Global assessment of benthic nepheloid layers and linkage with upper ocean dynamics

    Science.gov (United States)

    Gardner, Wilford D.; Richardson, Mary Jo; Mishonov, Alexey V.

    2018-01-01

    Global maps of the maximum bottom concentration, thickness, and integrated particle mass in benthic nepheloid layers are published here to support collaborations to understand deep ocean sediment dynamics, linkage with upper ocean dynamics, and assessing the potential for scavenging of adsorption-prone elements near the deep ocean seafloor. Mapping the intensity of benthic particle concentrations from natural oceanic processes also provides a baseline that will aid in quantifying the industrial impact of current and future deep-sea mining. Benthic nepheloid layers have been mapped using 6,392 full-depth profiles made during 64 cruises using our transmissometers mounted on CTDs in multiple national/international programs including WOCE, SAVE, JGOFS, CLIVAR-Repeat Hydrography, and GO-SHIP during the last four decades. Intense benthic nepheloid layers are found in areas where eddy kinetic energy in overlying waters, mean kinetic energy 50 m above bottom (mab), and energy dissipation in the bottom boundary layer are near the highest values in the ocean. Areas of intense benthic nepheloid layers include the Western North Atlantic, Argentine Basin in the South Atlantic, parts of the Southern Ocean and areas around South Africa. Benthic nepheloid layers are weak or absent in most of the Pacific, Indian, and Atlantic basins away from continental margins. High surface eddy kinetic energy is associated with the Kuroshio Current east of Japan. Data south of the Kuroshio show weak nepheloid layers, but no transmissometer data exist beneath the Kuroshio, a deficiency that should be remedied to increase understanding of eddy dynamics in un-sampled and under-sampled oceanic areas.

  1. Deep circulation in the Indian and Pacific Oceans and its implication for the dumping of low-level radioactive waste

    International Nuclear Information System (INIS)

    Harries, J.R.

    1980-06-01

    The complexity of ocean transport processes has meant that the limits for the dumping of low-activity radioactive wastes have had to be based on very simplified models of the oceans. This report discusses the models used to determine dumping limits and contrasts them with the known ocean circulation patterns. The deep circulations of the Indian and Pacific Oceans are reviewed to provide a basis for estimating the possible destinations and likely transit times for dissolved material released at the ocean floor

  2. Internal tides and sediment dynamics in the deep sea-Evidence from radioactive Th-234/U-238 disequilibria

    International Nuclear Information System (INIS)

    Turnewitsch, R.; Turnewitsch, R.; Waniek, J.J.; Reyss, J.L.; Nycander, J.; Lampitt, R.S.

    2008-01-01

    ). These conclusions are supported by the horizontal distribution and magnitude of the modeled total (baro-tropic + baro-clinic) tidal current velocities of the predominating tidal M 2 constituent: on (near-)critical sea mount slopes baro-clinic tides lead to localized [∼ O (1 km)] increases of the overall tidal current velocity by a factor of ∼ 2, thereby pushing the total current velocity well above the threshold for sediment erosion. The results of this and a previous study show that kilometer-scale flow/topography interactions leave a marine geochemical imprint.This imprint may help develop new sediment proxies for there construction of past changes of fluid dynamics in the deep sea, including residual and tidal flow. Sedimentary records controlled by kilometer-scale sea floor elevations are promising systems for there construction of paleo-changes of deep-ocean fluid dynamics. For the sediment-based reconstruction of paleo-parameters other than physical oceanographic ones it may be advisable to avoid kilometer-scale topography altogether. (authors)

  3. Light penetration structures the deep acoustic scattering layers in the global ocean.

    KAUST Repository

    Aksnes, Dag L.; Rø stad, Anders; Kaartvedt, Stein; Martinez, Udane; Duarte, Carlos M.; Irigoien, Xabier

    2017-01-01

    The deep scattering layer (DSL) is a ubiquitous acoustic signature found across all oceans and arguably the dominant feature structuring the pelagic open ocean ecosystem. It is formed by mesopelagic fishes and pelagic invertebrates. The DSL animals are an important food source for marine megafauna and contribute to the biological carbon pump through the active flux of organic carbon transported in their daily vertical migrations. They occupy depths from 200 to 1000 m at daytime and migrate to a varying degree into surface waters at nighttime. Their daytime depth, which determines the migration amplitude, varies across the global ocean in concert with water mass properties, in particular the oxygen regime, but the causal underpinning of these correlations has been unclear. We present evidence that the broad variability in the oceanic DSL daytime depth observed during the Malaspina 2010 Circumnavigation Expedition is governed by variation in light penetration. We find that the DSL depth distribution conforms to a common optical depth layer across the global ocean and that a correlation between dissolved oxygen and light penetration provides a parsimonious explanation for the association of shallow DSL distributions with hypoxic waters. In enhancing understanding of this phenomenon, our results should improve the ability to predict and model the dynamics of one of the largest animal biomass components on earth, with key roles in the oceanic biological carbon pump and food web.

  4. Light penetration structures the deep acoustic scattering layers in the global ocean.

    KAUST Repository

    Aksnes, Dag L.

    2017-05-01

    The deep scattering layer (DSL) is a ubiquitous acoustic signature found across all oceans and arguably the dominant feature structuring the pelagic open ocean ecosystem. It is formed by mesopelagic fishes and pelagic invertebrates. The DSL animals are an important food source for marine megafauna and contribute to the biological carbon pump through the active flux of organic carbon transported in their daily vertical migrations. They occupy depths from 200 to 1000 m at daytime and migrate to a varying degree into surface waters at nighttime. Their daytime depth, which determines the migration amplitude, varies across the global ocean in concert with water mass properties, in particular the oxygen regime, but the causal underpinning of these correlations has been unclear. We present evidence that the broad variability in the oceanic DSL daytime depth observed during the Malaspina 2010 Circumnavigation Expedition is governed by variation in light penetration. We find that the DSL depth distribution conforms to a common optical depth layer across the global ocean and that a correlation between dissolved oxygen and light penetration provides a parsimonious explanation for the association of shallow DSL distributions with hypoxic waters. In enhancing understanding of this phenomenon, our results should improve the ability to predict and model the dynamics of one of the largest animal biomass components on earth, with key roles in the oceanic biological carbon pump and food web.

  5. Environmental conditions outweigh geographical contiguity in determining the similarity of nifH-harboring microbial communities in sediments of two disconnected marginal seas

    Directory of Open Access Journals (Sweden)

    Haixia Zhou

    2016-07-01

    Full Text Available Ecological evidence suggests that heterotrophic diazotrophs fueled by organic carbon respiration in sediments play an important role in marine nitrogen fixation. However, fundamental knowledge about the identities, abundance, diversity, biogeography and controlling environmental factors of nitrogen-fixing communities in open ocean sediments is still elusive. Surprisingly, little is known also about nitrogen-fixing communities in sediments of the more research-accessible marginal seas. Here we report on an investigation of the environmental geochemistry and putative diazotrophic microbiota in the sediments of Bohai Sea, an eutrophic marginal sea of the western Pacific Ocean. Diverse and abundant nifH gene sequences were identified and sulfate-reducing bacteria were found to be the dominant putative nitrogen-fixing microbes. Community statistical analyses suggested bottom water temperature, bottom water chlorophyll a content (or the covarying turbidity and sediment porewater Eh (or the covarying pH as the most significant environmental factors controlling the structure and spatial distribution of the putative diazotrophic communities, while sediment Hg content, sulfide content and porewater SiO32--Si content were identified as the key environmental factors correlated positively with the nifH gene abundance in Bohai Sea sediments. Comparative analyses between the Bohai Sea and the northern South China Sea identified a significant composition difference of the putative diazotrophic communities in sediments between the shallow-water (estuarine and nearshore and deep-water (offshore and deep-sea environments, and sediment porewater dissolved oxygen content, water depth and in situ temperature as the key environmental factors tentatively controlling the species composition, community structure and spatial distribution of the marginal sea sediment nifH-harboring microbiota. This confirms the ecophysiological specialization and niche differentiation

  6. Radioisotope mobility across the sediment/water interface in the deep sea

    International Nuclear Information System (INIS)

    ten Brink, M.R.B.

    1987-01-01

    The removal of radiotracers from water to sediments and their partitioning between phases were used to study the rates and mechanisms of transfer for trace elements across the sediment/water interface in the deep sea. The in situ mobility of 22 Na, 134 Cs, 133 Ba, 65 Zn, 125 Sb, 7 Be, 203 Hg, 54 Mn, 60 Co, 59 Fe, 113 Gd, and 141 Ce was measured using MANOP Lander benthic chambers in the N. equatorial Pacific and in San Clemente Basin. The contributions to mobility of diffusion, bioturbation, advection of pore waters, and transport across the diffusive boundary layer was assessed. The penetration of particle reactive tracers in the upper cm suggested a mixing rate of ≤10 -7 cm 2 /s at Sites C and S and ≤10 -5 cm 2 /s at Sites M and H. Greater penetration could be correlated with worm tubes but no evidence of irrigation was found. The presence of nodules did not prevent transport of soluble tracers to the underlying sediment or concentrate tracers. Diffusion was the predominant mode of transport for radiotracers in the short-term in situ experiments

  7. Analyses of outcrop and sediment grains observed and collected from the Sirena Deep and Middle Pond of the Mariana Trench

    Science.gov (United States)

    Hand, K. P.; Bartlett, D. H.; Fryer, P.

    2012-12-01

    During a March 2012 expedition we recovered sediments from two locales within the Marina Trench - Middle Pond and Sirena Deep. Samples were recovered from a Niskin bottle deployed on a passive lander platform that released an arm after touching down on the seafloor. The impact of the arm holding the Niskin bottle caused sediments to enter the bottle; this process was seen in images and on video captured by the lander. The combination of imagery and preliminary analyses of the sediments indicates that the Sirena Deep locale is a region of serpentinization and active microbial communities. Images show several outcrops consistent with serpentinization, some of which are coated with filamentous microbial mats. Results and analyses of these samples will be presented.

  8. Driving forces and their contribution to the recent decrease in sediment flux to ocean of major rivers in China.

    Science.gov (United States)

    Li, Tong; Wang, Shuai; Liu, Yanxu; Fu, Bojie; Zhao, Wenwu

    2018-09-01

    Understanding the mechanisms behind land-ocean sediment transport processes is crucial, due to the resulting impacts on the sustainable management of water and soil resources. This study investigated temporal trends and historical phases of sediment flux delivered to the sea by nine major rivers in China, while also quantifying the contribution of key anthropogenic and natural driving forces. During the past six decades, sediment flux from these nine major rivers exhibited a statistically significant negative trend, decreasing from 1.92Gtyr -1 during 1954-1968 to 1.39Gtyr -1 , 0.861Gtyr -1 and 0.335Gtyr -1 during 1969-1985, 1986-1999 and 2000-2016, respectively. We used a recently developed Sediment Identity approach and found that the sharp decrease in sediment load observed across China was mainly (~95%) caused by a reduction in sediment concentration. Reservoir construction exerted the strongest influence on land-ocean sediment fluxes, while soil conservation measures represented a secondary driver. Before 1999, soil erosion was not controlled effectively in China and reservoirs, especially large ones, played a dominant role in reducing riverine sediments. After 1999, soil erosion has gradually been brought under control across China, so that conservation measures directly accounted for ~40% of the observed decrease in riverine sediments. With intensifying human activities, it is predicted that the total sediment flux delivered to the sea by the nine major rivers will continue to decrease in the coming decades, although at a slower rate, resulting in severe challenges for the sustainable management of drainage basins and river deltas. Copyright © 2018 Elsevier B.V. All rights reserved.

  9. Reconciling the sea level record of the last deglaciation with the δ18O spectra from deep sea cores

    International Nuclear Information System (INIS)

    Bard, Edouard; Columbia Univ., Palisades, NY; Arnold, Maurice; Duplessy, J.-C.

    1991-01-01

    In this paper we use the oxygen isotope record as a transient tracer to study palaeoceanography during the last deglaciation. By using 14 C and 18 O data obtained on four deep sea sediment cores, we show the presence of a measurable lag between the deglacial δ 18 O signal observed in the deep Atlantic and the deep Indo-Pacific oceans. Our study confirms that the major meltwater discharge occurred via the North Atlantic and that the thermohaline circulation was operating during the deglacial transition. (Author)

  10. Unique prokaryotic consortia in geochemically distinct sediments from Red Sea Atlantis II and discovery deep brine pools.

    KAUST Repository

    Siam, Rania; Mustafa, Ghada A; Sharaf, Hazem; Moustafa, Ahmed; Ramadan, Adham R; Antunes, Andre; Bajic, Vladimir B.; Stingl, Ulrich; Marsis, Nardine G R; Coolen, Marco J L; Sogin, Mitchell; Ferreira, Ari J S; Dorry, Hamza El

    2012-01-01

    )-rich Atlantis II and one nitrogen (N)-rich Discovery Deep section contained distinct microbial populations that differed from those found in the other sediment samples examined. Proteobacteria, Actinobacteria, Cyanobacteria, Deferribacteres, and Euryarchaeota

  11. High occurrence of Bathyarchaeota (MCG) in the deep-sea sediments of South China Sea quantified using newly designed PCR primers.

    Science.gov (United States)

    Yu, Tiantian; Liang, Qianyong; Niu, Mingyang; Wang, Fengping

    2017-08-01

    The archaeal phylum Bathyarchaeota, which is composed of a large number of diverse lineages, is widespread and abundant in marine sediments. Environmental factors that control the distribution, abundance and evolution of this largely diversified archaeal phylum are currently unclear. In this study, a new pair of specific primers that target the major marine subgroups of bathyarchaeotal 16S rRNA genes was designed and evaluated to investigate the distribution and abundance of Bathyarchaeota in marine sediments. The abundance of Bathyarchaeota along two sediment cores from the deep-sea sediments of South China Sea (SCS, each from the Dongsha and Shenhu area) was determined. A strong correlation was found between the bathyarchaeotal abundance and the content of total organic carbon (TOC), suggesting an important role of Bathyarchaeota in organic matter remineralisation in the sediments of SCS. Furthermore, diversity analysis revealed that subgroups Bathy-2, Bathy-8 and Bathy-10 were dominant bathyarchaeotal members of the deep-sea sediments in the SCS. Bathy-8 was found predominantly within the reducing and deeper sediment layers, while Bathy-10 occurred preferentially in the oxidizing and shallower sediment layers. Our study lays a foundation for the further understanding of the ecological functions and niche differentiation of the important but not well-understood sedimentary archaeal group. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  12. Cohesive and mixed sediment in the Regional Ocean Modeling System (ROMS v3.6 implemented in the Coupled Ocean–Atmosphere–Wave–Sediment Transport Modeling System (COAWST r1234

    Directory of Open Access Journals (Sweden)

    C. R. Sherwood

    2018-05-01

    Full Text Available We describe and demonstrate algorithms for treating cohesive and mixed sediment that have been added to the Regional Ocean Modeling System (ROMS version 3.6, as implemented in the Coupled Ocean–Atmosphere–Wave–Sediment Transport Modeling System (COAWST Subversion repository revision 1234. These include the following: floc dynamics (aggregation and disaggregation in the water column; changes in floc characteristics in the seabed; erosion and deposition of cohesive and mixed (combination of cohesive and non-cohesive sediment; and biodiffusive mixing of bed sediment. These routines supplement existing non-cohesive sediment modules, thereby increasing our ability to model fine-grained and mixed-sediment environments. Additionally, we describe changes to the sediment bed layering scheme that improve the fidelity of the modeled stratigraphic record. Finally, we provide examples of these modules implemented in idealized test cases and a realistic application.

  13. Determination of deep water circulation in the East Atlantic Ocean by means of a box-model based evaluation of C-14 measurements and other tracer data

    International Nuclear Information System (INIS)

    Schlitzer, R.

    1984-01-01

    Radiocarbon (C-14) measurements proved to be an efficient means of determining the average, large-area deep water circulation in the Atlantic Ocean. The thesis under review explains and discusses measurements carried out in the equatorial West Atlantic and North Atlantic Ocean. The samples have been taken during mission 56 of the RS 'meteor' in spring 1981. The gas has been obtained by vacuum extraction and the measurements have been performed in proportional counter tubes, the error to be accounted for amounting to 2per mille. These measured data, together with measurements of the potential temperatures, the silicate and CO 2 concentrations, and measured data from the South-East Atlantic Ocean, have been used to calculate on the basis of a box model of the Atlantic Ocean the deep water flow from the West to the East Atlantic Ocean, the deep water circulation between the various East Atlantic basins, and the turbulent diffusion coefficients required to parameterize the deep water mixing processes. (orig./HP) [de

  14. Size and Carbon Content of Sub-seafloor Microbial Cells at Landsort Deep, Baltic Sea

    DEFF Research Database (Denmark)

    Braun, Stefan; Morono, Yuki; Littmann, Sten

    2016-01-01

    determined the volume and the carbon content of microbial cells from a marine sediment drill core retrieved by the Integrated Ocean Drilling Program (IODP), Expedition 347, at Landsort Deep, Baltic Sea. To determine their shape and volume, cells were separated from the sediment matrix by multi-layer density......-specific carbon content was 19–31 fg C cell−1, which is at the lower end of previous estimates that were used for global estimates of microbial biomass. The cell-specific carbon density increased with sediment depth from about 200 to 1000 fg C μm−3, suggesting that cells decrease their water content and grow...... small cell sizes as adaptation to the long-term subsistence at very low energy availability in the deep biosphere. We present for the first time depth-related data on the cell volume and carbon content of sedimentary microbial cells buried down to 60 m below the seafloor. Our data enable estimates...

  15. Ocean acidification buffering effects of seagrass in Tampa Bay

    Science.gov (United States)

    Yates, Kimberly K.; Moyer, Ryan P.; Moore, Christopher; Tomasko, David A.; Smiley, Nathan A.; Torres-Garcia, Legna; Powell, Christina E.; Chappel, Amanda R.; Bociu, Ioana; Smiley, Nathan; Torres-Garcia, Legna M.; Powell, Christina E.; Chappel, Amanda R.; Bociu, Ioana

    2016-01-01

    The Intergovernmental Panel on Climate Change has identified ocean acidification as a critical threat to marine and estuarine species in ocean and coastal ecosystems around the world. However, seagrasses are projected to benefit from elevated atmospheric pCO2, are capable of increasing seawater pH and carbonate mineral saturation states through photosynthesis, and may help buffer against the chemical impacts of ocean acidification. Additionally, dissolution of carbonate sediments may also provide a mechanism for buffering seawater pH. Long-term water quality monitoring data from the Environmental Protection Commission of Hillsborough County indicates that seawater pH has risen since the 1980‘s as seagrass beds have continued to recover since that time. We examined the role of seagrass beds in maintaining and elevating pH and carbonate mineral saturation state in northern and southern Tampa Bay where the percent of carbonate sediments is low (40%), respectively. Basic water quality and carbonate system parameters (including pH, total alkalinity, dissolved inorganic carbon, partial pressure of CO2, and carbonate mineral saturation state) were measured over diurnal time periods along transects (50-100 m) including dense and sparse Thalassia testudinum. seagrass beds, deep edge seagrass, and adjacent bare sand bottom. Seagrass density and productivity, sediment composition and hydrodynamic parameters were also measured, concurrently. Results indicate that seagrass beds locally elevate pH by up to 0.5 pH unit and double carbonate mineral saturation states relative to bare sand habitats. Thus, seagrass beds in Tampa Bay may provide refuge for marine organisms from the impacts of ocean acidification.

  16. High-velocity basal sediment package atop oceanic crust, offshore Cascadia: Impacts on plate boundary processes and fluid migration

    Science.gov (United States)

    Peterson, D. E.; Keranen, K. M.

