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Sample records for affect biogeochemical cycles

  1. Biogeochemical Cycles in Degraded Lands

    NASA Technical Reports Server (NTRS)

    Davidson, Eric A.; Vieira, Ima Celia G.; ReisdeCarvalho, Claudio Jose; DeaneDeAbreuSa, Tatiana; deSpozaMoutinho, Paulo R.; Figueiredo, Ricardo O.; Stone, Thomas A.

    2003-01-01

    The objectives of this project were to define and describe the types of landscapes that fall under the broad category of "degraded lands" and to study biogeochemical cycles across this range of degradation found in secondary forests. We define degraded land as that which has lost part of its capacity of renovation of a productive ecosystem, either in the context of agroecosystems or as native communities of vegetation. This definition of degradation permits evaluation of biogeochemical constraints to future land uses.

  2. Biogeochemical Cycles in Degraded Lands

    NASA Technical Reports Server (NTRS)

    Davidson, Eric A.; Vieira, Ima Celia G.; ReisdeCarvalho, Claudio Jose; DeanedeAbreuSa, Tatiana; deSouzaMoutinho, Paulo R.; Figueiredo, Ricardo O.; Stone, Thomas A.

    2004-01-01

    The objectives of this project were to define and describe the types of landscapes that fall under the broad category of "degraded lands" and to study biogeochemical cycles across this range of degradation found in secondary forests. We define degraded land as that which has lost part of its capacity of renovation of a productive ecosystem, either in the context of agroecosystems or as native communities of vegetation. This definition of degradation permits evaluation of biogeochemical constraints to future land uses.

  3. Biogeochemical cycling and remote sensing

    NASA Technical Reports Server (NTRS)

    Peterson, D. L.

    1985-01-01

    Research is underway at the NASA Ames Research Center that is concerned with aspects of the nitrogen cycle in terrestrial ecosystems. An interdisciplinary research group is attempting to correlate nitrogen transformations, processes, and productivity with variables that can be remotely sensed. Recent NASA and other publications concerning biogeochemical cycling at global scales identify attributes of vegetation that could be related or explain the spatial variation in biologically functional variables. These functional variables include net primary productivity, annual nitrogen mineralization, and possibly the emission rate of nitrous oxide from soils.

  4. Biogeochemical Cycles of Carbon and Sulfur

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    The elements carbon (C) and sulfur (S) interact with each other across a network of elemental reservoirs that are interconnected by an array of physical, chemical and biological processes. These networks are termed the biogeochemical C and S cycles. The compounds of C are highly important, not only as organic matter, but also as atmospheric greenhouse gases, pH buffers in seawater, oxidation-reduction buffers virtually everywhere, and key magmatic constituents affecting plutonism and volcanism. The element S assumes important roles as an oxidation-reduction partner with C and Fe in biological systems, as a key constituent in magmas and volcanic gases, and as a major influence upon pH in certain environments. This presentation describes the modern biogeochemical C and S cycles. Measurements are described whereby stable isotopes can help to infer the nature and quantitative significance of biological and geological processes involved in the C and S cycles. This lecture also summarizes the geological and climatologic aspects of the ancient C and S cycles, as well as the planetary and extraterrestrial processes that influenced their evolution over millions to billions of years.

  5. Redox regime shifts in microbially mediated biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Bush, T.; Butler, I. B.; Free, A.; Allen, R. J.

    2015-06-01

    Understanding how the Earth's biogeochemical cycles respond to environmental change is a prerequisite for the prediction and mitigation of the effects of anthropogenic perturbations. Microbial populations mediate key steps in these cycles, yet they are often crudely represented in biogeochemical models. Here, we show that microbial population dynamics can qualitatively affect the response of biogeochemical cycles to environmental change. Using simple and generic mathematical models, we find that nutrient limitations on microbial population growth can lead to regime shifts, in which the redox state of a biogeochemical cycle changes dramatically as the availability of a redox-controlling species, such as oxygen or acetate, crosses a threshold (a "tipping point"). These redox regime shifts occur in parameter ranges that are relevant to the present-day sulfur cycle in the natural environment and the present-day nitrogen cycle in eutrophic terrestrial environments. These shifts may also have relevance to iron cycling in the iron-containing Proterozoic and Archean oceans. We show that redox regime shifts also occur in models with physically realistic modifications, such as additional terms, chemical states, or microbial populations. Our work reveals a possible new mechanism by which regime shifts can occur in nutrient-cycling ecosystems and biogeochemical cycles, and highlights the importance of considering microbial population dynamics in models of biogeochemical cycles.

  6. Searching for Biogeochemical Cycles on Mars

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.

    1997-01-01

    The search for life on Mars clearly benefits from a rigorous, yet broad, definition of life that compels us to consider all possible lines of evidence for a martian biosphere. Recent studies in microbial ecology illustrate that the classic definition of life should be expanded beyond the traditional definition of a living cell. The traditional defining characteristics of life are threefold. First, life is capable of metabolism, that is, it performs chemical reactions that utilize energy and also synthesize its cellular constituents. Second, life is capable of self-replication. Third, life can evolve in order to adapt to environmental changes. An expanded, ecological definition of life also recognizes that life is a community of organisms that must interact with their nonliving environment through processes called biogeochemical cycles. This regenerative processing maintains, in an aqueous conditions, a dependable supply of nutrients and energy for growth. In turn, life can significantly affect those processes that control the exchange of materials between the atmosphere, ocean, and upper crust. Because metabolic processes interact directly with the environment, they can alter their surroundings and thus leave behind evidence of life. For example, organic matter is produced from single-carbon-atom precursors for the biosynthesis of cellular constituents. This leads to a reservoir of reduced carbon in sediments that, in turn, can affect the oxidation state of the atmosphere. The harvesting of chemical energy for metabolism often employs oxidation-reduction reactions that can alter the chemistry and oxidation state of the redox-sensitive elements carbon, sulfur, nitrogen, iron, and manganese. Have there ever been biogeochemical cycles on Mars? Certain key planetary processes can offer clues. Active volcanism provides reduced chemical species that biota can use for organic synthesis. Volcanic carbon dioxide and methane can serve as greenhouse gases. Thus the

  7. Managing biogeochemical cycles to reduce greenhouse gases

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This special issue focuses on terrestrial biogeochemical cycles and their roles in determining current continental-scale budgets and future trends in biogenic greenhouse gases (GHGs) for North America. Understanding the current magnitude and forecasting future trajectories of atmospheric GHG concent...

  8. Managing biogeochemical cycles to reduce greenhouse gases

    SciTech Connect

    Post, Wilfred M; Venterea, Rodney

    2012-01-01

    This special issue focuses on terrestrial biogeochemical cycles as they relate to North America-wide budgeting and future projection of biogenic greenhouse gases (GHGs). Understanding the current magnitude and providing guidance on the future trajectories of atmospheric concentrations of these gases requires investigation of their (i) biogeochemical origins, (ii) response to climate feedbacks and other environmental factors, and (iii) susceptibility to management practices. This special issue provides a group of articles that present the current state of continental scale sources and sinks of biogenic GHGs and the potential to better manage them in the future.

  9. EFFECTS OF INCREASED SOLAR ULTRAVIOLET RADIATION ON BIOGEOCHEMICAL CYCLES

    EPA Science Inventory

    Increases in solar UV radiation could affect terrestrial and aquatic biogeochemical cycles thus altering both sources and sinks of greenhouse and chemically important trace gases (e.g., carbon dioxide (CO2), carbon monoxide (CO), carbonyl sulfide (COS)). n terrestrial ecosystems,...

  10. Estimating impacts of lichens and bryophytes on global biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Porada, Philipp; Weber, Bettina; Elbert, Wolfgang; Pöschl, Ulrich; Kleidon, Axel

    2014-02-01

    Lichens and bryophytes may significantly affect global biogeochemical cycles by fixation of nitrogen and biotic enhancement of surface weathering rates. Most of the studies suggesting these effects, however, are either conceptual or rely on upscaling of regional estimates to obtain global numbers. Here we use a different method, based on estimates of net carbon uptake, to quantify the impacts of lichens and bryophytes on biogeochemical cycles at the global scale. We focus on three processes, namely, nitrogen fixation, phosphorus uptake, and chemical weathering. Our estimates have the form of potential rates, which means that we quantify the amount of nitrogen and phosphorus needed by the organisms to build up biomass, also accounting for resorption and leaching of nutrients. Subsequently, we use potential phosphorus uptake on bare ground to estimate chemical weathering by the organisms, assuming that they release weathering agents to obtain phosphorus. The predicted requirement for nitrogen ranges from 3.5 to 34 Tgyr-1 and for phosphorus it ranges from 0.46 to 4.6 Tgyr-1. Estimates of chemical weathering are between 0.058 and 1.1 km3 yr-1 of rock. These values seem to have a realistic order of magnitude, and they support the notion that lichens and bryophytes have the potential to play an important role for biogeochemical cycles.

  11. Redox chemistry in the phosphorus biogeochemical cycle

    NASA Astrophysics Data System (ADS)

    Pasek, Matthew A.; Sampson, Jacqueline M.; Atlas, Zachary

    2014-10-01

    The element phosphorus (P) controls growth in many ecosystems as the limiting nutrient, where it is broadly considered to reside as pentavalent P in phosphate minerals and organic esters. Exceptions to pentavalent P include phosphine-PH3-a trace atmospheric gas, and phosphite and hypophosphite, P anions that have been detected recently in lightning strikes, eutrophic lakes, geothermal springs, and termite hindguts. Reduced oxidation state P compounds include the phosphonates, characterized by C-P bonds, which bear up to 25% of total organic dissolved phosphorus. Reduced P compounds have been considered to be rare; however, the microbial ability to use reduced P compounds as sole P sources is ubiquitous. Here we show that between 10% and 20% of dissolved P bears a redox state of less than +5 in water samples from central Florida, on average, with some samples bearing almost as much reduced P as phosphate. If the quantity of reduced P observed in the water samples from Florida studied here is broadly characteristic of similar environments on the global scale, it accounts well for the concentration of atmospheric phosphine and provides a rationale for the ubiquity of phosphite utilization genes in nature. Phosphine is generated at a quantity consistent with thermodynamic equilibrium established by the disproportionation reaction of reduced P species. Comprising 10-20% of the total dissolved P inventory in Florida environments, reduced P compounds could hence be a critical part of the phosphorus biogeochemical cycle, and in turn may impact global carbon cycling and methanogenesis.

  12. Redox chemistry in the phosphorus biogeochemical cycle

    PubMed Central

    Pasek, Matthew A.; Sampson, Jacqueline M.; Atlas, Zachary

    2014-01-01

    The element phosphorus (P) controls growth in many ecosystems as the limiting nutrient, where it is broadly considered to reside as pentavalent P in phosphate minerals and organic esters. Exceptions to pentavalent P include phosphine—PH3—a trace atmospheric gas, and phosphite and hypophosphite, P anions that have been detected recently in lightning strikes, eutrophic lakes, geothermal springs, and termite hindguts. Reduced oxidation state P compounds include the phosphonates, characterized by C−P bonds, which bear up to 25% of total organic dissolved phosphorus. Reduced P compounds have been considered to be rare; however, the microbial ability to use reduced P compounds as sole P sources is ubiquitous. Here we show that between 10% and 20% of dissolved P bears a redox state of less than +5 in water samples from central Florida, on average, with some samples bearing almost as much reduced P as phosphate. If the quantity of reduced P observed in the water samples from Florida studied here is broadly characteristic of similar environments on the global scale, it accounts well for the concentration of atmospheric phosphine and provides a rationale for the ubiquity of phosphite utilization genes in nature. Phosphine is generated at a quantity consistent with thermodynamic equilibrium established by the disproportionation reaction of reduced P species. Comprising 10–20% of the total dissolved P inventory in Florida environments, reduced P compounds could hence be a critical part of the phosphorus biogeochemical cycle, and in turn may impact global carbon cycling and methanogenesis. PMID:25313061

  13. Terrestrial ecosystems and the global biogeochemical silica cycle

    NASA Astrophysics Data System (ADS)

    Conley, Daniel J.

    2002-12-01

    Most research on the global Si cycle has focused nearly exclusively on weathering or the oceanic Si cycle and has not explored the complexity of the terrestrial biogeochemical cycle. The global biogeochemical Si cycle is of great interest because of its impact on global CO2 concentrations through the combined processes of weathering of silicate minerals and transfer of CO2 from the atmosphere to the lithosphere. A sizable pool of Si is contained as accumulations of amorphous silica, or biogenic silica (BSi), in living tissues of growing plants, known as phytoliths, and, after decomposition of organic material, as remains in the soil. The annual fixation of phytolith silica ranges from 60-200 Tmol yr-1 and rivals that fixed in the oceanic biogeochemical cycle (240 Tmol yr-1). Internal recycling of the phytolith pool is intense with riverine fluxes of dissolved silicate to the oceans buffered by the terrestrial biogeochemical Si cycle, challenging the ability of weathering models to predict rates of weathering and consequently, changes in global climate. Consideration must be given to the influence of the terrestrial BSi pool on variations in the global biogeochemical Si cycle over geologic time and the influence man has had on modifying both the terrestrial and aquatic biogeochemical cycles.

  14. The biogeochemical iron cycle and astrobiology

    NASA Astrophysics Data System (ADS)

    Schröder, Christian; Köhler, Inga; Muller, Francois L. L.; Chumakov, Aleksandr I.; Kupenko, Ilya; Rüffer, Rudolf; Kappler, Andreas

    2016-12-01

    Biogeochemistry investigates chemical cycles which influence or are influenced by biological activity. Astrobiology studies the origin, evolution and distribution of life in the universe. The biogeochemical Fe cycle has controlled major nutrient cycles such as the C cycle throughout geological time. Iron sulfide minerals may have provided energy and surfaces for the first pioneer organisms on Earth. Banded iron formations document the evolution of oxygenic photosynthesis. To assess the potential habitability of planets other than Earth one looks for water, an energy source and a C source. On Mars, for example, Fe minerals have provided evidence for the past presence of liquid water on its surface and would provide a viable energy source. Here we present Mössbauer spectroscopy investigations of Fe and C cycle interactions in both ancient and modern environments. Experiments to simulate the diagenesis of banded iron formations indicate that the formation of ferrous minerals depends on the amount of biomass buried with ferric precursors rather than on the atmospheric composition at the time of deposition. Mössbauer spectra further reveal the mutual stabilisation of Fe-organic matter complexes against mineral transformation and decay of organic matter into CO2. This corresponds to observations of a `rusty carbon sink' in modern sediments. The stabilisation of Fe-organic matter complexes may also aid transport of particulate Fe in the water column while having an adverse effect on the bioavailability of Fe. In the modern oxic ocean, Fe is insoluble and particulate Fe represents an important source. Collecting that particulate Fe yields small sample sizes that would pose a challenge for conventional Mössbauer experiments. We demonstrate that the unique properties of the beam used in synchrotron-based Mössbauer applications can be utilized for studying such samples effectively. Reactive Fe species often occur in amorphous or nanoparticulate form in the environment and

  15. Drought-induced Changes in Dryland Soil Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Belnap, J.; Darrouzet-Nardi, A.; Duniway, M.; Ferrenberg, S.; Hoover, D. L.; Reed, S.

    2015-12-01

    Approximately 41% of Earth´s terrestrial surface consists of drylands and they are an important biome on all continents. Although dryland biota would be expected to be drought adapted, they can be surprisingly vulnerable to extended dry periods with subsequent consequences for biogeochemical cycles. Biological soil crusts, constituting up to 70% of the living cover in these regions, are important in these cycles. They fix both N and C, providing a significant percentage of regional and global inputs. However, extended drought reduces both types of inputs, as biocrusts are only metabolically active when wet, yet losses continue even when soils are dry. In addition, extended droughts can result in their mortality. The amount of net soil C exchange of biocrusted soils is controversial, but in SE Utah, soil C uptake only occurred when only when soils were wet. As soils are infrequently wet, annual balances were negative during the 2 year study and with future extended droughts or increased temperatures that reduce soil moisture, these losses will become even greater. As with C, N fixation also requires biocrusts be wet and thus inputs decline with extended drought or higher temperatures that both reduce input and result in lichen and cyanobacterial mortality. And similarly, N losses continue even when soils are dry. Loss of biocrust mosses can profoundly alter N cycles. Desert plants are also affected by drought: in plots where experimental drought was imposed, plants had lower photosynthetic rates and higher leaf C:N, which will likely affect productivity and decomposition rates and thus have further impacts on soil biogeochemical cycles.

  16. Factors Influencing Phosphorous Cycling in Biogeochemical 'Hot Spots'

    NASA Astrophysics Data System (ADS)

    Saia, S. M.; Walter, M. T.; Buda, A. R.; Carrick, H. J.; Regan, J. M.

    2015-12-01

    Anthropogenic alteration of the phosphorus (P) cycle has led to subsequent soil and water quality issues. For example, P build up in soils due to historic fertilizer application may become biologically available and exacerbate eutrophication and anoxia in nearby water bodies. In the humid Northeastern United States, storm runoff transports P and also stimulates biogeochemical processes, these locations are termed biogeochemical 'hot spots'. Many studies have looked at nitrogen and carbon cycling in biogeochemical hot spots but few have focused on P. We hypothesize the periodic wetting and drying of biogeochemical hot spots promotes a combination of abiotic and biotic processes that influence the mobility of P. To test this hypothesis, we took monthly soil samples (5 cm deep) from May to October in forest, pasture, and cropped land near Ithaca, NY. In-situ measurements taken with each sample included volumetric soil moisture and soil temperature. We also analyzed samples for 'runoff generated' phosphate, nitrate, and sulfate (from 0.01 M CaCl2 extraction), Fe(II), percent organic matter, pH, as well as oxalate extractable and total P, Al, and Fe. We used linear mixed effects models to test how runoff generated phosphate concentrations vary with soil moisture and whether other environmental factors strengthen/weaken this relationship. The knowledge gained from this study will improve our understanding of P cycling in biogeochemical hot spots and can be used to improve the effectiveness of agricultural management practices in the Northeastern United States.

  17. Effects of Privately Owned Land Management Practices on Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    Getson, J. M.; Hutyra, L.; Short, A. G.; Templer, P. H.; Kittredge, D.

    2014-12-01

    An increasing fraction of the global population lives in urban settings. Understanding how the human-natural system couple and decouple biogeochemical cycles across urbanization gradients is crucial for human health and environmental sustainability. Natural processes of nutrient deposition, export, uptake, and internal cycling can be disrupted by human activities. Residential landscape management (e.g. composting, leaf litter collection, fertilizer application) interrupts these natural biogeochemical cycles; therefore, it is key to characterize these practices and their impacts. This study looks at private land management practices along a rural to urban gradient in Boston, Massachusetts. We used a mail survey instrument coupled with biogeochemical measurements and remote sensing derived estimates of aboveground biomass to estimate biogeochemical modifications associated with residential landscape management practices. We find parcel size influences management behavior, management practices differ for leaf litter and lawn clippings, and fertilizer application is unrelated to parcel size or degree of urban-ness. These management practices result in nutrient redistribution that differs with residential characteristics.

  18. Inland aquatic resources and biogeochemical cycles

    SciTech Connect

    Melack, J.M.

    1984-08-01

    The biosphere is the entire planetary system that includes, sustains and is influenced by life. The central issue of the science of the biosphere is the extent to which the Earth's surface, atmosphere and hydrosphere is the result of biological rather than abiotic processes. Space science and technology accelerates the understanding of global biological processes by providing repetive synoptic observations on large spatial scales once the relationships between the processes and the remotely sensed quantities are established. Especially promising applications of space technology are the measurement of biological productivity and portions of geochemical cycles in aquatic ecosystems and the evaluation and management of the quality of freshwater resources.

  19. Will a changed element composition of rainfall - due to climate change - affect the biogeochemical cycle of montane forest soils in Southern Ecuador?

    NASA Astrophysics Data System (ADS)

    Wullaert, H.; Peña, J. L.; González, E.; Valarezo, C.; Wilcke, W.

    2009-04-01

    Increasing biomass burning, fertilization and industrialization in tropical areas will generally lead to a greater N deposition in the Tropics including the northern Andean forests in the coming decades. In previous work, we detected extra Ca deposition from the atmosphere in the northern Andes originating from Sahara dust during a pronounced la Niña event. Therefore, the possible shortening of the El Niño Southern Oscillation might result in more frequent Ca input into the northern Andean forests. We quantify biogeochemical processes in a tropical montane forest in southern Ecuador at 2000 m a.s.l. in response to N and Ca additions to simulate elevated N and Ca deposition from the atmosphere. Four replicate experimental plots under native forest were fertilized with either 50 kg N or 10 kg Ca ha-1 y-1 with urea (46%) and CaCl2.2H2O, respectively, distributed between two dates per year and the effects were compared with non-fertilized control plots. We collected litter percolate with zero-tension lysimeters, soil solution with suction cups at 0.15 and 0.30 m, rainfall and throughfall. Samples were analyzed for concentrations of total N, nitrate, ammonium, dissolved organic nitrogen (DON) and Ca. Two months after the first fertilization, nitrogen addition mainly stimulates microbial activity where in a priming effect ammonium is transferred to nitrate and soil organic matter is mineralised, resulting in increased DON concentrations. This stimulation would also release other nutrients than N which in turn enhance tree growth. Total nitrogen concentration in litter leachate increased slightly after N fertilization from 1.75 mg/l to 1.8 mg/l, which represents about 1.5% of the total applied N. In contrast, the low Ca concentrations in litter leachate doubled from 0.10 mg/l to 0.20 mg/l after Ca addition, which on yearly basis would represent about 15% of the total applied Ca. From these preliminary results we conclude that (i) both added N and Ca are net retained in

  20. Eddy Permitting Simulations of Biogeochemical Cycles in the Global Ocean

    NASA Astrophysics Data System (ADS)

    Sumata, H.; Hashioka, T.; Suzuki, T.; Yamanaka, Y.

    2008-12-01

    A 3D ecosystem-biogeochemical model simulation for the global domain is performed in order to investigate variability of oceanic ecosystem on time scales of years to decades. The model has a horizontal resolution of 1/4 times 1/6 degrees and 51 vertical levels, covering the entire domain of the world ocean. The ecosystem- biogeochemical part of the model is based on NEMURO (North Pacific Ecosystem Model Used for Regional Oceanography), and is coupled with CCSR Ocean Component Model (COCO) version 4.3 by an offline technique. The physical part of the model is driven by the inter-annual forcing by common ocean-ice reference experiments (CORE) data from 1958 to 2004, and reasonably simulates inter-annual to decadal variabilities of ocean conditions related to biogeochemical cycles. These properties of the physical model with its eddying filed enable us to reproduce the realistic distributions of nutrients and plankton productions. Comparisons with historical station data show that the model also reasonably simulates the observed variabilities of ecosystem on time scales of years to decades. In particular, the model captures the transitions of biogeochemical cycles associated with regime shifts.

  1. Seasonal biogeochemical cycles in riverborne groundwater

    SciTech Connect

    Gunten, H.R. von; Karametaxas, G.; Kraehenbuehl, U.; Kuslys, M.; Giovanoli, R. ); Hoehn, E.; Keil, R. )

    1991-12-01

    The behavior of dissolved (<0.45{mu}m) inorganic species and changes in relevant properties of anthropogenically polluted river water were investigated during infiltration and movement in a hydraulically connected saturated aquifer. Water from the river and from several sampling wells was analyzed over 5 years for temporal and spatial chemical changes. At the early stage of infiltration, a drastic decrease in pH and in the concentrations of O{sub 2} and NO{sub 3}{sup {minus}} occurs. The gradients in these properties are most significant in the interstitial water of the river sediments. They are the result of the degradation of aquatic biota. The amount and grain morphology of river sediments varies seasonally and depends also on water flow conditions. Temperature-related variations in microbiological activity in the river water and in the sediments of the riverbed induce pronounced annual cycles in the aquifer for several of the investigated properties. Each summer, under anoxic conditions, manganese (hydr) oxides dissolve, and trace metals (Cu, Zn, Cd) are mobilized. The main sources for manganese and other trace elements were found within the river sediments; degradation of algae and other aquatic biota and dissolution of calcite contribute to the observed effects. Higher winter concentrations of O{sub 2} and NO{sub 3}{sup {minus}} result in precipitation of Mn and other redox sensitive elements in the aquifer. Zinc and Cd are retarded by interactions with the aquifer material, whereas Cu is mobile, probably as an organic complex.

  2. The microbial engines that drive Earth's biogeochemical cycles.

    PubMed

    Falkowski, Paul G; Fenchel, Tom; Delong, Edward F

    2008-05-23

    Virtually all nonequilibrium electron transfers on Earth are driven by a set of nanobiological machines composed largely of multimeric protein complexes associated with a small number of prosthetic groups. These machines evolved exclusively in microbes early in our planet's history yet, despite their antiquity, are highly conserved. Hence, although there is enormous genetic diversity in nature, there remains a relatively stable set of core genes coding for the major redox reactions essential for life and biogeochemical cycles. These genes created and coevolved with biogeochemical cycles and were passed from microbe to microbe primarily by horizontal gene transfer. A major challenge in the coming decades is to understand how these machines evolved, how they work, and the processes that control their activity on both molecular and planetary scales. PMID:18497287

  3. The global troposphere - Biogeochemical cycles, chemistry, and remote sensing

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Allario, F.

    1982-01-01

    The chemical composition of the troposphere is controlled by various biogeochemical cycles that couple the atmosphere with the oceans, the solid earth and the biosphere, and by atmospheric photochemical/chemical reactions. These cycles and reactions are discussed and a number of key questions concerning tropospheric composition and chemistry for the carbon, nitrogen, oxygen and sulfur species are identified. Next, various remote sensing techniques and instruments capable of measuring and monitoring tropospheric species from the ground, aircraft and space to address some of these key questions are reviewed. Future thrusts in remote sensing of the troposphere are also considered.

  4. The global troposphere: Biogeochemical cycles, chemistry, and remote sensing.

    PubMed

    Levine, J S; Allario, F

    1982-09-01

    The chemical composition of the troposphere is controlled by various biogeochemical cycles that couple the atmosphere with the oceans, the solid Earth and the biosphere, and by atmospheric photochemical/chemical reactions. These cycles and reactions are discussed and a number of key questions concerning tropospheric composition and chemistry for the carbon, nitrogen, oxygen and sulfur species are identified. Next, we review various remote sensing techniques and instruments capable of measuring and monitoring tropospheric species from the ground, aircraft and space to address some of these key questions. We also consider future thrusts in remote sensing of the troposphere. PMID:24264018

  5. Biogeochemical cycling of Si in a California rice cropping system

    NASA Astrophysics Data System (ADS)

    Seyfferth, A.; Kocar, B. D.; Lee, J.; Fendorf, S.

    2012-12-01

    Silicon is the second most abundant element in the earth's crust, but the number of studies on the biogeochemical cycling of Si does not reflect its environmental ubiquity. While not an "essential" plant nutrient, Si is important for many plants, particularly monocots, for structural integrity and protection against disease and environmental stress. For rice, Si fertilization with N and P increases yield significantly more than N and P alone. While total Si in soil is high, much of this Si is tied up in the crystal lattice of primary and secondary minerals and is only slowly released through chemical weathering. Thus, plant-available Si may be limited particularly in highly weathered soils in humid environments where long-term chemical weathering has lead to desilicification of the soils (e.g., in Southeast Asia where most rice is grown). In such Si-depleted environments, the biocycling of Si through decaying plant litter (i.e., phytoliths) and subsequent plant uptake has proven an important component of the terrestrial biogeochemical cycling of Si. Here, we investigate the dynamics of Si cycling over a two-year period in a rice paddy in Northern California where soil incorporation of harvested rice straw has impacted the terrestrial biogeochemical cycling of Si. We use Ge/Si ratios in pore-waters to infer the contribution of chemical weathering vs. dissolution of plant phytoliths on the plant-available Si pool. We found that the Ge/Si ratios change over the growing and fallow seasons reflecting different rates of Si release through phytolith dissolution and plant uptake.

  6. Water pulses and biogeochemical cycles in arid and semiarid ecosystems.

    PubMed

    Austin, Amy T; Yahdjian, Laura; Stark, John M; Belnap, Jayne; Porporato, Amilcare; Norton, Urszula; Ravetta, Damián A; Schaeffer, Sean M

    2004-10-01

    The episodic nature of water availability in arid and semiarid ecosystems has significant consequences on belowground carbon and nutrient cycling. Pulsed water events directly control belowground processes through soil wet-dry cycles. Rapid soil microbial response to incident moisture availability often results in almost instantaneous C and N mineralization, followed by shifts in C/N of microbially available substrate, and an offset in the balance between nutrient immobilization and mineralization. Nitrogen inputs from biological soil crusts are also highly sensitive to pulsed rain events, and nitrogen losses, particularly gaseous losses due to denitrification and nitrate leaching, are tightly linked to pulses of water availability. The magnitude of the effect of water pulses on carbon and nutrient pools, however, depends on the distribution of resource availability and soil organisms, both of which are strongly affected by the spatial and temporal heterogeneity of vegetation cover, topographic position and soil texture. The 'inverse texture hypothesis' for net primary production in water-limited ecosystems suggests that coarse-textured soils have higher NPP than fine-textured soils in very arid zones due to reduced evaporative losses, while NPP is greater in fine-textured soils in higher rainfall ecosystems due to increased water-holding capacity. With respect to belowground processes, fine-textured soils tend to have higher water-holding capacity and labile C and N pools than coarse-textured soils, and often show a much greater flush of N mineralization. The result of the interaction of texture and pulsed rainfall events suggests a corollary hypothesis for nutrient turnover in arid and semiarid ecosystems with a linear increase of N mineralization in coarse-textured soils, but a saturating response for fine-textured soils due to the importance of soil C and N pools. Seasonal distribution of water pulses can lead to the accumulation of mineral N in the dry season

  7. Biogeochemical cycling in terrestrial ecosystems of the Caatinga Biome.

    PubMed

    Menezes, R S C; Sampaio, E V S B; Giongo, V; Pérez-Marin, A M

    2012-08-01

    The biogeochemical cycles of C, N, P and water, the impacts of land use in the stocks and flows of these elements and how they can affect the structure and functioning of Caatinga were reviewed. About half of this biome is still covered by native secondary vegetation. Soils are deficient in nutrients, especially N and P. Average concentrations of total soil P and C in the top layer (0-20 cm) are 196 mg kg(-1) and 9.3 g kg(-1), corresponding to C stocks around 23 Mg ha(-1). Aboveground biomass of native vegetation varies from 30 to 50 Mg ha(-1), and average root biomass from 3 to 12 Mg ha(-1). Average annual productivities and biomass accumulation in different land use systems vary from 1 to 7 Mg ha(-1) year(-1). Biological atmospheric N2 fixation is estimated to vary from 3 to 11 kg N ha(-1) year-1 and 21 to 26 kg N ha(-1) year(-1) in mature and secondary Caatinga, respectively. The main processes responsible for nutrient and water losses are fire, soil erosion, runoff and harvest of crops and animal products. Projected climate changes in the future point to higher temperatures and rainfall decreases. In face of the high intrinsic variability, actions to increase sustainability should improve resilience and stability of the ecosystems. Land use systems based on perennial species, as opposed to annual species, may be more stable and resilient, thus more adequate to face future potential increases in climate variability. Long-term studies to investigate the potential of the native biodiversity or adapted exotic species to design sustainable land use systems should be encouraged. PMID:23011295

  8. Ocean fronts drive marine fishery production and biogeochemical cycling.

    PubMed

    Woodson, C Brock; Litvin, Steven Y

    2015-02-10

    Long-term changes in nutrient supply and primary production reportedly foreshadow substantial declines in global marine fishery production. These declines combined with current overfishing, habitat degradation, and pollution paint a grim picture for the future of marine fisheries and ecosystems. However, current models forecasting such declines do not account for the effects of ocean fronts as biogeochemical hotspots. Here we apply a fundamental technique from fluid dynamics to an ecosystem model to show how fronts increase total ecosystem biomass, explain fishery production, cause regime shifts, and contribute significantly to global biogeochemical budgets by channeling nutrients through alternate trophic pathways. We then illustrate how ocean fronts affect fishery abundance and yield, using long-term records of anchovy-sardine regimes and salmon abundances in the California Current. These results elucidate the fundamental importance of biophysical coupling as a driver of bottom-up vs. top-down regulation and high productivity in marine ecosystems. PMID:25624488

  9. Ocean fronts drive marine fishery production and biogeochemical cycling

    PubMed Central

    Woodson, C. Brock; Litvin, Steven Y.

    2015-01-01

    Long-term changes in nutrient supply and primary production reportedly foreshadow substantial declines in global marine fishery production. These declines combined with current overfishing, habitat degradation, and pollution paint a grim picture for the future of marine fisheries and ecosystems. However, current models forecasting such declines do not account for the effects of ocean fronts as biogeochemical hotspots. Here we apply a fundamental technique from fluid dynamics to an ecosystem model to show how fronts increase total ecosystem biomass, explain fishery production, cause regime shifts, and contribute significantly to global biogeochemical budgets by channeling nutrients through alternate trophic pathways. We then illustrate how ocean fronts affect fishery abundance and yield, using long-term records of anchovy–sardine regimes and salmon abundances in the California Current. These results elucidate the fundamental importance of biophysical coupling as a driver of bottom–up vs. top–down regulation and high productivity in marine ecosystems. PMID:25624488

  10. Mangrove forests: a potent nexus of coastal biogeochemical cycling

    NASA Astrophysics Data System (ADS)

    Barr, J. G.; Fuentes, J. D.; Shoemaker, B.; O'Halloran, T. L.; Lin, G., Sr.; Engel, V. C.

    2014-12-01

    Mangrove forests cover just 0.1% of the Earth's terrestrial surface, yet they provide a disproportionate source (~10 % globally) of terrestrially derived, refractory dissolved organic carbon to the oceans. Mangrove forests are biogeochemical reactors that convert biomass into dissolved organic and inorganic carbon at unusually high rates, and many studies recognize the value of mangrove ecosystems for the substantial amounts of soil carbon storage they produce. However, questions remain as to how mangrove forest ecosystem services should be valuated and quantified. Therefore, this study addresses several objectives. First, we demonstrate that seasonal and annual net ecosystem carbon exchange in three selected mangrove forests, derived from long-term eddy covariance measurements, represent key quantities in defining the magnitude of biogeochemical cycling and together with other information on carbon cycle parameters serves as a proxy to estimate ecosystem services. Second, we model ecosystem productivity across the mangrove forests of Everglades National Park and southern China by relating net ecosystem exchange values to remote sensing data. Finally, we develop a carbon budget for the mangrove forests in the Everglades National Park for the purposes of demonstrating that these forests and adjacent estuaries are sites of intense biogeochemical cycling. One conclusion from this study is that much of the carbon entering from the atmosphere as net ecosystem exchange (~1000 g C m-2 yr-1) is not retained in the net ecosystem carbon balance. Instead, a substantial fraction of the carbon entering the system as net ecosystem exchange is ultimately exported to the oceans or outgassed as reaction products within the adjacent estuary.

  11. Modeling the biogeochemical seasonal cycle in the Strait of Gibraltar

    NASA Astrophysics Data System (ADS)

    Ramírez-Romero, E.; Vichi, M.; Castro, M.; Macías, J.; Macías, D.; García, C. M.; Bruno, M.

    2014-11-01

    A physical-biological coupled model was used to estimate the effect of the physical processes at the Strait of Gibraltar over the biogeochemical features of the Atlantic Inflow (AI) towards the Mediterranean Sea. This work was focused on the seasonal variation of the biogeochemical patterns in the AI and the role of the Strait; including primary production and phytoplankton features. As the physical model is 1D (horizontal) and two-layer, different integration methods for the primary production in the Biogeochemical Fluxes Model (BFM) have been evaluated. An approach based on the integration of a production-irradiance function was the chosen method. Using this Plankton Functional Type model (BFM), a simplified phytoplankton seasonal cycle in the AI was simulated. Main results included a principal bloom in spring dominated by nanoflagellates, whereas minimum biomass (mostly picophytoplankton) was simulated during summer. Physical processes occurring in the Strait could trigger primary production and raise phytoplankton biomass (during spring and autumn), mainly due to two combined effects. First, in the Strait a strong interfacial mixing (causing nutrient supply to the upper layer) is produced, and, second, a shoaling of the surface Atlantic layer occurs eastward. Our results show that these phenomena caused an integrated production of 105 g C m- 2 year- 1 in the eastern side of the Strait, and would also modify the proportion of the different phytoplankton groups. Nanoflagellates were favored during spring/autumn while picophytoplankton is more abundant in summer. Finally, AI could represent a relevant source of nutrients and biomass to Alboran Sea, fertilizing the upper layer of this area with 4.95 megatons nitrate year- 1 (79.83 gigamol year- 1) and 0.44 megatons C year- 1. A main advantage of this coupled model is the capability of solving relevant high-resolution processes as the tidal forcing without expensive computing requirements, allowing to assess the

  12. Biogeochemical Cycles for Combining Chemical Knowledge and ESD Issues in Greek Secondary Schools Part I: Designing the Didactic Materials

    ERIC Educational Resources Information Center

    Koutalidi, Sophia; Scoullos, Michael

    2016-01-01

    Biogeochemical cycles support all anthropogenic activities and are affected by them, therefore they are intricately interlinked with global environmental and socioeconomic issues. Elements of these cycles that are already included in the science/chemical curriculum and textbooks intended for formal education in Greek secondary schools were…

  13. Global changes in biogeochemical cycles in response to human activities

    NASA Technical Reports Server (NTRS)

    Moore, Berrien, III; Melillo, Jerry

    1994-01-01

    The main objective of our research was to characterize biogeochemical cycles at continental and global scales in both terrestrial and aquatic ecosystems. This characterization applied to both natural ecosystems and those disturbed by human activity. The primary elements of interest were carbon and nitrogen and the analysis sought to quantify standing stocks and dynamic cycling processes. The translocation of major nutrients from the terrestrial landscape to the atmosphere (via trace gases) and to fluvial systems (via leaching, erosional losses, and point source pollution) were of particular importance to this study. Our aim was to develop the first generation of Earth System Models. Our research was organized around the construction and testing of component biogeochemical models which treated terrestrial ecosystem processes, aquatic nutrient transport through drainage basins, and trace gas exchanges at the continental and global scale. A suite of three complementary models were defined within this construct. The models were organized to operate at a 1/2 degree latitude by longitude level of spatial resolution and to execute at a monthly time step. This discretization afforded us the opportunity to understand the dynamics of the biosphere down to subregional scales, while simultaneously placing these dynamics into a global context.

  14. The Impacts of Climate-Induced Drought on Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Peng, C.

    2014-12-01

    Terrestrial ecosystems and, in particular, forests exert strong controls on the global biogeochemical cycles and influence regional hydrology and climatology directly through water and surface energy budgets. Recent studies indicated that forest mortality caused by rising temperature and drought from around the world have unexpectedly increased in the past decade and they collectively illustrate the vulnerability of many forested ecosystems to rapid increases in tree mortality due to warmer temperatures and more severe drought. Persistent changes in tree mortality rates can alter forest structure, composition, and ecosystem services (such as albedo and carbon sequestration). Quantifying potential impacts of tree mortality on ecosystem processes requires research into mortality effects on carbon, energy, and water budgets at both site and regional levels. Despite recent progress, the uncertainty around mortality responses still limits our ability to predict the likelihood and anticipate the impacts of tree die-off. Studies are needed that explore tree death physiology for a wide variety of functional types, connect patterns of mortality with climate events, and quantify the impacts on carbon, energy, and water flux. In this presentation, I will highlight recent research progress, and identify key research needs and future challenges to predict the consequence and impacts of drought-induced large-scale forest mortality on biogeochemical cycles. I will focus on three main forest ecosystems (tropic rainforest in Amazon, temperate forest in Western USA, and boreal forest in Canada) as detailed case studies.

  15. Linking soil and sediment properties for research on biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Kuhn, Nikolaus J.

    2013-04-01

    Conventional perspectives on soil erosion include the on-site damage to soil and reductions in crop yield, as well as the resulting off-site effects on water quality, runoff and sediment loads in rivers. Our evolving understanding of the Earth System has added a new dimension to the role of soil erosion within the global geochemical cycles. First, the relevance of soil as a nutrient and Carbon (C) pool was recognized. Initially, the role of soils in the global C cycle was largely considered to be limited to a vertical exchange of greenhouse house gases (GHG) between vegetation, soil and atmosphere and thus mostly studied by soil scientists, plant ecologists and climatologists. Even Critical Zone research focused mostly on weathering and regolith properties and ignored lateral fluxes of dissolved or particulate organic matter. Since the late 1990s, a wider role of soils in biogeochemical cycles has emerged. Recent estimates place the lateral movement of C between soil and sediment pools in terrestrial ecosystems (including rivers and lakes) at approximately 0.6 to 1.5 Gt per year. Some of the eroded C is replaced by photosynthesis from the atmosphere, but at a cost of additional emissions, for example due to fertilizer production. The long-term fate of the eroded and deposited soil organic matter is subject to an open debate and suffers from a lack of reliable spatial information on lateral C fluxes and its subsequent fate in terrestrial ecosystems. The connection between soil C pool, GHG emissions and erosion illustrates the relevance of surface processes for the C fluxes between Earth's spheres. Accordingly, soil is now considered as mobile system to make accurate predictions about the consequences of global change for terrestrial biogeochemical cycles and climate feedbacks. This expanded perspective on soils as dynamic pool of weathering regolith, sediment, nutrients and C at the interface between the geospheres requires the analysis of relevant soil properties

  16. Linking Soil and Sediment Properties for research on Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Kuhn, N. J.

    2012-04-01

    Conventional perspectives on soil erosion include the on-site damage to soil and reductions in crop yield, as well as the resulting off-site effects on water quality, runoff and sediment loads in rivers. Our evolving understanding of the Earth System has added a new dimension to the role of soil erosion within the global geochemical cycles. First, the relevance of soil as a nutrient and Carbon (C) pool was recognized. Initially, the role of soils in the global C cycle was largely considered to be limited to a vertical exchange of greenhouse house gases (GHG) between vegetation, soil and atmosphere and thus mostly studied by soil scientists, plant ecologists and climatologists. Even Critical Zone research focused mostly on weathering and regolith properties and ignored lateral fluxes of dissolved or particulate organic matter. Since the late 1990s, a wider role of soils in biogeochemical cycles has emerged. Recent estimates place the lateral movement of C between soil and sediment pools in terrestrial ecosystems (including rivers and lakes) at approximately 0.6 to 1.5 Gt per year. Some of the eroded C is replaced by photosynthesis from the atmosphere, but at a cost of additional emissions, for example due to fertilizer production. The long-term fate of the eroded and deposited soil organic matter is subject to an open debate and suffers from a lack of reliable spatial information on lateral C fluxes and its subsequent fate in terrestrial ecosystems. The connection between soil C pool, GHG emissions and erosion illustrates the relevance of surface processes for the C fluxes between Earth's spheres. Accordingly, soil is now considered as mobile system to make accurate predictions about the consequences of global change for terrestrial biogeochemical cycles and climate feedbacks. This expanded perspective on soils as dynamic pool of weathering regolith, sediment, nutrients and C at the interface between the geospheres requires the analysis of relevant soil properties

  17. Biogeochemical cycling in terrestrial ecosystems - Modeling, measurement, and remote sensing

    NASA Technical Reports Server (NTRS)

    Peterson, D. L.; Matson, P. A.; Lawless, J. G.; Aber, J. D.; Vitousek, P. M.

    1985-01-01

    The use of modeling, remote sensing, and measurements to characterize the pathways and to measure the rate of biogeochemical cycling in forest ecosystems is described. The application of the process-level model to predict processes in intact forests and ecosystems response to disturbance is examined. The selection of research areas from contrasting climate regimes and sites having a fertility gradient in that regime is discussed, and the sites studied are listed. The use of remote sensing in determining leaf area index and canopy biochemistry is analyzed. Nitrous oxide emission is investigated by using a gas measurement instrument. Future research projects, which include studying the influence of changes on nutrient cycling in ecosystems and the effect of pollutants on the ecosystems, are discussed.

  18. Ecohydrological Interfaces as Dynamic Hotspots of Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    Krause, S.

    2015-12-01

    Ecohydrological interfaces, represent the boundaries between water-dependent ecosystems that can alter substantially the fluxes of energy and matter. There is still a critical gap of understanding the organisational principles of the drivers and controls of spatially and temporally variable ecohydrological interface functions. This knowledge gap limits our capacity to efficiently quantify, predict and manage the services provided by complex ecosystems. Many ecohydrological interfaces are characterized by step changes in microbial metabolic activity, steep redox gradients and often even thermodynamic phase shifts, for instance at the interfaces between atmosphere and water or soil matrix and macro-pores interfaces. This paper integrates investigations from point scale microcosm experiments with reach and subcatchment scale tracer experiments and numerical modeling studies to elaborate similarities in the drivers and controls that constitute the enhanced biogeochemical activity of different types of ecohydrologica interfaces across a range of spatial and temporal scales. We therefore combine smart metabolic activity tracers to quantify the impact of bioturbating benthic fauna onto ecosystem respiration and oxygen consumption and investigate at larger scale, how microbial metabolic activity and carbon turnover at the water-sediment interface are controlled by sediment physical and chemical properties as well as water temperatures. Numerical modeling confirmed that experimentally identified hotspots of streambed biogeochemical cycling were controlled by patterns of physical properties such as hydraulic conductivities or bioavailability of organic matter, impacting on residence time distributions and hence reaction times. In contrast to previous research, our investigations thus confirmed that small-scale variability of physical and chemical interface properties had a major impact on biogeochemical processing at the investigated ecohydrological interfaces. Our results

  19. Ecohydrological Interfaces as Dynamic Hotspots of Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    Krause, Stefan; Lewandowski, Joerg; Hannah, David; McDonald, Karlie; Folegot, Silvia; Baranov, Victor

    2016-04-01

    Ecohydrological interfaces, represent the boundaries between water-dependent ecosystems that can alter substantially the fluxes of energy and matter. There is still a critical gap of understanding the organisational principles of the drivers and controls of spatially and temporally variable ecohydrological interface functions. This knowledge gap limits our capacity to efficiently quantify, predict and manage the services provided by complex ecosystems. Many ecohydrological interfaces are characterized by step changes in microbial metabolic activity, steep redox gradients and often even thermodynamic phase shifts, for instance at the interfaces between atmosphere and water or soil matrix and macro-pores interfaces. This paper integrates investigations from point scale laboratory microcosm experiments with reach and subcatchment scale tracer experiments and numerical modeling studies to elaborate similarities in the drivers and controls that constitute the enhanced biogeochemical activity of different types of ecohydrologica interfaces across a range of spatial and temporal scales. We therefore combine smart metabolic activity tracers to quantify the impact of bioturbating benthic fauna onto ecosystem respiration and oxygen consumption and investigate at larger scale, how microbial metabolic activity and carbon turnover at the water-sediment interface are controlled by sediment physical and chemical properties as well as water temperatures. Numerical modeling confirmed that experimentally identified hotspots of streambed biogeochemical cycling were controlled by patterns of physical properties such as hydraulic conductivities or bioavailability of organic matter, impacting on residence time distributions and hence reaction times. In contrast to previous research, our investigations thus confirmed that small-scale variability of physical and chemical interface properties had a major impact on biogeochemical processing at the investigated ecohydrological interfaces

  20. Phototrophic bacteria and their role in the biogeochemical sulfur cycle

    NASA Technical Reports Server (NTRS)

    Trueper, H. G.

    1985-01-01

    An essential step that cannot be bypassed in the biogeochemical cycle of sulfur today is dissimilatory sulfate reduction by anaerobic bacteria. The enormous amounts of sulfides produced by these are oxidized again either anaerobically by phototrophic bacteria or aerobically by thiobacilli and large chemotrophic bacteria (Beggiatoa, Thiovulum, etc.). Phototrophic bacteria use sulfide, sulfur, thiosulfate, and sulfite as electron donors for photosynthesis. The most obvious intermediate in their oxidative sulfur metabolism is a long chain polysulfide that appears as so called sulfur globules either inside (Chromatiaceae) or outside (Ectothiorhodospiraceae, Chlorobiaceae, and some of the Rhodospirillaceae) the cells. The assimilation of sulfur compounds in phototrophic bacteria is in principle identical with that of nonphototrophic bacteria. However, the Chlorobiaceae and some of the Chromatiaceae and Rhodospirillaceae, unable to reduce sulfate, rely upon reduced sulfur for biosynthetic purposes.

  1. INTERACTIVE EFFECTS OF SOLAR UV RADIATION AND CLIMATE CHANGE ON BIOGEOCHEMICAL CYCLING

    EPA Science Inventory

    This paper assesses research on the interactions of UV radiation (280-400 nm) and global climate change with global biogeochemical cycles at the Earth's surface. The effects of UV-B (280-315 nm), which are dependent on the stratospheric ozone layer, on biogeochemical cycles are o...

  2. Watershed Management and Mercury Biogeochemical Cycling in Lake Zapotlan, Mexico

    NASA Astrophysics Data System (ADS)

    Malczyk, E. A.; Branfireun, B. A.

    2009-05-01

    Lake Zapotlan is an endorheic subtropical eutrophic lake located in Jalisco State, Mexico. The lake supports a small but important local fishery for carp (Cyprinus sp.) and tilapia (Oreochromis sp.) and is an internationally recognized RAMSAR site. Very little research exists in these regions regarding mercury biogeochemical cycling. The lake receives considerable untreated municipal wastewater discharge that is elevated in inorganic total mercury (250-800 ng Hg/L) and organic methylmercury (3-10 ng CH3Hg+/L). The lake is also located on an active fault zone near an active volcano which may cause natural mercury enrichment. To assess a mercury risk to the commercial fishery we investigated the distribution of total inorganic mercury and organic methylmercury in waters, sediments, and fish tissues of the lake, surrounding wetlands, and incoming waters. Although there were high concentrations of inorganic mercury entering the lake in wastewater and seasonal tributary stream flow inputs, average concentrations in lake surface waters (3 ng Hg/L) and sediments (50 ng Hg/gdw) were relatively low. Average concentrations of total inorganic mercury were an order of magnitude higher in water (70 ng Hg/L) and sediment (245 ng Hg/gdw) in wetlands receiving the wastewater discharges. Mercury loading to the main body of the lake is likely reduced by these wetland buffer zones which allow mercury bound to particulate matter to settle out. A similar pattern was seen with respect to methylmercury concentrations. Average concentrations of methylmercury in lake surface water (below detect) and sediment (0.1 ng/gdw) were lower than in impounded wetlands (1 ng CH3Hg+/L, 0.7 ng CH3Hg+/gdw). Mercury concentrations in tilapia (3.5 ng/g) and carp (8 ng/g) from the commercial catch were found to be low in mercury; likely due to a combination of physiological, biogeochemical, and ecological factors.

  3. Tracking evolution of urban biogeochemical cycles: salinization of fresh water

    NASA Astrophysics Data System (ADS)

    Kaushal, S.; McDowell, W. H.; Wollheim, W. M.; Duan, S.; Gorman, J. K.; Haq, S.; Hohman, S.; Smith, R. M.; Mayer, P. M.

    2014-12-01

    The built environment often changes quickly in response to human activities, thus contributing to an evolution of stream chemistry over time. Depending upon development and management strategies, these changes can result in pulses and/or long-term trends. Here, we explore patterns of evolving salinization of fresh water over time, and we evaluate the potential water quality implications of fresh water salinization. We show that there has been global salinization of freshwater across urbanizing landscapes over a century. We also show that human-accelerated weathering in watersheds and river alkalinization can further influence regional rates of salinization (in addition to anthropogenic sources such as road salts, sewage leaks, etc.). Finally, we investigate how salinization of fresh water can impact stream sediment fluxes of carbon, nutrients, and sulfate in watersheds across a land use gradient at the Baltimore Long-Term Ecological Research (LTER) site. The impacts of salinization on mobilization and uptake of carbon, nutrients, and sulfate in streams warrant further consideration in water quality management strategies. Overall, we propose that salinization can be a "universal tracer" of watershed urbanization globally with major regional consequences for drinking water and evolution of biogeochemical cycles in freshwater ecosystems.

  4. Suspended Particles: Their Role in Estuarine Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Turner, A.; Millward, G. E.

    2002-12-01

    Suspended particles are instrumental in controlling the reactivity, transport and biological impacts of substances in aquatic environments, and provide a crucial link for chemical constituents between the water column, bed sediment and food chain. This article reviews the role of suspended particles in the chemical and biological cycling of trace constituents (trace metals, organo-metallic compounds and hydrophobic organic micropollutants; HOMs) in estuaries, with particular emphasis on the effects of and changes to particle reactivity and composition. The partitioning (or distribution coefficient, KD ) and bioavailability of chemical constituents, and assimilation efficiency (AE) of such by bivalve suspension feeders, are identified as key parameters requiring definition for accurate biogeochemical modelling, and the discussion centres around the determination of and controls on these parameters. Particle-water interactions encompass a variety of physical, biological, electrostatic and hydrophobic effects, and are largely dependent on the character and concentration of suspended particles and salinity. The salinity-dependence results from the competing and complexing effects of seawater ions for trace metals, and the compression of water in the presence of dissolved seawater ions and consequent salting out of neutral solute (HOMs, organo-metallic compounds and some trace metal complexes). The extent of biological solubilization of chemical constituents from suspended particles is dependent on the nature of chemical components of the gastro-intestinal environment and their interactions with ingested particles, and the physiological (e.g. gut passage time) and chemical (e.g. redox conditions and pH) constraints imposed on these interactions. Generally, chemicals that associate with fine, organic-rich particles (or, for some HOMs, fine inorganic particles), and desorb at pH 5-6 and/or complex with digestive enzymes or surfactants are most readily solubilized in the

  5. SEASONAL VARIATION IN THE BIOGEOCHEMICAL CYCLING OF SESTON IN GRAND TRAVERSE BAY, LAKE MICHIGAN. (R825151)

    EPA Science Inventory

    This study describes the biogeochemical cycling of seston in Grand Traverse Bay, Lake Michigan. Seston was characterized by carbon and nitrogen elemental and isotopic abundances. Fluorescence, temperature, light transmittance, and concentrations of dissolved inorganic nitrogen we...

  6. Interactions of Biogeochemical Cycles in Oncoid Microbialites from Cuatro Ciénegas, Mexico

    NASA Astrophysics Data System (ADS)

    Corman, J. R.; Souza, V.; Elser, J. J.

    2010-04-01

    Modern microbialite systems may provide unique opportunities to study the feedbacks that couple or uncouple multiple biogeochemical cycles. Here we present results from a two-week manipulative ecosystem experiment using oncoid microbialites from Cuatro Ciénegas, Mexico.

  7. Characterizing marine particles and their impact on biogeochemical cycles in the GEOTRACES program

    NASA Astrophysics Data System (ADS)

    Anderson, Robert F.; Hayes, Christopher T.

    2015-04-01

    Trace elements and their isotopes (TEIs) are of priority interest in several subdisciplines of oceanography. For example, the vital role of trace element micronutrients in regulating the growth of marine organisms, which, in turn, may influence the structure and composition of marine ecosystems, is now well established (Morel and Price, 2003; Twining and Baines, 2013). Natural distributions of some TEIs have been severely impacted by anthropogenic emissions, leading to substantial perturbations of natural ocean inventories. Pb and Hg, for example, (Lamborg et al., 2002; Schaule and Patterson, 1981), may represent a significant threat to human food supply. Furthermore, much of our knowledge of past variability in the ocean environment, including the ocean's role in climate change, has been developed using TEI proxies archived in marine substrates such as sediments, corals and microfossils. Research in each of these areas relies on a comprehensive knowledge of the distributions of TEIs in the ocean, and on the sensitivity of these distributions to changing environmental conditions. With numerous processes affecting the regional supply and removal of TEIs in the ocean, a comprehensive understanding of the marine biogeochemical cycles of TEIs can be attained only by a global, coordinated, international effort. GEOTRACES, an international program designed to study the marine biogeochemical cycles of trace elements and their isotopes (Anderson et al., 2014; Henderson et al., 2007), aims to achieve these goals.

  8. Effects of solar UV radiation and climate change on biogeochemical cycling: Interactions and feedbacks

    SciTech Connect

    Erickson III, David J

    2011-01-01

    Solar UV radiation, climate and other drivers of global change are undergoing significant changes and models forecast that these changes will continue for the remainder of this century. Here we assess the effects of solar UV radiation on biogeochemical cycles and the interactions of these effects with climate change, including feedbacks on climate. Such interactions occur in both terrestrial and aquatic ecosystems. While there is significant uncertainty in the quantification of these effects, they could accelerate the rate of atmospheric CO{sub 2} increase and subsequent climate change beyond current predictions. The effects of predicted changes in climate and solar UV radiation on carbon cycling in terrestrial and aquatic ecosystems are expected to vary significantly between regions. The balance of positive and negative effects on terrestrial carbon cycling remains uncertain, but the interactions between UV radiation and climate change are likely to contribute to decreasing sink strength in many oceanic regions. Interactions between climate and solar UV radiation will affect cycling of elements other than carbon, and so will influence the concentration of greenhouse and ozone-depleting gases. For example, increases in oxygen-deficient regions of the ocean caused by climate change are projected to enhance the emissions of nitrous oxide, an important greenhouse and ozone-depleting gas. Future changes in UV-induced transformations of aquatic and terrestrial contaminants could have both beneficial and adverse effects. Taken in total, it is clear that the future changes in UV radiation coupled with human-caused global change will have large impacts on biogeochemical cycles at local, regional and global scales.

  9. Effects of solar UV radiation and climate change on biogeochemical cycling: interactions and feedbacks.

    PubMed

    Zepp, R G; Erickson, D J; Paul, N D; Sulzberger, B

    2011-02-01

    Solar UV radiation, climate and other drivers of global change are undergoing significant changes and models forecast that these changes will continue for the remainder of this century. Here we assess the effects of solar UV radiation on biogeochemical cycles and the interactions of these effects with climate change, including feedbacks on climate. Such interactions occur in both terrestrial and aquatic ecosystems. While there is significant uncertainty in the quantification of these effects, they could accelerate the rate of atmospheric CO(2) increase and subsequent climate change beyond current predictions. The effects of predicted changes in climate and solar UV radiation on carbon cycling in terrestrial and aquatic ecosystems are expected to vary significantly between regions. The balance of positive and negative effects on terrestrial carbon cycling remains uncertain, but the interactions between UV radiation and climate change are likely to contribute to decreasing sink strength in many oceanic regions. Interactions between climate and solar UV radiation will affect cycling of elements other than carbon, and so will influence the concentration of greenhouse and ozone-depleting gases. For example, increases in oxygen-deficient regions of the ocean caused by climate change are projected to enhance the emissions of nitrous oxide, an important greenhouse and ozone-depleting gas. Future changes in UV-induced transformations of aquatic and terrestrial contaminants could have both beneficial and adverse effects. Taken in total, it is clear that the future changes in UV radiation coupled with human-caused global change will have large impacts on biogeochemical cycles at local, regional and global scales. PMID:21253663

  10. Interactive effects of solar UV radiation and climate change on biogeochemical cycling.

    PubMed

    Zepp, R G; Erickson, D J; Paul, N D; Sulzberger, B

    2007-03-01

    This report assesses research on the interactions of UV radiation (280-400 nm) and global climate change with global biogeochemical cycles at the Earth's surface. The effects of UV-B (280-315 nm), which are dependent on the stratospheric ozone layer, on biogeochemical cycles are often linked to concurrent exposure to UV-A radiation (315-400 nm), which is influenced by global climate change. These interactions involving UV radiation (the combination of UV-B and UV-A) are central to the prediction and evaluation of future Earth environmental conditions. There is increasing evidence that elevated UV-B radiation has significant effects on the terrestrial biosphere with implications for the cycling of carbon, nitrogen and other elements. The cycling of carbon and inorganic nutrients such as nitrogen can be affected by UV-B-mediated changes in communities of soil organisms, probably due to the effects of UV-B radiation on plant root exudation and/or the chemistry of dead plant material falling to the soil. In arid environments direct photodegradation can play a major role in the decay of plant litter, and UV-B radiation is responsible for a significant part of this photodegradation. UV-B radiation strongly influences aquatic carbon, nitrogen, sulfur and metals cycling that affect a wide range of life processes. UV-B radiation changes the biological availability of dissolved organic matter to microorganisms, and accelerates its transformation into dissolved inorganic carbon and nitrogen, including carbon dioxide and ammonium. The coloured part of dissolved organic matter (CDOM) controls the penetration of UV radiation into water bodies, but CDOM is also photodegraded by solar UV radiation. Changes in CDOM influence the penetration of UV radiation into water bodies with major consequences for aquatic biogeochemical processes. Changes in aquatic primary productivity and decomposition due to climate-related changes in circulation and nutrient supply occur concurrently with

  11. The Neoproterozoic oxygenation event: Environmental perturbations and biogeochemical cycling

    NASA Astrophysics Data System (ADS)

    Och, Lawrence M.; Shields-Zhou, Graham A.

    2012-01-01

    The oxygen content of the Earth's surface environment is thought to have increased in two broad steps: the Great Oxygenation Event (GOE) around the Archean-Proterozoic boundary and the Neoproterozoic Oxygenation Event (NOE), during which oxygen possibly accumulated to the levels required to support animal life and ventilate the deep oceans. Although the concept of the GOE is widely accepted, the NOE is less well constrained and its timing and extent remain the subjects of debate. We review available evidence for the NOE against the background of major climatic perturbations, tectonic upheaval related to the break-up of the supercontinent Rodinia and reassembly into Gondwana, and, most importantly, major biological innovations exemplified by the Ediacarian Biota and the Cambrian 'Explosion'. Geochemical lines of evidence for the NOE include perturbations to the biogeochemical cycling of carbon. Generally high δ 13C values are possibly indicative of increased organic carbon burial and the release of oxidative power to the Earth's surface environment after c. 800 Ma. A demonstrably global and primary record of extremely negative δ 13C values after about 580 Ma strongly suggests the oxidation of a large dissolved organic carbon pool (DOC), the culmination of which around c. 550 Ma coincided with an abrupt diversification of Ediacaran macrobiota. Increasing 87Sr/ 86Sr ratios toward the Neoproterozoic-Cambrian transition indicates enhanced continental weathering which may have fuelled higher organic production and burial during the later Neoproterozoic. Evidence for enhanced oxidative recycling is given by the increase in sulfur isotope fractionation between sulfide and sulfate, exceeding the range usually attained by sulfate reduction alone, reflecting an increasing importance of the oxidative part in the sulfur cycle. S/C ratios attained a maximum during the Precambrian-Cambrian transition, further indicating higher sulfate concentrations in the ocean and a

  12. Earth's Early Biosphere and the Biogeochemical Carbon Cycle

    NASA Technical Reports Server (NTRS)

    DesMarais, David

    2004-01-01

    Our biosphere has altered the global environment principally by influencing the chemistry of those elements most important for life, e g., C, N, S, O, P and transition metals (e.g., Fe and Mn). The coupling of oxygenic photosynthesis with the burial in sediments of photosynthetic organic matter, and with the escape of H2 to space, has increased the state of oxidation of the Oceans and atmosphere. It has also created highly reduced conditions within sedimentary rocks that have also extensively affected the geochemistry of several elements. The decline of volcanism during Earth's history reduced the flow of reduced chemical species that reacted with photosynthetically produced O2. The long-term net accumulation of photosynthetic O2 via biogeochemical processes has profoundly influenced our atmosphere and biosphere, as evidenced by the O2 levels required for algae, multicellular life and certain modem aerobic bacteria to exist. When our biosphere developed photosynthesis, it tapped into an energy resource that was much larger than the energy available from oxidation-reduction reactions associated with weathering and hydrothermal activity. Today, hydrothermal sources deliver globally (0.13-1.1)x10(exp l2) mol yr(sup -1) of reduced S, Fe(2+), Mn(2+), H2 and CH4; this is estimated to sustain at most about (0.2-2)xl0(exp 12)mol C yr(sup -1) of organic carbon production by chemautotrophic microorganisms. In contrast, global photosynthetic productivity is estimated to be 9000x10(exp 12) mol C yr(sup -1). Thus, even though global thermal fluxes were greater in the distant geologic past than today, the onset of oxygenic photosynthesis probably increased global organic productivity by some two or more orders of magnitude. This enormous productivity materialized principally because oxygenic photosynthesizers unleashed a virtually unlimited supply of reduced H that forever freed life from its sole dependence upon abiotic sources of reducing power such as hydrothermal emanations

  13. Accounting for the biogeochemical cycle of nitrogen in input-output life cycle assessment.

    PubMed

    Singh, Shweta; Bakshi, Bhavik R

    2013-08-20

    Nitrogen is indispensable for sustaining human activities through its role in the production of food, animal feed, and synthetic chemicals. This has encouraged significant anthropogenic mobilization of reactive nitrogen and its emissions into the environment resulting in severe disruption of the nitrogen cycle. This paper incorporates the biogeochemical cycle of nitrogen into the 2002 input-output model of the U.S. economy. Due to the complexity of this cycle, this work proposes a unique classification of nitrogen flows to facilitate understanding of the interaction between economic activities and various flows in the nitrogen cycle. The classification scheme distinguishes between the mobilization of inert nitrogen into its reactive form, use of nitrogen in various products, and nitrogen losses to the environment. The resulting inventory and model of the US economy can help quantify the direct and indirect impacts or dependence of economic sectors on the nitrogen cycle. This paper emphasizes the need for methods to manage the N cycle that focus not just on N losses, which has been the norm until now, but also include other N flows for a more comprehensive view and balanced decisions. Insight into the N profile of various sectors of the 2002 U.S. economy is presented, and the inventory can also be used for LCA or Hybrid LCA of various products. The resulting model is incorporated in the approach of Ecologically-Based LCA and available online. PMID:23869533

  14. Biogeochemical Cycles of Carbon and Sulfur on Early Earth (and on Mars?)

    NASA Technical Reports Server (NTRS)

    DesMarais, D. J.

    2004-01-01

    The physical and chemical interactions between the atmosphere, hydrosphere, geosphere and biosphere can be examined for elements such as carbon (C) and sulfur (S) that have played central roles for both life and the environment. The compounds of C are highly important, not only as organic matter, but also as atmospheric greenhouse gases, pH buffers in seawater, oxidation-reduction buffers virtually everywhere, and key magmatic constituents affecting plutonism and volcanism. S assumes important roles as an oxidation-reduction partner with C and Fe in biological systems, as a key constituent in magmas and volcanic gases, and as a major influence upon pH in certain environments. These multiple roles of C and S interact across a network of elemental reservoirs interconnected by physical, chemical and biological processes. These networks are termed biogeochemical C and S cycles.

  15. A GIS-based Framework for Examining the Effects of Water-Driven Erosion on Soil Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    Abban, B. K.; Papanicolaou, T.; Wacha, K.; Wilson, C. G.

    2014-12-01

    Soil erosion has long been identified as one of the key mechanisms affecting biogeochemical processes in the soil, through the transport and delivery of carbon and nutrients adsorbed to soil particles in the soil active layer. However, most biogeochemical models treat soil erosion contributions simplistically and lack the capacity to accurately account for the mechanisms that control soil erosion and deposition on the landscape. This stems from the fact that the majority of the biogeochemical models have traditionally been employed on landscapes where lateral and downslope fluxes due to soil erosion have been less significant compared to other vertical fluxes and processes occurring at a fixed location on the landscape. In intensely managed landscapes, however, this may not be the case since land management practices such as tillage and exposed land cover can lead to copious amounts of erosion on the landscape. Therefore, to better understand the role of soil erosion on soil biogeochemical cycling in IMLs, we present a framework for simulating the spatiotemporal effects of soil erosion and deposition on soil biogeochemical cycling. We focus specifically on tillage- and runoff-induced erosion since these are prevalent in IMLs. The framework employs a geospatial approach that loosely couples a GIS-based upland water erosion model, GeoWEPP, with a soil biogeochemistry model, Century, to predict downslope and lateral fluxes of soil erosion and the resultant impacts on soil biogeochemical cycling. The use of a geospatial approach allows us to better capture the effects of topography, soil type, land use/land cover, and climate on soil erosion fluxes as well as soil biogeochemical cycling. The spatiotemporal resolution of the framework makes it particularly beneficial for identifying hotspots in fields and hot moments at scales ranging from daily to annual time scales. We employ the framework to study the monthly redistribution of soil organic carbon over the course of a

  16. Biogeochemical cycles of Chernobyl-born radionuclides in the contaminated forest ecosystems: long-term dynamics of the migration processes

    NASA Astrophysics Data System (ADS)

    Shcheglov, Alexey; Tsvetnova, Ol'ga; Klyashtorin, Alexey

    2013-04-01

    Biogeochemical migration is a dominant factor of the radionuclide transport through the biosphere. In the early XX century, V.I. Vernadskii, a Russian scientist known, noted about a special role living things play in transport and accumulation of natural radionuclide in various environments. The role of biogeochemical processes in migration and redistribution of technogenic radionuclides is not less important. In Russia, V. M. Klechkovskii and N.V. Timofeev-Ressovskii showed some important biogeochemical aspects of radionuclide migration by the example of global fallout and Kyshtym accident. Their followers, R.M. Alexakhin, M.A. Naryshkin, N.V. Kulikov, F.A. Tikhomirov, E.B. Tyuryukanova, and others also contributed a lot to biogeochemistry of radionuclides. In the post-Chernobyl period, this area of knowledge received a lot of data that allowed building the radioactive element balance and flux estimation in various biogeochemical cycles [Shcheglov et al., 1999]. Regrettably, many of recent radioecological studies are only focused on specific radionuclide fluxes or pursue some applied tasks, missing the holistic approach. Most of the studies consider biogeochemical fluxes of radioactive isotopes in terms of either dose estimation or radionuclide migration rates in various food chains. However, to get a comprehensive picture and develop a reliable forecast of environmental, ecological, and social consequences of radioactive pollution in a vast contaminated area, it is necessary to investigate all the radionuclide fluxes associated with the biogeochemical cycles in affected ecosystems. We believe such an integrated approach would be useful to study long-term environmental consequences of the Fukushima accident as well. In our long-term research, we tried to characterize the flux dynamics of the Chernobyl-born radionuclides in the contaminated forest ecosystems and landscapes as a part of the integrated biogeochemical process. Our field studies were started in June of

  17. Deep Carbon Cycling in the Deep Hydrosphere: Abiotic Organic Synthesis and Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    Sherwood Lollar, B.; Sutcliffe, C. N.; Ballentine, C. J.; Warr, O.; Li, L.; Ono, S.; Wang, D. T.

    2014-12-01

    Research into the deep carbon cycle has expanded our understanding of the depth and extent of abiotic organic synthesis in the deep Earth beyond the hydrothermal vents of the deep ocean floor, and of the role of reduced gases in supporting deep subsurface microbial communities. Most recently, this research has expanded our understanding not only of the deep biosphere but the deep hydrosphere - identifying for the first time the extreme antiquity (millions to billions of years residence time) of deep saline fracture waters in the world's oldest rocks. Energy-rich saline fracture waters in the Precambrian crust that makes up more than 70% of the Earth's continental lithosphereprovide important constraints on our understanding of the extent of the crust that is habitable, on the time scales of hydrogeologic isolation (and conversely mixing) of fluids relevant to the deep carbon cycle, and on the geochemistry of substrates that sustain both abiotic organic synthesis and biogeochemical cycles driven by microbial communities. Ultimately the chemistry and hydrogeology of the deep hydrosphere will help define the limits for life in the subsurface and the boundary between the biotic-abiotic fringe. Using a variety of novel techniques including noble gas analysis, clumped isotopologues of methane, and compound specific isotope analysis of CHNOS, this research is addressing questions about the distribution of deep saline fluids in Precambrian rocks worldwide, the degree of interconnectedness of these potential biomes, the habitability of these fluids, and the biogeographic diversity of this new realm of the deep hydrosphere.

  18. Insight from Genomics on Biogeochemical Cycles in a Shallow-Sea Hydrothermal System

    NASA Astrophysics Data System (ADS)

    Lu, G. S.; Amend, J.

    2015-12-01

    Shallow-sea hydrothermal ecosystems are dynamic, high-energy systems influenced by sunlight and geothermal activity. They provide accessible opportunities for investigating thermophilic microbial biogeochemical cycles. In this study, we report biogeochemical data from a shallow-sea hydrothermal system offshore Paleochori Bay, Milos, Greece, which is characterized by a central vent covered by white microbial mats with hydrothermally influenced sediments extending into nearby sea grass area. Geochemical analysis and deep sequencing provide high-resolution information on the geochemical patterns, microbial diversity and metabolic potential in a two-meter transect. The venting fluid is elevated in temperature (~70oC), low in pH (~4), and enriched in reduced species. The geochemical pattern shows that the profile is affected by not only seawater dilution but also microbial regulation. The microbial community in the deepest section of vent core (10-12 cm) is largely dominated by thermophilic archaea, including a methanogen and a recently described Crenarcheon. Mid-core (6-8 cm), the microbial community in the venting area switches to the hydrogen utilizer Aquificae. Near the sediment-water interface, anaerobic Firmicutes and Actinobacteria dominate, both of which are commonly associated with subsurface and hydrothermal sites. All other samples are dominated by diverse Proteobacteria. The sulfate profile is strongly correlated with the population size of delta- and episilon-proteobactia. The dramatic decrease in concentrations of As and Mn in pore fluids as a function of distance from the vent suggests that in addition to seawater dilution, microorganisms are likely transforming these and other ions through a combination of detoxification and catabolism. In addition, high concentrations of dissolved Fe are only measurable in the shallow sea grass area, suggesting that iron-transforming microorganisms are controlling Fe mobility, and promoting biomineralization. Taken

  19. Overview of the 1988 GCE/CASE/WATOX Studies of biogeochemical cycles in the North Atlantic region

    NASA Astrophysics Data System (ADS)

    Pszenny, Alexander A. P.; Galloway, James N.; Artz, Richard S.; Boatman, Joseph F.

    1990-06-01

    The 1988 Global Change Expedition/Coordinated Air-Sea Experiment/Western Atlantic Ocean Experiment (GCE/CASE/WATOX) was a multifaceted research program designed to study atmospheric and oceanic processes affecting the biogeochemical cycles of carbon, nitrogen, sulfur, and trace metals in the North Atlantic Ocean region. Field work included (1) a 49-day research cruise aboard NOAA ship Mt. Mitchell (Global Change Expedition) from Norfolk, Virginia, to Bermuda, Iceland, the Azores, and Barbados, (2) eight flights of the NOAA King Air research aircraft, four off the Virginia Capes and four near Bermuda (CASE/WATOX), and (3) a research cruise aboard the yacht Fleurtie near Bermuda (WATOX). Objectives of GCE/CASE/WATOX were (1) to examine processes controlling the mesoscale distributions of productivity, chlorophyll, and phytoplankton growth rates in Atlantic surface waters, (2) to identify factors controlling the distribution of ozone in the North Atlantic marine boundary layer, and (3) to estimate the contributions of sources on surrounding continents to the biogeochemical cycles of sulfur, nitrogen, and trace metals over the North Atlantic region during the boreal summer season. The individual papers in this and the next two issues of Global Biogeochemical Cycles provide details on the results and analyses of the individual measurement efforts. This paper provides a brief overview of GCE/CASE/WATOX.