    2017-12-01

    Differences in fluid pressure and mechanical properties at megathrust boundaries in subduction zones have been proposed to create varying seismogenic behavior. In Cascadia, where large ruptures are possible but little seismicity occurs presently, new seismic transects across the deformation front (COAST cruise; Holbrook et al., 2012) image an unusually high-wavespeed sedimentary unit directly overlying oceanic crust. Wavespeed increases before sediments reach the deformation front, and the well-laminated unit, consistently of 1 km thickness, can be traced for 50 km beneath the accretionary prism before imaging quality declines. Wavespeed is modeled via iterative prestack time migration (PSTM) imaging and increases from 3.5 km/sec on the seaward end of the profile to >5.0 km/s near the deformation front. Landward of the deformation front, wavespeed is low along seaward-dipping thrust faults in the Quaternary accretionary prism, indicative of rapid dewatering along faults. The observed wavespeed of 5.5 km/sec just above subducting crust is consistent with porosity intersects the plate boundary at an oblique angle and changes the degree of hydration of the oceanic plate as it subducts within our area. Fluid flow out of oceanic crust is likely impeded by the low-porosity basal sediment package except along the focused thrust faults. Decollements are present at the top of oceanic basement, at the top of the high-wavespeed basal unit, and within sedimentary strata at higher levels; the decollement at the top of oceanic crust is active at the toe of the deformation front. The basal sedimentary unit appears to be mechanically strong, similar to observations from offshore Sumatra, where strongly consolidated sediments at the deformation front are interpreted to facilitate megathrust rupture to the trench (Hupers et al., 2017). A uniformly strong plate interface at Cascadia may inhibit microseismicity while building stress that is released in great earthquakes.

  17. Topographic control of oceanic flows in deep passages and straits

    Science.gov (United States)

    Whitehead, J. A.

    1998-08-01

    Saddle points between neighboring deep ocean basins are the sites of unidirectional flow from one basin to the next, depending on the source of bottom water. Flow in these sites appears to be topographically controlled so the interface between the bottom water and the water above adjusts itself to permit bottom water flow from the basin that contains a source of bottom water into the next. Examples in the Atlantic include flow in the Romanche Fracture Zone, the Vema Channel, the Ceara Abyssal Plain, the Anegada-Jungfern passage, and the Discovery Gap, but there are many more. Theoretical predictions of volume flux using a method that requires only conductivity-temperature-depth data archives and detailed knowledge of bathymetry near the saddle point are compared with volume flux estimates using current meters and/or geostrophic estimates for seven cases. The ratio of prediction to volume flux estimate ranges from 1.0 to 2.7. Some ocean straits that separate adjacent seas are also found to critically control bidirectional flows between basins. Theory of the influence of rotation on such critical flows is reviewed. Predictions of volume flux in eight cases are compared with ocean estimates of volume flux from traditional methods.

  18. Small fractures in deep sea sediments: indicators of pore fluid migration along compaction faults

    International Nuclear Information System (INIS)

    Buckley, D.E.

    1989-01-01

    A long piston core taken from the Southern Nares Abyssal Plain, intersected four fractures in plastic sediments between 17 and 25 m below the sea floor. Faults have been identified from seismic reflection surveys of sediments in this area. The sampled fractures all occurred in oxidized brown clays. Each fracture consisted of a simple plane having apparent dips ranging from 52-63 0 . One fracture had a well developed pale brown alteration halo extending out to 1.5 cm along this plane. Two fractures had no apparent alteration halo, but one fracture appeared to have fine-scale anastomosing features surrounding the main slip plane. Selective chemical tests for labile metal content in sediments surrounding the fractures revealed that about 70% of the reducible manganese, and 40% of the reducible iron had been leached from the sediments in the alteration halo surrounding the fracture plane. These results suggest that reducing pore fluids had migrated along the fracture plane to cause the observed effects. Implications of this study are that compaction faults may act as episodic conduits for vertical advection of pore water during dewatering of unconsolidated sediments. This may be a significant factor to be considered in assessing the effectiveness of deep sea sediment barriers for radioactive waste disposal. (author)

  19. Geochemical cycles and climate change studied chiefly in the ocean

    International Nuclear Information System (INIS)

    Tsunogai, Shizuo

    2011-01-01

    I have obtained following results written in my 209 scientific papers. 1. The tropospheric aerosols having the residence time of about 5 days are sporadically transported with a few % of long lived stratospheric aerosols. 2. The air-sea gas exchange at the sea surface is highly controlled by air bubbles taken into the depths sometimes more than 20m, inducing the fact that the gas exchange rate of CO 2 is a few tens % at least larger than that of O 2 . 3. The Pacific Deep Water can absorb the largest amount of CO 2 when its nutrients are used by photosynthesis, due to the facts that (1) it dissolved much CaCO 3 test during its stay in the deep, (2) it was formed before the industrial revolution, and (3) it expelled CO 2 from the surface during winter in the Antarctic Ocean. 4. The continental shelf zone shallower than 200m occupying only 8% of area of world seas is contributing about a half of the oceans' atmospheric CO 2 absorption. 5. Chemical tracers reveal one order of magnitude slower northward flow of the Pacific Deep Water than the current meter, its vertical eddy diffusivity of 1.2cm 2 /sec and its oldest age of 2000 years as well as 3% renewal of the Japan Sea deep water in winter 2000-2001. 6. Analyzing the oceanic behavior of radiochemical isotopes of insoluble metals, most of which cannot be collected on filter paper but settle down with great speeds, I submitted the train-passengers model for their removal from the ocean. 7. Sediment trap experiments gave the results that the organic C/carbonate C ratio is large in the western North Pacific, but it decreases with depth, indicating that the biological pump in the eastern Pacific and the Atlantic deeper than 1km is helpless. 8. In the Cenozoic era, diatoms are the strongest phytoplankton in the ocean, but their superiority disappears by reducing the concentration of dissolved silica below a threshold value due to their exclusive propagation during, for example, spring blooming, introducing the community

  20. Biodiversity of polycyclic aromatic hydrocarbon-degrading bacteria from deep sea sediments of the Middle Atlantic Ridge

    OpenAIRE

    Cui, Zhisong; Lai, Qiliang; Dong, Chunming; Shao, Zongze

    2008-01-01

    The bacteria involved in the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in deep sea subsurface environments are largely unknown. In order to reveal their biodiversity, sediments from 2.2 m under the bottom surface at a water depth of 3542 m were sampled on the Middle Atlantic Ridge with a gravity column sampler. The sediments were promptly enriched with either crude oil or a mixture of PAHs (naphthalene, phenanthrene and pyrene) as the sole carbon source, and further enriched w...

  1. Rapid global ocean-atmosphere response to Southern Ocean freshening during the last glacial.

    Science.gov (United States)

    Turney, Chris S M; Jones, Richard T; Phipps, Steven J; Thomas, Zoë; Hogg, Alan; Kershaw, A Peter; Fogwill, Christopher J; Palmer, Jonathan; Bronk Ramsey, Christopher; Adolphi, Florian; Muscheler, Raimund; Hughen, Konrad A; Staff, Richard A; Grosvenor, Mark; Golledge, Nicholas R; Rasmussen, Sune Olander; Hutchinson, David K; Haberle, Simon; Lorrey, Andrew; Boswijk, Gretel; Cooper, Alan

    2017-09-12

    Contrasting Greenland and Antarctic temperatures during the last glacial period (115,000 to 11,650 years ago) are thought to have been driven by imbalances in the rates of formation of North Atlantic and Antarctic Deep Water (the 'bipolar seesaw'). Here we exploit a bidecadally resolved 14 C data set obtained from New Zealand kauri (Agathis australis) to undertake high-precision alignment of key climate data sets spanning iceberg-rafted debris event Heinrich 3 and Greenland Interstadial (GI) 5.1 in the North Atlantic (~30,400 to 28,400 years ago). We observe no divergence between the kauri and Atlantic marine sediment 14 C data sets, implying limited changes in deep water formation. However, a Southern Ocean (Atlantic-sector) iceberg rafted debris event appears to have occurred synchronously with GI-5.1 warming and decreased precipitation over the western equatorial Pacific and Atlantic. An ensemble of transient meltwater simulations shows that Antarctic-sourced salinity anomalies can generate climate changes that are propagated globally via an atmospheric Rossby wave train.A challenge for testing mechanisms of past climate change is the precise correlation of palaeoclimate records. Here, through climate modelling and the alignment of terrestrial, ice and marine 14 C and 10 Be records, the authors show that Southern Ocean freshwater hosing can trigger global change.

  2. Deep sub-seafloor prokaryotes stimulated at interfaces over geological time RID B-1731-2010 RID A-1877-2008 RID D-2690-2009 RID A-2970-2010

    DEFF Research Database (Denmark)

    Parkes, RJ; Webster, G.; Cragg, BA

    2005-01-01

    in numbers of prokaryotes at depth were more restricted but also corresponded to increased activity; however, this time they were associated with repeating layers of diatom-rich sediments ( about 9 Myr old). These results show that deep sedimentary prokaryotes can have high activity, have changing diversity...... Pacific Ocean sites, margin and open ocean, both of which have deep, subsurface stimulation of prokaryotic processes associated with geochemical and/or sedimentary interfaces. At 90 m depth in the margin site, stimulation was such that prokaryote numbers were higher ( about 13-fold) and activity rates...

  3. Arctic deep-water ferromanganese-oxide deposits reflect the unique characteristics of the Arctic Ocean

    Science.gov (United States)

    Hein, James; Konstantinova, Natalia; Mikesell, Mariah; Mizell, Kira; Fitzsimmons, Jessica N.; Lam, Phoebe; Jensen, Laramie T.; Xiang, Yang; Gartman, Amy; Cherkashov, Georgy; Hutchinson, Deborah; Till, Claire P.

    2017-01-01

    Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by continental shelf and basins semi-closed to deep-water circulation. Here, we present data for ferromanganese crusts and nodules collected from the Amerasia Arctic Ocean in 2008, 2009, and 2012 (HLY0805, HLY0905, HLY1202). We determined mineral and chemical compositions of the crusts and nodules and the onset of their formation. Water column samples from the GEOTRACES program were analyzed for dissolved and particulate scandium concentrations, an element uniquely enriched in these deposits.The Arctic crusts and nodules are characterized by unique mineral and chemical compositions with atypically high growth rates, detrital contents, Fe/Mn ratios, and low Si/Al ratios, compared to deposits found elsewhere. High detritus reflects erosion of submarine outcrops and North America and Siberia cratons, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. Uniquely high Fe/Mn ratios are attributed to expansive continental shelves, where diagenetic cycling releases Fe to bottom waters, and density flows transport shelf bottom water to the open Arctic Ocean. Low Mn contents reflect the lack of a mid-water oxygen minimum zone that would act as a reservoir for dissolved Mn. The potential host phases and sources for elements with uniquely high contents are discussed with an emphasis on scandium. Scandium sorption onto Fe oxyhydroxides and Sc-rich detritus account for atypically high scandium contents. The opening of Fram Strait in the Miocene and ventilation of the deep basins initiated Fe-Mn crust growth ∼15 Myr ago.

  4. Geochemical prerequisites of petroleum-gas formation in the Mesozoic-Cenozoic sedimentary layer of the world's oceans

    Energy Technology Data Exchange (ETDEWEB)

    Trotsyuk, V Ya

    1979-05-01

    A summarization is given of the latest material on the geochemistry of trace organic matter of Mesozoic-Cenozoic deposits of the world's oceans, obtained as a result of deep-sea drilling. Trace organic matter was found to be present in the sedimentary layers of the ocean outskirts in amounts near that found in the continental stratosphere, but that content was five times less in the interior region of the oceans. The trace organic matter of deposits in the marginal region of the oceans was found to have a significant petroleum-gas matrix potential with respect to the level of content and composition characteristics. The distribution of organic carbon was found to be uneven in variously aged horizons of the Mesozoic-Cenozoic. The maximum content of organic carbon was noted in the Neogene-Quaternary and lower Cretaceous deposits. An elevated content of trace organic matter was found to be characteristic of the oceanic stratisphere in lithological mixed sediments: terrigenous-carbonate and terrigenous-silicons was 1.5 times greater than the trace organic matter in clays. Fundamental geochemical propagation laws were formulated, possibly for petroleum-gas-bearing sediment basins under the ocean bottom and beyond the shelf. 18 references, 3 figures.

  5. Ship Sensor Observations for Islands in the Stream 2002 - Deep Reef Habitat - Office of Ocean Exploration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Hourly measurements made by selected ship sensors on the R/V Seward Johnson during the 2002 "Islands in the Stream - Deep Reef Habitat" expedition sponsored by the...

  6. Particle mixing processes of Chernobyl fallout in deep Norwegian Sea sediments: Evidence for seasonal effects

    Science.gov (United States)

    Balzer, W.

    1996-09-01

    A 1430 m deep station in the Norwegian Sea (Voering Plateau) was occupied five times between May 1986 and February 1987 to investigate the seasonal variation in sediment mixing rates. Cherbnbyl-derived radiocesium, identified by its high proportion of short-lived 134Cs, was used as a tracer for mixing. Most of the nuclide input arrived at the sediment within a narrow time span in June/early July during the beginning of the seasonal biogenic sedimentation pulse. Measured 137Cs profiles in the sediment over time were compared with modelled distributions calculated with a finite difference scheme. The input function of radiocesium to the sea floor was evaluated from the increase of the total inventory with time. Time-invariant mixing coefficients did not provide reasonable fits to either summer or winter distributions. The best fit was obtained with a rate of mixing proportional to the radiocesium input flux, with an average enhancement factor of 6.6 during the two summer months. It appears that the benthic macrofauna are more active during the food supply season and rapidly ingest/bury freshly sedimented materials.

  7. Response to Comment on "Dilution limits dissolved organic carbon utilization in the deep ocean"

    KAUST Repository

    Arrieta, Jesus

    2015-12-18

    Our recent finding that dilution limits dissolved organic carbon (DOC) utilization in the deep ocean has been criticized based on the common misconception that lability equates to rapid and complete utilization. Even when considering the redefinition of recalcitrant DOC recently proposed by Jiao et al., the dilution hypothesis best explains our experimental observations.

  8. Short-term impact of deep sand extraction and ecosystem-based landscaping on macrozoobenthos and sediment characteristics.

    Science.gov (United States)

    de Jong, Maarten F; Baptist, Martin J; Lindeboom, Han J; Hoekstra, Piet

    2015-08-15

    We studied short-term changes in macrozoobenthos in a 20m deep borrow pit. A boxcorer was used to sample macrobenthic infauna and a bottom sledge was used to sample macrobenthic epifauna. Sediment characteristics were determined from the boxcore samples, bed shear stress and near-bed salinity were estimated with a hydrodynamic model. Two years after the cessation of sand extraction, macrozoobenthic biomass increased fivefold in the deepest areas. Species composition changed significantly and white furrow shell (Abra alba) became abundant. Several sediment characteristics also changed significantly in the deepest parts. Macrozoobenthic species composition and biomass significantly correlated with time after cessation of sand extraction, sediment and hydrographical characteristics. Ecosystem-based landscaped sand bars were found to be effective in influencing sediment characteristics and macrozoobenthic assemblage. Significant changes in epifauna occurred in deepest parts in 2012 which coincided with the highest sedimentation rate. We recommend continuing monitoring to investigate medium and long-term impacts. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

    NARCIS (Netherlands)

    Braeckman, U.; Van Colen, C.; Guilini, K.; Van Gansbeke, D.; Soetaert, K.; Vincx, M.; Vanaverbeke, J.

    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

  10. Neutralizing Carbonic Acid in Deep Carbonate Strata below the North Atlantic

    Energy Technology Data Exchange (ETDEWEB)

    Daniel P. Schrag

    2006-07-14

    Our research is aimed at investigating several technical issues associated with carbon dioxide sequestration in calcium carbonate sediments below the sea floor through laboratory experiments and chemical transport modeling. Our goal is to evaluate the basic feasibility of this approach, including an assessment of optimal depths, sediment types, and other issues related to site selection. The results of our modeling efforts were published this past summer in the Proceedings of the National Academy of Sciences. We are expanding on that work through a variety of laboratory and modeling efforts. In the laboratories at Columbia and at Harvard, we are studying the flow of liquid carbon dioxide and carbon dioxide-water mixtures through calcium carbonate sediments to better understand the geomechanical and structural stability of the sediments during and after injection. We are currently preparing the results of these findings for publication. In addition, we are investigating the kinetics of calcium carbonate dissolution in the presence of CO{sub 2}-water fluids, which is a critical feature of the system as it allows for increased permeability during injection. We are also investigating the possibility of carbon dioxide hydrate formation in the pore fluid, which might complicate the injection procedure by reducing sediment permeability but might also provide an upper seal in the sediment-pore fluid system, preventing release of CO{sub 2} into the deep ocean, particularly if depth and temperature at the injection point rule out immediate hydrate formation. This is done by injecting liquid CO{sub 2} into various types of porous media, and then monitoring the changes in permeability. Finally, we are performing an economic analysis to estimate costs of drilling and gas injection, site monitoring as well as the availability of potential disposal sites with particular emphasis on those sites that are within the 200-mile economic zone of the United States. We present some

  11. Near-bottom pelagic bacteria at a deep-water sewage sludge disposal site

    Energy Technology Data Exchange (ETDEWEB)

    Takizawa, M.; Straube, W.L.; Hill, R.T.; Colwell, R.R.

    1994-01-01

    The epibenthic bacterial community at deep-ocean sewage sludge disposal site DWD-106, located approximately 106 miles (ca. 196 km) off the coast of New Jersey, was assessed for changes associated with the introduction of large amounts of sewage sludge. Mixed cultures and bacterial isolates obtained from water overlying sediment core samples collected at the deep-water (2,500 m) municipal sewage disposal site were tested for the ability to grow under in situ conditions of temperature and pressure. The responses of cultures collected at a DWD-106 station heavily impacted by sewage sludge were compared with those of samples collected from a station at the same depth which was not contaminated by sewage sludge. Significant differences were observed in the ability of mixed bacterial cultures and isolates from the two sites to grow under deep-sea pressure and temperature conditions. The levels of sludge contamination were established by enumerating Clostridium perfringens, a sewage indicator bacterium, in sediment samples from the two sites. (Copyright (c) 1993, American Society for Microbiology.)

  12. Anthropogenic radionuclides in the Arctic Ocean. Distribution and pathways

    Energy Technology Data Exchange (ETDEWEB)

    Josefsson, Dan

    1998-05-01

    Anthropogenic radionuclide concentrations have been determined in seawater and sediment samples collected in 1991, 1994 and 1996 in the Eurasian Arctic shelf and interior. Global fallout, releases from European reprocessing plants and the Chernobyl accident are identified as the three main sources. From measurements in the Eurasian shelf seas it is concluded that the total input of {sup 134}Cs, {sup 137}Cs and {sup 90}Sr from these sources has been decreasing during the 1990`s, while {sup 129}I has increased. The main fraction of the reprocessing and Chernobyl activity found in Arctic Ocean surface layer is transported from the Barents Sea east along the Eurasian Arctic shelf seas to the Laptev Sea before entering the Nansen Basin. This inflow results in highest {sup 137}Cs, {sup 129}I and {sup 90}Sr concentrations in the Arctic Ocean surface layers, and continuously decreasing concentrations with depth. Chernobyl-derived {sup 137}Cs appeared in the central parts of the Arctic Ocean around 1991, and in the mid 1990`s the fraction to total {sup 137}Cs was approximately 30% in the entire Eurasian Arctic region. The transfer times for releases from Sellafield are estimated to be 5-7 years to the SE Barents Sea, 7-9 years to the Kara Sea, 10-11 years to the Laptev Sea and 12-14 years to the central Arctic Ocean. Global fallout is the primary source of plutonium with highest concentrations found in the Atlantic layer of the Arctic Ocean. When transported over the shallow shelf seas, particle reactive transuranic elements experience an intense scavenging. A rough estimate shows that approximately 75% of the plutonium entering the Kara and Laptev Seas are removed to the sediment. High seasonal riverine input of {sup 239}, {sup 240}Pu is observed near the mouths of the large Russian rivers. Sediment inventories show much higher concentrations on the shelf compared to the deep Arctic Ocean. This is primarily due to the low particle flux in the open ocean

  13. Anthropogenic radionuclides in the Arctic Ocean. Distribution and pathways

    International Nuclear Information System (INIS)

    Josefsson, Dan

    1998-05-01

    Anthropogenic radionuclide concentrations have been determined in seawater and sediment samples collected in 1991, 1994 and 1996 in the Eurasian Arctic shelf and interior. Global fallout, releases from European reprocessing plants and the Chernobyl accident are identified as the three main sources. From measurements in the Eurasian shelf seas it is concluded that the total input of 134 Cs, 137 Cs and 90 Sr from these sources has been decreasing during the 1990's, while 129 I has increased. The main fraction of the reprocessing and Chernobyl activity found in Arctic Ocean surface layer is transported from the Barents Sea east along the Eurasian Arctic shelf seas to the Laptev Sea before entering the Nansen Basin. This inflow results in highest 137 Cs, 129 I and 90 Sr concentrations in the Arctic Ocean surface layers, and continuously decreasing concentrations with depth. Chernobyl-derived 137 Cs appeared in the central parts of the Arctic Ocean around 1991, and in the mid 1990's the fraction to total 137 Cs was approximately 30% in the entire Eurasian Arctic region. The transfer times for releases from Sellafield are estimated to be 5-7 years to the SE Barents Sea, 7-9 years to the Kara Sea, 10-11 years to the Laptev Sea and 12-14 years to the central Arctic Ocean. Global fallout is the primary source of plutonium with highest concentrations found in the Atlantic layer of the Arctic Ocean. When transported over the shallow shelf seas, particle reactive transuranic elements experience an intense scavenging. A rough estimate shows that approximately 75% of the plutonium entering the Kara and Laptev Seas are removed to the sediment. High seasonal riverine input of 239 , 240 Pu is observed near the mouths of the large Russian rivers. Sediment inventories show much higher concentrations on the shelf compared to the deep Arctic Ocean. This is primarily due to the low particle flux in the open ocean

  14. Dispersal of volcaniclastic material by buoyant water plumes in deep-ocean explosive basaltic eruptions

    Science.gov (United States)

    Barreyre, T.; Soule, S.; Reves-Sohn, R. A.

    2009-12-01

    The ability of mid-ocean ridge (MOR) volcanic systems to generate explosive eruptions is inhibited by the large hydrostatic pressures associated with their deep-sea location, which suppress volatile exsolution from the magma, and which preclude the generation of steam from lava-water interaction. Nevertheless, volcaniclastic material indicative of explosive activity has been found along many parts of the global MOR, raising important questions regarding the volatile systematics within mid-ocean ridge magmatic systems, and the processes by which volcaniclastic material may be dispersed during deep-sea eruptions. In this study we measured the settling velocities of volcaniclastic grains recovered from the Gakkel Ridge, Loihi Seamount, and Axial Volcano, and developed empirical settling velocity models as a function of particle size for three different particle shapes (angular, sheet, and rod). We then used the Morton, Turner, Taylor turbulent plume model to investigate how a plume of buoyant water may distribute this volcaniclastic material during a deep-sea eruption so that the physical characteristics of the deposits may be used to constrain the location and size (i.e., energy) of the eruptions that produced them. We ran the turbulent plume model for conditions ranging from a typical black smoker (~150 MW) to a megaplume (~30000 MW), and for water column density stratifications and currents corresponding to nominal conditions for the Arctic and Pacific Oceans. We found that maximum dispersal distances for the dominant size of volcaniclastic material within buoyant water plumes range from Pele). These distances are insufficient to explain the areal extent of the volcaniclastic deposits observed along the 85°E segment of the Gakkel Ridge and various portions of the Juan de Fuca Ridge, indicating that additional energy in the form of momentum from expanding gases is required to produce the observed deposits.

  15. The Vertical Profile of Ocean Mixing

    Science.gov (United States)

    Ferrari, R. M.; Nikurashin, M.; McDougall, T. J.; Mashayek, A.

    2014-12-01

    The upwelling of bottom waters through density surfaces in the deep ocean is not possible unless the sloping nature of the sea floor is taken into account. The bottom--intensified mixing arising from interaction of internal tides and geostrophic motions with bottom topography implies that mixing is a decreasing function of height in the deep ocean. This would further imply that the diapycnal motion in the deep ocean is downward, not upwards as is required by continuity. This conundrum regarding ocean mixing and upwelling in the deep ocean will be resolved by appealing to the fact that the ocean does not have vertical side walls. Implications of the conundrum for the representation of ocean mixing in climate models will be discussed.

  16. Fungal diversity in deep-sea sediments associated with asphalt seeps at the Sao Paulo Plateau

    Science.gov (United States)

    Nagano, Yuriko; Miura, Toshiko; Nishi, Shinro; Lima, Andre O.; Nakayama, Cristina; Pellizari, Vivian H.; Fujikura, Katsunori

    2017-12-01

    We investigated the fungal diversity in a total of 20 deep-sea sediment samples (of which 14 samples were associated with natural asphalt seeps and 6 samples were not associated) collected from two different sites at the Sao Paulo Plateau off Brazil by Ion Torrent PGM targeting ITS region of ribosomal RNA. Our results suggest that diverse fungi (113 operational taxonomic units (OTUs) based on clustering at 97% sequence similarity assigned into 9 classes and 31 genus) are present in deep-sea sediment samples collected at the Sao Paulo Plateau, dominated by Ascomycota (74.3%), followed by Basidiomycota (11.5%), unidentified fungi (7.1%), and sequences with no affiliation to any organisms in the public database (7.1%). However, it was revealed that only three species, namely Penicillium sp., Cadophora malorum and Rhodosporidium diobovatum, were dominant, with the majority of OTUs remaining a minor community. Unexpectedly, there was no significant difference in major fungal community structure between the asphalt seep and non-asphalt seep sites, despite the presence of mass hydrocarbon deposits and the high amount of macro organisms surrounding the asphalt seeps. However, there were some differences in the minor fungal communities, with possible asphalt degrading fungi present specifically in the asphalt seep sites. In contrast, some differences were found between the two different sampling sites. Classification of OTUs revealed that only 47 (41.6%) fungal OTUs exhibited >97% sequence similarity, in comparison with pre-existing ITS sequences in public databases, indicating that a majority of deep-sea inhabiting fungal taxa still remain undescribed. Although our knowledge on fungi and their role in deep-sea environments is still limited and scarce, this study increases our understanding of fungal diversity and community structure in deep-sea environments.

  17. Costa Rica Rift Revisited: Constraints on Shallow and Deep Hydrothermal Circulation in Oceanic Crust

    Science.gov (United States)

    Davis, E. E.; Becker, K.; He, J.

    2002-12-01

    New heat-flow observations made along two seismic reflection profiles on 6 Ma crust of the Costa Rica Rift flank show an inverse correlation between heat flow and sediment thickness similar to that observed on other sedimented ridges and young ridge flanks. Extrapolation of the seafloor heat-flow values to the top of the igneous crust - justified by comparing seafloor and borehole determinations where observations are colocated - show the surface of the igneous crust to be of uniform temperature despite large local sediment thickness variations. This is consistent with observations made at DSDP/ODP Holes 504B and 896A where basement temperatures are observed to be nearly identical, also despite contrasting sediment thicknesses. Efficient lateral heat exchange via vigorous crustal hydrothermal circulation is required to create the degree of uniformity inferred and observed. Permeability measurements at the two drill sites show that this vigorous circulation may be restricted to as little as the uppermost tens of m of the crust. Permeability determined deeper in Hole 504B is too low to permit thermally significant flow, although temperature logs suggest that thermally significant flow extends throughout the 2 km section penetrated at Site 504, presumably via pathways not intersected by the borehole. The laterally uniform temperatures in the uppermost igneous crust here and elsewhere are remarkable given the small apparent depth-extent of the circulation that so efficiently distributes heat. While certainly not as vigorous, the circulation at depth suggested by the temperature logs at Site 504 is also noteworthy; unfortunately the observation cannot be generalized because of the lack of other deep crustal holes that could permit direct observations, and the lack of a method for inferring deep hydrothermal structure.

  18. Biscogniauxone, a New Isopyrrolonaphthoquinone Compound from the Fungus Biscogniauxia mediterranea Isolated from Deep-Sea Sediments

    Directory of Open Access Journals (Sweden)

    Bin Wu

    2016-11-01

    Full Text Available The properties and the production of new metabolites from the fungal strain LF657 isolated from the Herodotes Deep (2800 m depth in the Mediterranean Sea are reported in this study. The new isolate was identified as Biscogniauxia mediterranea based on ITS1-5.8S-ITS2 and 28S rRNA gene sequences. A new isopyrrolonaphthoquinone with inhibitory activity against glycogen synthase kinase (GSK-3β was isolated from this fungus. This is the first report of this class of compounds from a fungus isolated from a deep-sea sediment, as well as from a Biscogniauxia species.

  19. Distribution of some chemical elements between dissolved and particulate phases in the ocean. Period covered: August 1, 1976--October 31, 1977

    International Nuclear Information System (INIS)

    Spencer, D.W.; Brewer, P.G.; Bacon, M.P.; Sachs, P.L.; Smith, C.L.; Fleer, A.; Kadar, S.

    1977-01-01

    Progress is reported on studies of the distribution of dissolved and particulate forms of naturally radioactive 210 Pb and 210 Po in ocean coastal waters, deep waters, and the continental shelf and slope. Data are included from measurements of 210 Pb and 210 Po in seawater and sediment samples collected in the Labrador Sea area, the North Sea, the Norwegian Sea, and the Iceland-Scotish Overflow area of the North Atlantic Ocean

  20. Parameterization of Mixed Layer and Deep-Ocean Mesoscales Including Nonlinearity

    Science.gov (United States)

    Canuto, V. M.; Cheng, Y.; Dubovikov, M. S.; Howard, A. M.; Leboissetier, A.

    2018-01-01

    In 2011, Chelton et al. carried out a comprehensive census of mesoscales using altimetry data and reached the following conclusions: "essentially all of the observed mesoscale features are nonlinear" and "mesoscales do not move with the mean velocity but with their own drift velocity," which is "the most germane of all the nonlinear metrics."� Accounting for these results in a mesoscale parameterization presents conceptual and practical challenges since linear analysis is no longer usable and one needs a model of nonlinearity. A mesoscale parameterization is presented that has the following features: 1) it is based on the solutions of the nonlinear mesoscale dynamical equations, 2) it describes arbitrary tracers, 3) it includes adiabatic (A) and diabatic (D) regimes, 4) the eddy-induced velocity is the sum of a Gent and McWilliams (GM) term plus a new term representing the difference between drift and mean velocities, 5) the new term lowers the transfer of mean potential energy to mesoscales, 6) the isopycnal slopes are not as flat as in the GM case, 7) deep-ocean stratification is enhanced compared to previous parameterizations where being more weakly stratified allowed a large heat uptake that is not observed, 8) the strength of the Deacon cell is reduced. The numerical results are from a stand-alone ocean code with Coordinated Ocean-Ice Reference Experiment I (CORE-I) normal-year forcing.

  1. Early diagenesis in the sediments of the Congo deep-sea fan dominated by massive terrigenous deposits: Part II - Iron-sulfur coupling

    Science.gov (United States)

    Taillefert, Martial; Beckler, Jordon S.; Cathalot, Cécile; Michalopoulos, Panagiotis; Corvaisier, Rudolph; Kiriazis, Nicole; Caprais, Jean-Claude; Pastor, Lucie; Rabouille, Christophe

    2017-08-01

    Deep-sea fans are well known depot centers for organic carbon that should promote sulfate reduction. At the same time, the high rates of deposition of unconsolidated metal oxides from terrigenous origin may also promote metal-reducing microbial activity. To investigate the eventual coupling between the iron and sulfur cycles in these environments, shallow sediment cores (Congo River deep-sea fan ( 5000 m) were profiled using a combination of geochemical methods. Interestingly, metal reduction dominated suboxic carbon remineralization processes in most of these sediments, while dissolved sulfide was absent. In some 'hotspot' patches, however, sulfate reduction produced large sulfide concentrations which supported chemosynthetic-based benthic megafauna. These environments were characterized by sharp geochemical boundaries compared to the iron-rich background environment, suggesting that FeS precipitation efficiently titrated iron and sulfide from the pore waters. A companion study demonstrated that methanogenesis was active in the deep sediment layers of these patchy ecosystems, suggesting that sulfate reduction was promoted by alternative anaerobic processes. These highly reduced habitats could be fueled by discrete, excess inputs of highly labile natural organic matter from Congo River turbidites or by exhumation of buried sulfide during channel flank erosion and slumping. Sulfidic conditions may be maintained by the mineralization of decomposition products from local benthic macrofauna or bacterial symbionts or by the production of more crystalline Fe(III) oxide phases that are less thermodynamically favorable than sulfate reduction in these bioturbated sediments. Overall, the iron and sulfur biogeochemical cycling in this environment is unique and much more similar to a coastal ecosystem than a deep-sea environment.

  2. Were Ocean Impacts an Important Mechanism to Deliver Meteoritic Organic Matter to the Early Earth? Some Inferences from Eltanin

    Science.gov (United States)

    Kyte, Frank T.; Gersonde, Rainer; Kuhn. Gerhard

    2002-01-01

    Several workers have addressed the potential for extraterrestrial delivery of volatles, including water and complex organic compounds, to the early Earth. For example, Chyba and Sagan (1992) argued that since impacts would destroy organic matter, most extraterrestrial organics must be delivered in the fine-fractions of interplanetary dust. More recent computer simulations (Pierazzo and Chyba, 1999), however, have shown that substantial amounts of amino acids may survive the impacts of large (km-sized) comets and that this may exceed the amounts derived from IDPs or Miller-Urey synthesis in the atmosphere. Once an ocean developed on the early Earth, impacts of small ,asteroids and comets into deep-ocean basins were potentially common and may have been the most likely events to deliver large amounts of organics. The deposits of the late Pliocene impact of the Eltanin asteroid into the Bellingshausen Sea provide the only record of a deep-ocean (approx. 5 km) impact that can be used to constrain models of these events. This impact was first discovered in 1981 as an Ir anomaly in sediment cores collected by the USNS Eltanin in 1965 (Kyte et al., 1981). In 1995, Polarstem expedition ANT XII/4 made the first geological survey of the suspected impact region. Three sediment cores sampled around the San Martin seamounts (approx. 57.5S, 91 W) contained well-preserved impact deposits that include disturbed ocean sediments and meteoritic impact ejecta (Gersonde et al., 1997). The latter is composed of shock- melted asteroidal materials and unmelted meteorites. In 2001, the FS Polarstem returned to the impact area during expedition ANT XVIII/5a. At least 16 cores were recovered that contain ejecta deposits. These cores and geophysical data from the expedition can be used to map the effects of the impact over a large region of the ocean floor.

  3. Mine Waste and Acute Warming Induce Energetic Stress in the Deep-Sea Sponge Geodia atlantica and Coral Primnoa resedeaformis; Results From a Mesocosm Study

    Directory of Open Access Journals (Sweden)

    Elliot Scanes

    2018-04-01

    Full Text Available There is the potential for climate change to interact with pollution in all of the Earth's oceans. In the fjords of Norway, mine tailings are released into fjords generating suspended sediment plumes that impact deep-sea ecosystems. These same deep-sea ecosystems are expected to undergo periodic warming as climate change increases the frequency of down-welling events in fjords. It remains unknown how a polluted deep-sea ecosystem would respond to down-welling because multiple stressors will often interact in unpredictable ways. Here, we exposed two deep-sea foundation species; the gorgonian coral Primnoa resedaeformis and the demosponge Geodia atlantica to suspended sediment (10 mg L−1 and acute warming (+5°C in a factorial mesocosm experiment for 40 days. Physiology (respiration, nutrient flux and cellular responses (lysosomal cell stability were measured for both the coral and sponge. Exposure to elevated suspended sediment reduced metabolism, supressed silicate uptake and induced cellular instability of the sponge G. atlantica. However, combining sediment with warming caused G. atlantica to respire and excrete nitrogen at a greater rate. For the coral P. resedaeformis, suspended sediments reduced O:N ratios after 40 days, however, warming had a greater effect on P. resedaeformis physiology compared to sediment. Warming increased respiration, nitrogen excretion, and cellular instability which resulted in lower O:N ratios. We argue that suspended sediment and warming can act alone and also interact to cause significant harm to deep-sea biota, however responses are likely to be species-specific. Warming and pollution could interact in the deep-sea to cause mortality to the coral P. resedaeformis and to a lesser extent, the sponge G. atlantica. As foundation species, reducing the abundance of deep sea corals and sponges would likely impact the ecosystems they support.

  4. Lead isotopes in deep-sea coral skeletons: Ground-truthing and a first deglacial Southern Ocean record

    Science.gov (United States)

    Wilson, David J.; van de Flierdt, Tina; Adkins, Jess F.

    2017-05-01

    Past changes in seawater lead (Pb) isotopes record the temporal evolution of anthropogenic pollution, continental weathering inputs, and ocean current transport. To advance our ability to reconstruct this signature, we present methodological developments that allow us to make precise and accurate Pb isotope measurements on deep-sea coral aragonite, and apply our approach to generate the first Pb isotope record for the glacial to deglacial mid-depth Southern Ocean. Our refined methodology includes a two-step anion exchange chemistry procedure and measurement using a 207Pb-204Pb double spike on a Thermo Finnigan Triton TIMS instrument. By employing a 1012 Ω resistor (in place of a 1011 Ω resistor) to measure the low-abundance 204Pb ion beam, we improve the internal precision on 206,207,208Pb/204Pb for a 2 ng load of NIST-SRM-981 Pb from typically ∼420 ppm to ∼230 ppm (2 s.e.), and the long term external reproducibility from ∼950 ppm to ∼550 ppm (2 s.d.). Furthermore, for a typical 500 mg coral sample with low Pb concentrations (∼6-10 ppb yielding ∼3-5 ng Pb for analysis), we obtain a comparable internal precision of ∼150-250 ppm for 206,207,208Pb/204Pb, indicating a good sensitivity for tracing natural Pb sources to the oceans. Successful extraction of a seawater signal from deep-sea coral aragonite further relies on careful physical and chemical cleaning steps, which are necessary to remove anthropogenic Pb contaminants and obtain results that are consistent with ferromanganese crusts. Applying our approach to a collection of late glacial and deglacial corals (∼12-40 ka BP) from south of Tasmania at ∼1.4-1.7 km water depth, we generated the first intermediate water Pb isotope record from the Southern Ocean. That record reveals millennial timescale variability, controlled by binary mixing between two Pb sources, but no distinct glacial-interglacial Pb isotope shift. Mixing between natural endmembers is fully consistent with our data and points to

  5. Reviews and syntheses: Hidden forests, the role of vegetated coastal habitats in the ocean carbon budget

    Science.gov (United States)

    Duarte, Carlos M.

    2017-01-01

    Vegetated coastal habitats, including seagrass and macroalgal beds, mangrove forests and salt marshes, form highly productive ecosystems, but their contribution to the global carbon budget remains overlooked, and these forests remain hidden in representations of the global carbon budget. Despite being confined to a narrow belt around the shoreline of the world's oceans, where they cover less than 7 million km2, vegetated coastal habitats support about 1 to 10 % of the global marine net primary production and generate a large organic carbon surplus of about 40 % of their net primary production (NPP), which is either buried in sediments within these habitats or exported away. Large, 10-fold uncertainties in the area covered by vegetated coastal habitats, along with variability about carbon flux estimates, result in a 10-fold bracket around the estimates of their contribution to organic carbon sequestration in sediments and the deep sea from 73 to 866 Tg C yr-1, representing between 3 % and 1/3 of oceanic CO2 uptake. Up to 1/2 of this carbon sequestration occurs in sink reservoirs (sediments or the deep sea) beyond these habitats. The organic carbon exported that does not reach depositional sites subsidizes the metabolism of heterotrophic organisms. In addition to a significant contribution to organic carbon production and sequestration, vegetated coastal habitats contribute as much to carbonate accumulation as coral reefs do. While globally relevant, the magnitude of global carbon fluxes supported by salt-marsh, mangrove, seagrass and macroalgal habitats is declining due to rapid habitat loss, contributing to loss of CO2 sequestration, storage capacity and carbon subsidies. Incorporating the carbon fluxes' vegetated coastal habitats' support into depictions of the carbon budget of the global ocean and its perturbations will improve current representations of the carbon budget of the global ocean.

  6. Potential Increasing Dominance of Heterotrophy in the Global Ocean

    Science.gov (United States)

    Kvale, K.; Meissner, K. J.; Keller, D. P.