  20. The Biogeochemical Cycling of Nitrogen in Annual and Perennial Agroecosystems

    NASA Astrophysics Data System (ADS)

    Fortuna, A.; Cogger, C.

    2010-12-01

    Organic agricultural systems are dependent upon fertilizer amendments that undergo ammonification prior to the release of plant available nitrogen (N) as ammonium. Ammonia may be further transformed via nitrification to nitrate resulting in greater potential for leaching or volatilization. Additions of plant residue and animal amendments contribute to soil N and carbon pools improving soil quality and the potential for release of ammonium. Therefore, agricultural systems that relay on organic inputs as fertilizer sources must be monitored to insure stored nutrients are released during plant uptake to prevent N losses. Our experimental design allows us to determine the effects of several organic cropping systems and fertility regimes on plant available N, nitrification potential and nitrifier gene copy number g-1 dry soil across season in a grass ley and two annual systems receiving chicken manure or compost. Nitrification potentials measured via the shaken slurry method, KCl extractable N and ammonia oxidizing bacteria (AOB) and archaea (AOA) gene copy numbers g-1 dry soil measured via quantitative PCR were monitored. Nitrification potentials measured in March revealed increases in nitrification where compost had historically been applied (7.78 vs. 5.26 ± 0.856). Treatment affects were significant in June the closest date to application of amendments and when ammonification from soil N was optimal. Animal amendments were added yearly in annual systems (31.0 ± 2.91) vs every three years in the ley pasture (12.9 ± 2.91) resulting in a management effect. Copy numbers of AOB (2.69 x 108 ± 4.94 x 107) were greatest in plots receiving compost vs chicken manure. Preliminary measurements of AOA gene copy numbers reveal a similar trend to that of AOB. But, gene copy numbers of AOA (105 to 106) were lower than those of AOB. Nitrification potentials were not different across treatments in September, 11.8 ± 2.28. This research will contribute to the development of novel

  1. Effects of Solar UV Radiation and Climate Change on Biogeochemical Cycling: Interactions and Feedbacks

    EPA Science Inventory

    Solar UV radiation, climate and other drivers of global change are undergoing significant changes and models forecast that these changes will continue for the remainder of this century. Here we assess the effects of solar UV radiation on biogeochemical cycles and the interactions...

  2. INTERACTIVE EFFECTS OF OZONE DEPLETION AND CLIMATE CHANGE ON BIOGEOCHEMICAL CYCLES

    EPA Science Inventory

    The effects of ozone depletion on global biogeochemical cycles, via increased UV-B radiation at the Earth's surface, have continued to be documented over the past 4 years. In this report we also document various effects of UV-B that interact with global climate change because the...

  3. INTERACTIONS OF CHANGING CLIMATE AND ULTRAVIOLET RADIATION IN AQUATIC AND TERRESTRIAL BIOGEOCHEMICAL CYCLES

    EPA Science Inventory

    During the past decade interest has developed in the interactive effects of climate change and UV radiation on aquatic and terrestrial biogeochemical cycles. This talk used selected case studies to illustrate approaches that are being used to investigate these intriguing processe...

  4. Towards coupled physical-biogeochemical models of the ocean carbon cycle

    NASA Technical Reports Server (NTRS)

    Rintoul, Stephen R.

    1992-01-01

    The purpose of this review is to discuss the critical gaps in our knowledge of ocean dynamics and biogeochemical cycles. It is assumed that the ultimate goal is the design of a model of the earth system that can predict the response to changes in the external forces driving climate.

  5. Biogeochemical responses of the carbon cycle to natural and human perturbations: Past, present, and future

    SciTech Connect

    Ver, L.M.B.; Mackenzie, F.T.; Lerman, A.

    1999-07-01

    In the past three centuries, human perturbations of the environment have affected the biogeochemical behavior of the global carbon cycle and that of the other three nutrient elements closely coupled to carbon: nitrogen, phosphorus, and sulfur. The partitioning of anthropogenic CO{sub 2} among its various sinks in the past, for the present, and for projections into the near future is controlled by the interactions of these four elemental cycles within the major environmental domains of the land, atmosphere, coastal oceanic zone, and open ocean. The authors analyze the past, present, and future behavior of the global carbon cycle using the Terrestrial-Ocean-aTmosphere Ecosystem Model (TOTEM), a unique process-based model of the four global coupled biogeochemical cycles of carbon, nitrogen, phosphorus, and sulfur. They find that during the past 300 yrs, anthropogenic CO{sub 2} was mainly stored in the atmosphere and in the open ocean. Human activities on land caused an enhanced loss of mass from the terrestrial organic matter reservoirs (phytomass and humus) mainly through deforestation and consequently increased humus remineralization, erosion, and transport to the coastal margins by rivers and runoff. Photosynthetic uptake by the terrestrial phytomass was enhanced owing to fertilization by increasing atmospheric CO{sub 2} concentrations and supported by nutrients remineralized from organic matter. TOTEM results indicate that through most of the past 300 yrs, the loss of C from deforestation and other land-use activities was greater than the gain from the enhanced photosynthetic uptake. Since pre-industrial time (since 1700), the net flux of CO{sub 2} from the coastal waters has decreased by 40%, from 0.20 Gt C/yr to 0.12 Gt C/yr. TOTEM analyses of atmospheric CO{sub 2} concentrations for the 21st century were based on the fossil-fuel emission projections of IPCC (business as usual scenario) and of the more restrictive UN 1997 Kyoto Protocol. By the mid-21st century

  6. Biomass burning in the tropics: impact on atmospheric chemistry and biogeochemical cycles.

    PubMed

    Crutzen, P J; Andreae, M O

    1990-12-21

    Biomass burning is widespread, especially in the tropics. It serves to clear land for shifting cultivation, to convert forests to agricultural and pastoral lands, and to remove dry vegetation in order to promote agricultural productivity and the growth of higher yield grasses. Furthermore, much agricultural waste and fuel wood is being combusted, particularly in developing countries. Biomass containing 2 to 5 petagrams of carbon is burned annually (1 petagram = 10(15) grams), producing large amounts of trace gases and aerosol particles that play important roles in atmospheric chemistry and climate. Emissions of carbon monoxide and methane by biomass burning affect the oxidation efficiency of the atmosphere by reacting with hydroxyl radicals, and emissions of nitric oxide and hydrocarbons lead to high ozone concentrations in the tropics during the dry season. Large quantities of smoke particles are produced as well, and these can serve as cloud condensation nuclei. These particles may thus substantially influence cloud microphysical and optical properties, an effect that could have repercussions for the radiation budget and the hydrological cycle in the tropics. Widespread burning may also disturb biogeochemical cycles, especially that of nitrogen. About 50 percent of the nitrogen in the biomass fuel can be released as molecular nitrogen. This pyrdenitrification process causes a sizable loss of fixed nitrogen in tropical ecosystems, in the range of 10 to 20 teragrams per year (1 teragram = 10(12) grams). PMID:17734705

  7. Effects of Stratospheric Ozone Depletion, Solar UV Radiation, and Climate Change on Biogeochemical Cycling: Interactions and Feedbacks

    EPA Science Inventory

    Climate change modulates the effects of solar UV radiation on biogeochemical cycles in terrestrial and aquatic ecosystems, particularly for carbon cycling, resulting in UV-mediated positive or negative feedbacks on climate. Possible positive feedbacks discussed in this assessment...

  8. Biogeochemical cycle of arsenic and calculating the enrichment factor by using Li element.

    PubMed

    Aksu, Abdullah; Balkis, Nuray; Erşan, Mahmut S; Müftüoğlu, A E; Apak, Reşat

    2010-08-01

    In this study, the biogeochemical cycle of arsenic in the Bosporus and the Golden Horn, which have a two-layer stratified structure, was investigated and the dominant feature in this cycle was observed to be the anthropogenic (domestic + industrial) activities. On the contrary, in the rural areas which are far from human activities, such as Iğneada, the seawater-atmosphere interchange can be observed evidently in the periods covering the primary production. PMID:20379841

  9. Key biogeochemical factors affecting soil carbon storage in Posidonia meadows

    NASA Astrophysics Data System (ADS)

    Serrano, Oscar; Ricart, Aurora M.; Lavery, Paul S.; Mateo, Miguel Angel; Arias-Ortiz, Ariane; Masque, Pere; Rozaimi, Mohammad; Steven, Andy; Duarte, Carlos M.

    2016-08-01

    Biotic and abiotic factors influence the accumulation of organic carbon (Corg) in seagrass ecosystems. We surveyed Posidonia sinuosa meadows growing in different water depths to assess the variability in the sources, stocks and accumulation rates of Corg. We show that over the last 500 years, P. sinuosa meadows closer to the upper limit of distribution (at 2-4 m depth) accumulated 3- to 4-fold higher Corg stocks (averaging 6.3 kg Corg m-2) at 3- to 4-fold higher rates (12.8 g Corg m-2 yr-1) compared to meadows closer to the deep limits of distribution (at 6-8 m depth; 1.8 kg Corg m-2 and 3.6 g Corg m-2 yr-1). In shallower meadows, Corg stocks were mostly derived from seagrass detritus (88 % in average) compared to meadows closer to the deep limit of distribution (45 % on average). In addition, soil accumulation rates and fine-grained sediment content (< 0.125 mm) in shallower meadows (2.0 mm yr-1 and 9 %, respectively) were approximately 2-fold higher than in deeper meadows (1.2 mm yr-1 and 5 %, respectively). The Corg stocks and accumulation rates accumulated over the last 500 years in bare sediments (0.6 kg Corg m-2 and 1.2 g Corg m-2 yr-1) were 3- to 11-fold lower than in P. sinuosa meadows, while fine-grained sediment content (1 %) and seagrass detritus contribution to the Corg pool (20 %) were 8- and 3-fold lower than in Posidonia meadows, respectively. The patterns found support the hypothesis that Corg storage in seagrass soils is influenced by interactions of biological (e.g., meadow productivity, cover and density), chemical (e.g., recalcitrance of Corg stocks) and physical (e.g., hydrodynamic energy and soil accumulation rates) factors within the meadow. We conclude that there is a need to improve global estimates of seagrass carbon storage accounting for biogeochemical factors driving variability within habitats.

  10. Key biogeochemical factors affecting soil carbon storage in Posidonia meadows

    NASA Astrophysics Data System (ADS)

    Serrano, O.; Ricart, A. M.; Lavery, P. S.; Mateo, M. A.; Arias-Ortiz, A.; Masque, P.; Steven, A.; Duarte, C. M.

    2015-11-01

    Biotic and abiotic factors influence the accumulation of organic carbon (Corg) in seagrass ecosystems. We surveyed Posidonia sinuosa meadows growing in different water depths to assess the variability in the sources, stocks and accumulation rates of Corg. We show that over the last 500 years, P. sinuosa meadows closer to the upper limit of distribution (at 2-4 m depth) accumulated 3 to 4-fold higher Corg stocks (averaging 6.3 kg Corg m-2) at 3 to 4-fold higher rates (12.8 g Corg m-2 yr-1) compared to meadows closer to the deep limits of distribution (at 6-8 m depth; 1.8 kg Corg m-2 and 3.6 g Corg m-2 yr-1). In shallower meadows, Corg stores were mostly derived from seagrass detritus (88 % in average) compared to meadows closer to the deep limit of distribution (45 % on average). Also, sediment accumulation rates and fine-grained sediment content (< 0.125 mm) in shallower meadows (2.0 mm yr-1 and 9 %, respectively) were approximately 2-fold higher than in deeper meadows (1.2 mm yr-1 and 5 %, respectively). The Corg stocks and accumulation rates accumulated over the last 500 years in bare sediments (0.6 kg Corg m-2 and 1.2 g Corg m-2 yr-1) were 3 to 11-fold lower than in P. sinuosa meadows, while fine-grained sediment content (1 %) and seagrass detritus contribution to the Corg pool (20 %) were 8 and 3-fold lower than in Posidonia meadows, respectively. The patterns found support the hypotheses that Corg storage in seagrass soils is influenced by interactions of biological (e.g. meadow productivity, cover and density), chemical (e.g. recalcitrance of Corg stocks) and physical (e.g. hydrodynamic energy and sediment accumulation rates) factors within the meadow. We conclude that there is a need to improve global estimates of seagrass carbon storage accounting for biogeochemical factors driving variability within habitats.

  11. The biogeochemical role of baleen whales and krill in Southern Ocean nutrient cycling.

    PubMed

    Ratnarajah, Lavenia; Bowie, Andrew R; Lannuzel, Delphine; Meiners, Klaus M; Nicol, Stephen

    2014-01-01

    The availability of micronutrients is a key factor that affects primary productivity in High Nutrient Low Chlorophyll (HNLC) regions of the Southern Ocean. Nutrient supply is governed by a range of physical, chemical and biological processes, and there are significant feedbacks within the ecosystem. It has been suggested that baleen whales form a crucial part of biogeochemical cycling processes through the consumption of nutrient-rich krill and subsequent defecation, but data on their contribution are scarce. We analysed the concentration of iron, cadmium, manganese, cobalt, copper, zinc, phosphorus and carbon in baleen whale faeces and muscle, and krill tissue using inductively coupled plasma mass spectrometry. Metal concentrations in krill tissue were between 20 thousand and 4.8 million times higher than typical Southern Ocean HNLC seawater concentrations, while whale faecal matter was between 276 thousand and 10 million times higher. These findings suggest that krill act as a mechanism for concentrating and retaining elements in the surface layer, which are subsequently released back into the ocean, once eaten by whales, through defecation. Trace metal to carbon ratios were also higher in whale faeces compared to whale muscle indicating that whales are concentrating carbon and actively defecating trace elements. Consequently, recovery of the great whales may facilitate the recycling of nutrients via defecation, which may affect productivity in HNLC areas. PMID:25469984

  12. The Biogeochemical Role of Baleen Whales and Krill in Southern Ocean Nutrient Cycling

    PubMed Central

    Ratnarajah, Lavenia; Bowie, Andrew R.; Lannuzel, Delphine; Meiners, Klaus M.; Nicol, Stephen

    2014-01-01

    The availability of micronutrients is a key factor that affects primary productivity in High Nutrient Low Chlorophyll (HNLC) regions of the Southern Ocean. Nutrient supply is governed by a range of physical, chemical and biological processes, and there are significant feedbacks within the ecosystem. It has been suggested that baleen whales form a crucial part of biogeochemical cycling processes through the consumption of nutrient-rich krill and subsequent defecation, but data on their contribution are scarce. We analysed the concentration of iron, cadmium, manganese, cobalt, copper, zinc, phosphorus and carbon in baleen whale faeces and muscle, and krill tissue using inductively coupled plasma mass spectrometry. Metal concentrations in krill tissue were between 20 thousand and 4.8 million times higher than typical Southern Ocean HNLC seawater concentrations, while whale faecal matter was between 276 thousand and 10 million times higher. These findings suggest that krill act as a mechanism for concentrating and retaining elements in the surface layer, which are subsequently released back into the ocean, once eaten by whales, through defecation. Trace metal to carbon ratios were also higher in whale faeces compared to whale muscle indicating that whales are concentrating carbon and actively defecating trace elements. Consequently, recovery of the great whales may facilitate the recycling of nutrients via defecation, which may affect productivity in HNLC areas. PMID:25469984

  13. Global Biogeochemical Cycle of Si: Its Coupling to the Perturbed C-N-P cycles in Industrial Time

    NASA Astrophysics Data System (ADS)

    Lerman, A.; Li, D. D.; MacKenzie, F. T.

    2010-12-01

    The importance of silicon (Si) in global biogeochemical cycles is demonstrated by its abundance in the land and aquatic biomass, where Si/C is 0.02 in land plants and 0.15 in marine organisms. Estimates show that Si-bioproduction accounts for ~1.5% of terrestrial primary production, and ~4.5% in the coastal ocean. Human land-use activities have substantially changed regional patterns of vegetation distribution, soil conditions, and nutrient fluxes via runoff to the coastal ocean. Anthropogenic chemical fertilization of the land has caused a significant increase in fluvial nitrogen (N) and phosphorus (P) transport, whereas land-use and vegetation mass changes have caused variations in the riverine Si input, all eventually affecting the cycling of nutrients in the marine environment. We developed a global biogeochemical model of the Si cycle as coupled to the global C-N-P cycle model, TOTEM II (Terrestrial-Ocean-aTmosphere-Ecosystem-Model). In the model analysis from year 1700, taken as the start of the Anthropocene, to 2050, the bioproduction of Si on land and in the ocean is coupled to the bioproduction of C, perturbed by the atmospheric CO2 rise, land-use changes, and chemical fertilization. Also, temperature rise affects the Si cycling on land through bioproduction rates, terrestrial organic matter remineralization, and weathering, thereby affecting its delivery to the coastal zone. The results show that biouptake and subsequent release of Si on land strongly affect the Si river flux to the coastal ocean. During the 350-year period, Si river discharge has increased by ~10% until ~1940, decreasing since then to below its 1700 value and continuing to drop, under the current IPCC IS92 projections of CO2, temperature and other forcings. From 1700 to ~1950, land-use changes, associated with slash and burn of large areas of high-productivity land, caused a decrease of global land vegetation. Dissolution of Si in soil humus and weathering of silicate minerals are the

  14. Geomorphic and substrate controls on spatial variability in river solute transport and biogeochemical cycling

    NASA Astrophysics Data System (ADS)

    Blaen, Phillip; Kurz, Marie; Knapp, Julia; Mendoza-Lera, Clara; Lee-Cullin, Joe; Klaar, Megan; Drummond, Jen; Jaeger, Anna; Zarnetske, Jay; Lewandowski, Joerg; Marti, Eugenia; Ward, Adam; Fleckenstein, Jan; Datry, Thibault; Larned, Scott; Krause, Stefan

    2016-04-01

    Nutrient concentrations in surface waters and groundwaters are increasing in many agricultural catchments worldwide as a result of anthropogenic activities. Increasing geomorphological heterogeneity in river channels may help to attenuate nutrient pollution by facilitating water exchange fluxes with the hyporheic zone; a site of intense microbial activity where biogeochemical transformation rates (e.g. denitrification) can be high. However, the controls on spatial variability in biogeochemical cycling, particularly at scales relevant for river managers, are not well understood. Here, we aimed to assess: 1) how differences in geomorphological heterogeneity control river solute transport and rates of biogeochemical cycling at sub-reach scales (102 m); and 2) the relative magnitude of these differences versus those relating to reach scale substrate variability (103 m). We used the reactive 'smart' tracer resazurin (Raz), a weakly fluorescent dye that transforms to highly fluorescent resorufin (Rru) under mildly reducing conditions, as a proxy to assess rates of biogeochemical cycling in a lowland river in southern England. Solute tracer tests were conducted in two reaches with contrasting substrates: one sand-dominated and the other gravel-dominated. Each reach was divided into sub-reaches that varied in geomorphic complexity (e.g. by the presence of pool-riffle sequences or the abundance of large woody debris). Slug injections of Raz and the conservative tracer fluorescein were conducted in each reach during baseflow conditions (Q ≈ 80 L/s) and breakthrough curves monitored using in-situ fluorometers. Preliminary results indicate overall Raz:Rru transformation rates in the gravel-dominated reach were more than 50% higher than those in the sand-dominated reach. However, high sub-reach variability in Raz:Rru transformation rates and conservative solute transport parameters suggests small-scale targeted management interventions to alter geomorphic heterogeneity may be

  15. Hydrological and biogeochemical constraints on terrestrial carbon cycle projections

    NASA Astrophysics Data System (ADS)

    Mystakidis, Stefanos; Davin, Edouard L.; Gruber, Nicolas; Seneviratne, Sonia I.

    2016-04-01

    The terrestrial biosphere is currently acting as a sink for about a third of the total anthropogenic CO2 emissions. However, the future fate of this sink in the coming decades is very uncertain, as current Earth System Models (ESMs) simulate diverging responses of the terrestrial carbon cycle to upcoming climate change. Here, we use observation-based constraints of water and carbon fluxes to reduce uncertainties in the projected terrestrial carbon cycle response derived from simulations of ESMs conducted as part of the 5th phase of the Coupled Model Intercomparison Project (CMIP5). We find in the ESMs a clear linear relationship between present-day Evapotranspiration (ET) and Gross Primary Productivity (GPP), as well as between these present-day fluxes and projected changes in GPP, thus providing an emergent constraint on projected GPP. Constraining the ESMs based on their ability to simulate present-day ET and GPP leads to a substantial decrease of the projected GPP and to a ca. 50% reduction of the associated model spread in GPP by the end of the century. Given the strong correlation between projected changes in GPP and in NBP in the ESMs, applying the constraints on Net Biome Productivity (NBP) reduces the model spread in the projected land sink by more than 30% by 2100. Also, the projected decline in the land sink is at least doubled in the constrained ensembles and the probability that the terrestrial biosphere is turned into a net carbon source by the end of the century is strongly increased. Moreover, a similar strategy is used to provide constraints on the feedbacks involving the terrestrial carbon cycle and the climate system. The findings indicate that the decline in the future land carbon uptake might be stronger than previously thought, which would have important implications for the rate of increase of the atmospheric CO2 concentration and for future climate change.

  16. The biogeochemical cycling of elemental mercury: Anthropogenic influences

    SciTech Connect

    Mason, R.P.; Morel, F.M.M. ); Fitzgerald, W.F. )

    1994-08-01

    A review of the available information on global Hg cycling shows that the atmosphere and surface ocean are in rapid equilibrium; the evasion of Hg[sup 0] from the oceans is balanced by the total oceanic deposition of Hg(II) from the atmosphere. The mechanisms whereby reactive Hg species are reduced to volatile Hg[sup 0] in the oceans are poorly known, but reduction appears to be chiefly biological. The rapid equilibrium of the surface oceans and the atmosphere, coupled with the small Hg sedimentation in the oceans makes deposition on land the dominant sink for atmospheric Hg. About half of the anthropogenic emissions appear to enter the global atmospheric cycle while the other half is deposited locally, presumably due to the presence of reactive Hg in flue gases. The authors estimate that over the last century anthropogenic emissions have tripled the concentrations of Hg in the atmosphere and in the surface ocean. Thus, two-thirds of the present Hg fluxes (such as deposition on land and on the ocean) are directly or indirectly of anthropogenic origin. Elimination of the anthropogenic load in the ocean and atmosphere would take fifteen to twenty years after termination of all anthropogenic emissions.

  17. Late Archean Euxinia as a Window into Early Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Scott, C.; Bekker, A.; Reinhard, C.; Lyons, T. W.

    2009-12-01

    A number of transition metals present in seawater in trace amounts (10-10 to 10-7 moles/L) are nevertheless bioessential micronutrients, utilized in a wide range of cellular activities. Because their abundances in seawater are largely a reflection of redox-controlled sources and sinks, Precambrian biogeochemists increasingly focus on the interrelated nature of major redox transitions, the chemical composition of the oceans, and the evolution of life on Earth. Of particular interest are temporal trends in seawater inventories of elements utilized in the nitrogen cycle, both nitrogen fixation (Fe, V, Mo) and denitrification (Cu). Recent work on the link between trace metal abundance and the biologically mediated nitrogen cycle has focused on the Proterozoic Eon, when oxidative weathering was well established and sulfidic conditions were common in the deep ocean. However, we know little about trace metal availability during the Archean Eon, when oxygenic photosynthesis first appeared on Earth and began to alter the chemical composition of the oceans and atmosphere. The development of euxinic conditions, or anoxic and sulfidic bottom waters, provides important information regarding the cycling of major elements such as C, S and Fe. However, euxinic black shales can also provide a record of trace metal abundance. Mo is highly enriched in these shales and displays a conspicuous covariation with the concentration of total organic carbon (TOC). Furthermore, it has been demonstrated that the ratio Mo/TOC is proportional to the concentration of Mo in seawater. Cu and V are also enriched in euxinic black shales, and both correlate with TOC. By analogy with Mo, it is likely that the ratios Cu/TOC and V/TOC also contain information on the concentration of these transition metals in seawater. Here we present C-S-Fe systematics as well as trace metal concentrations from black shales of the Roy Hill Member of the late Archean Jeerinah Formation. Fe speciation indicates that the

  18. The Thermodynamics of Marine Biogeochemical Cycles: Lotka Revisited

    NASA Astrophysics Data System (ADS)

    Vallino, Joseph J.; Algar, Christopher K.

    2016-01-01

    Nearly 100 years ago, Alfred Lotka published two short but insightful papers describing how ecosystems may organize. Principally, Lotka argued that ecosystems will grow in size and that their cycles will spin faster via predation and nutrient recycling so as to capture all available energy, and that evolution and natural selection are the mechanisms by which this occurs and progresses. Lotka's ideas have often been associated with the maximum power principle, but they are more consistent with recent developments in nonequilibrium thermodynamics, which assert that complex systems will organize toward maximum entropy production (MEP). In this review, we explore Lotka's hypothesis within the context of the MEP principle, as well as how this principle can be used to improve marine biogeochemistry models. We need to develop the equivalent of a climate model, as opposed to a weather model, to understand marine biogeochemistry on longer timescales, and adoption of the MEP principle can help create such models.

  19. Biogeochemical cycling in the ocean. Part 1: Introduction to the effects of upwelling along the west coast of North America

    NASA Technical Reports Server (NTRS)

    Howe, John T.

    1986-01-01

    Coastal upwelling is examined as it relates to the cycling of chemical species in coastal waters along the west coast of North America. The temporal and spatial features of upwelling phenomena in the Eastern boundary regions of the North Pacific Ocean are presented and discussed in terms of upwelling episodes. Climate conditions affecting upwelling include: thermal effects, wind-induced shear stress which moves surface layers, and the curl of the wind stress vector which is thought to affect the extent and nature of upwelling and the formation of offshore convergent downwelling fronts. These effects and the interaction of sunlight and upwelled nutrients which result in a biological bloom in surface waters is modeled analytically. The roles of biological and chemical species, including the effects of predation, are discussed in that context, and relevant remote sensing and in situ observations are presented. Climatological, oceanographic, biological, physical, chemical events, and processes that pertain to biogeochemical cycling are presented and described by a set of partial differential equations. Simple preliminary results are obtained and are compared with data. Thus a fairly general framework has been laid where the many facets of biogeochemical cycling in coastal upwelled waters can be examined in their relationship to one another, and to the whole, to whatever level of detail or approximation is warranted or desired.

  20. Biogeochemical factors affecting the presence of 210Po in groundwater

    USGS Publications Warehouse

    Seiler, R.L.; Stillings, L.L.; Cutler, N.; Salonen, L.; Outola, I.

    2011-01-01

    The discovery of natural 210Po enrichment at levels exceeding 500 mBq/L in numerous domestic wells in northern Nevada, USA, led to a geochemical investigation of the processes responsible for its mobilization. 210Po activities in 63 domestic and public-supply wells ranged from below 1 mBq/L to 6590 ± 590 mBq/L, among the highest reported levels in the USA. There is little spatial or depth variability in 210Pb activity in study-area sediments and mobilization of a few percent of the 210Po in the sediments would account for all of the 210Po in water. Stable-isotope measurements indicate SO4 reduction has occurred in all 210Po contaminated wells. Sulfide species are not accumulating in the groundwater in much of Lahontan Valley, probably because of S cycling involving microbial SO4 reduction, abiotic oxidation of H2S to S0 by Mn(IV), followed by microbial disproportionation of S0 to H2S and SO4. The high pH, Ca depletion, MnCO3 saturation, and presence of S0 in Lahontan Valley groundwater may be consequences of the anaerobic S cycling. Consistent with data from naturally-enriched wells in Florida, 210Po activities begin to decrease when aqueous sulfide species begin to accumulate. This may be due to formation and precipitation of PoS, however, Eh–pH diagrams suggest PoS would not be stable in study-area groundwater. An alternative explanation for the study area is that H2S accumulation begins when anaerobic S cycling stops because Mn oxides are depleted and their reduction is no longer releasing 210Po. Common features of 210Po-enriched groundwater were identified by comparing the radiological and geochemical data from Nevada with data from naturally-enriched wells in Finland, and Florida and Maryland in the USA. Values of pH ranged from 9 in Nevada wells, indicating that pH is not critical in determining whether 210Po is present. Where U is present in the sediments, the data suggest 210Po levels may be elevated in aquifers with (1) SO4-reducing waters with low H2S

  1. Biogeochemical processes driving mercury cycling in estuarine ecosystems

    NASA Astrophysics Data System (ADS)

    Schartup, A. T.

    2015-12-01

    Mercury (Hg) is a naturally occurring element that has been enriched in the environment through human activities, particularly in the coastal zone. Bioaccumulation of methylmercury (MeHg) in marine fishposes health risks for fish-consuming populations and is a worldwide health concern. A broader understanding of major environmental processes controlling Hg cycling and MeHg production and bioaccumulation in estuaries is therefore needed. Recent fieldwork and modeling show diverse sources of MeHg production in estuaries. We present geochemical modeling results for Hg and MeHg acrossmultiple estuaries with contrasting physical, chemical and biological characteristics. We report new measurements of water column and sediment mercury speciation and methylation data from the subarctic (Lake Melville, Labrador Canada) and temperate latitudes (Long Island Sound, Delaware Bay, Chesapeake Bay). We find that benthic sediment is a relatively small source of MeHg to the water column in all systems. Water column methylation drives MeHg levels in Lake Melville, whereas in more impacted shallow systems such as Chesapeake Bay and Long Island Sound, external inputs and sediment resuspension are more dominant. All systems are a net source of MeHg to the ocean through tidal exchange. In light of these inter-system differences, we will evaluate timescales of coastal ecosystem responses to changes in Hg loading that can help predict potential responses to future perturbations.

  2. Environmental Assessment for Potential Impacts of Ocean CO2 Storage on Marine Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Yamada, N.; Tsurushima, N.; Suzumura, M.; Shibamoto, Y.; Harada, K.

    2008-12-01

    Ocean CO2 storage that actively utilizes the ocean potential to dissolve extremely large amounts of CO2 is a useful option with the intent of diminishing atmospheric CO2 concentration. CO2 storage into sub-seabed geological formations is also considered as the option which has been already put to practical reconnaissance in some projects. Direct release of CO2 in the ocean storage and potential CO2 leakage from geological formations into the bottom water can alter carbonate system as well as pH of seawater. It is essential to examine to what direction and extent chemistry change of seawater induced by CO2 can affect the marine environments. Previous studies have shown direct and acute effects by increasing CO2 concentrations on physiology of marine organisms. It is also a serious concern that chemistry change can affect the rates of chemical, biochemical and microbial processes in seawater resulting in significant influences on marine biogeochemical cycles of the bioelements including carbon, nutrients and trace metals. We, AIST, have conducted a series of basic researches to assess the potential impacts of ocean CO2 storage on marine biogeochemical processes including CaCO3 dissolution, and bacterial and enzymatic decomposition of organic matter. By laboratory experiments using a special high pressure apparatus, the improved empirical equation was obtained for CaCO3 dissolution rate in the high CO2 concentrations. Based on the experimentally obtained kinetics with a numerical simulation for a practical scenario of oceanic CO2 sequestration where 50 Mton CO2 per year is continuously injected to 1,000-2,500 m depth within 100 x 333 km area for 30 years, we could illustrate precise 3-D maps for the predicted distributions of the saturation depth of CaCO3, in situ Ω value and CaCO3 dissolution rate in the western North Pacific. The result showed no significant change in the bathypelagic CaCO3 flux due to chemistry change induced by ocean CO2 sequestration. Both

  3. Evaluation of Boundless Biogeochemical Cycle through Development of Process-Based Eco-Hydrological and Biogeochemical Cycle Model to Incorporate Terrestrial-Aquatic Continuum

    NASA Astrophysics Data System (ADS)

    Nakayama, T.; Maksyutov, S. S.

    2014-12-01

    Inland water might act as important transport pathway for continental biogeochemical cycle although its contribution has remained uncertain yet due to a paucity of data (Battin et al. 2009). The author has developed process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a-b, 2010, 2011a-b, 2012a-c, 2013; Nakayama and Fujita, 2010; Nakayama and Hashimoto, 2011; Nakayama and Shankman, 2013a-b; Nakayama and Watanabe, 2004, 2006, 2008a-b; Nakayama et al., 2006, 2007, 2010, 2012), which incorporates surface-groundwater interactions, includes up- and down-scaling processes between local-regional-global scales, and can simulate iteratively nonlinear feedback between hydrologic-geomorphic-ecological processes. Because NICE incorporates 3-D groundwater sub-model and expands from previous 1- or 2-D or steady state, the model can simulate the lateral transport pronounced at steeper-slope or riparian/floodplain with surface-groundwater connectivity. River discharge and groundwater level simulated by NICE agreed reasonably with those in previous researches (Niu et al., 2007; Fan et al., 2013) and extended to clarify lateral subsurface also has important role on global hydrologic cycle (Nakayama, 2011b; Nakayama and Shankman, 2013b) though the resolution was coarser. NICE was further developed to incorporate biogeochemical cycle including reaction between inorganic and organic carbons in terrestrial and aquatic ecosystems. The missing role of carbon cycle simulated by NICE, for example, CO2 evasion from inland water (global total flux was estimated as about 1.0 PgC/yr), was relatively in good agreement in that estimated by empirical relation using previous pCO2 data (Aufdenkampe et al., 2011; Laruelle et al., 2013). The model would play important role in identification of greenhouse gas balance of the biosphere and spatio-temporal hot spots, and bridging gap between top-down and bottom-up approaches (Cole et al. 2007; Frei et al. 2012).

  4. Biogeochemical modeling of phosphorus cycling in the ocean: response to long-term perturbations

    NASA Astrophysics Data System (ADS)

    Palastanga, Virginia; Slomp, Caroline; Heinze, Christoph; Winguth, Arne

    2010-05-01

    Phosphorus (P) is likely the limiting nutrient for marine primary productivity on geological time scales. Therefore, insight into the mechanisms that control P cycling and burial in marine sediments is of importance for our understanding of global biogeochemical cycling and climate. Here, we use a version of the Hamburg Oceanic Carbon Cycle biogeochemical ocean model (HAMOCC2) expanded with the sedimentary P cycle, i.e. burial of organic P and formation and burial of Fe-oxide bound P and authigenic Ca-P minerals. We also include anaerobic degradation of organic matter in the sediment and a description of the oceanic Fe cycle which takes into account aeolian input and scavenging of iron onto sinking particles. For present-day climate forcing, the model predictions for the solid forms of sediment P and benthic P fluxes are compared to observations from global surface sediments. In a sensitivity study, the relationships between primary productivity, nutrient cycling, and organic C and P burial are analyzed for scenarios of increased input of P from rivers as well as for changes in aeolian deposition and circulation forcing that represent Last Glacial Maximum conditions.

  5. Affective cycling in thyroid disease

    SciTech Connect

    Tapp, A.

    1988-05-01

    Depression in an elderly man with primary recurrent unipolar depression responded to radioactive iodine treatment of a thyrotoxic nodule, without the addition of psychotropic medications. Two months later, manic symptoms developed concomitant with the termination of the hyperthyroid state secondary to the radioactive iodine treatment. Clinical implications of these findings in relation to the possible mechanism of action of thyroid hormones on affective cycling are discussed.

  6. Biogeochemical factors affecting mercury methylation rate in two contaminated floodplain soils

    NASA Astrophysics Data System (ADS)

    Frohne, T.; Rinklebe, J.; Langer, U.; Du Laing, G.; Mothes, S.; Wennrich, R.

    2012-01-01

    An automated biogeochemical microcosm system allowing controlled variation of redox potential (EH) in soil suspensions was used to assess the effect of various factors on the mobility of mercury (Hg) as well as on the methylation of Hg in two contaminated floodplain soils with different Hg concentrations (approximately 5 mg Hg kg-1 and >30 mg Hg kg-1). The experiment was conducted under stepwise variation from reducing (approximately -350 mV at pH 5) to oxidizing conditions (approximately 600 mV at pH 5). Results of phospholipid fatty acids (PLFA) analysis indicate the occurrence of sulfate reducing bacteria (SRB) such as Desulfobacter species (10Me16:0, cy17:0, 10Me18:0, cy19:0) or Desulfovibrio species (18:2ω6,9), which are considered to promote Hg methylation. The products of the methylation process are lipophilic, highly toxic methyl mercury species such as the monomethyl mercury ion [MeHg+], which is named as MeHg here. The ln(MeHg/Hgt) ratio is assumed to reflect the net production of monomethyl mercury normalized to total dissolved Hg (Hgt) concentration. This ratio increases with rising dissolved organic carbon (DOC) to Hgt ratio (ln(DOC/Hgt) ratio) (R2 = 0.39, p<0.0001, n= 63) whereas the relation between ln(MeHg/Hgt ratio and lnDOC is weaker (R2 = 0.09; p<0.05; n = 63). In conclusion, the DOC/Hgt ratio might be a more important factor for the Hg net methylation than DOC alone in the current study. Redox variations seem to affect the biogeochemical behavior of dissolved inorganic Hg species and MeHg indirectly through related changes in DOC, sulfur cycle, and microbial community structure whereas EH and pH values, as well as concentration of dissolved Fe3+/Fe2+ and Cl- seem to play subordinate roles in Hg mobilization and methylation under our experimental conditions.

  7. Biogeochemical factors affecting mercury methylation rate in two contaminated floodplain soils

    NASA Astrophysics Data System (ADS)

    Frohne, T.; Rinklebe, J.; Langer, U.; Du Laing, G.; Mothes, S.; Wennrich, R.

    2011-09-01

    An automated biogeochemical microcosm system allowing controlled variation of redox potential (EH) in soil suspensions was used to assess the effect of various factors on the mobility of mercury (Hg) as well as on the methylation of Hg in two contaminated floodplain soils with different Hg concentrations (approximately 5 mg kg-1 Hg and >30 mg kg-1 Hg). The experiment was conducted under stepwise variation from reducing (approximately -350 mV at pH 5) to oxidizing conditions (approximately 600 mV at pH 5). Results of phospholipid fatty acids (PLFA) analysis indicate the occurrence of sulfate reducing bacteria (SRB) such as Desulfobacter species (10me16:0, cy17:0, 10me18:0, cy19:0) or Desulfovibrio species (18:2ω6,9), which are considered to promote Hg methylation. The products of the methylation process are lipophilic, highly toxic methyl mercury species such as the monomethyl mercury ion [MeHg+], which is named as MeHg here. The ln(MeHg/Hgt) ratio is assumed to reflect the net production of monomethyl mercury normalized to total dissolved Hg (Hgt) concentration. This ratio increases with rising dissolved organic carbon (DOC) to Hgt ratio (lnDOC/lnHgt ratio) (R2 = 0.39, p < 0.0001, n = 63) whereas the relation between ln(MeHg/Hgt) ratio and lnDOC is weaker (R2 = 0.09; p < 0.05; n = 63). In conclusion, the DOC/Hgt ratio might be a more important factor for the Hg net methylation than DOC alone in the current study. Redox variations seem to affect the biogeochemical behavior of dissolved inorganic Hg species and MeHg indirectly through related changes in DOC, sulfur cycle, and microbial community structure whereas E,H and pH values, as well as concentration of dissolved Fe,3+/Fe2+ and Cl- seem to play subordinate roles in Hg mobilization and methylation under our experimental conditions.

  8. Top-down constraints on atmospheric mercury emissions and implications for global biogeochemical cycling

    NASA Astrophysics Data System (ADS)

    Song, S.; Selin, N. E.; Soerensen, A. L.; Angot, H.; Artz, R.; Brooks, S.; Brunke, E.-G.; Conley, G.; Dommergue, A.; Ebinghaus, R.; Holsen, T. M.; Jaffe, D. A.; Kang, S.; Kelley, P.; Luke, W. T.; Magand, O.; Marumoto, K.; Pfaffhuber, K. A.; Ren, X.; Sheu, G.-R.; Slemr, F.; Warneke, T.; Weigelt, A.; Weiss-Penzias, P.; Wip, D. C.; Zhang, Q.

    2015-02-01

    We perform global-scale inverse modeling to constrain present-day atmospheric mercury emissions and relevant physio-chemical parameters in the GEOS-Chem chemical transport model. We use Bayesian inversion methods combining simulations with GEOS-Chem and ground-based Hg0 observations from regional monitoring networks and individual sites in recent years. Using optimized emissions/parameters, GEOS-Chem better reproduces these ground-based observations, and also matches regional over-water Hg0 and wet deposition measurements. The optimized global mercury emission to the atmosphere is ~5.8 Gg yr-1. The ocean accounts for 3.2 Gg yr-1 (55% of the total), and the terrestrial ecosystem is neither a net source nor a net sink of Hg0. The optimized Asian anthropogenic emission of Hg0 (gas elemental mercury) is 650-1770 Mg yr-1, higher than its bottom-up estimates (550-800 Mg yr-1). The ocean parameter inversions suggest that dark oxidation of aqueous elemental mercury is faster, and less mercury is removed from the mixed layer through particle sinking, when compared with current simulations. Parameter changes affect the simulated global ocean mercury budget, particularly mass exchange between the mixed layer and subsurface waters. Based on our inversion results, we re-evaluate the long-term global biogeochemical cycle of mercury, and show that legacy mercury becomes more likely to reside in the terrestrial ecosystem than in the ocean. We estimate that primary anthropogenic mercury contributes up to 23% of present-day atmospheric deposition.

  9. Top-down constraints on atmospheric mercury emissions and implications for global biogeochemical cycling

    NASA Astrophysics Data System (ADS)

    Song, S.; Selin, N. E.; Soerensen, A. L.; Angot, H.; Artz, R.; Brooks, S.; Brunke, E.-G.; Conley, G.; Dommergue, A.; Ebinghaus, R.; Holsen, T. M.; Jaffe, D. A.; Kang, S.; Kelley, P.; Luke, W. T.; Magand, O.; Marumoto, K.; Pfaffhuber, K. A.; Ren, X.; Sheu, G.-R.; Slemr, F.; Warneke, T.; Weigelt, A.; Weiss-Penzias, P.; Wip, D. C.; Zhang, Q.

    2015-06-01

    We perform global-scale inverse modeling to constrain present-day atmospheric mercury emissions and relevant physiochemical parameters in the GEOS-Chem chemical transport model. We use Bayesian inversion methods combining simulations with GEOS-Chem and ground-based Hg0 observations from regional monitoring networks and individual sites in recent years. Using optimized emissions/parameters, GEOS-Chem better reproduces these ground-based observations and also matches regional over-water Hg0 and wet deposition measurements. The optimized global mercury emission to the atmosphere is ~ 5.8 Gg yr-1. The ocean accounts for 3.2 Gg yr-1 (55 % of the total), and the terrestrial ecosystem is neither a net source nor a net sink of Hg0. The optimized Asian anthropogenic emission of Hg0 (gas elemental mercury) is 650-1770 Mg yr-1, higher than its bottom-up estimates (550-800 Mg yr-1). The ocean parameter inversions suggest that dark oxidation of aqueous elemental mercury is faster, and less mercury is removed from the mixed layer through particle sinking, when compared with current simulations. Parameter changes affect the simulated global ocean mercury budget, particularly mass exchange between the mixed layer and subsurface waters. Based on our inversion results, we re-evaluate the long-term global biogeochemical cycle of mercury, and show that legacy mercury becomes more likely to reside in the terrestrial ecosystem than in the ocean. We estimate that primary anthropogenic mercury contributes up to 23 % of present-day atmospheric deposition.

  10. Influence of biological soil crusts at different successional stages in the implantation of biogeochemical cycles in arid and semiarid zones

    NASA Astrophysics Data System (ADS)

    Gil-Sotres, F.; Miralles, I.; Canton-Castilla, Y.; Domingo, F.; Leiros, M. C.; Trasar-Cepeda, C.

    2012-04-01

    Influence of biological soil crusts at different successional stages in the implantation of biogeochemical cycles in arid and semiarid zones I. Miralles1, F. Gil-Sotres2, Y. Cantón-Castilla3, F. Domingo1, M.C. Leirós2, C. Trasar-Cepeda4 1 Experimental Estation of Arid Zones (CSIC), E-04230 La Cañada de San Urbano, Almería, Spain. 2 Departamento Edafología y Química Agrícola, Grupo de Evaluación de la Calidad del Suelo, Unidad Asociada CSIC, Facultad de Farmacia, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain. 3 University of Almería, Departamento de Edafología y Química Agrícola, E-04230-La Cañada de San Urbano, Almería, Spain. 4 Departamento Bioquímica del Suelo, IIAG-CSIC, Apartado 122, E-15708 Santiago de Compostela, Spain. Crusts (BSCs) are formed by a close association between soil particles and cyanobacteria, algae, lichens, bryophytes and microfungi in varying proportions. Their habitat is within or immediately on top of the uppermost millimetres of the soil and are the predominant surface cover in arid and semiarid zones. Among the diverse functions developed by BSCs in the ecosystem (hydrology, erosion, soil properties, etc.), one of the most important is its role in nutrient cycling. Within arid and semiarid environments, BSCs have been termed 'mantles of fertility' being considered hotspots of biogeochemical inputs, fixing C, N and P above- and below-ground. However, there are differences in N and C fixation rates between BSCs types. Early successional BSCs, dominated by cyanobacterial species, fix lower quantities of C and N than mature BSCs dominated by lichens. Although the positive effects of BSCs on biogeochemical soil cycles are widely accepted, no previous studies have evaluated the activities of the enzymes involved in C, N and P cycles of BSCs and how they are affected by the successional stage of the BSC. In this work, performed in the Tabernas desert (SE Spain), we studied the hydrolase enzymes

  11. The biogeochemical cycle of the adsorbed template. I - formation of the template

    NASA Technical Reports Server (NTRS)

    Lazard, Daniel; Lahav, Noam; Orenberg, J. B.

    1987-01-01

    Experimental results are presented for the verification of the first adsorption step of the 'adsorbed template' biogeochemical cycle, a simple model for a primitive prebiotic replication system. The adsorption of Poly-C, Poly-U, Poly-A, Poly-G, and 5'-AMP, 5'-GMP, 5'-CMP and 5'-UMP onto gypsum was studied. It was found that under the conditions of the experiment, the polymers have a very high affinity for the mineral surface, while the monomers adsorb much less efficiently.

  12. The biogeochemical cycle of the adsorbed template. II - Selective adsorption of mononucleotides on adsorbed polynucleotide templates

    NASA Technical Reports Server (NTRS)

    Lazard, Daniel; Lahav, Noam; Orenberg, James B.

    1988-01-01

    Experimental results are presented for the verification of the specific interaction step of the 'adsorbed template' biogeochemical cycle, a simple model for a primitive prebiotic replication system. The experimental system consisted of gypsum as the mineral to which an oligonucleotide template attaches (Poly-C or Poly-U) and (5-prime)-AMP, (5-prime)-GMP, (5-prime)-CMP and (5-prime)-UMP as the interacting biomonomers. When Poly-C or Poly-U were used as adsorbed templates, (5-prime)-GMP and (5-prime)-AMP, respectively, were observed to be the most strongly adsorbed species.

  13. Interdisciplinary research in global biogeochemical cycling Nitrous oxide in terrestrial ecosystems

    NASA Technical Reports Server (NTRS)

    Norman, S. D.; Peterson, D. L.

    1984-01-01

    NASA has begun an interdisciplinary research program to investigate various aspects of Global Biology and Global Habitability. An important element selected for the study of global phenomena is related to biogeochemical cycling. The studies involve a collaboration with recognized scientists in the areas of plant physiology, microbiology, nutrient cycling theory, and related areas. Selected subjects of study include nitrogen cycling dynamics in terrestrial ecosystems with special attention to biosphere/atmosphere interactions, and an identification of sensitive response variables which can be used in ecosystem models based on parameters derived from remotely sensed variables. A description is provided of the progress and findings over the past two years. Attention is given to the characteristics of nitrous oxide emissions, the approach followed in the investigations, the selection of study sites, radiometric measurements, and research in Sequoia.

  14. Abrupt shifts in ecosystem function and intensification of global biogeochemical cycle driven by hydroclimatic extremes

    NASA Astrophysics Data System (ADS)

    Ma, Xuanlong; Huete, Alfredo; Ponce-Campos, Guillermo; Zhang, Yongguang; Xie, Zunyi; Giovannini, Leandro; Cleverly, James; Eamus, Derek

    2016-04-01

    Amplification of the hydrologic cycle as a consequence of global warming is increasing the frequency, intensity, and spatial extent of extreme climate events globally. The potential influences resulting from amplification of the hydro-climatic cycle, coupled with an accelerating warming trend, pose great concerns on the sustainability of terrestrial ecosystems to sequester carbon, maintain biodiversity, provide ecosystem services, food security, and support human livelihood. Despite the great implications, the magnitude, direction, and carry-over effect of these extreme climate events on ecosystem function, remain largely uncertain. To address these pressing issues, we conducted an observational, interdisciplinary study using satellite retrievals of atmospheric CO2 and photosynthesis (chlorophyll fluorescence), and in-situ flux tower measures of ecosystem-atmosphere carbon exchange, to reveal the shifts in ecosystem function across extreme drought and wet periods. We further determine the factors that govern ecosystem sensitivity to hydroclimatic extremes. We focus on Australia but extended our analyses to other global dryland regions due to their significant role in global biogeochemical cycles. Our results revealed dramatic impacts of drought and wet hydroclimatic extremes on ecosystem function, with abrupt changes in vegetation productivity, carbon uptake, and water-use-efficiency between years. Drought resulted in widespread reductions or collapse in the normal patterns of vegetation growth seasonality such that in many cases there was no detectable phenological cycle during extreme drought years. We further identified a significant increasing trend (p < 0.001) in extreme wet year precipitation amounts over Australia and many other global regions, resulting in an increasing trend in magnitude of the episodic carbon sink pulses coupled to each La Niña-induced wet years. This finding is of global biogeochemical significance, with the consequence of amplifying

  15. Scale dependent importance of spatial heterogeneity in biogeochemical cycling at aquifer-river interfaces

    NASA Astrophysics Data System (ADS)

    Krause, Stefan; Blaen, Phillip; Hannah, David; Romejn, Paul; Gomez, Jesus; Kurz, Marie; Fleckenstein, Jan; Schmidt, Christian; Zarnetske, Jay; Cullin, Joe; Ward, Adam; Marti, Eugenia; Drummond, Jennifer; Schmadel, Noah; Knapp, Julia; Klaar, Megan; Mendoza, Clara

    2016-04-01

    The transport and transformation of carbon and nitrogen across aquifer - river interfaces are significantly altered along the streambed passage. Recent investigations have substantially improved the understanding of controls on streambed biogeochemical cycling, outlining a critical impact of exchange fluxes, temporal and spatial coincidence of reaction partners and streambed residence time distributions. Still, there is little understanding of the drivers of the widely observed strong spatial and temporal variability of interlinked carbon and nitrogen turnover at aquifer-river interfaces, including hotspots (locations) and hot moments (time periods) of increased reactivity. Previous research, predominantly with a surface water perspective, has mainly focused on the impact of bedform controlled hyporheic exchange fluxes and the chemical transformation of surface solutes transported along a hyporheic flow path. While such studies may explain nutrient turnover in the hyporheic zones of low-order streams in rather pristine headwater catchments, they fail to explain observations of spatially and temporally more variable nutrient turnover in streambeds with higher structural heterogeneity and relevant concentrations of autochthonous carbon and nitrogen. Here we combine laboratory, field and numerical modeling experiments from plot to stream reach/subcatchment scales to quantify the impacts of variability in physical and biogeochemical streambed properties on hyporheic nutrient (C, N, O) cycling. At the plot scale, hotspots of biogeochemical cycling have been found to be associated with peat and clay layers within streambed sediments, representing areas of significantly increased residence times and oxygen consumption what results in enhanced microbial metabolic activity and nitrogen removal capacity. We present distributed sensor network based up-scaling methods that allow identification of such features at larger reach scale. Numerical modeling based generalization

  16. The role of airborne volcanic ash for the surface ocean biogeochemical iron-cycle: a review

    NASA Astrophysics Data System (ADS)

    Duggen, S.; Olgun, N.; Croot, P.; Hoffmann, L.; Dietze, H.; Teschner, C.

    2009-07-01

    Iron is a key micronutrient for phytoplankton growth in the surface ocean. Yet the significance of volcanism for the marine biogeochemical iron-cycle is poorly constrained. Recent studies, however, suggest that offshore deposition of airborne ash from volcanic eruptions is a way to inject significant amounts of bio-available iron into the surface ocean. Volcanic ash may be transported up to several tens of kilometres high into the atmosphere during large-scale eruptions and fine ash may encircle the globe for years, thereby reaching even the remotest and most iron-starved oceanic areas. Scientific ocean drilling demonstrates that volcanic ash layers and dispersed ash particles are frequently found in marine sediments and that therefore volcanic ash deposition and iron-injection into the oceans took place throughout much of the Earth's history. The data from geochemical and biological experiments, natural evidence and satellite techniques now available suggest that volcanic ash is a so far underestimated source for iron in the surface ocean, possibly of similar importance as aeolian dust. Here we summarise the development of and the knowledge in this fairly young research field. The paper covers a wide range of chemical and biological issues and we make recommendations for future directions in these areas. The review paper may thus be helpful to improve our understanding of the role of volcanic ash for the marine biogeochemical iron-cycle, marine primary productivity and the ocean-atmosphere exchange of CO2 and other gases relevant for climate throughout the Earth's history.

  17. Biogeochemical cycles and biodiversity as key drivers of ecosystem services provided by soils

    NASA Astrophysics Data System (ADS)

    Smith, P.; Cotrufo, M. F.; Rumpel, C.; Paustian, K.; Kuikman, P. J.; Elliott, J. A.; McDowell, R.; Griffiths, R. I.; Asakawa, S.; Bustamante, M.; House, J. I.; Sobocká, J.; Harper, R.; Pan, G.; West, P. C.; Gerber, J. S.; Clark, J. M.; Adhya, T.; Scholes, R. J.; Scholes, M. C.

    2015-06-01

    Soils play a pivotal role in major global biogeochemical cycles (carbon, nutrient and water), while hosting the largest diversity of organisms on land. Because of this, soils deliver fundamental ecosystem services, and management to change a soil process in support of one ecosystem service can either provide co-benefits to other services or can result in trade-offs. In this critical review, we report the state-of-the-art understanding concerning the biogeochemical cycles and biodiversity in soil, and relate these to the provisioning, regulating, supporting and cultural ecosystem services which they underpin. We then outline key knowledge gaps and research challenges, before providing recommendations for management activities to support the continued delivery of ecosystem services from soils. We conclude that although there are knowledge gaps that require further research, enough is known to start improving soils globally. The main challenge is in finding ways to share knowledge with soil managers and policy-makers, so that best-practice management can be implemented. A key element of this knowledge sharing must be in raising awareness of the multiple ecosystem services underpinned by soils, and the natural capital they provide. The International Year of Soils in 2015 presents the perfect opportunity to begin a step-change in how we harness scientific knowledge to bring about more sustainable use of soils for a secure global society.

  18. Microbial mediation of biogeochemical cycles revealed by simulation of global changes with soil transplant and cropping

    PubMed Central

    Zhao, Mengxin; Xue, Kai; Wang, Feng; Liu, Shanshan; Bai, Shijie; Sun, Bo; Zhou, Jizhong; Yang, Yunfeng

    2014-01-01

    Despite microbes' key roles in driving biogeochemical cycles, the mechanism of microbe-mediated feedbacks to global changes remains elusive. Recently, soil transplant has been successfully established as a proxy to simulate climate changes, as the current trend of global warming coherently causes range shifts toward higher latitudes. Four years after southward soil transplant over large transects in China, we found that microbial functional diversity was increased, in addition to concurrent changes in microbial biomass, soil nutrient content and functional processes involved in the nitrogen cycle. However, soil transplant effects could be overridden by maize cropping, which was attributed to a negative interaction. Strikingly, abundances of nitrogen and carbon cycle genes were increased by these field experiments simulating global change, coinciding with higher soil nitrification potential and carbon dioxide (CO2) efflux. Further investigation revealed strong correlations between carbon cycle genes and CO2 efflux in bare soil but not cropped soil, and between nitrogen cycle genes and nitrification. These findings suggest that changes of soil carbon and nitrogen cycles by soil transplant and cropping were predictable by measuring microbial functional potentials, contributing to a better mechanistic understanding of these soil functional processes and suggesting a potential to incorporate microbial communities in greenhouse gas emission modeling. PMID:24694714

  19. Ocean viruses and their effects on microbial communities and biogeochemical cycles

    PubMed Central

    Wilhelm, Steven W.

    2012-01-01

    Viruses are the most abundant life forms on Earth, with an estimated 1031 total viruses globally. The majority of these viruses infect microbes, whether bacteria, archaea or microeukaryotes. Given the importance of microbes in driving global biogeochemical cycles, it would seem, based on numerical abundances alone, that viruses also play an important role in the global cycling of carbon and nutrients. However, the importance of viruses in controlling host populations and ecosystem functions, such as the regeneration, storage and export of carbon and other nutrients, remains unresolved. Here, we report on advances in the study of ecological effects of viruses of microbes. In doing so, we focus on an area of increasing importance: the role that ocean viruses play in shaping microbial population sizes as well as in regenerating carbon and other nutrients. PMID:22991582

  20. Biogeochemical cycling and ecosystem dynamics during strong El Niño events

    NASA Astrophysics Data System (ADS)

    Turk, D.

    2015-12-01

    El Niño events are known to induce substantial variability in carbon cycle, biological production and ecosystem structure and metabolism in the tropical Pacific and globally. The magnitude and spatial extend of this variability strongly depends on the intensity as well as type of event. Understanding and predicting biological processes are hampered because the existing in situ observing system focuses primarily on physical measurements and does not observe key biological parameters. The 1997-98 El Niño, by some measures was the strongest on record and resulted in drastic effect on heat, carbon and nutrient dynamics as well as biological production in tropical Pacific. Here, we compare current El Niño conditions during 2015 to 1997-98 event and explore the implications for biogeochemical cycling and ecosystem dynamics.

  1. Biogeochemical Cycling and Environmental Stability of Pu Relevant to Long-Term Stewardship of DOE Sites

    SciTech Connect

    Honeyman, Bruce D.; Francis, A.J.; Gillow, Jeffrey B.; Dodge, Cleveland J.; Santschi, Peter H.; Chin-Chang Hung; Diaz, Angelique; Tinnacher, Ruth; Roberts, Kimberly; Schwehr, Kathy

    2006-04-05

    The overall objective of this research is to understand the biogeochemical cycling of Pu in environments of interest to long-term DOE stewardship issues. Central to Pu cycling (transport initiation and immobilization) is the role of microorganisms. The hypothesis underlying this work is that microbial activity is the causative agent in initiating the mobilization of Pu in near-surface environments: through the transformation of Pu associated with solid phases, production of extracellular polymeric substances (EPS) carrier phases and the creation of microenvironments. Also, microbial processes are central to the immobilization of Pu species, through the metabolism of organically complexed Pu species and Pu associated with extracellular carrier phases and the creation of environments favorable for Pu transport retardation.

  2. Biogeochemical Cycling and Environmental Stability of Pu Relevant to Long-Term Stewardship of DOE Sites

    SciTech Connect

    Francis, Arokiasamy J.; Santschi, Peter H.; Honeyman, Bruce D.

    2005-06-01

    The overall objective of this proposed research is to understand the biogeochemical cycling of Pu in environments of interest to long-term DOE stewardship issues. Central to Pu cycling (transport initiation to immobilization) is the role of microorganisms. The hypothesis underlying this proposal is that microbial activity is the causative agent in initiating the mobilization of Pu in near-surface environments: through the transformation of Pu associated with solid phases, production of extracellular polymeric substances (EPS) carrier phases, and the creation of microenvironments. Also, microbial processes are central to the immobilization of Pu species, through the metabolism of organically complexed Pu species and Pu associated with extracellular carrier phases and the creation of environments favorable for Pu transport retardation.

  3. Biogeochemical Cycling and Environmental Stability of Pu Relevant to Long-Term Stewardship of DOE Sites

    SciTech Connect

    Santschi, Peter H.

    2006-06-01

    The overall objective of this proposed research is to understand the biogeochemical cycling of Pu in environments of interest to long-term DOE stewardship issues. Central to Pu cycling (transport initiation to immobilization) is the role of microorganisms. The hypothesis underlying this proposal is that microbial activity is the causative agent in initiating the mobilization of Pu in near-surface environments: through the transformation of Pu associated with solid phases, production of extracellular polymeric substances (EPS) carrier phases, and the creation of microenvironments. Also, microbial processes are central to the immobilization of Pu species, through the metabolism of organically complexed Pu species and Pu associated with extracellular carrier phases and the creation of environments favorable for Pu transport retardation.

  4. Quantifying the effects of mountain pine beetle infestation on water and biogeochemical cycles at multiple spatial and temporal scales

    NASA Astrophysics Data System (ADS)

    Brooks, P. D.; Harpold, A. A.; Somor, A. J.; Troch, P. A.; Gochis, D. J.; Ewers, B. E.; Pendall, E.; Biederman, J. A.; Reed, D.; Barnard, H. R.; Whitehouse, F.; Aston, T.; Borkhuu, B.

    2010-12-01

    Unprecedented levels of bark beetle infestation over the last decade have radically altered forest structure across millions of hectares of Western U.S. montane environments. The widespread extent of this disturbance presents a major challenge for governments and resource managers who lack a predictive understanding of how water and biogeochemical cycles will respond to this disturbance over various temporal and spatial scales. There is a widespread perception, largely based on hydrological responses to fire or logging, that a reduction in both transpiration and interception following tree death will increase soil water availability and catchment water yield. However, few studies have directly addressed the effects of insect-induced forest decline on water and biogeochemical cycling. We address this knowledge gap using observations and modeling at scales from 100 to 109 m2 across study sites in CO and WY that vary in the intensity and timing of beetle infestation and tree death. Our focus on multiple sites with different levels of impact allows us to address two broad, organizing questions: How do changes in vegetation structure associated with MPB alter the partitioning of energy and water? And How do these changes in energy and water availability affect local to regional scale water and biogeochemical cycles? This presentation will focus primarily on energy balance and water partitioning, providing context for ongoing biogeochemical work. During the growing season, stand-scale transpiration declines rapidly and soil moisture increases following infestation, consistent with streamflow data from regional catchments that shows an increase in baseflow following widespread attack. During the winter and spring, stand scale snow surveys and continuous snow depth sensors suggested that the variability in snow cover decreased as the severity of beetle impact increases, but there were no significant stand-scale differences in snow depth among levels of impact. This is due

  5. Role of sea ice in global biogeochemical cycles: emerging views and challenges

    NASA Astrophysics Data System (ADS)

    Vancoppenolle, Martin; Meiners, Klaus M.; Michel, Christine; Bopp, Laurent; Brabant, Frédéric; Carnat, Gauthier; Delille, Bruno; Lannuzel, Delphine; Madec, Gurvan; Moreau, Sébastien; Tison, Jean-Louis; van der Merwe, Pier

    2013-11-01

    Observations from the last decade suggest an important role of sea ice in the global biogeochemical cycles, promoted by (i) active biological and chemical processes within the sea ice; (ii) fluid and gas exchanges at the sea ice interface through an often permeable sea ice cover; and (iii) tight physical, biological and chemical interactions between the sea ice, the ocean and the atmosphere. Photosynthetic micro-organisms in sea ice thrive in liquid brine inclusions encased in a pure ice matrix, where they find suitable light and nutrient levels. They extend the production season, provide a winter and early spring food source, and contribute to organic carbon export to depth. Under-ice and ice edge phytoplankton blooms occur when ice retreats, favoured by increasing light, stratification, and by the release of material into the water column. In particular, the release of iron - highly concentrated in sea ice - could have large effects in the iron-limited Southern Ocean. The export of inorganic carbon transport by brine sinking below the mixed layer, calcium carbonate precipitation in sea ice, as well as active ice-atmosphere carbon dioxide (CO2) fluxes, could play a central role in the marine carbon cycle. Sea ice processes could also significantly contribute to the sulphur cycle through the large production by ice algae of dimethylsulfoniopropionate (DMSP), the precursor of sulphate aerosols, which as cloud condensation nuclei have a potential cooling effect on the planet. Finally, the sea ice zone supports significant ocean-atmosphere methane (CH4) fluxes, while saline ice surfaces activate springtime atmospheric bromine chemistry, setting ground for tropospheric ozone depletion events observed near both poles. All these mechanisms are generally known, but neither precisely understood nor quantified at large scales. As polar regions are rapidly changing, understanding the large-scale polar marine biogeochemical processes and their future evolution is of high

  6. Biogeochemical cycling of cadmium isotopes along a high-resolution section through the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Conway, Tim M.; John, Seth G.

    2015-01-01

    Cadmium (Cd) is a bioactive trace element in the oceans, with a nutrient-like distribution that closely matches dissolved phosphate. Seawater-dissolved stable Cd isotope ratios (δ114Cd) are a relatively new parameter, which show much promise for furthering our understanding of the biogeochemical cycling of Cd in the oceans. Here we present a high-resolution paired section of dissolved Cd concentrations and dissolved δ114Cd from 21 open-ocean stations along the US GEOTRACES GA03 transect through the North Atlantic Ocean. Dissolved Cd concentrations along the section are strongly influenced by water-mass distribution and the cycling of Cd. The highest dissolved Cd concentrations (400-540 pmol kg-1) are associated with Antarctic-sourced water masses, whilst biological uptake in the surface ocean results in a strong vertical gradient in dissolved Cd towards the surface, reaching as low as 0.03 pmol kg-1 in western surface waters. Dissolved δ114Cd is also characterized by a vertical gradient from ∼+0.2‰ in the deep ocean to +2‰ to +5‰ in the Cd-depleted surface ocean (relative to NIST SRM 3108). This variability in δ114Cd can be ascribed to mixing of Antarctic and North Atlantic water masses, together with fractionation due to in situ biological uptake of light Cd in the very surface ocean. Subtle deviations from this overall pattern of dissolved Cd concentration and dissolved δ114Cd are observed within low-oxygen waters off North Africa, where a dissolved Cd deficit relative to phosphate is associated with higher dissolved δ114Cd values. Together with elevated particulate Cd and Ba, this suggests that Cd sulfide precipitation is occurring within the water column of the North Atlantic, constituting a potentially important sink for isotopically light Cd. Additionally, the first measurements of dissolved δ114Cd within a hydrothermal plume at the Mid-Atlantic Ridge show that Cd is scavenged from the dissolved phase, leaving the remnant dissolved Cd

  7. Changes in mineral soil biogeochemical cycling and environmental conditions following tree harvest in the Northeast

    NASA Astrophysics Data System (ADS)

    Vario, C.; Friedland, A.

    2012-12-01

    to a minimum of 53 Mg ha-1 in the 75 year old stand. In our carbon flux measurements, we observed higher DOC concentrations in lysimeter samples collected at 30 cm at 12 years after harvest. We have also documented consistently higher soil temperatures across summer months at 50 cm below the mineral soil in the recently clear-cut site at Bartlett Experimental Forest. These changes in biogeochemical and environmental conditions suggest that forest clearing does affect mineral soil, and our findings may help identify a mechanism to explain the observed carbon loss from soils in clear-cut forests.

  8. Biogeochemical cycles in tropical Oceania: insights from Magnesium isotopes in the Liwu river, Taiwan.

    NASA Astrophysics Data System (ADS)

    Bedja, Imene; Galy, Albert

    2016-04-01

    We analyzed the isotopic composition of dissolved Mg in the Liwu catchment, Taiwan, impacted by typhoon events to understand the control on the temporal variability of water chemistry. The river chemistry is driven by the mixing of three water masses, characterized by constant and distinct chemistry composition: Rapid Surface Runoff (RSR), Slow Surface Runoff (SSR) and Deep Ground Water (DG). The relative contribution of these end members is estimated using a hydrograph separation model. A dense tropical forest covers the Liwu catchment and might affect the chemistry of the river. In fact, plants absorb their essential nutrient such as magnesium (Mg) from the draining water. Such biological pumping introduces an isotopic fractionation in the river water. With the consideration of other processes like chemical weathering and hydrological mixture, this study aims to bring out the biogeochemical cycle of Mg and consequently to quantify the feedback of biological factor on the river chemistry. Magnesium has three stables isotopes (24Mg, 25Mg and 26Mg) and the 26Mg/24Mg ratio (expressed as δ26Mg) is accurately measured, with precision of 0.09‰ at 95% confidence level, using the standard sample bracketing technique by MC-ICP-MS. The δ26Mg of sampled water range between: -0.96‰ and -1.44 ‰ on the DSM3 scale but is poorly correlated with the relative proportion of Mg brought by each of the RSR, SSR and DG end-members ruling out a pure hydrological control on the riverine δ26Mg. The δ26Mg can also record processes since 26Mg is preferentially scavenged during precipitation of secondary clay minerals or uptake by the biomass. However, the elemental uptake of silicon (Si) versus Mg is greatly different between those two processes. To unravel the dominant process of Mg isotope fractionation, we will discuss a coupling of δ26Mg values of the end-members reflecting the incorporation of Mg during clay formation and biomass uptake, with the masse balance of elemental

  9. Chromium biogeochemical cycle in Abu Kir Bay, east of Alexandria, Egypt

    NASA Astrophysics Data System (ADS)

    Aboul Dahab, O.

    1989-10-01

    Abu Kir Bay, east of Alexandria, is affected by two main point sources of pollution, namely Tabia Pumping Station and Lake Edku Outlet. Chromium was measured in the Bay effluents, sea water, marine organisms of different trophic levels, and sediments. Chromium concentration and mass emission from TPS (242 μg l -1 and 436 kg d -1) to the Bay are very high compared to those of Lake Edku Outlet (33 μg l -1 and 116 kg d -1). Average Cr concentrations in the Bay coastal waters during the period of study, were 0·120 μg l -1, 0·775 μg l -1 and 1·185 μg l -1, respectively, for Cr(III), Cr(VI), and particulate pphase. The surface distribution of Cr in the coastal waters showed the impact of Tabia Pumping Station on the Bay. On the basis of sediment concentrations of Cr in Abu Kir Bay, two 'hot spots' of the element were identified. The area around Tabia Pumping Station outfall (> 300 μg g -1 dw) and another one in the immediate vincinity of Lake Outlet (> 200 μg g -1 dw). Chromium concentrations in Abu Kir Bay organisms increased in the following order: mixed plankton (68 μg kg -1) > Sardina pilchardus (80 μg kg -1) ⩾ Mugil capito (82 μg kg -1) > Mullus barbatus (111 μ kg -1) > Solea solea (123 μg kg -1) > Penaeus kerathurus (168 μg kg -1 > Donax trunculus (209 μ kg -1) > Neptunus pelagicus (369 μg kg -1) > Ulva species (1867 μg kg -1) > Enteromorpha species (3345 μg kg -1). The sequence is consistent for organisms from both west and east Abu Kir Bay, regardless of the significantly low Cr concentrations of the latter. The study showed that algae and crabs play a critical role in the biological transport of Cr and can be considered the best accumulators of the element. From the total amount of Cr flux to the Bay, 552 kg d -1, flushing of the Bay to the open sea removes 262 kg d -1, and sedimentation within the Bay is 242 kg d -1. Finally, an input/output box model for Cr in Abu Kir Bay was constructed to help in understanding its biogeochemical cycle.

  10. Urbanization Impacts on Tree Canopies: The Unexplored Link Between Canopy Epiphytes and Pacific Northwest Forest Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Prather, H.; Rosenstiel, T. N.

    2014-12-01

    Canopy-dwelling cryptogamic plants (i.e. lichens and mosses) serve important roles in biogeochemical cycles worldwide and are of particular importance to biogeochemical cycling in Pacific Northwest forests. Epiphytic lichens and mosses respond sensitively to both direct and indirect effects of global change, as evidenced by distinct changes in epiphyte community structure. Yet, few studies have explored how shifting epiphytic communities, resulting from changing climate and increasing air pollutant exposure, may greatly impact biogeochemical cycles of the forests they inhabit. We present the first study investigating how urbanization, as a proxy for global change, impacts epiphytic community structure and functional biodiversity and address the impending effects on Pacific Northwest forest biogeochemical cycles. We discuss the results of paired ground and arboreal epiphyte surveys across an urban to rural gradient in Portland, Oregon. Three research sites with varying distance (0km, 74km, and 109km) from urban center were surveyed and epiphytic biodiversity was described. Pronounced shifts in epiphyte community structure were observed downwind of the Portland metro region. These results suggest that the impacts of urbanization may have significant and surprisingly far-reaching impacts on forested ecosystems in the Pacific Northwest. The impacts of an altered ground and arboreal epiphytic community on Pacific Northwest forest biogeochemical processes will be discussed.

  11. Impact of agriculture on the Si biogeochemical cycle: Input from phytolith studies

    NASA Astrophysics Data System (ADS)

    Keller, Catherine; Guntzer, Flore; Barboni, Doris; Labreuche, Jérôme; Meunier, Jean-Dominique

    2012-11-01

    The cycles of C and Si are closely related to the weathering of silicates. In both cycles, terrestrial plants make significant contributions to the weathering budget and soil formation. The perturbation of the terrestrial Si cycle by human occupation has become a challenging issue because of possible impact on the equilibrium of aquatic ecosystems and agriculture sustainability. The recycling of Si stored in plants as phytoliths may control the Si cycle in the short-term. A review of the recent literature shows that the biogeochemical cycling of Si that is generally not impacted by atmospheric input or fertilisation, is significantly altered by agriculture through the depletion of the phytoliths pool. We present here new evidence that the exportation of straw can lead to the depletion of the soil phytoliths pool in ˜10 years. In order to maintain the current levels of Si in crops, the contribution of other soil silicates such as clay minerals to the phytoavailable silica pool may become a key parameter, when straw is exported.

  12. Modeling carbon cycle responses to tree mortality: linking microbial and biogeochemical changes

    NASA Astrophysics Data System (ADS)

    Moore, D. J.; Trahan, N. A.; Dynes, E. L.; Zobitz, J. M.; Gallery, R.

    2013-12-01

    Amid a worldwide increase in tree mortality, mountain pine beetles (Dendroctonus ponderosae Hopkins) have killed billions of trees from Mexico to Alaska in the last 13 years. This mortality is predicted to influence important carbon, water and energy balance feedbacks on the Earth system. We studied changes in soil biogeochemical cycling and microbial community structure after tree mortality. We show, using a decade long chronosequence, that tree mortality causes no increase in total respiration from local to watershed scales, with corresponding changes in biogeochemical pools of nitrogen and phosphorus. We also found comparable declines in both gross primary productivity and respiration suggesting little change in net flux. We tested the mechanisms controlling these patterns using an ecosystem model; contrasting a simplified microbial subroutine with a 'dead soil' model. We coupled our modeling work with direct measurements of microbial biomass, enzyme kinetics and community structure. The transitory recovery of respiration 6-7 years after mortality was associated with increased microbial biomass, increased incorporation of leaf litter carbon into soil organic matter, and was followed by a secondary decline in respiration during years 8-10. Our findings are consistent with the mechanism of reduced input of new carbon causing a decline in microbial biomass rather than an increased output of older carbon.

  13. Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Le Quéré, C.; Buitenhuis, E. T.; Moriarty, R.; Alvain, S.; Aumont, O.; Bopp, L.; Chollet, S.; Enright, C.; Franklin, D. J.; Geider, R. J.; Harrison, S. P.; Hirst, A.; Larsen, S.; Legendre, L.; Platt, T.; Prentice, I. C.; Rivkin, R. B.; Sathyendranath, S.; Stephens, N.; Vogt, M.; Sailley, S.; Vallina, S. M.