    2016-02-01

    Autotrophs are largely limited by resources in the modern ocean. However, standard metabolic theory suggests continued ocean warming could globally benefit heterotrophs, thereby reducing autotrophic nutrient limitation. The paleo record as well as modern observations offer evidence this has happened in the past and could happen again. Increasing dominance of heterotrophs would result in strong nutrient recycling in the upper ocean and high rates of net primary production (NPP), yet low carbon export to the deep ocean and sediments. We describe the transition towards such a state in the early 22nd century as a response to business-as-usual Representative Concentration Pathway forcing (RCP8.5) in an intermediate complexity Earth system model in three configurations: with and without an explicit calcifier phytoplankton class and calcite ballast model. In all models nutrient regeneration in the near surface becomes an increasingly important driver of primary production. The near-linear relationship between changes in NPP and global sea surface temperature (SST) found over the 21st century becomes exponential above a 2-4 °C global mean SST change. This transition to a more heterotrophic ocean agrees roughly with metabolic theory. Inclusion of small phytoplankton and calcifiers increase the model NPP:SST sensitivity because of their relatively higher nutrient affinity than general phytoplankton. Accounting for organic carbon "protected" from remineralization by carbonate ballast mitigates the exponential increase in NPP and provides an increasingly important pathway for deep carbon export with higher SST changes, despite simultaneous increasing carbonate dissolution rates due to ocean acidification.

  7. Short-term impact of deep sand extraction and ecosystem-based landscaping on macrozoobenthos and sediment characteristics

    NARCIS (Netherlands)

    de Jong, Maarten F.; Baptist, Martin J.; Lindeboom, Han J.; Hoekstra, Piet

    2015-01-01

    We studied short-term changes in macrozoobenthos in a 20. m deep borrow pit. A boxcorer was used to sample macrobenthic infauna and a bottom sledge was used to sample macrobenthic epifauna. Sediment characteristics were determined from the boxcore samples, bed shear stress and near-bed salinity were

  8. Microbial Life of North Pacific Oceanic Crust

    Science.gov (United States)

    Schumann, G.; Koos, R.; Manz, W.; Reitner, J.

    2003-12-01

    Information on the microbiology of the deep subsurface is necessary in order to understand the factors controlling the rate and extent of the microbially catalyzed reactions that influence the geophysical properties of these environments. Drilling into 45-Ma oceanic basaltic crust in a deepwater environment during ODP Leg 200 provided a promising opportunity to explore the abundance, diversity and activity of micro-organisms. The combined use of culture-independent molecular phylogenetic analyses and enrichment culture techniques is an advantageous approach in investigating subsurface microbial ecosystems. Enrichment culture methods allow the evaluation of potential activities and functions. Microbiological investigations revealed few aerobic cultivable, in part hitherto unknown, micro-organisms in deep submarine sediments and basaltic lava flows. 16S rDNA sequencing of isolates from sediment revealed the next relatives to be members of the genera Halomonas, Pseudomonas, and Lactobacillus. Within the Pseudomonadaceae the closest relative is Acinetobacter sp., which was isolated from a deep subsurface environment. The next phylogenetical relatives within the Halomonadaceae are bacteria typically isolated from Soda lakes, which are considered as model of early life conditions. Interestingly, not only sediment bacteria could be obtained in pure culture. Aerobic strains could also be successfully isolated from the massive tholeiitic basalt layer at a depth of 76.16 mbsf (46 m below the sediment/basement contact). These particular isolates are gram-positive with low G+C content of DNA, phylogenetically affiliated to the phylum Firmicutes. The closest neighbors are e.g. a marine Bacillus isolated from the Gulf of Mexico and a low G+C gram-positive bacterium, which belongs to the microbial flora in the deepest sea mud of the Mariana Trench, isolated from a depth of 10,897 m. Based on the similarity values, the isolates represent hitherto undescribed species of the deep

  9. Geomechanical, Hydraulic and Thermal Characteristics of Deep Oceanic Sandy Sediments Recovered during the Second Ulleung Basin Gas Hydrate Expedition

    Directory of Open Access Journals (Sweden)

    Yohan Cha

    2016-09-01

    Full Text Available This study investigates the geomechanical, hydraulic and thermal characteristics of natural sandy sediments collected during the Ulleung Basin gas hydrate expedition 2, East Sea, offshore Korea. The studied sediment formation is considered as a potential target reservoir for natural gas production. The sediments contained silt, clay and sand fractions of 21%, 1.3% and 77.7%, respectively, as well as diatomaceous minerals with internal pores. The peak friction angle and critical state (or residual state friction angle under drained conditions were ~26° and ~22°, respectively. There was minimal or no apparent cohesion intercept. Stress- and strain-dependent elastic moduli, such as tangential modulus and secant modulus, were identified. The sediment stiffness increased with increasing confining stress, but degraded with increasing strain regime. Variations in water permeability with water saturation were obtained by fitting experimental matric suction-water saturation data to the Maulem-van Genuchen model. A significant reduction in thermal conductivity (from ~1.4–1.6 to ~0.5–0.7 W·m−1·K−1 was observed when water saturation decreased from 100% to ~10%–20%. In addition, the electrical resistance increased quasi-linearly with decreasing water saturation. The geomechanical, hydraulic and thermal properties of the hydrate-free sediments reported herein can be used as the baseline when predicting properties and behavior of the sediments containing hydrates, and when the hydrates dissociate during gas production. The variations in thermal and hydraulic properties with changing water and gas saturation can be used to assess gas production rates from hydrate-bearing deposits. In addition, while depressurization of hydrate-bearing sediments inevitably causes deformation of sediments under drained conditions, the obtained strength and stiffness properties and stress-strain responses of the sedimentary formation under drained loading conditions

  10. 231Pa and 230Th in the ocean model of the Community Earth System Model (CESM1.3)

    Science.gov (United States)

    Gu, Sifan; Liu, Zhengyu

    2017-12-01

    The sediment 231Pa / 230Th activity ratio is emerging as an important proxy for deep ocean circulation in the past. In order to allow for a direct model-data comparison and to improve our understanding of the sediment 231Pa / 230Th activity ratio, we implement 231Pa and 230Th in the ocean component of the Community Earth System Model (CESM). In addition to the fully coupled implementation of the scavenging behavior of 231Pa and 230Th with the active marine ecosystem module (particle-coupled: hereafter p-coupled), another form of 231Pa and 230Th have also been implemented with prescribed particle flux fields of the present climate (particle-fixed: hereafter p-fixed). The comparison of the two forms of 231Pa and 230Th helps to isolate the influence of the particle fluxes from that of ocean circulation. Under present-day climate forcing, our model is able to simulate water column 231Pa and 230Th activity and the sediment 231Pa / 230Th activity ratio in good agreement with available observations. In addition, in response to freshwater forcing, the p-coupled and p-fixed sediment 231Pa / 230Th activity ratios behave similarly over large areas of low productivity on long timescales, but can differ substantially in some regions of high productivity and on short timescales, indicating the importance of biological productivity in addition to ocean transport. Therefore, our model provides a potentially powerful tool to help the interpretation of sediment 231Pa / 230Th reconstructions and to improve our understanding of past ocean circulation and climate changes.

  11. Mission Moho: Rationale for drilling deep through the ocean crust into the upper mantle

    Science.gov (United States)

    Ildefonse, B.; Abe, N.; Kelemen, P. B.; Kumagai, H.; Teagle, D. A. H.; Wilson, D. S.; Moho Proponents, Mission

    2009-04-01

    Sampling a complete section of the ocean crust to the Moho was the original inspiration for scientific ocean drilling, and remains the main goal of the 21st Century Mohole Initiative in the IODP Science Plan. Fundamental questions about the composition, structure, and geophysical characteristics of the ocean lithosphere, and about the magnitude of chemical exchanges between the mantle, crust and oceans remain unresolved due to the absence of in-situ samples and measurements. The geological nature of the Mohorovičić discontinuity itself remains poorly constrained. "Mission Moho" is a proposal that was submitted to IODP in April 2007, with the ambition to drill completely through intact oceanic crust formed at a fast spreading rate, across the Moho and into the uppermost mantle. Although, eventually, no long-term mission was approved by IODP, the scientific objectives related to deep drilling in the ocean crust remain essential to our understanding of the Earth. These objectives are to : - Determine the geological meaning of the Moho in different oceanic settings, determine the in situ composition, structure and physical properties of the uppermost mantle, and understand mantle melt migration, - Determine the bulk composition of the oceanic crust to establish the chemical links between erupted lavas and primary mantle melts, understand the extent and intensity of seawater hydrothermal exchange with the lithosphere, and estimate the chemical fluxes returned to the mantle by subduction, - Test competing hypotheses of the ocean crust accretion at fast spreading mid-ocean ridges, and quantify the linkages and feedbacks between magma intrusion, hydrothermal circulation and tectonic activity, - Calibrate regional seismic measurements against recovered cores and borehole measurements, and understand the origin of marine magnetic anomalies, - Establish the limits of life in the ocean lithosphere. The "MoHole" was planned as the final stage of Mission Moho, which requires

  12. Environment-Dependent Distribution of the Sediment nifH-Harboring Microbiota in the Northern South China Sea

    Science.gov (United States)

    Yang, Jinying; Li, Jing; Luan, Xiwu; Zhang, Yunbo; Gu, Guizhou; Xue, Rongrong; Zong, Mingyue; Klotz, Martin G.

    2013-01-01

    The South China Sea (SCS), the largest marginal sea in the Western Pacific Ocean, is a huge oligotrophic water body with very limited influx of nitrogenous nutrients. This suggests that sediment microbial N2 fixation plays an important role in the production of bioavailable nitrogen. To test the molecular underpinning of this hypothesis, the diversity, abundance, biogeographical distribution, and community structure of the sediment diazotrophic microbiota were investigated at 12 sampling sites, including estuarine, coastal, offshore, deep-sea, and methane hydrate reservoirs or their prospective areas by targeting nifH and some other functional biomarker genes. Diverse and novel nifH sequences were obtained, significantly extending the evolutionary complexity of extant nifH genes. Statistical analyses indicate that sediment in situ temperature is the most significant environmental factor influencing the abundance, community structure, and spatial distribution of the sediment nifH-harboring microbial assemblages in the northern SCS (nSCS). The significantly positive correlation of the sediment pore water NH4+ concentration with the nifH gene abundance suggests that the nSCS sediment nifH-harboring microbiota is active in N2 fixation and NH4+ production. Several other environmental factors, including sediment pore water PO43− concentration, sediment organic carbon, nitrogen and phosphorus levels, etc., are also important in influencing the community structure, spatial distribution, or abundance of the nifH-harboring microbial assemblages. We also confirmed that the nifH genes encoded by archaeal diazotrophs in the ANME-2c subgroup occur exclusively in the deep-sea methane seep areas, providing for the possibility to develop ANME-2c nifH genes as a diagnostic tool for deep-sea methane hydrate reservoir discovery. PMID:23064334

  13. Submersible Data (Dive Waypoints) for Islands in the Stream 2002 - Deep Reef Habitat - Office of Ocean Exploration

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Data and information collected by the submersible Johnson Sea-Link II at waypoints along its track during one dive of the 2002 "Islands in the Stream - Deep Reef...

  14. Ocean One: A Robotic Avatar for Oceanic Discovery

    KAUST Repository

    Khatib, Oussama; Yeh, Xiyang; Brantner, Gerald; Soe, Brian; Kim, Boyeon; Ganguly, Shameek; Stuart, Hannah; Wang, Shiquan; Cutkosky, Mark; Edsinger, Aaron; Mullins, Phillip; Barham, Mitchell; Voolstra, Christian R.; Salama, Khaled N.; L'Hour, Michel; Creuze, Vincent

    2016-01-01

    The promise of oceanic discovery has long intrigued scientists and explorers, whether with the idea of studying underwater ecology and climate change or with the hope of uncovering natural resources and historic secrets buried deep in archaeological sites. This quest to explore the oceans requires skilled human access, yet much of the oceans are inaccessible to human divers; nearly ninetenths of the ocean floor is at 1 km or deeper [1]. Accessing these depths is imperative since factors such as pollution and deep-sea trawling threaten ecology and archaeological sites. While remotely operated vehicles (ROVs) are inadequate for the task, a robotic avatar could go where humans cannot and still embody human intelligence and intentions through immersive interfaces.

  15. Ocean One: A Robotic Avatar for Oceanic Discovery

    KAUST Repository

    Khatib, Oussama

    2016-11-11

    The promise of oceanic discovery has long intrigued scientists and explorers, whether with the idea of studying underwater ecology and climate change or with the hope of uncovering natural resources and historic secrets buried deep in archaeological sites. This quest to explore the oceans requires skilled human access, yet much of the oceans are inaccessible to human divers; nearly ninetenths of the ocean floor is at 1 km or deeper [1]. Accessing these depths is imperative since factors such as pollution and deep-sea trawling threaten ecology and archaeological sites. While remotely operated vehicles (ROVs) are inadequate for the task, a robotic avatar could go where humans cannot and still embody human intelligence and intentions through immersive interfaces.

  16. Analysis of a deep nucleus of Tehuantepec Gulf

    International Nuclear Information System (INIS)

    Ordonez R, E.; Lopez M, J.; Ramirez T, J. J.; Machain C, M. L.

    2009-10-01

    A nucleus of sediments obtained in the deep of Tehuantepec Gulf is analyzed; this nucleus has the particularity of to be a sampling of longitude of 18.3 m that include the total of last period glacial, few times obtained in our country. The physical chemistry composition of 10 selected fractions are analyzed with the purpose of to understand the formation processes of deep ocean along the period of 120 000 years, that includes the extracted fraction. Crystallography analysis, morphology, physical chemistry characterization and activity gamma were made. Finding that the content of organic matter falls as the superficial area increases, also was found the presence of natural uranium in similar concentration and balance with its radiogenic descendants along the nucleus profile what suggests the uranium migration to interior of mineral grains. (Author)

  17. MBARI Mapping AUV: A High-Resolution Deep Ocean Seafloor Mapping Capability

    Science.gov (United States)

    Caress, D. W.; Kirkwood, W. J.; Thomas, H.; McEwen, R.; Henthorn, R.; McGill, P.; Thompson, D.; Sibenac, M.; Jensen, S.; Shane, F.; Hamilton, A.

    2005-05-01

    The Monterey Bay Aquarium Research Institute (MBARI) is developing an autonomous seafloor mapping capability for deep ocean science applications. The MBARI Mapping AUV is a 0.53 m (21 in) diameter, 5.1 m (16.7 ft) long, Dorado-class vehicle designed to carry four mapping sonars. The primary sensor is a 200 kHz multibeam sonar producing swath bathymetry and sidescan. In addition, the vehicle carries 100 kHz and 410 kHz chirp sidescan sonars, and a 2-16 kHz sweep chirp subbottom profiler. Navigation and attitude data are obtained from an inertial navigation system (INS) incorporating a ring laser gyro and a 300 kHz Doppler velocity log (DVL). The vehicle also includes acoustic modem, ultra-short baseline navigation, and long-baseline navigation systems. The Mapping AUV is powered by 6 kWhr of Li-polymer batteries, providing expected mission duration of 12 hours at a typical speed of 1.5 m/s. All components of the vehicle are rated to 6000 m depth, allowing MBARI to conduct high-resolution mapping of the deep-ocean seafloor. The sonar package is also be mountable on ROV Ventana, allowing surveys at altitudes less than 20 m at topographically challenging sites. The vehicle was assembled and extensively tested during 2004; this year we are commencing operations for MBARI science projects while continuing the process of testing and integrating the complete suite of sensors and systems. MBARI is beginning to use this capability to observe the changing morphology of dynamic systems such as submarine canyons and active slumps, to map deep-water benthic habitats at resolutions comparable to ROV and submersible observations, to provide basemaps for ROV dives, and to provide high resolution bathymetry and subbottom profiles as part of a variety of projects requiring knowledge of the seafloor. We will present initial results from surveys in and around Monterey Canyon, including high resolution repeat surveys of four sites along the canyon axis.

  18. The biological carbon pump in the ocean: Reviewing model representations and its feedbacks on climate perturbations.

    Science.gov (United States)

    Hülse, Dominik; Arndt, Sandra; Ridgwell, Andy; Wilson, Jamie

    2016-04-01

    The ocean-sediment system, as the biggest carbon reservoir in the Earth's carbon cycle, plays a crucial role in regulating atmospheric carbon dioxide concentrations and climate. Therefore, it is essential to constrain the importance of marine carbon cycle feedbacks on global warming and ocean acidification. Arguably, the most important single component of the ocean's carbon cycle is the so-called "biological carbon pump". It transports carbon that is fixed in the light-flooded surface layer of the ocean to the deep ocean and the surface sediment, where it is degraded/dissolved or finally buried in the deep sediments. Over the past decade, progress has been made in understanding different factors that control the efficiency of the biological carbon pump and their feedbacks on the global carbon cycle and climate (i.e. ballasting = ocean acidification feedback; temperature dependant organic matter degradation = global warming feedback; organic matter sulphurisation = anoxia/euxinia feedback). Nevertheless, many uncertainties concerning the interplay of these processes and/or their relative significance remain. In addition, current Earth System Models tend to employ empirical and static parameterisations of the biological pump. As these parametric representations are derived from a limited set of present-day observations, their ability to represent carbon cycle feedbacks under changing climate conditions is limited. The aim of my research is to combine past carbon cycling information with a spatially resolved global biogeochemical model to constrain the functioning of the biological pump and to base its mathematical representation on a more mechanistic approach. Here, I will discuss important aspects that control the efficiency of the ocean's biological carbon pump, review how these processes of first order importance are mathematically represented in existing Earth system Models of Intermediate Complexity (EMIC) and distinguish different approaches to approximate

  19. Microbial diversity in methane hydrate-bearing deep marine sediments core preserved in the original pressure.

    Science.gov (United States)

    Takahashi, Y.; Hata, T.; Nishida, H.

    2017-12-01

    In normal coring of deep marine sediments, the sampled cores are exposed to the pressure of the atmosphere, which results in dissociation of gas-hydrates and might change microbial diversity. In this study, we analyzed microbial composition in methane hydrate-bearing sediment core sampled and preserved by Hybrid-PCS (Pressure Coring System). We sliced core into three layers; (i) outside layer, which were most affected by drilling fluids, (ii) middle layer, and (iii) inner layer, which were expected to be most preserved as the original state. From each layer, we directly extracted DNA, and amplified V3-V4 region of 16S rRNA gene. We determined at least 5000 of nucleotide sequences of the partial 16S rDNA from each layer by Miseq (Illumina). In the all layers, facultative anaerobes, which can grow with or without oxygen because they can metabolize energy aerobically or anaerobically, were detected as majority. However, the genera which are often detected anaerobic environment is abundant in the inner layer compared to the outside layer, indicating that condition of drilling and preservation affect the microbial composition in the deep marine sediment core. This study was conducted as a part of the activity of the Research Consortium for Methane Hydrate Resources in Japan [MH21 consortium], and supported by JOGMEC (Japan Oil, Gas and Metals National Corporation). The sample was provided by AIST (National Institute of Advanced Industrial Science and Technology).

  20. An upper limit to interstellar Pu-224 abundance as deduced from radiochemical search in deep-sea sediment

    International Nuclear Information System (INIS)

    Paul, M.; Valenta, A.; Ahman, I.

    2005-01-01

    Short-lived radionuclides with halflives of a few 10 7 years, now-extinct in the solar system, are expected to be present in the interstellar medium (ISM) as freshly synthesized matter in supermovae. Grains of ISM origin recently discovered in the inner solar system and at Earth orbit may accrete onto Earth after ablation in the atmosphere. As pointed out by one of the authors (K.S.) in 1974, a favorable matrix of detection of such extraterrestrial material is deep-sea sediments with very low sedimentation rates of ∼1 mm.ky -1 . We report here a search for the 'live' Pu-244 in a 1 kg-deep-sea dry sediment collected in 1992 in the North Pacific. After a 546 day a-counting of a Pu fraction chemically separated from the alkaline-fused sediment sample at Kanazawa Univ. AMS analysis was performed at Hebrew Univ. and Weizmann Institute. Only one count of Pu-244 with no background ions was detected, indicating no excess over the expected stratospheric man-made fallout. A limit of 0.2 Pu-244 atoms cm -2 .y -1 for extra terrestrial deposition was set under reasonable assumptions and it was then concluded from this result and the available data on ISM that the abundance of Pu-244 in the ISM is less than 2 X 10 -11 g-Pu-244 (g ISM) -1 . Implications of the present result will be discussed.

  1. Dominance of Epsilonproteobacteria associated with a whale fall at a 4204 m depth - South Atlantic Ocean

    Science.gov (United States)

    Cavalett, Angélica; Silva, Marcus Adonai Castro da; Toyofuku, Takashi; Mendes, Rodrigo; Taketani, Rodrigo Gouvêa; Pedrini, Jéssica; Freitas, Robert Cardoso de; Sumida, Paulo Yukio Gomes; Yamanaka, Toshiro; Nagano, Yuriko; Pellizari, Vivian Helena; Perez, José Angel Alvarez; Kitazato, Hiroshi; Lima, André Oliveira de Souza

    2017-12-01

    The deep ocean is the largest marine environment on Earth and is home to a large reservoir of biodiversity. Within the deep ocean, large organic falls attract a suite of metazoans and microorganisms, which form an important community that, in part, relies on reduced chemical compounds. Here, we describe a deep-sea (4204 m) microbial community associated with sediments collected underneath a whale fall skeleton in the South Atlantic Ocean. Metagenomic analysis of 1 Gb of Illumina HiSeq. 2000 reads, including taxonomic and functional genes, was performed by using the MG-RAST pipeline, SEED, COG and the KEGG database. The results showed that Proteobacteria (79%) was the main phylum represented. The most dominant bacterial class in this phylum was Epsilonproteobacteria (69%), and Sulfurovum sp. NBC37-1 (97%) was the dominant species. Different species of Epsilonproteobacteria have been described in marine and terrestrial environments as important organisms for nutrient cycling. Functional analysis revealed key genes for nitrogen and sulfur cycles, including protein sequences for Sox system (sulfur oxidation) enzymes. These enzymes were mainly those of the Epsilonproteobacteria, indicating their importance for nitrogen and sulfur cycles and the balance of nutrients in this environment.

  2. Global Paleobathymetry Reconstruction with Realistic Shelf-Slope and Sediment Wedge

    Science.gov (United States)

    Goswami, A.; Hinnov, L. A.; Gnanadesikan, A.; Olson, P.

    2013-12-01

    We present paleo-ocean bathymetry reconstructions in a 0.1°x0.1° resolution, using simple geophysical models (Plate Model Equation for oceanic lithosphere), published ages of the ocean floor (Müller et al. 2008), and modern world sediment thickness data (Divins 2003). The motivation is to create realistic paleobathymetry to understand the effect of ocean floor roughness on tides and heat transport in paleoclimate simulations. The values for the parameters in the Plate Model Equation are deduced from Crosby et al. (2006) and are used together with ocean floor age to model Depth to Basement. On top of the Depth to Basement, we added an isostatically adjusted multilayer sediment layer, as indicated from sediment thickness data of the modern oceans and marginal seas (Divins 2003). We also created another version of the sediment layer from the Müller et al. dataset. The Depth to Basement with the appropriate sediment layer together represent a realistic paleobathymetry. A Sediment Wedge was modeled to complement the reconstructed paleobathymetry by extending it to the coastlines. In this process we added a modeled Continental Shelf and Continental Slope to match the extent of the reconstructed paleobathymetry. The Sediment Wedge was prepared by studying the modern ocean where a complete history of seafloor spreading is preserved (north, south and central Atlantic Ocean, Southern Ocean between Australia-Antarctica, and the Pacific Ocean off the west coast of South America). The model takes into account the modern continental shelf-slope structure (as evident from ETOPO1/ETOPO5), tectonic margin type (active vs. passive margin) and age of the latest tectonic activity (USGS & CGMW). Once the complete ocean bathymetry is modeled, we combine it with PALEOMAP (Scotese, 2011) continental reconstructions to produce global paleoworld elevation-bathymetry maps. Modern time (00 Ma) was assumed as a test case. Using the above-described methodology we reconstructed modern ocean

  3. Monitoring technologies for ocean disposal of radioactive waste

    Science.gov (United States)

    Triplett, M. B.; Solomon, K. A.; Bishop, C. B.; Tyce, R. C.

    1982-01-01

    The feasibility of using carefully selected subseabed locations to permanently isolate high level radioactive wastes at ocean depths greater than 4000 meters is discussed. Disposal at several candidate subseabed areas is being studied because of the long term geologic stability of the sediments, remoteness from human activity, and lack of useful natural resources. While the deep sea environment is remote, it also poses some significant challenges for the technology required to survey and monitor these sites, to identify and pinpoint container leakage should it occur, and to provide the environmental information and data base essential to determining the probable impacts of any such occurrence. Objectives and technical approaches to aid in the selective development of advanced technologies for the future monitoring of nuclear low level and high level waste disposal in the deep seabed are presented. Detailed recommendations for measurement and sampling technology development needed for deep seabed nuclear waste monitoring are also presented.

  4. Boundary scavenging in the Pacific Ocean

    International Nuclear Information System (INIS)

    Anderson, R.F.; Lao, Y.; Broecker, W.S.; Trumbore, S.E.; Hofmann, H.J.; Wolfli, W.

    1990-01-01

    Concentrations of U, Th, 231 Pa and 10 Be were measured in Holocene sediments from two cores collected off the west coast of South America, two cores from the East Pacific Rise, two from the equatorial Pacific and one from the south Pacific central gyre. Our results, together with data from 5 cores reported in the literature, show that boundary scavenging plays a major role in the removal of 10 Be from the Pacific Ocean. Deposition rates of 10 Be at three margin sites are more than an order of magnitude greater than at sites of red clay accumulation in the deep central Pacific. Deposition of 231 Pa is 4 to 5-fold greater at the margin sites. The residence time of 10 Be with respect to chemical scavenging, defined as its inventory in the water column divided by its rate of removal to the sediments, varies regionally from >1000 years at the red-clay sites in the deep central Pacific to ∝100 years at the margin sites. Different factors control boundary scavenging of Pa and Be. For example, scavenging of 231 Pa is enhanced by metal-oxide coatings of particles, whereas this seems to have little influence on the scavenging of 10 Be. (orig.)

  5. Certified reference materials for radionuclides in Bikini Atoll sediment (IAEA-410) and Pacific Ocean sediment (IAEA-412)

    DEFF Research Database (Denmark)

    Pham, M. K.; van Beek, P.; Carvalho, F. P.

    2016-01-01

    The preparation and characterization of certified reference materials (CRMs) for radionuclide content in sediments collected offshore of Bikini Atoll (IAEA-410) and in the open northwest Pacific Ocean (IAEA-412) are described and the results of the certification process are presented. The certified...... radionuclides include: 40K, 210Pb (210Po), 226Ra, 228Ra, 228Th, 232Th, 234U, 238U, 239Pu, 239+240Pu and 241Am for IAEA-410 and 40K, 137Cs, 210Pb (210Po), 226Ra, 228Ra, 228Th, 232Th, 235U, 238U, 239Pu, 240Pu and 239+240Pu for IAEA-412. The CRMs can be used for quality assurance and quality control purposes...

  6. Long range transport of hydrocarbons in the Southern Ocean

    International Nuclear Information System (INIS)

    Pinturier, L.; Leureillard, J.; Arnold, M.; Tisnerat, N.; Pichon, J.J.; Gireaudau, J.

    1999-01-01

    We report here the first results for hydrocarbon analyses of deep surface sediments collected in the Indian sector of the Southern Ocean. The samples were taken along a north-south transect ranging from 43 deg. S to 55 deg. S in the southwestern Crozet Basin. In order to identify these compounds and elucidate their origins, various techniques were used: gas chromatography and gas chromatography coupled with mass spectrometry; Accelerator Mass Spectrometry (Tandetron: mass spectrometer coupled with a Tandem accelerator allowing the measure of 14 C/ 12 C ratio)

  7. Pelagic Iron Recycling in the Southern Ocean: Exploring the Contribution of Marine Animals

    Directory of Open Access Journals (Sweden)

    Lavenia Ratnarajah

    2018-03-01

    Full Text Available The availability of iron controls primary productivity in large areas of the Southern Ocean. Iron is largely supplied via atmospheric dust deposition, melting ice, the weathering of shelf sediments, upwelling, sediment resuspension, mixing (deep water, biogenic, and vertical mixing and hydrothermal vents with varying degrees of temporal and spatial importance. However, large areas of the Southern Ocean are remote from these sources, leading to regions of low primary productivity. Recent studies suggest that recycling of iron by animals in the surface layer could enhance primary productivity in the Southern Ocean. The aim of this review is to provide a quantitative and qualitative assessment of the current literature on pelagic iron recycling by marine animals in the Southern Ocean and highlight the next steps forward in quantifying the retention and recycling of iron by higher trophic levels in the Southern Ocean. Phytoplankton utilize the iron in seawater to meet their metabolic demand. Through grazing, pelagic herbivores transfer the iron in phytoplankton cells into their body tissues and organs. Herbivores can recycle iron through inefficient feeding behavior that release iron into the water before ingestion, and through the release of fecal pellets. The iron stored within herbivores is transferred to higher trophic levels when they are consumed. When predators consume iron beyond their metabolic demand it is either excreted or defecated. Waste products from pelagic vertebrates can thus contain high concentrations of iron which may be in a form that is available to phytoplankton. Bioavailability of fecal iron for phytoplankton growth is influenced by a combination of the size of the fecal particle, presence of organic ligands, the oxidation state of the iron, as well as biological (e.g., remineralization, coprochaly, coprorhexy, and coprophagy and physical (e.g., dissolution, fragmentation processes that lead to the degradation and release of

  8. The Search for Eight Glacial Cycles of Deep-Water Temperatures and Global ice Volume From the Southern Hemisphere

    Science.gov (United States)

    Ferretti, P.; Elderfield, H.; Greaves, M.; McCave, N.

    2007-12-01

    It has been recently suggested "a substantial portion of the marine 100-ky cycle that has been object of so much attention over the past quarter of a century is, in reality, a deep-water temperature signal and not an ice volume signal" (Shackleton, 2000). There are currently few records available of deep-water temperature variations during the Pleistocene and most of our understanding is inferred from the oxygen isotopic composition (δ18O) of benthic foraminifera from deep-sea sediments. However, variations in benthic δ18O reflect some combination of local to regional changes in water mass properties (largely deep- water temperature) as well as global changes in seawater δ18O (δ18Osw) resulting from the growth and decay of continental ice. Recent studies suggest that benthic foraminiferal Mg/Ca may be useful in reconstructing deep-water temperature changes, but the application of this method to benthic species has been hampered by a number of unresolved issues, such as uncertainties related to the calibration for benthic Mg at the coldest temperatures. Here we present deep-sea Mg/Ca and δ18O records for the past eight glacial cycles in benthic foraminiferal ( Uvigerina spp.) calcite from a marine sediment core recovered in the mid Southern latitudes. Ocean Drilling Program Site 1123 was retrieved from Chatham Rise, east of New Zealand in the Southwest Pacific Ocean (3290 m water depth). This site lies under the Deep Western Boundary Current (DWBC) that flows into the Pacific Ocean, and is responsible for most of the deep water in that ocean; DWBC strength is directly related to processes occurring around Antarctica. Temperatures derived via pore fluid modeling of the last glacial maximum are available from Site 1123 and represent an important tool to constrain deep-water temperatures estimates using Mg/Ca. In selected time slices, we measured B/Ca ratios in Uvigerina in order to gain information on the deep-water carbonate saturation state and have data of Mg

  9. Cycling of organic carbon in the ocean: use of naturally occuring radiocarbon as a long and short term tracer

    International Nuclear Information System (INIS)

    Williams, P.M.; Linick, T.W.

    1975-01-01

    The natural radiocarbon activities of surface, bathypelagic and benthic marine organisms have been measured for samples collected from the north central, north eastern and central equatorial Pacific Ocean and from the Ross Sea in Antarctica. These measurements show that 1961-1962 bomb-carbon-14 has been incorporated into the bathypelagic specimens in varying amounts. Thus, pollutants introduced into surface waters of the oceans may be removed more or less rapidly from the euphotic zone into the deep water depending upon particular food chain mechanisms. These results are discussed in relation to the cycling of disolved organic carbon, the flux of particulate organic carbon through the seawater column into the sediments, and to the oxidation rates of organic matter in the deep sea. (author)

  10. Geochemical records of salt-water inflows into the deep basins of the Baltic Sea

    DEFF Research Database (Denmark)

    Neumann, T.; Christiansen, C.; Clasen, S.

    1997-01-01

    The estuarine circulation system of the Baltic Sea promotes stable stratification and bottom water anoxia in sedimentary basins of the Baltic proper. Ingressions of saline, oxygen-rich waters from the North Sea replace the oxygen depleted deep water. Timing and extent of the ingressions vary...... on time-scales of years to decades, and are largely determined by wind-strength and storm frequency over the North Atlantic Ocean and Europe. Mn/Fe-ratios in sediments from a dated sediment core of the Gotland Deep (250 m water depth) record variations in redox conditions that can be linked to historical......-pressure areas over the North Atlantic in more recent times. The last three events have also been observed by hydrographic measurements. During the long time stagnation periods, Fe and Mn will be segregated into a particulate phase (iron sulfide) which accumulates at the seafloor and a dissolved phase (Mn2...

  11. Sedimentation

    Digital Repository Service at National Institute of Oceanography (India)

    Rixen, T.; Guptha, M.V.S.; Ittekkot, V.

    opal ratios. Such changes are assumed to have lowered the atmospheric CO sub(2) concentration significantly during glacial times. The differences between estimated deep ocean fluxes derived from satellite data and measured deep fluxes are lower than...

  12. Late Quaternary Deep Stratification-Climate Coupling in the Southern Ocean : Implications for Changes in Abyssal Carbon Storage

    NARCIS (Netherlands)

    Wu, Li; Wang, Rujian; Xiao, Wenshen; Krijgsman, Wout|info:eu-repo/dai/nl/148529763; Li, Qianyu; Ge, Shulan; Ma, Tong

    The Southern Ocean plays an important role in modulating Pleistocene atmospheric CO2 concentrations, but the underlying mechanisms are not yet fully understood. Here, we report the laser grain-size distribution and Mn geochemical data of a 523 kyr-long sediment record (core ANT30/P1-02 off Prydz

  13. Estimating carbonate parameters from hydrographic data for the intermediate and deep waters of the Southern Hemisphere oceans

    Science.gov (United States)

    Bostock, H. C.; Mikaloff Fletcher, S. E.; Williams, M. J. M.

    2013-10-01

    Using ocean carbon data from global datasets, we have developed several multiple linear regression (MLR) algorithms to estimate alkalinity and dissolved inorganic carbon (DIC) in the intermediate and deep waters of the Southern Hemisphere (south of 25° S) from only hydrographic data (temperature, salinity and dissolved oxygen). A Monte Carlo experiment was used to identify a potential density (σθ) of 27.5 as an optimal break point between the two regimes with different MLR algorithms. The algorithms provide a good estimate of DIC (R2=0.98) and alkalinity (R2=0.91), and excellent agreement for aragonite and calcite saturation states (R2=0.99). Combining the algorithms with the CSIRO Atlas of Regional Seas (CARS), we have mapped the calcite saturation horizon (CSH) and aragonite saturation horizon (ASH) for the Southern Ocean at a spatial resolution of 0.5°. These maps are more detailed and more consistent with the oceanography than the previously gridded GLODAP data. The high-resolution ASH map reveals a dramatic circumpolar shoaling at the polar front. North of 40° S the CSH is deepest in the Atlantic (~ 4000 m) and shallower in the Pacific Ocean (~ 2750 m), while the CSH sits between 3200 and 3400 m in the Indian Ocean. The uptake of anthropogenic carbon by the ocean will alter the relationships between DIC and hydrographic data in the intermediate and deep waters over time. Thus continued sampling will be required, and the MLR algorithms will need to be adjusted in the future to account for these changes.

  14. Estimating carbonate parameters from hydrographic data for the intermediate and deep waters of the Southern Hemisphere oceans

    Directory of Open Access Journals (Sweden)

    H. C. Bostock

    2013-10-01

    Full Text Available Using ocean carbon data from global datasets, we have developed several multiple linear regression (MLR algorithms to estimate alkalinity and dissolved inorganic carbon (DIC in the intermediate and deep waters of the Southern Hemisphere (south of 25° S from only hydrographic data (temperature, salinity and dissolved oxygen. A Monte Carlo experiment was used to identify a potential density (σθ of 27.5 as an optimal break point between the two regimes with different MLR algorithms. The algorithms provide a good estimate of DIC (R2=0.98 and alkalinity (R2=0.91, and excellent agreement for aragonite and calcite saturation states (R2=0.99. Combining the algorithms with the CSIRO Atlas of Regional Seas (CARS, we have mapped the calcite saturation horizon (CSH and aragonite saturation horizon (ASH for the Southern Ocean at a spatial resolution of 0.5°. These maps are more detailed and more consistent with the oceanography than the previously gridded GLODAP data. The high-resolution ASH map reveals a dramatic circumpolar shoaling at the polar front. North of 40° S the CSH is deepest in the Atlantic (~ 4000 m and shallower in the Pacific Ocean (~ 2750 m, while the CSH sits between 3200 and 3400 m in the Indian Ocean. The uptake of anthropogenic carbon by the ocean will alter the relationships between DIC and hydrographic data in the intermediate and deep waters over time. Thus continued sampling will be required, and the MLR algorithms will need to be adjusted in the future to account for these changes.

  15. Quantifying export production in the Southern Ocean: Implications for the Baxs proxy

    Science.gov (United States)

    Hernandez-Sanchez, Maria T.; Mills, Rachel A.; Planquette, HéLèNe; Pancost, Richard D.; Hepburn, Laura; Salter, Ian; Fitzgeorge-Balfour, Tania

    2011-12-01

    The water column and sedimentary Baxs distribution around the Crozet Plateau is used to decipher the controls and timing of barite formation and to evaluate how export production signals are recorded in sediments underlying a region of natural Fe fertilization within the Fe limited Southern Ocean. Export production estimated from preserved, vertical sedimentary Baxs accumulation rates are compared with published export fluxes assessed from an integrated study of the biological carbon pump to determine the validity of Baxs as a quantitative proxy under different Fe supply conditions typical of the Southern Ocean. Detailed assessment of the geochemical partitioning of Ba in sediments and the lithogenic end-member allows appropriate correction of the bulk Ba content and determination of the Baxs content of sediments and suspended particles. The upper water column distribution of Baxs is extremely heterogeneous spatially and temporally. Organic carbon/Baxs ratios in deep traps from the Fe fertilized region are similar to other oceanic settings allowing quantification of the inferred carbon export based on established algorithms. There appears to be some decoupling of POC and Ba export in the Fe limited region south of the Plateau. The export production across the Crozet Plateau inferred from the Baxs sedimentary proxy indicates that the Fe fertilized area to the north of the Plateau experiences enhanced export relative to equivalent Southern Ocean settings throughout the Holocene and that this influence may also have impacted the site to the south for significant periods. This interpretation is corroborated by alternative productivity proxies (opal accumulation, 231Paxs/230Thxs). Baxs can be used to quantify export production in complex settings such as naturally Fe-fertilized (volcanoclastic) areas, providing appropriate lithogenic correction is undertaken, and sediment focusing is corrected for along with evaluation of barite preservation.