    2015-07-01

    Global ocean biogeochemistry models currently employed in climate change projections use highly simplified representations of pelagic food webs. These food webs do not necessarily include critical pathways by which ecosystems interact with ocean biogeochemistry and climate. Here we present a global biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types (PFTs); six types of phytoplankton, three types of zooplankton, and heterotrophic bacteria. We improved the representation of zooplankton dynamics in our model through (a) the explicit inclusion of large, slow-growing zooplankton, and (b) the introduction of trophic cascades among the three zooplankton types. We use the model to quantitatively assess the relative roles of iron vs. grazing in determining phytoplankton biomass in the Southern Ocean High Nutrient Low Chlorophyll (HNLC) region during summer. When model simulations do not represent crustacean macrozooplankton grazing, they systematically overestimate Southern Ocean chlorophyll biomass during the summer, even when there was no iron deposition from dust. When model simulations included the developments of the zooplankton component, the simulation of phytoplankton biomass improved and the high chlorophyll summer bias in the Southern Ocean HNLC region largely disappeared. Our model results suggest that the observed low phytoplankton biomass in the Southern Ocean during summer is primarily explained by the dynamics of the Southern Ocean zooplankton community rather than iron limitation. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean.

  14. Numerical modeling of watershed-scale radiocesium transport coupled with biogeochemical cycling in forests

    NASA Astrophysics Data System (ADS)

    Mori, K.; Tada, K.; Tawara, Y.; Tosaka, H.; Ohno, K.; Asami, M.; Kosaka, K.

    2015-12-01

    Since the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, intensive monitoring and modeling works on radionuclide transfer in environment have been carried out. Although Cesium (Cs) concentration has been attenuating due to both physical and environmental half-life (i.e., wash-off by water and sediment), the attenuation rate depends clearly on the type of land use and land cover. In the Fukushima case, studying the migration in forest land use is important for predicting the long-term behavior of Cs because most of the contaminated region is covered by forests. Atmospheric fallout is characterized by complicated behavior in biogeochemical cycle in forests which can be described by biotic/abiotic interactions between many components. In developing conceptual and mathematical model on Cs transfer in forest ecosystem, defining the dominant components and their interactions are crucial issues (BIOMASS, 1997-2001). However, the modeling of fate and transport in geosphere after Cs exports from the forest ecosystem is often ignored. An integrated watershed modeling for simulating spatiotemporal redistribution of Cs that includes the entire region from source to mouth and surface to subsurface, has been recently developed. Since the deposited Cs can migrate due to water and sediment movement, the different species (i.e., dissolved and suspended) and their interactions are key issues in the modeling. However, the initial inventory as source-term was simplified to be homogeneous and time-independent, and biogeochemical cycle in forests was not explicitly considered. Consequently, it was difficult to evaluate the regionally-inherent characteristics which differ according to land uses, even if the model was well calibrated. In this study, we combine the different advantages in modeling of forest ecosystem and watershed. This enable to include more realistic Cs deposition and time series of inventory can be forced over the land surface. These processes are integrated

  15. Thermodynamic stability analysis of the carbon biogeochemical cycle in aquatic shallow environments

    NASA Astrophysics Data System (ADS)

    Lvov, S. N.; Pastres, R.; Marcomini, A.

    1996-10-01

    We carry out the thermodynamic stability analysis of the carbon cycle in a lagoon. Our approach differs from linear stability analysis, and is based on the excess entropy production. The coupled biogeochemical processes in the lagoon include gas transfer, photosynthesis, respiration, decomposition, sedimentation, and oxidation of algae. The thermodynamic stability criterion derived from this analysis indicates that, in addition to known limiting factors of biomass production such as temperature, light, and nitrogen and phosphorous concentrations, the rate of carbon dioxide delivery from the air reservoir to the water can be also a limiting factor. For the Venice lagoon, the criterion obtained predicts that a doubling of the CO 2 partial pressure in the atmosphere can render the system unstable, driving it to dramatic biomass production and degradation.

  16. Biogeochemical cycling of selenium in the San Joaquin Valley, California, USA

    NASA Astrophysics Data System (ADS)

    Presser, Theresa S.; Ohlendorf, Harry M.

    1987-11-01

    Subsurface agricultural drainage waters from western San Joaquin Valley, California, were found to contain elevated concentrations of the element selenium in the form of selenate. In 1978, these drainage waters began to replace previous input to Kesterson Reservoir, a pond system within Kesterson National Wildlife Refuge; this substitution was completed by 1982. In the 1983 nesting season, unusual rates of deformity and death in embryos and hatchlings of wild aquatic birds (up to 64% of eared grebe and American coot nests) occurred at the refuge and were attributed to selenium toxicosis. Features necessary for contamination to have taken place included geologic setting, climate, soil type, availability of imported irrigation water, type of irrigation, and the unique chemical properties of selenium. The mechanisms of biogeochemical cycling raise questions about other ecosystems and human exposure.

  17. Biogeochemical cycling of selenium in the San Joaquin Valley, California, USA

    USGS Publications Warehouse

    Presser, T.S.; Ohlendorf, H.M.

    1987-01-01

    Subsurface agricultural drainage waters from western San Joaquin Valley, California, were found to contain elevated concentrations of the element selenium in the form of selenate. In 1978, these drainage waters began to replace previous input to Kesterson Reservoir, a pond system within Kesterson National Wildlife Refuge; this substitution was completed by 1982. In the 1983 nesting season, unusual rates of deformity and death in embryos and hatchlings of wild aquatic birds (up to 64% of eared grebe and American coot nests) occurred at the refuge and were attributed to selenium toxicosis. Features necessary for contamination to have taken place included geologic setting, climate, soil type, availability of imported irrigation water, type of irrigation, and the unique chemical properties of selenium. The mechanisms of biogeochemical cycling raise questions about other ecosystems and human exposure.

  18. Paleoarchean sulfur cycle and biogeochemical surface conditions on the early Earth, Barberton, South Africa

    NASA Astrophysics Data System (ADS)

    Grosch, Eugene G.; McLoughlin, Nicola

    2013-09-01

    This study presents the first multiple sulfur isotope dataset on sulfides from the ca. 3.5-3.2 Ga Onverwacht Group in the Paleoarchean Barberton Greenstone Belt (BGB) of South Africa. In situ δ34SCDT and Δ33S values of pyrite (n=568) are reported from a wide range of hydrothermal, volcanic and sedimentary environments and are used to explore Mid-Archean biogeochemical sulfur cycling. Samples are from fresh drill core collected by the Barberton Scientific Drilling Project that intercepted cherts, metabasalts and sheared ultramafics of the ˜3.3-3.35 Ga Kromberg Formation; the sedimentary units of the ˜3.432 Ga Noisy formation; and the unconformably underlying metabasaltic pillow lavas of the ˜3.472 Ga Hooggenoeg Formation.

  19. The biogeochemical sulfur cycle in the marine boundary layer over the Northeast Pacific Ocean

    NASA Technical Reports Server (NTRS)

    Bates, T. S.; Johnson, J. E.; Quinn, P. K.; Goldan, P. D.; Kuster, W. C.

    1990-01-01

    The major components of the marine boundary layer biogeochemical sulfur cycle were measured simultaneously onshore and off the coast of Washington State, U.S.A. during May 1987. Seawater dimethysulfide (DMS) concentrations on the continental shelf were strongly influenced by coastal upwelling. Concentration further offshore were typical of summer values (2.2 nmol/l) at this latitude. Although seawater DMS concentrations were high on the biologically productive continental shelf (2-12 nmol/l), this region had no measurable effect on atmospheric DMS concentrations. Atmospheric DMS concentrations (0.1-12 nmol/l), however, were extremely dependent upon wind speed and boundary layer height. Although there appeared to be an appreciable input of nonsea-salt sulfate to the marine boundary layer from the free troposphere, the local flux of DMS from the ocean to the atmosphere was sufficient to balance the remainder of the sulfur budget.

  20. The biogeochemical cycling of zinc and zinc isotopes in the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Conway, Tim M.; John, Seth G.

    2014-10-01

    Zinc (Zn) is a marine micronutrient, with an overall oceanic distribution mirroring the major macronutrients, especially silicate. Seawater Zn isotope ratios (δ66Zn) are a relatively new oceanographic parameter which may offer insights into the biogeochemical cycling of Zn. To date, the handful of published studies of seawater δ66Zn show the global deep ocean to be both remarkably homogeneous (approximately +0.5‰) and isotopically heavier than the marine sources of Zn (+0.1 to +0.3‰). Here we present the first high-resolution oceanic section of δ66Zn, from the U.S. GEOTRACES GA03 North Atlantic Transect, from Lisbon to Woods Hole. Throughout the surface ocean, biological uptake and release of isotopically light Zn, together with scavenging of heavier Zn, leads to large variability in δ66Zn. In the ocean below 1000 m, δ66Zn is generally homogeneous (+0.50 ± 0.14‰; 2 SD), though deviations from +0.5‰ allow us to identify specific sources of Zn. The Mediterranean Outflow is characterized by δ66Zn of +0.1 to +0.3‰, while margin sediments are a source of isotopically light Zn (-0.5 to -0.8‰), which we attribute to release of nonregenerated biogenic Zn. Mid-Atlantic Ridge hydrothermal vents are also a source of light Zn (close to -0.5‰), though Zn is not transported far from the vents. Understanding the biogeochemical cycling of Zn in the modern ocean begins to address the imbalance between the light δ66Zn signature of marine sources and the globally homogeneous deep oceans (δ66Zn of +0.5‰) on long timescales, with overall patterns pointing to sediments as an important sink for isotopically light Zn throughout the oceans.

  1. The role of airborne volcanic ash for the surface ocean biogeochemical iron-cycle: a review

    NASA Astrophysics Data System (ADS)

    Duggen, S.; Olgun, N.; Croot, P.; Hoffmann, L.; Dietze, H.; Delmelle, P.; Teschner, C.

    2010-03-01

    Iron is a key micronutrient for phytoplankton growth in the surface ocean. Yet the significance of volcanism for the marine biogeochemical iron-cycle is poorly constrained. Recent studies, however, suggest that offshore deposition of airborne ash from volcanic eruptions is a way to inject significant amounts of bio-available iron into the surface ocean. Volcanic ash may be transported up to several tens of kilometers high into the atmosphere during large-scale eruptions and fine ash may stay aloft for days to weeks, thereby reaching even the remotest and most iron-starved oceanic regions. Scientific ocean drilling demonstrates that volcanic ash layers and dispersed ash particles are frequently found in marine sediments and that therefore volcanic ash deposition and iron-injection into the oceans took place throughout much of the Earth's history. Natural evidence and the data now available from geochemical and biological experiments and satellite techniques suggest that volcanic ash is a so far underestimated source for iron in the surface ocean, possibly of similar importance as aeolian dust. Here we summarise the development of and the knowledge in this fairly young research field. The paper covers a wide range of chemical and biological issues and we make recommendations for future directions in these areas. The review paper may thus be helpful to improve our understanding of the role of volcanic ash for the marine biogeochemical iron-cycle, marine primary productivity and the ocean-atmosphere exchange of CO2 and other gases relevant for climate in the Earth's history.

  2. Biogeochemical cycles and biodiversity as key drivers of ecosystem services provided by soils

    NASA Astrophysics Data System (ADS)

    Smith, P.; Cotrufo, M. F.; Rumpel, C.; Paustian, K.; Kuikman, P. J.; Elliott, J. A.; McDowell, R.; Griffiths, R. I.; Asakawa, S.; Bustamante, M.; House, J. I.; Sobocká, J.; Harper, R.; Pan, G.; West, P. C.; Gerber, J. S.; Clark, J. M.; Adhya, T.; Scholes, R. J.; Scholes, M. C.

    2015-11-01

    Soils play a pivotal role in major global biogeochemical cycles (carbon, nutrient, and water), while hosting the largest diversity of organisms on land. Because of this, soils deliver fundamental ecosystem services, and management to change a soil process in support of one ecosystem service can either provide co-benefits to other services or result in trade-offs. In this critical review, we report the state-of-the-art understanding concerning the biogeochemical cycles and biodiversity in soil, and relate these to the provisioning, regulating, supporting, and cultural ecosystem services which they underpin. We then outline key knowledge gaps and research challenges, before providing recommendations for management activities to support the continued delivery of ecosystem services from soils. We conclude that, although soils are complex, there are still knowledge gaps, and fundamental research is still needed to better understand the relationships between different facets of soils and the array of ecosystem services they underpin, enough is known to implement best practices now. There is a tendency among soil scientists to dwell on the complexity and knowledge gaps rather than to focus on what we do know and how this knowledge can be put to use to improve the delivery of ecosystem services. A significant challenge is to find effective ways to share knowledge with soil managers and policy makers so that best management can be implemented. A key element of this knowledge exchange must be to raise awareness of the ecosystems services underpinned by soils and thus the natural capital they provide. We know enough to start moving in the right direction while we conduct research to fill in our knowledge gaps. The lasting legacy of the International Year of Soils in 2015 should be for soil scientists to work together with policy makers and land managers to put soils at the centre of environmental policy making and land management decisions.

  3. The Coordination and Harmonics of Biogeochemical Cycles in North Inlet, SC Salt Marshes

    NASA Astrophysics Data System (ADS)

    Morris, J. T.

    2015-12-01

    North Inlet is a pristine estuary within a small coastal watershed with minimal surface water input or human impact. North Inlet exchanges its water with the coastal ocean with a turnover time of about 0.5 per day. Its marshes are dominated by the grass Spartina alterniflora. Growth rates of Spartina have been measured monthly on permanent plots in North Inlet since 1984, and concentrations of porewater ammonium and phosphate, and sulfide have been measured monthly over depth (10-100 cm) since 1994. The salt marsh shows pronounced seasonal biogeochemical cycles that are highly correlated. Ammonium, phosphate and sulfide concentrations all peak in August-October and are minimal during February-April. Mean monthly ammonium concentration varies between 42 and 87 μM, phosphate between 3 and 18 μM, and sulfide between 8 and 87 μM. Monthly growth rates of Spartina range from 91 to 111 g dry weight m-2 between April and September. The integrated total aboveground production is 25 mol C m-2 yr-1. The inventories of N and P in porewater are small fractions of what is required to support primary production. Primary production is N-limited and this is consistent with the N:P ratio declining from 14 during early spring to 5 in late summer. There are losses, especially of N, from drainage, denitrification, and export of organic production. These have to be compensated by gains from N fixation, most likely from coupled sulfate reduction. There is also a coupling between sulfide, iron, and phosphorous that appears to conserve P during the winter and generate soluble P during the active growing season. These couplings coordinate the biogeochemical cycles, and this extends to the tidal creeks that are dominated by benthic sources of nutrients.

  4. The impacts of climate change and human activities on biogeochemical cycles on the Qinghai-Tibetan Plateau.

    PubMed

    Chen, Huai; Zhu, Qiuan; Peng, Changhui; Wu, Ning; Wang, Yanfen; Fang, Xiuqing; Gao, Yongheng; Zhu, Dan; Yang, Gang; Tian, Jianqing; Kang, Xiaoming; Piao, Shilong; Ouyang, Hua; Xiang, Wenhua; Luo, Zhibin; Jiang, Hong; Song, Xingzhang; Zhang, Yao; Yu, Guirui; Zhao, Xinquan; Gong, Peng; Yao, Tandong; Wu, Jianghua

    2013-10-01

    With a pace of about twice the observed rate of global warming, the temperature on the Qinghai-Tibetan Plateau (Earth's 'third pole') has increased by 0.2 °C per decade over the past 50 years, which results in significant permafrost thawing and glacier retreat. Our review suggested that warming enhanced net primary production and soil respiration, decreased methane (CH(4)) emissions from wetlands and increased CH(4) consumption of meadows, but might increase CH(4) emissions from lakes. Warming-induced permafrost thawing and glaciers melting would also result in substantial emission of old carbon dioxide (CO(2)) and CH(4). Nitrous oxide (N(2)O) emission was not stimulated by warming itself, but might be slightly enhanced by wetting. However, there are many uncertainties in such biogeochemical cycles under climate change. Human activities (e.g. grazing, land cover changes) further modified the biogeochemical cycles and amplified such uncertainties on the plateau. If the projected warming and wetting continues, the future biogeochemical cycles will be more complicated. So facing research in this field is an ongoing challenge of integrating field observations with process-based ecosystem models to predict the impacts of future climate change and human activities at various temporal and spatial scales. To reduce the uncertainties and to improve the precision of the predictions of the impacts of climate change and human activities on biogeochemical cycles, efforts should focus on conducting more field observation studies, integrating data within improved models, and developing new knowledge about coupling among carbon, nitrogen, and phosphorus biogeochemical cycles as well as about the role of microbes in these cycles. PMID:23744573

  5. Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Le Quéré, Corinne; Buitenhuis, Erik T.; Moriarty, Róisín; Alvain, Séverine; Aumont, Olivier; Bopp, Laurent; Chollet, Sophie; Enright, Clare; Franklin, Daniel J.; Geider, Richard J.; Harrison, Sandy P.; Hirst, Andrew G.; Larsen, Stuart; Legendre, Louis; Platt, Trevor; Prentice, I. Colin; Rivkin, Richard B.; Sailley, Sévrine; Sathyendranath, Shubha; Stephens, Nick; Vogt, Meike; Vallina, Sergio M.

    2016-07-01

    Global ocean biogeochemistry models currently employed in climate change projections use highly simplified representations of pelagic food webs. These food webs do not necessarily include critical pathways by which ecosystems interact with ocean biogeochemistry and climate. Here we present a global biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types (PFTs): six types of phytoplankton, three types of zooplankton, and heterotrophic procaryotes. We improved the representation of zooplankton dynamics in our model through (a) the explicit inclusion of large, slow-growing macrozooplankton (e.g. krill), and (b) the introduction of trophic cascades among the three zooplankton types. We use the model to quantitatively assess the relative roles of iron vs. grazing in determining phytoplankton biomass in the Southern Ocean high-nutrient low-chlorophyll (HNLC) region during summer. When model simulations do not include macrozooplankton grazing explicitly, they systematically overestimate Southern Ocean chlorophyll biomass during the summer, even when there is no iron deposition from dust. When model simulations include a slow-growing macrozooplankton and trophic cascades among three zooplankton types, the high-chlorophyll summer bias in the Southern Ocean HNLC region largely disappears. Our model results suggest that the observed low phytoplankton biomass in the Southern Ocean during summer is primarily explained by the dynamics of the Southern Ocean zooplankton community, despite iron limitation of phytoplankton community growth rates. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean.

  6. Sea Level Rise Modifies Biogeochemical Cycles in Winyah Bay, South Carolina Wetlands

    NASA Astrophysics Data System (ADS)

    Chow, A. T.; Conner, W.; Rhew, R. C.; Suhre, D.; Wang, J.

    2013-12-01

    Rising sea level along the relatively flat southeastern US coastal plain significantly changes both vegetation composition and salinity of coastal wetlands, eventually modifying ecosystem functions and biogeochemical processes of these wetlands. We conducted a two-year study to evaluate the dynamics and relationships among aboveground productivity, greenhouse and halocarbon gas emissions, nutrients, and dissolved organic matter of a freshwater forested wetland, a salt-impacted and degraded forested wetland, and a salt marsh in Winyah Bay, South Carolina, representing the salinity gradient and the transition from freshwater forested wetland to salt marsh due to sea level rise. The degraded forested wetland had significantly lower above-ground productivity with annual stem growth of 102 g/m^2/yr and litterfall of 392 g/m^2/yr compared to the freshwater forested wetland (230 and 612 g/m^2/yr, respectively). High methane emission [> 50 mmol/m2/day, n = 4] was only observed in the freshwater-forested wetland but there was a strong smell of sulfide noticed in the salt marsh, suggesting that different redox processes control the decomposition of natural organic matter along the salinity gradient. In addition, the largest CHCl3 [209 × 183 nmol/m2/day, n = 4] emission was observed in the degraded forested wetland, but net CH3Cl [257 × 190 nmol/m2/day, n = 4] and CH3Br [28 × 20 nmol/m2/day, n = 4] emissions were only observed in the salt marsh, suggesting different mechanisms in response to salt intrusion at that sites. The highest DOC concentration (28 - 42 mg/L) in monthly water samples was found in degraded forest wetland, followed by the freshwater forested wetland (19 - 38 mg/L) and salt marsh (9 - 18 mg/L). Results demonstrate that the salt-impacted degraded wetland has unique biogeochemical cycles that differ from unaltered freshwater forested wetland and salt marsh.

  7. How life affects the geochemical cycle of carbon

    NASA Technical Reports Server (NTRS)

    Walker, James C. G.

    1992-01-01

    Developing a quantitative understanding of the biogeochemical cycles of carbon as they have worked throughout Earth history on various time scales, how they have been affected by biological evolution, and how changes in the carbon content of ocean and atmosphere may have affected climate and the evolution of life are the goals of the research. Theoretical simulations were developed that can be tuned to reproduce such data as exist and, once tuned, can be used to predict properties that have not yet been observed. This is an ongoing process, in which models and results are refined as new data and interpretations become available and as understanding of the global system improves. Results of the research are described in several papers which were published or submitted for publication. These papers are summarized. Future research plans are presented.

  8. Holocene climate dynamics, biogeochemical cycles and ecosystem variability in the eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Schmiedl, Gerhard; Adloff, Fanny; Emeis, Kay; Grimm, Rosina; Maier-Reimer, Ernst; Mikolajewicz, Uwe; Möbius, Jürgen; Müller-Navarra, Katharina

    2013-04-01

    The past variability of biogeochemical processes and marine ecosystems of the eastern Mediterranean Sea (EMS) is documented in the form of organic-rich sapropels that occurred at northern hemisphere insolation maxima. In order to understand the processes leading from deglacial and Holocene climate variability to the formation of sapropel S1 via changed biogeochemical cycling in the EMS, we integrated results from global and regional Earth system model experiments with biogeochemical and micropaleontological proxy records. Our results suggest a high spatiotemporal variability of deep-water oxygenation and biogeochemical processes at the sea floor during the late glacial and early Holocene. Changes in trophic conditions of bathyal ecosystems along ocean margins are closely linked to the hydrology of the EMS borderlands; they reflect orbital and sub-orbital climate variations of the high northern latitudes and the African monsoon system. Local trophic conditions were particularly variable in the northern Aegean Sea as a response to changes in riverine runoff and Black Sea outflow. During the time of S1 deposition, average oxygen levels decreased exponentially with increasing water depth, suggesting a basin-wide shallowing of vertical convection superimposed by local signals. In the northernmost Aegean Sea, deep-water ventilation persisted during the early period of S1 formation, owing to temperature-driven local convection and the absence of low-salinity Black Sea outflow. At the same time, severe temporary dysoxia or even short anoxia occurred in the eastern Levantine basin at water depths as shallow as 900 m. This area was likely influenced by enhanced nutrient input of the Nile river that resulted in high organic matter fluxes and related high oxygen-consumption rates in the water column. In contrast, abyssal ecosystems of the Levantine and Ionian basins lack eutrophication during the early Holocene suggesting that enhanced productivity did not play a crucial role

  9. The Biogeochemical Role of Antarctic Krill and Baleen Whales in Southern Ocean Nutrient Cycling.

    NASA Astrophysics Data System (ADS)

    Ratnarajah, L.

    2015-12-01

    Iron limits primary productivity in large areas of the Southern Ocean. It has been suggested that baleen whales form a crucial part of biogeochemical cycling processes through the consumption of nutrient-rich krill and subsequent defecation, but evidence on their contribution is scarce. We analysed the concentration of iron in Antarctic krill and baleen whale faeces and muscle. Iron concentrations in Antarctic krill were over 1 million times higher, and whale faecal matter were almost 10 million times higher than typical Southern Ocean High Nutrient Low Chlorophyll seawater concentrations. This suggests that Antarctic krill act as a reservoir of in in Southern Ocean surface waters, and that baleen whales play an important role in converting this fixed iron into a liquid form in their faeces. We developed an exploratory model to examine potential contribution of blue, fin and humpback whales to the Southern Ocean iron cycle to explore the effect of the recovery of great whales to historical levels. Our results suggest that pre-exploitation populations of blue whales and, to a lesser extent fin and humpback whales, could have contributed to the more effective recycling of iron in surface waters, resulting in enhanced phytoplankton production. This enhanced primary productivity is estimated to be: 8.3 x 10-5 to 15 g C m-2 yr-1 (blue whales), 7 x 10-5 to 9 g C m-2 yr-1 (fin whales), and 10-5 to 1.7 g C m-2 yr-1 (humpback whales). To put these into perspective, current estimates of primary production in the Southern Ocean from remotely sensed ocean colour are in the order of 57 g C m-2 yr-1 (south of 50°). The high degree of uncertainty around the magnitude of these increases in primary productivity is mainly due to our limited quantitative understanding of key biogeochemical processes including iron content in krill, krill consumption rates by whales, persistence of iron in the photic zone, bioavailability of retained iron, and carbon-to-iron ratio of phytoplankton

  10. The effect of gold mining and processing on biogeochemical cycles in Muteh area, Isfahan province, Iran

    NASA Astrophysics Data System (ADS)

    Keshavarzi, B.; Moore, F.

    2009-04-01

    The environmental impacts of gold mining and processing on geochemical and biogeochemical cycles in Muteh region located northwest of Esfahan province and northeast of Golpaygan city is investigated. For this purpose systematic sampling was carried out in, rock, soil, water, and sediment environments along with plant, livestocks and human hair samples. Mineralogical and Petrological studies show that ore mineral such as pyrite and arsenopyrite along with fluorine-bearing minerals like tremolite, actinolite, biotite and muscovite occur in green schist, amphibolite and lucogranitic rocks in the area. The hydrochemistry of the analysed water samples indicate that As and F display the highest concentrations among the analysed elements. Indeed arsenic has the highest concentration in both topsoil and subsoil samples when compared with other potentially toxic elements. Anthropogenic activity also have it s greatest effect on increasing arsenic concentration among the analysed samples. The concentration of the majority of the analysed elements in the shoots and leaves of two local plants of the region i.e Artemesia and Penagum is higher than their concentration in the roots. Generally speaking, Artemesia has a greater tendency for bioaccumulating heavy metals. The results of cyanide analysis in soil samples show that cyanide concentration in the soils near the newly built tailing dam is much higher than that in the vicinity of the old tailing dam. The high concentration of fluorine in the drinking water of the Muteh village is the main reason of the observed dental fluorosis symptoms seen in the inhabitants. One of the two drinking water wells which is located near the metamorphic complex and supplies part of the tap water in the village, probably has the greatest impact in this regard. A decreasing trend in fluorine concentration is illustrated with increasing distance from the metamorphic complex. Measurements of As concentration in human hair specimens indicate that As

  11. Did large animals play an important role in global biogeochemical cycling in the past?

    NASA Astrophysics Data System (ADS)

    Doughty, C.

    2014-12-01

    In the late Pleistocene (~50-10,000 years ago), ninety-seven genera of large animals (>44kg) (megafauna) went extinct, concentrated in the Americas and Australia. The loss of megafauna had major effects on ecosystem structure, seed dispersal and land surface albedo. However, the impact of this dramatic extinction on ecosystem nutrient biogeochemistry, through the lateral transport of dung and bodies, has never been explored. Here we explore these nutrient impacts using a novel mathematical framework that analyses this lateral transport as a diffusion-like process and demonstrates that large animals play a disproportionately large role in the horizontal transfer of nutrients across landscapes. For example, we estimate that the extinction of the Amazonian megafauna led to a >98% reduction in the lateral transfer flux of the limiting nutrient phosphorus (P) with similar, though less extreme, decreases in all continents outside of Africa. This resulted in strong decreases in phosphorus availability in Eastern Amazonia away from fertile floodplains, a decline which may still be ongoing, and current P limitation in the Amazon basin may be partially a relic of an ecosystem without the functional connectedness it once had. More broadly, the Pleistocene megafaunal extinctions resulted in major and ongoing disruptions to terrestrial biogeochemical cycling at continental scales and increased nutrient heterogeneity globally.

  12. Biogeochemical processes and nutrient cycling within an artificial reef off Southern Portugal.

    PubMed

    Falcão, M; Santos, M N; Vicente, M; Monteiro, C C

    2007-06-01

    This study (2002/2004) examines the effect of artificial reef (AR) structures off the southern coast of Portugal on biogeochemical process and nutrient cycling. Organic and inorganic carbon, nitrogen, phosphorus and chlorophyll a were determined monthly in sediment cores and settled particles for a two-year period. Ammonium, nitrates, phosphates, silicates, total organic nitrogen and phosphorus, chlorophyll a and phaeopigments were also determined monthly in water samples within AR and control sites. Results of the two-year study showed that: (i) there was a significant exponential fit between organic carbon and chlorophyll a (r2=0.91; p<0.01) in reef sediment suggesting an increase of benthic productivity; (ii) organic carbon and nitrogen content in settled particles within AR environment was about four times higher two years after reef deployment; (iii) nutrients and chlorophyll a in the water column were higher at AR than control site. Two years after AR deployment, dissolved organic and inorganic compounds in near bottom water were 30-60% higher, emphasizing benthic remineralization processes at AR's organically rich sediment. Marked chemical changes in the ecosystem were observed during the two-year study period, reinforcing the importance of these structures for sandy coastal areas rehabilitation through trophic chain pull-out. PMID:17239434

  13. Parallel geochemical and metagenomic datasets reveal biogeochemical cycling in a hot spring ecosystem

    NASA Astrophysics Data System (ADS)

    Meyer-Dombard, D. R.; Swingley, W.; Raymond, J.; Shock, E.

    2012-12-01

    Environmental sequence data (2,321 16S rRNA clones and 470 megabases of "metagenome" sequence) were produced from biofilms at five sites in the outflow of "Bison Pool" (BP), an alkaline hot spring in the Lower Geyser Basin of Yellowstone National Park. The outflow of BP is characterized by decreasing temperature, increasing pH, increasing dissolved oxygen, decreasing total sulfide, and changing availability of biological nutrients. Microbial life along a 22 m gradient at BP transitions from a 92°C chemotrophic streamer biofilm community in the source pool to a 56°C phototrophic mat community. Coordinated analysis of the BP Environmental Genome and a complementary contextual geochemical dataset of ~75 parameters has revealed biogeochemical cycling and metabolic and microbial community shifts within a hot spring ecosystem (1). In the BP outflow, genes diagnostic for sulfide oxidation, attributed to Aquificales in the chemosynthetic zone and Deinococcus-Thermus at the photosynthetic fringe, decrease in total number downstream. Geochemical data indicate that biological sulfide oxidation, an energy-yielding process in BP, occurs over this same range. While the genetic capacity for sulfate reduction in Thermoproteales at high temperature was found, inorganic sulfate reduction is only minimally energy-yielding at BP suggesting limited activity of these genes. Presence of apr, sat, and dsr genes in the photosynthetic mats may indicate sulfate reduction in micro-niches at depth within the biofilms, perhaps in response to increased availability of organic solutes. Carbon fixation tactics shift downstream in BP as well, as evidenced by the presence of genes associated with specific pathways and carbon isotope ratios. Capacity for the rTCA cycle, attributed to Aquificales and Thermoproteales, and the acetyl co-A pathway are found throughout BP, but are most prevalent in highest temperature sites. At lower temperature sites, fewer total carbon fixation genes were observed

  14. Bark Beetle-Induced Mortality Impacts on Forest Biogeochemical Cycles are Less than Expected

    NASA Astrophysics Data System (ADS)

    Ewers, B. E.; Pendall, E.; Norton, U.; Millar, D.; Mackay, D. S.; Frank, J. M.; Massman, W. J.; Hyde, K.

    2015-12-01

    Bark beetles increased conifer tree mortality across western North America due to past land use interacting with climate change. For both mountain pine and spruce beetles, the mechanism of mortality is hydraulic failure due to xylem occlusion by beetle-carried blue stain fungi, which causes the trees to die from symptoms that are the same as extreme drought. As the mortality event peaked in the last decade, the hypothesized effects on forest biogeochemical processes were 1) lower forest water use from xylem occlusion, 2) less carbon uptake from limited canopy gas exchange, 3) increased nitrogen cycling from increased litterfall and soil moisture and 4) increased streamflow and organic N and C loading at the watershed scale from the first three consequences. The stand-scale effects during mortality were as predicted with transpiration falling by 10-35% in proportion to the occluded xylem, carbon uptake declining by > 50% due to lack of canopy gas exchange and nitrogen cycling increasing from elevated litter inputs and stimulated organic matter decomposition. Some stands, especially mid-elevation lodgepole pine, did not follow these trends because of residual vegetation taking advantage of the increased resources from the dead trees and rapid succession within 5 years of new grasses, shrubs and tree seedlings as well as increased resource use by surviving canopy trees. In a high elevation spruce stand, the lower water use lasted for only three years while summer carbon uptake was only significantly reduced for a year. At the scale of small to medium-sized watersheds, the impact of mortality was not detectable in stream flow due to the spatial and temporal scale muting of the mortality signal as temporal and spatial scales increase. Current ecosystem and watershed models miss these compensating mechanisms with increasing scale and thus over predict the impact of bark beetle mortality.

  15. Genomic reconstruction of novel sediment phyla enlightens roles in sedimentary biogeochemical cycling

    NASA Astrophysics Data System (ADS)

    Baker, B.; Lazar, C.; Seitz, K.; Teske, A.; Hinrichs, K. U.; Dick, G.

    2015-12-01

    Estuaries are among the most productive habitats on the planet. Microbes in estuary sediments control the turnover of organic carbon, and the anaerobic cycling of nitrogen and sulfur. These communities are complex and primarily made up of uncultured lineages, thus little is known about how ecological and metabolic processes are partitioned in sediments. We reconstructed 82 bacterial and 24 archaeal high-quality genomes from different redox regimes (sulfate-rich, sulfate-methane transition zone, and methane-rich zones) of estuary sediments. These bacteria belong to 23 distinct groups, including uncultured candidate phyla (eg. KSB1, TA06, and KD3-62), and three newly described phyla (WOR-1, and -2, and -3). The archaea encompass 8 widespread sediment lineages including MGB-D, RC-III and IV, Z7ME43, Parvarchaeota, Lokiarchoaeta (MBG-B), SAGMEG, Bathyarchaeota (groups MCG-1, -6, -7, and -15) and previously unrecognized deeply branched phylum "Thorarchaeota". The uncultured phyla mediate essential biogeochemical processes of the estuarine environment. Z7ME43 archaea have genes for S disproportionation (S0 reduction and thiosulfate reduction and oxidation). SAGMEG appear to be strict anaerobes capable of coupling CO/H2 oxidation to either S0 or nitrite reduction and have novel RubisCO genes for carbon fixation. Thorarchaeota contain pathways for acetate production from the degradation of detrital proteins and intermediate S cycling. Furthermore, the gene content of this group revealed links in the evolutionary histories of archaea and eukaryotes. This dataset extents our knowledge of the metabolic potential of several uncultured phyla. We were able to chart the flow of carbon and nutrients through the multiple layers of bacterial processing and reveal potential ecological interactions within the communities.

  16. Effects of stratospheric ozone depletion, solar UV radiation, and climate change on biogeochemical cycling: interactions and feedbacks

    SciTech Connect

    Erickson III, David J.; Sulzberger, Barbara; Zepp, Richard G.; Austin, Amy T.

    2014-11-07

    Climate change modulates the effects of solar UV radiation on biogeochemical cycles in terrestrial and aquatic ecosystems, particularly for carbon cycling, resulting in UV-mediated positive or negative feedbacks on climate. Possible positive feedbacks discussed in this assessment include: (i) enhanced UV-induced mineralisation of above ground litter due to aridification; (ii) enhanced UV-induced mineralisation of photoreactive dissolved organic matter (DOM) in aquatic ecosystems due to changes in continental runoff and ice melting; (iii) reduced efficiency of the biological pump due to UV-induced bleaching of coloured dissolved organic matter (CDOM) in stratified aquatic ecosystems, where CDOM protects phytoplankton from the damaging solar UV-B radiation. Mineralisation of organic matter results in the production and release of CO2, whereas the biological pump is the main biological process for CO2 removal by aquatic ecosystems. This research also assesses the interactive effects of solar UV radiation and climate change on the biogeochemical cycling of aerosols and trace gases other than CO2, as well as of chemical and biological contaminants. Lastly,, interacting effects of solar UV radiation and climate change on biogeochemical cycles are particularly pronounced at terrestrial-aquatic interfaces.

  17. Effects of stratospheric ozone depletion, solar UV radiation, and climate change on biogeochemical cycling: interactions and feedbacks

    DOE PAGESBeta

    Erickson III, David J.; Sulzberger, Barbara; Zepp, Richard G.; Austin, Amy T.

    2014-11-07

    Climate change modulates the effects of solar UV radiation on biogeochemical cycles in terrestrial and aquatic ecosystems, particularly for carbon cycling, resulting in UV-mediated positive or negative feedbacks on climate. Possible positive feedbacks discussed in this assessment include: (i) enhanced UV-induced mineralisation of above ground litter due to aridification; (ii) enhanced UV-induced mineralisation of photoreactive dissolved organic matter (DOM) in aquatic ecosystems due to changes in continental runoff and ice melting; (iii) reduced efficiency of the biological pump due to UV-induced bleaching of coloured dissolved organic matter (CDOM) in stratified aquatic ecosystems, where CDOM protects phytoplankton from the damaging solarmore » UV-B radiation. Mineralisation of organic matter results in the production and release of CO2, whereas the biological pump is the main biological process for CO2 removal by aquatic ecosystems. This research also assesses the interactive effects of solar UV radiation and climate change on the biogeochemical cycling of aerosols and trace gases other than CO2, as well as of chemical and biological contaminants. Lastly,, interacting effects of solar UV radiation and climate change on biogeochemical cycles are particularly pronounced at terrestrial-aquatic interfaces.« less

  18. Effects of stratospheric ozone depletion, solar UV radiation, and climate change on biogeochemical cycling: interactions and feedbacks.

    PubMed

    Erickson, David J; Sulzberger, Barbara; Zepp, Richard G; Austin, Amy T

    2015-01-01

    Climate change modulates the effects of solar UV radiation on biogeochemical cycles in terrestrial and aquatic ecosystems, particularly for carbon cycling, resulting in UV-mediated positive or negative feedbacks on climate. Possible positive feedbacks discussed in this assessment include: (i) enhanced UV-induced mineralisation of above ground litter due to aridification; (ii) enhanced UV-induced mineralisation of photoreactive dissolved organic matter (DOM) in aquatic ecosystems due to changes in continental runoff and ice melting; (iii) reduced efficiency of the biological pump due to UV-induced bleaching of coloured dissolved organic matter (CDOM) in stratified aquatic ecosystems, where CDOM protects phytoplankton from the damaging solar UV-B radiation. Mineralisation of organic matter results in the production and release of CO2, whereas the biological pump is the main biological process for CO2 removal by aquatic ecosystems. This paper also assesses the interactive effects of solar UV radiation and climate change on the biogeochemical cycling of aerosols and trace gases other than CO2, as well as of chemical and biological contaminants. Interacting effects of solar UV radiation and climate change on biogeochemical cycles are particularly pronounced at terrestrial-aquatic interfaces. PMID:25380348

  19. Evidence of Microbial Regulation of Biogeochemical Cycles from a Study on Methane Flux and Land Use Change

    PubMed Central

    Nazaries, Loïc; Pan, Yao; Bodrossy, Levente; Baggs, Elizabeth M.; Millard, Peter; Murrell, J. Colin

    2013-01-01

    Microbes play an essential role in ecosystem functions, including carrying out biogeochemical cycles, but are currently considered a black box in predictive models and all global biodiversity debates. This is due to (i) perceived temporal and spatial variations in microbial communities and (ii) lack of ecological theory explaining how microbes regulate ecosystem functions. Providing evidence of the microbial regulation of biogeochemical cycles is key for predicting ecosystem functions, including greenhouse gas fluxes, under current and future climate scenarios. Using functional measures, stable-isotope probing, and molecular methods, we show that microbial (community diversity and function) response to land use change is stable over time. We investigated the change in net methane flux and associated microbial communities due to afforestation of bog, grassland, and moorland. Afforestation resulted in the stable and consistent enhancement in sink of atmospheric methane at all sites. This change in function was linked to a niche-specific separation of microbial communities (methanotrophs). The results suggest that ecological theories developed for macroecology may explain the microbial regulation of the methane cycle. Our findings provide support for the explicit consideration of microbial data in ecosystem/climate models to improve predictions of biogeochemical cycles. PMID:23624469

  20. IIASA`s climate-vegetation-biogeochemical cycle module as a part of an integrated model for climate change

    SciTech Connect

    Ganopolski, A.V.; Jonas, M.; Krabec, J.; Olendrzynski, K.; Petoukhov, V.K.; Venevsky, S.V.

    1994-12-31

    The main objective of this study is the development of a hierarchy of coupled climate biosphere models with a full description of the global biogeochemical cycles. These models are planned for use as the core of a set of integrated models of climate change and they will incorporate the main elements of the Earth system (atmosphere, hydrosphere, pedosphere and biosphere) linked with each other (and eventually with the antroposphere) through the fluxes of heat, momentum, water and through the global biogeochemical cycles of carbon and nitrogen. This set of integrated models can be considered to fill the gap between highly simplified integrated models of climate change and very sophisticated and computationally expensive coupled models, developed on the basis of general circulation models (GCMs). It is anticipated that this range of integrated models will be an effective tool for investigating the broad spectrum of problems connected with the coexistence of human society and biosphere.

  1. Organics in the atmosphere: From air pollution to biogeochemical cycles and climate (Vilhelm Bjerknes Medal)

    NASA Astrophysics Data System (ADS)

    Kanakidou, Maria

    2016-04-01

    Organics are key players in the biosphere-atmosphere-climate interactions. They have also a significant anthropogenic component due to primary emissions or interactions with pollution. The organic pool in the atmosphere is a complex mixture of compounds of variable reactivity and properties, variable content in C, H, O, N and other elements depending on their origin and their history in the atmosphere. Multiphase atmospheric chemistry is known to produce organic acids with high oxygen content, like oxalic acid. This water soluble organic bi-acid is used as indicator for cloud processing and can form complexes with atmospheric Iron, affecting Iron solubility. Organics are also carriers of other nutrients like nitrogen and phosphorus. They also interact with solar radiation and with atmospheric water impacting on climate. In line with this vision for the role of organics in the atmosphere, we present results from a global 3-dimensional chemistry-transport model on the role of gaseous and particulate organics in atmospheric chemistry, accounting for multiphase chemistry and aerosol ageing in the atmosphere as well as nutrients emissions, atmospheric transport and deposition. Historical simulations and projections highlight the human impact on air quality and atmospheric deposition to the oceans. The results are put in the context of climate change. Uncertainties and implications of our findings for biogeochemical and climate modeling are discussed.

  2. Review: Potential catastrophic reduction of sea ice in the western Arctic Ocean: Its impact on biogeochemical cycles and marine ecosystems

    NASA Astrophysics Data System (ADS)

    Harada, Naomi

    2016-01-01

    The reduction of sea ice in the Arctic Ocean, which has progressed more rapidly than previously predicted, has the potential to cause multiple environmental stresses, including warming, acidification, and strengthened stratification of the ocean. Observational studies have been undertaken to detect the impacts on biogeochemical cycles and marine ecosystems of these environmental stresses in the Arctic Ocean. Satellite analyses show that the reduction of sea ice has been especially great in the western Arctic Ocean. Observations and model simulations have both helped to clarify the impact of sea-ice reductions on the dynamics of ecosystem processes and biogeochemical cycles. In this review, I focus on the western Arctic Ocean, which has experienced the most rapid retreat of sea ice in the Arctic Ocean and, very importantly, has a higher rate of primary production than any other area of the Arctic Ocean owing to the supply of nutrient-rich Pacific water. I report the impact of the current reduction of sea ice on marine biogeochemical cycles in the western Arctic Ocean, including lower-trophic-level organisms, and identify the key mechanism of changes in the biogeochemical cycles, based on published observations and model simulations. The retreat of sea ice has enhanced primary production and has increased the frequency of appearance of mesoscale anticyclonic eddies. These eddies enhance the light environment and replenish nutrients, and they also represent a mechanism that can increase the rate of the biological pump in the Arctic Ocean. Various unresolved issues that require further investigation, such as biological responses to environmental stressors such as ocean acidification, are also discussed.

  3. The Importance of Kinetics and Redox in the Biogeochemical Cycling of Iron in the Surface Ocean

    PubMed Central

    Croot, Peter L.; Heller, Maija I.

    2012-01-01

    term impact of this species on iron solubility also with relevance to the euphotic zone. This data highlights the roles of kinetics, redox, and weaker iron binding ligands in the biogeochemical cycling of iron in the ocean. PMID:22723797

  4. Spatial patterns of hyporheic flow and biogeochemical cycling around cross-vane restoration structures

    NASA Astrophysics Data System (ADS)

    Gordon, R. P.; Lautz, L. K.; Daniluk, T.

    2010-12-01

    Natural channel design restoration projects in streams often include the construction of cross-vanes, which are low, stone, dam-like structures that span the active channel. The change in streambed and water elevation over a cross-vane creates a step in static pressure head across the structure. According to modeling studies of similar in-stream structures, this step in head should create a hyporheic flow cell in the streambed many times larger in space than the height of the cross-vane. In such a flow cell, stream water downwells into the streambed upstream of the cross-vane, flows beneath the cross-vane, and upwells back to the surface farther downstream. The purpose of the present study is to determine the extent to which cross-vanes create hyporheic flow cells under field conditions, and to describe the patterns of hyporheic exchange and associated biogeochemical cycling around built structures in restored stream corridors. We chose three cross-vanes in central New York State with different spatial dimensions, and measured heat flux, water exchange, dissolved oxygen, and redox-sensitive solute concentrations in the hyporheic zone surrounding each structure. Streambed temperatures were mapped by inserting a hand-held thermometer to a depth of 7 cm in the bed at 70-to-90 points at each site. Pore water samples were collected from the streambed at approximately 50 in-stream minipiezometers in a meter-scale grid, with 5 cm screens centered at a depth of 15 cm. Temperature was also recorded every 10 minutes for 14 days at several different depths at a subset of points at each site. The time-series temperature data and meter-scale grid temperature measurements were used to calculate vertical water flux rates using an analytical heat transport model. Water samples were analyzed for redox-sensitive nutrients and metals using ion chromatography and ICP-OES. The spatial patterns of water, dissolved oxygen, and solute fluxes that we found are not consistent with a single

  5. Reconstructing paleo-ocean silicon chemistry and ecology during Last Glacial Maximum, a biogeochemical cycle modeling approach

    NASA Astrophysics Data System (ADS)

    Li, D. D.; Lerman, A.; Mackenzie, F. T.

    2012-12-01

    It has been established by a number of investigators that opal content and Si-C isotope studies in the marine sediments reveal information about paleooceanography and the impact on silicic acid utilization by marine autotrophes (diatoms, silicoflagellates) and heterotrophes (radiolarians) during the Last Glacial Maximum (LGM). Opal, as an amorphous form of SiO2, formed by marine Si-secreting organisms, has been used as a proxy to indicate chemical ocean evolution, paleoproductivity and temperature variations in the paleoenvironment and regional ocean water biogeochemical studies, both on million- and thousand-year scales. Here, we are using a model of the global silicon biogeochemical cycle to understand and reconstruct evolutionary history of the paleobiogeochemical cycle and paleoenvironment since LGM. The model is process-driven, temperature-driven, and land-ocean-sediment coupled with specific marine Si-secreting organisms that represent different trophic levels and physiological mechanisms. Specifically, Si utilization by marine silicoflagellates and radiolarians are each about 5% of that of ubiquitous marine diatoms. Available marine reactive Si is controlled by variation of diatom bioproduction that represents 5% of the total marine primary productivity (Si/C Redfield ratio in the marine organic matter is ~0.13, which is an order of magnitude higher than ratio in land organic matter). River input of Si is controlled by chemical weathering of silicate rocks and biocyling of land plant phytoliths. Decreasing dissolved and particulate Si input from land and less favorable climatic condition into LGM diminished the primary production of marine diatoms. However, because radiolarians favor deep-water habitat, where a higher level of DSi is found and that is less affected by temperature changes, a peak of relative abundance is usually observed in sedimentary record during LGM. Given that opal formation fractionated seawater δ30Si (1‰) and enriched seawater with

  6. Natural Organobromine in Marine Sediments: New Evidence of Biogeochemical Br Cycling

    SciTech Connect

    A Leri; J Hakala; M Marcus; A Lanzirotti; C Reddy; S Myneni

    2011-12-31

    Organobromine (Br{sub org}) compounds, commonly recognized as persistent, toxic anthropogenic pollutants, are also produced naturally in terrestrial and marine systems. Several enzymatic and abiotic bromination mechanisms have been identified, as well as an array of natural Br{sub org} molecules associated with various marine organisms. The fate of the carbon-bromine functionality in the marine environment, however, remains largely unexplored. Oceanographic studies have noted an association between bromine (Br) and organic carbon (C{sub org}) in marine sediments. Even so, there has been no direct chemical evidence that Br in the sediments exists in a stable form apart from inorganic bromide (Br{sub inorg}), which is widely presumed conservative in marine systems. To investigate the scope of natural Br{sub org} production and its fate in the environment, we probed Br distribution and speciation in estuarine and marine sediments using in situ X-ray spectroscopy and spectromicroscopy. We show that Br{sub org} is ubiquitous throughout diverse sedimentary environments, occurring in correlation with C{sub org} and metals such as Fe, Ca, and Zn. Analysis of sinking particulate carbon from the seawater column links the Br{sub org} observed in sediments to biologically produced Br{sub org} compounds that persist through humification of natural organic matter (NOM). Br speciation varies with sediment depth, revealing biogeochemical cycling of Br between organic and inorganic forms as part of the burial and degradation of NOM. These findings illuminate the chemistry behind the association of Br with Corg in marine sediments and cast doubt on the paradigmatic classification of Br as a conservative element in seawater systems.

  7. Effects of Past Climate Changes on Ecosystem Biogeochemical Cycles in Rocky Mountain Forests and Lakes

    NASA Astrophysics Data System (ADS)

    Shuman, B.; Mechenich, M. F.; Stefanova, I.; Henderson, A.; Donnelly, J. P.

    2007-12-01

    Ongoing climate trends will likely alter how forest ecosystems produce important goods and services, in part, by changing ecosystem responses to disturbances, such as fires and land-use. Disturbances induce forest succession and thus dramatically change the flow of water and nutrients through a given ecosystem. However, long-term ecosystem responses to disturbance, especially regarding nutrient pools and cycling rates, are poorly documented, and less is known about the effects of century-scale climate trends on these responses especially with respect to moisture. Here, we show biogeochemical responses to repeated (>20) episodes of disturbance and succession in a single ecosystem under a range of climatic conditions over 2000 years. Our lake sediment record shows regular fluctuations in the flux of base cations and other macronutrients from lodgepole pine ( Pinus contorta) forests in northern Colorado following catastrophic stand-replacing fires. Post-fire elemental fluctuations are consistent with ecosystem theory regarding the re-equilibration of biomass and nutrient pools during succession, but show systematic variation that has been previously undocumented. The time span of post-fire re-equilibration correlates positively with measures of fire severity, which is consistent with hypotheses that seed dispersal and soil recovery likely slow re-growth after large or severe fires. Likewise, dry conditions during the Medieval Climatic Anomaly (MCA, 1200-500 yrs BP) altered elemental fluctuations and, thus, generated post-fire pulses of lake eutrophication that were not evident during other periods. The interaction of climate and disturbance, therefore, has important consequences for ecosystem function and services, including the quality of aquatic environments.

  8. How does global biogeochemical cycle become complicated by terrestrial-aquatic interactions ?

    NASA Astrophysics Data System (ADS)

    Nakayama, Tadanobu; Maksyutov, Shamil

    2015-04-01

    Inland water such as river and lake are now known to be important and active components of global carbon cycle though its contribution has remained uncertain due to data scarcity (Battin et al., 2009; Aufdenkampe et al., 2011). The author has developed process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a-b, 2010, 2011a-b, 2012a-c, 2013; Nakayama and Fujita, 2010; Nakayama and Hashimoto, 2011; Nakayama and Shankman, 2013a-b; Nakayama and Watanabe, 2004, 2006, 2008a-b; Nakayama et al., 2006, 2007, 2010, 2012), which incorporates surface-groundwater interactions, includes up- and down-scaling processes between local-global scales, and can simulate iteratively nonlinear feedback between hydrologic, geomorphic, and ecological processes. In this study, NICE was coupled with various biogeochemical models to incorporate biogeochemical cycle including reaction between inorganic and organic carbons (DOC, POC, DIC, pCO2, etc.) in terrestrial and aquatic ecosystems including surface water and groundwater. The coupled model simulated CO2 evasion from inland water in global scale, was relatively in good agreement in that estimated by empirical regression model (Raymond et al., 2013). In particular, the simulated result implied importance of connectivity between terrestrial and aquatic ecosystems in addition to surface and groundwater, and hillslopes and stream channels, etc. The model further improved the accuracy of CH4 flux in wetland which is sensitive to fluctuations of shallow groundwater because the original NICE incorporates 3-D groundwater sub-model and simulates lateral subsurface flow more reasonably. This simulation system would play important role in integration of greenhouse gas budget of the biosphere, quantification of hot spots in boundless biogeochemical cycle, and bridging gap between top-down and bottom-up approaches (Cole et al., 2007; Frei et al., 2012; Kiel and Cardenas, 2014). References; Aufdenkampe, A.K., et al

  9. Iron: A Biogeochemical Engine That Drives Carbon, Nitrogen, and Phosphorus Cycling in Humid Tropical Forest Soils

    NASA Astrophysics Data System (ADS)

    Silver, W. L.; Hall, S. J.; Thompson, A.; Yang, W. H.

    2014-12-01

    rapidly immobilized into biological pools (Liptzin and Silver 2009). Data suggest that Fe-redox cycling may decrease P limitation to NPP, and help maintain forest nutrient stocks. In summary, our results highlight the biogeochemical significance of Fe cycling in upland soils environments and its important role in the dynamics of humid tropical forests.

  10. Timing of the Departure of Ocean Biogeochemical Cycles from the Preindustrial State

    PubMed Central

    Christian, James R.

    2014-01-01

    Changes in ocean chemistry and climate induced by anthropogenic CO2 affect a broad range of ocean biological and biogeochemical processes; these changes are already well underway. Direct effects of CO2 (e.g. on pH) are prominent among these, but climate model simulations with historical greenhouse gas forcing suggest that physical and biological processes only indirectly forced by CO2 (via the effect of atmospheric CO2 on climate) begin to show anthropogenically-induced trends as early as the 1920s. Dates of emergence of a number of representative ocean fields from the envelope of natural variability are calculated for global means and for spatial ‘fingerprints’ over a number of geographic regions. Emergence dates are consistent among these methods and insensitive to the exact choice of regions, but are generally earlier with more spatial information included. Emergence dates calculated for individual sampling stations are more variable and generally later, but means across stations are generally consistent with global emergence dates. The last sign reversal of linear trends calculated for periods of 20 or 30 years also functions as a diagnostic of emergence, and is generally consistent with other measures. The last sign reversal among 20 year trends is found to be a conservative measure (biased towards later emergence), while for 30 year trends it is found to have an early emergence bias, relative to emergence dates calculated by departure from the preindustrial mean. These results are largely independent of emission scenario, but the latest-emerging fields show a response to mitigation. A significant anthropogenic component of ocean variability has been present throughout the modern era of ocean observation. PMID:25386910

  11. Timing of the departure of ocean biogeochemical cycles from the preindustrial state.

    PubMed

    Christian, James R

    2014-01-01

    Changes in ocean chemistry and climate induced by anthropogenic CO2 affect a broad range of ocean biological and biogeochemical processes; these changes are already well underway. Direct effects of CO2 (e.g. on pH) are prominent among these, but climate model simulations with historical greenhouse gas forcing suggest that physical and biological processes only indirectly forced by CO2 (via the effect of atmospheric CO2 on climate) begin to show anthropogenically-induced trends as early as the 1920s. Dates of emergence of a number of representative ocean fields from the envelope of natural variability are calculated for global means and for spatial 'fingerprints' over a number of geographic regions. Emergence dates are consistent among these methods and insensitive to the exact choice of regions, but are generally earlier with more spatial information included. Emergence dates calculated for individual sampling stations are more variable and generally later, but means across stations are generally consistent with global emergence dates. The last sign reversal of linear trends calculated for periods of 20 or 30 years also functions as a diagnostic of emergence, and is generally consistent with other measures. The last sign reversal among 20 year trends is found to be a conservative measure (biased towards later emergence), while for 30 year trends it is found to have an early emergence bias, relative to emergence dates calculated by departure from the preindustrial mean. These results are largely independent of emission scenario, but the latest-emerging fields show a response to mitigation. A significant anthropogenic component of ocean variability has been present throughout the modern era of ocean observation. PMID:25386910

  12. Modeling the Natural Biogeochemical Cycle of Mercury in the Global Ocean

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Jaegle, L.; Thompson, L.; Emerson, S. R.; Deutsch, C. A.; Trossman, D. S.; Shao, A.

    2012-12-01

    The ocean plays an important role in the biogeochemical cycling of mercury (Hg) because of its large reservoir mass and re-emission flux via evasion. The currently available Hg models, including 2D slab, 1D column and 0D box model cannot fully resolve the marine Hg cycle because of the lack of the proper spatial resolution. In this work, we have implemented Hg biogeochemistry in a state-of-the-art 3D offline ocean tracer model (OFFTRAC). OFFTRAC simulates the evolution of three Hg species (Hg0aq, HgIIaq and HgPaq), which are diffused and advected in the ocean. Hg0aq and HgII aq are interconverted in the surface ocean via parameterized photochemical and biological redox processes. The partitioning between HgIIaq and HgPaq depends on the local levels of particulate organic carbon (POC). The sinking of HgPaq is parameterized by coupling with the nutrient phosphorous cycle simulated in OFFTRAC. The reduction of HgIIaq to Hg0aq in the anaerobic subsurface water is proportional to the remineralizaiton of POC. OFFTRAC is coupled to a global simulation of the natural atmospheric Hg cycle in the GEOS-Chem chemical transport model. The GEOS-Chem simulation includes a geogenic source and provides the atmospheric deposition flux of HgII to the ocean and atmospheric Hg0 concentrations. The riverine input of Hg is calculated based on the climatological monthly mean fresh water discharge from continental to ocean and the average soil concentrations near the river mouth. The results show that the riverine input enhances Hg concentrations at surface by a factor of 2-3 near large river mouths and nearby coastal regions. The riverine input approximately doubles surface Hg concentration over the Arctic because of the small basin volume. In the deep ocean, which is not influenced by anthropogenic emissions, the model results (1.1±0.3 pM) generally agree with the observed present-day total Hg concentration profiles (1.4±0.9 pM). In the surface ocean, observations show average total Hg

  13. The MIRACLE Project: An integrated approach to understanding biogeochemical cycling of mercury and its relationship with lagoon clam farming

    NASA Astrophysics Data System (ADS)

    Covelli, Stefano

    2012-11-01

    The "MIRACLE" Project was aimed at two specific issues: understanding Hg biogeochemical cycling in the Marano and Grado Lagoon and testing the coexistence of clam farming with Hg contamination in the sediments. Mercury contamination was measured in several matrices (water, sediment, biota) and its mobility was tested along with its speciation in relation to biogeochemical processes occurring in the lagoon environment, where bacterial communities have a primary role in converting Hg to its more toxic form, methylmercury (MeHg). Bioaccumulation of the Hg species was investigated on natural and seeded clams (Ruditapes philippinarum), the most important commercial bivalves in the Lagoon. The Editorial summarizes the main results obtained from this multidisciplinary study and reported in the Special Issue.

  14. Integrating biorefinery and farm biogeochemical cycles offsets fossil energy and mitigates soil carbon losses.

    PubMed

    Adler, Paul R; Mitchell, James G; Pourhashem, Ghasideh; Spatari, Sabrina; Del Grosso, Stephen J; Parton, William J

    2015-06-01

    Crop residues are potentially significant sources of feedstock for biofuel production in the United States. However, there are concerns with maintaining the environmental functions of these residues while also serving as a feedstock for biofuel production. Maintaining soil organic carbon (SOC) along with its functional benefits is considered a greater constraint than maintaining soil erosion losses to an acceptable level. We used the biogeochemical model DayCent to evaluate the effect of residue removal, corn stover, and wheat and barley straw in three diverse locations in the USA. We evaluated residue removal with and without N replacement, along with application of a high-lignin fermentation byproduct (HLFB), the residue by-product comprised of lignin and small quantities of nutrients from cellulosic ethanol production. SOC always decreased with residue harvest, but the decrease was greater in colder climates when expressed on a life cycle basis. The effect of residue harvest on soil N2O emissions varied with N addition and climate. With N addition, N2O emissions always increased, but the increase was greater in colder climates. Without N addition, N2O emissions increased in Iowa, but decreased in Maryland and North Carolina with crop residue harvest. Although SOC was lower with residue harvest when HLFB was used for power production instead of being applied to land, the avoidance of fossil fuel emissions to the atmosphere by utilizing the cellulose and hemicellulose fractions of crop residue to produce ethanol (offsets) reduced the overall greenhouse gas (GHG) emissions because most of this residue carbon would normally be lost during microbial respiration. Losses of SOC and reduced N mineralization could both be mitigated with the application of HLFB to the land. Therefore, by returning the high-lignin fraction of crop residue to the land after production of ethanol at the biorefinery, soil carbon levels could be maintained along with the functional benefit of

  15. Biogeochemical cycle of Mercury in an urban stream in Hartford CT

    NASA Astrophysics Data System (ADS)

    Aragon-jose, A. T.; Bushey, J. T.; Perkins, C.; Mendes, M.; Ulatowski, G.

    2012-12-01

    Mercury (Hg) toxicity and the potential for bioaccumulation in the food chain result in exposure risk even at low Hg levels. The presence of urban activities can substantially alter Hg fate and transport mechanisms and Hg biogeochemical cycles. Urban watersheds are characterized by high imperviousness and some may even be impacted by combined sewer overflows, both being fundamental factors contributing to Hg loading, mobilization, and shifts in bioavailability in urban watersheds. Research is still needed to characterize the fate and dynamics of Hg in urban streams. To address this gap in knowledge, we collected and characterized stream water and suspended sediment samples in the Park River watershed in Hartford, CT (USA) during baseflow and precipitation events. Sampling sites were selected across an urbanization gradient. Water samples are analyzed for total, dissolved, and particulate Hg and methyl Hg (MeHg), major ions (Cl-, NO3-, SO42-)-, total suspended solids (TSS), and dissolved organic carbon (DOC). Our results show that both total and dissolved Hg concentrations increase in the streams during precipitation events, however, the greatest portion of Hg is associated, and consequently transported, with suspended sediments, as suggested by the high correlation coefficient (R2 ~ 0.80) between TSS and total Hg. No significant correlation was observed between dissolved or total Hg and DOC, contrary to the observations in forested systems, which indicates that the sources and mechanisms governing mobilization and transport of dissolved Hg in an urban watershed differ from those at forested systems. However, during select events, a significant portion of Hg flux occurs in the dissolved phase. Unfiltered MeHg samples exhibited a similar pattern relative to the hydrograph to that of total Hg. Concentrations increase during the rising limb with TSS followed by a decrease as the storm progresses. Dissolved MeHg is mostly below our detection limit. Area normalized THg

  16. Improvement of wine terroir management according to biogeochemical cycle of nitrogen in soil

    NASA Astrophysics Data System (ADS)

    Najat, Nassr; Aude, Langenfeld; Mohammed, Benbrahim; Lionel, Ley; Laurent, Deliere; Jean-Pascal, Goutouly; David, Lafond; Marie, Thiollet-Scholtus

    2015-04-01

    Good wine terroir production implies a well-balanced Biogeochemical Cycle of Nitrogen (BCN) at field level i.e. in soil and in plant. Nitrogen is very important for grape quality and soil sustainability. The mineralization of organic nitrogen is the main source of mineral nitrogen for the vine. This mineralization depends mainly on the soil microbial activity. This study is focused on the functional microbial populations implicated in the BCN, in particular nitrifying bacteria. An experimental network with 6 vine sites located in Atlantic coast (Loire valley and Bordeaux) and in North-East (Alsace) of France has been set up since 2012. These vine sites represent a diversity of environmental factors (i.e. soil and climate). The adopted approach is based on the measure of several indicators to assess nitrogen dynamic in soil, i.e. nitrogen mineralization, regarding microbial biomass and activity. Statistical analyses are performed to determine the relationship between biological indicator and nitrogen mineralisation regarding farmer's practices. The variability of the BCN indicators seems to be correlated to the physical and chemical parameters in the soil of the field. For all the sites, the bacterial biomass is correlated to the rate and kinetic of nitrogen in soil, however this bioindicator depend also on others parameters. Moreover, the functional bacterial diversity depends on the soil organic matter content. Differences in the bacterial biomass and kinetic of nitrogen mineralization are observed between the sites with clayey (Loire valley site) and sandy soils (Bordeaux site). In some tested vine systems, effects on bacterial activity and nitrogen dynamic are also observed depending on the farmer's practices: soil tillage, reduction of inputs, i.e. pesticides and fertilizers, and soil cover management between rows. The BCN indicators seem to be strong to assess the dynamics of the nitrogen in various sites underline the functional diversity of the soils. These

  17. Stabilization of dissolved trace metals at hydrothermal vent sites: Impact on their marine biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Sander, Sylvia G.; Powell, Zach D.; Koschinsky, Andrea; Kuzmanovski, Stefan; Kleint, Charlotte

    2014-05-01

    Hydrothermal vents have long been neglected as a significant source of several bioactive trace metals as it was assumed that elements such as Fe, Mn, and Cu etc., precipitate in extensor forming poly-metallic sulfide and oxy-hydroxy sediments in the relative vicinity of the emanation site. However, recently this paradigm has been reviewed since the stabilization of dissolved Fe and Cu from hydrothermal vents was observed [1, 2] and increased concentrations of trace metals can be traced from their hydrothermal source thousands of kilometres through the ocean basins [3]. Furthermore several independent modelling attempts have shown that not only a stabilization of dissolved hydrothermal Fe and Cu is possible [4] but also that hydrothermalism must be a significant source of Fe to be able to balance the Fe-biogeochemical cycle [5]. Here we present new data that gives further evidence of the presence of copper stabilising organic and inorganic compounds in samples characterized by hydrothermal input. We can show that there are systematic differences in copper-complexing ligands at different vent sites such as 5°S on the Mid Atlantic Ridge, Brother Volcano on the Kermadec Arc, and some shallow hydrothermal CO2 seeps in the Bay of Plenty, New Zealand and the Mediterranean Sea. Quantitative and qualitative voltammetric data convincingly indicates that inorganic sulphur and organic thiols form the majority of the strong copper-complexing ligand pool in many of these hydrothermal samples. On average, the high temperature vents had a significantly higher copper binding capacity than the diffuse vents due to higher inorganic sulphur species concentrations. References: [1] Sander, S. G., et al. 2007. Organic complexation of copper in deep-sea hydrothermal vent systems. Environmental Chemistry 4: 81-89 [2] Bennett, S. A., et al. 2008. The distribution and stabilisation of dissolved Fe in deep-sea hydrothermal plumes. Earth and Planetary Science Letters 270: 157-167. [3] Wu J

  18. Final Project Report: "Exploratory Research: Mercury Stable Isotopes as Indicators of the Biogeochemical Cycling of Mercury"

    SciTech Connect

    Johnson, Thomas M

    2012-08-01

    This is the final project report for award DE-SC0005351, which supported the research project "Exploratory Research: Mercury Stable Isotopes as Indicators of the Biogeochemical Cycling of Mercury. "This exploratory project investigated the use of mercury (Hg) stable isotope measurements as a new approach to study how Hg moves and changes its chemical form in environmental systems, with particular focus on the East Fork of Poplar Creek (EFPC) near the DOE Y-12 plant (a Hg contamination source). This study developed analytical methods and collected pilot data that have set the stage for more detailed studies and have begun to provide insights into Hg movement and chemical changes. The overall Hg stable isotope approach was effective. The Hg isotope analysis methods yielded high-precision measurements of the sediment, water, and fish samples analyzed; quality control measures demonstrated the precision. The pilot data show that the 202Hg/198Hg, 199Hg/198Hg, and 201Hg/198Hg isotope ratios vary in this system. 202Hg/198Hg ratios of the Hg released from the Y-12 plant are relatively high, and those of the regional Hg background in soils and river sediments are significantly lower. Unfortunately, 202Hg/198Hg differences that might have been useful to distinguish early Hg releases from later releases were not observed. However, 202Hg/198Hg ratios in sediments do provide insights into chemical transformations that may occur as Hg moves through the system. Furthermore, 199Hg/198Hg and 201Hg/198Hg ratio analyses of fish tissues indicate that the effects of sunlight-driven chemical reactions on the Hg that eventually ends up in EFPC fish are measureable, but small. These results provide a starting point for a more detailed study (already begun at Univ. of Michigan) that will continue Hg isotope ratio work aimed at improving understanding of how Hg moves, changes chemically, and does or does not take on more highly toxic forms in the Oak Ridge area. This work also benefits

  19. Impact of phytoplankton on the biogeochemical cycling of iron in subantarctic waters southeast of New Zealand during FeCycle

    NASA Astrophysics Data System (ADS)

    McKay, R. M. L.; Wilhelm, S. W.; Hall, J.; Hutchins, D. A.; Al-Rshaidat, M. M. D.; Mioni, C. E.; Pickmere, S.; Porta, D.; Boyd, P. W.

    2005-12-01

    During austral summer 2003, we tracked a patch of surface water infused with the tracer sulfur hexafluoride, but without addition of Fe, through subantarctic waters over 10 days in order to characterize and quantify algal Fe pools and fluxes to construct a detailed biogeochemical budget. Nutrient profiles characterized this patch as a high-nitrate, low-silicic acid, low-chlorophyll (HNLSiLC) water mass deficient in dissolved Fe. The low Fe condition was confirmed by several approaches: shipboard iron enrichment experiments and physiological indices of Fe deficiency (Fv/Fm < 0.25, Ferredoxin Index < 0.2). During FeCycle, picophytoplankton (0.2-2 μm) and nanophytoplankton (2-20 μm) each contributed >40% of total chlorophyll. Whereas the picophytoplankton accounted for ˜50% of total primary production, they were responsible for the majority of community iron uptake in the mixed layer. Thus ratios of 55Fe:14C uptake were highest for picophytoplankton (median: 17 μmol:mol) and declined to ˜5 μmol:mol for the larger algal size fractions. A pelagic Fe budget revealed that picophytoplankton were the largest pool of algal Fe (>90%), which was consistent with the high (˜80%) phytoplankton Fe demand attributed to them. However, Fe regenerated by herbivory satisfied only ˜20% of total algal Fe demand. This iron regeneration term increased to 40% of algal Fe demand when we include Fe recycled by bacterivory. As recycled, rather than new, iron dominated the pelagic iron budget (Boyd et al., 2005), it is highly unlikely that the supply of new Fe would redress the imbalance between algal Fe demand and supply. Reasons for this imbalance may include the overestimation of algal iron uptake from radiotracer techniques, or a lack of consideration of other iron regeneration processes. In conclusion, it seems that algal Fe uptake cannot be supported solely by the recycling of algal iron, and may require an Fe "subsidy" from that regenerated by heterotrophic pathways.

  20. Coupled biogeochemical cycles in riparian zones with contrasting hydrogeomorphic characteristics in the US Midwest

    NASA Astrophysics Data System (ADS)

    Liu, X.

    2012-12-01

    In this study we aims to understand what drives the fate and transport of multiple contaminants sensitive to soil redox condition across hydrogeomorphic (HGM) gradient and evaluate overall biogeochemical functions of riparian zones regarding those contaminants. We conducted monthly field work for 19 consecutive months from November 2009 to May 2011 at three study sites representative for main HGM types at the US Midwest. We collected the parameters from different sources which include field parameters, such as topography, water table depth, oxidation reduction potential (ORP) and dissolved oxygen (DO), and groundwater chemistry, such as NH4+, NO3-, PO43-, SO42-, CI- , and Hg and MeHg. Our results demonstrated that seasonal water table fluctuations and groundwater flows characteristics at three sites are strongly affected by their HGM setting. Specifically, the convergence of quick rise of water table, high ORP and sharp decrease in concentrations of NO3- and SO42 from field edge to stream edge (60-90% at LWD and 90% at WR) in spring after snowmelt and early May, which could be explained by that snow melt and early summer rainfall are major drivers of fluctuations of water table, variations of ORP and transport and transformation of contaminants. Riparian zones removed NO3- and SO42- during high water table but released Mercury in summer at both LWD and WR, and sulfate reduction, ammonia production and MeHg production all occurred when ORP and water tables were low in summer. These results might reflect the strong ORP control on these processes at landscape scale. These findings supported our hypothesis. Other findings however contrast to our hypothesis. For instances, unusual high concentrations of nitrate and Hg at WR suggest that the transport and fate of multiple contaminants relate not only to HGM settings but geographic location and land use. Negligible variations of P concentration in groundwater indicate that the transformation of P is not sensitive to soil

  1. Biogeochemical and hydrologic processes controlling mercury cycling in Great Salt Lake, Utah

    NASA Astrophysics Data System (ADS)

    Naftz, D.; Kenney, T.; Angeroth, C.; Waddell, B.; Darnall, N.; Perschon, C.; Johnson, W. P.

    2006-12-01

    Great Salt Lake (GSL), in the Western United States, is a terminal lake with a highly variable surface area that can exceed 5,100 km2. The open water and adjacent wetlands of the GSL ecosystem support millions of migratory waterfowl and shorebirds from throughout the Western Hemisphere, as well as a brine shrimp industry with annual revenues exceeding 70 million dollars. Despite the ecologic and economic significance of GSL, little is known about the biogeochemical cycling of mercury (Hg) and no water-quality standards currently exist for this system. Whole water samples collected since 2000 were determined to contain elevated concentrations of total Hg (100 ng/L) and methyl Hg (33 ng/L). The elevated levels of methyl Hg are likely the result of high rates of SO4 reduction and associated Hg methylation in persistently anoxic areas of the lake at depths greater than 6.5 m below the water surface. Hydroacoustic equipment deployed in this anoxic layer indicates a "conveyor belt" flow system that can distribute methyl Hg in a predominantly southerly direction throughout the southern half of GSL (fig. 1, URL: http://users.o2wire.com/dnaftz/Dave/AGU-abs-figs- AUG06.pdf). Periodic and sustained wind events on GSL may result in transport of the methyl Hg-rich anoxic water and bottom sediments into the oxic and biologically active regions. Sediment traps positioned above the anoxic brine interface have captured up to 6 mm of bottom sediment during cumulative wind-driven resuspension events (fig. 2, URL:http://users.o2wire.com/dnaftz/Dave/AGU-abs-figs-AUG06.pdf). Vertical velocity data collected with hydroacoustic equipment indicates upward flow > 1.5 cm/sec during transient wind events (fig. 3, URL:http://users.o2wire.com/dnaftz/Dave/AGU-abs-figs-AUG06.pdf). Transport of methyl Hg into the oxic regions of GSL is supported by biota samples. The median Hg concentration (wet weight) in brine shrimp increased seasonally from the spring to fall time period and is likely a

  2. Biogeochemical cycling of cadmium isotopes in the Southern Ocean along the Zero Meridian

    NASA Astrophysics Data System (ADS)

    Abouchami, W.; Galer, S. J. G.; de Baar, H. J. W.; Middag, R.; Vance, D.; Zhao, Y.; Klunder, M.; Mezger, K.; Feldmann, H.; Andreae, M. O.