  16. Spatial Vertical Directionality and Correlation of Low-Frequency Ambient Noise in Deep Ocean Direct-Arrival Zones

    Directory of Open Access Journals (Sweden)

    Qiulong Yang

    2018-01-01

    Full Text Available Wind-driven and distant shipping noise sources contribute to the total noise field in the deep ocean direct-arrival zones. Wind-driven and distant shipping noise sources may significantly and simultaneously affect the spatial characteristics of the total noise field to some extent. In this work, a ray approach and parabolic equation solution method were jointly utilized to model the low-frequency ambient noise field in a range-dependent deep ocean environment by considering their calculation accuracy and efficiency in near-field wind-driven and far-field distant shipping noise fields. The reanalysis databases of National Center of Environment Prediction (NCEP and Volunteer Observation System (VOS were used to model the ambient noise source intensity and distribution. Spatial vertical directionality and correlation were analyzed in three scenarios that correspond to three wind speed conditions. The noise field was dominated by distant shipping noise sources when the wind speed was less than 3 m/s, and then the spatial vertical directionality and vertical correlation of the total noise field were nearly consistent with those of distant shipping noise field. The total noise field was completely dominated by near field wind generated noise sources when the wind speed was greater than 12 m/s at 150 Hz, and then the spatial vertical correlation coefficient and directionality pattern of the total noise field was approximately consistent with that of the wind-driven noise field. The spatial characteristics of the total noise field for wind speeds between 3 m/s and 12 m/s were the weighted results of wind-driven and distant shipping noise fields. Furthermore, the spatial characteristics of low-frequency ambient noise field were compared with the classical Cron/Sherman deep water noise field coherence function. Simulation results with the described modeling method showed good agreement with the experimental measurement results based on the vertical line

  17. Spatial Vertical Directionality and Correlation of Low-Frequency Ambient Noise in Deep Ocean Direct-Arrival Zones

    Science.gov (United States)

    Yang, Qiulong; Yang, Kunde; Cao, Ran; Duan, Shunli

    2018-01-01

    Wind-driven and distant shipping noise sources contribute to the total noise field in the deep ocean direct-arrival zones. Wind-driven and distant shipping noise sources may significantly and simultaneously affect the spatial characteristics of the total noise field to some extent. In this work, a ray approach and parabolic equation solution method were jointly utilized to model the low-frequency ambient noise field in a range-dependent deep ocean environment by considering their calculation accuracy and efficiency in near-field wind-driven and far-field distant shipping noise fields. The reanalysis databases of National Center of Environment Prediction (NCEP) and Volunteer Observation System (VOS) were used to model the ambient noise source intensity and distribution. Spatial vertical directionality and correlation were analyzed in three scenarios that correspond to three wind speed conditions. The noise field was dominated by distant shipping noise sources when the wind speed was less than 3 m/s, and then the spatial vertical directionality and vertical correlation of the total noise field were nearly consistent with those of distant shipping noise field. The total noise field was completely dominated by near field wind generated noise sources when the wind speed was greater than 12 m/s at 150 Hz, and then the spatial vertical correlation coefficient and directionality pattern of the total noise field was approximately consistent with that of the wind-driven noise field. The spatial characteristics of the total noise field for wind speeds between 3 m/s and 12 m/s were the weighted results of wind-driven and distant shipping noise fields. Furthermore, the spatial characteristics of low-frequency ambient noise field were compared with the classical Cron/Sherman deep water noise field coherence function. Simulation results with the described modeling method showed good agreement with the experimental measurement results based on the vertical line array deployed near

  18. Shallow and Deep Latent Heating Modes Over Tropical Oceans Observed with TRMM PR Spectral Latent Heating Data

    Science.gov (United States)

    Takayabu, Yukari N.; Shige, Shoichi; Tao, Wei-Kuo; Hirota, Nagio

    2010-01-01

    The global hydrological cycle is central to the Earth's climate system, with rainfall and the physics of its formation acting as the key links in the cycle. Two-thirds of global rainfall occurs in the Tropics. Associated with this rainfall is a vast amount of heat, which is known as latent heat. It arises mainly due to the phase change of water vapor condensing into liquid droplets; three-fourths of the total heat energy available to the Earth's atmosphere comes from tropical rainfall. In addition, fresh water provided by tropical rainfall and its variability exerts a large impact upon the structure and motions of the upper ocean layer. Three-dimensional distributions of latent heating estimated from Tropical Rainfall Measuring Mission Precipitation Radar (TRMM PR)utilizing the Spectral Latent Heating (SLH) algorithm are analyzed. Mass-weighted and vertically integrated latent heating averaged over the tropical oceans is estimated as approx.72.6 J/s (approx.2.51 mm/day), and that over tropical land is approx.73.7 J/s (approx.2.55 mm/day), for 30degN-30degS. It is shown that non-drizzle precipitation over tropical and subtropical oceans consists of two dominant modes of rainfall systems, deep systems and congestus. A rough estimate of shallow mode contribution against the total heating is about 46.7 % for the average tropical oceans, which is substantially larger than 23.7 % over tropical land. While cumulus congestus heating linearly correlates with the SST, deep mode is dynamically bounded by large-scale subsidence. It is notable that substantial amount of rain, as large as 2.38 mm day-1 in average, is brought from congestus clouds under the large-scale subsiding circulation. It is also notable that even in the region with SST warmer than 28 oC, large-scale subsidence effectively suppresses the deep convection, remaining the heating by congestus clouds. Our results support that the entrainment of mid-to-lower-tropospheric dry air, which accompanies the large

  19. The concentration of "1"3"7Cs and organic carbon on sediment at Rat island in Indian ocean

    International Nuclear Information System (INIS)

    Muslim; Reza Agung Arjana; Wahyu Retno Prihatiningsih

    2016-01-01

    Rat Island is one of the islands in Indonesia, located in the Indian Ocean, about 10 kilometers west of Bengkulu, which has a beautiful scenery both on its land and on the seabed, making it a favorite tourist in Bengkulu. The purpose of this study was to determine the condition of "1"3"7Cs in sediments and its relation to the total carbon and sediment texture. Sediment sampling carried out on 17 September 2014 at six stations where three stations are still relatively close to The Rat island with water depth of ≤ 1 m and 3 others are far from Rat Island waters with a depth of 14-18 meters. Sediment texture and TOC content at waters depth of ≤ 1 m is sand and its TOC contents were <5.5%. On other hand at water depth of 14-18 meters sediment texture are silt sand mixture and the TOC content were ≥6%. The concentration of "1"3"7Cs in sediment were influenced by texture characteristic and TOC content. (author)

  20. Metal release from contaminated coastal sediments under changing pH conditions: Implications for metal mobilization in acidified oceans.

    Science.gov (United States)

    Wang, Zaosheng; Wang, Yushao; Zhao, Peihong; Chen, Liuqin; Yan, Changzhou; Yan, Yijun; Chi, Qiaoqiao

    2015-12-30

    To investigate the impacts and processes of CO2-induced acidification on metal mobilization, laboratory-scale experiments were performed, simulating the scenarios where carbon dioxide was injected into sediment-seawater layers inside non-pressurized chambers. Coastal sediments were sampled from two sites with different contamination levels and subjected to pre-determined pH conditions. Sediment samples and overlying water were collected for metal analysis after 10-days. The results indicated that CO2-induced ocean acidification would provoke increased metal mobilization causing adverse side-effects on water quality. The mobility of metals from sediment to the overlying seawater was correlated with the reduction in pH. Results of sequential extractions of sediments illustrated that exchangeable metal forms were the dominant source of mobile metals. Collectively, our data revealed that high metal concentrations in overlying seawater released from contaminated sediments under acidic conditions may strengthen the existing contamination gradients in Maluan Bay and represent a potential risk to ecosystem health in coastal environments. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Increased terrestrial to ocean sediment and carbon fluxes in the northern Chesapeake Bay associated with twentieth century land alteration

    Science.gov (United States)

    Saenger, C.; Cronin, T. M.; Willard, D.; Halka, J.; Kerhin, R.

    2008-01-01

    We calculated Chesapeake Bay (CB) sediment and carbon fluxes before and after major anthropogenic land clearance using robust monitoring, modeling and sedimentary data. Four distinct fluxes in the estuarine system were considered including (1) the flux of eroded material from the watershed to streams, (2) the flux of suspended sediment at river fall lines, (3) the burial flux in tributary sediments, and (4) the burial flux in main CB sediments. The sedimentary maximum in Ambrosia (ragweed) pollen marked peak land clearance (~1900 a.d.). Rivers feeding CB had a total organic carbon (TOC)/total suspended solids of 0.24??0.12, and we used this observation to calculate TOC fluxes from sediment fluxes. Sediment and carbon fluxes increased by 138-269% across all four regions after land clearance. Our results demonstrate that sediment delivery to CB is subject to significant lags and that excess post-land clearance sediment loads have not reached the ocean. Post-land clearance increases in erosional flux from watersheds, and burial in estuaries are important processes that must be considered to calculate accurate global sediment and carbon budgets. ?? 2008 Coastal and Estuarine Research Federation.

  2. Sorption of redox-sensitive radionuclides to deep-sea sediments in the absence of oxygen

    International Nuclear Information System (INIS)

    Higgo, J.J.W.; Rees, L.V.C.; Cronan, D.S.; Cole, T.G.

    1986-03-01

    Sediments were recovered from the GME area of the mid-Atlantic and stored in an inert atmosphere from the time of collection Pore-water analysis showed them to be post-oxic. Sorption tests in an inert atmosphere showed that they were not sufficiently reducing to affect the distribution ratios of the redox-sensitive elements, technetium and neptunium. This may mean that previous results obtained under oxic conditions can be used in modelling. Ferrous iron was strongly sorbed onto the sediments but this iron had no effect on technetium sorption, which was negligible. Only if a large excess of Fe ++ was added so that the concentration of Fe ++ in solution exceeded 100um (Eh probably < -0.2V) was the technetium reduced and adsorption appreciable. The indications are, therefore, that ferrous iron from dissolved canisters will not increase the sorption of technetium to deep-sea sediments. Moessbauer analysis showed that a high proportion (up to 15%) of the iron in the high-carbonate turbidites was in the ferrous state but that all the iron in the clay-rich layer, containing less carbonate, was in the ferric state. This may explain the fact that, in general, neptunium is more strongly adsorbed by high-carbonate than by other types of sediment. (author)

  3. Literature Review of Unconsolidated Sediment in San Francisco Bay and Nearby Pacific Ocean Coast

    Directory of Open Access Journals (Sweden)

    Barry R. Keller

    2009-09-01

    Full Text Available A review of the geologic literature regarding sedimentation in the San Francisco Bay estuarine system shows that the main part of the bay occupies a structural tectonic depression that developed in Pleistocene time. Eastern parts, including San Pablo Bay and Suisun Bay, have had sedimentation throughout late Mesozoic and Tertiary. Carquinez Strait and the Golden Gate may represent antecedent stream erosion. Sedimentation has included estuarine, alluvial, and eolian deposition. The ages of estuarine deposition includes the modern high sea level stand and earlier Pleistocene interglacial periods. Sediment sources can be generally divided into the Coast Ranges, particularly the Franciscan Complex, and “Sierran.” Much of the estuarine system is floored by very fine sediment, with local areas of sand floor. Near the Golden Gate, sediment size decreases in both directions away from the deep channel. Bedforms include sand waves (submarine dunes, flat beds, and rock and boulders. These are interpreted in terms of dominant transport directions. Near the Golden Gate is an ebb-tidal delta on the outside (including San Francisco bar and a flood-tidal delta on the inside (parts of Central Bay. The large tidal prism causes strong tidal currents, which in the upper part of the estuary are normally much stronger than river currents, except during large floods. Cultural influences have altered conditions, including hydraulic mining debris, blasting of rocks, dredging of navigation channels, filling of the bay, and commercial sand mining. Many of these have served to decrease the tidal prism, correspondingly decreasing the strength of tidal currents.

  4. Past climate clues from anoxic basin sediments: Cariaco basin (Venezuela) as a tropical climate type section

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, L.C.

    2008-07-01

    This paper discusses how anoxic conditions in deep oceans are the result of a dynamic balance between oxygen supply and oxygen consumption. The author states that a significant consequence of ancient anoxic episodes was that the accumulation and preservation of organic matter in marine sediments were greatly enhanced, allowing the generation of potential petroleum source rocks. Changes in climatic conditions both in the short term as well as over longer periods of time are examined on the basis of oxygen isotope quantities found in ice-cores drilled in Greenland. The influence of these climatic changes on anoxic conditions in the oceans is discussed.

  5. Climate control on late Holocene high-energy sedimentation along coasts of the northeastern Atlantic Ocean

    OpenAIRE

    Poirier , Clément; Tessier , Bernadette; Chaumillon , Eric

    2017-01-01

    International audience; Abundant sedimentological and geochronological data gathered on European sandy coasts highlight major phases of increased high-energy sedimentation in the North Atlantic Ocean during the late Holocene. Owing to an inconsistent use of the terminology, it is often difficult to determine whether studies have described storm-built or wave-built deposits. Both deposits can be identified by overall similar coarse-grained sedimentary facies, but may provide contradictory pale...

  6. Fate of copper complexes in hydrothermally altered deep-sea sediments from the Central Indian Ocean Basin.

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, P.; Sander, S.G.; Jayachandran, S.; Nath, B.N.; Nagaraju, G.; Chennuri, K.; Vudamala, K.; Lathika, N.; Mascarenhas-Pereira, M.B.L.

    concentrations of TOC in the studied sediments reduced the concentrations of Cu associated with organic matter in all the studied sediments. Cu present as residual fraction (Fraction 4, Cures) were within the range of (~ 58-82%) and possibly bound to sulphides... Fraction 2 CuFe Fraction 3 CuCorg Fraction 4 Cures Cu- Feox1 Cu- Feox2 Cu- Femag AAS-61 BC 8 4-10cm 354±6 0.3±1 40.7±3.1 0.3±0.1 58.5±3.2 69.3±4.6 29.7±1.2 1.0±0.2 10-15cm 253±7 0.1±0.1 20.7±2.5 0.0 79.2±5.8 63.0±3.2 33.9±2.2 3...

  7. Nematode communities in sediments of the Kermadec Trench, Southwest Pacific Ocean

    Science.gov (United States)

    Leduc, Daniel; Rowden, Ashley A.

    2018-04-01

    Hadal trenches are characterized by environmental conditions not found in any other deep-sea environment, such as steep topography and periodic disturbance by turbidity flows, which are likely responsible for the distinct nature of benthic communities of hadal trenches relative to those of the abyssal plain. Nematodes are the most abundant metazoans in the deep-sea benthos, but it is not yet clear if different trenches host distinct nematode communities, and no data are yet available on the communities of most trenches, including the Kermadec Trench in the Southwest Pacific. Quantitative core samples from the seafloor of the Kermadec Trench were recently obtained from four sites at 6000-9000 m depth which allowed for analyses of meiofauna, and nematodes in particular, for the first time. Nematode community and trophic structure was also compared with other trenches using published data. There was a bathymetric gradient in meiofauna abundance, biomass, and community structure within the Kermadec Trench, but patterns for species richness were ambiguous depending on which metric was used. There was a change in community structure from shallow to deep sites, as well as a consistent change in community structure from the upper sediment layers to the deeper sediment layers across the four sites. These patterns are most likely explained by variation in food availability within the trench, and related to trench topography. Together, deposit and microbial feeders represented 48-92% of total nematode abundance in the samples, which suggests that fine organic detritus and bacteria are major food sources. The relatively high abundance of epigrowth feeders at the 6000 and 9000 m sites (38% and 31%, respectively) indicates that relatively freshly settled microalgal cells represent another important food source at these sites. We found a significant difference in species community structure between the Kermadec and Tonga trenches, which was due to both the presence/absence of

  8. Rare earth element geochemistry of South Atlantic deep sea sediments: Ce anomaly change at approx. 54 My

    International Nuclear Information System (INIS)

    Wang, Y.L.; Liu, Y.-G.; Schmitt, R.A.; Oregon State Univ., Corvallis; Oregon State Univ., Corvallis; Oregon State Univ., Corvallis

    1986-01-01

    The geochemistry of the REE (rare earth elements) in oceanic sediments is discussed, based mainly on samples from DSDP Holes 530A and 530B, Leg 75, and Hole 525A, Leg 74. The proposed mechanisms for incorporation of the REE into the marine carbonate phases are adsorption, chiefly onto the carbonate minerals and on Sc, Hf, and Ta-rich FE-Mn hydroxide flocs as carbonate coatings. The Ce anomaly of marine carbonate was used as an indicator of paleo-ocean water redox conditions: the bottom water of the Angola Basin was in a reducing condition in the Cretaceous. At ca. 54 My, the South Atlantic water condition became oxidizing, similar to the present seawater redox condition. This change was related to the improvement of circulation due to the widening of South Atlantic and the subsidence of water circulation barriers such as the Walvis Ridge and perhaps the Romanche Fracture Zone. The REE abundances and patterns of younger sediments in the Angola Basin (YSAB) are very similar to those observed in NASC, PAAS, and ES sediments. The YSAB REE abundances and patterns may represent the average REE distribution of the exposed African continental crust. The strong resemblance of REE distributions of YSAB, NASC, PAAS and ES suggests thorough REE mixing from different sources and the uniformity of the average crustal compositions of different continents: Africa, North America, Australia, and Europe. (author)

  9. Does seismic activity control carbon exchanges between transform-faults in old ocean crust and the deep sea? A hypothesis examined by the EU COST network FLOWS

    Science.gov (United States)

    Lever, M. A.

    2014-12-01

    The European Cooperation in Science and Technology (COST)-Action FLOWS (http://www.cost.eu/domains_actions/essem/Actions/ES1301) was initiated on the 25th of October 2013. It is a consortium formed by members of currently 14 COST countries and external partners striving to better understand the interplay between earthquakes and fluid flow at transform-faults in old oceanic crust. The recent occurrence of large earthquakes and discovery of deep fluid seepage calls for a revision of the postulated hydrogeological inactivity and low seismic activity of old oceanic transform-type plate boundaries, and indicates that earthquakes and fluid flow are intrinsically associated. This Action merges the expertise of a large number of research groups and supports the development of multidisciplinary knowledge on how seep fluid (bio)chemistry relates to seismicity. It aims to identify (bio)geochemical proxies for the detection of precursory seismic signals and to develop innovative physico-chemical sensors for deep-ocean seismogenic faults. National efforts are coordinated through Working Groups (WGs) focused on 1) geophysical and (bio)geochemical data acquisition; 2) modelling of structure and seismicity of faults; 3) engineering of deep-ocean physico-chemical seismic sensors; and 4) integration and dissemination. This poster will illustrate the overarching goals of the FLOWS Group, with special focus to research goals concerning the role of seismic activity in controlling the release of carbon from the old ocean crust into the deep ocean.

  10. Comparison of the anaerobic microbiota of deep-water Geodia spp. and sandy sediments in the Straits of Florida.

    Science.gov (United States)

    Brück, Wolfram M; Brück, Thomas B; Self, William T; Reed, John K; Nitecki, Sonja S; McCarthy, Peter J

    2010-05-01

    Marine sediments and sponges may show steep variations in redox potential, providing niches for both aerobic and anaerobic microorganisms. Geodia spp. and sediment specimens from the Straits of Florida were fixed using paraformaldehyde and 95% ethanol (v/v) for fluorescence in situ hybridization (FISH). In addition, homogenates of sponge and sediment samples were incubated anaerobically on various cysteine supplemented agars. FISH analysis showed a prominent similarity of microbiota in sediments and Geodia spp. samples. Furthermore, the presence of sulfate-reducing and annamox bacteria as well as other obligate anaerobic microorganisms in both Geodia spp. and sediment samples were also confirmed. Anaerobic cultures obtained from the homogenates allowed the isolation of a variety of facultative anaerobes, primarily Bacillus spp. and Vibrio spp. Obligate anaerobes such as Desulfovibrio spp. and Clostridium spp. were also found. We also provide the first evidence for a culturable marine member of the Chloroflexi, which may enter into symbiotic relationships with deep-water sponges such as Geodia spp. Resuspended sediment particles, may provide a source of microorganisms able to associate or form a symbiotic relationship with sponges.

  11. Clay mineralogy, strontium and neodymium isotope ratios in the sediments of two High Arctic catchments (Svalbard)

    Science.gov (United States)

    Hindshaw, Ruth S.; Tosca, Nicholas J.; Piotrowski, Alexander M.; Tipper, Edward T.