    2014-02-01

    isotope fractionation and Zn availability in the contrasted nutrient and ecological regimes of the Southern Ocean. Substitution of Cd for Zn in the enzyme carbonic anhydrase appears to be the driving mechanism for Cd isotope fractionation in the Antarctic Circumpolar Current, while an “excess-uptake” mechanism seems to predominate in the Weddell Gyre. Our study highlights some of the complexities of the biogeochemical cycling of Cd in the oceans. Nevertheless, systematic variations in Cd isotopic compositions with water mass distribution in the Southern Ocean suggest that Cd isotopes could, with some caveats, be useful tracers of changes in past nutrient utilization and deep water circulation.

  3. Assessment of diel chemical and isotopic techniques to investigate biogeochemical cycles in the upper Klamath River, Oregon, USA

    USGS Publications Warehouse

    Poulson, S.R.; Sullivan, A.B.

    2009-01-01

    The upper Klamath River experiences a cyanobacterial algal bloom and poor water quality during the summer. Diel chemical and isotopic techniques have been employed in order to investigate the rates of biogeochemical processes. Four diel measurements of field parameters (temperature, pH, dissolved oxygen concentrations, and alkalinity) and stable isotope compositions (dissolved oxygen-??18O and dissolved inorganic carbon-??13C) have been performed between June 2007 and August 2008. Significant diel variations of pH, dissolved oxygen (DO) concentration, and DO-??18O were observed, due to varying rates of primary productivity vs. respiration vs. gas exchange with air. Diel cycles are generally similar to those previously observed in river systems, although there are also differences compared to previous studies. In large part, these different diel signatures are the result of the low turbulence of the upper Klamath River. Observed changes in the diel signatures vs. sampling date reflect the evolution of the status of the algal bloom over the course of the summer. Results indicate the potential utility of applying diel chemical and stable isotope techniques to investigate the rates of biogeochemical cycles in slow-moving rivers, lakes, and reservoirs, but also illustrate the increased complexity of stable isotope dynamics in these low-turbulence systems compared to well-mixed aquatic systems. ?? 2009 Elsevier B.V.

  4. Quantifying Biogeochemical Cycles of CO2 and CH4 over the Land and Aquatic Ecosystems in Northern Eurasia

    NASA Astrophysics Data System (ADS)

    Zhuang, Q.

    2015-12-01

    Under the auspices of the NASA Land-Use and Land-Cover Change Program, we have made a significant progress on quantifying both CO2 and CH4 biogeochemical cycles of the land and aquatic systems in Northern Eurasia over the last several decades. Our quantification is based on in situ and satellite data of ecosystem distribution, land cover distribution, carbon, water and energy fluxes, fire disturbances, plant biomass inventory, atmospheric CO2 and CH4, and meteorology. The evaluated process-based modeling systems for both land and aquatic ecosystems for the historical period have been used to project carbon fluxes during the 21st century over this region. The uncertainty associated with these carbon-based gases is also quantified. This presentation will update these quantifications by examining: 1) the impacts of fire disturbances on land ecosystem CO2 budget in the last few decades; 2) net CO2 and CH4 exchanges of the land and aquatic ecosystems in both historical and future periods. Our study has also assessed the role of permafrost dynamics in both land and aquatic ecosystem carbon and water dynamics in this region. Our research provides an integrated land and aquatic ecosystem model that can be used to address biogeochemical cycles of carbon and water in this climate-sensitive region.

  5. Effects of Climate-Induced Hydrologic Modifications on Biogeochemical Cycling of Trace Metals in Alluvial and Coastal Watersheds

    NASA Astrophysics Data System (ADS)

    Lee, M.; Natter, M. G.; Keevan, J. P.; Guerra, K.; Saunders, J.; Uddin, A.; Humayun, M.; Wang, Y.; Keimowitz, A. R.

    2013-12-01

    Assessing the impacts of climate changes on water quality requires an understanding of the biogeochemical cycling of trace metals. Evidence from research on alluvial aquifers and coastal watersheds shows direct impacts of climate change on the fate and transformation of trace metals in natural environments. This study employs field data and numerical modeling techniques to test assumptions about the effects of climate change on natural arsenic contamination of groundwater in alluvial aquifers and mercury bioaccumulation in coastal saltmarshes. The results show that the rises of sea level and river base during the warm Holocene period has led to an overall increase in groundwater arsenic concentration due to the development of reducing geochemical conditions and sluggish groundwater movement. Modeling results indicate that the intrusion of seawater occurring during high sea-level stand may lead to desorption of arsenic from the surfaces of hydrous oxides due to pH effects and ionic competition for mineral sorbing sites. Our results also show that contamination and bioaccumulation of Hg and other metals in estuarine and coastal ecosystems may be influenced by climate-induced hydrologic modifications (atmospheric deposition, riverine input, salinity level, etc.). An integrated research framework consisting of numerical modeling, long-term monitoring, laboratory experiments will be necessary for building a comprehensive understanding of the complex response of biogeochemical cycling of trace metals to climate change.

  6. Red waters of Myrionecta rubra are biogeochemical hotspots for the Columbia River estuary with impacts on primary/secondary productions and nutrient cycles

    SciTech Connect

    Herfort, Lydie; Peterson, Tawnya D.; Prahl, Fredrick G.; McCue, Lee Ann; Needoba, Joe A.; Crump, Byron C.; Roegner, G. Curtis; Campbell, Victoria; Zuber, Peter A.

    2012-02-29

    The localized impact of blooms of the mixotrophic ciliate Myrionecta rubra in the Columbia River estuary during 2007-2010 was evaluated with biogeochemical, light microscopy, physiological and molecular data. M. rubra affected surrounding estuarine nutrient cycles, as indicated by high and low concentrations of organic nutrients and inorganic nitrogen, respectively, associated with red waters. M. rubra blooms also altered the energy transfer pattern in patches of the estuarine water that contain the ciliate by creating areas characterized by high primary production and elevated levels of fresh autochthonous particulate organic matter, therefore shifting the trophic status in emergent red water areas of the estuary from net heterotrophy towards autotrophy. The pelagic estuarine bacterial community structure was unaffected by M. rubra abundance, but red waters of the ciliate do offer a possible link between autotrophic and heterotrophic processes since they were associated with elevated dissolved organic matter and enhanced microbial secondary production. Taken together these findings suggest that M. rubra red waters are biogeochemical hotspots of the Columbia River estuary.

  7. Molecular and biogeochemical evidence for methane cycling beneath the western margin of the Greenland Ice Sheet

    PubMed Central

    Dieser, Markus; Broemsen, Erik L J E; Cameron, Karen A; King, Gary M; Achberger, Amanda; Choquette, Kyla; Hagedorn, Birgit; Sletten, Ron; Junge, Karen; Christner, Brent C

    2014-01-01

    Microbial processes that mineralize organic carbon and enhance solute production at the bed of polar ice sheets could be of a magnitude sufficient to affect global elemental cycles. To investigate the biogeochemistry of a polar subglacial microbial ecosystem, we analyzed water discharged during the summer of 2012 and 2013 from Russell Glacier, a land-terminating outlet glacier at the western margin of the Greenland Ice Sheet. The molecular data implied that the most abundant and active component of the subglacial microbial community at these marginal locations were bacteria within the order Methylococcales (59–100% of reverse transcribed (RT)-rRNA sequences). mRNA transcripts of the particulate methane monooxygenase (pmoA) from these taxa were also detected, confirming that methanotrophic bacteria were functional members of this subglacial ecosystem. Dissolved methane ranged between 2.7 and 83 μM in the subglacial waters analyzed, and the concentration was inversely correlated with dissolved oxygen while positively correlated with electrical conductivity. Subglacial microbial methane production was supported by δ13C-CH4 values between −64‰ and −62‰ together with the recovery of RT-rRNA sequences that classified within the Methanosarcinales and Methanomicrobiales. Under aerobic conditions, >98% of the methane in the subglacial water was consumed over ∼30 days incubation at ∼4 °C and rates of methane oxidation were estimated at 0.32 μM per day. Our results support the occurrence of active methane cycling beneath this region of the Greenland Ice Sheet, where microbial communities poised in oxygenated subglacial drainage channels could serve as significant methane sinks. PMID:24739624

  8. Enhanced biogeochemical cycling and subsequent reduction of hydraulic conductivity associated with soil-layer interfaces in the vadose zone.

    PubMed

    Hansen, David J; McGuire, Jennifer T; Mohanty, Binayak P

    2011-01-01

    Biogeochemical dynamics in the vadose zone are poorly understood due to the transient nature of chemical and hydrologic conditions but are nonetheless critical to understanding chemical fate and transport. This study explored the effects of a soil layer on linked geochemical, hydrological, and microbiological processes. Three laboratory soil columns were constructed: a homogenized medium-grained sand, a homogenized organic-rich loam, and a sand-over-loam layered column. Upward and downward infiltration of water was evaluated during experiments to simulate rising water table and rainfall events, respectively. In situ collocated probes measured soil water content, matric potential, and Eh. Water samples collected from the same locations were analyzed for Br, Cl, NO, SO, NH, Fe, and total sulfide. Compared with homogeneous columns, the presence of a soil layer altered the biogeochemistry and water flow of the system considerably. Enhanced biogeochemical cycling was observed in the layered column over the texturally homogeneous soil columns. Enumerations of iron- and sulfate-reducing bacteria showed 1 to 2 orders of magnitude greater community numbers in the layered column. Mineral and soil aggregate composites were most abundant near the soil-layer interface, the presence of which likely contributed to an observed order-of-magnitude decrease in hydraulic conductivity. These findings show that quantifying coupled hydrologic-biogeochemical processes occurring at small-scale soil interfaces is critical to accurately describing and predicting chemical changes at the larger system scale. These findings also provide justification for considering soil layering in contaminant fate and transport models because of its potential to increase biodegradation or to slow the rate of transport of contaminants. PMID:22031578

  9. Enhanced biogeochemical cycling and subsequent reduction of hydraulic conductivity associated with soil-layer interfaces in the vadose zone

    PubMed Central

    Hansen, David J.; McGuire, Jennifer T.; Mohanty, Binayak P.

    2013-01-01

    Biogeochemical dynamics in the vadose zone are poorly understood due to the transient nature of chemical and hydrologic conditions, but are nonetheless critical to understanding chemical fate and transport. This study explored the effects of a soil layer on linked geochemical, hydrological, and microbiological processes. Three laboratory soil columns were constructed: a homogenized medium-grained sand, a homogenized organic-rich loam, and a sand-over-loam layered column. Upward and downward infiltration of water was evaluated during experiments to simulate rising water table and rainfall events respectively. In-situ collocated probes measured soil water content, matric potential, and Eh while water samples collected from the same locations were analyzed for Br−, Cl−, NO3−, SO42−, NH4+, Fe2+, and total sulfide. Compared to homogenous columns, the presence of a soil layer altered the biogeochemistry and water flow of the system considerably. Enhanced biogeochemical cycling was observed in the layered column over the texturally homogeneous soil columns. Enumerations of iron and sulfate reducing bacteria showed 1-2 orders of magnitude greater community numbers in the layered column. Mineral and soil aggregate composites were most abundant near the soil-layer interface; the presence of which, likely contributed to an observed order-of-magnitude decrease in hydraulic conductivity. These findings show that quantifying coupled hydrologic-biogeochemical processes occurring at small-scale soil interfaces is critical to accurately describing and predicting chemical changes at the larger system scale. Findings also provide justification for considering soil layering in contaminant fate and transport models because of its potential to increase biodegradation and/or slow the rate of transport of contaminants. PMID:22031578

  10. Simulating anchovy's full life cycle in the northern Aegean Sea (eastern Mediterranean): A coupled hydro-biogeochemical-IBM model

    NASA Astrophysics Data System (ADS)

    Politikos, D.; Somarakis, S.; Tsiaras, K. P.; Giannoulaki, M.; Petihakis, G.; Machias, A.; Triantafyllou, G.

    2015-11-01

    A 3-D full life cycle population model for the North Aegean Sea (NAS) anchovy stock is presented. The model is two-way coupled with a hydrodynamic-biogeochemical model (POM-ERSEM). The anchovy life span is divided into seven life stages/age classes. Embryos and early larvae are passive particles, but subsequent stages exhibit active horizontal movements based on specific rules. A bioenergetics model simulates the growth in both the larval and juvenile/adult stages, while the microzooplankton and mesozooplankton fields of the biogeochemical model provide the food for fish consumption. The super-individual approach is adopted for the representation of the anchovy population. A dynamic egg production module, with an energy allocation algorithm, is embedded in the bioenergetics equation and produces eggs based on a new conceptual model for anchovy vitellogenesis. A model simulation for the period 2003-2006 with realistic initial conditions reproduced well the magnitude of population biomass and daily egg production estimated from acoustic and daily egg production method (DEPM) surveys, carried out in the NAS during June 2003-2006. Model simulated adult and egg habitats were also in good agreement with observed spatial distributions of acoustic biomass and egg abundance in June. Sensitivity simulations were performed to investigate the effect of different formulations adopted for key processes, such as reproduction and movement. The effect of the anchovy population on plankton dynamics was also investigated, by comparing simulations adopting a two-way or a one-way coupling of the fish with the biogeochemical model.

  11. Integrating 'omic' data and biogeochemical modeling: the key to understanding the microbial regulation of matter cycling in soil

    NASA Astrophysics Data System (ADS)

    Pagel, Holger; Kandeler, Ellen; Seifert, Jana; Camarinha-Silva, Amélia; Kügler, Philipp; Rennert, Thilo; Poll, Christian; Streck, Thilo

    2016-04-01

    Matter cycling in soils and associated soil functions are intrinsically controlled by microbial dynamics. It is therefore crucial to consider functional traits of microorganisms in biogeochemical models. Tremendous advances in 'omic' methods provide a plethora of data on physiology, metabolic capabilities and ecological life strategies of microorganisms in soil. Combined with isotopic techniques, biochemical pathways and transformations can be identified and quantified. Such data have been, however, rarely used to improve the mechanistic representation of microbial dynamics in soil organic matter models. It is the goal of the Young Investigator Group SoilReg to address this challenge. Our general approach is to tightly integrate experiments and biochemical modeling. NextGen sequencing will be applied to identify key functional groups. Active microbial groups will be quantified by measurements of functional genes and by stable isotope probing methods of DNA and proteins. Based on this information a biogeochemical model that couples a mechanistic representation of microbial dynamics with physicochemical processes will be set up and calibrated. Sensitivity and stability analyses of the model as well as scenario simulations will reveal the importance of intrinsic and extrinsic controls of organic matter turnover. We will demonstrate our concept and present first results of two case studies on pesticide degradation and methane oxidation.

  12. Linking Nitrogen-Cycling Microbial Communities to Environmental Fluctuations and Biogeochemical Activity in a Large, Urban Estuary: the San Francisco Bay-Delta

    NASA Astrophysics Data System (ADS)

    Francis, C.

    2015-12-01

    Nitrogen (N) availability is an important factor controlling productivity and thus carbon cycling in estuaries. The fate of N in estuaries depends on the activities of the microbes that carry out the N-cycle, which in turn depend on factors such as organic matter availability, dissolved inorganic N, salinity, oxygen, and temperature. Key microbial N transformations include nitrification (the aerobic oxidation of ammonia to nitrite and nitrate) and denitrification (the anaerobic reduction of nitrate to dinitrogen gas). While denitrification leads to N loss, nitrification is the only link between reduced N (produced by decomposition) and oxidized N (substrates for N loss processes), and both processes are known to produce nitrous oxide (N2O), a potent greenhouse gas. Understanding controls of N-cycling in the San Francisco Bay-Delta (SFBD)—the largest estuary on the west coast of North America—is particularly important, as this urban estuary is massively polluted with N, even compared to classic "eutrophic" systems. Interestingly, the SFBD has been spared the detrimental consequences of nutrient enrichment, largely due to high suspended sediment concentrations (and thus low light penetration) throughout the water column, combined with high grazing pressure. However, the recent "clearing" of SFBD waters due to a sharp decrease in suspended sediments may significantly alter the ecology of the estuary, by increasing phytoplankton growth. Thus, the SFBD may be losing its historical resilience to eutrophication, and may soon be "high-nutrient, low-chlorophyll" no more. Elucidating the environmental factors affecting the community structure, activity, and functioning of N-cycling microbes in SFBD is crucial for determining how changes in turbidity and productivity will be propagated throughout the ecosystem. While substantial ecological research in the SFBD has focused on phytoplankton and food webs, bacterial and archaeal communities have received far less attention

  13. Short-term effects of salinity reduction and drainage on salt-marsh biogeochemical cycling and Spartina (Cordgrass) production

    USGS Publications Warehouse

    Portnoy, J.W.; Valiela, I.

    1997-01-01

    To assess the biogeochemical effects of tidal restrictions on salt-marsh sulfur cycling and plant growth, cores of short-form Spartina alterniflora peat were desalinated and kept either waterlogged or drained in greenhouse microcosms. Changes in net Spartina production, and porewater and solid phase chemistry of treated cores were compared to natural conditions in the field collection site over a 21-mo period. Net production among treatments increased significantly in drained and waterlogged peat compared to field conditions during the first growing season. Constantly high sulfide in waterlogged cores accompanied reduced plant growth. Aeration invigorated growth in drained cores but led to oxidization of sulfide minerals and to lowered pH. During the second growing season, growth declined in the drained treatment, probably because of acidification and decreased dissolved inorganic nitrogen. Results are pertinent to the success of current wetland protection and restoration activities in the coastal zone.

  14. Long-Term Trends in the Global Carbon Cycle: Biogeochemical Records of the Past 205 myrs

    NASA Astrophysics Data System (ADS)

    Katz, M. E.; Fennel, K.; Berner, R. A.; Falkowski, P. G.

    2005-12-01

    Atmospheric and seawater chemistry are modified through time by both geological and biological processes: tectonic outgassing in combination with erosional processes are the primary suppliers of most major elements in geochemical cycles; biologically-mediated redox processes alter mobile elemental reservoirs before geologic processes sequester (remove) elements from these mobile reservoirs. We present Jurassic-Cenozoic carbon isotope records for carbonates and organic matter generated from bulk sediment samples from the Atlantic (sample resolution of 200 kyrs), and infer from these records changes in redox conditions and biological processes that affected atmospheric and seawater chemistry through time. We use our carbon isotope records with published sulfur isotopes of sulfates in model simulations to reconstruct carbon burial, pCO2 and pO2 over the past 205 myrs; our model results indicate that organic C burial and pO2 have increased, while pCO2 has decreased. The evolution and expansion of the larger-celled eucaryotic phytoplankton of the red-plastid lineage, coupled with the opening of the Atlantic Ocean basin and global sea-level rise, led to this increase in organic carbon burial beginning in the Early Jurassic as the supercontinent Pangea broke apart. This organic C burial increased the oxidation state of Earth's surface reservoirs while drawing down atmospheric CO2, which in turn acted as a strong selective agent in both marine and terrestrial primary producers, resulting in the rise in C4 and beta-carboxylation photosynthetic pathways in the latter part of the Cenozoic. At the same time, O2 levels approximately doubled, with relatively fast increases in the Early Jurassic and the Eocene. The rise of oxygen may have been a key factor in the evolution, radiation, and subsequent increase in the average size of placental mammals during the Cenozoic.

  15. Biogeochemical sulfur cycling during Cretaceous oceanic anoxic events: A comparison of OAE1a and OAE2

    NASA Astrophysics Data System (ADS)

    Gomes, Maya L.; Hurtgen, Matthew T.; Sageman, Bradley B.

    2016-02-01

    Biogeochemical sulfur cycling has varied widely over geologic time, mainly in response to changes in primary productivity and organic carbon burial, volcanism, weathering, and evaporite deposition. Several of these processes are explicitly linked to discreet (<1.2 Ma) intervals of widespread organic carbon burial, termed oceanic anoxic events (OAEs). During the Cretaceous, there is a highly distinctive ~4‰ negative excursion in the sulfur isotope composition of seawater sulfate (δ34SSO4) that is bracketed by the two most prominent OAEs (OAE1a and OAE2). This excursion lasted for ~25 Ma and has been variously attributed to enhanced volcanism, changes in weathering, evaporite burial, and/or changes in modes of organic carbon remineralization. We present new high-resolution carbon and sulfur isotope records from carbonate-associated sulfate and pyrite for OAE1a and OAE2. OAE1a is characterized by a monotonic decrease in δ34SSO4 values. Both negative and positive δ34SSO4 excursions are associated with OAE2. To refine hypotheses for the observed changes in biogeochemical sulfur cycling associated with these events, we use a simple sulfur isotope box model. Both empirical and modeling results indicate that δ34SSO4 variability was dominated by input fluxes during OAE1a, whereas enhanced volcanism, weathering, and pyrite burial controlled δ34SSO4 records during OAE2. Our analysis supports the conclusion that Cretaceous marine sulfate concentrations were much lower than modern concentrations and indicates that increases in marine sulfate occurred at the onset of both events. We conclude that increases in marine sulfate from low background concentrations, in conjunction with other environmental characteristics, contributed to the development of OAEs.

  16. Spatial patterns of hyporheic exchange and biogeochemical cycling around cross-vane restoration structures: Implications for stream restoration design

    NASA Astrophysics Data System (ADS)

    Gordon, Ryan P.; Lautz, Laura K.; Daniluk, Timothy L.

    2013-04-01

    Natural channel design restoration projects in streams often include the construction of cross-vanes, which are stone, dam-like structures that span the active channel. Vertical hyporheic exchange flux (HEF) and redox-sensitive solutes were measured in the streambed around four cross-vanes with different morphologies. Observed patterns of HEF and redox conditions are not dominated by a single, downstream-directed hyporheic flow cell beneath cross-vanes. Instead, spatial patterns of moderate (<0.4 m d-1) upwelling and downwelling are distributed in smaller cells around pool and riffle bed forms upstream and downstream of structures. Patterns of biogeochemical cycling are controlled by dissolved oxygen concentrations and resulting redox conditions, and are also oriented around secondary bed forms. Strong downwelling into the hyporheic zone (0.5-3.5 m d-1) was observed immediately upstream of structures, but was limited to an area 1-2 m from the cross-vane; these hyporheic flow paths likely rejoin the stream at the base of cross-vanes after residence times too short to alter nitrate concentrations or accumulate reaction products. Total hyporheic exchange volumes are ˜0.4% of stream discharge in restored reaches of 45-55 m. Results show that shallow hyporheic flow and associated biogeochemical cycling near cross-vanes is primarily controlled by secondary bed forms created or augmented by the cross-vane, rather than by the cross-vane itself. This study suggests that cross-vane restoration structures benefit the stream ecosystem by creating heterogeneous patches of varying HEF and redox conditions in the hyporheic zone, rather than by processing large amounts of nutrients to alter in-stream water chemistry.

  17. The role of industrial nitrogen in the global nitrogen biogeochemical cycle

    PubMed Central

    Gu, Baojing; Chang, Jie; Min, Yong; Ge, Ying; Zhu, Qiuan; Galloway, James N.; Peng, Changhui

    2013-01-01

    Haber-Bosch nitrogen (N) has been increasingly used in industrial products, e.g., nylon, besides fertilizer. Massive numbers of species of industrial reactive N (Nr) have emerged and produced definite consequences but receive little notice. Based on a comprehensive inventory, we show that (1) the industrial N flux has increased globally from 2.5 to 25.4 Tg N yr−1 from 1960 through 2008, comparable to the NOx emissions from fossil fuel combustion; (2) more than 25% of industrial products (primarily structural forms, e.g., nylon) tend to accumulate in human settlements due to their long service lives; (3) emerging Nr species define new N-assimilation and decomposition pathways and change the way that Nr is released to the environment; and (4) the loss of these Nr species to the environment has significant negative human and ecosystem impacts. Incorporating industrial Nr into urban environmental and biogeochemical models could help to advance urban ecology and environmental sciences. PMID:23999540

  18. The role of industrial nitrogen in the global nitrogen biogeochemical cycle.

    PubMed

    Gu, Baojing; Chang, Jie; Min, Yong; Ge, Ying; Zhu, Qiuan; Galloway, James N; Peng, Changhui

    2013-01-01

    Haber-Bosch nitrogen (N) has been increasingly used in industrial products, e.g., nylon, besides fertilizer. Massive numbers of species of industrial reactive N (Nr) have emerged and produced definite consequences but receive little notice. Based on a comprehensive inventory, we show that (1) the industrial N flux has increased globally from 2.5 to 25.4 Tg N yr(-1) from 1960 through 2008, comparable to the NOx emissions from fossil fuel combustion; (2) more than 25% of industrial products (primarily structural forms, e.g., nylon) tend to accumulate in human settlements due to their long service lives; (3) emerging Nr species define new N-assimilation and decomposition pathways and change the way that Nr is released to the environment; and (4) the loss of these Nr species to the environment has significant negative human and ecosystem impacts. Incorporating industrial Nr into urban environmental and biogeochemical models could help to advance urban ecology and environmental sciences. PMID:23999540

  19. Exploring a microbial ecosystem approach to modeling deep ocean biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Zakem, E.; Follows, M. J.

    2014-12-01

    Though microbial respiration of organic matter in the deep ocean governs ocean and atmosphere biogeochemistry, it is not represented mechanistically in current global biogeochemical models. We seek approaches that are feasible for a global resolution, yet still reflect the enormous biodiversity of the deep microbial community and its associated metabolic pathways. We present a modeling framework grounded in thermodynamics and redox reaction stoichiometry that represents diverse microbial metabolisms explicitly. We describe a bacterial/archaeal functional type with two parameters: a growth efficiency representing the chemistry underlying a bacterial metabolism, and a rate limitation given by the rate of uptake of each of the necessary substrates for that metabolism. We then apply this approach to answer questions about microbial ecology. As a start, we resolve two dominant heterotrophic respiratory pathways- reduction of oxygen and nitrate- and associated microbial functional types. We combine these into an ecological model and a two-dimensional ocean circulation model to explore the organization, biogeochemistry, and ecology of oxygen minimum zones. Intensified upwelling and lateral transport conspire to produce an oxygen minimum at mid-depth, populated by anaerobic denitrifiers. This modeling approach should ultimately allow for the emergence of bacterial biogeography from competition of metabolisms and for the incorporation of microbial feedbacks to the climate system.

  20. Biogeochemical Cycles for Combining Chemical Knowledge and ESD Issues in Greek Secondary Schools Part II: Assessing the Impact of the Intervention

    ERIC Educational Resources Information Center

    Koutalidi, Sophia; Psallidas, Vassilis; Scoullos, Michael

    2016-01-01

    In searching for effective ways to combine science/chemical education with EE/ESD, new didactic materials were designed and produced focussing on biogeochemical cycles and their connection to sustainable development. The materials were experimentally applied in 16 Greek schools under the newly introduced compulsory "school project" which…

  1. Metatranscriptome Analysis of Aquifer Samples Reveals Unexpected Metabolic Lifestyles Relevant to Active Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    Beller, H. R.; Jewell, T. N. M.; Karaoz, U.; Banfield, J. F.; Brodie, E.; Williams, K. H.

    2015-12-01

    Modern molecular ecology techniques are revealing the metabolic potential of uncultivated microorganisms, but there is still much to be learned about the actual biogeochemical roles of microbes that have cultivated relatives. Here, we present metatranscriptomic and metagenomic data from a field study that provides evidence of coupled redox processes that have not been documented in cultivated relatives and, indeed, represent strains with metabolic traits that are novel with respect to closely related isolates. The data come from omics analysis of groundwater samples collected during an experiment in which nitrate (a native electron acceptor) was injected into a perennially suboxic aquifer in Rifle (CO). Transcriptional data indicated that just two groups of chemolithoautotrophic bacteria accounted for a very large portion (~80%) of overall community gene expression: (1) members of the Fe(II)-oxidizing Gallionellaceae family and (2) strains of the S-oxidizing species, Sulfurimonas denitrificans. Metabolic lifestyles for Gallionellaceae strains that were novel compared to cultivated representatives included nitrate-dependent Fe(II) oxidation and S oxidation. Evidence for these metabolisms included highly correlated temporal expression in binned data of nitrate reductase (e.g., narGHI) genes (which have never been reported in Gallionellaceae genomes) and Fe(II) oxidation genes (e.g., mtoA) or S oxidation genes (e.g., dsrE, aprA). Of the two most active strains of S. denitrificans, only one showed strong expression of S oxidation genes, whereas the other was apparently using an unexpected (as-yet unidentified) primary electron donor. Transcriptional data added considerable interpretive value to this study, as (1) metagenomic data would not have highlighted these organisms, which had a disproportionately large role in community metabolism relative to their populations, and (2) co-expression of coupled pathway genes could not be predicted based solely on metagenomic data.

  2. Linking sediment structure, hydrological functioning and biogeochemical cycling in disturbed coastal saltmarshes and implications for vegetation development

    NASA Astrophysics Data System (ADS)

    Spencer, Kate; Harvey, Gemma; James, Tempest; Simon, Carr; Michelle, Morris

    2014-05-01

    with preferential horizontal flows. The undisturbed saltmarsh displayed typical vertical geochemical sediment profiles. However, in the restored sites total Fe and Mn are elevated at depth indicating an absence of diagenetic cycling, whilst porewater sulphate and nitrate increased at depth suggesting that vertical solute transport is impeded in restored sites. In surface sediments, though total Hg concentrations are similar, Hg methylation rates are significantly higher than in the undisturbed saltmarsh suggesting that surface anoxia and poor drainage may result in increased mobilization and bioavailability of Hg. These findings have implications for the wider biogeochemical ecosystem services offered by saltmarsh restoration and the water-logged, anoxic conditions produced are unsuitable for seedling germination and plant growth. This highlights the need for integrated understanding of physical and biogeochemical processes.

  3. Physical and biogeochemical mechanisms of internal carbon cycling in Lake Michigan

    NASA Astrophysics Data System (ADS)

    Pilcher, Darren J.; McKinley, Galen A.; Bootsma, Harvey A.; Bennington, Val

    2015-03-01

    The lakewide seasonal carbon cycle of Lake Michigan is poorly quantified and lacks the mechanistic links necessary to determine impacts upon it from eutrophication, invasive species, and climate change. A first step toward a full appreciation of Lake Michigan's carbon cycle is to quantify the dominant mechanisms of its internal carbon cycle. To achieve this, we use the MIT general circulation model configured to the bathymetry of Lake Michigan and coupled to an ecosystem model to simulate the seasonal cycle of productivity, temperature, circulation, and the partial pressure of CO2 in water (pCO2). This biogeochemistry is designed to be appropriate for the prequagga mussel state of the lake. The primary mechanism behind the seasonal cycle of primary productivity is lake physics. The offshore spring phytoplankton bloom begins following a reduction in deep vertical mixing and ends with the depletion of nutrients via thermal stratification. The exception is the western shoreline, where summer winds drive coastal upwelling, providing hypolimnetic nutrients and generating significant productivity. Surface pCO2 is controlled by the net effect from temperature on solubility, and is modulated by biological uptake of dissolved inorganic carbon (DIC) and isothermal mixing of DIC-rich water in winter. Temperature tends to have the greatest seasonal impact in nearshore regions, while local DIC has the greatest impact in offshore regions. Lakewide, the model suggests that carbon is absorbed from the atmosphere during the spring bloom and released to the atmosphere during winter mixing and when summer surface temperatures are at their maximum.

  4. Biogeochemical processes and buffering capacity concurrently affect acidification in a seasonally hypoxic coastal marine basin

    NASA Astrophysics Data System (ADS)

    Hagens, M.; Slomp, C. P.; Meysman, F. J. R.; Seitaj, D.; Harlay, J.; Borges, A. V.; Middelburg, J. J.

    2015-03-01

    Coastal areas are impacted by multiple natural and anthropogenic processes and experience stronger pH fluctuations than the open ocean. These variations can weaken or intensify the ocean acidification signal induced by increasing atmospheric pCO2. The development of eutrophication-induced hypoxia intensifies coastal acidification, since the CO2 produced during respiration decreases the buffering capacity in any hypoxic bottom water. To assess the combined ecosystem impacts of acidification and hypoxia, we quantified the seasonal variation in pH and oxygen dynamics in the water column of a seasonally stratified coastal basin (Lake Grevelingen, the Netherlands). Monthly water-column chemistry measurements were complemented with estimates of primary production and respiration using O2 light-dark incubations, in addition to sediment-water fluxes of dissolved inorganic carbon (DIC) and total alkalinity (TA). The resulting data set was used to set up a proton budget on a seasonal scale. Temperature-induced seasonal stratification combined with a high community respiration was responsible for the depletion of oxygen in the bottom water in summer. The surface water showed strong seasonal variation in process rates (primary production, CO2 air-sea exchange), but relatively small seasonal pH fluctuations (0.46 units on the total hydrogen ion scale). In contrast, the bottom water showed less seasonality in biogeochemical rates (respiration, sediment-water exchange), but stronger pH fluctuations (0.60 units). This marked difference in pH dynamics could be attributed to a substantial reduction in the acid-base buffering capacity of the hypoxic bottom water in the summer period. Our results highlight the importance of acid-base buffering in the pH dynamics of coastal systems and illustrate the increasing vulnerability of hypoxic, CO2-rich waters to any acidifying process.

  5. [Seasonal evolution of the biogeochemical cycle in the southwest lagoon of New Caledonia. Application of a compartmental model].

    PubMed

    Bujan, S; Grenz, C; Fichez, R; Douillet, P

    2000-02-01

    A biogeochemical box model describing the south-west lagoon of New-Caledonia was developed in order to simulate the seasonal cycle of carbon and nitrogen. We used fluxes generated by a 3D hydrodynamic model to simulate horizontal exchanges between boxes and added freshwater influxes as nitrogen sources from the land. Average residence time proved to be less than 11 days for the lagoon as a whole. Standard simulations showed baseline values of chlorophyll a between 0.2 and 0.4 microgram.L-1. Influences of freshwater influxes proved to be significant (increases up to 1 microgram.L-1) only in shallow areas protected from wind exposure and during short periods of heavy rainfall (tropical depressions). Tropical climatic events have reduced impact in space and time and long-term simulations over decades with increased nutrient inputs did not show any significant process of eutrophication. Hydrodynamics seemed to be one of the major control factors with respect to organic matter cycling in the lagoon. PMID:10763441

  6. Biogeochemical cycling of manganese in Oneida Lake, New York: whole lake studies of manganese

    NASA Technical Reports Server (NTRS)

    Aguilar, C.; Nealson, K. H.

    1998-01-01

    Oneida Lake, New York is a eutrophic freshwater lake known for its abundant manganese nodules and a dynamic manganese cycle. Temporal and spatial distribution of soluble and particulate manganese in the water column of the lake were analyzed over a 3-year period and correlated with other variables such as oxygen, pH, and temperature. Only data from 1988 are shown. Manganese is removed from the water column in the spring via conversion to particulate form and deposited in the bottom sediments. This removal is due to biological factors, as the lake Eh/pH conditions alone can not account for the oxidation of the soluble manganese Mn(II). During the summer months the manganese from microbial reduction moves from the sediments to the water column. In periods of stratification the soluble Mn(II) builds up to concentrations of 20 micromoles or more in the bottom waters. When mixing occurs, the soluble Mn(II) is rapidly removed via oxidation. This cycle occurs more than once during the summer, with each manganese atom probably being used several times for the oxidation of organic carbon. At the end of the fall, whole lake concentrations of manganese stabilize, and remain at about 1 micromole until the following summer, when the cycle begins again. Inputs and outflows from the lake indicate that the active Mn cycle is primarily internal, with a small accumulation each year into ferromanganese nodules located in the oxic zones of the lake.

  7. Investigating the organic carbon cycle and the anaerobic oxidation of methane in the Guaymas Basin: a biogeochemical approach

    NASA Astrophysics Data System (ADS)

    Cathalot, C.; Decker, C.; Caprais, J.; Ruffine, L.; Le Bruchec, J.; Olu, K.

    2013-12-01

    The Guaymas Basin is a pretty unique environment located in the Gulf of California and characterized by the emanation of fluids enriched in hydrocarbon, mainly methane, and sulfides. In this peculiar environment, both cold seeps and hydrothermal vents co-exist very closely, and are separated only by a few kilometers. In addition, highly productive surface waters and strong terrestrial inputs are responsible for strong sedimentation rates in this area. This special geological system allows for the development of various and complex macrofaunal and/or bacterial assemblages, based on chemosynthetic activity. These sea-bottom communities have been previously described [1,2] and several studies have demonstrated the occurrence of Anaerobic Oxidation of Methane (AOM) in the shallow sediment layers. Nevertheless, the quantification of the biogeochemical processes (e.g. rates, relative proportions) involved in both ecosystems in relation with the associated communities, and their role in the local organic carbon (OC) cycle is still lacking. Using a diagenetic modeling approach, this study aims at studying the OC production and recycling processes by describing the biogeochemical pathways and their associated rates in the ecosystems from the Guaymas Basin. Twelve stations presenting distinct biological assemblages (microbial mats, vesicomyids and bare sediment) were selected among both cold-seeps and hydrothermal vents sites from the Guaymas basin. A transport-reaction model including respiration, sulfate reduction, methanogenesis and AOM was developed and applied to each station. To constrain the model, at each station, cores were sampled using an ROV and the pore-waters extracted using Rhizon syringes. Pore-water concentrations of CH4, SO42-, Cl- and H2S were then measured. In addition, ex situ O2 microprofiles equipped with microsensors and in situ incubations using benthic chambers were performed to estimate the sediment uptake rates (O2, H2S, CH4). The overall dataset

  8. Unraveling the Drivers of Spatial and Temporal Variability in Biogeochemical Cycling at Aquifer-River Interfaces - The LEVERHULME Hyporheic Zone Research Network

    NASA Astrophysics Data System (ADS)

    Krause, Stefan

    2015-04-01

    While there has been substantial improvement of understanding hyporheic exchange flow and residence time controls on biogeochemical turnover rates, there is little knowledge of the actual drivers of the spatial and temporal variability of interlinked biogeochemical cycles. Previous research has mainly focused on bedform controlled hyporheic exchange and the transformation of surface solutes along a hyporheic flow path but failed to explain observations of spatially and temporally variable nutrient turnover in streambeds with higher structural heterogeneity and autochthonous carbon and nitrogen sources. The "Leverhulme Hyporheic Zone Research Network" has developed an interdisciplinary strategy for investigating the physical controls on hyporheic exchange fluxes and residence time distributions, heat and reactive solute transport along biogeographical and catchment gradients. This strategy combines smart tracer applications with distributed sensor networks in multi-scale nested monitoring schemes and numerical model studies to investigate the interactions between physico-chemical process dynamics and hyporheic microbial, invertebrate and macrophyte ecology. Investigations integrating the process knowledge from mesocosms to artificial channels and stream reaches highlight the impact of small-scale streambed structure on spatial patterns of hyporheic exchange flow, residence time distribution and the development of biogeochemical hotspots. Manipulation studies inhibiting flow through dominant hyporheic exchange flow paths allowed to quantify the functional significance, sensitivity and resilience of biogeochemical, microbial and ecological functioning of identified hyporheic hotspots to environmental change. Further discharge and stage manipulations proved to not only control in-channel macrophyte growth but also temperature patterns and residence time distributions as well as microbial metabolic activity and biogeochemical processing rates, highlighting the potential

  9. Unraveling the Drivers of Spatial and Temporal Variability in Biogeochemical Cycling at Aquifer-River Interfaces - The LEVERHULME Hyporheic Zone Research Network

    NASA Astrophysics Data System (ADS)

    Krause, S.; Ward, A. S.; Zarnetske, J. P.; Martí Roca, E.; Larned, S.; Milner, A.; Datry, T.; Fleckenstein, J. H.; Schmidt, C.; Blaen, P.; Kurz, M. J.; Klaar, M. J.; Drummond, J. D.; Knapp, J.; Folegot, S.; Hannah, D. M.; Romeijn, P.; Blume, T.; Lewandowski, J.; Maruedo, A.; Ledger, M.; Lee-Cullin, J. A.; O'Callaghan, M.; Keller, T.; Vieweg, M.

    2014-12-01

    While there has been substantial improvement of understanding hyporheic exchange flow and residence time controls on biogeochemical turnover rates, there is little knowledge of the actual drivers of the spatial and temporal variability of interlinked biogeochemical cycles. Previous research has mainly focused on bedform controlled hyporheic exchange and the transformation of surface solutes along a hyporheic flow path but failed to explain observations of spatially and temporally variable nutrient turnover in streambeds with higher structural heterogeneity and autochthonous carbon and nitrogen sources. The "Leverhulme Hyporheic Zone Research Network" has developed an interdisciplinary strategy for investigating the physical controls on hyporheic exchange fluxes and residence time distributions, heat and reactive solute transport along biogeographical and catchment gradients. This strategy combines smart tracer applications with distributed sensor networks in multi-scale nested monitoring schemes and numerical model studies to investigate the interactions between physico-chemical process dynamics and hyporheic microbial, invertebrate and macrophyte ecology. Investigations integrating the process knowledge from mesocosms to artificial channels and stream reaches highlight the impact of small-scale streambed structure on spatial patterns of hyporheic exchange flow, residence time distribution and the development of biogeochemical hotspots. Manipulation studies inhibiting flow through dominant hyporheic exchange flow paths allowed to quantify the functional significance, sensitivity and resilience of biogeochemical, microbial and ecological functioning of identified hyporheic hotspots to environmental change. Further discharge and stage manipulations proved to not only control in-channel macrophyte growth but also temperature patterns and residence time distributions as well as microbial metabolic activity and biogeochemical processing rates, highlighting the potential

  10. Biogeochemical cycles in a tropical lowland rainforest (La Reunion Island) developed on a basaltic flow : first results

    NASA Astrophysics Data System (ADS)

    Kirman, S.; Strasberg, D.; Grondin, V.; Meunier, J. D.

    2001-12-01

    La Reunion (Indian Ocean) is one of the last volcanic island that supports a lowland rainforest relatively unaffected by man. Contrary to other well known spots such as Hawaii, the biodiversity is still high. A project financed by the French Government (IRD and PNSE) is undertaken to determine the biogeochemical cycles of C and major elements in the Marelongue Natural Reserve. The studied site is located along the Piton de la Fournaise Volcano, on basaltic flows dated approximately around 500 y. The aim of the project is to better constrain the biogeochemical models of rainforest ecosystems. Here we present preliminary results on the relations between biodiversity and ecosystem productivity and mineral cycling. We measure, in a 1 ha permanent plot, the element content stored in the above ground biomass and the return of these elements to the soil. A total of 1079 trees (DBH {* } 10 cm) were identified and measured in the permanent plot. The biomass was estimated by an indirect method based on allometric relations from trees harvested in previous studies elsewhere. The calculated above ground biomass ranged from to 267 to 300 tha and only three species (Labourdonnaisia calophylloides, Nuxia verticillata and Agauria.salicifolia) represent more than 60% of that biomass. The litter production was measured by collecting every 15 days the fine litterfall on a 0.5 ha plot, from August 2000 to July 2001 and the estimated annual mean was 6.6 t/ha of which 74% were leaves. Again, two of the species (Labourdonnaisia calophylloidesa and Nuxia verticillata) contribute to nearly 60% of the total fine litterfall. Over the year, seasonal variations were observed and showed two peaks, one in January and one during the months of March and April. The first one can be attributed to the occurrence of a cyclone at 200km from the coast. The annual litterfall pattern is dominated by the litterfall of the two dominant canopy trees. The leaf mineral content was determined for 15 of the

  11. A role for scavenging in the marine biogeochemical cycling of zinc and zinc isotopes

    NASA Astrophysics Data System (ADS)

    John, Seth G.; Conway, Tim M.

    2014-05-01

    Zinc (Zn) and cadmium (Cd) are important biologically active trace-metals in the ocean. To date, the marine distributions of these elements have been understood primarily in terms of biological assimilation by growing phytoplankton and regeneration of sinking biological material. Initial studies of Zn and Cd concentrations and stable isotope ratios (δ66Zn and δ114Cd) have therefore focused on their use as simple tracers of assimilation and regeneration in the oceans. However, these two processes are insufficient to explain new data on the marine distribution of Zn and δ66Zn. Here, using the first high-resolution paired marine depth profiles of Zn, Cd, δ66Zn and δ114Cd, we suggest that scavenging of Zn onto organic matter plays a major, yet largely unconsidered, role in the marine cycling of Zn. This hypothesis is supported by culture experiments, which show that Zn released from degrading phytoplankton is rapidly scavenged back onto organic matter, and that adsorbed Zn is isotopically heavier than the dissolved phase by 0.58‰. In contrast, very little Cd or phosphate was scavenged and Cd isotopes were not significantly fractionated during degradation. Our hypothesis is further supported by one-dimensional modeling, which reproduces observed marine δ66Zn profiles with <1% of Zn adsorbed to particles. Understanding how Zn cycling in the oceans is a balance between assimilation, scavenging, and regeneration is necessary in order to investigate δ66Zn as a tracer of marine productivity. We anticipate that paired analyses of δ66Zn and δ114Cd will prove to be valuable new tools in constraining patterns of global primary productivity, providing key information for the marine carbon cycle during periods of past and present global climate change.

  12. Tectonic Cycles and the History of the Earth's Biogeochemical and Paleoceanographic Record

    NASA Astrophysics Data System (ADS)

    Worsley, Thomas R.; Nance, R. Damian; Moody, Judith B.

    1986-09-01

    An integrated approach to earth history for the last 2.5 b.y. reveals the strong interdependence of all geologic variables. Three earth history components are identified and interrelated: secular trends as the earth ages, recurring events of a previously proposed supercontinent megacycle (Worsley et al., 1984, 1985), and nonrecurring environmental shifts. Declining secular trends are endogenic heat production, atmospheric carbon dioxide levels, and surface temperatures. Continental differentiation, enzyme efficiency, atmospheric oxygen levels, and solar luminosity are increasing secular trends. Four phases of a supercontinent cycle (supercontinent fragmentation, maximum continent dispersal, continental assembly, and supercontinental stasis) recur with a ˜0.5-b.y. period and are correlated with tectonism, cratonic sediment preservation, atmospheric and hydrospheric evolution, and the distribution of marine platform stable isotopes. These correlations reflect coupling among the various oceanic and continental constituents during consecutive supercontinent assemblies and fragmentations. Nonrecurring shifts are unique and irreversible events in earth history (e.g., development of photosynthesis, occurrence of banded iron formations, and deposition of detrital uraninite) that represent periods of rapid geochemical adjustment to biospheric evolution. Earth's tectonobiogeochemical history is then synthesized by integrating secular trends and nonrecurring events with the supercontinent cycle, emphasizing the preferentially preserved periods of fragmentation and continental dispersal. Paleoceanographic consequences of the megacycle are considered to reflect the stepwise coupling of secular trends and nonrecurring events to a biotically controlled, phosphorus-organic carbon-climate linkage required to maintain earth's post-Archean surface temperature.

  13. Inorganic Carbon Cycling and Biogeochemical Processes in an Arctic Inland Sea (Hudson Bay)

    NASA Astrophysics Data System (ADS)

    Burt, William; Thomas, Helmuth; Miller, Lisa; Granskog, Mats; Papakyriakou, Tim; Pengelly, Leah

    2016-04-01

    The distributions of CO2 system parameters in Hudson Bay, which not only receives nearly one third of Canada's river discharge, but is also subject to annual cycles of sea-ice formation and melt, indicate that the timing and magnitude of freshwater inputs play an important role in carbon biogeochemistry and ocean acidification in this unique Arctic ecosystem. This study uses basin-wide measurements of dissolved inorganic carbon (DIC) and total alkalinity (TA), as well as stable isotope tracers (δ18OH2O and δ13CDIC), to provide a detailed assessment of carbon cycling processes throughout the bay. Surface distributions of carbonate parameters reveal the particular importance of freshwater inputs in the southern portion of the bay. Riverine TA end-members vary significantly both regionally and with small changes in near-surface depths, highlighting the importance of careful surface water sampling in highly stratified waters. In an along-shore transect, large increases in subsurface DIC are accompanied by equivalent decreases in δ13CDIC with no discernable change in TA, indicating a respiratory DIC production on the order of 100 μmol/kg during deep water circulation around the bay. Based on TA data we surmise that the deep waters in the Hudson Bay are of Pacific origin.

  14. Microbial iron oxidation in the Arctic tundra and its implications for biogeochemical cycling.

    PubMed

    Emerson, David; Scott, Jarrod J; Benes, Joshua; Bowden, William B

    2015-12-01

    The role that neutrophilic iron-oxidizing bacteria play in the Arctic tundra is unknown. This study surveyed chemosynthetic iron-oxidizing communities at the North Slope of Alaska near Toolik Field Station (TFS) at Toolik Lake (lat 68.63, long -149.60). Microbial iron mats were common in submerged habitats with stationary or slowly flowing water, and their greatest areal extent is in coating plant stems and sediments in wet sedge meadows. Some Fe-oxidizing bacteria (FeOB) produce easily recognized sheath or stalk morphotypes that were present and dominant in all the mats we observed. The cool water temperatures (9 to 11°C) and reduced pH (5.0 to 6.6) at all sites kinetically favor microbial iron oxidation. A microbial survey of five sites based on 16S rRNA genes found a predominance of Proteobacteria, with Betaproteobacteria and members of the family Comamonadaceae being the most prevalent operational taxonomic units (OTUs). In relative abundance, clades of lithotrophic FeOB composed 5 to 10% of the communities. OTUs related to cyanobacteria and chloroplasts accounted for 3 to 25% of the communities. Oxygen profiles showed evidence for oxygenic photosynthesis at the surface of some mats, indicating the coexistence of photosynthetic and FeOB populations. The relative abundance of OTUs belonging to putative Fe-reducing bacteria (FeRB) averaged around 11% in the sampled iron mats. Mats incubated anaerobically with 10 mM acetate rapidly initiated Fe reduction, indicating that active iron cycling is likely. The prevalence of iron mats on the tundra might impact the carbon cycle through lithoautotrophic chemosynthesis, anaerobic respiration of organic carbon coupled to iron reduction, and the suppression of methanogenesis, and it potentially influences phosphorus dynamics through the adsorption of phosphorus to iron oxides. PMID:26386054

  15. Microbial Iron Oxidation in the Arctic Tundra and Its Implications for Biogeochemical Cycling

    PubMed Central

    Scott, Jarrod J.; Benes, Joshua; Bowden, William B.

    2015-01-01

    The role that neutrophilic iron-oxidizing bacteria play in the Arctic tundra is unknown. This study surveyed chemosynthetic iron-oxidizing communities at the North Slope of Alaska near Toolik Field Station (TFS) at Toolik Lake (lat 68.63, long −149.60). Microbial iron mats were common in submerged habitats with stationary or slowly flowing water, and their greatest areal extent is in coating plant stems and sediments in wet sedge meadows. Some Fe-oxidizing bacteria (FeOB) produce easily recognized sheath or stalk morphotypes that were present and dominant in all the mats we observed. The cool water temperatures (9 to 11°C) and reduced pH (5.0 to 6.6) at all sites kinetically favor microbial iron oxidation. A microbial survey of five sites based on 16S rRNA genes found a predominance of Proteobacteria, with Betaproteobacteria and members of the family Comamonadaceae being the most prevalent operational taxonomic units (OTUs). In relative abundance, clades of lithotrophic FeOB composed 5 to 10% of the communities. OTUs related to cyanobacteria and chloroplasts accounted for 3 to 25% of the communities. Oxygen profiles showed evidence for oxygenic photosynthesis at the surface of some mats, indicating the coexistence of photosynthetic and FeOB populations. The relative abundance of OTUs belonging to putative Fe-reducing bacteria (FeRB) averaged around 11% in the sampled iron mats. Mats incubated anaerobically with 10 mM acetate rapidly initiated Fe reduction, indicating that active iron cycling is likely. The prevalence of iron mats on the tundra might impact the carbon cycle through lithoautotrophic chemosynthesis, anaerobic respiration of organic carbon coupled to iron reduction, and the suppression of methanogenesis, and it potentially influences phosphorus dynamics through the adsorption of phosphorus to iron oxides. PMID:26386054

  16. Evidence for global reorganisation of biogeochemical cycles at 2.73 Ma.

    NASA Astrophysics Data System (ADS)

    Reynolds, B. C.; Jaccard, S. L.; Frank, M.; Halliday, A. N.

    2006-12-01

    The abrupt cessation of high opaline accumulation marks the initiation of Northern Hemisphere Glaciation and the beginning of ice-rafted debris deposition in the Subarctic North Pacific at ~2.73 Ma. The decrease in opal flux has been linked to a decrease in the exposure of nutrient-rich deep water to the surface caused by an increased stratification of the water column within the subarctic gyre. The restricted supply should have led to more complete utilization of nutrients and silicate and a resulting increase in the δ15N and δ^{30}Si values in organic matter and diatoms deposited in the marine sediments. Whilst nitrogen isotopes from bulk sediments as well as diatom-bound nitrogen indeed documented a heavy isotope enrichment, there is an inverse correlation with silicon isotopes. This is best explained as a result of changes in the nutrient limiting conditions from high silicic acid utilization under nitrate replete conditions prior to 2.73 Ma to more nitrate depleted conditions and lower Si utilization thereafter. These changes imply a global reorganisation of the nutrient cycling within the global thermohaline circulation rather than a regional change in nutrient dynamics. A contemporaneous shift towards higher primary diatom productivity in the Southern Ocean led to enhanced nutrient storage in deep-waters and ultimately to a global cooling due to a diminished green-house effect. These changes pre-date the major intensification of Northern Hemisphere Glaciation observed in the North Atlantic at 2.5 Ma, but probably mark a switch across a global climatic threshold leading to Northern Hemisphere glacial cycles.

  17. Isolation and characterization of an NAD+-degrading bacterium PTX1 and its role in chromium biogeochemical cycle

    SciTech Connect

    Puzon, Geoffrey J.; Huang, Yan C.; Dohnalkova, Alice; Xun, Luying

    2008-06-01

    Microorganisms can reduce toxic chromate to less toxic trivalent chromium [Cr(III)]. Besides Cr(OH)3 precipitates, some soluble organo-Cr(III) complexes are readily formed upon microbial, enzymatic, and chemical reduction of chromate. However, the biotransformation of the organo-Cr(III) complexes has not been characterized. We have previously reported the formation of a nicotinamide adenine dinucleotide (NAD+)-Cr(III) complex after enzymatic reduction of chromate. Although the NAD+-Cr(III) complex was stable under sterile conditions, microbial cells were identified as precipitates in a non-sterile NAD+-Cr(III) solution after extended incubation. The most dominant bacterium PTX1 was isolated and assigned to Leifsonia genus by phylogenetic analysis of 16S rRNA gene sequence. PTX1 grew slowly on NAD+ with a doubling time of 17 h, and even more slowly on the NAD+-Cr(III) complex with an estimated doubling time of 35 days. The slow growth suggests that PTX1 passively grew on trace NAD+ dissociated from the NAD+-Cr(III) complex, facilitating further dissociation of the complex and formation of Cr(III) precipitates. Thus, organo-Cr(III) complexes might be an intrinsic link of the chromium biogeochemical cycle; they can be produced during chromate reduction and then further mineralized by microorganisms.

  18. [Neutrophilic lithotrophic iron-oxidizing prokaryotes and their role in the biogeochemical processes of the iron cycle].

    PubMed

    Dubinina, G A; Sorokina, A Iu

    2014-01-01

    Biology of lithotrophic neutrophilic iron-oxidizing prokaryotes and their role in the processes of the biogeochemical cycle of iron are discussed. This group of microorganisms is phylogenetically, taxonomically, and physiologically heterogeneous, comprising three metabolically different groups: aerobes, nitrate-dependent anaerobes, and phototrophs; the latter two groups have been revealed relatively recently. Their taxonomy and metabolism are described. Materials on the structure and functioning of the electron transport chain in the course of Fe(II) oxidation by members of various physiological groups are discussed. Occurrence of iron oxidizers in freshwater and marine ecosystems, thermal springs, areas of hydrothermal activity, and underwater volcanic areas are considered. Molecular genetic techniques were used to determine the structure of iron-oxidizing microbial communities in various natural ecosystems. Analysis of stable isotope fractioning of 56/54Fe in pure cultures and model experiments revealed predominance of biological oxidation over abiotic ones in shallow aquatic habitats and mineral springs, which was especially pronounced under microaerobic conditions at the redox zone boundary. Discovery of anaerobic bacterial Fe(II) oxidation resulted in development of new hypotheses concerning the possible role of microorganisms and the mechanisms of formation of the major iron ore deposits in Precambrian and early Proterozoic epoch. Paleobiological data are presented on the microfossils and specific biomarkers retrieved from ancient ore samples and confirming involvement of anaerobic biogenic processes in their formation. PMID:25423717

  19. [Neutrophilic lithotrophic iron-oxidizing prokaryotes and their role in the biogeochemical processes of the iron cycle].

    PubMed

    2014-01-01

    Biology of lithotrophic neutrophilic iron-oxidizing prokaryotes and their role in the processes of the biogeochemical cycle of iron are discussed. This group of microorganisms is phylogenetically, taxonomically, and physiologically heterogeneous, comprising three metabolically different groups: aerobes, nitrate-dependent anaerobes, and phototrophs; the latter two groups have been revealed relatively recently. Their taxonomy and metabolism are described. Materials on the structure and functioning of the electron transport chain in the course of Fe(II) oxidation by members of various physiological groups are discussed. Occurrence of iron oxidizers in freshwater and marine ecosystems, thermal springs, areas of hydrothermal activity, and underwater volcanic areas are considered. Molecular genetic techniques were used to determine the structure of iron-oxidizing microbial communities in various natural ecosystems. Analysis of stable isotope fractioning of 56/54Fe in pure cultures and model experiments revealed predominance of biological oxidation over abiotic ones in shallow aquatic habitats and mineral springs, which was especially pronounced under microaerobic conditions at the redox zone boundary. Discovery of anaerobic bacterial Fe(II) oxidation resulted in development of new hypotheses concerning the possible role of microorganisms and the mechanisms of formation of the major iron ore deposits in Precambrian and early Proterozoic epoch. Paleobiological data are presented on the microfossils and specific biomarkers retrieved from ancient ore samples and confirming involvement of anaerobic biogenic processes in their formation. PMID:25507440

  20. Bromine isotope analysis - a tool for investigating biogeochemical cycle of bromine-containing organic and inorganic compounds in the environment

    NASA Astrophysics Data System (ADS)

    Gelman, F.; Bernstein, A.; Levin, E.; Ronen, Z.; Halicz, L.

    2012-04-01

    Bromine naturally occurs mainly in the form of bromide and is usually considered as a conservative tracer in the groundwater system. However, nowadays many synthetically produced organobromine compounds are introduced into the environment by humans. Due to a possible toxic effect of these compounds, investigation of their fate in the nature is of the utmost importance. In this sense, examination of isotopic composition of inorganic and organic bromine may serve as a powerful tool for understanding Br geochemical cycle. Due to a relatively small mass difference between the isotopes 81Br and 79Br, bromine isotope fractionation originating from biotic and abiotic processes is expected to be in the range of several permille. Therefore, a highly precise technique for the bromine isotope ratio analysis is required. This work presents a new methodology for the precise determination of bromine isotope ratio in inorganic bromides and individual organic compounds by MC-ICPMS. Attained external precision (2σ) up to 0.1‰ allowed employment of the developed technique for determination of the bromine isotope composition in organic and inorganic bromides and Br KIE in biogeochemical processes.

  1. Natural biogeochemical cycle of mercury in a global three-dimensional ocean tracer model

    NASA Astrophysics Data System (ADS)

    Zhang, Yanxu; Jaeglé, Lyatt; Thompson, LuAnne

    2014-05-01

    We implement mercury (Hg) biogeochemistry in the offline global 3-D ocean tracer model (OFFTRAC) to investigate the natural Hg cycle, prior to any anthropogenic input. The simulation includes three Hg tracers: dissolved elemental (Hg0aq), dissolved divalent (HgIIaq), and particle-bound mercury (HgPaq). Our Hg parameterization takes into account redox chemistry in ocean waters, air-sea exchange of Hg0, scavenging of HgIIaq onto sinking particles, and resupply of HgIIaq at depth by remineralization of sinking particles. Atmospheric boundary conditions are provided by a global simulation of the natural atmospheric Hg cycle in the GEOS-Chem model. In the surface ocean, the OFFTRAC model predicts global mean concentrations of 0.16 pM for total Hg, partitioned as 80% HgIIaq, 14% Hg0aq, and 6% HgPaq. Total Hg concentrations increase to 0.38 pM in the thermocline/intermediate waters (between the mixed layer and 1000 m depth) and 0.82 pM in deep waters (below 1000 m), reflecting removal of Hg from the surface to the subsurface ocean by particle sinking followed by remineralization at depth. Our model predicts that Hg concentrations in the deep North Pacific Ocean (>2000 m) are a factor of 2-3 higher than in the deep North Atlantic Ocean. This is the result of cumulative input of Hg from particle remineralization as deep waters transit from the North Atlantic to the North Pacific on their ~2000 year journey. The model is able to reproduce the relatively uniform concentrations of total Hg observed in the old deep waters of the North Pacific Ocean (observations: 1.2 ± 0.4 pM; model: 1.1 ± 0.04 pM) and Southern Ocean (observations: 1.1 ± 0.2 pM; model: 0.8 ± 0.02 pM). However, the modeled concentrations are factors of 5-6 too low compared to observed concentrations in the surface ocean and in the young water masses of the deep North Atlantic Ocean. This large underestimate for these regions implies a factor of 5-6 anthropogenic enhancement in Hg concentrations.

  2. Biogeochemical Iron Cycling in Subalpine Wetlands: Impact of Root Derived Organic Matter from the Molecular to the Field Scale

    NASA Astrophysics Data System (ADS)

    Borch, T.; Marsh, A.; Rhoades, C.; Hubbard, R. M.; Elder, K.; Kelly, E. F.

    2011-12-01

    Intensification of hydrologic regimes due to climate change will have important impacts on biogeochemical processes and ecosystem services, but quantifying these impacts experimentally remains a key challenge for Earth scientists. Iron (Fe) is the 4th most abundant element of the Earth's crust, and Fe (hydr)oxide minerals can account for a significant amount of the bulk mass of soils. In contrast to lab-synthesized ferrihydrite (Fhy), natural ferrihydrite is often formed in the presence of plant derived humic substances (HS). Despite the abundant presence of HS coated Fhy and Fhy-HS coprecipitates in natural systems, there is a significant gap in our understanding of how plant derived carbon influence the crystal structure and reactivity of Fe (hydr)oxides. The goal of this presentation is to illustrate one approach to quantification of the potential impacts of changes in soil moisture (redox conditions) as well as adsorbed or coprecipitated HS on the biogeochemical cycling of iron in subalpine wetlands with different hydrology based on lab and field studies. We found that that humic substances both adsorbed to and coprecipitated with iron oxides (i.e., ferrihydrite) influenced both the bioreduction kinetics (by Shewanalla putrefaciens) and the secondary iron mineral phases formed (based on synchrotron radiation-based X-ray absorption analysis). The ferrihydrite reduction kinetics was influenced in a non-linear fashion showing little impact of low HS concentrations but significantly increased total Fe(II) production at high HS concentration. Both adsorbed and coprecipitated HS appeared to limit goethite (FeOOH) formation but favor the formation of ferrous bearing iron phases. These changes are likely due to changes in surface charge, specific surface area, or crystal structure. Thus, the effect of plant derived organic matter on microbial iron mineral transformation and reactivity has to be included in the framework of environmental iron biogeochemistry. The

  3. Marine Snow and Gels: Hot Spots of Biogeochemical Cycling, Biological Activity, and Sedimentation in the Sea

    NASA Astrophysics Data System (ADS)

    Alldredge, A. L.

    2004-12-01

    Much of the organic carbon sequestered in the deep sea and ocean bottom sediments as relatively rare, large detrital particles generically known as marine snow. Because they are enriched in organic matter, microbes, and nutrients, these large particles also serve as hot spots for biological and chemical process in the water column. Recent evidence reveals that abundant carbohydrate gel particles in the ocean, formed from the dissolved exudates of phytoplankton and bacteria, are intricately involved in the formation of marine snow. These discoveries are changing the way we conceptualize the pelagic zone on small scales. We no longer imagine seawater as a relatively homogeneous fluid in which float a spectrum of dispersed molecules, particles, and organisms, but instead see it as a rich hydrated matrix of transparent organic gels, detritus, and cob-web like surfaces which provide microscale physical, chemical, and biological structure. This talk will focus on the origins, fate, and significance of marine snow and gels in the sea, including their role in carbon cycling, sedimentation and carbon flux , food webs, and chemical and biological transformation.

  4. Climate Change and Biogeochemical Cycling in Green Lakes Valley, Colorado Front Range, USA

    NASA Astrophysics Data System (ADS)

    Barnes, R. T.; Parman, J.; Williams, M. W.

    2010-12-01

    Alpine ecosystems are particularly susceptible to disturbance due to their short growing seasons, sparse vegetation, thin soils, and a harsh climate. Warming temperatures and atmospheric nitrogen deposition, two drivers of global change, are currently affecting the Green Lakes Valley within the Colorado Front Range. At the top of Green Lakes Valley is Arikaree glacier, a 9 ha cirque glacier which has steady decreased in size since 2000. The watershed continues to receive elevated amounts of nitrogen deposition; however the atmospheric flux of inorganic nitrogen has decreased by 0.56 kg ha-1yr-1 since 2000, due to several years of low rainfall. Despite this decrease N deposition, the alpine watershed’s yield of nitrate has increased by 40% over the same time period relative to 1990-1999, at an approximate rate of 0.47 kg ha-1yr-1 since 2000. Concurrent with increases in nitrate were large increases in sulfate (1.13 kg ha-1yr-1), calcium (0.63 kg ha-1yr-1) and silica (0.22 kg ha-1yr-1) yields. The source of these increased yields appears to be meltwater from Arikaree and thawing permafrost. Mass balance models indicate that high ammonium loads within Arikaree’s meltwater are rapidly nitrified; contributing approximately 0.45 kg yr-1 to the NO3- flux within the upper reaches of the watershed. The chemistry of melting permafrost (as indicated by rock glacial meltwater) is rich in geochemical weathering products suggesting that it is the source of increased sulfate, calcium, and silica as well as providing sustained water contributions late into the growing season. Downstream within the subalpine, there was no increase in nitrate yield and relatively small increases in weathering products, suggesting that the subalpine serves as a sink for excess nitrogen and weathering products. Finally, there were no long term increases in nitrate, sulfate, silica, or calcium at a nearby watershed devoid of glacial and permafrost features; providing further evidence that the

  5. "Anticlumping" and Other Combinatorial Effects on Clumped Isotopes: Implications for Tracing Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    Yeung, L.

    2015-12-01

    I present a mode of isotopic ordering that has purely combinatorial origins. It can be important when identical rare isotopes are paired by coincidence (e.g., they are neighbors on the same molecule), or when extrinsic factors govern the isotopic composition of the two atoms that share a chemical bond. By itself, combinatorial isotope pairing yields products with isotopes either randomly distributed or with a deficit relative to a random distribution of isotopes. These systematics arise because of an unconventional coupling between the formation of singly- and multiply-substituted isotopic moieties. In a random distribution, rare isotopes are symmetrically distributed: Single isotopic substitutions (e.g., H‒D and D‒H in H2) occur with equal probability, and double isotopic substitutions (e.g., D2) occur according to random chance. The absence of symmetry in a bond-making complex can yield unequal numbers of singly-substituted molecules (e.g., more H‒D than D‒H in H2), which is recorded in the product molecule as a deficit in doubly-substituted moieties and an "anticlumped" isotope distribution (i.e., Δn < 0). Enzymatic isotope pairing reactions, which can have site-specific isotopic fractionation factors and atom reservoirs, should express this class of combinatorial isotope effect. Chemical-kinetic isotope effects, which are related to the bond-forming transition state, arise independently and express second-order combinatorial effects. In general, both combinatorial and chemical factors are important for calculating and interpreting clumped-isotope signatures of individual reactions. In many reactions relevant to geochemical oxygen, carbon, and nitrogen cycling, combinatorial isotope pairing likely plays a strong role in the clumped isotope distribution of the products. These isotopic signatures, manifest as either directly bound isotope clumps or as features of a molecule's isotopic anatomy, could be exploited as tracers of biogeochemistry that can

  6. Nitrification and its influence on biogeochemical cycles from the equatorial Pacific to the Arctic Ocean

    PubMed Central

    Shiozaki, Takuhei; Ijichi, Minoru; Isobe, Kazuo; Hashihama, Fuminori; Nakamura, Ken-ichi; Ehama, Makoto; Hayashizaki, Ken-ichi; Takahashi, Kazutaka; Hamasaki, Koji; Furuya, Ken

    2016-01-01

    We examined nitrification in the euphotic zone, its impact on the nitrogen cycles, and the controlling factors along a 7500 km transect from the equatorial Pacific Ocean to the Arctic Ocean. Ammonia oxidation occurred in the euphotic zone at most of the stations. The gene and transcript abundances for ammonia oxidation indicated that the shallow clade archaea were the major ammonia oxidizers throughout the study regions. Ammonia oxidation accounted for up to 87.4% (average 55.6%) of the rate of nitrate assimilation in the subtropical oligotrophic region. However, in the shallow Bering and Chukchi sea shelves (bottom ⩽67 m), the percentage was small (0–4.74%) because ammonia oxidation and the abundance of ammonia oxidizers were low, the light environment being one possible explanation for the low activity. With the exception of the shallow bottom stations, depth-integrated ammonia oxidation was positively correlated with depth-integrated primary production. Ammonia oxidation was low in the high-nutrient low-chlorophyll subarctic region and high in the Bering Sea Green Belt, and primary production in both was influenced by micronutrient supply. An ammonium kinetics experiment demonstrated that ammonia oxidation did not increase significantly with the addition of 31–1560 nm ammonium at most stations except in the Bering Sea Green Belt. Thus, the relationship between ammonia oxidation and primary production does not simply indicate that ammonia oxidation increased with ammonium supply through decomposition of organic matter produced by primary production but that ammonia oxidation might also be controlled by micronutrient availability as with primary production. PMID:26918664

  7. Silica biogeochemical cycle in temperate ecosystems of the Pampean Plain, Argentina

    NASA Astrophysics Data System (ADS)

    Osterrieth, Margarita; Borrelli, Natalia; Alvarez, María Fernanda; Fernández Honaine, Mariana

    2015-11-01

    Silicophytoliths were produced in the plant communities of the Pampean Plain during the Quaternary. The biogeochemistry of silicon is scarcely known in continental environments of Argentina. The aim of this work is to present a synthesis of: the plant production and the presence of silicophytoliths in soils with grasses, and its relationship with silica content in soil solution, soil matrix and groundwaters in temperate ecosystems of the Pampean Plain, Argentina. We quantified the content of silicophytoliths in representative grasses and soils of the area. Mineralochemical determinations of the soils' matrix were made. The concentration of silica was determined in soil solution and groundwaters. The silicophytoliths assemblages in plants let to differenciate subfamilies within Poaceae. In soils, silicophytoliths represent 40-5% of the total components, conforming a stock of 59-72 × 103 kg/ha in A horizons. The concentration of SiO2 in soil solution increases with depth (453-1243 μmol/L) in relation with plant communities, their nutritional requirements and root development. The average concentration of silica in groundwaters is 840 umol/L. In the studied soils, inorganic minerals and volcanic shards show no features of weathering. About 10-40% of silicophytoliths were taxonomically unidentified because of their weathering degrees. The matrix of the aggregates is made up by microaggregates composed of carbon and silicon. The weathering of silicophytoliths is a process that contributes to the formation of amorphous silica-rich matrix of the aggregates. So, silicophytoliths could play an important role in the silica cycle being a sink and source of Si in soils and enriching soil solutions and groundwaters.

  8. [Biogeochemical cycles in natural forest and conifer plantations in the high mountains of Colombia].

    PubMed

    León, Juan Diego; González, María Isabel; Gallardo, Juan Fernando

    2011-12-01

    Plant litter production and decomposition are two important processes in forest ecosystems, since they provide the main organic matter input to soil and regulate nutrient cycling. With the aim to study these processes, litterfall, standing litter and nutrient return were studied for three years in an oak forest (Quercus humboldtii), pine (Pinus patula) and cypress (Cupressus lusitanica) plantations, located in highlands of the Central Cordillera of Colombia. Evaluation methods included: fine litter collection at fortnightly intervals using litter traps; the litter layer samples at the end of each sampling year and chemical analyses of both litterfall and standing litter. Fine litter fall observed was similar in oak forest (7.5 Mg ha/y) and in pine (7.8 Mg ha/y), but very low in cypress (3.5 Mg ha/y). Litter standing was 1.76, 1.73 and 1.3 Mg ha/y in oak, pine and cypress, respectively. The mean residence time of the standing litter was of 3.3 years for cypress, 2.1 years for pine and 1.8 years for oak forests. In contrast, the total amount of retained elements (N, P, S, Ca, Mg, K, Cu, Fe, Mn and Zn) in the standing litter was higher in pine (115 kg/ha), followed by oak (78 kg/ha) and cypress (24 kg/ha). Oak forests showed the lowest mean residence time of nutrients and the highest nutrients return to the soil as a consequence of a faster decomposition. Thus, a higher nutrient supply to soils from oaks than from tree plantations, seems to be an ecological advantage for recovering and maintaining the main ecosystem functioning features, which needs to be taken into account in restoration programs in this highly degraded Andean mountains. PMID:22208100

  9. Nitrification and its influence on biogeochemical cycles from the equatorial Pacific to the Arctic Ocean.

    PubMed

    Shiozaki, Takuhei; Ijichi, Minoru; Isobe, Kazuo; Hashihama, Fuminori; Nakamura, Ken-Ichi; Ehama, Makoto; Hayashizaki, Ken-Ichi; Takahashi, Kazutaka; Hamasaki, Koji; Furuya, Ken

    2016-09-01

    We examined nitrification in the euphotic zone, its impact on the nitrogen cycles, and the controlling factors along a 7500 km transect from the equatorial Pacific Ocean to the Arctic Ocean. Ammonia oxidation occurred in the euphotic zone at most of the stations. The gene and transcript abundances for ammonia oxidation indicated that the shallow clade archaea were the major ammonia oxidizers throughout the study regions. Ammonia oxidation accounted for up to 87.4% (average 55.6%) of the rate of nitrate assimilation in the subtropical oligotrophic region. However, in the shallow Bering and Chukchi sea shelves (bottom ⩽67 m), the percentage was small (0-4.74%) because ammonia oxidation and the abundance of ammonia oxidizers were low, the light environment being one possible explanation for the low activity. With the exception of the shallow bottom stations, depth-integrated ammonia oxidation was positively correlated with depth-integrated primary production. Ammonia oxidation was low in the high-nutrient low-chlorophyll subarctic region and high in the Bering Sea Green Belt, and primary production in both was influenced by micronutrient supply. An ammonium kinetics experiment demonstrated that ammonia oxidation did not increase significantly with the addition of 31-1560 nm ammonium at most stations except in the Bering Sea Green Belt. Thus, the relationship between ammonia oxidation and primary production does not simply indicate that ammonia oxidation increased with ammonium supply through decomposition of organic matter produced by primary production but that ammonia oxidation might also be controlled by micronutrient availability as with primary production. PMID:26918664

  10. Biogeochemical cycles during the species succession from Skeletonema costatum to Alexandrium tamarense in northern Hiroshima Bay

    NASA Astrophysics Data System (ADS)

    Yamamoto, Tamiji; Inokuchi, Yuko; Sugiyama, Teiji

    2004-12-01

    Temporal variations, budgets and cycling patterns of major biophilic elements [phosphorus (P), nitrogen (N) and silicon (Si)] in northern Hiroshima Bay during species succession from Skeletonema costatum to Alexandrium tamarense were documented using data collected on a weekly basis in 1996 and 1997. The budget calculations using a box model were made from the perspective of both particulate formation and decomposition of particulate matter. Thus, the overall circulation patterns of these three elements and their differences were examined in the present study. The turnover time of P was longer than that of N, indicating that the utilization efficiency of P by organisms is low. Along with this, absolute concentrations of dissolved inorganic phosphorus in this season and elemental ratios calculated from various forms of biophilic elements support the idea that DIP is too low for phytoplankton to utilize it. However, the utilization efficiency of P was higher in 1997 than in 1996, when A. tamarense formed a more intensive bloom, suggesting that these organisms could retain elements. When the bloom of A. tamarense formed in 1997, the residence time of water was extremely long, indicating that stagnation of water is a primary factor for bloom formation. In contrast to the large fluctuation in the residence time of water, residence times of biophilic elements were almost constant, indicating the importance of biological processes occurring in the system. On the other hand, in 1996, the residence times of biophilic elements were usually longer compared to that of water. This suggests that the particulate formation process by phytoplankton acts as a "nutrient trap" in combination with estuarine circulation.