    2018-03-01

    The identification of sediment sources to the ocean is a prerequisite to using marine sediment cores to extract information on past climate and ocean circulation. Sr and Nd isotopes are classical tools with which to trace source provenance. Despite considerable interest in the Arctic Ocean, the circum-Arctic source regions are poorly characterised in terms of their Sr and Nd isotopic compositions. In this study we present Sr and Nd isotope data from the Paleogene Central Basin sediments of Svalbard, including the first published data of stream suspended sediments from Svalbard. The stream suspended sediments exhibit considerable isotopic variation (ɛNd = -20.6 to -13.4; 87Sr / 86Sr = 0.73421 to 0.74704) which can be related to the depositional history of the sedimentary formations from which they are derived. In combination with analysis of the clay mineralogy of catchment rocks and sediments, we suggest that the Central Basin sedimentary rocks were derived from two sources. One source is Proterozoic sediments derived from Greenlandic basement rocks which are rich in illite and have high 87Sr / 86Sr and low ɛNd values. The second source is Carboniferous to Jurassic sediments derived from Siberian basalts which are rich in smectite and have low 87Sr / 86Sr and high ɛNd values. Due to a change in depositional conditions throughout the Paleogene (from deep sea to continental) the relative proportions of these two sources vary in the Central Basin formations. The modern stream suspended sediment isotopic composition is then controlled by modern processes, in particular glaciation, which determines the present-day exposure of the formations and therefore the relative contribution of each formation to the stream suspended sediment load. This study demonstrates that the Nd isotopic composition of stream suspended sediments exhibits seasonal variation, which likely mirrors longer-term hydrological changes, with implications for source provenance studies based on fixed

  12. The deep biosphere in terrestrial sediments in the chesapeake bay area, virginia, USA.

    Science.gov (United States)

    Breuker, Anja; Köweker, Gerrit; Blazejak, Anna; Schippers, Axel

    2011-01-01

    For the first time quantitative data on the abundance of Bacteria, Archaea, and Eukarya in deep terrestrial sediments are provided using multiple methods (total cell counting, quantitative real-time PCR, Q-PCR and catalyzed reporter deposition-fluorescence in situ hybridization, CARD-FISH). The oligotrophic (organic carbon content of ∼0.2%) deep terrestrial sediments in the Chesapeake Bay area at Eyreville, Virginia, USA, were drilled and sampled up to a depth of 140 m in 2006. The possibility of contamination during drilling was checked using fluorescent microspheres. Total cell counts decreased from 10(9) to 10(6) cells/g dry weight within the uppermost 20 m, and did not further decrease with depth below. Within the top 7 m, a significant proportion of the total cell counts could be detected with CARD-FISH. The CARD-FISH numbers for Bacteria were about an order of magnitude higher than those for Archaea. The dominance of Bacteria over Archaea was confirmed by Q-PCR. The down core quantitative distribution of prokaryotic and eukaryotic small subunit ribosomal RNA genes as well as functional genes involved in different biogeochemical processes was revealed by Q-PCR for the uppermost 10 m and for 80-140 m depth. Eukarya and the Fe(III)- and Mn(IV)-reducing bacterial group Geobacteriaceae were almost exclusively found in the uppermost meter (arable soil), where reactive iron was detected in higher amounts. The bacterial candidate division JS-1 and the classes Anaerolineae and Caldilineae of the phylum Chloroflexi, highly abundant in marine sediments, were found up to the maximum sampling depth in high copy numbers at this terrestrial site as well. A similar high abundance of the functional gene cbbL encoding for the large subunit of RubisCO suggests that autotrophic microorganisms could be relevant in addition to heterotrophs. The functional gene aprA of sulfate reducing bacteria was found within distinct layers up to ca. 100 m depth in low copy numbers

  13. Gas production potential of disperse low-saturation hydrate accumulations in oceanic sediments

    International Nuclear Information System (INIS)

    Moridis, George J.; Sloan, E. Dendy

    2007-01-01

    In this paper, we evaluate the gas production potential of disperse, low-saturation (S H H hydrate-bearing sediments subject to depressurization-induced dissociation over a 10-year production period. We investigate the sensitivity of items (a)-(c) to the following hydraulic properties, reservoir conditions, and operational parameters: intrinsic permeability, porosity, pressure, temperature, hydrate saturation, and constant pressure at which the production well is kept. The results of this study indicate that, despite wide variations in the aforementioned parameters (covering the entire spectrum of such deposits), gas production is very limited, never exceeding a few thousand cubic meters of gas during the 10-year production period. Such low production volumes are orders of magnitude below commonly accepted standards of economic viability, and are further burdened with very unfavorable gas-to-water ratios. The unequivocal conclusion from this study is that disperse, low-S H hydrate accumulations in oceanic sediments are not promising targets for gas production by means of depressurization-induced dissociation, and resources for early hydrate exploitation should be focused elsewhere

  14. Recent sediment dynamics in hadal trenches: Evidence for the influence of higher-frequency (tidal, near-inertial) fluid dynamics

    Science.gov (United States)

    Turnewitsch, Robert; Falahat, Saeed; Stehlikova, Jirina; Oguri, Kazumasa; Glud, Ronnie N.; Middelboe, Mathias; Kitazato, Hiroshi; Wenzhöfer, Frank; Ando, Kojiro; Fujio, Shinzou; Yanagimoto, Daigo

    2014-08-01

    In addition to high hydrostatic pressure, scarcity of food is viewed as a factor that limits the abundance and activity of heterotrophic organisms at great ocean depths, including hadal trenches. Supply of nutritious food largely relies on the flux of organic-rich particulate matter from the surface ocean. It has been speculated that the shape of hadal trenches helps to ‘funnel' particulate matter into the deeper parts of the trench, leading to sediment ‘focussing' and improved benthic food supply. Here we investigate for five Northwest Pacific trenches the efficiency of sediment focussing by evaluating ratios of measured (sediment-derived) and expected (water-column-derived) sedimentary inventories of the naturally occurring and radioactive particulate-matter tracer 210Pbxs. The sites comprise a broad range of surface-ocean productivity and physical-oceanographic regimes. Across the five trench-axis settings the inventory ratio varies between 0.5 and 4.1, with four trench-axis settings having ratios>1 (sediment focussing) and one trench-axis setting a ratiowinnowing). Although the fluid- and sediment-dynamical forcing behind sediment focussing remains unclear, this study finds evidence for another mechanism that is superimposed on, and counteracts, the focussing mechanism. This superimposed mechanism is related to higher-frequency (tidal, near-inertial) fluid dynamics. In particular, there is evidence for a strong and negative relation between the intensity of propagating internal tides and the extent of sediment focussing in the trench-axis. The relation can be approximated by a power function and the most intense drop in sediment focussing already occurs at moderate internal-tide intensities. This suggests that propagating internal tides may have a subtle but significant influence on particulate-matter dynamics and food supply in hadal trenches in particular, but possibly also in the deep seas in general. A mechanism for the influence of internal tides on

  15. Antagonistic Effects of Ocean Acidification and Rising Sea Surface Temperature on the Dissolution of Coral Reef Carbonate Sediments

    Directory of Open Access Journals (Sweden)

    Daniel Trnovsky

    2016-11-01

    Full Text Available Increasing atmospheric CO2 is raising sea surface temperature (SST and increasing seawater CO2 concentrations, resulting in a lower oceanic pH (ocean acidification; OA, which is expected to reduce the accretion of coral reef ecosystems. Although sediments comprise most of the calcium carbonate (CaCO3 within coral reefs, no in situ studies have looked at the combined effects of increased SST and OA on the dissolution of coral reef CaCO3 sediments. In situ benthic chamber incubations were used to measure dissolution rates in permeable CaCO3 sands under future OA and SST scenarios in a coral reef lagoon on Australia’s Great Barrier Reef (Heron Island. End of century (2100 simulations (temperature +2.7°C and pH -0.3 shifted carbonate sediments from net precipitating to net dissolving. Warming increased the rate of benthic respiration (R by 29% per 1°C and lowered the ratio of productivity to respiration (P/R; ΔP/R = -0.23, which increased the rate of CaCO3 sediment dissolution (average net increase of 18.9 mmol CaCO3 m-2 d-1 for business as usual scenarios. This is most likely due to the influence of warming on benthic P/R which, in turn, was an important control on sediment dissolution through the respiratory production of CO2. The effect of increasing CO2 on CaCO3 sediment dissolution (average net increase of 6.5 mmol CaCO3 m-2 d-1 for business as usual scenarios was significantly less than the effect of warming. However, the combined effect of increasing both SST and pCO2 on CaCO3 sediment dissolution was non-additive (average net increase of 5.6 mmol CaCO3 m-2 d-1 due to the different responses of the benthic community. This study highlights that benthic biogeochemical processes such as metabolism and associated CaCO3 sediment dissolution respond rapidly to changes in SST and OA, and that the response to multiple environmental changes are not necessarily additive.

  16. Genetic homogeneity in the deep-sea grenadier Macrourus berglax across the North Atlantic Ocean

    Science.gov (United States)

    Coscia, Ilaria; Castilho, Rita; Massa-Gallucci, Alexia; Sacchi, Carlotta; Cunha, Regina L.; Stefanni, Sergio; Helyar, Sarah J.; Knutsen, Halvor; Mariani, Stefano

    2018-02-01

    Paucity of data on population structure and connectivity in deep sea species remains a major obstacle to their sustainable management and conservation in the face of ever increasing fisheries pressure and other forms of impacts on deep sea ecosystems. The roughhead grenadier Macrourus berglax presents all the classical characteristics of a deep sea species, such as slow growth and low fecundity, which make them particularly vulnerable to anthropogenic impact, due to their low resilience to change. In this study, the population structure of the roughhead grenadier is investigated throughout its geographic distribution using two sets of molecular markers: a partial sequence of the Control Region of mitochondrial DNA and species-specific microsatellites. No evidence of significant structure was found throughout the North Atlantic, with both sets of molecular markers yielding the same results of overall homogeneity. We posit two non-mutually exclusive scenarios that can explain such outcome: i) substantial high gene flow among locations, possibly maintained by larval stages, ii) very large effective size of post-glacially expanded populations. The results can inform management strategies in this by-caught species, and contribute to the broader issue of biological connectivity in the deep ocean.

  17. Apparent changes in the climatic state of the deep North Atlantic Ocean

    Energy Technology Data Exchange (ETDEWEB)

    Roemmich, D; Wunsch, C

    1984-02-01

    Determination of any long-term changes in the large-scale characteristics of the deep ocean circulation would be an important clue in understanding the climatic interactions of the ocean and atmosphere. In the summer of 1981, the RV Atlantis II reoccupied two transatlantic sections at nominal latitudes of 24/sup 0/30'N and 36/sup 0/16'N with a conductivity-temperature-depth instrument (CTD). One purpose of the work was to make a comparison with previous surveys conducted during the International Geophysical Year (IGY), when sections were obtained in October 1957 and April-May 1959. The authors report here that significant warming occurred in an ocean-wide band from 700 m to 3,000 m with a maximum temperature difference of 0.2 ..pi..C. These changes are sufficient to expand the water column by several centimeters. The historical temperature-salinity curve was apparently unchanged. Interannual changes in local water mass characteristics have been proposed previously. Perhaps it would be most surprising if no changes were seen to occur. What remains obscure is the significance of these changes and the extent to which they represent long-term climate trends, or merely the minor and random fluctuations to be expected in any complex fluid system.

  18. Geochemistry of sediments

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B.N.

    Considering the potential of elemental data in marine sediments as diagnostic tools of various geological and oceanographic processes, sediment geochemical data from the Indian Ocean region has been reviewed in this article. Emphasis is laid...

  19. Fatty acids in sediments and phytoplankton data were collected from the Equatorial Pacific Ocean as part of the Joint Global Ocean Flux Study/Equatorial Pacific Basin Study (JGOFS/EQPAC) project., from 1992-02-03 to 1992-12-13 (NODC Accession 9700180)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Fatty acids in sediments and phytoplankton data were collected using plankton tow, sediments sampler - corer, pump and CTD casts from the R/V THOMAS THOMPSON in the...

  20. Early diagenesis in the Congo deep-sea fan sediments dominated by massive terrigenous deposits: Part I - Oxygen consumption and organic carbon mineralization using a micro-electrode approach

    Science.gov (United States)

    Pozzato, Lara; Cathalot, Cécile; Berrached, Chabha; Toussaint, Flora; Stetten, Elsa; Caprais, Jean-Claude; Pastor, Lucie; Olu, Karine; Rabouille, Christophe

    2017-08-01

    Organic matter (OM) transfer from the continent to the ocean occurs across margins which constitute a major area of OM recycling and burial. The lobe complex of the Congo deep-sea fan is connected to the river mouth by a canyon and alimented by recurrent turbidity currents, containing a large proportion of labile terrigenous OM and producing high sedimentation rates. These inputs support the development of ecosystems harboring rich assemblages of vesicomyid bivalves and bacterial mats, called Habitats. Here, we present O2 microprofiles and diffusive oxygen uptake rates (DOUs) obtained during the CONGOLOBE project at six sites of this active lobe complex by in situ and on-board methods based on micro-electrode profiling. The dataset is used to determine remineralization rates and study the biogeochemical dynamics of different ecosystems of the lobe area, in order to compare levee and background sediments to the Habitats developed on the flanks of the main turbiditic channel. Levee and background sediments are characterized by significantly higher DOUs than abyssal sediments at 5000 m meters depth (2-5 mmol O2 m-2 d-1versus 1.5-2.5 mmol O2 m-2 d-1) and the Habitats are hotspots of OM remineralization with DOU values ranging between 8 and 40 mmol O2 m-2 d-1. By comparing sites near the active channel to a site located 50 km away, we show that the lobe connection to the main turbiditic channel is vital to the dense benthic communities.

  1. Sediment resuspension events induced by the wake wash of deep-draft vessels

    Science.gov (United States)

    Garel, Erwan; López Fernández, Laura; Collins, Mike

    2008-08-01

    Hydrodynamics and sediment resuspension events, induced at the shoreline by a deep-draft vessel passing nearby, are described. Measurements (pressure, currents and turbidity) were obtained at 4 Hz, on a lower beach ~50 m from a channel where large car ferries operate in Wootton Creek, Isle of Wight. The study focuses on a representative 8-min 32-s-long record, during which two large vessels passed the channel section. At the shore, the passage of each vessel induced a long-period water-level drawdown, followed by a water-level oscillation (seiche) of similar period, and the short-period waves of the wake. Both drawdowns were the main constituents of the prevailing wave pattern. The second drawdown was the largest in amplitude, in response to a higher speed of the ferry, and the influence of the seiche which had been activated during the preceding event. Two successive peaks of turbidity were observed shortly after this drawdown. Analyses of current velocity and direction indicate that the sediments resuspended originated from the shallower upper beach. Anthropogenically induced erosion of the foreshore is predicted at Wootton Creek.

  2. Gas hydrate formation in deep-sea sediments - on the role of sediment-mechanical process determination; Gashydratbildung in Tiefseesedimenten - zur Rolle der sedimentmechanischen Prozesssteuerung

    Energy Technology Data Exchange (ETDEWEB)

    Feeser, V. [Kiel Univ. (Germany). Geologisch-Palaeontologisches Inst.

    1997-12-31

    Slope failures in gas hydrate regions are encountered throughout the oceans. The stability of seafloor slopes can be assessed and predicted by means of calculation methods based on mechanical laws and parameters which describe the deformation behaviour and/or mechanical strength of the slope-forming sediments. Thermodynamic conditions conducive to the formation of gas hydrates in marine sediments differ from conditions prevailing in exclusively water-filled systems. The present contribution describes the relevant energetic conditions on the basis of a simple spherical model giving due consideration to petrographic parameters. Depending on pore size distribution, lithological stress conditions, pore water pressure, and sediment strength gas hydrates will either develop as a cementing phase or as segregated lenses. (MSK) [Deutsch] In den Weltmeeren ereignen sich immer wieder Hangrutschungen in Gashydratgebieten. Die zur Beurteilung und Prognonse von Hangstabilitaeten zu verwendenden Berechnungsverfahren erfordern Stoffgesetze und Parameter, welche das Deformations-und/oder Festigkeitsverhalten der hangbildenden Sedimente beschreiben. Die thermodynamischen Bildungsbedingungen von Gashydraten in marinen Sedimenten unterscheiden sich von den Bedingungen in ausschliesslich wassergefuellten Systemen. Unter Einbeziehung petrographischer Eigenschaften werden die energetischen Bedingungen beschrieben. Dazu dient ein einfaches Kugelmodell. Je nach vorhandenem Porenraumspektrum, lithostatischen Spannungsverhaeltnissen, Porenwasserdruck und Sedimentfestigkeit wachsen Gashydrate als Porenraumzement oder als segregierte Linsen.

  3. Glacial magnetite dissolution in abyssal NW Pacific sediments - evidence for carbon trapping?

    Science.gov (United States)

    Korff, Lucia; von Dobeneck, Tilo; Frederichs, Thomas; Kasten, Sabine; Kuhn, Gerhard; Gersonde, Rainer; Diekmann, Bernhard

    2016-04-01

    The abyssal North Pacific Ocean's large volume, depth, and terminal position on the deep oceanic conveyor make it a candidate site for deep carbon trapping as postulated by climate theory to explain the massive glacial drawdown of atmospheric CO2. As the major basins of the North Pacific have depths of 5500-6500m, far below the modern and glacial Calcite Compensation Depths (CCD), these abyssal sediments are carbonate-free and therefore not suitable for carbonate-based paleoceanographic proxy reconstructions. Instead, paleo-, rock and environmental magnetic methods are generally well applicable to hololytic abyssal muds and clays. In 2009, the international paleoceanographic research cruise SO 202 INOPEX ('Innovative North Pacific Experiment') of the German RV SONNE collected two ocean-spanning EW sediment core transects of the North Pacific and Bering Sea recovering a total of 50 piston and gravity cores from 45 sites. Out of seven here considered abyssal Northwest Pacific piston cores collected at water depths of 5100 to 5700m with mostly coherent shipboard susceptibility logs, the 20.23m long SO202-39-3, retrieved from 5102 m water depth east of northern Shatsky Rise (38°00.70'N, 164°26.78'E), was rated as the stratigraphically most promising record of the entire core transect and selected for detailed paleo- and environmental magnetic, geochemical and sedimentological investigations. This core was dated by correlating its RPI and Ba/Ti records to well-dated reference records and obviously provides a continuous sequence of the past 940 kyrs. The most striking orck magnetic features are coherent magnetite-depleted zones corresponding to glacial periods. In the interglacial sections, detrital, volcanic and even submicron bacterial magnetite fractions are excellently preserved. These alternating magnetite preservation states seem to reflect dramatic oxygenation changes in the deep North Pacific Ocean and hint at large-scale benthic glacial carbon trapping

  4. Low level spectrometry of Fe-Mn concretions from the Pacific Ocean bed and of Pierre St. Martin cave sediments

    International Nuclear Information System (INIS)

    Dimchev, T.; Prodanov, Ya.

    1977-01-01

    Results of the nondestructive gamma-spectrometric analysis of the Fe-Mn nodules from the Pacific Ocean in the neighbourhood of the Raratonga Isles and Fiji Isles are reported. The cave sediments from the San Martin Cave in the Pyrenees and from other caves were also analyzed. The nondestructive method was used for analyzing samples using a low background scintillation gamma spectrometer. Results obtained for geological samples, soils, sediments, etc. are given for comparison. Statistical methods were applied for the quantitative analysis of the gamma spectra obtained. (author)

  5. Earth's portfolio of extreme sediment transport events

    Science.gov (United States)

    Korup, Oliver

    2012-05-01

    Quantitative estimates of sediment flux and the global cycling of sediments from hillslopes to rivers, estuaries, deltas, continental shelves, and deep-sea basins have a long research tradition. In this context, extremely large and commensurately rare sediment transport events have so far eluded a systematic analysis. To start filling this knowledge gap I review some of the highest reported sediment yields in mountain rivers impacted by volcanic eruptions, earthquake- and storm-triggered landslide episodes, and catastrophic dam breaks. Extreme specific yields, defined here as those exceeding the 95th percentile of compiled data, are ~ 104 t km- 2 yr- 1 if averaged over 1 yr. These extreme yields vary by eight orders of magnitude, but systematically decay with reference intervals from minutes to millennia such that yields vary by three orders of magnitude for a given reference interval. Sediment delivery from natural dam breaks and pyroclastic eruptions dominate these yields for a given reference interval. Even if averaged over 102-103 yr, the contribution of individual disturbances may remain elevated above corresponding catchment denudation rates. I further estimate rates of sediment (re-)mobilisation by individual giant terrestrial and submarine mass movements. Less than 50 postglacial submarine mass movements have involved an equivalent of ~ 10% of the contemporary annual global flux of fluvial sediment to Earth's oceans, while mobilisation rates by individual events rival the decadal-scale sediment discharge from tectonically active orogens such as Taiwan or New Zealand. Sediment flushing associated with catastrophic natural dam breaks is non-stationary and shows a distinct kink at the last glacial-interglacial transition, owing to the drainage of very large late Pleistocene ice-marginal lakes. Besides emphasising the contribution of high-magnitude and low-frequency events to the global sediment cascade, these findings stress the importance of sediment storage

  6. Indications of low macrobenthic activity in the deep sediments of the eastern Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Daniela Basso

    2004-12-01

    Full Text Available 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 has been evaluated and compared through 210Pb profiles from box-cores and study of dredge samples from sites on Medina Rise (1374 m water depth, the Messina Abyssal Plain (4135 m and several sites along the Mediterranean Ridge, SW and S of Crete (1783 to 3655 m. All these sites are remote from the continental shelves, so the biological benthic activity is expected to depend primarily on primary production from surface waters. The results show that present-day macrobenthos and trace fossils are generally scarce, especially at depths > 2500 m. This observation is supported by surface sediment 210Pb excess distributions that show a surface mixed layer (SML 2500 m. The historical layer of some box-cores and the Pleistocene hardgrounds collected in the Cleft area (Mediterranean Ridge do, however, record a macrobenthic activity that is apparently more intense than at present, which may be related to higher primary production of the Pleistocene glacial intervals. In contrast with most areas of the present-day deep eastern Mediterranean which depend on surface primary production based on photosynthesis, a relatively dense and diversified macrobenthic community based on chemosynthesis has been recognised at depths > 1100 m on the Napoli Dome mud volcano in the Olimpi area, and on the Kazan and other mud volcanoes in the Anaximander Mountains.