  11. Development of advanced process-based model towards evaluation of boundless biogeochemical cycles in terrestrial-aquatic continuum

    NASA Astrophysics Data System (ADS)

    Nakayama, Tadanobu; Maksyutov, Shamil

    2014-05-01

    Recent research shows inland water may play some role in continental biogeochemical cycling though its contribution has remained uncertain due to a paucity of data (Battin et al. 2009). The author has developed process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a-b, 2010, 2011a-b, 2012a-c, 2013; Nakayama and Fujita, 2010; Nakayama and Hashimoto, 2011; Nakayama and Shankman, 2013a-b; Nakayama and Watanabe, 2004, 2006, 2008a-b; Nakayama et al., 2006, 2007, 2010, 2012), which incorporates surface-groundwater interactions, includes up- and down-scaling processes between local, regional and global scales, and can simulate iteratively nonlinear feedback between hydrologic, geomorphic, and ecological processes. In this study, NICE was extended to evaluate global hydrologic cycle by using various global datasets. The simulated result agreed reasonably with that in the previous research (Fan et al., 2013) and extended to clarify further eco-hydrological process in global scale. Then, NICE was further developed to incorporate the biogeochemical cycle including the reaction between inorganic and organic carbons (DOC, POC, DIC, pCO2, etc.) in the biosphere (terrestrial and aquatic ecosystems including surface water and groundwater). The model simulated the carbon cycle, for example, CO2 evasion from inland water in global scale, which is relatively in good agreement in that estimated by empirical relation using the previous pCO2 data (Aufdenkampe et al., 2011; Global River Chemistry Database, 2013). This simulation system would play important role in identification of full greenhouse gas balance of the biosphere and spatio-temporal hot spots in boundless biogeochemical cycle (Cole et al. 2007; Frei et al. 2012). References; Aufdenkampe, A.K., et al., Front. Ecol. Environ., doi:10.1890/100014, 2011. Battin, T.J., et al., Nat. Geosci., 2, 598-600, 2009. Cole, J.J. et al., Ecosystems, doi:10.1007/s10021-006-9013-8, 2007. Fan, Y. et al

  12. Prokaryotic diversity, distribution, and insights into their role in biogeochemical cycling in marine basalts.

    PubMed

    Mason, Olivia U; Di Meo-Savoie, Carol A; Van Nostrand, Joy D; Zhou, Jizhong; Fisk, Martin R; Giovannoni, Stephen J

    2009-02-01

    We used molecular techniques to analyze basalts of varying ages that were collected from the East Pacific Rise, 9 degrees N, from the rift axis of the Juan de Fuca Ridge and from neighboring seamounts. Cluster analysis of 16S rDNA terminal restriction fragment polymorphism data revealed that basalt endoliths are distinct from seawater and that communities clustered, to some degree, based on the age of the host rock. This age-based clustering suggests that alteration processes may affect community structure. Cloning and sequencing of bacterial and archaeal 16S rRNA genes revealed 12 different phyla and subphyla associated with basalts. These include the Gemmatimonadetes, Nitrospirae, the candidate phylum SBR1093 in the bacteria, and in the Archaea Marine Benthic Group B, none of which have been previously reported in basalts. We delineated novel ocean crust clades in the gamma-Proteobacteria, Planctomycetes and Actinobacteria that are composed entirely of basalt-associated microflora, and may represent basalt ecotypes. Finally, microarray analysis of functional genes in basalt revealed that genes coding for previously unreported processes such as carbon fixation, methane oxidation, methanogenesis and nitrogen fixation are present, suggesting that basalts harbor previously unrecognized metabolic diversity. These novel processes could exert a profound influence on ocean chemistry. PMID:18843298

  13. Prokaryotic diversity, distribution, and insights into their role in biogeochemical cycling in marine basalts

    SciTech Connect

    Mason, Olivia U.; Di Meo-Savoie, Carol A.; Van Nostrand, Joy D.; Zhou, Jizhong; Fisk, Martin R.; Giovannoni, Stephen J.

    2008-09-30

    We used molecular techniques to analyze basalts of varying ages that were collected from the East Pacific Rise, 9 oN, from the rift axis of the Juan de Fuca Ridge, and from neighboring seamounts. Cluster analysis of 16S rDNA Terminal Restriction Fragment Polymorphism data revealed that basalt endoliths are distinct from seawater and that communities clustered, to some degree, based on the age of the host rock. This age-based clustering suggests that alteration processes may affect community structure. Cloning and sequencing of bacterial and archaeal 16S rRNA genes revealed twelve different phyla and sub-phyla associated with basalts. These include the Gemmatimonadetes, Nitrospirae, the candidate phylum SBR1093 in the c, andin the Archaea Marine Benthic Group B, none of which have been previously reported in basalts. We delineated novel ocean crust clades in the gamma-Proteobacteria, Planctomycetes, and Actinobacteria that are composed entirely of basalt associated microflora, and may represent basalt ecotypes. Finally, microarray analysis of functional genes in basalt revealed that genes coding for previously unreported processes such as carbon fixation, methane-oxidation, methanogenesis, and nitrogen fixation are present, suggesting that basalts harbor previously unrecognized metabolic diversity. These novel processes could exert a profound influence on ocean chemistry.

  14. Sulfur isotopic analysis of carbonyl sulfide and its application for biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Hattori, Shohei; Kamezaki, Kazuki; Ogawa, Takahiro; Toyoda, Sakae; Katayama, Yoko; Yoshida, Naohiro

    2016-04-01

    Carbonyl sulfide (OCS or COS) is the most abundant gas containing sulfur in the atmosphere, with an average mixing ratio of 500 p.p.t.v. in the troposphere. OCS is suggested as a sulfur source of the stratospheric sulfate aerosols (SSA) which plays an important role in Earth's radiation budget and ozone depletion. Therefore, OCS budget should be validated for prediction of climate change, but the global OCS budget is imbalance. Recently we developed a promising new analytical method for measuring the stable sulfur isotopic compositions of OCS using nanomole level samples: the direct isotopic analytical technique of on-line gas chromatography-isotope ratio mass spectrometry (GC-IRMS) using fragmentation ions S+ (Hattori et al., 2015). The first measurement of the δ34S value for atmospheric OCS coupled with isotopic fractionation for OCS sink reactions in the stratosphere (Hattori et al., 2011; Schmidt et al., 2012; Hattori et al., 2012) explains the reported δ34S value for background stratospheric sulfate, suggesting that OCS is a potentially important source for background (nonepisodic or nonvolcanic) stratospheric sulfate aerosols. This new method measuring δ34S values of OCS can be used to investigate OCS sources and sinks in the troposphere to better understand its cycle. It is known that some microorganisms in soil can degrade OCS, but the mechanism and the contribution to the OCS in the air are still uncertain. In order to determine sulfur isotopic enrichment factor of OCS during degradation via microorganisms, incubation experiments were conducted using strains belonging to the genera Mycobacterium, Williamsia and Cupriavidus, isolated from natural soil environments (Kato et al., 2008). As a result, sulfur isotope ratios of OCS were increased during degradation of OCS, indicating that reaction for OC32S is faster than that for OC33S and OC34S. OCS degradation via microorganisms is not mass-independent fractionation (MIF) process, suggesting that this

  15. Silicon isotope fractionation in bamboo and its significance to the biogeochemical cycle of silicon

    NASA Astrophysics Data System (ADS)

    Ding, T. P.; Zhou, J. X.; Wan, D. F.; Chen, Z. Y.; Wang, C. Y.; Zhang, F.

    2008-03-01

    silicon in pore water and phytoliths in soil is the direct sources of silicon taken up by bamboo roots. A biochemical silicon isotope fractionation exists in process of silicon uptake by bamboo roots. Its silicon isotope fractionation factor ( αbam-wa) is estimated to be 0.9988. Considering the distribution patterns of SiO 2 contents and δ 30Si values among different bamboo organs, evapotranspiration may be the driving force for an upward flow of a silicon-bearing fluid and silica precipitation. Passive silicon uptake and transportation may be important for bamboo, although the role of active uptake of silicic acid by roots may not be neglected. The samples with relatively high δ 30Si values all grew in soils showing high content of organic materials. In contrast, the samples with relatively low δ 30Si values all grew in soil showing low content of organic materials. The silicon isotope composition of bamboo may reflect the local soil type and growth conditions. Our study suggests that bamboos may play an important role in global silicon cycle.

  16. Sedimentary organic matter distributions, burrowing activity, and biogeochemical cycling: Natural patterns and experimental artifacts

    NASA Astrophysics Data System (ADS)

    Michaud, Emma; Aller, Robert, C.; Stora, Georges

    2010-11-01

    The coupling between biogenic reworking activity and reactive organic matter patterns within deposits is poorly understood and often ignored. In this study, we examined how common experimental treatments of sediment affect the burrowing behavior of the polychaete Nephtys incisa and how these effects may interact with reactive organic matter distributions to alter diagenetic transport - reaction balances. Sediment and animals were recovered from a subtidal site in central Long Island Sound, USA. The upper 15 cm of the sediment was sectioned into sub-intervals, and each interval separately sieved and homogenized. Three initial distributions of sediment and organic substrate reactivity were setup in a series of microcosms: (1) a reconstituted natural pattern with surface-derived sediment overlying sediment obtained from progressively deeper material to a depth of 15 cm (Natural); (2) a 15 cm thick sediment layer composed only of surface-derived sediment (Rich); and (3) a 15 cm thick layer composed of uniformally mixed sediment from the original 15 cm sediment profile (Averaged). The two last treatments are comparable to that used in microcosms in many previous studies of bioturbation and interspecific functional interaction experiments. Sediment grain size distributions were 97.5% silt-clay and showed no depth dependent patterns. Sediment porosity gradients were slightly altered by the treatments. Nepthys were reintroduced and aquariums were X-rayed regularly over 5 months to visualize and quantify spatial and temporal dynamics of burrows. The burrowing behaviour of adult populations having similar total biovolume, biomass, abundance, and individual sizes differed substantially as a function of treatment. Burrows in sediment with natural property gradients were much shallower and less dense than those in microcosms with altered gradients. The burrow volume/biovolume ratio was also lower in the substrate with natural organic reactivity gradients. Variation in food

  17. Dense microbial community on a ferromanganese nodule from the ultra-oligotrophic South Pacific Gyre: Implications for biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Shiraishi, Fumito; Mitsunobu, Satoshi; Suzuki, Katsuhiko; Hoshino, Tatsuhiko; Morono, Yuki; Inagaki, Fumio

    2016-08-01

    During Integrated Ocean Drilling Program (IODP) Expedition 329, a deep-sea ferromanganese nodule and surrounding sediment were collected from the South Pacific Gyre, the most oligotrophic oceanic environment on earth. Using a combination of cryo-sectioning and fluorescence-based cell counting techniques, we determined that the microbial cell density at the very surface of the nodule was ∼108 cells cm-3, three orders of magnitude higher than that in the surrounding sediment. Analysis of bacterial and archaeal 16S rRNA gene sequences (∼1400 bp) indicated that the taxonomic composition of the nodule-associated community differed markedly from that of the sediment-associated community. Members of Marine Group I (MGI) Thaumarchaeota are potentially crucial for sustaining the high cell density because both ammonia and Cu were available on the nodule surface, making it suitable for ammonia-oxidizing chemolithoautotrophy mediated by copper enzymes. Combined cryo-sectioning and synchrotron analysis of the nodule surface revealed both hexagonal birnessite resembling δ-MnO2 and triclinic birnessite, minerals characteristic of biogenic oxide and its secondary product, respectively. Regardless of these possible biogenic features, only one gene sequence exhibited some similarity to previously identified manganese-oxidizing bacteria. On the other hand, MGI Thaumarchaeota were assumed as potential candidate of manganese oxidizers because they have multi-copper oxidase that is utilized by most known manganese oxidizers. Therefore, this archaeal group is considered to play a significant ecological role as a primary producer in biogeochemical elemental cycles in the ultra-oligotrophic abyssal plain.

  18. A biogeochemical model for phosphorus and nitrogen cycling in the Eastern Mediterranean Sea. Part 1. Model development, initialization and sensitivity

    NASA Astrophysics Data System (ADS)

    Van Cappellen, P.; Powley, H. R.; Emeis, K.-C.; Krom, M. D.

    2014-11-01

    The Eastern Mediterranean Sea (EMS) is the largest marine basin whose annual primary productivity is limited by phosphorus (P) rather than nitrogen (N). The basin is nearly entirely land-locked and receives substantial external nutrient fluxes, comparable for instance to those of the Baltic Sea. The biological productivity of the EMS, however, is among the lowest observed in the oceans. The water column exhibits very low P and N concentrations with N:P ratios in excess of the Redfield value. These unique biogeochemical features are analyzed using a mass balance model of the coupled P and N cycles in the EMS. The present paper describes the conceptual basis, quantitative implementation and sensitivity of the model. The model is initialized for the year 1950, that is, prior to the large increase in anthropogenic nutrient loading experienced by the EMS during the second half of the 20th century. In the companion paper, the model is used to simulate the P and N cycles during the period 1950-2000. The 1950 model set-up and sensitivity analyses support the following conclusions. Inorganic molar N:P ratios in excess of the 16:1 Redfield value observed in the water column reflect higher-than-Redfield N:P ratios of the external inputs, combined with negligible denitrification. Model simulations imply that the denitrification flux would have to increase by at least a factor of 14, relative to the 1950 flux, in order for the inorganic N:P ratio of the deep waters to approach the Redfield value. The higher

  19. Human Impact on Biogeochemical Cycles and Deposition Dynamics in Karstic Lakes: El Tobar Lake Record (Central Iberian Range, Spain)

    NASA Astrophysics Data System (ADS)

    Barreiro-Lostres, F.; Moreno-Caballud, A.; Giralt, S.; Hillman, A. L.; Brown, E. T.; Abbott, M. B.; Valero-Garces, B. L.

    2014-12-01

    Karstic lakes in the Iberian Range (Central Spain) provide a unique opportunity to test the human impact in the watersheds and the aquatic environments during historical times. We reconstruct the depositional evolution and the changes in biogeochemical cycles of El Tobar karstic lake, evaluating the response and the resilience of this Mediterranean ecosystem to both anthropogenic impacts and climate forcing during the last 1000 years. Lake El Tobar (40°32'N, 3°56'W; 1200 m a.s.l.; see Figure), 16 ha surface area, 20 m max. depth and permanent meromictic conditions, has a relatively large watershed (1080 ha). Five 8 m long sediment cores and short gravity cores where recovered, imaged, logged with a Geotek, described and sampled for geochemical analyses (elemental TOC, TIC, TN, TS), XRF scanner and ICP-MS, and dated (137Cs and 10 14C assays). The record is a combination of: i) laminated dark silts with terrestrial remains and diatoms and ii) massive to banded light silts (mm to cm -thick layers) interpreted as flood deposits. Sediments, TOC, and Br/Ti and Sr/Ca ratios identify four periods of increased sediment delivery occurred about 1500, 1800, 1850 and 1900 AD, coinciding with large land uses changes of regional relevance such as land clearing and increased population. Two main hydrological changes are clearly recorded in El Tobar sequence. The first one, marked by a sharp decrease in Mg, Ca and Si concentrations, took place about 1200 AD, and during a period of increasing lake level, which shifted from shallower to deeper facies and from carbonatic to clastic and organic-rich deposition. This change was likely related to increased water availability synchronous to the transition from the Medieval Climate Anomaly to the Little Ice Age. The second one was a canal construction in 1967 AD when a nearby reservoir provided fresh water influx to the lake, and resulted in stronger meromictic conditions in the system after canal construction, which is marked by lower

  20. Vertical fluxes of biogenic particles and associated biota in the eastern North Pacific: Implications for biogeochemical cycling and productivity

    NASA Astrophysics Data System (ADS)

    Taylor, Gordon T.; Karl, David M.

    1991-09-01

    Previously published data on vertical fluxes of particulate carbon (PC), nitrogen (PN), organisms (MICRO), and extracted adenosine triphosphate (ATP) into screened sediment traps (335 μm) from the VERTEX 5 and ADIOS I programs are reexamined as they relate to biogeochemical cycling and oceanic productivity. The four stations discussed represent an oligotrophic to mesotrophic gradient in total primary production (PT), ranging from 245 to 1141 mg Cm-2 d-1 and a gradient in PC flux from the euphotic zone, ranging from 12 to 164 mg Cm-2 d-1 for particles <335 μm in diameter. Vertical fluxes of PC, PN, MICRO, and ATP decreased as negative power functions of depth with significantly higher depth-dependent losses for ATP fluxes. The flux of intact biota (free, particle-associated, and some active "swimmers," measured microscopically and by extracted ATP) decreased rapidly in the upper 200 m, contributing as much as 52.4% at the most productive station and as little as 1.6% to the flux of PC at oligotrophic stations, remaining relatively constant or increasing slightly (to 3.4 - 9.6% PC flux) between 200 and 2000 m. Multiple regression analyses, expressing fluxes as functions of depth and PT or new production, PN, demonstrated that MICRO and ATP fluxes were more dependent on PT, PN, and depth than bulk PC or PN fluxes. The present analysis illustrates that while sinking particulate organic matter (POM) undergoes rapid attrition in the upper water column, the fluxes of sedimenting biota decrease at even higher rates. Findings support the hypothesis that in oceanic waters, POM sinking from the euphotic zone rapidly becomes a poor habitat for associated microbes, and mechanisms other than remineralization by attached microbes must be invoked to explain observed fluxes and attrition rates. This study also supports the hypothesis that the vertical flux of intact organisms is a more sensitive and less ambiguous record of upper ocean processes than bulk flux measurements of

  1. Dissolved Organic Matter Release During Baseflow and Storm Events and its Potential Impact on Riverine and Biogeochemical Cycles

    NASA Astrophysics Data System (ADS)

    Cammer, S. S.; Canuel, E. A.; Reay, W. G.

    2011-12-01

    Climate change impacts on the hydrologic cycle are expected to alter the delivery of terrestrial organic matter and nutrients to downstream aquatic environments such as estuaries and the coastal ocean. In the coastal zone, dissolved organic matter (DOM) is derived from both aquatic primary production and terrestrial sources and plays an important role in a range of biogeochemical processes including organic matter and nutrient remineralization, which have the potential to impact the water quality of rivers and estuaries. Consequently, understanding the factors controlling the composition and reactivity of exported terrestrial organic matter are important for predicting and managing future climate change. The watershed of Taskinas Creek, located within the Chesapeake National Estuarine Research Reserve, Virginia (USA), is composed of forested and wetland environments that export dissolved organic matter to the York River Estuary, making the location an ideal environment to study how different land uses and hydrologic conditions control the composition and reactivity of DOM exported from a watershed to a downstream estuary. In this study, seasonal sources and fluxes of organic matter exported from forested and wetland sub-environments within Taskinas Creek, Virginia (USA), were compared during baseflow and storm flow conditions. Sources of DOM were determined using a combination of excitation-emission spectrofluorophotometry and parallel factor analysis, specific ultraviolet absorbance, and the fluorescence and freshness indices. Antecedent conditions of soil moisture, temperature, water table height, chromophoric dissolved organic matter concentration and stream discharge were monitored throughout the study. Reactivity of released DOM was assessed using microbial, photochemical and nutrient addition experiments for surface water exported during the rising and falling limbs of storm hydrographs. Preliminary data indicate that baseflow samples from both the forest and

  2. Effects of near-bottom water oxygen concentration on biogeochemical cycling of C, N and S in sediments of the Gulf of Gdansk (southern Baltic)

    NASA Astrophysics Data System (ADS)

    Lukawska-Matuszewska, Katarzyna; Kielczewska, Joanna

    2016-04-01

    Sediments from four sampling sites in the Gulf of Gdansk were sampled to test how different oxygen concentrations in near-bottom water affects biogeochemical cycling of C, N and S. Vertical distributions of content of organic carbon (OC), total nitrogen (TN) and total sulfur (TS) and number of sulfate-reducing bacteria (SRB) in sediments were determined. Pore water total alkalinity (TA), dissolved inorganic carbon (DIC), sulfate, hydrogen sulfide, ammonium and phosphate were analyzed and benthic fluxes of DIC, hydrogen sulfide and ammonium were calculated. Concentrations of OC and TN decreased and concentration of TS increased with sediment depth. Highest concentrations of OC, TN and TS were observed in silty clay sediments from hypoxic and anoxic sediments below the permanent halocline. Organic matter (OM) accumulation in sediments and oxygen deficiency in near-bottom water stimulate preservation of OC and burial of TS in this area. Concentrations of TA, DIC, hydrogen sulfide, ammonium and phosphate in pore water increased, while concentration of sulfate decreased with sediment depth. Hydrogen sulfide, ammonium and phosphate was a significant additional source of TA in pore water under hypoxic and anoxic conditions. Mineralization of OM at oxygen concentrations <2 ml l-1 occurred mainly via bacterial sulfate reduction. Diurnal hydrogen sulfide fluxes under hypoxic conditions ranged from 400 to 1240 μmol m-2 d-1. Ammonium fluxes were estimated on 534 - 924 μmol m-2 d-1. Corresponding fluxes measured under anoxic conditions were 266 μmol m-2 d-1 and 106 μmol m-2 d-1. Sediments under oxic conditions became a place of the intensive regeneration of carbon - DIC flux from sediment reached 2775 μmol m-2 day-1. Sediment-water DIC fluxes under hypoxic and anoxic conditions were much lower and ranged from 1015 to 1208 μmol m-2 d-1.

  3. Life under ice: Investigating microbial-related biogeochemical cycles in the seasonally-covered Great Lake Onego, Russia

    NASA Astrophysics Data System (ADS)

    Thomas, Camille; Ariztegui, Daniel; Victor, Frossard; Emilie, Lyautey; Marie-Elodie, Perga; Life Under Ice Scientific Team

    2016-04-01

    The Great European lakes Ladoga and Onego are important resources for Russia in terms of drinking water, energy, fishing and leisure. Because their northern location (North of Saint Petersburgh), these lakes are usually ice-covered during winter. Due to logistical reasons, their study has thus been limited to the ice-free periods, and very few data are available for the winter season. As a matter of fact, comprehension of large lakes behaviour in winter is very limited as compared to the knowledge available from small subpolar lakes or perennially ice-covered polar lakes. To tackle this issue, an international consortium of scientists has gathered around the « life under ice » project to investigate physical, chemical and biogeochemical changes during winter in Lake Onego. Our team has mainly focused on the characterization and quantification of biological processes, from the water column to the sediment, with a special focus on methane cycling and trophic interactions. A first « on-ice » campaign in March 2015 allowed the sampling of a 120 cm sedimentary core and the collection of water samples at multiple depths. The data resulting from this expedition will be correlated to physical and chemical parameters collected simultaneously. A rapid biological activity test was applied immediately after coring in order to test for microbial activity in the sediments. In situ adenosine-5'-triphosphate (ATP) measurements were carried out in the core and taken as an indication of living organisms within the sediments. The presence of ATP is a marker molecule for metabolically active cells, since it is not known to form abiotically. Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) were extracted from these samples, and quantified. Quantitative polymerase chain reactions (PCR) were performed on archaeal and bacterial 16S rRNA genes used to reconstruct phylogenies, as well as on their transcripts. Moreover, functional genes involved in the methane and nitrogen cycles

  4. Anthropogenic influences on the input and biogeochemical cycling of nutrients and mercury in Great Salt Lake, Utah, USA

    USGS Publications Warehouse

    Naftz, D.; Angeroth, C.; Kenney, T.; Waddell, B.; Darnall, N.; Silva, S.; Perschon, C.; Whitehead, J.

    2008-01-01

    Despite the ecological and economic importance of Great Salt Lake (GSL), little is known about the input and biogeochemical cycling of nutrients and trace elements in the lake. In response to increasing public concern regarding anthropogenic inputs to the GSL ecosystem, the US Geological Survey (USGS) and US Fish and Wildlife Service (USFWS) initiated coordinated studies to quantify and evaluate the significance of nutrient and Hg inputs into GSL. A 6??? decrease in ??15N observed in brine shrimp (Artemia franciscana) samples collected from GSL during summer time periods is likely due to the consumption of cyanobacteria produced in freshwater bays entering the lake. Supporting data collected from the outflow of Farmington Bay indicates decreasing trends in ??15N in particulate organic matter (POM) during the mid-summer time period, reflective of increasing proportions of cyanobacteria in algae exported to GSL on a seasonal basis. The C:N molar ratio of POM in outflow from Farmington Bay decreases during the summer period, supportive of the increased activity of N fixation indicated by decreasing ??15N in brine shrimp and POM. Although N fixation is only taking place in the relatively freshwater inflows to GSL, data indicate that influx of fresh water influences large areas of the lake. Separation of GSL into two distinct hydrologic and geochemical systems from the construction of a railroad causeway in the late 1950s has created a persistent and widespread anoxic layer in the southern part of GSL. This anoxic layer, referred to as the deep brine layer (DBL), has high rates of SO42 - reduction, likely increasing the Hg methylation capacity. High concentrations of methyl mercury (CH3Hg) (median concentration = 24 ng/L) were observed in the DBL with a significant proportion (31-60%) of total Hg in the CH3Hg form. Hydroacoustic and sediment-trap evidence indicate that turbulence introduced by internal waves generated during sustained wind events can temporarily mix the

  5. A dynamic marine iron cycle module coupled to the University of Victoria Earth System Model: the Kiel Marine Biogeochemical Model 2 for UVic 2.9

    NASA Astrophysics Data System (ADS)

    Nickelsen, L.; Keller, D. P.; Oschlies, A.

    2015-05-01

    Marine biological production as well as the associated biotic uptake of carbon in many ocean regions depends on the availability of nutrients in the euphotic zone. While large areas are limited by nitrogen and/or phosphorus, the micronutrient iron is considered the main limiting nutrient in the North Pacific, equatorial Pacific and Southern Ocean. Changes in iron availability via changes in atmospheric dust input are discussed to play an important role in glacial-interglacial cycles via climate feedbacks caused by changes in biological ocean carbon sequestration. Although many aspects of the iron cycle remain unknown, its incorporation into marine biogeochemical models is needed to test our current understanding and better constrain its role in the Earth system. In the University of Victoria Earth System Climate Model (UVic) iron limitation in the ocean was, until now, simulated pragmatically with an iron concentration masking scheme that did not allow a consistent interactive response to perturbations of ocean biogeochemistry or iron cycling sensitivity studies. Here, we replace the iron masking scheme with a dynamic iron cycle and compare the results to available observations and the previous marine biogeochemical model. Sensitivity studies are also conducted with the new model to test the sensitivity of the model to parameterized iron ligand concentrations, the importance of considering the variable solubility of iron in dust deposition, the importance of considering high-resolution bathymetry for the sediment release of iron, the effect of scaling the sedimentary iron release with temperature and the sensitivity of the iron cycle to a climate change scenario.

  6. Microbial Diversity, Distribution and Insight into Their Role in S, Fe and N Biogeochemical Cycling in the Hot Springs at Tengchong Geothermal Fields, Southwest China

    NASA Astrophysics Data System (ADS)

    Li, J.; Peng, X.; Zhang, L.

    2014-12-01

    Ten sediment samples collected from one acidic and three alkaline high temperature hot springs at Tengchong terrestrial geothermal field, Southwest China, were examined by the mineralogical, geochemical, and molecular biological techniques. The mineralogical and geochemical analyses suggested that these hot springs contain relative high concentrations of S, Fe and N chemical species. Specifically, the acidic hot spring was rich in Fe2+, SO42- and NH4+, while the alkaline hot springs were high in NO3-, H2S and S2O3-. Analyses of 16S rRNA sequences showed their bacterial communities were dominated by Aquificae, Cyanobacteria, Deinococci-Thermus, Firmicutes, Proteobacteria, and Thermodesulfobacteria, while the archeal clone libraries were dominated by Desulfurococcales, Sulfolobales, and Thermoproteales. Among them, the potential S-, N- and Fe-related oxidizing and reducing prokaryote were presenting as a relative high proportion but with a great difference in diversity and metabolic approaches of each sample. These findings provide some significant implications for the microbial function in element biogeochemical cycles within the Tengchong geothermal environments: i). the distinct differences in abundance and diversity of microbial communities of geothermal sediments were related to in situ different physicochemical conditions; ii). the S-, N- and Fe-related prokaryote would take advantage of the strong chemical disequilibria in the hot springs; iii). in return, their metabolic activities can promote the transformation of S, Fe and N chemical species, thus founded the bases of biogeochemical cycles in the terrestrial geothermal environments.

  7. The Role of Heterotrophic Microbial Communities in Estuarine C Budgets and the Biogeochemical C Cycle with Implications for Global Warming: Research Opportunities and Challenges.

    PubMed

    Anderson, O Roger

    2016-05-01

    Estuaries are among the most productive and economically important marine ecosystems at the land-ocean interface and contribute significantly to exchange of CO2 with the atmosphere. Estuarine microbial communities are major links in the biogeochemical C cycle and flow of C in food webs from primary producers to higher consumers. Considerable attention has been given to bacteria and autotrophic eukaryotes in estuarine ecosystems, but less research has been devoted to the role of heterotrophic eukaryotic microbes. Current research is reviewed here on the role of heterotrophic eukaryotic microbes in C biogeochemistry and ecology of estuaries, with particular attention to C budgets, trophodynamics, and the metabolic fate of C in microbial communities. Some attention is given to the importance of these processes in climate change and global warming, especially in relation to sources and sinks of atmospheric CO2 , while also documenting the current paucity of research on the role of eukaryotic microbes that contribute to this larger question of C biogeochemistry and the environment. Some recommendations are made for future directions of research and opportunities of applying newer technologies and analytical approaches to a more refined analysis of the role of C in estuarine microbial community processes and the biogeochemical C cycle. PMID:26507684

  8. Using Multiple Tracer Approaches to Investigate the Influence of Stream-Groundwater Exchange on Biogeochemical Cycling in the McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Gooseff, M. N.; Bernzott, E.; McKnight, D. M.; Lyons, W. B.

    2012-04-01

    Streams in the McMurdo Dry Valleys of Antarctica are connected to extensive hyporheic zones through which stream water exchanges during the 10-12 week flow season. We have used a variety of study designs and techniques to determine how hyporheic exchange influences biogeochemical cycling in these glacial meltwater streams. Synoptic sampling campaigns and subsequent simulation of major ion concentration changes downstream have provided evidence that hyporheic exchange is responsible for the very high chemical weathering rates we observe in these streams. Data from stream tracer experiments, including nutrient additions, and subsequent transport modeling have indicated that nitrogen and phosphorous uptake occur both in the channel and within the hyporheic zone, under enriched nutrient conditions. Furthermore, these experiments indicate incomplete denitrification in the algal mats that cover these streambeds. Long timescale (i.e. on the order of weeks) hyporheic exchange has been observed using stable isotopes as a natural tracer of exchange and mixing of surface and hyporheic waters. We have also recently made use of high temporal frequency electrical conductivity measurements from glacier sources to stream outflows to determine the intensity of hyporheic exchange in theses streams continuously. Our findings from these different approaches indicate that Dry Valley streams are intimately linked with their hyporheic zones, which are hot spots for biogeochemical cycling within this desert landscape.

  9. Up-scaling of process-based eco-hydrology model to global scale for identification of hot spots in boundless biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Nakayama, T.; Maksyutov, S. S.

    2013-12-01

    Recent research shows inland water may play some role in continental biogeochemical cycling though its contribution has remained uncertain due to a paucity of data (Battin et al. 2009). The author has developed process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a-b, 2010, 2011a-b, 2012a-c, 2013; Nakayama and Fujita, 2010; Nakayama and Hashimoto, 2011; Nakayama and Shankman, 2013a-b; Nakayama and Watanabe, 2004, 2006, 2008a-b; Nakayama et al., 2006, 2007, 2010, 2012), which includes surface-groundwater interactions and down-scaling process from regional to local simulation with finer resolution, and can simulate iteratively nonlinear feedback between hydrologic, geomorphic, and ecological processes in east Asia. In this study, NICE was further extended to implement map factor and non-uniform grid through up-scaling process of coordinate transformation from rectangular to longitude-latitude system applicable to global scale. This improved model was applied to several basins in Eurasia to evaluate the impact of coordinate transformation on eco-hydrological changes. Simulated eco-hydrological process after up-scaling corresponded reasonably to that in the original there after evaluating the effect of different latitude. Then, the model was expanded to evaluate global hydrologic cycle by using various global datasets. The simulated result agreed reasonably with that in the previous research (Fan et al., 2013) and extended to clarify further eco-hydrological process in global scale. This simulation system would play important role in identification of spatio-temporal hot spots in boundless biogeochemical cycle along terrestrial-aquatic continuum for global environmental change (Cole et al. 2007; Battin et al. 2009; Frei et al. 2012).

  10. A model of biogeochemical cycling of phosphorus, nitrogen, oxygen, and sulphur in the ocean: One step toward a global climate model

    NASA Astrophysics Data System (ADS)

    Shaffer, Gary

    1989-02-01

    An ocean model has been developed which, for prescribed physics, deals with interrelationships between chemical distributions, biogeochemical sinks and sources, chemical reactions at redox fronts, and transports across the air-sea and sediment-water interfaces. In its first application here, the model focuses on biogeochemical cycling of phosphorus, nitrogen, oxygen, and sulphur in an ocean forced by river input of nutrients. This is a natural starting point for a global climate model since ocean circulation and biology determine atmospheric CO2 concentrations for a given inventory of inorganic C and oceanic production is controlled mainly by the availability of inorganic P and/or N. A general approach is taken to look at oxic versus anoxic conditions, P versus N limitation of primary production, with or without inorganic removal of phosphate to the sediments. As demanded by this approach, the model is nonlinear and continuous in a vertical coordinate. To focus on the biogeochemical aspects, ocean physics are kept as simple as possible. Cold, oxygen-rich water sinks at high latitudes and is upwelled with a constant velocity. Turbulent mixing is parameterized with a constant, vertical diffusion coefficient. The biogeochemical processes considered are new production, burial, nitrogen fixation, phosphorite formation, and three types of organic decomposition: oxidation with O2, denitrification, and sulphate reduction. Organic matter is taken to consist of a high- and a low-reactive fraction. The chemical species considered explicitly are PO43--P, NO3--N, O2, NH4+-N and H2S-S. Results indicate that a change from oxic to weakly anoxic conditions at middepths in a P-limited ocean would lead to strong local denitrification and low nitrate concentrations throughout the water column. New production would also become dominated by nitrogen fixers. Geological evidence implies that anoxic conditions in the water column have been rare in the Phanerozoic ocean. Both phosphorite

  11. Carbon Nanotubes Influence the Enzyme Activity of Biogeochemical Cycles of Carbon, Nitrogen, Phosphorus and the Pathogenesis of Plants in Annual Agroecosystems

    NASA Astrophysics Data System (ADS)

    Vaishlya, O. B.; Osipov, N. N.; Guseva, N. V.

    2015-09-01

    We conducted pre-sowing seed treatment of spring wheat carbon nanotubes modified with thionyl chloride, ethylene diamine, azobenzole, and dodecylamine. CNTs did not disrupt the structure of the crop, but the activity of extracellular enzymes in the rhizosphere of plants in the flowering stage changed: laccase works more poorly in the variant of the CNTs with the amino groups exochitinase and phosphatase activity increased in the case of chlorinated CNTs, OH and COOH groups on the surface of the nanotubes twice accelerate work β-glucosidase. The changes observed in the biogeochemical cycles in the rhizosphere are a possible cause of the effect of nanotubes on the development of epidemic diseases of wheat.

  12. Biogeochemical Cycling of Fe, S, C, N, and Mo in the 3.2 Ga ocean: Constraints from DXCL-DP Black Shales from Pilbara, Western Australia

    NASA Astrophysics Data System (ADS)

    Yamaguchi, K. E.; Naraoka, H.; Ikehara, M.; Ito, T.; Kiyokawa, S.

    2014-12-01

    Records of geochemical cycling of bio-essential, redox-sensitive elements have keys to decipher mysteries of the co-evolution of Earth and life. To obtain insight into biogeochemical cycling of those elements and early evolution of microbial biosphere from high-quality samples, we drilled through Mesoarchean strata in coastal Pilbara (Dixon Island-Cleaverville Drilling Project, see Yamaguchi et al., 2009; Kiyokawa et al., 2012), and obtained 3.2 Ga old drillcores (CL1, CL2, and DX) of sulfide-rich black shales in the Cleaverville Group, Pilbara Supergroup. We conducted a systematic geochemical study involving sequential extractions of Fe, S, C, and N for phase-dependent contents (e.g., pyrite-Fe, reactive-Fe, highly reactive-Fe, unreactive-Fe, pyrite-S, sulfate-S, organic-S, elemental-S, Corg, Ccarb, Norg, and Nclay) and their stable isotope compositions, micro FT-IR and laser Raman spectroscopy for extracted kerogen, in addition to major and trace (redox-sensitive; e.g., Mo) element analysis, for >100 samples. Here we integrate our recent multidisciplinary investigations into the redox state of ocean and nature of microbial biosphere in the ocean 3.2 Ga ago. All of the obtained data are very difficult to explain only by geochemical processes in strictly anoxic environments, where both atmosphere and oceans were completely anoxic, like an environment before the inferred "Great Oxidation Event" when pO2 was lower than 0.00001 PAL (e.g., Holland, 1994). Our extensive data set consistently suggests that oxygenic photosynthesis, bacterial sulfate reduction, and microbially mediated redox-cycling of nitrogen, possibly involving denitrification and N2-fixation, are very likely to have been operating, and may be used as a strong evidence for at least local and temporal existence of oxidized environment as far back as 3.2 Ga ago. Modern-style biogeochemical cycling of Fe, S, C, N, and Mo has been operating since then. The atmosphere-hydrosphere system 3.2 Ga ago would have

  13. Biogeochemical characterization of the Cointzio reservoir (Morelia, Mexico) and identification of a watershed-dependent cycling of nutrients

    NASA Astrophysics Data System (ADS)

    Némery, J.; Alvarado, R.; Gratiot, N.; Duvert, C.; Mahé, F.; Duwig, C.; Bonnet, M.; Prat, C.; Esteves, M.

    2009-12-01

    to May), the baseflow is much more concentrated in dissolved nutrients. On the contrary, the high flows (June to October) bring a high amount of suspended sediments (up to 50g/L) that transport nutrients such as particulate P. Despite the high turbidity level of the reservoir, chlorophyll a concentrations appear important (70 µg/L during the dry season) especially in the first five meters of the water column. The phytoplankton community is dominated by Euglenophyta and Cyanobacteria groups typical of eutrophic waters. This study is the first complete biogeochemical survey of the Cointzio watershed. Results acquired will be used in a 3D biogeochemical model ELMO (Bonnet and Wessen, 2001) with the objective of providing a quantitative and update analysis of the water quality. The model already reproduced thermal stratification but furthers runs are needed to calibrate the biogeochemical modules and provide an efficient tool to reservoir’s managers.

  14. Road Salt Accumulation and Wash-out in Stormwater Detention Basins: Patterns and Implications for Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    McPhillips, L. E.; Walter, M. T.

    2014-12-01

    There is increasing evidence that salt application to roads and parking lots in winter is driving a rise in chloride concentrations in streams in the northeastern United States. Our research focuses specifically on salt dynamics in stormwater detention basins, which receive runoff directly from parking lots and detain it before it reaches the stream. The four study basins are located on the Cornell University campus in Ithaca, NY USA. Between summer 2012 and 2014, soil electrical conductivity was continuously monitored inside and outside the basins using Decagon 5TE sensors and dataloggers. In two basins which drain stormwater quickly, conductivity levels changed minimally over the year. However, in the other two basins which drain much slower and often are saturated, conductivity increased through the winter, peaking at 8-10 mS/cm, and then took several months to decrease to baseline levels; thus the basins served as a source of salt to outflowing water even into the summer. This annual variation in soil salinity has implications for plant and microbial communities living in these basins. Research by colleagues has indicated that changing salinity can alter microbial communities and impact biogeochemical processes that play a role in water quality remediation. Thus we are also investigating the impact of salinity on denitrification rates in these basins. All of this information will help us understand what role stormwater detention basins are playing in controlling fluxes of road salt in watersheds, as well as how changing salinity influences the ecosystem services provided by these basins.

  15. An approach to quantify sources, seasonal change, and biogeochemical processes affecting metal loading in streams: Facilitating decisions for remediation of mine drainage

    USGS Publications Warehouse

    Kimball, B.A.; Runkel, R.L.; Walton-Day, K.

    2010-01-01

    Historical mining has left complex problems in catchments throughout the world. Land managers are faced with making cost-effective plans to remediate mine influences. Remediation plans are facilitated by spatial mass-loading profiles that indicate the locations of metal mass-loading, seasonal changes, and the extent of biogeochemical processes. Field-scale experiments during both low- and high-flow conditions and time-series data over diel cycles illustrate how this can be accomplished. A low-flow experiment provided spatially detailed loading profiles to indicate where loading occurred. For example, SO42 - was principally derived from sources upstream from the study reach, but three principal locations also were important for SO42 - loading within the reach. During high-flow conditions, Lagrangian sampling provided data to interpret seasonal changes and indicated locations where snowmelt runoff flushed metals to the stream. Comparison of metal concentrations between the low- and high-flow experiments indicated substantial increases in metal loading at high flow, but little change in metal concentrations, showing that toxicity at the most downstream sampling site was not substantially greater during snowmelt runoff. During high-flow conditions, a detailed temporal sampling at fixed sites indicated that Zn concentration more than doubled during the diel cycle. Monitoring programs must account for diel variation to provide meaningful results. Mass-loading studies during different flow conditions and detailed time-series over diel cycles provide useful scientific support for stream management decisions.

  16. Statistical evaluation of biogeochemical variables affecting spatiotemporal distributions of multiple free metal ion concentrations in an urban estuary.

    PubMed

    Dong, Zhao; Lewis, Christopher G; Burgess, Robert M; Coull, Brent; Shine, James P

    2016-05-01

    Free metal ion concentrations have been recognized as a better indicator of metal bioavailability in aquatic environments than total dissolved metal concentrations. However, our understanding of the determinants of free ion concentrations, especially in a metal mixture, is limited, due to underexplored techniques for measuring multiple free metal ions simultaneously. In this work, we performed statistical analyses on a large dataset containing repeated measurements of free ion concentrations of Cu, Zn, Pb, Ni, and Cd, the most commonly measured metals in seawater, at five inshore locations in Boston Harbor, previously collected using an in-situ equilibrium-based multi-metal free ion sampler, the 'Gellyfish'. We examined correlations among these five metals by season, and evaluated effects of 10 biogeochemical variables on free ion concentrations over time and location through multivariate regressions. We also explored potential clustering among the five metals through a principal component analysis. We found significant correlations among metals, with varying patterns over season. Our regression results suggest that instead of dissolved metals, pH, salinity, temperature and rainfall were the most significant determinants of free metal ion concentrations. For example, a one-unit decrease in pH was associated with a 2.2 (Cd) to 99 (Cu) times increase in free ion concentrations. This work is among the first to reveal key contributors to spatiotemporal variations in free ion concentrations, and demonstrated the usefulness of the Gellyfish sampler in routine sampling of free ions within metal mixtures and in generating data for statistical analyses. PMID:26901477

  17. MEDUSA-2.0: an intermediate complexity biogeochemical model of the marine carbon cycle for climate change and ocean acidification studies

    NASA Astrophysics Data System (ADS)

    Yool, A.; Popova, E. E.; Anderson, T. R.

    2013-10-01

    MEDUSA-1.0 (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification) was developed as an "intermediate complexity" plankton ecosystem model to study the biogeochemical response, and especially that of the so-called "biological pump", to anthropogenically driven change in the World Ocean (Yool et al., 2011). The base currency in this model was nitrogen from which fluxes of organic carbon, including export to the deep ocean, were calculated by invoking fixed C:N ratios in phytoplankton, zooplankton and detritus. However, due to anthropogenic activity, the atmospheric concentration of carbon dioxide (CO2) has significantly increased above its natural, inter-glacial background. As such, simulating and predicting the carbon cycle in the ocean in its entirety, including ventilation of CO2 with the atmosphere and the resulting impact of ocean acidification on marine ecosystems, requires that both organic and inorganic carbon be afforded a more complete representation in the model specification. Here, we introduce MEDUSA-2.0, an expanded successor model which includes additional state variables for dissolved inorganic carbon, alkalinity, dissolved oxygen and detritus carbon (permitting variable C:N in exported organic matter), as well as a simple benthic formulation and extended parameterizations of phytoplankton growth, calcification and detritus remineralisation. A full description of MEDUSA-2.0, including its additional functionality, is provided and a multi-decadal spin-up simulation (1860-2005) is performed. The biogeochemical performance of the model is evaluated using a diverse range of observational data, and MEDUSA-2.0 is assessed relative to comparable models using output from the Coupled Model Intercomparison Project (CMIP5).

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

    PubMed

    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. PMID:23718903

  19. Studying Microbial Mat Functioning Amidst "Unexpected Diversity": Methodological Approaches and Initial Results from Metatranscriptomes of Mats Over Diel cycles, iTags from Long Term Manipulations, and Biogeochemical Cycling in Simplified Microbial Mats Constructed from Cultures

    NASA Astrophysics Data System (ADS)

    Bebout, B.; Bebout, L. E.; Detweiler, A. M.; Everroad, R. C.; Lee, J.; Pett-Ridge, J.; Weber, P. K.

    2014-12-01

    Microbial mats are famously amongst the most diverse microbial ecosystems on Earth, inhabiting some of the most inclement environments known, including hypersaline, dry, hot, cold, nutrient poor, and high UV environments. The high microbial diversity of microbial mats makes studies of microbial ecology notably difficult. To address this challenge, we have been using a combination of metagenomics, metatranscriptomics, iTags and culture-based simplified microbial mats to study biogeochemical cycling (H2 production, N2 fixation, and fermentation) in microbial mats collected from Elkhorn Slough, Monterey Bay, California. Metatranscriptomes of microbial mats incubated over a diel cycle have revealed that a number of gene systems activate only during the day in Cyanobacteria, while the remaining appear to be constitutive. The dominant cyanobacterium in the mat (Microcoleus chthonoplastes) expresses several pathways for nitrogen scavenging undocumented in cultured strains, as well as the expression of two starch storage and utilization cycles. Community composition shifts in response to long term manipulations of mats were assessed using iTags. Changes in community diversity were observed as hydrogen fluxes increased in response to a lowering of sulfate concentrations. To produce simplified microbial mats, we have isolated members of 13 of the 15 top taxa from our iTag libraries into culture. Simplified microbial mats and simple co-cultures and consortia constructed from these isolates reproduce many of the natural patterns of biogeochemical cycling in the parent natural microbial mats, but against a background of far lower overall diversity, simplifying studies of changes in gene expression (over the short term), interactions between community members, and community composition changes (over the longer term), in response to environmental forcing.

  20. A biogeochemical model for phosphorus and nitrogen cycling in the Eastern Mediterranean Sea. Part 2. Response of nutrient cycles and primary production to anthropogenic forcing: 1950-2000

    NASA Astrophysics Data System (ADS)

    Powley, H. R.; Krom, M. D.; Emeis, K.-C.; Van Cappellen, P.

    2014-11-01

    Anthropogenic inputs of nutrient phosphorus (P) and nitrogen (N) to the Eastern Mediterranean Sea (EMS) increased significantly after 1950. Nonetheless, the EMS remained ultra-oligotrophic, with eutrophication only affecting a restricted number of nearshore areas. To better understand this apparent contradiction, we reconstructed the external inputs of reactive P and N to the EMS for the period 1950 to 2000. Although the inputs associated with atmospheric deposition and river discharge more than doubled, the inflow of surface water from the Western Mediterranean Sea (WMS) remained the dominant source of nutrient P and N to the EMS during the second half of the 20th century. The combined external input of reactive P rose by 24% from 1950 to 1985, followed by a slight decline. In contrast, the external reactive N input increased continuously from 1950 to 2000, with a 62% higher input in 2000 compared to 1950. When imposing the reconstructed inputs to the dynamic model of P and N cycling in the EMS developed in the companion paper, a maximum increase of primary production of only 16% is predicted. According to the model, integrated over the period 1950-2000, outflow of Levantine Intermediate Water (LIW) to the WMS exported the equivalent of about one third of the P supplied in excess of the 1950 input, while another one third was translocated to the Eastern Mediterranean Deep Water (EMDW). Together, both mechanisms efficiently counteracted enhanced P input to the EMS, by drawing nutrient P away from primary producers in the surface waters. Furthermore, between 1950 and 2000, inorganic and organic dissolved N:P ratios increased in all water masses. Thus, the EMS became even more P limited because of anthropogenic nutrient inputs. A model simulation incorporating the circulation changes accompanying the Eastern Mediterranean Transient (EMT) between 1987 and 2000 yielded a 4% increase of EMS primary productivity relative to the baseline scenario.

  1. Genetic and biogeochemical investigation of sedimentary nitrogen cycling communities responding to tidal and seasonal dynamics in Cape Fear River Estuary

    NASA Astrophysics Data System (ADS)

    Lisa, Jessica A.; Song, Bongkeun; Tobias, Craig R.; Hines, David E.

    2015-12-01

    Tidal and seasonal fluctuations in the oligohaline reaches of estuaries may alter geochemical features that influence structure and function of microbial communities involved in sedimentary nitrogen (N) cycling. In order to evaluate sediment community responses to short-term (tidal) and long-term (seasonal) changes in different tidal regimes, nitrogen cycling rates and genes were quantified in three sites that span a range of tidal influence in the upper portion of the Cape Fear River Estuary. Environmental parameters were monitored during low and high tides in winter and spring. 15N tracer incubation experiments were conducted to measure nitrification, denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonia (DNRA). Abundances of functional genes including bacterial and archaeal ammonia monooxygenase (amoA), nitrite reductases (nirS and nrfA), nitrous oxide reductase (nosZ), and hydrazine oxidoreductase (hzo) were measured using quantitative PCR assays. Denitrification rates were highest among the measured N cycling processes while bacteria carrying nrfA genes were most abundant. A discernable pattern in the short-term variation of N cycling rates and gene abundance was not apparent under the different tidal regimes. Significant seasonal variation in nitrification, denitrification, and anammox rates as well as bacterial amoA, nirS and nosZ gene abundance was observed, largely explained by increases in substrate availability during winter, with sediment ammonium playing a central role. These results suggest that the coupling of nitrification to N removal pathways is primarily driven by organic carbon mineralization and independent of tidal or salinity changes. Finally, changes in denitrification and nitrification activities were strongly reflected by the abundance of the respective functional genes, supporting a linkage between the structure and function of microbial communities.

  2. Long-term increase in mesozooplankton biomass in the Sargasso Sea: Linkage to climate and implications for food web dynamics and biogeochemical cycling

    NASA Astrophysics Data System (ADS)

    Steinberg, Deborah K.; Lomas, Michael W.; Cope, Joseph S.

    2012-03-01

    Changes in zooplankton biomass and species composition over long time scales can have significant effects on biogeochemical cycling and transfer of energy to higher trophic levels. We analyzed size-fractionated mesozooplankton biomass (>200μm) from biweekly to monthly day and night tows taken from 1994 to 2010 in the epipelagic zone at the Bermuda Atlantic Time series Study (BATS) site in the oligotrophic North Atlantic subtropical gyre. During this 17-year period total mesozooplankton biomass increased 61% overall, although a few short-term downturns occurred over the course of the time series. The overall increase was higher in the nighttime compared to daytime, resulting in an increase in calculated diel vertical migrator biomass. The largest seasonal increase in total biomass was in the late-winter to spring (February-April). Associated with the larger increase in late-winter/spring biomass was a shift in the timing of annual peak biomass during the latter half of the time series (from March/April to a distinct March peak for all size fractions combined, and April to March for the 2-5 mm size fractions). Zooplankton biomass was positively correlated with sea-surface temperature, water column stratification, and primary production, and negatively correlated with mean temperature between 300 and 600 m. Significant correlations exist between multidecadal climate indices-the North Atlantic Oscillation plus three different Pacific Ocean climate indices, and BATS zooplankton biomass, indicating connections between patterns in climate forcing and ecosystem response. Resultant changes in biogeochemical cycling include an increase in the magnitude of both active carbon flux by diel vertical migration and passive carbon flux of fecal pellets as components of the export flux. The most likely mechanism driving the zooplankton biomass increase is bottom-up control by smaller phytoplankton, which has also increased in biomass and production at BATS, translating up the

  3. Metagenomics, single cell genomics, and steady-state free energy flux provide insight into the biogeochemical cycling of deep, meteoric water

    NASA Astrophysics Data System (ADS)

    Magnabosco, C.; Lau, C. M.; Ryan, K.; Kieft, T. L.; Snyder, L.; Sherwood Lollar, B.; Lacrampe Couloume, G.; Hendrickson, S.; Pullin, M. J.; Slater, G. F.; Simkus, D.; Borgonie, G.; van Heerden, E.; Kuloyo, O.; Maleke, M.; Tlalajoe, T.; Vermeulen, J.; Vermeulen, F.; Munro, A.; Pienaar, M.; Stepanauskas, R.; Grim, S. L.; Onstott, T. C.

    2013-12-01

    Prior to the onset of high-throughput sequencing, the study of biogeochemical cycling in the terrestrial deep subsurface was limited to geochemical, thermodynamic, culture dependent microbial and low-throughput molecular analyses. Here, we present an integration of these traditional methods with high-throughput metagenomic and single cell analysis of 3.1 km deep water collected from a borehole (TT107) located in AngloGold Ashanti's TauTona Au Mine of South Africa and intersecting a fracture within a Witwatersrand Supergroup quartzite. The low salinity fracture water encountered at this depth is meteoric in origin and has a subsurface residence time on the order of a few thousand years. Aqueous geochemistry and estimated steady-state free energy flux values suggest that redox reactions are driven by the oxidation of abundant, energy-rich substrates including H2, CO, CH4, formate, and propanoate. The majority of the metagenome's sequences related to the phyla Firmicutes and Proteobacteria, which contain several bacterial species that are likely to exhibit chemoautotrophic metabolism. Sequence data confirms that many of these bacteria have the ability reduce of sulfur and nitrogen species via dissimilatory pathways. Thermincola were the most abundant firmicutes at this location and were sequenced at the single cell level. Notably, Thermincola sp. are capable of reducing metals and may utilize energy rich manganese reduction pathways at TT107. The CH4 at this site is of abiological origin (δ13C-C1-3 = -43.5 to -44.3 VPDB; δ2H-C1-3 = -345 to -200 VSMOW) despite the metagenome containing several sequences that are closely related to methanogens in the archaeal phyla Euryarchaeota. Alternatively, these archaea may belong to a group of euryarchaetoa commonly referred to as anaerobic mehanotrophic archaea (ANME) - suggesting that anaerobic oxidation (AOM) of abiogenic CH4 coupled to the reduction of sulfate species may be occurring at this site. Sequences for pmoA and s

  4. 17 years of biogeochemical data from a remote tropical montane forest in Ecuador: Tracing changes in the N cycle under environmental change

    NASA Astrophysics Data System (ADS)

    Leimer, Sophia; Velescu, Andre; Valarezo, Carlos; Wilcke, Wolfgang

    2015-04-01

    Water-bound N cycling in temperate terrestrial ecosystems of the Northern Hemisphere is today mainly inorganic because of anthropogenic release of reactive N to the environment. In little-industrialized and remote areas, in contrast, a larger part of N cycling occurs as dissolved organic N (DON). Since 1998, we intensively study the biogeochemical cycle of a north Andean tropical montane forest in Ecuador. The resulting data set offers the unique opportunity to assess the effects of environmental change on a remote ecosystem. Rainfall, throughfall, stemflow, litter leachate, soil solution in 0.15 and 0.30 m soil depth, and stream water were sampled in weekly resolution and analyzed for total N, NO3-N, NH4-N, DON, total organic C, PO4-P, total dissolved phosphorus, Cl, K, Ca, Mg, and Na. Furthermore, ecological time-series data from other disciplines (e.g., climate or phenological data) is available for the study site, resulting in over 500 ecosystem variables by now. The data set was aggregated to monthly means and analyzed for temporal trends with the non-parametric Seasonal Mann-Kendall test. Our results show that the N cycle changed markedly during the study period along with increasing N deposition and reduced soil moisture. The DON concentrations and the fractional contribution of DON to total N significantly decreased in rainfall, throughfall, and soil solutions. This turn toward inorganic N was most pronounced in rainfall and became weaker along the flow path of water through the system until it disappeared in stream water. Decreasing organic contributions to N cycling were not only caused by increasing inorganic N input but also by reduced DON production and/or enhanced DON decomposition. Such an accelerated DON decomposition might be attributable to less waterlogging and higher nutrient availability, which both were observed at our study site. Significantly increasing NO3-N concentrations and NO3-N/NH4-N concentration ratios in throughfall and litter

  5. The biogeochemical footprint of agricultural soil erosion

    NASA Astrophysics Data System (ADS)

    Govers, Gerard; Van Oost, Kristof; Wang, Zhengang

    2015-04-01

    Global biogeochemical cycles are a key component of the functioning of the Earth System: these cycles are all, to a varying extent, disturbed by human activities which not only has dramatic consequences for the global climate but also for the acidity of the world's oceans. It is only relatively recently that the role of lateral fluxes related to surface water movement and soil erosion and deposition (and the way those fluxes are modified by human action) is explicitly considered by the scientific community. In this paper we present an overview of our present-day understanding of the role of agricultural soil erosion in the global cycles of carbon, nitrogen, phosphorous and silica. We discuss the major processes through which erosion affects these global cycles and pay particular attention to the knowledge gaps that prevent us from accurately assessing the impact of soil erosion on global biogeochemical cycling at different temporal scales. Furthering our understanding (and better constraining our estimates) will require progress both in terms of model development and process understanding. Research needs can be most clearly identified with respect to soil organic carbon: (i) at present, large-scale soil erosion (and deposition) models are poorly constrained so that the amount of carbon mobilised by erosion (and its fate) cannot be accurately estimated and (ii) the fate of soil organic carbon buried by deposition or delivered to river network is poorly understood. Uncertainties for N, P and Si are larger than those for C as we have less information on the amount of these elements stored in agricultural soils and/or do not fully understand how these elements cycle through the soil/plant system. Agricultural soil erosion does not affect soil functioning through its effect on biogeochemical cycling. Erosion directly affects soil hydrological functioning and is likely to affect weathering processes and soil production. Addressing all these issues requires the

  6. Microbial Carbon Cycling in Permafrost-Affected Soils

    SciTech Connect

    Vishnivetskaya, T.; Liebner, Susanne; Wilhelm, Ronald; Wagner, Dirk

    2011-01-01

    The Arctic plays a key role in Earth s climate system as global warming is predicted to be most pronounced at high latitudes and because one third of the global carbon pool is stored in ecosystems of the northern latitudes. In order to improve our understanding of the present and future carbon dynamics in climate sensitive permafrost ecosystems, present studies concentrate on investigations of microbial controls of greenhouse gas fluxes, on the activity and structure of the involved microbial communities, and on their response to changing environmental conditions. Permafrost-affected soils can function as both a source and a sink for carbon dioxide and methane. Under anaerobic conditions, caused by flooding of the active layer and the effect of backwater above the permafrost table, the mineralization of organic matter can only be realized stepwise by specialized microorganisms. Important intermediates of the organic matter decomposition are hydrogen, carbon dioxide and acetate, which can be further reduced to methane by methanogenic archaea. Evolution of methane fluxes across the subsurface/atmosphere boundary will thereby strongly depend on the activity of anaerobic methanogenic archaea and obligately aerobic methane oxidizing proteobacteria, which are known to be abundant and to significantly reduce methane emissions in permafrost-affected soils. Therefore current studies on methane-cycling microorganisms are the object of particular attention in permafrost studies, because of their key role in the Arctic methane cycle and consequently of their significance for the global methane budget.

  7. The biogeochemical cycling of trace metals in the water column of Lake Sammamish, Washington: response to seasonally anoxic conditions

    USGS Publications Warehouse

    Balistrieri, L.S.; Murray, J.W.; Paul, B.

    1992-01-01

    Spatial and temporal changes in the redox conditions of the bottom waters result in increases in dissolved Co and Ni concentrations, peaks in particulate Co profiles, decreases in dissolved Cu and Cr concentrations, and significant changes in dissolved metal speciation during stagnation. The redox-driven cycling of Fe and Mn in the hypolimnion has a dramatic effect on Co disturbutions, a slight effect on Ni concentrations, and virtually no effect on Cd, Cu, Cr, and Zn concentrations. Biological uptake and regeneration processes result in a correlation between Zn and silicate concentrations throughout the water column, and it appears that biological cycling may also influence the distribution of Cd. During the sulfidic phase of stagnation dissolved Cd concentrations in the bottom-waters may be controlled by metal-sulfide precipitation, Cr(VI) is probably reduced to more particle-reactive Cr(III) and removed by settling particles, and Cu(II) is most likely reduced to Cu(I) and precipitated as a metal-sulfide phase. -from Authors

  8. FeCycle: Attempting an iron biogeochemical budget from a mesoscale SF6 tracer experiment in unperturbed low iron waters

    NASA Astrophysics Data System (ADS)

    Boyd, P. W.; Law, C. S.; Hutchins, D. A.; Abraham, E. R.; Croot, P. L.; Ellwood, M.; Frew, R. D.; Hadfield, M.; Hall, J.; Handy, S.; Hare, C.; Higgins, J.; Hill, P.; Hunter, K. A.; Leblanc, K.; Maldonado, M. T.; McKay, R. M.; Mioni, C.; Oliver, M.; Pickmere, S.; Pinkerton, M.; Safi, K.; Sander, S.; Sanudo-Wilhelmy, S. A.; Smith, M.; Strzepek, R.; Tovar-Sanchez, A.; Wilhelm, S. W.

    2005-12-01

    An improved knowledge of iron biogeochemistry is needed to better understand key controls on the functioning of high-nitrate low-chlorophyll (HNLC) oceanic regions. Iron budgets for HNLC waters have been constructed using data from disparate sources ranging from laboratory algal cultures to ocean physics. In summer 2003 we conducted FeCycle, a 10-day mesoscale tracer release in HNLC waters SE of New Zealand, and measured concurrently all sources (with the exception of aerosol deposition) to, sinks of iron from, and rates of iron recycling within, the surface mixed layer. A pelagic iron budget (timescale of days) indicated that oceanic supply terms (lateral advection and vertical diffusion) were relatively small compared to the main sink (downward particulate export). Remote sensing and terrestrial monitoring reveal 13 dust or wildfire events in Australia, prior to and during FeCycle, one of which may have deposited iron at the study location. However, iron deposition rates cannot be derived from such observations, illustrating the difficulties in closing iron budgets without quantification of episodic atmospheric supply. Despite the threefold uncertainties reported for rates of aerosol deposition (Duce et al., 1991), published atmospheric iron supply for the New Zealand region is ˜50-fold (i.e., 7- to 150-fold) greater than the oceanic iron supply measured in our budget, and thus was comparable (i.e., a third to threefold) to our estimates of downward export of particulate iron. During FeCycle, the fluxes due to short term (hours) biological iron uptake and regeneration were indicative of rapid recycling and were tenfold greater than for new iron (i.e. estimated atmospheric and measured oceanic supply), giving an "fe" ratio (uptake of new iron/uptake of new + regenerated iron) of 0.17 (i.e., a range of 0.06 to 0.51 due to uncertainties on aerosol iron supply), and an "Fe" ratio (biogenic Fe export/uptake of new + regenerated iron) of 0.09 (i.e., 0.03 to 0.24).

  9. Phytoplankton versus macrophyte contribution to primary production and biogeochemical cycles of a coastal mesotidal system. A modelling approach

    NASA Astrophysics Data System (ADS)

    Plus, M.; Auby, I.; Maurer, D.; Trut, G.; Del Amo, Y.; Dumas, F.; Thouvenin, B.

    2015-11-01

    This study presents an assessment of the contributions of various primary producers to the global annual production and N/P cycles of a coastal system, namely the Arcachon Bay, by means of a numerical model. This 3D model fully couples hydrodynamic with ecological processes and simulates nitrogen, silicon and phosphorus cycles as well as phytoplankton, macroalgae and seagrasses. Total annual production rates for the different components were calculated for different years (2005, 2007 and 2009) during a time period of drastic reduction in seagrass beds since 2005. The total demand of nitrogen and phosphorus was also calculated and discussed with regards to the riverine inputs. Moreover, this study presents the first estimation of particulate organic carbon export to the adjacent open ocean. The calculated annual net production for the Arcachon Bay (except microphytobenthos, not included in the model) ranges between 22,850 and 35,300 tons of carbon. The main producers are seagrasses in all the years considered with a contribution ranging from 56% to 81% of global production. According to our model, the -30% reduction in seagrass bed surface between 2005 and 2007, led to an approximate 55% reduction in seagrass production, while during the same period of time, macroalgae and phytoplankton enhanced their productions by about +83% and +46% respectively. Nonetheless, the phytoplankton production remains about eightfold higher than the macroalgae production. Our results also highlight the importance of remineralisation inside the Bay, since riverine inputs only fulfill at maximum 73% nitrogen and 13% phosphorus demands during the years 2005, 2007 and 2009. Calculated advection allowed a rough estimate of the organic matter export: about 10% of the total production in the bay was exported, originating mainly from the seagrass compartment, since most of the labile organic matter was remineralised inside the bay.

  10. Contribution of phytoliths to total biogenic silica volumes in the tropical rivers of Malaysia and associated implications for the marine biogeochemical cycle

    NASA Astrophysics Data System (ADS)

    Zang, Jiaye; Liu, Sen; Liu, Yanguang; Ma, Yongxing; Ran, Xiangbin

    2016-01-01

    The contribution of phytoliths to total biogenic silica (BSi) volumes in rivers worldwide, and the associated implications for the biogeochemical cycle, require in-depth study. Based on samples from rivers in Peninsular Malaysia, this project investigated the source and characteristics of BSi found in Asian tropical rivers, as well as the process of reverse weathering taking place in these fluvial systems. Results indicated that BSi samples collected in sediments consisted of phytolith, diatom and sponge spicules. Phytoliths, predominantly of the elongate form, comprised 92.8%-98.3% of BSi in the Pahang River. Diatom BSi in this river consisted mainly of pennatae diatoms, but represented a relatively small proportion of the total BSi volume. However, diatom BSi (predominantly of the Centricae form) was more prevalent in the Pontian and Endau Rivers with shares of 68.8% and 79.3% of the total BSi volumes, respectively, than Pahang River. Carbon contents of the BSi particulates ranged from 1.85% to 10.8% with an average of 4.79%. These values are higher than those recorded in other studies to date, and indicate that BSi plays a major role in controlling permanent carbon burial. This study suggests that phytoliths from terrestrial plants are the primary constituents of BSi in the rivers of Peninsular Malaysia, and therefore represent a significant proportion of the coastal silica budget.

  11. Molecular evidence for microorganisms participating in Fe, Mn, and S biogeochemical cycling in two low-temperature hydrothermal fields at the Southwest Indian Ridge

    NASA Astrophysics Data System (ADS)

    Li, Jiwei; Peng, Xiaotong; Zhou, Huaiyang; Li, Jiangtao; Sun, Zhilei

    2013-06-01

    We examined two low-temperature hydrothermal deposits rich in Fe-Si-Mn collected from the recently discovered hydrothermal fields at the Southwest Indian Ridge using mineralogical, geochemical, and molecular biological techniques. The mineralogical and geochemical analyses indicated that the low-temperature hydrothermal fields would provide a warm and chemical species-rich habitat for chemosynthetic-based hydrothermal ecosystems. Analyses of 16S rRNA sequences showed that ζ-Proteobacteria, Pseudoalteromonas, Leptothrix, and Pseudomonas were potential Fe and Mn oxidizers in the low-temperature hydrothermal environments, but they were not present in equal abundance among the subniches. Some potential Fe and Mn reducers were also recovered; they were more commonly found in the exterior black Fe-Mn oxides. The difference between the exterior black Fe-Mn oxides and the interior Opal-A could be related to differences in in situ physicochemical conditions. We also identified microbial players that may participate in sulfur (S) geochemical cycling in these low-temperature hydrothermal environments via analyses of 16S rRNA sequences and the aprA functional gene. The results indicated that members of γ-Proteobacteria and α-Proteobacteria were involved in the S oxidation process, while members of δ-Proteobacteria, Nitrospirae, Firmicutes, and Archaea might participate in the S reduction process. Fe, Mn, and S oxidizers and reducers might actively participate in hydrothermal biogeochemical processes, which could influence the transfer of chemical species and the formation of biogenic minerals.

  12. Contribution of phytoliths to total biogenic silica volumes in the tropical rivers of Malaysia and associated implications for the marine biogeochemical cycle

    NASA Astrophysics Data System (ADS)

    Zang, Jiaye; Liu, Sen; Liu, Yanguang; Ma, Yongxing; Ran, Xiangbin

    2016-09-01

    The contribution of phytoliths to total biogenic silica (BSi) volumes in rivers worldwide, and the associated implications for the biogeochemical cycle, require in-depth study. Based on samples from rivers in Peninsular Malaysia, this project investigated the source and characteristics of BSi found in Asian tropical rivers, as well as the process of reverse weathering taking place in these fluvial systems. Results indicated that BSi samples collected in sediments consisted of phytolith, diatom and sponge spicules. Phytoliths, predominantly of the elongate form, comprised 92.8%-98.3% of BSi in the Pahang River. Diatom BSi in this river consisted mainly of pennatae diatoms, but represented a relatively small proportion of the total BSi volume. However, diatom BSi (predominantly of the Centricae form) was more prevalent in the Pontian and Endau Rivers with shares of 68.8% and 79.3% of the total BSi volumes, respectively, than Pahang River. Carbon contents of the BSi particulates ranged from 1.85% to 10.8% with an average of 4.79%. These values are higher than those recorded in other studies to date, and indicate that BSi plays a major role in controlling permanent carbon burial. This study suggests that phytoliths from terrestrial plants are the primary constituents of BSi in the rivers of Peninsular Malaysia, and therefore represent a significant proportion of the coastal silica budget.

  13. Calibration of a biome-biogeochemical cycles model for modeling the net primary production of teak forests through inverse modeling of remotely sensed data

    NASA Astrophysics Data System (ADS)

    Imvitthaya, Chomchid; Honda, Kiyoshi; Lertlum, Surat; Tangtham, Nipon

    2011-01-01

    In this paper, we present the results of a net primary production (NPP) modeling of teak (Tectona grandis Lin F.), an important species in tropical deciduous forests. The biome-biogeochemical cycles or Biome-BGC model was calibrated to estimate net NPP through the inverse modeling approach. A genetic algorithm (GA) was linked with Biome-BGC to determine the optimal ecophysiological model parameters. The Biome-BGC was calibrated by adjusting the ecophysiological model parameters to fit the simulated LAI to the satellite LAI (SPOT-Vegetation), and the best fitness confirmed the high accuracy of generated ecophysioligical parameter from GA. The modeled NPP, using optimized parameters from GA as input data, was evaluated using daily NPP derived by the MODIS satellite and the annual field data in northern Thailand. The results showed that NPP obtained using the optimized ecophysiological parameters were more accurate than those obtained using default literature parameterization. This improvement occurred mainly because the model's optimized parameters reduced the bias by reducing systematic underestimation in the model. These Biome-BGC results can be effectively applied in teak forests in tropical areas. The study proposes a more effective method of using GA to determine ecophysiological parameters at the site level and represents a first step toward the analysis of the carbon budget of teak plantations at the regional scale.

  14. Renewable Energy Production and Urban Remediation: Modeling the biogeochemical cycle at contaminated urban brownfields and the potential for renewable energy production and mitigation of greenhouse gases

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, G.

    2014-12-01

    Brownfields or urban sites that have been contaminated as a result of historic practices are present throughout the world. In the United States alone, the National Research Council has estimated that there are approximately 300,000 to 400,000 sites which have been contaminated by improper use and disposal of chemicals (NRC 1993). The land available at these sites is estimated at several million acres; however, the presence of high levels of contamination in the soil and groundwater makes it difficult to utilize these sites for traditional purposes such as agriculture. Further, the time required to remediate these contaminants to regulated levels is in the order of decades, which often results in long-term economic consequences for the areas near these sites. There has been significant interest in developing these sites as potential sources of renewable energy production in order to increase the economic viability of these sites and to provide alternative land resources for renewable energy production (EPA 2012). Solar energy, wind energy, and bioenergy from lignocellulosic biomass production have been identified as the main sources of renewable energy that can be produced at these locations. However, the environmental impacts of such a policy and the implications for greenhouse gas emissions, particularly resulting from changes in land-use impacting the biogeochemical cycle at these sites, have not been studied extensively to date. This study uses the biogeochemical process-based model DNDC to simulate carbon sequestration, nitrous oxide emissions and methane emissions from typical urban brownfield systems in the United States, when renewable energy systems are deployed. Photovoltaic solar energy and lignocellulosic biomass energy systems are evaluated here. Plants modeled include those most widely used for both bioenergy and remediation such as woody trees. Model sensitivity to soil conditions, contaminant levels and local weather data and the resulting impacts on

  15. Terrestrial carbon cycle affected by non-uniform climate warming

    NASA Astrophysics Data System (ADS)

    Xia, Jianyang; Chen, Jiquan; Piao, Shilong; Ciais, Philippe; Luo, Yiqi; Wan, Shiqiang

    2014-03-01

    Feedbacks between the terrestrial carbon cycle and climate change could affect many ecosystem functions and services, such as food production, carbon sequestration and climate regulation. The rate of climate warming varies on diurnal and seasonal timescales. A synthesis of global air temperature data reveals a greater rate of warming in winter than in summer in northern mid and high latitudes, and the inverse pattern in some tropical regions. The data also reveal a decline in the diurnal temperature range over 51% of the global land area and an increase over only 13%, because night-time temperatures in most locations have risen faster than daytime temperatures. Analyses of satellite data, model simulations and in situ observations suggest that the impact of seasonal warming varies between regions. For example, spring warming has largely stimulated ecosystem productivity at latitudes between 30° and 90° N, but suppressed productivity in other regions. Contrasting impacts of day- and night-time warming on plant carbon gain and loss are apparent in many regions. We argue that ascertaining the effects of non-uniform climate warming on terrestrial ecosystems is a key challenge in carbon cycle research.

  16. Future changes in climate, ocean circulation, ecosystems, and biogeochemical cycling simulated for a business-as-usual CO2 emission scenario until year 4000 AD

    NASA Astrophysics Data System (ADS)

    Schmittner, Andreas; Oschlies, Andreas; Matthews, H. Damon; Galbraith, Eric D.

    2008-03-01

    A new model of global climate, ocean circulation, ecosystems, and biogeochemical cycling, including a fully coupled carbon cycle, is presented and evaluated. The model is consistent with multiple observational data sets from the past 50 years as well as with the observed warming of global surface air and sea temperatures during the last 150 years. It is applied to a simulation of the coming two millennia following a business-as-usual scenario of anthropogenic CO2 emissions (SRES A2 until year 2100 and subsequent linear decrease to zero until year 2300, corresponding to a total release of 5100 GtC). Atmospheric CO2 increases to a peak of more than 2000 ppmv near year 2300 (that is an airborne fraction of 72% of the emissions) followed by a gradual decline to ˜1700 ppmv at year 4000 (airborne fraction of 56%). Forty-four percent of the additional atmospheric CO2 at year 4000 is due to positive carbon cycle-climate feedbacks. Global surface air warms by ˜10°C, sea ice melts back to 10% of its current area, and the circulation of the abyssal ocean collapses. Subsurface oxygen concentrations decrease, tripling the volume of suboxic water and quadrupling the global water column denitrification. We estimate 60 ppb increase in atmospheric N2O concentrations owing to doubling of its oceanic production, leading to a weak positive feedback and contributing about 0.24°C warming at year 4000. Global ocean primary production almost doubles by year 4000. Planktonic biomass increases at high latitudes and in the subtropics whereas it decreases at midlatitudes and in the tropics. In our model, which does not account for possible direct impacts of acidification on ocean biology, production of calcium carbonate in the surface ocean doubles, further increasing surface ocean and atmospheric pCO2. This represents a new positive feedback mechanism and leads to a strengthening of the positive interaction between climate change and the carbon cycle on a multicentennial to millennial

  17. Annual cycles of deep-ocean biogeochemical export fluxes in subtropical and subantarctic waters, southwest Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Nodder, Scott D.; Chiswell, Stephen M.; Northcote, Lisa C.

    2016-04-01

    The annual cycles of particle fluxes derived from moored sediment trap data collected during 2000-2012 in subtropical (STW) and subantarctic waters (SAW) east of New Zealand are presented. These observations are the most comprehensive export flux time series from temperate Southern Hemisphere latitudes to date. With high levels of variability, fluxes in SAW were markedly lower than in STW, reflecting the picophytoplankton-dominated communities in the iron-limited, high nutrient-low chlorophyll SAW. Austral spring chlorophyll blooms in surface STW were near synchronous with elevated fluxes of bio-siliceous, carbonate, and organic carbon-rich materials to the deep ocean, probably facilitated by diatom and/or coccolithophorid sedimentation. Lithogenic fluxes were also high in STW, compared to SAW, reflecting proximity to the New Zealand landmass. In contrast, the highest biogenic fluxes in SAW occurred in spring when surface chlorophyll concentrations were low, while highest annual chlorophyll concentrations were in summer with no associated flux increase. We hypothesize that the high spring export in SAW results from subsurface chlorophyll accumulation that is not evident from remote-sensing satellites. This material was also rich in biogenic silica, perhaps related to the preferential export of diatoms and other silica-producing organisms, such as silicoflagellates and radiolarians. Organic carbon fluxes in STW are similar to that of other mesotrophic to oligotrophic waters (˜6-7 mg C m-2 d-1), whereas export from SAW is below the global average (˜3 mg C m-2 d-1). Regional differences in flux across the SW Pacific and Tasman region reflect variations in physical processes and ecosystem structure and function.

  18. Dissolved Silver in Marine Waters: Reviewing Three Decades of Advances in Analytical Techniques and Understanding its Biogeochemical Cycling

    NASA Astrophysics Data System (ADS)

    Ndungu, K.; Flegal, A. R., Jr.

    2015-12-01

    Although billions of dollars have been spent over the past half-century to reduce contamination of U.S. waters, quantifying parts-per-billion reductions in surface water concentration since has been relatively unsuccessful. The reasons for the failure in identifying the benefits of these remediative efforts include: (i) historic (pre-1980) problems in accurately sampling and analyzing trace element concentrations at parts-per-billion level, so that temporal reductions in trace metal contamination reflected improved sampling and analytical accuracy rather than real decreases in those concentrations; (ii) limited seasonal and long term research. Silver in its ionic form is more toxic to aquatic organisms than any other metal except Hg. Because Ag is not common naturally in the environment, its elevated presence in water, sediment or biological tissues is usually indicative of anthropogenic influences. However, there is very little published data on Ag levels in both water and sediment. The published studies include Ag levels in a few U.S. estuarine waters, including detailed and time series studies for the San Francisco Estuary system by the WIGS lab at UC Santa Cruz. In the open Ocean, Ag measurements are limited to a few studies in the North and South Pacific, The North and South Atlantic. However, as Gallon and Flegal recently noted, there is no available data on Ag concentrations from the Indian Ocean! Most of the dissolved Ag data from the Atlantic was made in WIGS lab at UC Santa Cruz Analytical determination of Ag in seawater has come a long way since Murozumi reported the first dissolved Ag measurements from the N. Pacific in 1981 using isotope dilution MS after solvent extraction. In this presentation I will review analytical developments for Ag determination in the last three decades. I will also highlight the missing data gaps and present new tentative data on dissolved Ag concentration and cycling in polar regions including the Antarctic (Amundsen Sea

  19. Impact of vegetation and ecosystems on chlorine(-36) cycling and its modeling: from simplified approaches towards more complex biogeochemical tools

    NASA Astrophysics Data System (ADS)

    Thiry, Yves; Redon, Paul-Olivier; Gustafsson, Malin; Marang, Laura; Bastviken, David

    2013-04-01

    Chlorine is very soluble at a global scale with chloride (Cl-), the dominating form. Because of its high mobility, chlorine is usually perceived as a good conservative tracer in hydrological studies and by analogy as little reactive in biosphere. Since 36Cl can be considered to have the same behaviour than stable Cl, a good knowledge of chlorine distribution between compartments of terrestrial ecosystems is sufficient to calibrate a specific activity model which supposes rapid dilution of 36Cl within the large pool of stable Cl and isotopic equilibrium between compartments. By assuming 36Cl redistribution similar to that of stable Cl at steady-state, specific activity models are simplified interesting tools for regulatory purposes in environmental safety assessment, especially in case of potential long term chronic contamination of agricultural food chain (IAEA, 2010). In many other more complex scenarios (accidental acute release, intermediate time frame, and contrasted natural ecosystems), new information and tools are necessary for improving (radio-)ecological realism, which entails a non-conservative behavior of chlorine. Indeed observed dynamics of chlorine in terrestrial ecosystems is far from a simple equilibrium notably because of natural processes of organic matter (SOM) chlorination mainly occurring in surface soils (Öberg, 1998) and mediated by microbial activities on a large extent (Bastviken et al. 2007). Our recent studies have strengthened the view that an organic cycle for chlorine should now be recognized, in addition to its inorganic cycle. Major results showed that: organochlorine (Clorg) formation occurs in all type of soils and ecosystems (culture, pasture, forest), leading to an average fraction of the total Cl pool in soil of about 80 % (Redon et al., 2012), chlorination in more organic soils over time leads to a larger Clorg pool and in turn to a possible high internal supply of inorganic chlorine (Clin) upon dechlorination. (Gustafsson et

  20. Resource quality affects carbon cycling in deep-sea sediments.

    PubMed

    Mayor, Daniel J; Thornton, Barry; Hay, Steve; Zuur, Alain F; Nicol, Graeme W; McWilliam, Jenna M; Witte, Ursula F M

    2012-09-01

    Deep-sea sediments cover ~70% of Earth's surface and represent the largest interface between the biological and geological cycles of carbon. Diatoms and zooplankton faecal pellets naturally transport organic material from the upper ocean down to the deep seabed, but how these qualitatively different substrates affect the fate of carbon in this permanently cold environment remains unknown. We added equal quantities of (13)C-labelled diatoms and faecal pellets to a cold water (-0.7 °C) sediment community retrieved from 1080 m in the Faroe-Shetland Channel, Northeast Atlantic, and quantified carbon mineralization and uptake by the resident bacteria and macrofauna over a 6-day period. High-quality, diatom-derived carbon was mineralized >300% faster than that from low-quality faecal pellets, demonstrating that qualitative differences in organic matter drive major changes in the residence time of carbon at the deep seabed. Benthic bacteria dominated biological carbon processing in our experiments, yet showed no evidence of resource quality-limited growth; they displayed lower growth efficiencies when respiring diatoms. These effects were consistent in contrasting months. We contend that respiration and growth in the resident sediment microbial communities were substrate and temperature limited, respectively. Our study has important implications for how future changes in the biochemical makeup of exported organic matter will affect the balance between mineralization and sequestration of organic carbon in the largest ecosystem on Earth. PMID:22378534

  1. ASSESSMENT OF INTRINSIC BIOREMEDIATION OF A COAL-TAR AFFECTED AQUIFER USING TWO-DIMENSIONAL REACTIVE TRANSPORT AND BIOGEOCHEMICAL MASS BALANCE APPROACHES

    EPA Science Inventory

    Expedited site characterization and groundwater monitoring using direct-push technology and conventional monitoring wells were conducted at a former manufactured gas plant site. Biogeochemical data and heterotrophic plate counts support the presence of microbially mediated remedi...

  2. Simulation of annual biogeochemical cycles of nutrient balance, phytoplankton bloom(s), and DO in Puget Sound using an unstructured grid model

    SciTech Connect

    Khangaonkar, Tarang; Sackmann, Brandon; Long, Wen; Mohamedali, Teizeen; Roberts, Mindy

    2012-08-14

    Nutrient pollution from rivers, nonpoint source runoff, and nearly 100 wastewater discharges is a potential threat to the ecological health of Puget Sound with evidence of hypoxia in some basins. However, the relative contributions of loads entering Puget Sound from natural and anthropogenic sources, and the effects of exchange flow from the Pacific Ocean are not well understood. Development of a quantitative model of Puget Sound is thus presented to help improve our understanding of the annual biogeochemical cycles in this system using the unstructured grid Finite-Volume Coastal Ocean Model framework and the Integrated Compartment Model (CE-QUAL-ICM) water quality kinetics. Results based on 2006 data show that phytoplankton growth and die-off, succession between two species of algae, nutrient dynamics, and dissolved oxygen in Puget Sound are strongly tied to seasonal variation of temperature, solar radiation, and the annual exchange and flushing induced by upwelled Pacific Ocean waters. Concentrations in the mixed outflow surface layer occupying approximately 5–20 m of the upper water column show strong effects of eutrophication from natural and anthropogenic sources, spring and summer algae blooms, accompanied by depleted nutrients but high dissolved oxygen levels. The bottom layer reflects dissolved oxygen and nutrient concentrations of upwelled Pacific Ocean water modulated by mixing with biologically active surface outflow in the Strait of Juan de Fuca prior to entering Puget Sound over the Admiralty Inlet. The effect of reflux mixing at the Admiralty Inlet sill resulting in lower nutrient and higher dissolved oxygen levels in bottom waters of Puget Sound than the incoming upwelled Pacific Ocean water is reproduced. Finally, by late winter, with the reduction in algal activity, water column constituents of interest, were renewed and the system appeared to reset with cooler temperature, higher nutrient, and higher dissolved oxygen waters from the Pacific

  3. Simulation of annual biogeochemical cycles of nutrient balance, phytoplankton bloom(s), and DO in Puget Sound using an unstructured grid model

    NASA Astrophysics Data System (ADS)

    Khangaonkar, Tarang; Sackmann, Brandon; Long, Wen; Mohamedali, Teizeen; Roberts, Mindy

    2012-09-01

    Nutrient pollution from rivers, nonpoint source runoff, and nearly 100 wastewater discharges is a potential threat to the ecological health of Puget Sound with evidence of hypoxia in some basins. However, the relative contributions of loads entering Puget Sound from natural and anthropogenic sources, and the effects of exchange flow from the Pacific Ocean are not well understood. Development of a quantitative model of Puget Sound is thus presented to help improve our understanding of the annual biogeochemical cycles in this system using the unstructured grid Finite-Volume Coastal Ocean Model framework and the Integrated Compartment Model (CE-QUAL-ICM) water quality kinetics. Results based on 2006 data show that phytoplankton growth and die-off, succession between two species of algae, nutrient dynamics, and dissolved oxygen in Puget Sound are strongly tied to seasonal variation of temperature, solar radiation, and the annual exchange and flushing induced by upwelled Pacific Ocean waters. Concentrations in the mixed outflow surface layer occupying approximately 5-20 m of the upper water column show strong effects of eutrophication from natural and anthropogenic sources, spring and summer algae blooms, accompanied by depleted nutrients but high dissolved oxygen levels. The bottom layer reflects dissolved oxygen and nutrient concentrations of upwelled Pacific Ocean water modulated by mixing with biologically active surface outflow in the Strait of Juan de Fuca prior to entering Puget Sound over the Admiralty Inlet. The effect of reflux mixing at the Admiralty Inlet sill resulting in lower nutrient and higher dissolved oxygen levels in bottom waters of Puget Sound than the incoming upwelled Pacific Ocean water is reproduced. By late winter, with the reduction in algal activity, water column constituents of interest, were renewed and the system appeared to reset with cooler temperature, higher nutrient, and higher dissolved oxygen waters from the Pacific Ocean.

  4. Peaks of solar cycles affect the gender ratio.

    PubMed

    Davis, George E; Lowell, Walter E

    2008-12-01

    In this study, we report that the gender ratio (GR) at death [where GR=(N(males)/N(males)+N(females))] of those born (and likely conceived) in solar cycle peaks (about a 3-year period occurring on average every approximately 11 years), is inversely related to mean male age at death; e.g., the higher the GR(at death) the lower the mean lifespan, while the GR(at death) of those born in non-peak years has no relation to mean male lifespan. Although changes in the GR are small and may be of little clinical significance, the GR is a sensitive indicator of environmental effects, and therefore is pertinent to epigenetics. This paper supports the hypothesis that solar radiation, probably in the ultraviolet spectrum, by some manner interacts with chromosomal DNA (genes) and produces the genetic variety that not only fosters adaptation, but also produces the diseases that reduce lifespan. This paper also proposes that sunlight is more effective in modifying genomes at the time of conception than later in gestation or infancy. Referring to the work of others, this study also reveals that geographic latitude also affects the GR, suggesting that the variation in light is probably as important as the intensity of light in modifying genomes. This study finds that men sustain more genetic variation, producing 28% more disease than women, as well as a 2% decrease in GR from birth to death, and a shorter life (in Maine) by 7 years. PMID:18755551

  5. Natural and anthropogenic impacts on biogeochemical cycle in Yangtze River basin: Source, transformation and fate of dissolved organic matter (DOM) characterized by 3-D fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Gan, Shuchai; Wu, Ying; Bao, Hongyan; Zhang, Jing

    2013-04-01

    Inland waters play an important role in the global carbon cycle as reactors for DOM cycling, transformation and transportation. With large amounts of terrestrial DOM, the Yangtze River is vital for coastal environment and ecosystem. In the context of climate change, it's critical to evaluate both hydrodynamic conditions and increasing human activities' impacts on biogeochemical cycle of DOM in Yangtze River across different climatic and hydrologic regions which are poorly understood. What's more, the hydrologic condition changes caused by the Three Gorges Dam (TGD, world's largest power station in terms of installed capacity) have recently proven to be a partition factor for fluvial particle. However, it's still an enigma for dissolved matter cycle. To address those issues, this study applies EEMs combined with bulk characteristics, chlorophyll and absorption spectrum in an attempt to assess characteristics and dynamics of DOM in Yangtze River. It's a novel optical approach that could 'see' molecular structure of DOM without the limits of time-consuming and laborious molecular measurements. Combined with parallel factor analysis, 5 individual fluorescent components have been identified: 3 humic-like (H1, H2, H3) and 2 protein-like components (P1, P2). With typical bioavailability and photo-reactivity, these components suggest different sources and dynamics. On the whole, both DOC and the sum of all 5 components (? Fluo) increased remarkably from the upper reach especially to the Three Gorge Dam and thereafter remained constant (R2between DOC and - Fluo: 0.92). The protein-like components (- P) accounted for 1/4 of - Fluo with apparently weak correlations with DOC and chlorophyll, which implied that the DOM is not dominated by autochthonous production, especially for the upper reach with high concentration of total suspended matter. As for Humic-like component, increasing H1 and DOC in the TGD reservoir area implied impacts from human activities there with intercept

  6. Stable Strontium Isotopes (δ88/86Sr) As a Tracer of Sr Sources and Biogeochemical Cycling in Two Catchments Draining Fiordland, New Zealand

    NASA Astrophysics Data System (ADS)

    Andrews, G.; Jacobson, A. D.; Lehn, G. O.

    2014-12-01

    To understand how Sr isotopes behave during chemical weathering and biogeochemical cycling, we analyzed the stable Sr isotope composition (δ88/86Sr) of rivers, rocks, sediments, plants, and soils from the Cleddau and Hollyford catchments in Fiordland, New Zealand. We leached rocks, sediments, and soils to isolate relatively soluble Sr sources. δ88/86Sr values were measured using an 87Sr-84Sr double-spike MC-TIMS method, which was optimized according to the Monte Carlo error model described in Lehn et al. (2013). The long-term, external reproducibility of the method is ±0.020‰ (2σSD) based on repeated measurements of NBS-987 [δ88/86Sr = 0.000 ± 0.004‰ (2σSEM), n=77] and IAPSO seawater [δ88/86Sr = 0.396 ± 0.005‰ (2σSEM), n=54]. Although the study site receives abundant rainfall (6700mm/yr), atmospheric inputs of Sr are negligible. We find that δ88/86Sr values can distinguish between silicate- versus carbonate- derived riverine Sr sources when traditional tracers, such as radiogenic Sr isotope (87Sr/86Sr) and molar Ca/Sr ratios, are equivocal. Moreover, rivers draining gabbro bedrock in the Cleddau and Upper Hollyford catchments have higher δ88/86Sr values (0.368‰) as compared to bulk silicate rock (0.162 - 0.284‰) and sediment (0.286‰). In the Lower Hollyford catchment, tributary rivers draining volcanic and sedimentary rocks also have higher δ88/86Sr values (0.328‰) as compared to bulk silicate rock (0.177‰) and sediment (0.260‰). We examine several hypotheses to explain the elevated riverine δ88/86Sr values, including end-member mixing, fractionation during chemical weathering, and plant uptake. We attribute the riverine δ88/86Sr values to mixing with the soil pore water pool, which is isotopically heavy due to preferential uptake of 86Sr by plants.

  7. Biogeochemistry of sulfur in the Vienna Woods: Study of sulfur stable isotope ratios by MC-ICP-MS as indicator of biogeochemical S cycling

    NASA Astrophysics Data System (ADS)

    Hanousek, Ondrej; Berger, Torsten W.; Prohaska, Thomas

    2014-05-01

    Sulfur entering forest ecosystems originates mainly from combustion of fossil fuels. This source of sulfur has been strongly (by more than 95 %) reduced in last decades and recently, higher sulfur output (in soil solution or stream water) than sulfur input (in rain water) in an ecosystem was registered in many monitored forest ecosystems. This unbalance may be caused by weathering of sulfur-bearing rocks, desorption of sulfur adsorbed in soil in the past or (re)mineralization of organic sulfur compounds. This 'negative' balance leads to mobilization of base cations along with SO42- and as such to an acidification of soils. As hypothesis, δ34S/32S depletion in stream water will be observed if a considerable proportion of atmospherically deposited sulfate is cycled through the organic S pool. Rain water and soil solutions samples were collected for this study at 3 sites (beech stands) in the Vienna Woods, Austria twice a month from May 2010 to April 2012. Due to the expected sulfate concentration gradient with respect to the distance from a tree, sampling was carried out at 5 intervals from a stem. The sulfur concentration in the samples was determined by ion chromatography. Sulfur isotope ratios (δ34S/32SV CDT) were analyzed by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) in edge-resolution mode. The method was validated using IAEA-S-1 and IAEA-S-2 isotopic certified reference materials. The combined standard uncertainty of the measurement (uc = 0.10 %, k = 1) proves the suitability of the developed method. The concentration of sulfur in rain water showed expected behavior, with a seasonal maximum in winter months, in contrast to the corresponding δ34S/32SV CDT isotope ratios, where no or low seasonal trends were observed. The sulfur isotope ratios in soil solution samples show a dependence on the distance from a tree stem and the sampling depth with lower δ34S/32SV CDT ratios as compared to the precipitation. The measured isotopic

  8. Comparative Biogeochemical Cycles of Bioenergy Crops Reveal Nitrogen-Fixation and Low GHG Emissions in a Miscanthus x giganteus Agro-ecosystem

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We evaluated the relative greenhouse gas mitigation potential of plant species considered as biofuel feedstock crops by simulating the biogeochemical processes associated with Miscanthus x giganteus, Panicum virgatum, Zea mays, and a mixed prairie community. DayCent model simulations for Miscanthus ...

  9. Does gender or the menstrual cycle affect colonic transit?

    PubMed

    Hinds, J P; Stoney, B; Wald, A

    1989-02-01

    Controversy exists as to whether slowing of colonic transit occurs in the high progesterone luteal phase of the menstrual cycle. To clarify this issue, colonic transit studies using radiopaque markers were performed on 10 women in the follicular phase, 10 women in the luteal phase of the menstrual cycle, and five women on oral contraceptives, and the results were compared with transit times in 11 male controls. No significant differences in colonic transit were found between either phase of the menstrual cycle. Colonic transit in women was slower than in men, but this was not statistically significant. In the clinical setting, therefore, colonic transit studies can be performed throughout the menstrual cycle or when taking oral contraceptives. In addition, a single standard for normal values can be used for both men and women. PMID:2916519

  10. Post-transcriptional RNA Regulons Affecting Cell Cycle and Proliferation

    PubMed Central

    Blackinton, Jeff G.

    2014-01-01

    The cellular growth cycle is initiated and maintained by punctual, yet agile, regulatory events involving modifications of cell cycle proteins as well as coordinated gene expression to support cyclic checkpoint decisions. Recent evidence indicates that post-transcriptional partitioning of messenger RNA subsets by RNA-binding proteins help physically localize, temporally coordinate, and efficiently translate cell cycle proteins. This dynamic organization of mRNAs encoding cell cycle components contributes to the overall economy of the cell cycle consistent with the post-transcriptional RNA regulon model of gene expression. This review examines several recent studies demonstrating the coordination of mRNA subsets encoding cell cycle proteins during nuclear export and subsequent coupling to protein synthesis, and discusses evidence for mRNA coordination of p53 targets and the DNA damage response pathway. We consider how these observations may connect to upstream and downstream post-transcriptional coordination and coupling of splicing, export, localization, and translation. Published examples from yeast, nematode, insect, and mammalian systems are discussed, and we consider genetic evidence supporting the conclusion that dysregulation of RNA regulons may promote pathogenic states of growth such as carcinogenesis. PMID:24882724

  11. Global Biology Research Program: Biogeochemical Processes in Wetlands

    NASA Technical Reports Server (NTRS)

    Bartlett, D. S. (Editor)

    1984-01-01

    The results of a workshop examining potential NASA contributions to research on wetland processes as they relate to global biogeochemical cycles are summarized. A wetlands data base utilizing remotely sensed inventories, studies of wetland/atmosphere exchange processes, and the extrapolation of local measurements to global biogeochemical cycling processes were identified as possible areas for NASA support.

  12. Oceanographic and biogeochemical insights from diatom genomes.

    PubMed

    Bowler, Chris; Vardi, Assaf; Allen, Andrew E

    2010-01-01

    Diatoms are the most successful group of eukaryotic phytoplankton in the modern ocean and have risen to dominance relatively quickly over the last 100 million years. Recently completed whole genome sequences from two species of diatom, Thalassiosira pseudonana and Phaeodactylum tricornutum, have revealed a wealth of information about the evolutionary origins and metabolic adaptations that have led to their ecological success. A major finding is that they have incorporated genes both from their endosymbiotic ancestors and by horizontal gene transfer from marine bacteria. This unique melting pot of genes encodes novel capacities for metabolic management, for example, allowing the integration of a urea cycle into a photosynthetic cell. In this review we show how genome-enabled approaches are being leveraged to explore major phenomena of oceanographic and biogeochemical relevance, such as nutrient assimilation and life histories in diatoms. We also discuss how diatoms may be affected by climate change-induced alterations in ocean processes. PMID:21141668

  13. Cretaceous-Palaeogene experiments in Biogeochemical Resilience

    NASA Astrophysics Data System (ADS)

    Penman, D. E.; Henehan, M. J.; Hull, P. M.; Planavsky, N.; Schmidt, D. N.; Rae, J. W. B.; Thomas, E.; Huber, B. T.

    2015-12-01

    Human activity is altering biogeochemical cycles in the ocean. While ultimately anthropogenic forcings may be brought under control, it is still unclear whether tipping points may exist beyond which human-induced changes to biogeochemical cycles become irreversible. We use the Late Cretaceous and the Cretaceous-Palaeogene (K-Pg) boundary interval as an informative case study. Over this interval, two carbon cycle perturbations (gradual flood basalt volcanism and abrupt bolide impact) occurred within a short time window, allowing us to investigate the resilience of biogeochemical cycles to different pressures applied to the same initial boundary conditions on very different time scales. We demonstrate that relatively gradual emission of CO2 from the Deccan large igneous province was efficiently mitigated within the limits of existing biogeochemical processes. However, the rapid extinction of pelagic calcifying organisms at the K-Pg boundary due to the Chicxulub bolide impact had more profound effects, and caused lasting (> 1 million years) changes to biogeochemical cycles. By combining sedimentological observations with boron isotope-based pH reconstructions over these events, we document two potentially useful partial analogues for best and worst case scenarios for anthropogenic global change. We suggest that if current ocean acidification results in the mass extinction of marine pelagic calcifiers, we may cause profound changes to the Earth system that will persist for 100,000s to millions of years.

  14. Using Coupled Models to Study the Effects of River Discharge on Biogeochemical Cycling and Hypoxia in the Northern Gulf of Mexico

    NASA Technical Reports Server (NTRS)

    Penta, Bradley; Ko, D.; Gould, Richard W.; Arnone, Robert A.; Greene, R.; Lehrter, J.; Hagy, James; Schaeffer, B.; Murrell, M.; Kurtz, J.; Herchenroder, B.; Green, R.; Eldridge, P.

    2009-01-01

    We describe emerging capabilities to understand physical processes and biogeoehemical cycles in coastal waters through the use of satellites, numerical models, and ship observations. Emerging capabilities provide significantly improved ability to model ecological systems and the impact of environmental management actions on them. The complex interaction of physical and biogeoehemical processes responsible for hypoxic events requires an integrated approach to research, monitoring, and modeling in order to fully define the processes leading to hypoxia. Our efforts characterizes the carbon cycle associated with river plumes and the export of organic matter and nutrients form coastal Louisiana wetlands and embayments in a spatially and temporally intensive manner previously not possible. Riverine nutrients clearly affect ecosystems in the northern Gulf of Mexico as evidenced in the occurrence of regional hypoxia events. Less known and largely unqualified is the export of organic matter and nutrients from the large areas of disappearing coastal wetlands and large embayments adjacent to the Louisiana Continental Shelf. This project provides new methods to track the river plume along the shelf and to estimate the rate of export of suspended inorganic and organic paniculate matter and dissolved organic matter form coastal habitats of south Louisiana.

  15. [Effects of global climate change on the ecological characteristics and biogeochemical significance of marine viruses--A review].

    PubMed

    Yang, Yunlan; Cai, Lanlan; Zhang, Rui

    2015-09-01

    As the most abundance biological agents in the oceans, viruses can influence the physiological and ecological characteristics of host cells through viral infections and lysis, and affect the nutrient and energy cycles of the marine food chain. Thus, they are the major players in the ocean biogeochemical processes. The problems caused by global climate changes, such as sea-surface warming, acidification, nutrients availability, and deoxygenation, have the potential effects on marine viruses and subsequently their ecological and biogeochemical function in the ocean. Here, we reviewed the potential impacts of global climate change on the ecological characteristics (e. g. abundance, distribution, life cycle and the host-virus interactions) and biogeochemical significance (e. g. carbon cycling) of marine viruses. We proposed that marine viruses should not be ignored in the global climate change study. PMID:26762022

  16. Allyl isothiocyanate affects the cell cycle of Arabidopsis thaliana

    PubMed Central

    Åsberg, Signe E.; Bones, Atle M.; Øverby, Anders

    2015-01-01

    Isothiocyanates (ITCs) are degradation products of glucosinolates present in members of the Brassicaceae family acting as herbivore repellents and antimicrobial compounds. Recent results indicate that allyl ITC (AITC) has a role in defense responses such as glutathione depletion, ROS generation and stomatal closure. In this study we show that exposure to non-lethal concentrations of AITC causes a shift in the cell cycle distribution of Arabidopsis thaliana leading to accumulation of cells in S-phases and a reduced number of cells in non-replicating phases. Furthermore, transcriptional analysis revealed an AITC-induced up-regulation of the gene encoding cyclin-dependent kinase A while several genes encoding mitotic proteins were down-regulated, suggesting an inhibition of mitotic processes. Interestingly, visualization of DNA synthesis indicated that exposure to AITC reduced the rate of DNA replication. Taken together, these results indicate that non-lethal concentrations of AITC induce cells of A. thaliana to enter the cell cycle and accumulate in S-phases, presumably as a part of a defensive response. Thus, this study suggests that AITC has several roles in plant defense and add evidence to the growing data supporting a multifunctional role of glucosinolates and their degradation products in plants. PMID:26042144

  17. Linking spatially distributed biogeochemical data with a two-host life-cycle pathogen:A model of whirling disease dynamics in salmonid fishes in the Intermountain West

    NASA Astrophysics Data System (ADS)

    Fytilis, N.; Lamb, R.; Stevens, L.; Morrissey, L. A.; Kerans, B.; Rizzo, D. M.

    2010-12-01

    Fish diseases are often caused by waterborne parasites, making them ideal systems for modeling the non-linear relationships between biogeochemical features and disease dynamics. Myxobolus cerebralis, the causative agent of whirling disease, has been a major contributor to the loss of wild rainbow trout populations in numerous streams within the Intermountain West (Colorado, Idaho, Montana, Utah, Wyoming). The parasite alternates between an invertebrate and vertebrate host, being transmitted between the sediment feeding worm T.Tubifex and salmonid fishes. A greater understanding of the linkage between biological stream integrity, geomorphic features, water quality parameters and whirling disease risk is needed to improve current management techniques. Biodiversity and abundance of the worm communities are influenced by biogeochemical features and linked to disease severity in fish. We collected and identified ~700 worms from eight sites using molecular genetic probes and a taxonomic key. Additionally, ~1700 worms were identified using only a taxonomic key. Our work examines the links between worm community structure and biogeochemical features. We use a modified Self-Organizing-Map (SOM), which is a non-parametric clustering method based on an artificial neural network (ANN). Clustering methods are particularly attractive for exploratory data analyses because they do not require either the target number of groupings or the data structure be specified at the outset. ANN clustering methods have been shown to be more robust and to account for more data variability than traditional methods when applied to clustering geo-hydrochemical and microbiological datasets. The SOM highlights spatial variation of worm community structure between sites; and is used in tandem with expert knowledge (Lamb and Kerans) of local worm communities and a Madison River, MT physiochemical dataset (GIS-derived layers, water quality parameters). We iteratively clustered the physiochemical data

  18. Evaluation of Physicochemical Deterioration and Lipid Oxidation of Beef Muscle Affected by Freeze-thaw Cycles.

    PubMed

    Rahman, M H; Hossain, M M; Rahman, S M E; Amin, M R; Oh, Deog-Hwan

    2015-01-01

    This study was performed to explore the deterioration of physicochemical quality of beef hind limb during frozen storage at -20℃, affected by repeated freeze-thaw cycles. The effects of three successive freeze-thaw cycles on beef hind limb were investigated comparing with unfrozen beef muscle for 80 d by keeping at -20±1℃. The freeze-thaw cycles were subjected to three thawing methods and carried out to select the best one on the basis of deterioration of physicochemical properties of beef. As the number of repeated freeze-thaw cycles increased, drip loss decreased and water holding capacity (WHC) increased (p<0.05) till two cycles and then decreased. Cooking loss increased in cycle one and three but decreased in cycle two. Moreover, drip loss, WHC and cooking loss affected (p<0.05) by thawing methods within the cycles. However, pH value decreased (p<0.05), but peroxide value (p<0.05), free fatty acids value (p<0.05) and TBARS value increased (p<0.05) significantly as the number of repeated freeze-thaw cycles increased. Moreover, significant (p<0.05) interactive effects were found among the thawing methods and repeated cycles. As a result, freeze-thaw cycles affected the physicochemical quality of beef muscle, causing the degradation of its quality. PMID:26877637

  19. Evaluation of Physicochemical Deterioration and Lipid Oxidation of Beef Muscle Affected by Freeze-thaw Cycles

    PubMed Central

    Rahman, M. H.; Hossain, M. M.; Rahman, S. M. E.; Amin, M. R.; Oh, Deog-Hwan

    2015-01-01

    This study was performed to explore the deterioration of physicochemical quality of beef hind limb during frozen storage at −20℃, affected by repeated freeze-thaw cycles. The effects of three successive freeze-thaw cycles on beef hind limb were investigated comparing with unfrozen beef muscle for 80 d by keeping at −20±1℃. The freeze-thaw cycles were subjected to three thawing methods and carried out to select the best one on the basis of deterioration of physicochemical properties of beef. As the number of repeated freeze-thaw cycles increased, drip loss decreased and water holding capacity (WHC) increased (p<0.05) till two cycles and then decreased. Cooking loss increased in cycle one and three but decreased in cycle two. Moreover, drip loss, WHC and cooking loss affected (p<0.05) by thawing methods within the cycles. However, pH value decreased (p<0.05), but peroxide value (p<0.05), free fatty acids value (p<0.05) and TBARS value increased (p<0.05) significantly as the number of repeated freeze-thaw cycles increased. Moreover, significant (p<0.05) interactive effects were found among the thawing methods and repeated cycles. As a result, freeze-thaw cycles affected the physicochemical quality of beef muscle, causing the degradation of its quality. PMID:26877637

  20. Menstrual cycle phase affects discrimination of infant cuteness.

    PubMed

    Lobmaier, Janek S; Probst, Fabian; Perrett, David I; Heinrichs, Markus

    2015-04-01

    Recent studies have shown that women are more sensitive than men to subtle cuteness differences in infant faces. It has been suggested that raised levels in estradiol and progesterone may be responsible for this advantage. We compared young women's sensitivity to computer-manipulated baby faces varying in cuteness. Thirty-six women were tested once during ovulation and once during the luteal phase of their menstrual cycle. In a two alternative forced-choice experiment, participants chose the baby which they thought was cuter (Task 1), younger (Task 2), or the baby that they would prefer to babysit (Task 3). Saliva samples to assess levels of estradiol, progesterone and testosterone were collected at each test session. During ovulation, women were more likely to choose the cuter baby than during the luteal phase, in all three tasks. These results suggest that cuteness discrimination may be driven by cyclic hormonal shifts. However none of the measured hormones were related to increased cuteness sensitivity. We speculate that other hormones than the ones measured here might be responsible for the increased sensitivity to subtle cuteness differences during ovulation. PMID:25683277

  1. Assessment of intrinsic bioremediation of a coal-tar-affected aquifer using two-dimensional reactive transport and biogeochemical mass balance approaches

    SciTech Connect

    Rogers, S.W.; Ong, S.K.; Stenback, G.A.; Golchin, J.; Kjartanson, B.H.

    2007-01-15

    Expedited site characterization and groundwater monitoring using direct-push technology and conventional monitoring wells were conducted at a former manufactured gas plant site. Biogeochemical data and heterotrophic plate counts support the presence of microbially mediated remediation. By superimposing solutions of a two-dimensional reactive transport analytical model, first-order degradation rate coefficients (day{sup -1}) of various compounds for the dissolved-phase plume were estimated (i.e., benzene (0.0084), naphthalene (0.0058), and acenaphthene (0.0011)). The total mass transformed by aerobic respiration, nitrate reduction, and sulfate reduction around the free-phase coal-tar dense-nonaqueous-phase-liquid region and in the plume was estimated to be approximately 4.5 kg/y using a biogeochemical mass-balance approach. The total mass transformed using the degradation rate coefficients was estimated to be approximately 3.6 kg/y. Results showed that a simple two-dimensional analytical model and a biochemical mass balance with geochemical data from expedited site characterization can be useful for rapid estimation of mass-transformation rates.

  2. Breaking the cycle: extending the persistent pain cycle diagram using an affective pictorial metaphor.

    PubMed

    Stones, Catherine; Cole, Frances

    2014-01-01

    The persistent pain cycle diagram is a common feature of pain management literature. but how is it designed and is it fulfilling its potential in terms of providing information to motivate behavioral change? This article examines on-line persistent pain diagrams and critically discusses their purpose and design approach. By using broad information design theories by Karabeg and particular approaches to dialogic visual communications in business, this article argues the need for motivational as well as cognitive diagrams. It also outlines the design of a new persistent pain cycle that is currently being used with chronic pain patients in NHS Bradford, UK. This new cycle adopts and then visually extends an established verbal metaphor within acceptance and commitment therapy (ACT) in an attempt to increase the motivational aspects of the vicious circle diagram format. PMID:23356651

  3. Development of a robust marine ecosystem model to predict the role of iron in biogeochemical cycles: A comparison of results for iron-replete and iron-limited areas, and the SOIREE iron-enrichment experiment

    NASA Astrophysics Data System (ADS)

    Fasham, M. J. R.; Flynn, K. J.; Pondaven, P.; Anderson, T. R.; Boyd, P. W.

    2006-02-01

    A new mixed layer multi-nutrient ecosystem model, incorporating diatoms, non-diatoms and zooplankton, is described that models the role of iron in marine biogeochemical cycles. The internal cell biochemistry of the phytoplankton is modelled using the mechanistic model of Flynn [2001. A mechanistic model for describing dynamic multi-nutrient, light, temperature interactions in phytoplankton. Journal of Plankton Research 23, 977-997] in which the internal cell concentrations of chlorophyll, nitrogen, silica, and iron are all dynamic variables that respond to external nutrient concentrations and light levels. Iron stress in phytoplankton feeds back into chlorophyll synthesis and changes in photosynthetic unit (PSU) size, thereby reducing their growth rate. Because diatom silicon metabolism is inextricably linked with cell division, diatom population density (cell m -3) is modelled as well as C biomass. An optimisation technique was used to fit the model to three time-series datasets at Biotrans (47°N, 20°W) and Kerfix (50°40'S, 68°25'E) and the observations for the Southern Ocean Iron-Release Experiment (SOIREE) iron-enrichment experiment (61°S, 140°E). The model gives realistic simulations of the annual cycles of nutrients, phytoplankton, and primary production at Biotrans and Kerfix and can also accurately simulate an iron fertilisation experiment. Specifically, the model predicts the high values of diatom Si:N and Si:C ratios observed in areas where iron is a limiting factor on algal growth. In addition, the model results at Kerfix confirm previous suggestions that underwater light levels have a more limiting effect on phytoplankton growth than iron supply. The model is also used to calculate C budgets and C and Si export from the mixed layer. The implications of these results for developing biogeochemical models incorporating the role of iron are discussed.

  4. Effect of sulfidogenesis cycling on the biogeochemical process in arsenic-enriched aquifers in the Lanyang Plain of Taiwan: Evidence from a sulfur isotope study

    NASA Astrophysics Data System (ADS)

    Kao, Yu-Hsuan; Liu, Chen-Wuing; Wang, Pei-Ling; Liao, Chung-Min

    2015-09-01

    This study evaluated the biogeochemical interactions between arsenic (As) and sulfur (S) in groundwater to understand the natural and anthropogenic influences of S redox processes on As mobilization in the Lanyang Plain, Taiwan. Cl- and the sulfate isotopic composition (δ34S[SO4]) were selected as conservative tracers. River water and saline seawater were considered as end members in the binary mixing model. Thirty-two groundwater samples were divided into four types of groundwater (I, pyrite-oxidation; II, iron- and sulfate-reducing; III, sulfate-reducing; and IV, anthropogenic and others). The binary mixing model coupled with discriminant analysis was applied to yield a classification with 97% correctness, indicating that the DO/ORP values and δ34S[SO4] and Fe2+ concentrations are effective redox-sensitive indicators. Type I groundwater is mostly located in a mountainous recharge area where pyrite oxidation is the major geochemical process. A high 18O enrichment factor (ε[SO4-H2O]) and high 34S enrichment factor (ε34S[FeS2-SO4]) indicate that disproportionation and dissimilatory sulfate reduction are both involved in Type II and Type III groundwater. The process of bacterial sulfate reduction may coprecipitate and sequester As, a mechanism that is unlikely to occur in Type II groundwater. The presence of high As and Fe2+ concentrations and enriched δ34S[SO4] in Type II groundwater suggest that biogeochemical reactions occurred under anaerobic conditions. The reductive dissolution of As-bearing Fe oxyhydroxides together with microbial disproportionation of sulfur explains the substantial correlations among the high As concentration and enriched δ34S[SO4] and Fe2+ concentrations in the iron- and sulfate-reducing zone (Type II). The As concentration in Type III groundwater (sulfate-reducing) is lower than that in Type II groundwater because of bacterial sulfate reduction and coprecipitation with As. Furthermore, the dissolution of sulfate minerals is not the

  5. Extracellular enzyme activity and microbial diversity measured on seafloor exposed basalts from Loihi seamount indicate the importance of basalts to global biogeochemical cycling.

    PubMed

    Jacobson Meyers, Myrna E; Sylvan, Jason B; Edwards, Katrina J

    2014-08-01

    Seafloor basalts are widely distributed and host diverse prokaryotic communities, but no data exist concerning the metabolic rates of the resident microbial communities. We present here potential extracellular enzyme activities of leucine aminopeptidase (LAP) and alkaline phosphatase (AP) measured on basalt samples from different locations on Loihi Seamount, HI, coupled with analysis of prokaryotic biomass and pyrosequencing of the bacterial 16S rRNA gene. The community maximum potential enzyme activity (Vmax) of LAP ranged from 0.47 to 0.90 nmol (g rock)(-1) h(-1); the Vmax for AP was 28 to 60 nmol (g rock)(-1) h(-1). The Km of LAP ranged from 26 to 33 μM, while the Km for AP was 2 to 7 μM. Bacterial communities on Loihi basalts were comprised primarily of Alpha-, Delta-, andGammaproteobacteria, Bacteroidetes, and Planctomycetes. The putative ability to produce LAP is evenly distributed across the most commonly detected bacterial orders, but the ability to produce AP is likely dominated by bacteria in the orders Xanthomonadales, Flavobacteriales, and Planctomycetales. The enzyme activities on Loihi basalts were compared to those of other marine environments that have been studied and were found to be similar in magnitude to those from continental shelf sediments and orders of magnitude higher than any measured in the water column, demonstrating that the potential for exposed basalts to transform organic matter is substantial. We propose that microbial communities on basaltic rock play a significant, quantifiable role in benthic biogeochemical processes. PMID:24907315

  6. Extracellular Enzyme Activity and Microbial Diversity Measured on Seafloor Exposed Basalts from Loihi Seamount Indicate the Importance of Basalts to Global Biogeochemical Cycling

    PubMed Central

    Sylvan, Jason B.; Edwards, Katrina J.

    2014-01-01

    Seafloor basalts are widely distributed and host diverse prokaryotic communities, but no data exist concerning the metabolic rates of the resident microbial communities. We present here potential extracellular enzyme activities of leucine aminopeptidase (LAP) and alkaline phosphatase (AP) measured on basalt samples from different locations on Loihi Seamount, HI, coupled with analysis of prokaryotic biomass and pyrosequencing of the bacterial 16S rRNA gene. The community maximum potential enzyme activity (Vmax) of LAP ranged from 0.47 to 0.90 nmol (g rock)−1 h−1; the Vmax for AP was 28 to 60 nmol (g rock)−1 h−1. The Km of LAP ranged from 26 to 33 μM, while the Km for AP was 2 to 7 μM. Bacterial communities on Loihi basalts were comprised primarily of Alpha-, Delta-, andGammaproteobacteria, Bacteroidetes, and Planctomycetes. The putative ability to produce LAP is evenly distributed across the most commonly detected bacterial orders, but the ability to produce AP is likely dominated by bacteria in the orders Xanthomonadales, Flavobacteriales, and Planctomycetales. The enzyme activities on Loihi basalts were compared to those of other marine environments that have been studied and were found to be similar in magnitude to those from continental shelf sediments and orders of magnitude higher than any measured in the water column, demonstrating that the potential for exposed basalts to transform organic matter is substantial. We propose that microbial communities on basaltic rock play a significant, quantifiable role in benthic biogeochemical processes. PMID:24907315

  7. Biogeochemical factors affecting the distribution, speciation, and transport of Hg species in the Deûle and Lys Rivers (Northern France).

    PubMed

    Daye, Mirna; Kadlecova, Milada; Ouddane, Baghdad

    2015-02-01

    The Deûle River is a highly polluted River by heavy metals caused by the historical discharges of ore minerals from the former ore smelter "Metaleurop." The potential mercury (Hg) pollution in the Deûle River implicates the importance of Hg distribution study in the river. As well as to configure the different biogeochemical factors that control the distribution and the potential transport of Hg to distant places. Four different sites were studied as follows: D-A (Deûle River, a site located upstream the river), D-B (Deûle River, a site located near a Zn, Pb, Cu, and Ni smelter that closed in 2003), L-C (Lys River, a site located upstream the confluence of the Deûle River with Lys River), and L-D (downstream the rivers confluence). Different Hg analyses were performed including total mercury in sediment (HgTS), methylmercury (MeHg) in sediment, total mercury in pore water (HgTPW), total mercury in surface water (HgTD), and total suspended particulate Hg in water (HgTP). HgTS decreases downstream from the Deûle River sites with a mean value of 11 ± 0.34 mg/kg to Lys River site (L-D) with a mean value of 0.53 ± 0.02 mg/kg at the confluence. The unaffected side of the Lys River, localized before the confluence (L-C), is characterized by low HgTS of an average value of 0.042 ± 0.003 mg/kg and high % MeHg reaching 4.2 %. Whereas, the highly contaminated Deûle sites are designated by low % MeHg with an average value of 0.053 %. Low pristine environments like that found in L-C site with more favorable biogeochemical conditions of lower concentrations of HgTS, sulfides, and Corg host more active biotic methylation than that of the highly polluted Deûle sites with high concentrations of HgTS and sulfides concentrations. Methylation in D-B (the closet site to Metaleurop smelter) is an old and recent methylation activity that has contributed to MeHg accumulation in the sediments as opposed to the exclusive recent events of methylation in Lys sites. Me

  8. Biogeochemical Processes in Microbial Ecosystems

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    The hierarchical organization of microbial ecosystems determines process rates that shape Earth's environment, create the biomarker sedimentary and atmospheric signatures of life and define the stage upon which major evolutionary events occurred. In order to understand how microorganisms have shaped the global environment of Earth and potentially, other worlds, we must develop an experimental paradigm that links biogeochemical processes with ever-changing temporal and spatial distributions of microbial population, and their metabolic properties. Photosynthetic microbial mats offer an opportunity to define holistic functionality at the millimeter scale. At the same time, their Biogeochemistry contributes to environmental processes on a planetary scale. These mats are possibly direct descendents of the most ancient biological communities; communities in which oxygenic photosynthesis might have been invented. Mats provide one of the best natural systems to study how microbial populations associate to control dynamic biogeochemical gradients. These are self-sustaining, complete ecosystems in which light energy absorbed over a diel (24 hour) cycle drives the synthesis of spatially-organized, diverse biomass. Tightly-coupled microorganisms in the mat have specialized metabolisms that catalyze transformations of carbon, nitrogen. sulfur, and a host of other elements.

  9. Low-intensity cycling affects the muscle activation pattern of consequent countermovement jumps.

    PubMed

    Marquez, Gonzalo J; Mon, Javier; Acero, Rafael M; Sanchez, Jose A; Fernandez-del-Olmo, Miguel

    2009-08-01

    Players (eg, basketball, soccer, and football) often use a static bicycle during a game to maintain warming. However, the effectiveness of this procedure has not been addressed in the literature. Thus, it remains unknown whether low-intensity cycling movement can affect explosive movement performance. In this study, 10 male subjects performed countermovement jumps before and after a 15-minutes cycling bout at 35% of their maximal power output. Three sessions were tested for 3 different cadences of cycling: freely chosen cadence, 20% lower than freely chosen cadence (FCC-20%), and 20% higher than freely chosen cadence (FCC+20%). Jump height, kinematics, and electromyogram were recorded simultaneously during the countermovement jumps. The results showed a significant decreasing in the height of countermovement jump after cycling at freely chosen cadence and FCC-20% (p = 0.03 and p = 0.04, respectively), but not for FCC+20% cadences. The electromyographic parameters suggest that changes in the countermovement jump after cycling can be attributed to alteration of the pattern of activation and may be modulated by the preceding cycling cadence. Our study indicates that to avoid a possible negative effect of the cycling in the subsequent explosive movements, a cadence 20% higher than the preferred cadence must be used. PMID:19620918

  10. Ancient Organic Matter Sources to the Hudson-Mohawk River System: Implications of Riverine Transport of Ancient Organic Matter for the Global Biogeochemical Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Longworth, B. E.; Petsch, S. T.; Raymond, P. A.

    2003-12-01

    The connection between erosion of rocks on the continents and deposition of marine sediments is riverine transport. Rivers are an important component of both the contemporary and long-term geologic carbon cycles. They erode ancient organic matter [OM] buried in sedimentary rock, carbon stored in soils, and carbonate bearing rock. Current understanding is that ancient OM is chemically and biologically reactive during weathering and riverine transport. However, while much OM exposed during weathering and transport is oxidized to CO2, a significant portion is not remineralized, but instead is delivered downstream and reburied in marine sediments. This riverine conduit potentially allows ancient organic carbon to remain chemically distinct from pools of the contemporary carbon cycle. If a significant portion of ancient organic carbon remains sequestered in reduced form via this mechanism, there are important implications for the global carbon cycle over geologic time. These include carbon isotope effects, reservoir sizes and turnover rates, and ultimately, the composition of earth's atmosphere over geologic time. The Ordovician and Devonian shales of the Hudson-Mohawk watershed in upstate New York, USA, provide an ideal location to study the behavior of OM in a river system. In this study, we quantify sources of the dissolved and particulate organic carbon load of headwater streams draining these organic rich black shales using isotopic and molecular tracers of organic matter source. These tracers include stable isotopes of carbon and nitrogen, radiocarbon isotope ratios, and chromatographic signatures produced by pyrolysis-GC. We employ a GIS-based matrix of field sites in watersheds of contrasting lithology (OM-rich shales vs. OM-free crystalline basement) and surface cover, under the assumption that the two main controls on riverine carbon under similar climatic conditions are land use and underlying rock type. Samples include stream waters as well as endmember

  11. Genomic Copy Number Variation Affecting Genes Involved in the Cell Cycle Pathway: Implications for Somatic Mosaicism

    PubMed Central

    Iourov, Ivan Y.; Vorsanova, Svetlana G.; Zelenova, Maria A.; Korostelev, Sergei A.; Yurov, Yuri B.

    2015-01-01

    Somatic genome variations (mosaicism) seem to represent a common mechanism for human intercellular/interindividual diversity in health and disease. However, origins and mechanisms of somatic mosaicism remain a matter of conjecture. Recently, it has been hypothesized that zygotic genomic variation naturally occurring in humans is likely to predispose to nonheritable genetic changes (aneuploidy) acquired during the lifetime through affecting cell cycle regulation, genome stability maintenance, and related pathways. Here, we have evaluated genomic copy number variation (CNV) in genes implicated in the cell cycle pathway (according to Kyoto Encyclopedia of Genes and Genomes/KEGG) within a cohort of patients with intellectual disability, autism, and/or epilepsy, in which the phenotype was not associated with genomic rearrangements altering this pathway. Benign CNVs affecting 20 genes of the cell cycle pathway were detected in 161 out of 255 patients (71.6%). Among them, 62 individuals exhibited >2 CNVs affecting the cell cycle pathway. Taking into account the number of individuals demonstrating CNV of these genes, a support for this hypothesis appears to be presented. Accordingly, we speculate that further studies of CNV burden across the genes implicated in related pathways might clarify whether zygotic genomic variation generates somatic mosaicism in health and disease. PMID:26421275

  12. Ge/Si, Ca/Sr and 87Sr/86Sr tracers of biogeochemical sources and cycling of Si and Ca at the Shale Hills CZO

    NASA Astrophysics Data System (ADS)

    Derry, L. A.; Meek, K.; Sparks, J. P.

    2014-12-01

    Plant uptake and cycling of nutrients is commonly the largest flux of nutrients in terrestrial ecosystems. Hydrologic and other losses are offset by inputs from atmospheric deposition and weathering. We measured elemental and isotopic compositions from soil solution, soil exchange complex, leaves and sapwater from two canopy species, soil and rock samples, and stream and ground waters at the Shale Hills CZO. Xylem fluid and leaf samples have similar Ge/Si < 1 μmo/mol, consistent with fractionation at the root-soil water interface. Ge/Si in soil waters is higher Ge/Si near the surface and increases over the growing season, indicating preferential uptake of Si. Ca/Sr in leaves of Quercus are significantly higher (450±150) than for Acer (200±100), and Ca/Sr is generally higher in leaves than in xylem, consistent with Ca uptake during transpiration. 87Sr/86Sr in both are similar for a given site, implying that the trees access similar pools of Sr and Ca, although there are site-to-site differences. Data on litterfall rates and transpiration rates yield similar estimates of plant cycling of Ca and Si. 87Sr/86Sr in soil solutions from ridgtop and swale sites are well explained by mixing Sr derived from shale and atmospheric deposition. Valley bottom soil solutions and stream and groundwater samples include Sr and Ca derived from dissolution of diagenetic carbonates, found in drill cuttings. A preliminary estimate of the Sr and Ca stream fluxes and isotopic mass balances imply propagation of a carbonate weathering front of ca. 200 m/Ma, faster than previously reported regolith weathering advance rates based on on cosmogenic nuclides and U series (Jin et al., 2010; Ma et al., 2010). These rates are not strictly comparable and differences are at least in part consistent with the greater depth of the carbonate weathering front (Brantley et al, 2013). The data for Ca, Sr, Si and Ge in soil, soil solutions and stream waters reflects the interaction of slower weathering

  13. Scrapie affects the maturation cycle and immune complex trapping by follicular dendritic cells in mice.

    PubMed

    McGovern, Gillian; Mabbott, Neil; Jeffrey, Martin

    2009-01-01

    Transmissible spongiform encephalopathies (TSEs) or prion diseases are infectious neurological disorders of man and animals, characterised by abnormal disease-associated prion protein (PrP(d)) accumulations in the brain and lymphoreticular system (LRS). Prior to neuroinvasion, TSE agents often accumulate to high levels within the LRS, apparently without affecting immune function. However, our analysis of scrapie-affected sheep shows that PrP(d) accumulations within the LRS are associated with morphological changes to follicular dendritic cells (FDCs) and tingible body macrophages (TBMs). Here we examined FDCs and TBMs in the mesenteric lymph nodes (MLNs) of scrapie-affected mice by light and electron microscopy. In MLNs from uninfected mice, FDCs could be morphologically categorised into immature, mature and regressing forms. However, in scrapie-affected MLNs this maturation cycle was adversely affected. FDCs characteristically trap and retain immune complexes on their surfaces, which they display to B-lymphocytes. In scrapie-affected MLNs, some FDCs were found where areas of normal and abnormal immune complex retention occurred side by side. The latter co-localised with PrP(d) plasmalemmal accumulations. Our data suggest this previously unrecognised morphology represents the initial stage of an abnormal FDC maturation cycle. Alterations to the FDCs included PrP(d) accumulation, abnormal cell membrane ubiquitin and excess immunoglobulin accumulation. Regressing FDCs, in contrast, appeared to lose their membrane-attached PrP(d). Together, these data suggest that TSE infection adversely affects the maturation and regression cycle of FDCs, and that PrP(d) accumulation is causally linked to the abnormal pathology observed. We therefore support the hypothesis that TSEs cause an abnormality in immune function. PMID:19997557

  14. Temporal and spatial variations in the biogeochemical cycling of cobalt in two urban estuaries: Hudson River Estuary and San Francisco Bay

    NASA Astrophysics Data System (ADS)

    Tovar-Sánchez, Antonio; Sañudo-Wilhelmy, Sergio A.; Flegal, A. Russell

    2004-08-01

    Despite the fact that Co is an essential trace element for the growth of marine phytoplankton, there is very limited information on the cycling of this trace metal in the marine environment. We report here the distribution of dissolved (<0.4 μm) and particulate (>0.4 μm) Co in surface waters of the Hudson River Estuary (HRE) and San Francisco Bay (SFB). Samples were collected during several cruises (from 1990 to 1995 in SFB and from 1995 to 1997 in the HRE) along the whole salinity gradient. Dissolved Co concentrations (mean±1 standard deviation) were nearly identical in magnitude in both estuaries despite differences in climate, hydrography, riverine-flow conditions and land-usage (HRE=0.91±0.61 nM; SFB=1.12±0.69 nM). Dissolved Co levels in each system showed non-conservative distributions when plotted as a function of salinity, with increasing concentrations downstream from the riverine end-members. Desorption from suspended particulates and sewage inputs, therefore, seems to be the major processes responsible for the non-conservative behavior of Co observed. Mass balance estimates also indicated that most of the estuarine Co is exported out of both estuaries, indicating that they and other estuarine systems are principal sources of this essential trace element to the open ocean.

  15. Loss of phytotelmata due to an invasive bromeliad-eating weevil and its potential effects on faunal diversity and biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Cooper, Teresa M.; Frank, J. Howard; Cave, Ronald D.

    2014-01-01

    Epiphytic tank bromeliads are important ecosystem engineers because they form phytotelmata that create habitat, increase species richness and abundance, create water sources and nutrient reservoirs in the canopy, and collect and redirect nutrients in forest ecosystems. Native bromeliad populations have been devastated in Florida (USA) because an invasive bromeliad-eating weevil (Metamasius callizona) has been destroying the plants. Tillandsia utriculata is a tank bromeliad that was once widespread from central to south Florida. Its populations have been hit hard by the weevil and are declining rapidly. This study quantifies the mortality rate caused by the weevil in a population of T. utriculata at the Enchanted Forest Sanctuary in central Florida and estimates the associated loss of phytotelmata. Estimations of phytotelmata were calculated for the T. utriculata baseline population, the population at 6 months into the study when 87% of the population was destroyed, and at the end of the study when less than 3% of the bromeliad population remained (99% of all deaths were caused by the weevil). The baseline population contained 16,758 L of water. At six months, there were 3180 L, and at the end of the study, there were 408 L. The loss of phytotelmata results in the loss of habitat, a decrease in biological diversity, and altered water and nutrient cycles and availability.

  16. The acid and alkalinity budgets of weathering in the Andes-Amazon system: Insights into the erosional control of global biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Torres, Mark A.; West, A. Joshua; Clark, Kathryn E.; Paris, Guillaume; Bouchez, Julien; Ponton, Camilo; Feakins, Sarah J.; Galy, Valier; Adkins, Jess F.

    2016-09-01

    The correlation between chemical weathering fluxes and denudation rates suggests that tectonic activity can force variations in atmospheric pCO2 by modulating weathering fluxes. However, the effect of weathering on pCO2 is not solely determined by the total mass flux. Instead, the effect of weathering on pCO2 also depends upon the balance between 1) alkalinity generation by carbonate and silicate mineral dissolution and 2) sulfuric acid generation by the oxidation of sulfide minerals. In this study, we explore how the balance between acid and alkalinity generation varies with tectonic uplift to better understand the links between tectonics and the long-term carbon cycle. To trace weathering reactions across the transition from the Peruvian Andes to the Amazonian foreland basin, we measured a suite of elemental concentrations (Na, K, Ca, Mg, Sr, Si, Li, SO4, and Cl) and isotopic ratios (87Sr/86Sr and δ34S) on both dissolved and solid phase samples. Using an inverse model, we quantitatively link systematic changes in solute geochemistry with elevation to downstream declines in sulfuric acid weathering as well as the proportion of cations sourced from silicates. With a new carbonate-system framework, we show that weathering in the Andes Mountains is a CO2 source whereas foreland weathering is a CO2 sink. These results are consistent with the theoretical expectation that the ratio of sulfide oxidation to silicate weathering increases with increasing erosion. Altogether, our results suggest that the effect of tectonically-enhanced weathering on atmospheric pCO2 is strongly modulated by sulfide mineral oxidation.

  17. Climate change effects on watershed hydrological and biogeochemical processes

    EPA Science Inventory

    Projected changes in climate are widely expected to alter watershed processes. However, the extent of these changes is difficult to predict because complex interactions among affected hydrological and biogeochemical processes will likely play out over many decades and spatial sc...

  18. Evolution of biogeochemical cycling of phosphorus during 45~50 Ma revealed by sequential extraction analysis of IODP Expedition 302 cores from the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Hashimoto, S.; Yamaguchi, K. E.; Takahashi, K.

    2012-12-01

    The modern Arctic Ocean plays crucial roles in controlling global climate system with the driving force of global thermohaline circulation through the formation of dense deep water and high albedo due to the presence of perennial sea-ice. However, the Arctic sea-ice has not always existed in the past. Integrated Ocean Drilling Program (IODP) Expedition 302 Arctic Coring Expedition (ACEX) has clarified that global warming (water temperature: ca. 14~16○C) during 48~49 Ma Azolla Event induced the loss of sea-ice and desalination of surface ocean, and that sea-ice formed again some million years later (45 Ma). In the Arctic Ocean, warming and cooling events repeated over and over (e.g., Brinkhuis et al., 2006; Moran et al., 2006; März et al., 2010). Large variations in the extent of thermohaline circulation through time often caused stagnation of seawater and appearance of anaerobic environment where hydrogen sulfide was produced by bacterial sulfate reduction. Ogawa et al. (2009) confirmed occurrence of framboidal pyrite in the ACEX sediments, and suggested that the Arctic Ocean at the time was anoxic, analogous to the modern Black Sea, mainly based on sulfur isotope analysis. To further clarify the variations in the nutrient status of the Arctic Ocean, we focus on the geochemical cycle of phosphorus. We performed sequential extraction analysis of sedimentary phosphorus in the ACEX sediments, using the method that we improvped based on the original SEDEX method by Ruttenberg (1992) and Schenau et al. (2000). In our method, phosphorus fractions are divided into five forms; (1) absorbed P, (2) Feoxide-P, (4) carbonate fluorapatite (CFAP) + CaCO3-P + hydroxylapatite (HAP), (4) detrital P, and (5) organic P. Schenau et al. (2000) divided the (3) fraction into non-biological CFAP and biological HAP and CaCO3-P. When the Arctic Ocean was closed and in its warming period, the water mass was most likely stratified and an anaerobic condition would have prevailed where

  19. Menstrual cycle phase does not affect sympathetic neural activity in women with postural orthostatic tachycardia syndrome

    PubMed Central

    Stickford, Abigail SL; VanGundy, Tiffany B; Levine, Benjamin D; Fu, Qi

    2015-01-01

    Abstract Patients with the postural orthostatic tachycardia syndrome (POTS) are primarily premenopausal women, which may be attributed to female sex hormones. We tested the hypothesis that hormonal fluctuations of the menstrual cycle alter sympathetic neural activity and orthostatic tolerance in POTS women. Ten POTS women were studied during the early follicular (EF) and mid-luteal (ML) phases of the menstrual cycle. Haemodynamics and muscle sympathetic nerve activity (MSNA) were measured when supine, during 60 deg upright tilt for 45 min or until presyncope, and during the cold pressor test (CPT) and Valsalva manoeuvres. Blood pressure and total peripheral resistance were higher during rest and tilting in the ML than EF phase; however, heart rate, stroke volume and cardiac output were similar between phases. There were no mean ± SD differences in MSNA burst frequency (8 ± 8 EF phase vs. 10 ± 10 bursts min–1 ML phase at rest; 34 ± 15 EF phase vs. 36 ± 16 bursts min–1 ML phase at 5 min tilt), burst incidence or total activity, nor any differences in the cardiovagal and sympathetic baroreflex sensitivities between phases under any condition. The incidence of presyncope was also the same between phases. There were no differences in haemodynamic or sympathetic responses to CPT or Valsalva. These results suggest that the menstrual cycle does not affect sympathetic neural activity but modulates blood pressure and vasoconstriction in POTS women during tilting. Thus, factors other than sympathetic neural activity are probably responsible for the symptoms of orthostatic intolerance across the menstrual cycle in women with POTS. Key points Women with the postural orthostatic tachycardia syndrome (POTS) report fluctuations in orthostatic tolerance throughout the menstrual cycle. The mechanism(s) underlying blood pressure control across the menstrual cycle in women with POTS are unknown. The findings of the present study indicate that the menstrual

  20. Modeling greenhouse gas emissions (CO2, N2O, CH4) from managed arable soils with a fully coupled hydrology-biogeochemical modeling system simulating water and nutrient transport and associated carbon and nitrogen cycling at catchment scale

    NASA Astrophysics Data System (ADS)

    Klatt, Steffen; Haas, Edwin; Kraus, David; Kiese, Ralf; Butterbach-Bahl, Klaus; Kraft, Philipp; Plesca, Ina; Breuer, Lutz; Zhu, Bo; Zhou, Minghua; Zhang, Wei; Zheng, Xunhua; Wlotzka, Martin; Heuveline, Vincent

    2014-05-01

    The use of mineral nitrogen fertilizer sustains the global food production and therefore the livelihood of human kind. The rise in world population will put pressure on the global agricultural system to increase its productivity leading most likely to an intensification of mineral nitrogen fertilizer use. The fate of excess nitrogen and its distribution within landscapes is manifold. Process knowledge on the site scale has rapidly grown in recent years and models have been developed to simulate carbon and nitrogen cycling in managed ecosystems on the site scale. Despite first regional studies, the carbon and nitrogen cycling on the landscape or catchment scale is not fully understood. In this study we present a newly developed modelling approach by coupling the fully distributed hydrology model CMF (catchment modelling framework) to the process based regional ecosystem model LandscapeDNDC for the investigation of hydrological processes and carbon and nitrogen transport and cycling, with a focus on nutrient displacement and resulting greenhouse gas emissions in a small catchment at the Yanting Agro-ecological Experimental Station of Purple Soil, Sichuan province, China. The catchment hosts cypress forests on the outer regions, arable fields on the sloping croplands cultivated with wheat-maize rotations and paddy rice fields in the lowland. The catchment consists of 300 polygons vertically stratified into 10 soil layers. Ecosystem states (soil water content and nutrients) and fluxes (evapotranspiration) are exchanged between the models at high temporal scales (hourly to daily) forming a 3-dimensional model application. The water flux and nutrients transport in the soil is modelled using a 3D Richards/Darcy approach for subsurface fluxes with a kinematic wave approach for surface water runoff and the evapotranspiration is based on Penman-Monteith. Biogeochemical processes are modelled by LandscapeDNDC, including soil microclimate, plant growth and biomass allocation

  1. The general ensemble biogeochemical modeling system (GEMS) and its applications to agriculture systems in the United States

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The General Ensemble Biogeochemical Modeling System (GEMS) was developed for a proper integration of well-established ecosystem biogeochemical models with various spatial databases to simulate biogeochemical cycles over large areas. Major driving variables include land cover and land use, climate, s...

  2. Biogeochemical weathering under ice: Size matters

    NASA Astrophysics Data System (ADS)

    Wadham, J. L.; Tranter, M.; Skidmore, M.; Hodson, A. J.; Priscu, J.; Lyons, W. B.; Sharp, M.; Wynn, P.; Jackson, M.

    2010-09-01

    The basal regions of continental ice sheets are gaps in our current understanding of the Earth's biosphere and biogeochemical cycles. We draw on existing and new chemical data sets for subglacial meltwaters to provide the first comprehensive assessment of sub-ice sheet biogeochemical weathering. We show that size of the ice mass is a critical control on the balance of chemical weathering processes and that microbial activity is ubiquitous in driving dissolution. Carbonate dissolution fueled by sulfide oxidation and microbial CO2 dominate beneath small valley glaciers. Prolonged meltwater residence times and greater isolation characteristic of ice sheets lead to the development of anoxia and enhanced silicate dissolution due to calcite saturation. We show that sub-ice sheet environments are highly geochemically reactive and should be considered in regional and global solute budgets. For example, calculated solute fluxes from Antarctica (72-130 t yr-1) are the same order of magnitude as those from some of the world's largest rivers and rates of chemical weathering (10-17 t km-2 yr-1) are high for the annual specific discharge (2.3-4.1 × 10-3 m). Our model of chemical weathering dynamics provides important information on subglacial biodiversity and global biogeochemical cycles and may be used to design strategies for the first sampling of Antarctic Subglacial Lakes and other sub-ice sheet environments for the next decade.

  3. Microbial H2 cycling does not affect δ2H values of ground water

    USGS Publications Warehouse

    Landmeyer, J.E.; Chapelle, F.H.; Bradley, P.M.

    2000-01-01

    Stable hydrogen-isotope values of ground water (δ2H) and dissolved hydrogen concentrations (H(2(aq)) were quantified in a petroleum-hydrocarbon contaminated aquifer to determine whether the production/consumption of H2 by subsurface microorganisms affects ground water &delta2H values. The range of &delta2H observed in monitoring wells sampled (-27.8 ‰c to -15.5 ‰c) was best explained, however, by seasonal differences in recharge temperature as indicated using ground water δ18O values, rather than isotopic exchange reactions involving the microbial cycling of H2 during anaerobic petroleum-hydrocarbon biodegradation. The absence of a measurable hydrogen-isotope exchange between microbially cycled H2 and ground water reflects the fact that the amount of H2 available from the anaerobic decomposition of petroleum hydrocarbons is small relative to the amount of hydrogen present in water, even though milligram per liter concentrations of readily biodegradable contaminants are present at the study site. Additionally, isotopic fractionation calculations indicate that in order for H2 cycling processes to affect δ2H values of ground water, relatively high concentrations of H2 (>0.080 M) would have to be maintained, considerably higher than the 0.2 to 26 nM present at this site and characteristic of anaerobic conditions in general. These observations suggest that the conventional approach of using δ2H and δ18O values to determine recharge history is appropriate even for those ground water systems characterized by anaerobic conditions and extensive microbial H2 cycling.

  4. Factors affecting gestation length and estrus cycle characteristics in Spanish donkey breeds reared in southern Spain.

    PubMed

    Galisteo, J; Perez-Marin, C C

    2010-08-01

    This paper investigated gestation length and estrus cycle characteristics in three different Spanish donkey breeds (Andalusian, Zamorano-Leones, and Catalonian) kept on farm conditions in southern Spain, using data for ten consecutive breeding seasons. Gestation length was measured in 58 pregnancies. Ovarian ultrasonography was used to detect the ovulation, in order to ascertain true gestation length (ovulation-parturition). Pregnancy was diagnosed approximately 14-18 d after ovulation and confirmed on approximately day 60. Average gestation length was 362 +/-15.3 (SD) d, and no significant differences were observed between the three different breeds. Breeding season had a significant effect (P < 0.01), with longer gestation lengths when jennies were covered during the early period. Breed, age of jenny, year of birth, foal gender, month of breeding, and type of gestation had no significant effect on gestation length. After parturition, foal-heat was detected in 53.8% of the postpartum cycles studied (n = 78), and ovulation occurred on day 13.2 +/- 2.7. The duration of foal-heat was 4.7 +/-1.7 d, with a pregnancy rate of 40.5%. When subsequent estrus cycles were analyzed, the interovulatory interval (n = 68) and estrus duration (n = 258) were extended to a mean 23.8 +/- 3.5 and 5.7 +/- 2.2 d, respectively. Both variables were influenced by the year of study (P < 0.03 and P < 0.001), whereas month and season of ovulation (P < 0.005 and P < 0.009, respectively) affected only interovulatory intervals. Estrus duration was significantly longer than that observed at the foal-heat (P < 0.006), and the pregnancy rate was 65.8%. This study provides reference values for true gestation length and estrus cycle characteristics in Spanish jennies. Breeding season affected gestation length in farm conditions. Also, seasonal influence was observed on the length of the estrus cycle (i.e., interovulatory interval), although foal-heat was not affected by environmental factors. PMID

  5. 5-ASA Affects Cell Cycle Progression in Colorectal Cells by Reversibly Activating a Replication Checkpoint

    PubMed Central

    LUCIANI, M. GLORIA; CAMPREGHER, CHRISTOPH; FORTUNE, JOHN M.; KUNKEL, THOMAS A.; GASCHE, CHRISTOPH

    2007-01-01

    Background & Aims Individuals with inflammatory bowel disease are at risk of developing colorectal cancer (CRC). Epidemiologic, animal, and laboratory studies suggest that 5-amino-salicylic acid (5-ASA) protects from the development of CRC by altering cell cycle progression and by inducing apoptosis. Our previous results indicate that 5-ASA improves replication fidelity in colorectal cells, an effect that is active in reducing mutations. In this study, we hypothesized that 5-ASA restrains cell cycle progression by activating checkpoint pathways in colorectal cell lines, which would prevent tumor development and improve genomic stability. Methods CRC cells with different genetic backgrounds such as HT29, HCT116, HCT116p53−/−, HCT116+chr3, and LoVo were treated with 5-ASA for 2–96 hours. Cell cycle progression, phosphorylation, and DNA binding of cell cycle checkpoint proteins were analyzed. Results We found that 5-ASA at concentrations between 10 and 40 mmol/L affects cell cycle progression by inducing cells to accumulate in the S phase. This effect was independent of the hMLH1, hMSH2, and p53 status because it was observed to a similar extent in all cell lines under investigation. Moreover, wash-out experiments demonstrated reversibility within 48 hours. Although p53 did not have a causative role, p53 Ser15 was strongly phosphorylated. Proteins involved in the ATM-and-Rad3-related kinase (ATR)-dependent S-phase checkpoint response (Chk1 and Rad17) were also phosphorylated but not ataxia telengectasia mutated kinase. Conclusions Our data demonstrate that 5-ASA causes cells to reversibly accumulate in S phase and activate an ATR-dependent checkpoint. The activation of replication checkpoint may slow down DNA replication and improve DNA replication fidelity, which increases the maintenance of genomic stability and counteracts carcinogenesis. PMID:17241873

  6. Change in photoperiodic cycle affects life span in a prosimian primate (Microcebus murinus).

    PubMed

    Perret, M

    1997-04-01

    The lesser mouse lemur, a small prosimian primate, exhibits seasonal rhythms strictly controlled by photoperiodic variations. Exposure to day lengths shorter than 12 h results in complete sexual rest, fattening, lethargy, and reduced behavioral activities; whereas exposure to day lengths greater than 12 h induces sexual activity, an increase in behavioral activities, and high hormonal levels. The objective of this study was to test whether long-term acceleration of seasonal rhythms may affect survival and longevity of this primate. In captivity, acceleration of seasonal rhythms was obtained by exposing the animals to an accelerated photoperiodic regimen consisting of 5 months of long photoperiod followed by 3 months of short photoperiod. The age-specific survival rate in animals exposed from birth to accelerated photoperiodic conditions (n = 89) was compared to the age-specific survival rate of animals maintained under a natural photoperiod (n = 68). Independent of sexes, the mean life span (45.5 +/- 2.1 months) and maximal survival (79.3 +/- 3.3 months) were significantly (p < .01) shortened in mouse lemurs exposed to the accelerated photoperiodic cycle compared to those in animals living under annual photoperiod (63.2 +/- 2.5 and 98 +/- 3.9 months for mean life span and maximal survival, respectively). This reduction of about 30% of life span was not accompanied by a desynchronization of biological rhythms under photoperiodic control and was not related to an increase in reproduction or in duration of time spent in active conditions. However, when the number of seasonal cycles experienced by 1 individual is considered rather than chronological age, the mean life span was 5 seasonal cycles and maximum survival reached 9-10 cycles, independent of sex or of photoperiodic regimen. These results suggest that in mouse lemurs, as in other seasonal mammals, longevity may depend on the expression of a fixed number of seasonal cycles rather than on a fixed biological age

  7. TRANSIENT BIOGEOCHEMICAL CYCLING AND SEDIMENT OXYGEN DEMAND

    EPA Science Inventory

    Through this research, the effects of variable sediment accumulation and oxygen concentration on SOD and soluble chemical fluxes will be quantified. This study will enable correct estimates of “diffuser-induced” SOD to be made that will facilitate appropriate desig...