  7. Biogeochemical Regeneration of a Nodule Mining Disturbance Site: Trace Metals, DOC and Amino Acids in Deep-Sea Sediments and Pore Waters

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    Sophie A. L. Paul

    2018-04-01

    Full Text Available Increasing interest in deep-sea mineral resources, such as polymetallic nodules, calls for environmental research about possible impacts of mineral exploitation on the deep-sea ecosystem. So far, little geochemical comparisons of deep-sea sediments before and after mining induced disturbances have been made, and thus long-term environmental effects of deep-sea mining are unknown. Here we present geochemical data from sediment cores from an experimental disturbance area at 4,100 m water depth in the Peru Basin. The site was revisited in 2015, 26 years after a disturbance experiment mimicking nodule mining was carried out and compared to sites outside the experimental zone which served as a pre-disturbance reference. We investigated if signs of the disturbance are still visible in the solid phase and the pore water after 26 years or if pre-disturbance conditions have been re-established. Additionally, a new disturbance was created during the cruise and sampled 5 weeks later to compare short- and longer-term impacts. The particulate fraction and pore water were analyzed for major and trace elements to study element distribution and processes in the surface sediment. Pore water and bottom water samples were also analyzed for oxygen, nitrate, dissolved organic carbon, and dissolved amino acids, to examine organic matter degradation processes. The study area of about 11 km2 was found to be naturally more heterogeneous than expected, requiring an analysis of spatial variability before the disturbed and undisturbed sites can be compared. The disturbed sites exhibit various disturbance features: some surface sediments were mixed through, others had the top layer removed and some had additional material deposited on top. Pore water constituents have largely regained pre-disturbance gradients after 26 years. The solid phase, however, shows clear differences between disturbed and undisturbed sites in the top 20 cm so that the impact is still visible in the

  8. {sup 210}Pb-Excess and Sediment Accumulation Rates at the Iberian Continental Margin

    Energy Technology Data Exchange (ETDEWEB)

    Carvalho, F. P.; Oliveira, J. M.; Soares, A. M. [Nuclear and Technological Institute, Sacavem (Portugal)

    2013-07-15

    Sediments from the continental shelf, slope, and rise at the continental margin of northern Portugal and the adjacent Iberian abyssal basin were analysed for 210Pb, {sup 226}Ra, {sup 137}Cs and {sup 14}C. Pb-210 derived sedimentation rates at the continental shelf off the Portuguese coast were 0.2-0.6 cm/a. In some cores from fine sediment deposits at the outer shelf, the {sup 210}Pb excess continuum was interrupted and sediment layers were missing, suggesting that events such as sediment slides could have occurred. Higher sedimentation rates were determined in locations at the rise of the continental slope, confirming enhanced deposition by sediment slides. In the deeper Iberian Abyssal Basin, using the {sup 14}C age of sediment layers the sedimentation rate was determined at 3.2 cm/ka, thus four orders of magnitude lower than at the continental shelf. The spatial distribution of sedimentation rates determined by radionuclide based chronologies, suggested that fine sediments from river discharges are deposited mainly at the outer continental shelf. These deposits may became unstable with time and, occasionally, originate sediment slides that are drained by the canyons and reach the deep sea. The Iberian abyssal basin receives some advective contribution of these sediment slides and the sedimentation rate is one order of magnitude higher than in other abyssal basins of the NE Atlantic Ocean. (author)

  9. Bioproductivity in the Southern Ocean since the last Interglacial - new high-resolution biogenic opal flux records from the Scotia Sea

    Science.gov (United States)

    Sprenk, D.; Weber, M. E.; Kuhn, G.; Rosén, P.; Röhling, H.-G.

    2012-04-01

    The Southern Ocean plays an important role in transferring CO2 via wind-induced upwelling from the deep sea to the atmosphere. It is therefore one of the key areas to study climate change. Bioproductivity in the Southern Ocean is mostly influenced by the extent of sea ice, upwelling of cold nutrient- and silica-rich water, and the availability of light. Biogenic opal (BSi) is a significant nutrient in the Southern Ocean, and according to recent investigations only marginally affected by preservation changes. It can therefore be used as bioproductivity proxy. Here we present several methods to determine BSi, discuss them and put the results into context with respect to regional bioproductivity changes in Southern Ocean during the last glacial cycle. We studied deep-sea sediment core sites MD07-3133 and MD07-3134 from the central Scotia Sea with extraordinary high sedimentation rates of up to 2.1 to 1.2 m/kyr, respectively covering the last 92.5 kyr. BSi leaching according to Müller & Schneider (1993) is very time-consuming and expensive, so we measured only 253 samples from large-amplitude variation core sections. In addition, we determined BSi using non-destructive measurements of sediment colour b*, wet-bulk density, and Ti/Si count ratios. Furthermore, we provide the first attempts to estimate BSi in marine sediment using Fourier transform infrared spectroscopy (FTIRS), a cost-efficient method, which requires only 11 mg of sediment. All estimation methods capture the main BSi trends, however FTIRS seems to be the most promising one. In the central Scotia Sea, south of the modern Antarctic Polar Front, the BSi flux reflects a relatively complicated glacial-to-interglacial pattern with large-amplitude, millennial-scale fluctuations in bioproductivity. During Antarctic Isotopic Maxima, BSi fluxes were generally increased. Lowest bioproductivity occur at the Last Glacial Maximum, while upwelling of mid-depth water was reduced, atmospheric CO2 low, and sea-ice cover

  10. Glacial-interglacial variability in ocean oxygen and phosphorus in a global biogeochemical model

    Directory of Open Access Journals (Sweden)

    V Palastanga

    2013-02-01

    Full Text Available Increased transfer of particulate matter from continental shelves to the open ocean during glacials may have had a major impact on the biogeochemistry of the ocean. Here, we assess the response of the coupled oceanic cycles of oxygen, carbon, phosphorus, and iron to the input of particulate organic carbon and reactive phosphorus from shelves. We use a biogeochemical ocean model and specifically focus on the Last Glacial Maximum (LGM. When compared to an interglacial reference run, our glacial scenario with shelf input shows major increases in ocean productivity and phosphorus burial, while mean deep-water oxygen concentrations decline. There is a downward expansion of the oxygen minimum zones (OMZs in the Atlantic and Indian Ocean, while the extension of the OMZ in the Pacific is slightly reduced. Oxygen concentrations below 2000 m also decline but bottom waters do not become anoxic. The model simulations show when shelf input of particulate organic matter and particulate reactive P is considered, low oxygen areas in the glacial ocean expand, but concentrations are not low enough to generate wide scale changes in sediment biogeochemistry and sedimentary phosphorus recycling. Increased reactive phosphorus burial in the open ocean during the LGM in the model is related to dust input, notably over the southwest Atlantic and northwest Pacific, whereas input of material from shelves explains higher burial fluxes in continental slope and rise regions. Our model results are in qualitative agreement with available data and reproduce the strong spatial differences in the response of phosphorus burial to glacial-interglacial change. Our model results also highlight the need for additional sediment core records from all ocean basins to allow further insight into changes in phosphorus, carbon and oxygen dynamics in the ocean on glacial-interglacial timescales.

  11. The deep biosphere in terrestrial sediments in the Chesapeake Bay area, Virginia, USA

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    Anja eBreuker

    2011-07-01

    Full Text Available For the first time quantitative data on the abundance of Bacteria, Archaea and Eukarya in deep terrestrial sediments are provided using multiple methods (total cell counting, quantitative real-time PCR (Q-PCR and catalyzed reporter deposition – fluorescence in situ hybridization (CARD-FISH. The oligotrophic (organic carbon content of ~ 0.2 % deep terrestrial sediments in the Chesapeake Bay area at Eyreville, Virginia, USA, were drilled and sampled up to a depth of 140 m in 2006. The possibility of contamination during drilling was checked using fluorescent microspheres. Total cell counts decreased from 109 to 106 cells per g dry weight (dw within the uppermost 20 m depth, and did not further decrease with depth below. A significant proportion of the total cell counts could be detected with CARD-FISH within the uppermost 7 m depth. The CARD-FISH numbers for Bacteria were about an order of magnitude higher than those for Archaea. The dominance of Bacteria over Archaea was confirmed by Q-PCR. The down core quantitative distribution of prokaryotic and eukaryotic small subunit ribosomal RNA genes as well as functional genes involved in different biogeochemical processes was revealed by Q-PCR for the uppermost 10 m and for 80-140 m depth. Eukarya and the Fe(III- and Mn(IV-reducing bacterial group Geobacteriaceae were almost only found in the uppermost meter (arable soil, where reactive iron was detected in higher amounts. The bacterial candidate division JS-1 and the classes Anaerolineae and Caldilineae of the phylum Chloroflexi, highly abundant in marine sediments, were found up to the maximum sampling depth in high copy numbers at this terrestrial site as well. A similar high abundance of the functional gene cbbL encoding for the large subunit of RubisCO suggests that autotrophic microorganisms could be relevant in addition to heterotrophs. The functional gene aprA of sulfate reducing bacteria was found within distinct layers up to ca. 100 m depth

  12. Evolution of organic carbon burial in the Global Ocean during the Neogene

    Science.gov (United States)

    LI, Z.; Zhang, Y.

    2017-12-01

    Although only a small fraction of the organic carbon (OC) that rains from surface waters is eventually buried in the sediments, it is a process that controls the organic sub-cycle of the long-term carbon cycle, and the key for atmospheric O2, CO2 and nutrient cycling. Here we constrain the spatiotemporal variability of OC burial by quantifying the total organic carbon (TOC) mass accumulation rate (MAR) over the Neogene (23.0-2.6 Ma) by compiling the TOC, age model and sediment density data from sites retrieved by the Deep Sea Drilling Program, Ocean Drilling Program, and Integrated Ocean Drilling Program. We screened all available sites which yielded 80 sites with adequate data quality, covering all major ocean basins and sedimentary depositional environments. All age models are updated to the GTS 2012 timescale so the TOC MAR records from different sites are comparable. Preliminary results show a clear early Miocene peak of OC burial in many sites related to high sediment flux which might reflect the orogenic uplift and/or glacier erosion. Places that receive high influx of terrigenous inputs become "hotspots" for Neogene burial of OC. At "open ocean" sites, OC burial seems to be more impacted by marine productivity changes, with a pronounced increase during the middle Miocene "Monterey Formation" and late Miocene - early Pliocene "Biogenic Bloom". Upon the completion of the data collection, we will further explore the regional and global OC burial in the context of tectonic uplift, climate change and the evolution of primary producers and consumers during the last 23 million years of Earth history.

  13. Assessment of 210Po in agricultural soils and marine sediments of the Atlantic and Pacific oceans of Guatemala

    International Nuclear Information System (INIS)

    Garcia Vela, A.G.

    1999-01-01

    A radiochemical method consisting of 210 Polonium extraction was made to measure radioactivity in samples of soil and marine sediments of Atlantic and Pacific Ocean. The solution of polonium it was treated to obtain the deposition of the metal over a zinc disc and was measured by alpha espectrometry system based on Planar Ion Planted Silice (PIPS) system. The concern about cultivated soils its consuption products from sea and soil come from these sources. The results shows that activity of 210 Polonium in agricultural soils and marine sediments are below of ALI recommended by international standards

  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. Basalt microlapilli in deep sea sediments of Indian Ocean in the vicinity of Vityaz fracture zone

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B.N.; Iyer, S.D.

    Two cores recovered from the flanks of Mid-India oceanic ridge in the vicinity of Vityaz fracture zone consist of discrete pyroclastic layers at various depths. These layers are composed of coarse-grained, angular basaltic microlapilli in which...

  16. Hess Deep Interactive Lab: Exploring the Structure and Formation of the Oceanic Crust through Hands-On Models and Online Tools

    Science.gov (United States)

    Kurtz, N.; Marks, N.; Cooper, S. K.

    2014-12-01

    Scientific ocean drilling through the International Ocean Discovery Program (IODP) has contributed extensively to our knowledge of Earth systems science. However, many of its methods and discoveries can seem abstract and complicated for students. Collaborations between scientists and educators/artists to create accurate yet engaging demonstrations and activities have been crucial to increasing understanding and stimulating interest in fascinating geological topics. One such collaboration, which came out of Expedition 345 to the Hess Deep Rift, resulted in an interactive lab to explore sampling rocks from the usually inacessible lower oceanic crust, offering an insight into the geological processes that form the structure of the Earth's crust. This Hess Deep Interactive Lab aims to explain several significant discoveries made by oceanic drilling utilizing images of actual thin sections and core samples recovered from IODP expeditions. . Participants can interact with a physical model to learn about the coring and drilling processes, and gain an understanding of seafloor structures. The collaboration of this lab developed as a need to explain fundamental notions of the ocean crust formed at fast-spreading ridges. A complementary interactive online lab can be accessed at www.joidesresolution.org for students to engage further with these concepts. This project explores the relationship between physical and on-line models to further understanding, including what we can learn from the pros and cons of each.

  17. Biodiversity's big wet secret: the global distribution of marine biological records reveals chronic under-exploration of the deep pelagic ocean.

    Directory of Open Access Journals (Sweden)

    Thomas J Webb

    Full Text Available BACKGROUND: Understanding the distribution of marine biodiversity is a crucial first step towards the effective and sustainable management of marine ecosystems. Recent efforts to collate location records from marine surveys enable us to assemble a global picture of recorded marine biodiversity. They also effectively highlight gaps in our knowledge of particular marine regions. In particular, the deep pelagic ocean--the largest biome on Earth--is chronically under-represented in global databases of marine biodiversity. METHODOLOGY/PRINCIPAL FINDINGS: We use data from the Ocean Biogeographic Information System to plot the position in the water column of ca 7 million records of marine species occurrences. Records from relatively shallow waters dominate this global picture of recorded marine biodiversity. In addition, standardising the number of records from regions of the ocean differing in depth reveals that regardless of ocean depth, most records come either from surface waters or the sea bed. Midwater biodiversity is drastically under-represented. CONCLUSIONS/SIGNIFICANCE: The deep pelagic ocean is the largest habitat by volume on Earth, yet it remains biodiversity's big wet secret, as it is hugely under-represented in global databases of marine biological records. Given both its value in the provision of a range of ecosystem services, and its vulnerability to threats including overfishing and climate change, there is a pressing need to increase our knowledge of Earth's largest ecosystem.

  18. Chemical compositions of magnetic, stony spherules from deep-sea sediments determined by instrumental neutron activation analysis

    International Nuclear Information System (INIS)

    Yamakoshi, Kazuo

    1984-01-01

    Chemical compositions of magnetic, stony spherules from deep sea sediments were determined by instrumental neutron activation analysis. High Ir, Au, Ni and Co contents indicate their extraterrestrial origin. The obtained compositions are considerably different from those of chondrites. It can be qualitatively interpreted, however, that cosmic matters having the compositions of chondrites are changed into magnetic, stony spherules by thermal degenerations during their atmospheric entry. (author)

  19. Impact of an asteroid or comet in the ocean and extinction of terrestrial life

    International Nuclear Information System (INIS)

    Ahrens, T.J.; O'Keefe, J.D.

    1983-01-01

    Finite difference calculations describing the impact mechanics associated with a 10 to 30 km diameter silicate or water object impacting a 5 km deep ocean overlying a silicate solid planet at 30 km/sec demonstrate that from 12 to 15% of the bolide energy resides in the water. In the gravity field of the earth some 10 to 30 times the impactor mass of water is launched on trajectories which would take it to altitudes of 10 km or higher. This ejecta launched on trajectories which can achieve stratospheric heights is 10 1 to 10 2 projectile masses, similar to that resulting from impact of objects on an ocean-free silicate half-space (continent). Ejecta composed of impactor material, launched on trajectories which would carry it to stratospheric heights, matches the fraction (10 -2 to 10 -1 ) of bolide (extraterrestrial) material found in the platinum-metal-rich Cretaceous-Tertiary and Eocene-Oligocene boundary layers. Oceanic impact results in giant tsunamis initially having amplitudes of approx. 4 km, representing the solitary waterwave stability limit in the deep ocean, and containing 10 -2 to 10 -1 of the energy of the impact. Using the constraint of no observed turbidities in marine sediments in the Cretaceous-Tertiary and Eocene-Oligocene boundary materials (calculated maximum water-sediment interface particle velocity approx. 10 0 m/sec) implies a maximum impactor energy of approx. 10 28 to approx. 10 29 erg corresponding to a maximum diameter for a silicate impactor of approx. 2 km (at 11 km/sec). Minimal global tsunami run-up heights on the continents corresponding to impacts of this energy are 300-400 m. We speculate that such waves would inundate all low altitude continental areas. As a result, the terrestrial animal food chain would be seriously perturbed, which could have caused extinction of large terrestrial animals

  20. New Experimental Constraints on Crystallization Differentiation in a Deep Magma Ocean

    Science.gov (United States)

    Walter, M. J.; Ito, E.; Nakamura, E.; Tronnes, R.; Frost, D.

    2001-12-01

    Most of Earth's mass probably accreted as a consequence of numerous impacts between large bodies and proto-Earth, and a giant impact with a Mars-sized object is the most plausible explanation for a Moon forming event. 1 Physical models show that large impacts would have caused high-degrees of melting and a global magma ocean. 2 Crystallization differentiation in a deep magma ocean could impart stratification in the solidified mantle, forming large geochemical domains. To accurately model crystallization in a deep magma ocean the liquidus phase-relations of peridotite, as well as mineral/melt element partitioning, must be known at lower mantle conditions. Here, we report the results of liquidus experiments on fertile model peridotite compositions at 23 - 33 GPa. Experiments were performed in 6/8-type multi-anvil apparatus using carbide and sintered-diamond second-stage anvils with 4 and 2 mm truncations, respectively. Samples were encapsulated by either graphite or Re. High-temperatures were generated using LaCrO3 or Re furnaces, and temperatures were held from 2 to 50 minutes at 2300 - 2500 C. Run products were analyzed for major and trace elements using EPMA and SIMS. At 23 GPa the liquidus phase is majorite, followed closely down temperature by ferropericlase (Fp) and Mg-perovskite (Mg-Pv). At 24 GPa the liquidus phase has changed to Fp, followed closely by majorite and Mg-Pv. Ca-perovskite (Ca-Pv) is present only at much lower temperatures close to the solidus. At approximately 31 GPa Mg-Pv is the liquidus phase followed down-temperature by Fp then Ca-Pv. At ~ 33 GPa Ca-Pv crystallizes closer to the liquidus, within about 50 C, at a similar temperature to Fp. Thus, important phases crystallizing in a deep magma ocean are Mg-Pv, Ca-Pv and Fp. Crystallization models based on major element partitioning show that only very modest amounts of crystal separation of a Mg-Pv + Fp assemblage can be tolerated before Ca/Al, Al/Ti and Ca/Ti ratios become unrealistic for