  8. Terminal Proterozoic reorganization of biogeochemical cycles

    NASA Technical Reports Server (NTRS)

    Logan, G. A.; Hayes, J. M.; Hieshima, G. B.; Summons, R. E.

    1995-01-01

    The Proterozoic aeon (2,500-540 million years ago) saw episodic increases in atmospheric oxygen content, the evolution of multicellular life and, at its close, an enormous radiation of animal diversity. These profound biological and environmental changes must have been linked, but the underlying mechanisms have been obscure. Here we show that hydrocarbons extracted from Proterozoic sediments in several locations worldwide are derived mainly from bacteria or other heterotrophs rather than from photosynthetic organisms. Biodegradation of algal products in sedimenting matter was therefore unusually complete, indicating that organic material was extensively reworked as it sank slowly through the water column. We propose that a significant proportion of this reworking will have been mediated by sulphate-reducing bacteria, forming sulphide. The production of sulphide and consumption of oxygen near the ocean surface will have inhibited transport of O2 to the deep ocean. We find that preservation of algal-lipid skeletons improves at the beginning of the Cambrian, reflecting the increase in transport by rapidly sinking faecal pellets. We suggest that this rapid removal of organic matter will have increased oxygenation of surface waters, leading to a descent of the O2-sulphide interface to the sea floor and to marked changes in the marine environment, ultimately contributing to the Cambrian radiation.

  9. Menstrual cycle and sex affect hemodynamic responses to combined orthostatic and heat stress.

    PubMed

    Meendering, Jessica R; Torgrimson, Britta N; Houghton, Belinda L; Halliwill, John R; Minson, Christopher T

    2005-08-01

    Women have decreased orthostatic tolerance compared with men, and anecdotal evidence suggests women are more susceptible to orthostatic intolerance in warm environments. Because estrogen and progesterone affect numerous physiological variables that may alter orthostatic tolerance, the purpose of our study was to compare orthostatic tolerance across the menstrual cycle phases in women during combined orthostatic and heat stress and to compare these data with those of men. Eight normally menstruating women and eight males (22 +/- 4.0 and 23 +/- 3.5 yr, respectively) completed the protocol. Women were studied during their early follicular (EF), ovulatory (OV), and midluteal (ML) phases. Men were studied twice within 2-4 wk. Heart rate, cardiac output, blood pressure, core temperature (T(c)), and cutaneous vascular conductance (CVC) were measured during three head-up tilt tests, consisting of two tilts in the thermoneutral condition and one tilt after a 0.5 degrees C rise in T(c). There was no difference in orthostatic tolerance across the menstrual cycle phases, despite higher CVC in the ML phase after heating (EF, 42.3 +/- 4.8; OV, 40.1 +/- 3.7; ML, 57.5 +/- 4.5; P < 0.05). Orthostatic tolerance in the heat was greater in men than women (P < 0.05). These data suggest that although many physiological variables associated with blood pressure regulation fluctuate during the menstrual cycle, orthostatic tolerance in the heat remains unchanged. Additionally, our data support a clear sex difference in orthostatic tolerance and extend upon previous data to show that the sex difference in the heat is not attributable to fluctuating hormone profiles during the menstrual cycle. PMID:15778279

  10. Coastal-zone biogeochemical dynamics under global warming

    SciTech Connect

    Mackenzie, F.T.; Ver, L.M.; Lerman, A.

    2000-03-01

    The coastal zone, consisting of the continental shelves to a depth of 200 meters, including bays, lagoons, estuaries, and near-shore banks, is an environment that is strongly affected by its biogeochemical and physical interactions with reservoirs in the adjacent domains of land, atmosphere, open ocean, and marine sediments. Because the coastal zone is smaller in volume and area coverage relative to the open ocean, it traditionally has been studied as an integral part of the global oceans. In this paper, the authors show by numerical modeling that it is important to consider the coastal zone as an entity separate from the open ocean in any assessment of future Earth-system response under human perturbation. Model analyses for the early part of the 21st century suggest that the coastal zone plays a significant modifying role in the biogeochemical dynamics of the carbon cycle and the nutrient cycles coupled to it. This role is manifested in changes in primary production, storage, and/or export of organic matter, its remineralization, and calcium carbonate precipitation--all of which determine the state of the coastal zone with respect to exchange of CO{sub 2} with the atmosphere. Under a scenario of future reduced or complete cessation of the thermohaline circulation (THC) of the global oceans, coastal waters become an important sink for atmospheric CO{sub 2}, as opposed to the conditions in the past and present, when coastal waters are believed to be a source of CO{sub 2} to the atmosphere. Profound changes in coastal-zone primary productivity underscore the important role of phosphorus as a limiting nutrient. In addition, calculations indicate that the saturation state of coastal waters with respect to carbonate minerals will decline by {approximately}15% by the year 2030. Any future slowdown in the THC of the oceans will increase slightly the rate of decline in saturation state.

  11. Biogeochemical drivers of phosphatase activity in salt marsh sediments

    NASA Astrophysics Data System (ADS)

    Freitas, Joana; Duarte, Bernardo; Caçador, Isabel

    2014-10-01

    Although nitrogen has become a major concern for wetlands scientists dealing with eutrophication problems, phosphorous represents another key element, and consequently its biogeochemical cycling has a crucial role in eutrophication processes. Microbial communities are a central component in trophic dynamics and biogeochemical processes on coastal systems, since most of the processes in sediments are microbial-mediated due to enzymatic action, including the mineralization of organic phosphorus carried out by acid phosphatase activity. In the present work, the authors investigate the biogeochemical sediment drivers that control phosphatase activities. Authors also aim to assess biogeochemical factors' influence on the enzyme-mediated phosphorous cycling processes in salt marshes. Plant rhizosediments and bare sediments were collected and biogeochemical features, including phosphatase activities, inorganic and organic phosphorus contents, humic acids content and pH, were assessed. Acid phosphatase was found to give the highest contribution for total phosphatase activity among the three pH-isoforms present in salt marsh sediments, favored by acid pH in colonized sediments. Humic acids also appear to have an important role inhibiting phosphatase activity. A clear relation of phosphatase activity and inorganic phosphorous was also found. The data presented reinforces the role of phosphatase in phosphorous cycling.

  12. Diel biogeochemical processes in terrestrial waters

    USGS Publications Warehouse

    Compiled and Edited by Nimick, David A.; Gammons, Christopher H.

    2011-01-01

    Many biogeochemical processes in rivers and lakes respond to the solar photocycle and produce persistent patterns of measureable phenomena that exhibit a day-night, or 24-h, cycle. Despite a large body of recent literature, the mechanisms responsible for these diel fluctuations are widely debated, with a growing consensus that combinations of physical, chemical, and biological processes are involved. These processes include streamflow variation, photosynthesis and respiration, plant assimilation, and reactions involving photochemistry, adsorption and desorption, and mineral precipitation and dissolution. Diel changes in streamflow and water properties such as temperature, pH, and dissolved oxygen concentration have been widely recognized, and recently, diel studies have focused more widely by considering other constituents such as dissolved and particulate trace metals, metalloids, rare earth elements, mercury, organic matter, dissolved inorganic carbon (DIC), and nutrients. The details of many diel processes are being studied using stable isotopes, which also can exhibit diel cycles in response to microbial metabolism, photosynthesis and respiration, or changes in phase, speciation, or redox state. In addition, secondary effects that diel cycles might have, for example, on biota or in the hyporheic zone are beginning to be considered. This special issue is composed primarily of papers presented at the topical session "Diurnal Biogeochemical Processes in Rivers, Lakes, and Shallow Groundwater" held at the annual meeting of the Geological Society of America in October 2009 in Portland, Oregon. This session was organized because many of the growing number of diel studies have addressed just a small part of the full range of diel cycling phenomena found in rivers and lakes. This limited focus is understandable because (1) fundamental aspects of many diel processes are poorly understood and require detailed study, (2) the interests and expertise of individual

  13. Aquaporin-1 plays important role in proliferation by affecting cell cycle progression.

    PubMed

    Galán-Cobo, Ana; Ramírez-Lorca, Reposo; Toledo-Aral, Juan José; Echevarría, Miriam

    2016-01-01

    Aquaporin-1 (AQP1) has been associated with tumor development. Here, we investigated how AQP1 may affect cell proliferation. The proliferative rate of adult carotid body (CB) cells, known to proliferate under chronic hypoxia, was analyzed in wild-type (AQP1(+/+) ) and knock out (AQP1(-/-) ) mice, maintained in normoxia or exposed to hypoxia while BrdU was administered. Fewer numbers of total BrdU(+) and TH-BrdU(+) cells were observed in AQP1(-/-) mice, indicating a role for AQP1 in CB proliferation. Then, by flow cytometry, cell cycle state and proliferation of cells overexpressing AQP1 were compared to those of wild-type cells. In the AQP1-overexpressing cells, we observed higher cell proliferation and percentages of cells in phases S and G2/M and fewer apoptotic cells after nocodazole treatment were detected by annexin V staining. Also in these cells, proteomic assays showed higher expression of cyclin D1 and E1 and microarray analysis revealed changes in many cell proliferation-related molecules, including, Zeb 2, Jun, NF-kβ, Cxcl9, Cxcl10, TNF, and the TNF receptor. Overall, our results indicate that the presence of AQP1 modifies the expression of key cell cycle proteins apparently related to increases in cell proliferation. This contributes to explaining the presence of AQP1 in many different tumors. PMID:26081645

  14. Sex hormones affect language lateralisation but not cognitive control in normally cycling women.

    PubMed

    Hodgetts, Sophie; Weis, Susanne; Hausmann, Markus

    2015-08-01

    This article is part of a Special Issue "Estradiol and Cognition". Natural fluctuations of sex hormones during the menstrual cycle have been shown to modulate language lateralisation. Using the dichotic listening (DL) paradigm, a well-established measurement of language lateralisation, several studies revealed that the left hemispheric language dominance was stronger when levels of estradiol were high. A recent study (Hjelmervik et al., 2012) showed, however, that high levels of follicular estradiol increased lateralisation only in a condition that required participants to cognitively control (top-down) the stimulus-driven (bottom-up) response. This finding suggested that sex hormones modulate lateralisation only if cognitive control demands are high. The present study investigated language lateralisation in 73 normally cycling women under three attention conditions that differed in cognitive control demands. Saliva estradiol and progesterone levels were determined by luminescence immunoassays. Women were allocated to a high or low estradiol group. The results showed a reduced language lateralisation when estradiol and progesterone levels were high. The effect was independent of the attention condition indicating that estradiol marginally affected cognitive control. The findings might suggest that high levels of estradiol especially reduce the stimulus-driven (bottom-up) aspect of lateralisation rather than top-down cognitive control. PMID:26145565

  15. Biogeochemical processes underpin ecosystem services

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Elemental cycling is critical to the function of ecosystems and delivery of key ecosystem services because many of these elements are essential nutrients or detrimental toxicants that directly affect the health of organisms and ecosystems. A team of authors from North Carolina State University and ...

  16. A framework to assess biogeochemical response to ecosystem disturbance using nutrient partitioning ratios

    USGS Publications Warehouse

    Kranabetter, J. Marty; McLauchlan, Kendra K.; Enders, Sara K.; Fraterrigo, Jennifer M.; Higuera, Philip E.; Morris, Jesse L.; Rastetter, Edward B.; Barnes, Rebecca; Buma, Brian; Gavin, Daniel G.; Gerhart, Laci M.; Gillson, Lindsey; Hietz, Peter; Mack, Michelle C.; McNeil, Brenden; Perakis, Steven

    2016-01-01

    Disturbances affect almost all terrestrial ecosystems, but it has been difficult to identify general principles regarding these influences. To improve our understanding of the long-term consequences of disturbance on terrestrial ecosystems, we present a conceptual framework that analyzes disturbances by their biogeochemical impacts. We posit that the ratio of soil and plant nutrient stocks in mature ecosystems represents a characteristic site property. Focusing on nitrogen (N), we hypothesize that this partitioning ratio (soil N: plant N) will undergo a predictable trajectory after disturbance. We investigate the nature of this partitioning ratio with three approaches: (1) nutrient stock data from forested ecosystems in North America, (2) a process-based ecosystem model, and (3) conceptual shifts in site nutrient availability with altered disturbance frequency. Partitioning ratios could be applied to a variety of ecosystems and successional states, allowing for improved temporal scaling of disturbance events. The generally short-term empirical evidence for recovery trajectories of nutrient stocks and partitioning ratios suggests two areas for future research. First, we need to recognize and quantify how disturbance effects can be accreting or depleting, depending on whether their net effect is to increase or decrease ecosystem nutrient stocks. Second, we need to test how altered disturbance frequencies from the present state may be constructive or destructive in their effects on biogeochemical cycling and nutrient availability. Long-term studies, with repeated sampling of soils and vegetation, will be essential in further developing this framework of biogeochemical response to disturbance.

  17. Biogeochemical modeling at mass extinction boundaries

    NASA Technical Reports Server (NTRS)

    Rampino, M. R.; Caldeira, K. G.

    1991-01-01

    The causes of major mass extinctions is a subject of considerable interest to those concerned with the history and evolution of life on earth. The primary objectives of the proposed plan of research are: (1) to develop quantitative time-dependent biogeochemical cycle models, coupled with an ocean atmosphere in order to improve the understanding of global scale physical, chemical, and biological processes that control the distribution of elements important for life at times of mass extinctions; and (2) to develop a comprehensive data base of the best available geochemical, isotopic, and other relevant geologic data from sections across mass extinction boundaries. These data will be used to constrain and test the biogeochemical model. These modeling experiments should prove useful in: (1) determining the possible cause(s) of the environmental changes seen at bio-event boundaries; (2) identifying and quantifying little-known feedbacks among the oceans, atmosphere, and biosphere; and (3) providing additional insights into the possible responses of the earth system to perturbations of various timescales. One of the best known mass extinction events marks the Cretaceous/Tertiary (K/T) boundary (66 Myr ago). Data from the K/T boundary are used here to constrain a newly developed time-dependent biogeochemical cycle model that is designed to study transient behavior of the earth system. Model results predict significant fluctuations in ocean alkalinity, atmospheric CO2, and global temperatures caused by extinction of calcareous plankton and reduction in the sedimentation rates of pelagic carbonates and organic carbon. Oxygen-isotome and other paleoclimatic data from K/T time provide some evidence that such climatic fluctuations may have occurred, but stabilizing feedbacks may have acted to reduce the ocean alkalinity and carbon dioxide fluctuations.

  18. Elevated Progesterone Levels on the Day of Oocyte Maturation May Affect Top Quality Embryo IVF Cycles

    PubMed Central

    Huang, Bo; Ren, Xinling; Wu, Li; Zhu, Lixia; Xu, Bei; Li, Yufeng; Ai, Jihui; Jin, Lei

    2016-01-01

    In contrast to the impact of elevated progesterone on endometrial receptivity, the data on whether increased progesterone levels affects the quality of embryos is still limited. This study retrospectively enrolled 4,236 fresh in vitro fertilization (IVF) cycles and sought to determine whether increased progesterone is associated with adverse outcomes with regard to top quality embryos (TQE). The results showed that the TQE rate significantly correlated with progesterone levels on the day of human chorionic gonadotropin (hCG) trigger (P = 0.009). Multivariate linear regression analysis of factors related to the TQE rate, in conventional IVF cycles, showed that the TQE rate was negatively associated with progesterone concentration on the day of hCG (OR was -1.658, 95% CI: -2.806 to -0.510, P = 0.005). When the serum progesterone level was within the interval 2.0–2.5 ng/ml, the TQE rate was significantly lower (P <0.05) than when the progesterone level was < 1.0 ng/ml; similar results were obtained for serum progesterone levels >2.5 ng/ml. Then, we choose a progesterone level at 1.5ng/ml, 2.0 ng/ml and 2.5 ng/ml as cut-off points to verify this result. We found that the TQE rate was significantly different (P <0.05) between serum progesterone levels < 2.0 ng/ml and >2.0 ng/ml. In conclusion, the results of this study clearly demonstrated a negative effect of elevated progesterone levels on the day of hCG trigger, on TQE rate, regardless of the basal FSH, the total gonadotropin, the age of the woman, or the time of ovarian stimulation. These data demonstrate that elevated progesterone levels (>2.0 ng/ml) before oocyte maturation were consistently detrimental to the oocyte. PMID:26745711

  19. A Generic Biogeochemical Module for Earth System Models: Next Generation BioGeoChemical Module (NGBGC), Version 1.0

    SciTech Connect

    Fang, Yilin; Huang, Maoyi; Liu, Chongxuan; Li, Hongyi; Leung, Lai-Yung R.

    2013-11-13

    Physical and biogeochemical processes regulate soil carbon dynamics and CO2 flux to and from atmosphere, influencing global climate changes. Integration of these processes into earth system models (e.g., community land models (CLM)), however, currently faces three major challenges: 1) extensive efforts are required to modify modeling structures and to rewrite computer programs to incorporate new or updated processes as new knowledge is being generated, 2) computational cost is prohibitively expensive to simulate biogeochemical processes in land models due to large variations in the rates of biogeochemical processes, and 3) various mathematical representations of biogeochemical processes exist to incorporate different aspects of fundamental mechanisms, but systematic evaluation of the different mathematical representations is difficult, if not possible. To address these challenges, we propose a new computational framework to easily incorporate physical and biogeochemical processes into land models. The new framework consists of a new biogeochemical module with a generic algorithm and reaction database so that new and updated processes can be incorporated into land models without the need to manually set up the ordinary differential equations to be solved numerically. The reaction database consists of processes of nutrient flow through the terrestrial ecosystems in plants, litter and soil. This framework facilitates effective comparison studies of biogeochemical cycles in an ecosystem using different conceptual models under the same land modeling framework. The approach was first implemented in CLM and benchmarked against simulations from the original CLM-CN code. A case study was then provided to demonstrate the advantages of using the new approach to incorporate a phosphorus cycle into the CLM model. To our knowledge, the phosphorus-incorporated CLM is a new model that can be used to simulate phosphorus limitation on the productivity of terrestrial ecosystems.

  20. Terrestrial biogeochemical feedbacks in the climate system

    NASA Astrophysics Data System (ADS)

    Arneth, A.; Harrison, S. P.; Zaehle, S.; Tsigaridis, K.; Menon, S.; Bartlein, P. J.; Feichter, J.; Korhola, A.; Kulmala, M.; O'Donnell, D.; Schurgers, G.; Sorvari, S.; Vesala, T.

    2010-08-01

    The terrestrial biosphere is a key regulator of atmospheric chemistry and climate. During past periods of climate change, vegetation cover and interactions between the terrestrial biosphere and atmosphere changed within decades. Modern observations show a similar responsiveness of terrestrial biogeochemistry to anthropogenically forced climate change and air pollution. Although interactions between the carbon cycle and climate have been a central focus, other biogeochemical feedbacks could be as important in modulating future climate change. Total positive radiative forcings resulting from feedbacks between the terrestrial biosphere and the atmosphere are estimated to reach up to 0.9 or 1.5 W m-2 K-1 towards the end of the twenty-first century, depending on the extent to which interactions with the nitrogen cycle stimulate or limit carbon sequestration. This substantially reduces and potentially even eliminates the cooling effect owing to carbon dioxide fertilization of the terrestrial biota. The overall magnitude of the biogeochemical feedbacks could potentially be similar to that of feedbacks in the physical climate system, but there are large uncertainties in the magnitude of individual estimates and in accounting for synergies between these effects.

  1. Antecedent acute cycling exercise affects attention control: an ERP study using attention network test

    PubMed Central

    Chang, Yu-Kai; Pesce, Caterina; Chiang, Yi-Te; Kuo, Cheng-Yuh; Fong, Dong-Yang

    2015-01-01

    The purpose of this study was to investigate the after-effects of an acute bout of moderate intensity aerobic cycling exercise on neuroelectric and behavioral indices of efficiency of three attentional networks: alerting, orienting, and executive (conflict) control. Thirty young, highly fit amateur basketball players performed a multifunctional attentional reaction time task, the attention network test (ANT), with a two-group randomized experimental design after an acute bout of moderate intensity spinning wheel exercise or without antecedent exercise. The ANT combined warning signals prior to targets, spatial cueing of potential target locations and target stimuli surrounded by congruent or incongruent flankers, which were provided to assess three attentional networks. Event-related brain potentials and task performance were measured during the ANT. Exercise resulted in a larger P3 amplitude in the alerting and executive control subtasks across frontal, central and parietal midline sites that was paralleled by an enhanced reaction speed only on trials with incongruent flankers of the executive control network. The P3 latency and response accuracy were not affected by exercise. These findings suggest that after spinning, more resources are allocated to task-relevant stimuli in tasks that rely on the alerting and executive control networks. However, the improvement in performance was observed in only the executively challenging conflict condition, suggesting that whether the brain resources that are rendered available immediately after acute exercise translate into better attention performance depends on the cognitive task complexity. PMID:25914634

  2. Influence of rapid thermal cycles in multipass welding on heat-affected-zone properties in ferritic cryogenic steels

    SciTech Connect

    Kim, H.J.; Shin, H.K.; Morris, J.W. Jr.

    1982-05-01

    The results of both welding and weld simulation studies on 2BT-treated 9Ni steel show that multiple rapid thermal cycles have a very beneficial effect on heat-affected zone toughness at cryogenic temperatures. The metallurgical sources of toughness are, however, different from those in the furnace-treated base plate. The rapidly cycled material contains no detectable austenite phase. The alloy is grain-refined by the rapid thermal cycle, and the matrix carbon content is relieved by the formation of interlathcementite precipitates which do not destroy toughness.

  3. Incorporating nitrogen fixing cyanobacteria in the global biogeochemical model HAMOCC

    NASA Astrophysics Data System (ADS)

    Paulsen, Hanna; Ilyina, Tatiana; Six, Katharina

    2015-04-01

    Nitrogen fixation by marine diazotrophs plays a fundamental role in the oceanic nitrogen and carbon cycle as it provides a major source of 'new' nitrogen to the euphotic zone that supports biological carbon export and sequestration. Since most global biogeochemical models include nitrogen fixation only diagnostically, they are not able to capture its spatial pattern sufficiently. Here we present the incorporation of an explicit, dynamic representation of diazotrophic cyanobacteria and the corresponding nitrogen fixation in the global ocean biogeochemical model HAMOCC (Hamburg Ocean Carbon Cycle model), which is part of the Max Planck Institute for Meteorology Earth system model (MPI-ESM). The parameterization of the diazotrophic growth is thereby based on available knowledge about the cyanobacterium Trichodesmium spp., which is considered as the most significant pelagic nitrogen fixer. Evaluation against observations shows that the model successfully reproduces the main spatial distribution of cyanobacteria and nitrogen fixation, covering large parts of the tropical and subtropical oceans. Besides the role of cyanobacteria in marine biogeochemical cycles, their capacity to form extensive surface blooms induces a number of bio-physical feedback mechanisms in the Earth system. The processes driving these interactions, which are related to the alteration of heat absorption, surface albedo and momentum input by wind, are incorporated in the biogeochemical and physical model of the MPI-ESM in order to investigate their impacts on a global scale. First preliminary results will be shown.

  4. Factors affecting life cycle assessment of milk produced on 6 Mediterranean buffalo farms.

    PubMed

    Pirlo, G; Carè, S; Fantin, V; Falconi, F; Buttol, P; Terzano, G M; Masoni, P; Pacelli, C

    2014-10-01

    This study quantifies the environmental impact of milk production of Italian Mediterranean buffaloes and points out the farm characteristics that mainly affect their environmental performance. Life cycle assessment was applied in a sample of 6 farms. The functional unit was 1 kg of normalized buffalo milk (LBN), with a reference milk fat and protein content of 8.3 and 4.73%, respectively. The system boundaries included the agricultural phase of the buffalo milk chain from cradle to farm gate. An economic criterion was adopted to allocate the impacts on milk production. Impact categories investigated were global warming (GW), abiotic depletion (AD), photochemical ozone formation (PO), acidification (AC), and eutrophication (EU). The contribution to the total results of the following farm activities were investigated: (1) on-farm energy consumption, (2) manure management, (3) manure application, (4) on-farm feed production (comprising production and application of chemical fertilizers and pesticides), (5) purchased feed production, (6) enteric fermentation, and (7) transport of purchased feeds, chemical fertilizers, and pesticides from producers to farms. Global warming associated with 1 kg of LBN resulted in 5.07 kg of CO₂ Eq [coefficient of variation (CV)=21.9%], AD was 3.5 × 10(-3) kg of Sb Eq (CV=51.7%), PO was 6.8 × 10(-4) kg of C₂H₄ Eq (CV=28.8%), AC was 6.5 × 10(-2) kg of SO₂ Eq (CV=30.3%), and EU was 3.3 × 10(-2) kg of PO₄(3-) Eq (CV=36.5%). The contribution of enteric fermentation and manure application to GW is 37 and 20%, respectively; on-farm consumption, on-farm feed production, and purchased feed production are the main contributors to AD; about 70% of PO is due to enteric fermentation; manure management and manure application are responsible for 55 and 25% of AC and 25 and 55% of EU, respectively. Methane and N₂O are responsible for 44 and 43% of GW, respectively. Crude oil consumption is responsible for about 72% of AD; contribution of

  5. Ecosystem Consequences of Forest Fragmentation in the Pacific Northwest: Biogeochemical Edge Effects within Old-Growth Forest Remnants

    NASA Astrophysics Data System (ADS)

    Hayes, T. D.; Swanson, A.; D'Antonio, C. M.; Griffiths, R. P.

    2005-12-01

    Our research includes quantifying the long term impact of clear-cut edges on biogeochemical processes affecting carbon and nitrogen retention within fragmented old-growth Douglas-fir/western hemlock forests in the Pacific Northwest. In addition to quantifying the magnitude and depth of influence of edge effects on soil processes, this research seeks broader application to conservation biology, using a mechanistic approach. Along 360-m gradients spanning clear-cut to forest at nine sites, long-term monitoring of edge effects integrates microclimate, above-ground structure, litter fall, decomposition, and soil nitrogen dynamics. Abrupt changes in height and structure at edges induce increased microclimatic variability in adjacent forest, which, in turn, alters rates of nitrogen and carbon cycling in soils. Field and laboratory assays reveal increases in litter decomposition and nitrogen availability in near edge (0-30 m from edge) forest, and higher rates of litter fall and soil organic matter storage within far edge (30-120 m from edge) forest, relative to interior forest (more than 120 m from edge). Abiotic structural effects, by modulating microclimatic variability, change the complex biotic interactions involved in biogeochemical cycling in forest soils within 120 m of edges. Due to such interactions, organic-matter and nitrogen pool sizes in soil and vegetation, and net ecosystem production, vary in a nonlinear, but predictable, manner with distance into forest from edge. Mixed-effects statistical models most precisely quantify depth of influence for over 100 microclimatic, structural, and biogeochemical variables.

  6. Ecosystem biogeochemical function and services in an urbanizing desert region

    NASA Astrophysics Data System (ADS)

    Grimm, N. B.; Cook, E. M.; Earl, S.; Hale, R. L.; Hall, S. J.; Hartnett, H. E.; Iwaniec, D.; Larson, E. K.; McHale, M.; Sponseller, R. A.

    2009-12-01

    Ecosystem services derive from underlying ecosystem processes but are distinguished by their benefits to society. Among ecosystem services, those associated with biogeochemical cycling and regulation of water, air, and soil quality are relatively unrecognized by the public, although concentrations of some materials are regulated by local, state and national laws. The disconnection between their importance and the degree to which these services are acknowledged means that biogeochemical ecosystem services have seldom been considered in urban planning and design. Drawing from research at multiple scales in the central Arizona region that includes over twenty cities and towns comprising metropolitan Phoenix, we illustrate the relationships between ecosystem functions and services in three areas. First, at household to whole-city scales, we show that the overriding influence of water and material inputs mediated by humans is changing biogeochemical patterns in soil and vegetation. Second, we show how human modification of aquatic ecosystems for water delivery, stormwater management, and wastewater removal give rise to important trade-offs among these services. And finally, we illustrate the limited capacity of surrounding unproductive desert ecosystems to assimilate the air pollutants generated by this region of >4 million inhabitants. We argue that urban planning and design that take into account the ecosystem functions underlying biogeochemical ecosystem services will be most effective in management of potential pollution problems associated with all of these cases. This paper thus highlights biogeochemical research conducted at the central Arizona-Phoenix LTER within a framework of ecosystem services.

  7. Biological soil crusts emit large amounts of NO and HONO affecting the nitrogen cycle in drylands

    NASA Astrophysics Data System (ADS)

    Tamm, Alexandra; Wu, Dianming; Ruckteschler, Nina; Rodríguez-Caballero, Emilio; Steinkamp, Jörg; Meusel, Hannah; Elbert, Wolfgang; Behrendt, Thomas; Sörgel, Matthias; Cheng, Yafang; Crutzen, Paul J.; Su, Hang; Pöschl, Ulrich; Weber, Bettina

    2016-04-01

    to the latest IPCC report. In summary, our measurements show that dryland emissions of nitrogen oxides are largely driven by biocrusts and not by the underlying soil. As precipitation patterns, which influence biocrust activity, are affected by climate change, alterations in global nitrogen oxide emissions are to be expected. Thus, the role of biocrusts in the global cycling of reactive nitrogen needs to be followed and also implemented in regional and global models of biogeochemistry, air chemistry and climate.

  8. Biological soil crusts emit large amounts of NO and HONO affecting the nitrogen cycle in drylands

    NASA Astrophysics Data System (ADS)

    Tamm, Alexandra; Wu, Dianming; Ruckteschler, Nina; Rodríguez-Caballero, Emilio; Steinkamp, Jörg; Meusel, Hannah; Elbert, Wolfgang; Behrendt, Thomas; Sörgel, Matthias; Cheng, Yafang; Crutzen, Paul J.; Su, Hang; Pöschl, Ulrich; Weber, Bettina

    2016-04-01

    according to the latest IPCC report. In summary, our measurements show that dryland emissions of nitrogen oxides are largely driven by biocrusts and not by the underlying soil. As precipitation patterns, which influence biocrust activity, are affected by climate change, alterations in global nitrogen oxide emissions are to be expected. Thus, the role of biocrusts in the global cycling of reactive nitrogen needs to be followed and also implemented in regional and global models of biogeochemistry, air chemistry and climate.

  9. Transcriptional modulator ZBED6 affects cell cycle and growth of human colorectal cancer cells

    PubMed Central

    Akhtar Ali, Muhammad; Younis, Shady; Wallerman, Ola; Gupta, Rajesh; Andersson, Leif; Sjöblom, Tobias

    2015-01-01

    The transcription factor ZBED6 (zinc finger, BED-type containing 6) is a repressor of IGF2 whose action impacts development, cell proliferation, and growth in placental mammals. In human colorectal cancers, IGF2 overexpression is mutually exclusive with somatic mutations in PI3K signaling components, providing genetic evidence for a role in the PI3K pathway. To understand the role of ZBED6 in tumorigenesis, we engineered and validated somatic cell ZBED6 knock-outs in the human colorectal cancer cell lines RKO and HCT116. Ablation of ZBED6 affected the cell cycle and led to increased growth rate in RKO cells but reduced growth in HCT116 cells. This striking difference was reflected in the transcriptome analyses, which revealed enrichment of cell-cycle–related processes among differentially expressed genes in both cell lines, but the direction of change often differed between the cell lines. ChIP sequencing analyses displayed enrichment of ZBED6 binding at genes up-regulated in ZBED6-knockout clones, consistent with the view that ZBED6 modulates gene expression primarily by repressing transcription. Ten differentially expressed genes were identified as putative direct gene targets, and their down-regulation by ZBED6 was validated experimentally. Eight of these genes were linked to the Wnt, Hippo, TGF-β, EGF receptor, or PI3K pathways, all involved in colorectal cancer development. The results of this study show that the effect of ZBED6 on tumor development depends on the genetic background and the transcriptional state of its target genes. PMID:26056301

  10. A Coupled Land Surface-Subsurface Biogeochemical Model for Aqueous and Gaseous Nitrogen Losses

    NASA Astrophysics Data System (ADS)

    Gu, C.; Maggi, F.; Riley, W.; Pan, L.; Xu, T.; Oldenburg, C.; Miller, N.

    2008-12-01

    In recent years concern has grown over the contribution of nitrogen (N) fertilizers to nitrate (NOB3PB-P) water pollution and atmospheric pollution of nitrous oxide (NB2BO), nitric oxide (NO), and ammonia (NHB3B). Characterizing the amount and species of N losses is therefore essential in developing a strategy to estimate and mitigate N leaching and emission to the atmosphere. Indeed, transformations of nitrogen depend strongly on water content, soil temperature, and nitrogen concentration. Land surface processes therefore have to be taken into account to properly characterize N biogeochemical cycling. However, most current nitrogen biogeochemical models take the land surface as the upper boundary by lumping the complex processes above the surface as known boundary conditions. In this study, an extant subsurface mechanistic N cycle model (TOUGHREACT-N) was coupled with the community land model (CLM). The resulting coupled model extends the modeling capability of TOUGHREACT-N to include the important energy, momentum, and moisture dynamics provided by CLM. The coupled model showed a significant impact of land-surface diurnal forcing on soil temperature and moisture and on nitrogen fluxes. We also discuss field applications of the model and discuss how temporal dynamics of nitrogen fluxes are affected by land surface processes.

  11. How inhibiting nitrification affects nitrogen cycle and reduces environmental impacts of anthropogenic nitrogen input.

    PubMed

    Qiao, Chunlian; Liu, Lingli; Hu, Shuijin; Compton, Jana E; Greaver, Tara L; Li, Quanlin

    2015-03-01

    Anthropogenic activities, and in particular the use of synthetic nitrogen (N) fertilizer, have doubled global annual reactive N inputs in the past 50-100 years, causing deleterious effects on the environment through increased N leaching and nitrous oxide (N2 O) and ammonia (NH3 ) emissions. Leaching and gaseous losses of N are greatly controlled by the net rate of microbial nitrification. Extensive experiments have been conducted to develop ways to inhibit this process through use of nitrification inhibitors (NI) in combination with fertilizers. Yet, no study has comprehensively assessed how inhibiting nitrification affects both hydrologic and gaseous losses of N and plant nitrogen use efficiency. We synthesized the results of 62 NI field studies and evaluated how NI application altered N cycle and ecosystem services in N-enriched systems. Our results showed that inhibiting nitrification by NI application increased NH3 emission (mean: 20%, 95% confidential interval: 33-67%), but reduced dissolved inorganic N leaching (-48%, -56% to -38%), N2 O emission (-44%, -48% to -39%) and NO emission (-24%, -38% to -8%). This amounted to a net reduction of 16.5% in the total N release to the environment. Inhibiting nitrification also increased plant N recovery (58%, 34-93%) and productivity of grain (9%, 6-13%), straw (15%, 12-18%), vegetable (5%, 0-10%) and pasture hay (14%, 8-20%). The cost and benefit analysis showed that the economic benefit of reducing N's environmental impacts offsets the cost of NI application. Applying NI along with N fertilizer could bring additional revenues of $163 ha(-1)  yr(-1) for a maize farm, equivalent to 8.95% increase in revenues. Our findings showed that NIs could create a win-win scenario that reduces the negative impact of N leaching and greenhouse gas production, while increases the agricultural output. However, NI's potential negative impacts, such as increase in NH3 emission and the risk of NI contamination, should be fully

  12. The NEON Aquatic Network: Expanding the Availability of Biogeochemical Data

    NASA Astrophysics Data System (ADS)

    Vance, J. M.; Bohall, C.; Fitzgerald, M.; Utz, R.; Parker, S. M.; Roehm, C. L.; Goodman, K. J.; McLaughlin, B.

    2013-12-01

    Aquatic ecosystems are facing unprecedented pressure from climate change and land-use practices. Invasive species, whether plant, animal, insect or microbe present additional threat to aquatic ecosystem services. There are significant scientific challenges to understanding how these forces will interact to affect aquatic ecosystems, as the flow of energy and materials in the environment is driven by multivariate and non-linear biogeochemical cycles. The National Ecological Observatory Network (NEON) will collect and provide observational data across multiple scales. Sites were selected to maximize representation of major North American ecosystems using a multivariate geographic clustering method that partitioned the continental US, AK, HI, and Puerto Rico into 20 eco-climatic domains. The NEON data collection systems and methods are designed to yield standardized, near real-time data subjected to rigorous quality controls prior to public dissemination through an online data portal. NEON will collect data for 30 years to facilitate spatial-temporal analysis of environmental responses and drivers of ecosystem change, ranging from local through continental scales. Here we present the NEON Aquatic Network, a multi-parameter network consisting of a combination of in situ sensor and observational data. This network will provide data to examine biogeochemical, biological, hydrologic and geomorphic metrics at 36 sites, which are a combination of small 1st/2nd order wadeable streams, large rivers and lakes. A typical NEON Aquatic site will host up to two in-stream sensor sets designed to collect near-continuous water quality data (e.g. pH/ORP, temperature, conductivity, dissolved oxygen, CDOM) along with up to 8 shallow groundwater monitoring wells (level, temp., cond.), and a local meteorological station (e.g. 2D wind speed, PAR, barometric pressure, temperature, net radiation). These coupled sensor suites will be complemented by observational data (e.g. water

  13. The repeated drying-wetting and freezing-thawing cycles affect only the active pool of soil organic matter

    NASA Astrophysics Data System (ADS)

    Semenov, Vyacheslav; Zinyakova, Natalya; Tulina, Anastasiya

    2016-04-01

    The decrease in the content of soil organic carbon, particularly in active form, is one of the major problems of the 21st century, which is closely related to the disturbance of the biogeochemical carbon cycle and to the increase in the emission of carbon dioxide into the atmosphere. The main reasons for the SOM losses are the surplus of the SOM active pool losses due to mineralization, erosion, and infiltration over the input of fresh organic matter to the soil, as well as the changes in the soil conditions and processes due to natural and anthropogenic disturbing impacts. Experiments were carried out with mixed samples from the upper layers of soddy-podzolic soil, gray forest soil, and typical chernozems. Soil samples as controls were incubated after wetting for 150 days. The dynamics and cumulative production of C-CO2 under stable temperature (22°C) and moisture conditions were determined; the initial content of potentially mineralizable organic matter (C0) in the soil at the beginning of the incubation was then calculated to use these data as the control. Other soil samples were exposed in flasks to the following successive treatments: wetting →incubation → freezing → thawing → incubation →drying. Six repeated cycles of disturbing impacts were performed for 140 days of the experiment. After six cycles, the soil samples were incubated under stable temperature and moisture conditions for 150 days. The wetting of dried soils and the thawing of frozen soils are accompanied by the pulsed dynamics of the C-CO2 production with an abrupt increase in the rate of the C-CO2 emission within several days by 2.7-12.4 and 1.6-2.7 times, respectively, compared to the stable incubation conditions. The rate of the C-CO2 production pulses under each subsequent impact decreased compared to the preceding one similarly for all studied soils, which could be due to the depletion in potentially mineralizable soil organic matter (C0). The cumulative extra C-CO2 production by

  14. Heat-affected zone thermal cycles in Inconel[reg sign] 718

    SciTech Connect

    Bowers, R.J. CANMET-MTL, Ottawa, Ontario ); Nippes, E.F. . Materials Engineering Dept.)

    1993-12-01

    Thermal cycles adjacent to autogenous welds in 1-cm (0.39-in.) IN718 plate were obtained using a computer data-acquisition system. Data from gas tungsten arc welds (GTAW) of various energy inputs were regression analyzed and tabulated for various times and distances from the centerline. The observation of grain-boundary precipitates in simulated and actual weld microstructures were used as a method of thermal-cycle verification. Application of the thermal-cycle data to the simulation of a fracture-toughness specimen was investigated. Thermal gradients across the specimen and high cooling rates were limiting factors in the microstructural simulation of a large cross-sectional-area specimen.

  15. Bax alpha perturbs T cell development and affects cell cycle entry of T cells.

    PubMed Central

    Brady, H J; Gil-Gómez, G; Kirberg, J; Berns, A J

    1996-01-01

    Bax alpha can heterodimerize with Bcl-2 and Bcl-X(L), countering their effects, as well as promoting apoptosis on overexpression. We show that bax alpha transgenic mice have greatly reduced numbers of mature T cells, which results from an impaired positive selection in the thymus. This perturbation in positive selection is accompanied by an increase in the number of cycling thymocytes. Further to this, mature T cells overexpressing Bax alpha have lower levels of p27Kip1 and enter S phase more rapidly in response to interleukin-2 stimulation than do control T cells, while the converse is true of bcl-2 transgenic T cells. These data indicate that apoptotic regulatory proteins can modulate the level of cell cycle-controlling proteins and thereby directly impact on the cell cycle. Images PMID:9003775

  16. Microstructural changes in HSLA-100 steel thermally cycled to simulate the heat-affected zone during welding

    SciTech Connect

    Spanos, G.; Fonda, R.W.; Vandermeer, R.A.; Matuszeski, A.

    1995-12-01

    The microstructural changes that occur in a commercial HSLA-100 steel thermally cycled to simulate weld heat affected zone (HAZ) behavior were systematically investigated primarily by transmission electron microscopy (TEM). Eight different weld thermal cycles, with peak temperatures representative of four HAZ regions (the tempered region, the intercritical region, the fine-grained austenitized region, and the coarse-grained austenitized region) and cooling rates characteristic of high heat input (cooling rate (CR) = 5 C/s) and low heat input (CR = 60 C/s) welding were simulated in a heating/quenching dilatometer. The as-received base plate consisted of heavily tempered lath martensite, acicular ferrite, and retained austenite matrix phases with precipitates of copper, niobium-carbonitride, and cementite. The microstructural changes in both the matrix and precipitate phases due to thermal cycling were examined by TEM and correlated with the results of (1) conventional optical microscopy, (2) prior austenite grain size measurements, (3) microhardness testing, and (4) dilatometric analysis. Many of the thermal cycles resulted in dramatic changes in both the microstructures and the properties due to the synergistic interaction between the simulated position in the HAZ and the heat input. Some of these microstructures deviate substantially from those predicted from published continuous cooling transformation (CCT) curves. The final microstructure was predominantly dependent upon peak temperature (i.e., position within the HAZ), although the cooling rate (i.e., heat input) strongly affected the microstructures of the simulated intercritical and fine-grained austenitized regions.

  17. Biogeochemical Processes in Microbial Ecosystems

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.

    2001-01-01

    The hierarchical organization of microbial ecosystems determines process rates that shape Earth's environment, create the biomarker sedimentary and atmospheric signatures of life, and define the stage upon which major evolutionary events occurred. In order to understand how microorganisms have shaped the global environment of Earth and, potentially, other worlds, we must develop an experimental paradigm that links biogeochemical processes with ever-changing temporal and spatial distributions of microbial populations and their metabolic properties. Additional information is contained in the original extended abstract.

  18. The Impact of Continuous and Interval Cycle Exercise on Affect and Enjoyment

    ERIC Educational Resources Information Center

    Kilpatrick, Marcus W.; Greeley, Samuel J.; Collins, Larry H.

    2015-01-01

    Rates of physical activity remain low despite public health efforts. One form of physical activity that provides significant physiological benefit but has not been evaluated in terms of affective and enjoyment responses is interval exercise. Purpose: The purpose of this study was to compare affect and enjoyment assessed before, during, and after…

  19. How Business Cycles Affect the Healthcare Sector: A Cross-country Investigation.

    PubMed

    Cleeren, Kathleen; Lamey, Lien; Meyer, Jan-Hinrich; De Ruyter, Ko

    2016-07-01

    The long-term relationship between the general economy and healthcare expenditures has been extensively researched, to explain differences in healthcare spending between countries, but the midterm (i.e., business cycle) perspective has been overlooked. This study explores business cycle sensitivity in both public and private parts of the healthcare sector across 32 countries. Responses to the business cycle vary notably, both across spending sources and across countries. Whereas in some countries, consumers and/or governments cut back, in others, private and/or public healthcare buyers tend to spend more. We also assess long-term consequences of business cycle sensitivity and show that public cost cutting during economic downturns deflates the mortality rates, whereas private cut backs increase the long-term growth in total healthcare expenditures. Finally, multiple factors help explain variability in cyclical sensitivity. Private cost cuts during economic downturns are smaller in countries with a predominantly publicly funded healthcare system and more preventive public activities. Public cut backs during contractions are smaller in countries that rely more on tax-based resources rather than social health insurances. Copyright © 2015 John Wiley & Sons, Ltd. PMID:25916435

  20. Menstrual-cycle dependent fluctuations in ovarian hormones affect emotional memory.

    PubMed

    Bayer, Janine; Schultz, Heidrun; Gamer, Matthias; Sommer, Tobias

    2014-04-01

    The hormones progesterone and estradiol modulate neural plasticity in the hippocampus, the amygdala and the prefrontal cortex. These structures are involved in the superior memory for emotionally arousing information (EEM effects). Therefore, fluctuations in hormonal levels across the menstrual cycle are expected to influence activity in these areas as well as behavioral memory performance for emotionally arousing events. To test this hypothesis, naturally cycling women underwent functional magnetic resonance imaging during the encoding of emotional and neutral stimuli in the low-hormone early follicular and the high-hormone luteal phase. Their memory was tested after an interval of 48 h, because emotional arousal primarily enhances the consolidation of new memories. Whereas overall recognition accuracy remained stable across cycle phases, recognition quality varied with menstrual cycle phases. Particularly recollection-based recognition memory for negative items tended to decrease from early follicular to luteal phase. EEM effects for both valences were associated with higher activity in the right anterior hippocampus during early follicular compared to luteal phase. Valence-specific modulations were found in the anterior cingulate, the amygdala and the posterior hippocampus. Current findings connect to anxiolytic actions of estradiol and progesterone as well as to studies on fear conditioning. Moreover, they are in line with differential networks involved in EEM effects for positive and negative items. PMID:24492058

  1. Factors affecting cycle life in ambient temperature of secondary lithium batteries

    NASA Technical Reports Server (NTRS)

    Somoano, R.

    1982-01-01

    Three major factors are discussed: electrode integrity, electrolyte stability, and dendrite formation. It is concluded that elastomers can function as improved binders for rechargeable cathodes. The cathodes can retain integrity under long cycle life with no visual deteriorations. It is found that microelectrodes can be made from powdery cathode materials for voltammetry studies.

  2. Marine viruses and their biogeochemical and ecological effects

    NASA Astrophysics Data System (ADS)

    Fuhrman, Jed A.

    1999-06-01

    Viruses are the most common biological agents in the sea, typically numbering ten billion per litre. They probably infect all organisms, can undergo rapid decay and replenishment, and influence many biogeochemical and ecological processes, including nutrient cycling, system respiration, particle size-distributions and sinking rates, bacterial and algal biodiversity and species distributions, algal bloom control, dimethyl sulphide formation and genetic transfer. Newly developed fluorescence and molecular techniques leave the field poised to make significant advances towards evaluating and quantifying such effects.

  3. How inhibiting nitrification affects nitrogen cycle and reduces environmental impacts of anthropogenic nitrogen input

    EPA Science Inventory

    We conducted a meta-analysis of 103 nitrification inhibitor (NI) studies, and evaluated how NI application affects crop productivity and other ecosystem services in agricultural systems. Our results showed that, compared to conventional fertilizer practice, applications of NI alo...

  4. A Deregulated Intestinal Cell Cycle Program Disrupts Tissue Homeostasis without Affecting Longevity in Drosophila*

    PubMed Central

    Petkau, Kristina; Parsons, Brendon D.; Duggal, Aashna; Foley, Edan

    2014-01-01

    Recent studies illuminate a complex relationship between the control of stem cell division and intestinal tissue organization in the model system Drosophila melanogaster. Host and microbial signals drive intestinal proliferation to maintain an effective epithelial barrier. Although it is widely assumed that proliferation induces dysplasia and shortens the life span of the host, the phenotypic consequences of deregulated intestinal proliferation for an otherwise healthy host remain unexplored. To address this question, we genetically isolated and manipulated the cell cycle programs of adult stem cells and enterocytes. Our studies revealed that cell cycle alterations led to extensive cell death and morphological disruptions. Despite the extensive tissue damage, we did not observe an impact on longevity, suggesting a remarkable degree of plasticity in intestinal function. PMID:25170078

  5. A deregulated intestinal cell cycle program disrupts tissue homeostasis without affecting longevity in Drosophila.

    PubMed

    Petkau, Kristina; Parsons, Brendon D; Duggal, Aashna; Foley, Edan

    2014-10-10

    Recent studies illuminate a complex relationship between the control of stem cell division and intestinal tissue organization in the model system Drosophila melanogaster. Host and microbial signals drive intestinal proliferation to maintain an effective epithelial barrier. Although it is widely assumed that proliferation induces dysplasia and shortens the life span of the host, the phenotypic consequences of deregulated intestinal proliferation for an otherwise healthy host remain unexplored. To address this question, we genetically isolated and manipulated the cell cycle programs of adult stem cells and enterocytes. Our studies revealed that cell cycle alterations led to extensive cell death and morphological disruptions. Despite the extensive tissue damage, we did not observe an impact on longevity, suggesting a remarkable degree of plasticity in intestinal function. PMID:25170078

  6. Is the Stratospheric QBO affected by Solar Wind Dynamic Pressure via an Annual Cycle Modulation?

    NASA Astrophysics Data System (ADS)

    Lu, H.; Jarvis, M. J.

    2010-12-01

    This study explores possible solar wind dynamic pressure effects on equatorial temperature and wind with an emphasis on the stratospheric Quasi-biennial Oscillation (QBO). The QBO phase occurrence and transition are closely linked to an annual cycle of tropical lower stratospheric temperature. The statistical response of the tropical temperature to solar wind dynamic pressure is characterized by ~1.25 K warming near the tropopause during the Boreal winter and spring and ~ 0.5 K cooling in the troposphere during the Austral winter and spring. The combined effect of this is a reduction of the amplitude of the annual cycle in temperature in the tropical tropopause region. The weakening of the annual cycle causes systematic and significant change in the tropical upwelling and therefore the strength and phase distribution of the QBO in the lower stratosphere. In the lower stratosphere, significantly stronger and more frequency easterly anomalies are found to be associated with high solar wind dynamic pressure during August to October. In addition to the seasonal response, there is a small but seasonally invariant response that is characterized by a vertical three-cell anomaly pattern with westerly anomalies in the troposphere and at 3-10 hPa and easterly anomalies in the lower stratosphere. We propose that significantly stronger easterly anomalies in the tropical lower stratosphere under high solar wind dynamic pressure during the Austral winter and spring are a consequence both of the initializing effect of this three-cell structure and of an amplification effect due to the seasonal modulation of the annual cycle.

  7. Large nuclear vacuoles in spermatozoa negatively affect pregnancy rate in IVF cycles

    PubMed Central

    Ghazali, Shahin; Talebi, Ali Reza; Khalili, Mohammad Ali; Aflatoonian, Abbas; Esfandiari, Navid

    2015-01-01

    Background: Recently, motile sperm organelle morphology examination (MSOME) criteria as a new real time tool for evaluation of spermatozoa in intracytoplasmic sperm injection (ICSI) cycles has been considered. Objective: The aim was to investigate the predictive value of MSOME in in vitro fertilization (IVF) in comparison to ICSI cycles and evaluation of the association between MSOME parameters and traditional sperm parameters in both groups. Materials and Methods: This is a cross sectional prospective analysis of MSOME parameters in IVF (n=31) and ICSI cycles (n=35). MSOME parameters were also evaluated as the presence of vacuole (none, small, medium, large or mix); head size (normal, small or large); cytoplasmic droplet; head shape and acrosome normality. In sub-analysis, MSOME parameters were compared between two groups with successful or failed clinical pregnancy in each group. Results: In IVF group, the rate of large nuclear vacuole showed significant increase in failed as compared to successful pregnancies (13.81±9.7vs7.38±4.4, respectively, p=0.045) while MSOME parameters were the same between successful and failed pregnancies in ICSI group. Moreover, a negative correlation was noticed between LNV and sperm shape normalcy. In ICSI group, a negative correlation was established between cytoplasmic droplet and sperm shape normalcy. In addition, there was a positive correlation between sperm shape normalcy and non-vacuolated spermatozoa. Conclusion: The high rate of large nuclear vacuoles in sperm used in IVF cycles with failed pregnancies confirms that MSOME, is a helpful tool for fine sperm morphology assessment, and its application may enhance the assisted reproduction technology success rates. PMID:26494990

  8. Biochar affects soil organic matter cycling and microbial functions but does not alter microbial community structure in a paddy soil.

    PubMed

    Tian, Jing; Wang, Jingyuan; Dippold, Michaela; Gao, Yang; Blagodatskaya, Evgenia; Kuzyakov, Yakov

    2016-06-15

    The application of biochar (BC) in conjunction with mineral fertilizers is one of the most promising management practices recommended to improve soil quality. However, the interactive mechanisms of BC and mineral fertilizer addition affecting microbial communities and functions associated with soil organic matter (SOM) cycling are poorly understood. We investigated the SOM in physical and chemical fractions, microbial community structure (using phospholipid fatty acid analysis, PLFA) and functions (by analyzing enzymes involved in C and N cycling and Biolog) in a 6-year field experiment with BC and NPK amendment. BC application increased total soil C and particulate organic C for 47.4-50.4% and 63.7-74.6%, respectively. The effects of BC on the microbial community and C-cycling enzymes were dependent on fertilization. Addition of BC alone did not change the microbial community compared with the control, but altered the microbial community structure in conjunction with NPK fertilization. SOM fractions accounted for 55% of the variance in the PLFA-related microbial community structure. The particulate organic N explained the largest variation in the microbial community structure. Microbial metabolic activity strongly increased after BC addition, particularly the utilization of amino acids and amines due to an increase in the activity of proteolytic (l-leucine aminopeptidase) enzymes. These results indicate that microorganisms start to mine N from the SOM to compensate for high C:N ratios after BC application, which consequently accelerate cycling of stable N. Concluding, BC in combination with NPK fertilizer application strongly affected microbial community composition and functions, which consequently influenced SOM cycling. PMID:26974565

  9. PKA-mediated responses in females' estrous cycle affect cocaine-induced responses in dopamine-mediated intracellular cascades.

    PubMed

    Weiner, J; Sun, W Lun; Zhou, L; Kreiter, C M; Jenab, S; Quiñones-Jenab, V

    2009-07-01

    An extensive body of literature provides evidence for both sexual dimorphism and menstrual cycle effects in drug abuse patterns and behavioral responses. However, the cellular mechanisms underlying sexually dimorphic responses to and hormonal effects on cocaine use remain unclear. We hypothesized that endogenous hormonal fluctuations during the estrous cycle of rats modulate cocaine's effects on dopamine- and PKA-mediated intracellular responses. To test this hypothesis, intact female rats at different stages of their cycle received a single injection of saline or cocaine (20 mg/kg) and were sacrificed after 15 or 60 min. The nucleus accumbens (NAc) and caudate putamen (CPu) were dissected and analyzed via Western blot for total and phosphorylated (p-thr34) dopamine- and 3'-5'-cyclic AMP-regulated phosphoprotein with molecular weight 32 kDa (DARPP-32), PP1, PP2B (CNA1 and CNB1 subunits), PKA, CREB, cFOS, and Delta-FosB. Our results show that saline-treated rats had estrous cycle-related differences in protein levels of pCREB, DARPP-32, p-thr34-DARPP-32, PP1, and CNA1. Saline-treated female rats in the estrus stage had higher levels of pCREB in the NAc, but cocaine-treatment lowered pCREB levels. The estrous cycle also significantly affected the magnitude of change for p-thr34-DARPP-32 protein levels in both the NAc and CPu. Sixty minutes of cocaine administration increased p-thr34-DARPP-32 levels in the NAc of rats during estrus and proestrus and in the CPu of rats in diestrus. Furthermore, cocaine-induced changes in PP1 protein levels in the NAc were also affected by the stage of the cycle; 60 min of cocaine administration increased PP1 levels in the NAc of rats during diestrus, whereas PP-1 levels decreased in rats during estrus. Taken together, these novel findings suggest that hormonal fluctuations during the estrous cycle may contribute to the previously reported sex differences in the PKA pathway and in behavioral responses to cocaine. PMID:19348873

  10. The relationship between sleep-wake cycle and cognitive functioning in young people with affective disorders.

    PubMed

    Carpenter, Joanne S; Robillard, Rébecca; Lee, Rico S C; Hermens, Daniel F; Naismith, Sharon L; White, Django; Whitwell, Bradley; Scott, Elizabeth M; Hickie, Ian B

    2015-01-01

    Although early-stage affective disorders are associated with both cognitive dysfunction and sleep-wake disruptions, relationships between these factors have not been specifically examined in young adults. Sleep and circadian rhythm disturbances in those with affective disorders are considerably heterogeneous, and may not relate to cognitive dysfunction in a simple linear fashion. This study aimed to characterise profiles of sleep and circadian disturbance in young people with affective disorders and examine associations between these profiles and cognitive performance. Actigraphy monitoring was completed in 152 young people (16-30 years; 66% female) with primary diagnoses of affective disorders, and 69 healthy controls (18-30 years; 57% female). Patients also underwent detailed neuropsychological assessment. Actigraphy data were processed to estimate both sleep and circadian parameters. Overall neuropsychological performance in patients was poor on tasks relating to mental flexibility and visual memory. Two hierarchical cluster analyses identified three distinct patient groups based on sleep variables and three based on circadian variables. Sleep clusters included a 'long sleep' cluster, a 'disrupted sleep' cluster, and a 'delayed and disrupted sleep' cluster. Circadian clusters included a 'strong circadian' cluster, a 'weak circadian' cluster, and a 'delayed circadian' cluster. Medication use differed between clusters. The 'long sleep' cluster displayed significantly worse visual memory performance compared to the 'disrupted sleep' cluster. No other cognitive functions differed between clusters. These results highlight the heterogeneity of sleep and circadian profiles in young people with affective disorders, and provide preliminary evidence in support of a relationship between sleep and visual memory, which may be mediated by use of antipsychotic medication. These findings have implications for the personalisation of treatments and improvement of functioning in

  11. The Relationship between Sleep-Wake Cycle and Cognitive Functioning in Young People with Affective Disorders

    PubMed Central

    Carpenter, Joanne S.; Robillard, Rébecca; Lee, Rico S. C.; Hermens, Daniel F.; Naismith, Sharon L.; White, Django; Whitwell, Bradley; Scott, Elizabeth M.; Hickie, Ian B.

    2015-01-01

    Although early-stage affective disorders are associated with both cognitive dysfunction and sleep-wake disruptions, relationships between these factors have not been specifically examined in young adults. Sleep and circadian rhythm disturbances in those with affective disorders are considerably heterogeneous, and may not relate to cognitive dysfunction in a simple linear fashion. This study aimed to characterise profiles of sleep and circadian disturbance in young people with affective disorders and examine associations between these profiles and cognitive performance. Actigraphy monitoring was completed in 152 young people (16–30 years; 66% female) with primary diagnoses of affective disorders, and 69 healthy controls (18–30 years; 57% female). Patients also underwent detailed neuropsychological assessment. Actigraphy data were processed to estimate both sleep and circadian parameters. Overall neuropsychological performance in patients was poor on tasks relating to mental flexibility and visual memory. Two hierarchical cluster analyses identified three distinct patient groups based on sleep variables and three based on circadian variables. Sleep clusters included a ‘long sleep’ cluster, a ‘disrupted sleep’ cluster, and a ‘delayed and disrupted sleep’ cluster. Circadian clusters included a ‘strong circadian’ cluster, a ‘weak circadian’ cluster, and a ‘delayed circadian’ cluster. Medication use differed between clusters. The ‘long sleep’ cluster displayed significantly worse visual memory performance compared to the ‘disrupted sleep’ cluster. No other cognitive functions differed between clusters. These results highlight the heterogeneity of sleep and circadian profiles in young people with affective disorders, and provide preliminary evidence in support of a relationship between sleep and visual memory, which may be mediated by use of antipsychotic medication. These findings have implications for the personalisation of treatments

  12. Factors Affecting the Pathways of Glucose Catabolism and the Tricarboxylic Acid Cycle in Pseudomonas natriegens

    PubMed Central

    Cho, H. W.; Eagon, R. G.

    1967-01-01

    Less than 50% of theoretical oxygen uptake was observed when glucose was dissimilated by resting cells of Pseudomonas natriegens. Low oxygen uptakes were also observed when a variety of other substrates were dissimilated. When uniformly labeled glucose-14C was used as substrate, 56% of the label was shown to accumulate in these resting cells. This material consisted, in part, of a polysaccharide which, although it did not give typical glycogen reactions, yielded glucose after its hydrolysis. Resting cells previously cultivated on media containing glucose completely catabolized glucose and formed a large amount of pyruvate within 30 min. Resting cells cultivated in the absence of glucose catabolized glucose more slowly and produced little pyruvate. Pyruvate disappeared after further incubation. In this latter case, experimental results suggested (i) that pyruvate was converted to other acidic products (e.g., acetate and lactate) and (ii) that pyruvate was further catabolized via the tricarboxylic acid cycle. Growth on glucose repressed the level of key enzymes of the tricarboxylic acid cycle and of lactic dehydrogenase. Growth on glycerol stimulated the level of these enzymes. A low level of isocitratase, but not malate synthetase, was noted in extracts of glucose-grown cells. Isocitric dehydrogenase was shown to require nicotinamide adenine dinucleotide phosphate (NADP) as cofactor. Previous experiments have shown that reduced NADP (NADPH2) cannot be readily oxidized and that pyridine nucleotide transhydrogenase could not be detected in extracts. It was concluded that acetate, lactate, and pyruvate accumulate under growing conditions when P. natriegens is cultivated on glucose (i) because of a rapid initial catabolism of glucose via an aerobic glycolytic pathway and (ii) because of a sluggishly functioning tricarboxylic acid cycle due to the accumulation of NADPH2 and to repressed levels of key enzymes. PMID:4381634

  13. The biogeochemical reactivity of suspended particulate matter at nested sites in the Dee basin, NE Scotland.

    PubMed

    Dawson, J J C; Adhikari, Y R; Soulsby, C; Stutter, M I

    2012-09-15

    Variation in the organic matter content associated with suspended particulate matter (SPM) is an often overlooked component of carbon cycling within freshwater riverine systems. The potential biogeochemical reactivity of particulate organic carbon (POC) that affect its interactions and fate, i.e. respired and lost to the atmosphere along river continua or ultimately exported to estuarine and oceanic pools was assessed. Eleven contrasting sites draining nested catchments (5-1837 km(2)) in the River Dee basin, NE Scotland were sampled during summer 2008 to evaluate spatio-temporal variations in quantity and quality (biogeochemical reactivity) of SPM during relatively low flow conditions. Mean SPM concentrations increased from 0.21 to 1.22 mg L(-1) between the uppermost and lowest mainstem sites. Individually, POC concentrations ranged from 0.08 to 0.55 mg L(-1) and accounted for ca. 3-15% of total aqueous organic carbon transported. The POC content was partitioned into autotrophic (2.78-73.0 mg C g(-1) SPM) and detrital (119-388 mg C g(-1) SPM) biomass carbon content. The particulate respired CO(2)-C as a % of the total carbon associated with SPM, measured by MicroResp™ over 18 h, varied in recalcitrance from 0.49% at peat-dominated sites to 3.20% at the lowermost mainstem site. Significant (p<0.05) relationships were observed between SPM biogeochemical reactivity measures (% respired CO(2)-C; chlorophyll α; bioavailable-phosphorus) and arable and improved grassland area, associated with increasing biological productivity downstream. Compositional characteristics and in-stream processing of SPM appear to be related to contributory land use pressures, that influence SPM characteristics and biogeochemistry (C:N:P stoichiometry) of its surrounding aqueous environment. As moorland influences declined, nutrient inputs from arable and improved grasslands increasingly affected the biogeochemical content and reactivity of both dissolved and particulate matter. This

  14. Understanding the Cycle of Military Deployment: How It Affects Young Children and Families

    ERIC Educational Resources Information Center

    Robertson, Rachel

    2008-01-01

    The statistics of children and families experiencing military life and affected by deployment are astounding. Many children who have an uncle, aunt, brother, or other family member serving in the military live near a military duty station, but others live far from other military families. Caregivers and teachers of young children share a common…

  15. Temperature cycling periods affect growth and tuberization in potatoes under continuous irradiation

    NASA Technical Reports Server (NTRS)

    Cao, W.; Tibbitts, T. W.

    1992-01-01

    Plants of the potato (Solanum tuberosum L.) cultivars Denali, Norland, Haig and Kennebec were grown for 42 days under three temperature cycling periods (thermoperiods) with continuous irradiation in two repeated experiments to help determine if temperature cycling might be varied to optimize tuber development of potatoes in controlled environments. Thermoperiods of 6/6 hours, 12/12 hours and 24/24 hours were established with the same temperature change of 22/14C and same controlled vapor pressure deficit of 0.60 kPa. The thermoperiod of 24/24 hours significantly promoted tuber initiation but slowed tuber enlargement in all four cultivars, compared to the thermoperiods of 6/6 hours and 12/12 hours. Denali' produced the highest tuber and total dry weights under the 6/6 hours thermoperiod. Kennebec' produced the highest tuber dry weight under the 12/12 hours thermoperiod. Thermoperiods had no significant effect on shoot and root dry weights of any cultivars. The major effect of thermoperiods was on initiation and enlargement of tubers.

  16. A coupled biogeochemical-Dynamic Energy Budget model as a tool for managing fish production ponds.

    PubMed

    Serpa, Dalila; Pousão-Ferreira, Pedro; Caetano, Miguel; Cancela da Fonseca, Luís; Dinis, Maria Teresa; Duarte, Pedro

    2013-10-01

    The sustainability of semi-intensive aquaculture relies on management practices that simultaneously improve production efficiency and minimize the environmental impacts of this activity. The purpose of the present work was to develop a mathematical model that reproduced the dynamics of a semi-intensive fish earth pond, to simulate different management scenarios for optimizing fish production. The modeling approach consisted of coupling a biogeochemical model that simulated the dynamics of the elements that are more likely to affect fish production and cause undesirable environmental impacts (nitrogen, phosphorus and oxygen) to a fish growth model based on the Dynamic Energy Budget approach. The biogeochemical sub-model successfully simulated most water column and sediment variables. A good model fit was also found between predicted and observed white seabream (Diplodus sargus) growth data over a production cycle. In order to optimize fish production, different management scenarios were analysed with the model (e.g. increase stocking densities, decrease/increase water exchange rates, decrease/increase feeding rates, decrease phosphorus content in fish feeds, increase food assimilation efficiency and decrease pellets sinking velocity) to test their effects on the pond environment as well as on fish yields and effluent nutrient discharges. Scenarios were quantitatively evaluated and compared using the Analytical Hierarchical Process (AHP) methodology. The best management options that allow the maximization of fish production while maintaining a good pond environment and minimum impacts on the adjacent coastal system were to double standard stocking densities and to improve food assimilation efficiency. PMID:23872182

  17. Biotic Interactions in Microbial Communities as Modulators of Biogeochemical Processes: Methanotrophy as a Model System

    PubMed Central

    Ho, Adrian; Angel, Roey; Veraart, Annelies J.; Daebeler, Anne; Jia, Zhongjun; Kim, Sang Yoon; Kerckhof, Frederiek-Maarten; Boon, Nico; Bodelier, Paul L. E.

    2016-01-01

    Microbial interaction is an integral component of microbial ecology studies, yet the role, extent, and relevance of microbial interaction in community functioning remains unclear, particularly in the context of global biogeochemical cycles. While many studies have shed light on the physico-chemical cues affecting specific processes, (micro)biotic controls and interactions potentially steering microbial communities leading to altered functioning are less known. Yet, recent accumulating evidence suggests that the concerted actions of a community can be significantly different from the combined effects of individual microorganisms, giving rise to emergent properties. Here, we exemplify the importance of microbial interaction for ecosystem processes by analysis of a reasonably well-understood microbial guild, namely, aerobic methane-oxidizing bacteria (MOB). We reviewed the literature which provided compelling evidence for the relevance of microbial interaction in modulating methane oxidation. Support for microbial associations within methane-fed communities is sought by a re-analysis of literature data derived from stable isotope probing studies of various complex environmental settings. Putative positive interactions between active MOB and other microbes were assessed by a correlation network-based analysis with datasets covering diverse environments where closely interacting members of a consortium can potentially alter the methane oxidation activity. Although, methanotrophy is used as a model system, the fundamentals of our postulations may be applicable to other microbial guilds mediating other biogeochemical processes. PMID:27602021

  18. Biotic Interactions in Microbial Communities as Modulators of Biogeochemical Processes: Methanotrophy as a Model System.

    PubMed

    Ho, Adrian; Angel, Roey; Veraart, Annelies J; Daebeler, Anne; Jia, Zhongjun; Kim, Sang Yoon; Kerckhof, Frederiek-Maarten; Boon, Nico; Bodelier, Paul L E

    2016-01-01

    Microbial interaction is an integral component of microbial ecology studies, yet the role, extent, and relevance of microbial interaction in community functioning remains unclear, particularly in the context of global biogeochemical cycles. While many studies have shed light on the physico-chemical cues affecting specific processes, (micro)biotic controls and interactions potentially steering microbial communities leading to altered functioning are less known. Yet, recent accumulating evidence suggests that the concerted actions of a community can be significantly different from the combined effects of individual microorganisms, giving rise to emergent properties. Here, we exemplify the importance of microbial interaction for ecosystem processes by analysis of a reasonably well-understood microbial guild, namely, aerobic methane-oxidizing bacteria (MOB). We reviewed the literature which provided compelling evidence for the relevance of microbial interaction in modulating methane oxidation. Support for microbial associations within methane-fed communities is sought by a re-analysis of literature data derived from stable isotope probing studies of various complex environmental settings. Putative positive interactions between active MOB and other microbes were assessed by a correlation network-based analysis with datasets covering diverse environments where closely interacting members of a consortium can potentially alter the methane oxidation activity. Although, methanotrophy is used as a model system, the fundamentals of our postulations may be applicable to other microbial guilds mediating other biogeochemical processes. PMID:27602021

  19. MOPS-1.0: towards a model for the regulation of the global oceanic nitrogen budget by marine biogeochemical processes

    NASA Astrophysics Data System (ADS)

    Kriest, I.; Oschlies, A.

    2015-09-01

    Global models of the oceanic nitrogen cycle are subject to many uncertainties regarding the representation of the relevant biogeochemical processes and of the feedbacks between nitrogen sources and sinks that determine space- and timescales on which the global nitrogen budget is regulated. We investigate these aspects using a global model of ocean biogeochemistry that explicitly considers phosphorus and nitrogen, including pelagic denitrification and nitrogen fixation as sink and source terms of fixed nitrogen, respectively. The model explores different parameterizations of organic matter sinking speed, oxidant affinity of oxic and suboxic remineralization, and regulation of nitrogen fixation by temperature and different stoichiometric ratios. Examination of the initial transient behavior of different model setups initialized from observed biogeochemical tracer distributions reveal changes in simulated nitrogen inventories and fluxes particularly during the first centuries. Millennial timescales have to be resolved in order to bring all biogeochemical and physical processes into a dynamically consistent steady state. Analysis of global properties suggests that not only particularly particle sinking speed but also the parameterization of denitrification determine the extent of oxygen minimum zones, global nitrogen fluxes, and hence the oceanic nitrogen inventory. However, the ways and directions in which different parameterizations of particle sinking, nitrogen fixation, and denitrification affect the global diagnostics are different suggesting that these may, in principle, be constrained independently from each other. Analysis of the model misfit with respect to observed biogeochemical tracer distributions and fluxes suggests a particle flux profile close to the one suggested by Martin et al. (1987). Simulated pelagic denitrification best agrees with the lower values between 59 and 84 Tg N yr-1 recently estimated by other authors.

  20. Modeling phase transformation behavior during thermal cycling in the heat-affected zone of stainless steel welds

    SciTech Connect

    Vitek, J.M.; Iskander, Y.S.; David, S.A.

    1995-12-31

    An implicit finite-difference analysis was used to model the diffusion-controlled transformation behavior in a ternary system. The present analysis extends earlier work by examining the transformation behavior under the influence of multiple thermal cycles. The analysis was applied to the Fe-Cr-Ni ternary system to simulate the microstructural development in austenitic stainless steel welds. The ferrite-to-austenite transformation was studied in an effort to model the response of the heat-affected zone to multiple thermal cycles experienced during multipass welding. Results show that under some conditions, a transformation ``inertia`` exists that delays the system`s response when changing from cooling to heating. Conditions under which this ``inertia`` is most influential were examined. It was also found that under some conditions, the transformation behavior does not follow the equilibrium behavior as a function of temperature. Results also provide some insight into effect of composition distribution on transformation behavior.

  1. “I like the way you move”: how hormonal changes across the menstrual cycle affect female perceptions of gait

    PubMed Central

    2012-01-01

    Background Variations in hormone concentrations across the menstrual cycle affect human female mate preferences. It has been shown that around the time of ovulation human females prefer more masculine male voices, faces, and bodies while simultaneously preferring less faces that are more feminine. They prefer also displays of male dominance, males with more symmetrical faces, and the scent of males with high levels of body symmetry. The aim of the experiments reported here was to investigate whether there are changes in female preferences for walking gaits across the menstrual cycle. Results Experiment 1 showed female observers could discriminate between point-light walkers with low and high levels of fluctuating asymmetries in their gaits. Female observers were more sensitive to asymmetries in female gaits than they were for asymmetries in male gaits. Experiment 2 showed that level of gait asymmetry did not affect the abilities of observers to discriminate female from male walkers. Experiment 3 showed that female observers did not change their preference for low and high asymmetry walkers across their menstrual cycles. However, females showed a decreased preference for all female walkers at the time during which it was estimated observers were at peak fertility. That same change in preference was not observed for male walkers. Conclusions These data suggest female observers may not value gait asymmetry, as a mate selection cue, in the same way that they value asymmetries in faces and bodies. While only “average” gaits were used in these experiments, rather than the gaits of individual walkers, the types of asymmetries in gait tested here were not used in the same way as static cues for judging the apparent healthiness of individuals. Females do discriminate well average female gait asymmetries and do change their preferences for those gaits across their menstrual cycle. Doing so may reflect the operation of processes that equip females with an advantage when

  2. Timing Carbohydrate Beverage Intake During Prolonged Moderate Intensity Exercise Does Not Affect Cycling Performance

    PubMed Central

    SCHWEITZER, GEORGE G.; SMITH, JOHN D.; LECHEMINANT, JAMES D.

    2009-01-01

    Carbohydrate beverages consumed during long-term exercise have been shown to attenuate fatigue and improve performance; however, the optimal timing of ingestion is unclear. Therefore, the purpose of this study was to determine if timing the carbohydrate ingestion (continual loading (CL), front-loading (FL), and end-loading (EL)) during prolonged exercise influenced exercise performance in competitive cyclists. Ten well-trained cyclists completed three separate exercise bouts on a bicycle ergometer, each lasting 2 hours at an intensity of ~67% VO2 max, followed by a 15-minute “all out” time trial. In the CL trial, a carbohydrate beverage was ingested throughout the trial. In the FL trial, participants ingested a carbohydrate beverage during the first hour and a placebo beverage during the second hour. In the EL trial, a carbohydrate beverage was ingested during the second hour and a placebo during the first hour. The amount of carbohydrate consumed (75 g) was the same among conditions. The order of conditions was single-blinded, counterbalanced, and determined randomly. Performance was measured by the work output during the 15-minute performance ride. There were no differences in work output among the three conditions during the final time trial. In the first hour of exercise, peak venous blood glucose was highest in the FL condition. In the second hour, peak venous blood glucose was highest in the EL condition. Following the time trial, venous blood glucose levels were similar among CL, FL, and EL. Overall, the timing of carbohydrate beverage consumption during prolonged moderate intensity cycling did not alter cycling performance.

  3. Carbohydrate supplementation during prolonged cycling exercise spares muscle glycogen but does not affect intramyocellular lipid use

    PubMed Central

    Boon, Hanneke; Gijsen, Annemie P.; Stegen, Jos H. C. H.; Kuipers, Harm; van Loon, Luc J. C.

    2007-01-01

    Using contemporary stable-isotope methodology and fluorescence microscopy, we assessed the impact of carbohydrate supplementation on whole-body and fiber-type-specific intramyocellular triacylglycerol (IMTG) and glycogen use during prolonged endurance exercise. Ten endurance-trained male subjects were studied twice during 3 h of cycling at 63 ± 4% of maximal O2 uptake with either glucose ingestion (CHO trial; 0.7 g CHO kg−1 h−1) or without (CON placebo trial; water only). Continuous infusions with [U-13C] palmitate and [6,6-2H2] glucose were applied to quantify plasma free fatty acids (FFA) and glucose oxidation rates and to estimate intramyocellular lipid and glycogen use. Before and after exercise, muscle biopsy samples were taken to quantify fiber-type-specific IMTG and glycogen content. Plasma glucose rate of appearance (Ra) and carbohydrate oxidation rates were substantially greater in the CHO vs CON trial. Carbohydrate supplementation resulted in a lower muscle glycogen use during the first hour of exercise in the CHO vs CON trial, resulting in a 38 ± 19 and 57 ± 22% decreased utilization in type I and II muscle-fiber glycogen content, respectively. In the CHO trial, both plasma FFA Ra and subsequent plasma FFA concentrations were lower, resulting in a 34 ± 12% reduction in plasma FFA oxidation rates during exercise (P < 0.05). Carbohydrate intake did not augment IMTG utilization, as fluorescence microscopy revealed a 76 ± 21 and 78 ± 22% reduction in type I muscle-fiber lipid content in the CHO and CON trial, respectively. We conclude that carbohydrate supplementation during prolonged cycling exercise does not modulate IMTG use but spares muscle glycogen use during the initial stages of exercise in endurance-trained men. PMID:17333244

  4. Investigating the initial stages of soil formation in glacier forefields using the new biogeochemical model: SHIMMER

    NASA Astrophysics Data System (ADS)

    Bradley, James; Anesio, Alexandre; Arndt, Sandra; Sabacka, Marie; Barker, Gary; Benning, Liane; Blacker, Joshua; Singarayer, Joy; Tranter, Martyn; Yallop, Marian

    2016-04-01

    Glaciers and ice sheets in Polar and alpine regions are retreating in response to recent climate warming, exposing terrestrial ecosystems that have been locked under the ice for thousands of years. Exposed soils exhibit successional characteristics that can be characterised using a chronosequence approach. Decades of empirical research in glacier forefields has shown that soils are quickly colonised by microbes which drive biogeochemical cycling of elements and affect soil properties including nutrient concentrations, carbon fluxes and soil stability (Bradley et al, 2014). The characterisation of these soils is important for our understanding of the cycling of organic matter under extreme environmental and nutrient limiting conditions, and their potential contribution to global biogeochemical cycles. This is particularly important as these new areas will become more geographically expansive with continued ice retreat. SHIMMER (Soil biogeocHemIcal Model of Microbial Ecosystem Response) (Bradley et al, 2015) is a new mathematical model that simulates biogeochemical and microbial dynamics in glacier forefields. The model captures, explores and predicts the growth of different microbial groups (classified by function), and the associated cycling of carbon, nitrogen and phosphorus along a chronosequence. SHIMMER improves typical soil model formulations by including explicit representation of microbial dynamics, and those processes which are shown to be important for glacier forefields. For example, we categorise microbial groups by function to represent the diversity of soil microbial communities, and include the different metabolic needs and physiological pathways of microbial organisms commonly found in glacier forefields (e.g. microbes derived from underneath the glacier, typical soil bacteria, and microbes that can fix atmospheric nitrogen and assimilate soil nitrogen). Here, we present data from a study where we integrated modelling using SHIMMER with empirical

  5. Aging affects spatial distribution of leg muscle oxygen saturation during ramp cycling exercise.

    PubMed

    Takagi, Shun; Kime, Ryotaro; Murase, Norio; Watanabe, Tsubasa; Osada, Takuya; Niwayama, Masatsugu; Katsumura, Toshihito

    2013-01-01

    We compared muscle oxygen saturation (SmO2) responses in several leg muscles and within a single muscle during ramp cycling exercise between elderly men (n = 8; age, 65 ± 3 years; ELD) and young men (n = 10; age, 23 ± 3 years; YNG). SmO2 was monitored at the distal site of the vastus lateralis (VLd), proximal site of the vastus lateralis (VLp), rectus femoris (RF), vastus medialis (VM), biceps femoris (BF), gastrocnemius lateralis (GL), gastrocnemius medialis (GM), and tibialis anterior (TA) by near-infrared spatial resolved spectroscopy. During submaximal exercise, significantly lower SmO2 at a given absolute work rate was observed in VLd, RF, BF, GL, and TA but not in VLp, VM, and GM in ELD than in YNG. In contrast, at all measurement sites, SmO2 at peak exercise was not significantly different between groups. These results indicate that the effects of aging on SmO2 responses are heterogeneous between leg muscles and also within a single muscle. The lower SmO2 in older men may have been caused by reduced muscle blood flow or altered blood flow distribution. PMID:23852490

  6. Methane and nitrous oxide emissions affect the life-cycle analysis of algal biofuels

    NASA Astrophysics Data System (ADS)

    Frank, Edward D.; Han, Jeongwoo; Palou-Rivera, Ignasi; Elgowainy, Amgad; Wang, Michael Q.

    2012-03-01

    Researchers around the world are developing sustainable plant-based liquid transportation fuels (biofuels) to reduce petroleum consumption and greenhouse gas emissions. Algae are attractive because they promise large yields per acre compared to grasses, grains and trees, and because they produce oils that might be converted to diesel and gasoline equivalents. It takes considerable energy to produce algal biofuels with current technology; thus, the potential benefits of algal biofuels compared to petroleum fuels must be quantified. To this end, we identified key parameters for algal biofuel production using GREET, a tool for the life-cycle analysis of energy use and emissions in transportation systems. The baseline scenario produced 55 400 g CO2 equivalent per million BTU of biodiesel compared to 101 000 g for low-sulfur petroleum diesel. The analysis considered the potential for greenhouse gas emissions from anaerobic digestion processes commonly used in algal biofuel models. The work also studied alternative scenarios, e.g., catalytic hydrothermal gasification, that may reduce these emissions. The analysis of the nitrogen recovery step from lipid-extracted algae (residues) highlighted the importance of considering the fate of the unrecovered nitrogen fraction, especially that which produces N2O, a potent greenhouse gas with global warming potential 298 times that of CO2.

  7. Glucosylceramide synthesis inhibition affects cell cycle progression, membrane trafficking, and stage differentiation in Giardia lamblia.

    PubMed

    Stefanić, Sasa; Spycher, Cornelia; Morf, Laura; Fabriàs, Gemma; Casas, Josefina; Schraner, Elisabeth; Wild, Peter; Hehl, Adrian B; Sonda, Sabrina

    2010-09-01

    Synthesis of glucosylceramide via glucosylceramide synthase (GCS) is a crucial event in higher eukaryotes, both for the production of complex glycosphingolipids and for regulating cellular levels of ceramide, a potent antiproliferative second messenger. In this study, we explored the dependence of the early branching eukaryote Giardia lamblia on GCS activity. Biochemical analyses revealed that the parasite has a GCS located in endoplasmic reticulum (ER) membranes that is active in proliferating and encysting trophozoites. Pharmacological inhibition of GCS induced aberrant cell division, characterized by arrest of cytokinesis, incomplete cleavage furrow formation, and consequent block of replication. Importantly, we showed that increased ceramide levels were responsible for the cytokinesis arrest. In addition, GCS inhibition resulted in prominent ultrastructural abnormalities, including accumulation of cytosolic vesicles, enlarged lysosomes, and clathrin disorganization. Moreover, anterograde trafficking of the encystations-specific protein CWP1 was severely compromised and resulted in inhibition of stage differentiation. Our results reveal novel aspects of lipid metabolism in G. lamblia and specifically highlight the vital role of GCS in regulating cell cycle progression, membrane trafficking events, and stage differentiation in this parasite. In addition, we identified ceramide as a potent bioactive molecule, underscoring the universal conservation of ceramide signaling in eukaryotes. PMID:20335568

  8. A new Gsdma3 mutation affecting anagen phase of first hair cycle

    SciTech Connect

    Tanaka, Shigekazu; Tamura, Masaru; Aoki, Aya; Fujii, Tomoaki; Komiyama, Hiromitsu; Sagai, Tomoko; Shiroishi, Toshihiko . E-mail: tshirois@lab.nig.ac.jp

    2007-08-10

    Recombination-induced mutation 3 (Rim3) is a spontaneous mouse mutation that exhibits dominant phenotype of hyperkeratosis and hair loss. Fine linkage analysis of Rim3 and sequencing revealed a novel single point mutation, G1124A leading to Ala348Thr, in Gsdma3 in chromosome 11. Transgenesis with BAC DNA harboring the Rim3-type Gsdma3 recaptured the Rim3 phenotype, providing direct evidence that Gsdma3 is the causative gene of Rim3. We examined the spatial expression of Gsdma3 and characterized the Rim3 phenotype in detail. Gsdma3 is expressed in differentiated epidermal cells in the skin, but not in the proliferating epidermal cells. Histological analysis of Rim3 mutant showed hyperplasia of the epidermal cells in the upper hair follicles and abnormal anagen phase at the first hair cycle. Furthermore, immunohistochemical analysis revealed hyperproliferation and misdifferentiation of the upper follicular epidermis in Rim3 mutant. These results suggest that Gsdma3 is involved in the proliferation and differentiation of epidermal stem cells.

  9. Richness, biomass, and nutrient content of a wetland macrophyte community affect soil nitrogen cycling in a diversity-ecosystem functioning experiment

    USGS Publications Warehouse

    Korol, Alicia R.; Ahn, Changwoo; Noe, Gregory

    2016-01-01

    The development of soil nitrogen (N) cycling in created wetlands promotes the maturation of multiple biogeochemical cycles necessary for ecosystem functioning. This development proceeds from gradual changes in soil physicochemical properties and influential characteristics of the plant community, such as competitive behavior, phenology, productivity, and nutrient composition. In the context of a 2-year diversity experiment in freshwater mesocosms (0, 1, 2, 3, or 4 richness levels), we assessed the direct and indirect impacts of three plant community characteristics – species richness, total biomass, and tissue N concentration – on three processes in the soil N cycle – soil net ammonification, net nitrification, and denitrification potentials. Species richness had a positive effect on net ammonification potential (NAP) through higher redox potentials and likely faster microbial respiration. All NAP rates were negative, however, due to immobilization and high rates of ammonium removal. Net nitrification was inhibited at higher species richness without mediation from the measured soil properties. Higher species richness also inhibited denitrification potential through increased redox potential and decreased nitrification. Both lower biomass and/or higher tissue ratios of carbon to nitrogen, characteristics indicative of the two annual plants, were shown to have stimulatory effects on all three soil N processes. The two mediating physicochemical links between the young macrophyte community and microbial N processes were soil redox potential and temperature. Our results suggest that early-successional annual plant communities play an important role in the development of ecosystem N multifunctionality in newly created wetland soils.

  10. Terpenoids inhibit Candida albicans growth by affecting membrane integrity and arrest of cell cycle.

    PubMed

    Zore, Gajanan B; Thakre, Archana D; Jadhav, Sitaram; Karuppayil, S Mohan

    2011-10-15

    Anti-Candida potential of six terpenoids were evaluated in this study against various isolates of Candida albicans (n=39) and non-C. albicans (n=9) that are differentially susceptible to fluconazole. All the six terpenoids tested, showed excellent activity and were equally effective against isolates of Candida sps., tested in this study. Linalool and citral were the most effective ones, inhibiting all the isolates at ≤0.064% (v/v). Five among the six terpenoids tested were fungicidal. Time dependent kill curve assay showed that MFCs of linalool and eugenol were highly toxic to C. albicans, killing 99.9% inoculum within seven min of exposure, while that of citronellal, linalyl acetate and citral required 15min, 1h and 2h, respectively. FIC index values (Linalool - 0.140, benzyl benzoate - 0.156, eugenol - 0.265, citral - 0.281 and 0.312 for linalyl acetate and citronellal) and isobologram obtained by checker board assay showed that all the six terpenoids tested exhibit excellent synergistic activity with fluconazole against a fluconazole resistant strain of C. albicans. Terpenoids tested arrested C. albicans cells at different phases of the cell cycle i.e. linalool and LA at G1, citral and citronellal at S phase and benzyl benzoate at G2-M phase and induced apoptosis. Linalool, citral, citronellal and benzyl benzoate caused more than 50% inhibition of germ tube induction at 0.008%, while eugenol and LA required 0.032 and 0.016% (v/v) concentrations, respectively. MICs of all the terpenoids for the C. albicans growth were non toxic to HeLa cells. Terpenoids tested exhibited excellent activity against C. albicans yeast and hyphal form growth at the concentrations that are non toxic to HeLa cells. Terpenoids tested in this study may find use in antifungal chemotherapy, not only as antifungal agents but also as synergistic agents along with conventional drugs like fluconazole. PMID:21596542

  11. How Subduction Settings can Affect Planetary Nitrogen Cycle: An Experimental Insight

    NASA Astrophysics Data System (ADS)

    Cedeno, D. G.; Conceicao, R. V.; Wilbert de Souza, M. R.; Carniel, L. C.; Schmitz Quinteiro, R. V.

    2015-12-01

    Nitrogen is one of the main building blocks of life on Earth and its elemental cycle is deeply connected with organic matter and the biological system. It is known that nitrogen can be stored in mantellic phases (such as clinopyroxenes) or in metallic alloys under high pressures, meaning that Earth's mantle, and even the core, could be efficient nitrogen reservoirs. Probably, nitrogen is present in these deep Earth systems since the formation of our planet. Nevertheless, it is possible that superficial nitrogen can be reintroduced in the mantle through tectonic processes along Earth history. This is reinforced by d15N values in inclusions in diamonds and other deep mantle phases. We believe that subduction zones are efficient enough to transport nitrogen from surface to mantle. Clay minerals with high charge exchange capacity (CEC) are good candidates to convey nitrogen in subduction zones, especially when we take into account the similarities between K+ and NH4+. To simulate the high-pressure high-temperature conditions found in subduction zones, we performed a series of experiments with montmorillonite clay mineral undergone to high pressure and high temperature produced by a hydraulic press coupled with toroidal chambers, in pressures ranging from 2.5 to 7.7 GPa and temperatures up to 700oC. We used ex situ XRD analysis to accompany the main montmorillonite structural changes and FTIR analysis to determine quantitatively the presence of nitrogen. So far, our results show that the main structural transition in montmorillonite happens at ~350oC at room pressure and ~450oC at 2.5 and 4.0 GPa and consists in the transformation of an open clay structure to a closed mica structure (tobelite). FTIR data show the presence of nitrogen in all the analysed experiments. With the data obtained, we can presume that clay minerals carried in subduction zones can successfully transport nitrogen and other volatiles to the mantle. However, only cold subduction systems have the

  12. CD82 expression alters with human endometrial cycles and affects the uterine endometrial receptivity in vitro.

    PubMed

    Wei, Xiaowei; Liu, Shuai; Wang, Xiaoqi; Yan, Qiu

    2012-03-01

    Embryo implantation is a process that requires both temporal and spatial synchronization of the uterine endometrium and the embryo, and the endometrium becomes receptive to the embryo during the window of implantation. Although the expression patterns of many implantation-related molecules change dynamically during this process, the impact of CD82 on endometrial receptivity has not been elucidated. By immunohistochemical staining, we found that CD82 levels rose from the proliferative phase to the secretory phase in human endometrium. Specifically, the highest level appeared in mid- and late-secretory phases. Consistently, RL95-2 cells, representative of high-receptive endometrial epithelium, expressed higher levels of CD82 than did HEC-1A cells, which are representative of low-receptive endometrial epithelium, as detected by reverse transcription-polymerase chain reaction, Western blot and immunofluorescence. Furthermore, progesterone up-regulated the expression of CD82 in both epithelial cell lines. Down-regulation of CD82 in RL95-2 cells by either CD82 siRNA transfection or treatment with a CD82 antibody significantly decreased the adhesion of human embryonic JAR cells to RL95-2 cell monolayers (P < 0.01) and inhibited the phosphorylation of focal adhesion kinase (FAK). In contrast, up-regulation of CD82 in HEC-1A cells by CD82 cDNA transfection promoted embryonic JAR cell adhesion to HEC-1A monolayers (P < 0.05) and activated the phosphorylation of FAK. In conclusion, the expression of CD82 increases in endometrial tissues during the window of embryo implantation, CD82 expression affects endometrial receptivity of the uterine epithelial cells in vitro, and the FAK signaling pathway may be involved in this phenomenon. The correlation between CD82 and endometrial receptivity suggests that CD82 may serve as a potential marker of endometrial function. PMID:22393164

  13. Understanding oceanic migrations with intrinsic biogeochemical markers.

    PubMed

    Ramos, Raül; González-Solís, Jacob; Croxall, John P; Oro, Daniel; Ruiz, Xavier

    2009-01-01

    Migratory marine vertebrates move annually across remote oceanic water masses crossing international borders. Many anthropogenic threats such as overfishing, bycatch, pollution or global warming put millions of marine migrants at risk especially during their long-distance movements. Therefore, precise knowledge about these migratory movements to understand where and when these animals are more exposed to human impacts is vital for addressing marine conservation issues. Because electronic tracking devices suffer from several constraints, mainly logistical and financial, there is emerging interest in finding appropriate intrinsic markers, such as the chemical composition of inert tissues, to study long-distance migrations and identify wintering sites. Here, using tracked pelagic seabirds and some of their own feathers which were known to be grown at different places and times within the annual cycle, we proved the value of biogeochemical analyses of inert tissue as tracers of marine movements and habitat use. Analyses of feathers grown in summer showed that both stable isotope signatures and element concentrations can signal the origin of breeding birds feeding in distinct water masses. However, only stable isotopes signalled water masses used during winter because elements mainly accumulated during the long breeding period are incorporated into feathers grown in both summer and winter. Our findings shed new light on the simple and effective assignment of marine organisms to distinct oceanic areas, providing new opportunities to study unknown migration patterns of secretive species, including in relation to human-induced mortality on specific populations in the marine environment. PMID:19623244

  14. Understanding Oceanic Migrations with Intrinsic Biogeochemical Markers

    PubMed Central

    Ramos, Raül; González-Solís, Jacob; Croxall, John P.; Oro, Daniel

    2009-01-01

    Migratory marine vertebrates move annually across remote oceanic water masses crossing international borders. Many anthropogenic threats such as overfishing, bycatch, pollution or global warming put millions of marine migrants at risk especially during their long-distance movements. Therefore, precise knowledge about these migratory movements to understand where and when these animals are more exposed to human impacts is vital for addressing marine conservation issues. Because electronic tracking devices suffer from several constraints, mainly logistical and financial, there is emerging interest in finding appropriate intrinsic markers, such as the chemical composition of inert tissues, to study long-distance migrations and identify wintering sites. Here, using tracked pelagic seabirds and some of their own feathers which were known to be grown at different places and times within the annual cycle, we proved the value of biogeochemical analyses of inert tissue as tracers of marine movements and habitat use. Analyses of feathers grown in summer showed that both stable isotope signatures and element concentrations can signal the origin of breeding birds feeding in distinct water masses. However, only stable isotopes signalled water masses used during winter because elements mainly accumulated during the long breeding period are incorporated into feathers grown in both summer and winter. Our findings shed new light on the simple and effective assignment of marine organisms to distinct oceanic areas, providing new opportunities to study unknown migration patterns of secretive species, including in relation to human-induced mortality on specific populations in the marine environment. PMID:19623244

  15. Plant Nitrogen Uptake in Terrestrial Biogeochemical Models

    NASA Astrophysics Data System (ADS)

    Marti Donati, A.; Cox, P.; Smith, M. J.; Purves, D.; Sitch, S.; Jones, C. D.

    2013-12-01

    Most terrestrial biogeochemical models featured in the last Intergovernmental Panel on Climate Change (IPPC) Assessment Report highlight the importance of the terrestrial Carbon sequestration and feedbacks between the terrestrial Carbon cycle and the climate system. However, these models have been criticized for overestimating predicted Carbon sequestration and its potential climate feedback when calculating the rate of future climate change because they do not account for the Carbon sequestration constraints caused by nutrient limitation, particularly Nitrogen (N). This is particularly relevant considering the existence of a substantial deficit of Nitrogen for plants in most areas of the world. To date, most climate models assume that plants have access to as much Nitrogen as needed, but ignore the nutrient requirements for new vegetation growth. Determining the natural demand and acquisition for Nitrogen and its associated resource optimization is key when accounting for the Carbon sequestration constrains caused by nutrient limitation. The few climate models that include C-N dynamics have illustrated that the stimulation of plant growth over the coming century may be significantly smaller than previously predicted. However, models exhibit wide differences in their predictive accuracy and lead to widely diverging and inconsistent projections accounting for an uncertain Carbon sequestration decrease due to Nitrogen limitation ranging from 7 to 64%. This reduction in growth is partially offset by an increase in the availability of nutrients resulting from an accelerated rate of decomposition of dead plants and other organic matter that occurring with a rise in temperature. However, this offset does not counterbalance the reduced level of plant growth calculated by natural nutrient limitations. Additionally, Nitrogen limitation is also expected to become more pronounced in some ecosystems as atmospheric CO2 concentration increases; resulting in less new growth and

  16. Life cycle stage and water depth affect flooding-induced adventitious root formation in the terrestrial species Solanum dulcamara

    PubMed Central

    Zhang, Qian; Visser, Eric J. W.; de Kroon, Hans; Huber, Heidrun

    2015-01-01

    Background and Aims Flooding can occur at any stage of the life cycle of a plant, but often adaptive responses of plants are only studied at a single developmental stage. It may be anticipated that juvenile plants may respond differently from mature plants, as the amount of stored resources may differ and morphological changes can be constrained. Moreover, different water depths may require different strategies to cope with the flooding stress, the expression of which may also depend on developmental stage. This study investigated whether flooding-induced adventitious root formation and plant growth were affected by flooding depth in Solanum dulcamara plants at different developmental stages. Methods Juvenile plants without pre-formed adventitious root primordia and mature plants with primordia were subjected to shallow flooding or deep flooding for 5 weeks. Plant growth and the timing of adventitious root formation were monitored during the flooding treatments. Key Results Adventitious root formation in response to shallow flooding was significantly constrained in juvenile S. dulcamara plants compared with mature plants, and was delayed by deep flooding compared with shallow flooding. Complete submergence suppressed adventitious root formation until up to 2 weeks after shoots restored contact with the atmosphere. Independent of developmental stage, a strong positive correlation was found between adventitious root formation and total biomass accumulation during shallow flooding. Conclusions The potential to deploy an escape strategy (i.e. adventitious root formation) may change throughout a plant’s life cycle, and is largely dependent on flooding depth. Adaptive responses at a given stage of the life cycle thus do not necessarily predict how the plant responds to flooding in another growth stage. As variation in adventitious root formation also correlates with finally attained biomass, this variation may form the basis for variation in resistance to shallow

  17. Deregulated expression of Cdc6 in the skin facilitates papilloma formation and affects the hair growth cycle.

    PubMed

    Búa, Sabela; Sotiropoulou, Peggy; Sgarlata, Cecilia; Borlado, Luis R; Eguren, Manuel; Domínguez, Orlando; Ortega, Sagrario; Malumbres, Marcos; Blanpain, Cedric; Méndez, Juan

    2015-01-01

    Cdc6 encodes a key protein for DNA replication, responsible for the recruitment of the MCM helicase to replication origins during the G1 phase of the cell division cycle. The oncogenic potential of deregulated Cdc6 expression has been inferred from cellular studies, but no mouse models have been described to study its effects in mammalian tissues. Here we report the generation of K5-Cdc6, a transgenic mouse strain in which Cdc6 expression is deregulated in tissues with stratified epithelia. Higher levels of CDC6 protein enhanced the loading of MCM complexes to DNA in epidermal keratinocytes, without affecting their proliferation rate or inducing DNA damage. While Cdc6 overexpression did not promote skin tumors, it facilitated the formation of papillomas in cooperation with mutagenic agents such as DMBA. In addition, the elevated levels of CDC6 protein in the skin extended the resting stage of the hair growth cycle, leading to better fur preservation in older mice. PMID:26697840

  18. Implementing high-latitude biogeochemical processes into Earth System Models

    NASA Astrophysics Data System (ADS)

    Brovkin, Victor; Kleinen, Thomas; Cresto-Aleina, Fabio; Kloster, Silvia; Ilyina, Tatiana

    2016-04-01

    Projections of future climate changes suggest that air temperatures in the Arctic could rise to the levels unprecedented in the last million years. Sensitivity of carbon storages on land and shelves to climate change of that scale is highly uncertain. Earth System models (ESMs), consisting of atmosphere, ocean, land, and cryosphere components are the main tools to understand interactions between carbon cycle and climate. However, ESM representation of ecological and biogeochemical processes in the Arctic is extremely simplistic. For example, all ESMs agree that tree cover in the future warming scenarios will move northwards to the Arctic coast, but they ignore interactions between vegetation, permafrost, and disturbances such as fires, which are critical for vegetation dynamics in this region. Improving modeling of interactions between model components and their evaluation against growing observational evidence is a promising research area. The first attempts to account for the permafrost carbon dynamics in the ESM framework suggest that CO2 and CH4 emissions from high-latitude regions in the 21st century are relatively small, but they become much more significant afterwards due to committed climate changes. Therefore, extension of ESM simulations beyond 2100 is essential to estimate a proper scale of frozen carbon pool response to human-induced climate change. Additionally, inclusion of sub-sea permafrost component into ESMs is an active research area that brings together terrestrial and marine biogeochemical communities, as well as geologists analyzing climate proxies on glacial timescales. Another challenging aspect of biogeochemical interactions in Arctic is an extreme land surface heterogeneity. A mixture of wetlands, lakes, and vegetation-covered surfaces on fine local scale is not properly reflected in the model structure. A promising approach of dealing with scaling gaps in modeling high-latitude biogeochemical processes in ESMs will be presented.

  19. Silicon biogeochemical processes in a large river (Cauvery, India)

    NASA Astrophysics Data System (ADS)

    Kameswari Rajasekaran, Mangalaa; Arnaud, Dapoigny; Jean, Riotte; Sarma Vedula, V. S. S.; Nittala, S. Sarma; Sankaran, Subramanian; Gundiga Puttojirao, Gurumurthy; Keshava, Balakrishna; Cardinal, Damien

    2016-04-01

    Silicon (Si), one of the key nutrients for diatom growth in ocean, is principally released during silicate weathering on continents and then exported by rivers. Phytoplankton composition is determined by the availability of Si relative to other nutrients, mainly N and P, which fluxes in estuarine and coastal systems are affected by eutrophication due to land use and industrialization. In order to understand the biogeochemical cycle of Si and its supply to the coastal ocean, we studied a tropical monsoonal river from Southern India (Cauvery) and compare it with other large and small rivers. Cauvery is the 7th largest river in India with a basin covering 85626 sq.km. The major part of the basin (˜66%) is covered by agriculture and inhabited by more than 30 million inhabitants. There are 96 dams built across the basin. As a consequence, 80% of the historical discharge is diverted, mainly for irrigation (Meunier et al. 2015). This makes the Cauvery River a good example of current anthropogenic pressure on silicon biogeochemical cycle. We measured amorphous silica contents (ASi) and isotopic composition of dissolved silicon (δ30Si-DSi) in the Cauvery estuary, including freshwater end-member and groundwater as well as along a 670 km transect along the river course. Other Indian rivers and estuaries have also been measured, including some less impacted by anthropogenic pressure. The average Cauvery δ30Si signature just upstream the estuary is 2.21±0.15 ‰ (n=3) which is almost 1‰ heavier than the groundwater isotopic composition (1.38±0.03). The δ30Si-DSi of Cauvery water is also almost 1‰ heavier than the world river supply to the ocean estimated so far and 0.4‰ heavier than other large Indian rivers like Ganges (Frings et al 2015) and Krishna. On the other hand, the smaller watersheds (Ponnaiyar, Vellar, and Penna) adjacent to Cauvery also display heavy δ30Si-DSi. Unlike the effect of silicate weathering, the heavy isotopic compositions in the river

  20. Ocean Acidification Affects Redox-Balance and Ion-Homeostasis in the Life-Cycle Stages of Emiliania huxleyi

    PubMed Central

    Rokitta, Sebastian D.; John, Uwe; Rost, Björn

    2012-01-01

    Ocean Acidification (OA) has been shown to affect photosynthesis and calcification in the coccolithophore Emiliania huxleyi, a cosmopolitan calcifier that significantly contributes to the regulation of the biological carbon pumps. Its non-calcifying, haploid life-cycle stage was found to be relatively unaffected by OA with respect to biomass production. Deeper insights into physiological key processes and their dependence on environmental factors are lacking, but are required to understand and possibly estimate the dynamics of carbon cycling in present and future oceans. Therefore, calcifying diploid and non-calcifying haploid cells were acclimated to present and future CO2 partial pressures (pCO2; 38.5 Pa vs. 101.3 Pa CO2) under low and high light (50 vs. 300 µmol photons m−2 s−1). Comparative microarray-based transcriptome profiling was used to screen for the underlying cellular processes and allowed to follow up interpretations derived from physiological data. In the diplont, the observed increases in biomass production under OA are likely caused by stimulated production of glycoconjugates and lipids. The observed lowered calcification under OA can be attributed to impaired signal-transduction and ion-transport. The haplont utilizes distinct genes and metabolic pathways, reflecting the stage-specific usage of certain portions of the genome. With respect to functionality and energy-dependence, however, the transcriptomic OA-responses resemble those of the diplont. In both life-cycle stages, OA affects the cellular redox-state as a master regulator and thereby causes a metabolic shift from oxidative towards reductive pathways, which involves a reconstellation of carbon flux networks within and across compartments. Whereas signal transduction and ion-homeostasis appear equally OA-sensitive under both light intensities, the effects on carbon metabolism and light physiology are clearly modulated by light availability. These interactive effects can be attributed

  1. A generic reaction-based biogeochemical simulator

    SciTech Connect

    Fang, Yilin; Yabusaki, Steven B.; Yeh, Gour T.; C.T. Miller, M.W. Farthing, W.G. Gray, and G.F. Pinder

    2004-06-17

    This paper presents a generic biogeochemical simulator, BIOGEOCHEM. The simulator can read a thermodynamic database based on the EQ3/EQ6 database. It can also read user-specified equilibrium and kinetic reactions (reactions not defined in the format of that in EQ3/EQ6 database) symbolically. BIOGEOCHEM is developed with a general paradigm. It overcomes the requirement in most available reaction-based models that reactions and rate laws be specified in a limited number of canonical forms. The simulator interprets the reactions, and rate laws of virtually any type for input to the MAPLE symbolic mathematical software package. MAPLE then generates Fortran code for the analytical Jacobian matrix used in the Newton-Raphson technique, which are compiled and linked into the BIOGEOCHEM executable. With this feature, the users are exempted from recoding the simulator to accept new equilibrium expressions or kinetic rate laws. Two examples are used to demonstrate the new features of the simulator.

  2. BIOGEOCHEMICAL INDICATORS IN AQUATIC ECOSYSTEMS

    EPA Science Inventory

    Loadings of excess organic wastes and associated nutrients to aquatic systems has numerous deleterious consequences with respect to the ecosystem services provided by these important ecosystems including perturbation of organic matter and nutrient cycling rates, reduction in diss...

  3. Quantifying the Variability of CH4 Emissions from Pan-Arctic Lakes with Lake Biogeochemical and Landscape Evolution Models

    NASA Astrophysics Data System (ADS)

    Tan, Z.; Zhuang, Q.

    2014-12-01

    Recent studies in the arctic and subarctic show that CH4 emissions from pan-arctic lakes are playing much more significant roles in the regional carbon cycling than previously estimated. Permafrost thawing due to pronounced warming at northern high latitudes affects lake morphology, changing its CH4 emissions. Thermokarst can enlarge the extent of artic lakes, exposing stable ancient carbon buried in the permafrost zone for degradation and changing a previously known carbon sink to a large carbon source. In some areas, the thawing of subarctic discontinuous and isolated permafrost can diminish thermokarst lakes. To date, few models have considered these important hydrological and biogeochemical processes to provide adequate estimation of CH4 emissions from these lakes. To fill this gap, we have developed a process-based climate-sensitive lake biogeochemical model and a landscape evolution model, which have been applied to quantify the state and variability of CH4 emissions from this freshwater system. Site-level experiments show the models are capable to capture the spatial and temporal variability of CH4 emissions from lakes across Siberia and Alaska. With the lake biogeochemical model solely, we estimate that the magnitude of CH4 emissions from lakes is 13.2 Tg yr-1 in the north of 60 ºN at present, which is on the same order of CH4 emissions from northern high-latitude wetlands. The maximum increment is 11.8 Tg CH4 yr-1 by the end of the 21st century when the worst warming scenario is assumed. We expect the landscape evolution model will improve the existing estimates.

  4. Mutations altering the gammaretrovirus endoproteolytic motif affect glycosylation of the envelope glycoprotein and early events of the virus life cycle

    SciTech Connect

    Argaw, Takele; Wilson, Carolyn A.

    2015-01-15

    Previously, we found that mutation of glutamine to proline in the endoproteolytic cleavage signal of the PERV-C envelope (RQKK to RPKK) resulted in non-infectious vectors. Here, we show that RPKK results in a non-infectious vector when placed in not only a PERV envelope, but also the envelope of a related gammaretrovirus, FeLV-B. The amino acid substitutions do not prevent envelope precursor cleavage, viral core and genome assembly, or receptor binding. Rather, the mutations result in the formation of hyperglycosylated glycoprotein and a reduction in the reverse transcribed minus strand synthesis and undetectable 2-LTR circular DNA in cells exposed to vectors with these mutated envelopes. Our findings suggest novel functions associated with the cleavage signal sequence that may affect trafficking through the glycosylation machinery of the cell. Further, the glycosylation status of the envelope appears to impact post-binding events of the viral life cycle, either membrane fusion, internalization, or reverse transcription. - Highlights: • Env cleavage signal impacts infectivity of gammaretroviruses. • Non-infectious mutants have hyper-glycosylated envelope that bind target cells. • Non-infectious mutants have defects in the formation of the double-stranded DNA. • Env cleavage motif has functions beyond cleavage of the env precursor.

  5. FBXW7 and USP7 regulate CCDC6 turnover during the cell cycle and affect cancer drugs susceptibility in NSCLC

    PubMed Central

    Merolla, Francesco; Poser, Ina; Visconti, Roberta; Ilardi, Gennaro; Paladino, Simona; Inuzuka, Hiroyuki; Guggino, Gianluca; Monaco, Roberto; Colecchia, David; Monaco, Guglielmo; Cerrato, Aniello; Chiariello, Mario; Denning, Krista; Claudio, Pier Paolo; Staibano, Stefania; Celetti, Angela

    2015-01-01

    CCDC6 gene product is a pro-apoptotic protein substrate of ATM, whose loss or inactivation enhances tumour progression. In primary tumours, the impaired function of CCDC6 protein has been ascribed to CCDC6 rearrangements and to somatic mutations in several neoplasia. Recently, low levels of CCDC6 protein, in NSCLC, have been correlated with tumor prognosis. However, the mechanisms responsible for the variable levels of CCDC6 in primary tumors have not been described yet. We show that CCDC6 turnover is regulated in a cell cycle dependent manner. CCDC6 undergoes a cyclic variation in the phosphorylated status and in protein levels that peak at G2 and decrease in mitosis. The reduced stability of CCDC6 in the M phase is dependent on mitotic kinases and on degron motifs that are present in CCDC6 and direct the recruitment of CCDC6 to the FBXW7 E3 Ubl. The de-ubiquitinase enzyme USP7 appears responsible of the fine tuning of the CCDC6 stability, affecting cells behaviour and drug response. Thus, we propose that the amount of CCDC6 protein in primary tumors, as reported in lung, may depend on the impairment of the CCDC6 turnover due to altered protein-protein interaction and post-translational modifications and may be critical in optimizing personalized therapy. PMID:25885523

  6. Mutations altering the gammaretrovirus endoproteolytic motif affect glycosylation of the envelope glycoprotein and early events of the virus life cycle.

    PubMed

    Argaw, Takele; Wilson, Carolyn A

    2015-01-15

    Previously, we found that mutation of glutamine to proline in the endoproteolytic cleavage signal of the PERV-C envelope (RQKK to RPKK) resulted in non-infectious vectors. Here, we show that RPKK results in a non-infectious vector when placed in not only a PERV envelope, but also the envelope of a related gammaretrovirus, FeLV-B. The amino acid substitutions do not prevent envelope precursor cleavage, viral core and genome assembly, or receptor binding. Rather, the mutations result in the formation of hyperglycosylated glycoprotein and a reduction in the reverse transcribed minus strand synthesis and undetectable 2-LTR circular DNA in cells exposed to vectors with these mutated envelopes. Our findings suggest novel functions associated with the cleavage signal sequence that may affect trafficking through the glycosylation machinery of the cell. Further, the glycosylation status of the envelope appears to impact post-binding events of the viral life cycle, either membrane fusion, internalization, or reverse transcription. PMID:25462351

  7. Microbial Metagenomics Reveals Climate-Relevant Subsurface Biogeochemical Processes.

    PubMed

    Long, Philip E; Williams, Kenneth H; Hubbard, Susan S; Banfield, Jillian F

    2016-08-01

    Microorganisms play key roles in terrestrial system processes, including the turnover of natural organic carbon, such as leaf litter and woody debris that accumulate in soils and subsurface sediments. What has emerged from a series of recent DNA sequencing-based studies is recognition of the enormous variety of little known and previously unknown microorganisms that mediate recycling of these vast stores of buried carbon in subsoil compartments of the terrestrial system. More importantly, the genome resolution achieved in these studies has enabled association of specific members of these microbial communities with carbon compound transformations and other linked biogeochemical processes-such as the nitrogen cycle-that can impact the quality of groundwater, surface water, and atmospheric trace gas concentrations. The emerging view also emphasizes the importance of organism interactions through exchange of metabolic byproducts (e.g., within the carbon, nitrogen, and sulfur cycles) and via symbioses since many novel organisms exhibit restricted metabolic capabilities and an associated extremely small cell size. New, genome-resolved information reshapes our view of subsurface microbial communities and provides critical new inputs for advanced reactive transport models. These inputs are needed for accurate prediction of feedbacks in watershed biogeochemical functioning and their influence on the climate via the fluxes of greenhouse gases, CO2, CH4, and N2O. PMID:27156744

  8. Cardiac Myosin Binding Protein C Phosphorylation Affects Cross-Bridge Cycle's Elementary Steps in a Site-Specific Manner

    PubMed Central

    Wang, Li; Sadayappan, Sakthivel; Kawai, Masakata

    2014-01-01

    Based on our recent finding that cardiac myosin binding protein C (cMyBP-C) phosphorylation affects muscle contractility in a site-specific manner, we further studied the force per cross-bridge and the kinetic constants of the elementary steps in the six-state cross-bridge model in cMyBP-C mutated transgenic mice for better understanding of the influence of cMyBP-C phosphorylation on contractile functions. Papillary muscle fibres were dissected from cMyBP-C mutated mice of ADA (Ala273-Asp282-Ala302), DAD (Asp273-Ala282-Asp302), SAS (Ser273-Ala282-Ser302), and t/t (cMyBP-C null) genotypes, and the results were compared to transgenic mice expressing wide-type (WT) cMyBP-C. Sinusoidal analyses were performed with serial concentrations of ATP, phosphate (Pi), and ADP. Both t/t and DAD mutants significantly reduced active tension, force per cross-bridge, apparent rate constant (2πc), and the rate constant of cross-bridge detachment. In contrast to the weakened ATP binding and enhanced Pi and ADP release steps in t/t mice, DAD mice showed a decreased ADP release without affecting the ATP binding and the Pi release. ADA showed decreased ADP release, and slightly increased ATP binding and cross-bridge detachment steps, whereas SAS diminished the ATP binding step and accelerated the ADP release step. t/t has the broadest effects with changes in most elementary steps of the cross-bridge cycle, DAD mimics t/t to a large extent, and ADA and SAS predominantly affect the nucleotide binding steps. We conclude that the reduced tension production in DAD and t/t is the result of reduced force per cross-bridge, instead of the less number of strongly attached cross-bridges. We further conclude that cMyBP-C is an allosteric activator of myosin to increase cross-bridge force, and its phosphorylation status modulates the force, which is regulated by variety of protein kinases. PMID:25420047

  9. Estuarine Biogeochemical Dynamics of Nutrients and Organic Carbon in the Columbia River: Observing Transformations Using a Biogeochemical Sensor Network

    NASA Astrophysics Data System (ADS)

    Needoba, J. A.; Peterson, T. D.; Riseman, S.; Wilkin, M.; Baptista, A. M.

    2015-12-01

    The Columbia River estuary is an ecosystem dominated by both a large river discharge and strong tidal forcing that creates fast currents, intense and variable physical stratification, low water residence times, and large gradients in salinity, temperature and water quality across the river to ocean boundary. Assessing ecosystem function and biogeochemical cycling in this environment is hampered by the inherent variability in both temporal and spatial timescales. In recent years the NSF Science and Technology Center for Coastal Margin Observation and Prediction has established a comprehensive in situ observation network that spans the estuarine gradient and captures variability associated with tides, diel cycles, episodic events, and seasonal changes in the river and ocean end-members. Here we describe the major patterns of variability in nitrate, orthophosphate, fluorescent dissolved organic carbon and related variables that demonstrate the dominant physical forcing and the biogeochemical hotspots within the ecosystem. These hotspots include intertidal lateral bays, the tidal freshwater river, and the estuarine turbidity maxima. Improved understanding of the role of these estuarine hotspots has informed ecosystem stewardship activities related to juvenile salmon survival, hypoxia, and food web structure.

  10. Extrinsic light:dark cycles, rather than endogenous circadian cycles, affect the photoperiodic counter in the pitcher-plant mosquito, Wyeomyia smithii.

    PubMed

    Emerson, Kevin J; Letaw, Alathea D; Bradshaw, William E; Holzapfel, Christina M

    2008-07-01

    A wide diversity of organisms use photoperiod (daylength) as an environmental cue to anticipate the changing seasons and to time various life-history events such as dormancy and migration. Photoperiodic time measurement consists of two main components, (1) the photoperiodic timer that discriminates between long and short days, and (2) the photoperiodic counter that accumulates and stores information from the timer and then induces the phenotypic output. Herein, we use extended night treatments to show that light is necessary to accumulate photoperiodic information across the geographic range of the mosquito, Wyeomyia smithii and that the photoperiodic counter counts extrinsic (external) light:dark cycles and not endogenous (internal) circadian cycles. PMID:18427810

  11. Extrinsic light:dark cycles, rather than endogenous circadian cycles, affect the photoperiodic counter in the pitcher-plant mosquito, Wyeomyia smithii

    PubMed Central

    Emerson, Kevin J.; Letaw, Alathea D.; Bradshaw, William E.; Holzapfel, Christina M.

    2014-01-01

    A wide diversity of organisms use photoperiod (daylength) as an environmental cue to anticipate the changing seasons and to time various life-history events such as dormancy and migration. Photoperiodic time measurement consists of two main components, (1) the photoperiodic timer that discriminates between long and short days, and (2) the photoperiodic counter that accumulates and stores information from the timer and then induces the phenotypic output. Herein, we use extended night treatments to show that light is necessary to accumulate photoperiodic information across the geographic range of the mosquito, Wyeomyia smithii and that the photoperiodic counter counts extrinsic (external) light:dark cycles and not endogenous (internal) circadian cycles. PMID:18427810

  12. JMJD2A attenuation affects cell cycle and tumourigenic inflammatory gene regulation in lipopolysaccharide stimulated neuroectodermal stem cells.

    PubMed

    Das, Amitabh; Chai, Jin Choul; Jung, Kyoung Hwa; Das, Nando Dulal; Kang, Sung Chul; Lee, Young Seek; Seo, Hyemyung; Chai, Young Gyu

    2014-11-01

    JMJD2A is a lysine trimethyl-specific histone demethylase that is highly expressed in a variety of tumours. The role of JMJD2A in tumour progression remains unclear. The objectives of this study were to identify JMJD2A-regulated genes and understand the function of JMJD2A in p53-null neuroectodermal stem cells (p53(-/-) NE-4Cs). We determined the effect of LPS as a model of inflammation in p53(-/-) NE-4Cs and investigated whether the epigenetic modifier JMJD2A alter the expression of tumourigenic inflammatory genes. Global gene expression was measured in JMJD2A knockdown (kd) p53(-/-) NE-4Cs and in LPS-stimulated JMJD2A-kd p53(-/-) NE-4C cells. JMJD2A attenuation significantly down-regulated genes were Cdca2, Ccnd2, Ccnd1, Crebbp, IL6rα, and Stat3 related with cell cycle, proliferation, and inflammatory-disease responses. Importantly, some tumour-suppressor genes including Dapk3, Timp2 and TFPI were significantly up-regulated but were not affected by silencing of the JMJD2B. Furthermore, we confirmed the attenuation of JMJD2A also down-regulated Cdca2, Ccnd2, Crebbp, and Rest in primary NSCs isolated from the forebrains of E15 embryos of C57/BL6J mice with effective p53 inhibitor pifithrin-α (PFT-α). Transcription factor (TF) motif analysis revealed known binding patterns for CDC5, MYC, and CREB, as well as three novel motifs in JMJD2A-regulated genes. IPA established molecular networks. The molecular network signatures and functional gene-expression profiling data from this study warrants further investigation as an effective therapeutic target, and studies to elucidate the molecular mechanism of JMJD2A-kd-dependent effects in neuroectodermal stem cells should be performed. PMID:25193078

  13. Complotype affects the extent of down-regulation by Factor I of the C3b feedback cycle in vitro.

    PubMed

    Lay, E; Nutland, S; Smith, J E; Hiles, I; Smith, R A G; Seilly, D J; Buchberger, A; Schwaeble, W; Lachmann, P J

    2015-08-01

    Sera from a large panel of normal subjects were typed for three common polymorphisms, one in C3 (R102G) and two in Factor H (V62I and Y402H), that influence predisposition to age-related macular degeneration and to some forms of kidney disease. Three groups of sera were tested; those that were homozygous for the three risk alleles; those that were heterozygous for all three; and those homozygous for the low-risk alleles. These groups vary in their response to the addition of exogenous Factor I when the alternative complement pathway is activated by zymosan. Both the reduction in the maximum amount of iC3b formed and the rate at which the iC3b is converted to C3dg are affected. For both reactions the at-risk complotype requires higher doses of Factor I to produce similar down-regulation. Because iC3b reacting with the complement receptor CR3 is a major mechanism by which complement activation gives rise to inflammation, the breakdown of iC3b to C3dg can be seen to have major significance for reducing complement-induced inflammation. These findings demonstrate for the first time that sera from subjects with different complement alleles behave as predicted in an in-vitro assay of the down-regulation of the alternative complement pathway by increasing the concentration of Factor I. These results support the hypothesis that exogenous Factor I may be a valuable therapeutic aid for down-regulating hyperactivity of the C3b feedback cycle, thereby providing a treatment for age-related macular degeneration and other inflammatory diseases of later life. PMID:25124117

  14. Biogeochemical Modeling of the Second Rise of Atmospheric Oxygen

    NASA Astrophysics Data System (ADS)

    Smith, M.; Catling, D. C.; Claire, M.

    2014-12-01

    The second rise of atmospheric oxygen (~600 Ma) marked an increase of atmospheric pO2 from a poorly constrained value of 0.1% < pO2 < 10% of present atmospheric level (PAL) in the early and mid Proterozoic to >10%PAL1. The event is important because it ushered in the modern era of animal life. To understand the evolution of Earth's habitability, it is therefore key to understand the cause of this 2nd rise. Here, we quantitatively examine possible causes for the 2nd rise of oxygen. We use a biogeochemical box model2 originally developed to calculate the oxygen evolution before and after the 1st rise of oxygen (~2.4 Ga). The Claire et al. (2006) model calculates the evolution of atmospheric oxygen and methane given production and loss fluxes associated with the oxygen, carbon, and iron cycles. Because the model was unable to drive pO2 to end-Proterozoic levels, the authors suggested that another buffer, such as sulfur, is needed to explain the 2nd rise of oxygen. The sulfur and oxygen cycles are tied through various biogeochemical interactions; therefore, once sulfur (as sulfate) began to accumulate in Proterozoic oceans, it likely began to heavily influence the oxygen cycle. We have added a sulfur biogeochemical cycle to this model, enabling exploration of mechanisms that buffer pO2 at intermediate levels in the Proterozoic and fail to do so in the Phanerozoic. Preliminary results show evolution of oxygen and methane that are consistent with geologic proxies. However, the model-generated 2nd rise of oxygen is dependent upon sulfur fluxes that have uncertain magnitudes, so we will present the sensitivity of our results to model assumptions while constraining scenarios for the 2nd rise of atmospheric O2. In the future, we will also integrate isotopic fractionation effects, which will allow comparison with isotopic data from sedimentary sulfides, carbonates, and organic carbon. 1Canfield, C., 2014, Treatise on Geochemistry, 197 2Claire, M.W., et al., 2006, Geobiology

  15. Emergy of the Global Biogeochemical Cycles of Biologically Active Elements

    EPA Science Inventory

    Accurate estimates of the emergy of elemental flows are needed to accurately evaluate the far field effects of anthropogenic wastes. The transformity and specific emergy of the elements and of their different chemical species is also needed to quantify the inputs to many producti...

  16. Photoreduction fuels biogeochemical cycling of iron in Spain's acid rivers

    USGS Publications Warehouse

    Gammons, C.H.; Nimick, D.A.; Parker, S.R.; Snyder, D.M.; McCleskey, R.B.; Amils, R.; Poulson, S.R.

    2008-01-01

    A number of investigations have shown that photoreduction of Fe(III) causes midday accumulations of dissolved Fe(II) in rivers and lakes, leading to large diel (24-h) fluctuations in the concentration and speciation of total dissolved iron. Less well appreciated is the importance of photoreduction in providing chemical energy for bacteria to thrive in low pH waters. Diel variations in water chemistry from the highly acidic (pH 2.3 to 3.1) Ri??o Tinto, Ri??o Odiel, and Ri??o Agrio of southwestern Spain (Iberian Pyrite Belt) resulted in daytime increases in Fe(II) concentration of 15 to 66????M at four diel sampling locations. Dissolved Fe(II) concentrations increased with solar radiation, and one of the stream sites showed an antithetic relationship between dissolved Fe(II) and Fe(III) concentrations; both results are consistent with photoreduction. The diel data were used to estimate rates of microbially catalyzed Fe(II) oxidation (1 to 3??nmol L- 1 s- 1) and maximum rates of Fe(III) photoreduction (1.7 to 4.3??nmol L- 1 s- 1). Bioenergetic calculations indicate that the latter rates are sufficient to build up a population of Fe-oxidizing bacteria to the levels observed in the Ri??o Tinto in about 30??days. We conclude that photoreduction plays an important role in the bioenergetics of the bacterial communities of these acidic rivers, which have previously been shown to be dominated by autotrophic Fe(II)-oxidizers such as Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans. Given the possibility of the previous existence of acidic, Fe(III)-rich water on Mars, photoreduction may be an important process on other planets, a fact that could have implications to astrobiological research. ?? 2008 Elsevier B.V. All rights reserved.

  17. The carbon cycle and biogeochemical dynamics in lake sediments

    USGS Publications Warehouse

    Dean, W.E.

    1999-01-01

    The concentrations of organic carbon (OC) and CaCO3 in lake sediments are often inversely related. This relation occurs in surface sediments from different locations in the same lake, surface sediments from different lakes, and with depth in Holocene sediments. Where data on accumulation rates are available, the relation holds for organic carbon and CaCO3 accumulation rates as well. An increase of several percent OC is accompanied by a decrease of several tens of percent CaCO3 indicating that the inverse relation is not due to simple dilution of one component by another. It appears from core data that once the OC concentration in the sediments becomes greater than about 12%, the CO2 produced by decomposition of that OC and production of organic acids lowers the pH of anoxic pore waters enough to dissolve any CaCO3 that reaches the sediment-water interface. In a lake with a seasonally anoxic hypolimnion, processes in the water column also can produce an inverse relation between OC and CaCO3 over time. If productivity of the lake increases, the rain rate of OC from the epilimnion increases. Biogenic removal of CO2 and accompanying increase in pH also may increase the production of CaCO3. However, the decomposition of organic matter in the hypolimnion will decrease the pH of the hypolimnion causing greater dissolution of CaCO3 and therefore a decrease in the rain rate of CaCO3 to the sediment-water interface.

  18. Micro-Scale Heterogeneity in Biogeochemical Uranium Cycling

    SciTech Connect

    Ginder-Vogel, M.; Wu, W.-M.; Kelly, S.; Criddle, C.S.; Carley, J.; Jardine, P.; Kemner, K.M.; Fendorf, S.

    2009-06-04

    One method for the in situ remediation of uranium contaminated subsurface environments is the removal of highly soluble U(VI) from groundwater by microbial reduction to the sparingly soluble U(IV) mineral uraninite. Success of this remediation strategy will, in part, be determined by the extent and products of microbial reduction. In heterogeneous subsurface environments, microbial processes will likely yield a combination of U(IV) and U(VI) phases distributed throughout the soil matrix. Here, we use a combination of bulk X-ray absorption spectroscopy (XAS) and micro-focused XAS and X-ray diffraction to determine uranium speciation and distribution with sediment from a pilot-scale uranium remediation project located in Oak Ridge, TN.

  19. Organohalide respiration and bioremediation: harnessing biogeochemical cycles (Invited)

    NASA Astrophysics Data System (ADS)

    Edwards, E.; Hug, L.; Perez de Mora, A.

    2013-12-01

    Groundwater contamination is a serious threat to global health and prosperity. Chlorinated solvents are widely used as industrial degreasers, dry-cleaning agents and precursors in chemical synthesis, and therefore are common groundwater contaminants. Owing to their toxicity, even small spills render groundwater unsuitable for use, and cleanup is typically a costly and long-term undertaking. Dehalococcoides, Dehalobacter, Dehalogenimonas and other unusual microbes have been discovered that can dechlorinate many groundwater contaminants, in particular, the common solvents tetrachloroethene and trichloroethene to the benign product ethene. Remarkably, these organisms obtain energy for growth from dechlorination in a process termed organohalide respiration. The use of biostimulation and bioaugmentation is growing, even at sites with complex hydrogeology and high concentrations of contaminants. Molecular understanding of the unusual metabolism of these organisms is helping to design successful remediation strategies. Four aspects will be emphasized: 1) the nature of the remarkable enzymes that catalyze dechlorination reactions, 2) the role of the non-dechlorinating microbes in providing essential nutrients to dechlorinating organisms, 3) the effects of mixtures of contaminants and 4) the origins of organohalide respiration. Morevoer, the hunt is on to further explore nature's diversity to discover other unusual or novel microbes capable of detoxifying a broader range of contaminants. New molecular biology and genomic tools are helping us understand how these microbes make a living, and how we can take advantage of their abilities to clean up the environment. In this presentation I will review some of the current trends in bioremediation with particular focus on how molecular tools are helping with remediation design, scope and troubleshooting. I will draw from a number of examples from my own laboratory and elsewhere.

  20. Biogeochemical Cycle of Methanol in Anoxic Deep-Sea Sediments

    PubMed Central

    Yanagawa, Katsunori; Tani, Atsushi; Yamamoto, Naoya; Hachikubo, Akihiro; Kano, Akihiro; Matsumoto, Ryo; Suzuki, Yohey

    2016-01-01

    The biological flux and lifetime of methanol in anoxic marine sediments are largely unknown. We herein reported, for the first time, quantitative methanol removal rates in subsurface sediments. Anaerobic incubation experiments with radiotracers showed high rates of microbial methanol consumption. Notably, methanol oxidation to CO2 surpassed methanol assimilation and methanogenesis from CO2/H2 and methanol. Nevertheless, a significant decrease in methanol was not observed after the incubation, and this was attributed to the microbial production of methanol in parallel with its consumption. These results suggest that microbial reactions play an important role in the sources and sinks of methanol in subseafloor sediments. PMID:27301420

  1. Mercury Biogeochemical Cycling in the Ocean and Policy Implications

    PubMed Central

    Mason, Robert P.; Choi, Anna L.; Fitzgerald, William F.; Hammerschmidt, Chad R.; Lamborg, Carl H.; Soerensen, Anne L.; Sunderland, Elsie M.

    2012-01-01

    Anthropogenic activities have enriched mercury in the biosphere by at least a factor of three, leading to increases in total mercury (Hg) in the surface ocean. However, the impacts on ocean fish and associated trends in human exposure as a result of such changes are less clear. Here we review our understanding of global mass budgets for both inorganic and methylated Hg species in ocean seawater. We consider external inputs from atmospheric deposition and rivers as well as internal production of monomethylmercury (CH3Hg) and dimethylmercury ((CH3)2Hg). Impacts of large-scale ocean circulation and vertical transport processes on Hg distribution throughout the water column and how this influences bioaccumulation into ocean food chains are also discussed. Our analysis suggests that while atmospheric deposition is the main source of inorganic Hg to open ocean systems, most of the CH3Hg accumulating in ocean fish is derived from in situ production within the upper waters (<1000 m). An analysis of the available data suggests that concentrations in the various ocean basins are changing at different rates due to differences in atmospheric loading and that the deeper waters of the oceans are responding slowly to changes in atmospheric Hg inputs. Most biological exposures occur in the upper ocean and therefore should respond over years to decades to changes in atmospheric mercury inputs achieved by regulatory control strategies. Migratory pelagic fish such as tuna and swordfish are an important component of CH3Hg exposure for many human populations and therefore any reduction in anthropogenic releases of Hg and associated deposition to the ocean will result in a decline in human exposure and risk. PMID:22559948

  2. Mercury biogeochemical cycling in the ocean and policy implications.

    PubMed

    Mason, Robert P; Choi, Anna L; Fitzgerald, William F; Hammerschmidt, Chad R; Lamborg, Carl H; Soerensen, Anne L; Sunderland, Elsie M

    2012-11-01

    Anthropogenic activities have enriched mercury in the biosphere by at least a factor of three, leading to increases in total mercury (Hg) in the surface ocean. However, the impacts on ocean fish and associated trends in human exposure as a result of such changes are less clear. Here we review our understanding of global mass budgets for both inorganic and methylated Hg species in ocean seawater. We consider external inputs from atmospheric deposition and rivers as well as internal production of monomethylmercury (CH₃Hg) and dimethylmercury ((CH₃)₂Hg). Impacts of large-scale ocean circulation and vertical transport processes on Hg distribution throughout the water column and how this influences bioaccumulation into ocean food chains are also discussed. Our analysis suggests that while atmospheric deposition is the main source of inorganic Hg to open ocean systems, most of the CH₃Hg accumulating in ocean fish is derived from in situ production within the upper waters (<1000 m). An analysis of the available data suggests that concentrations in the various ocean basins are changing at different rates due to differences in atmospheric loading and that the deeper waters of the oceans are responding slowly to changes in atmospheric Hg inputs. Most biological exposures occur in the upper ocean and therefore should respond over years to decades to changes in atmospheric mercury inputs achieved by regulatory control strategies. Migratory pelagic fish such as tuna and swordfish are an important component of CH₃Hg exposure for many human populations and therefore any reduction in anthropogenic releases of Hg and associated deposition to the ocean will result in a decline in human exposure and risk. PMID:22559948

  3. Terrestrial biogeochemical cycles - Global interactions with the atmosphere and hydrology

    NASA Technical Reports Server (NTRS)

    Schimel, David S.; Parton, William J.; Kittel, Timothy G. F.

    1991-01-01

    A review is presented of developments in ecosystem theory, remote sensing, and geographic information systems that support new endeavors in spatial modeling. A paradigm has emerged to predict ecosystem behavior based on understanding responses to multiple resources. Ecosystem models couple primary production to decomposition and nutrient availability utilizing this paradigm. It is indicated that coupling of transport and ecosystem processes alters the behavior of earth system components (terrestrial ecosystems, hydrology, and the atmosphere) from that of an uncoupled model.

  4. Using Geochemical Indicators to Distinguish High Biogeochemical Activity in Sediments

    NASA Astrophysics Data System (ADS)

    Kenwell, A. M.; Navarre-Sitchler, A.; Prugue, R.; Spear, J. R.; Williams, K. H.; Maxwell, R. M.

    2014-12-01

    A better understanding of how microbial communities interact with their surroundings in physically and chemically heterogeneous subsurface environments will lead to improved quantification of biogeochemical reactions and associated nutrient cycling. This study develops a methodology to predict elevated rates of biogeochemical activity (microbial "hotspots") in subsurface environments by correlating microbial community structure with the spatial distribution of geochemical indicators in subsurface sediments. Statistical hierarchical cluster analyses (HCA) of X-ray fluorescence (XRF), simulated precipitation leachate, bioavailable Fe and Mn, total organic carbon (TOC), microbial community structure, grain size, bulk density and moisture content data were used to identify regions of the subsurface characterized by biogeochemical hotspots and sample characteristics indicative of these hotspots within fluvially-derived aquifer sediments. The methodology has been applied to (a) alluvial materials collected at a former uranium mill site near Rifle, Colorado and (b) relatively undisturbed floodplain deposits (soils and sediments) collected along the East River near Crested Butte, Colorado. At Rifle, 33 sediment samples were taken from 8 sediment cores and at the East River 33 soil/sediment samples were collected across and perpendicular to 3 active meanders. The East River watershed exhibits characteristic fluvial progression and serves as a representative example of many headwater catchments with the upper Colorado River basin. Initial clustering revealed that operationally defined hotspots were characterized by high organic carbon, bioavailable iron and dark colors but not necessarily low hydraulic conductivity. Applying the method to identify hotspots in both contaminated and natural floodplain deposits and their associated alluvial aquifers demonstrates the broad applicability of a geochemical indicator based approach.

  5. Biogeochemical interactions affecting hepatic trace element levels in aquatic birds

    SciTech Connect

    Moeller, G.

    1996-07-01

    Knowledge of elemental interactions is important to the toxicological assessment of wildlife in the geochemical environment. This study determines the concentrations of Al, As, B, Ba, Be, Cd, Cr, Cu, Fe, Pb, Li, Mg, Mn, Hg, Mo, Ni, Se, Ag, V, and Zn in aquatic bird liver, fish liver, whole bivalves, insects, and waters in several aquatic ecosystems in northern California. There is evidence of strong in vivo and environmental interactions, including the observation of manganese as a possible cofactor or indicator in selenium bioaccumulation. The nearest neighbor selenium correlation in aquatic bird liver tissue that results from this work is Cd-Mn-Se-Hg-As. The correlation of liver selenium to manganese in vivo and the result that the majority of the variance in liver selenium concentration is contained in the manganese term of the regression model relating Se to Cd, Mn, and Hg is new knowledge in the study of aquatic birds. A linear relationship between liver selenium and environmental manganese (water and sediment) is found in the data, suggesting a water chemistry compartmentalization or activation of toxicants. Alternatively, the hepatic concentrations of selenium, manganese, and iron suggest induction of enzymes in response to oxidative stress.

  6. Modelling Marine Biological and Biogeochemical Data

    NASA Astrophysics Data System (ADS)

    Soetaert, Karline; van Oevelen, Dick

    2011-09-01

    In the environmental sciences, mathematic models are commonly applied to analyze ecological and biogeochemical data. The technique where a model is used to interpret available measurements such as to retrieve unmeasured information on the system being observed is called "inverse modelling". In this paper we will discuss and give examples of two modeling techniques used to analyse ecological and biogeochemical data. On the one hand are mechanistic mathematical models that are written as a set of non-linear differential equations. On the other hand are so-called linear inverse models (LIMs) that consist of a set of linear equations that need to be solved for the unknowns.

  7. Widespread euxinia in the aftermath of the Lomagundi event: insights from a modeling study of ocean biogeochemical dynamics

    NASA Astrophysics Data System (ADS)

    Ozaki, Kazumi; Tajika, Eiichi

    2015-04-01

    The emergence of strongly sulphidic oceanic waters (euxinia) during the Proterozoic may have affected biological turnover, extinction, and evolution, not only because of its toxicity to eukaryotes but also because of its fundamental role on bioessential trace metal availability. From this point of view, the evidence for euxinic environments in the Lomagundi-Jatuli event (LJE) aftermath (~2.08-2.05 billion years ago) in Gabon and Karelia are notable because their low δ98/95Mo values (less than 0.95o and 0.85o respectively) imply widespread euxinia at that time. The Francevillian Group in Gabon represents the oxic-anoxic/euxinic transitional sequence, implying a fluctuation in the atmospheric redox condition from oxic to relatively reducing, possibly due to the oxidation of substantial amount of organic matter deposited during the LJE. The large positive anomaly of sulphur isotopes and a substantial contraction of marine sulphate reservoir size through the latter part of the LJE also imply a fall in surface oxidation state. Variations of the oxygenation state of the Earth's surface would have caused substantial changes in oceanic chemical composition and, in turn, would surely have impacted the biosphere. However, the nature and dynamics of oceanic biogeochemical cycles for this interval are poorly understood. To unravel cause and effect of the variations of oceanic redox state in the Paleoproteorozoic, we improved the CANOPS model (a 1-D advection-diffusion-reaction marine biogeochemical cycle model), in which coupled C-N-O-P-S marine biogeochemical cycles and a series of redox reactions were adequately taken into account. Through systematic sensitivity experiments we show that a substantial drop in atmospheric oxygen level could cause a widespread euxinia for millions of years, which provides a theoretical explanation consistent with the geological records, such as large positive anomaly of δ34S, low δ98/95Mo, and a decrease in SO4 concentration, in the

  8. Potential effects of climate change and variability on watershed biogeochemical processes and water quality in Northeast Asia.

    PubMed

    Park, Ji-Hyung; Duan, Lei; Kim, Bomchul; Mitchell, Myron J; Shibata, Hideaki

    2010-02-01

    An overview is provided of the potential effects of climate change on the watershed biogeochemical processes and surface water quality in mountainous watersheds of Northeast (NE) Asia that provide drinking water supplies for large populations. We address major 'local' issues with the case studies conducted at three watersheds along a latitudinal gradient going from northern Japan through the central Korean Peninsula and ending in southern China. Winter snow regimes and ground snowpack dynamics play a crucial role in many ecological and biogeochemical processes in the mountainous watersheds across northern Japan. A warmer winter with less snowfall, as has been projected for northern Japan, will alter the accumulation and melting of snowpacks and affect hydro-biogeochemical processes linking soil processes to surface water quality. Soils on steep hillslopes and rich in base cations have been shown to have distinct patterns in buffering acidic inputs during snowmelt. Alteration of soil microbial processes in response to more frequent freeze-thaw cycles under thinner snowpacks may increase nutrient leaching to stream waters. The amount and intensity of summer monsoon rainfalls have been increasing in Korea over recent decades. More frequent extreme rainfall events have resulted in large watershed export of sediments and nutrients from agricultural lands on steep hillslopes converted from forests. Surface water siltation caused by terrestrial export of sediments from these steep hillslopes is emerging as a new challenge for water quality management due to detrimental effects on water quality. Climatic predictions in upcoming decades for southern China include lower precipitation with large year-to-year variations. The results from a four-year intensive study at a forested watershed in Chongquing province showed that acidity and the concentrations of sulfate and nitrate in soil and surface waters were generally lower in the years with lower precipitation, suggesting year

  9. Water, Carbon, and Nutrient Cycling Following Insect-induced Tree Mortality: How Well Do Plot-scale Observations Predict Ecosystem-Scale Response?

    NASA Astrophysics Data System (ADS)

    Brooks, P. D.; Barnard, H. R.; Biederman, J. A.; Borkhuu, B.; Edburg, S. L.; Ewers, B. E.; Gochis, D. J.; Gutmann, E. D.; Harpold, A. A.; Hicke, J. A.; Pendall, E.; Reed, D. E.; Somor, A. J.; Troch, P. A.

    2011-12-01

    Widespread tree mortality caused by insect infestations and drought has impacted millions of hectares across western North America in recent years. Although previous work on post-disturbance responses (e.g. experimental manipulations, fire, and logging) provides insight into how water and biogeochemical cycles may respond to insect infestations and drought, we find that the unique nature of these drivers of tree mortality complicates extrapolation to larger scales. Building from previous work on forest disturbance, we present a conceptual model of how temporal changes in forest structure impact the individual components of energy balance, hydrologic partitioning, and biogeochemical cycling and the interactions among them. We evaluate and refine this model using integrated observations and process modeling on multiple scales including plot, stand, flux tower footprint, hillslope, and catchment to identify scaling relationships and emergent patterns in hydrological and biogeochemical responses. Our initial results suggest that changes in forest structure at point or plot scales largely have predictable effects on energy, water, and biogeochemical cycles that are well captured by land surface, hydrological, and biogeochemical models. However, observations from flux towers and nested catchments suggest that both the hydrological and biogeochemical effects observed at tree and plot scales may be attenuated or exacerbated at larger scales. Compensatory processes are associated with attenuation (e.g. as transpiration decreases, evaporation and sublimation increase), whereas both attenuation and exacerbation may result from nonlinear scaling behavior across transitions in topography and ecosystem structure that affect the redistribution of energy, water, and solutes. Consequently, the effects of widespread tree mortality on ecosystem services of water supply and carbon sequestration will likely depend on how spatial patterns in mortality severity across the landscape

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  11. Isotopes and Isoscapes: Tools for Testing Hydrological and Biogeochemical Models

    NASA Astrophysics Data System (ADS)

    Kendall, C.

    2014-12-01

    In the 21st century, the importance of high quality water resources cannot be overstated. New approaches are needed to pinpoint sources and ages of multiple contaminants, and to better understand critical hydrologic systems. Stable isotopic compositions of materials often show strong spatial and temporal distributions related to combinations of sources and processes. Isoscapes (spatial and/or temporal maps) of riverine and atmospheric data are increasingly being found to be effective means for assessing the effects of different land uses and biogeochemical processes on water resources. Hence, isotopes and isoscapes are a potentially powerful component of monitoring and assessment programs that are aimed at quantifying and mitigating alterations to environments from human activities (anthropogenic disturbances). Locations exhibiting unusually high rates of biogeochemical cycling or elevated pollution levels usually have distinctive isotopic compositions that are suggestive or diagnostic of specific reactions and pollution sources. Isotopes can be more effective at identifying hot spots and hot moments than concentrations alone because isotopic ratios may change even when concentrations do not. Hence, isotopes provide valuable additions to standard chemical and hydrological mass balance methods. This presentation will examine how the field of isotope hydrology has evolved over my 40+ year career as an isotope geochemist, highlight several exciting recent research thrusts, and share some thoughts on future research directions.

  12. Biogeochemical Transformation Pathways through the Land-water Geosphere

    NASA Astrophysics Data System (ADS)

    Destouni, G.; Asokan, S. M.; Augustsson, A.; Balfors, B.; Bring, A.; Jaramillo, F.; Jarsjo, J.; Johansson, E.; Juston, J.; Levi, L.; Olofsson, B.; Prieto, C.; Quin, A.; Åström, M. E.; Cvetkovic, V.

    2014-12-01

    Water on land undergoes and participates in many biogeochemical exchanges and changes. A bits-and-pieces approach to these may miss essential aspects of change propagation and transformation by land-water through different segments of the Earth system. This paper proposes a conceptualization of the entire land-water geosphere as a scale-free catchment-wise organised system (Figure 1), emphasizing four key new system aspects compared to traditional hydrosphere/water cycle view: i) distinction of coastal divergent in addition to traditional convergent catchments; ii) physical and social-ecological system coupling through four main nodal zones/interfaces (surface, subsurface, coastal, observation); iii) flow-transport pathways as system coupling agents; iv) multiple interactions with the anthroposphere as integral system parts. Utilizing this conceptualization, we identify distinct patterns of direct anthropogenic change in large-scale water and waterborne nutrient fluxes, emerging across different parts of the world. In general, its embedment directly in the anthroposphere/technosphere makes land-water a key geosphere for understanding and monitoring human-driven biogeochemical changes. Further progress in system-level understanding of such changes requires studies of land-water as a continuous yet structured geosphere following the proposed spatiotemporal pathways of change propagation-transformation.

  13. Long-term biogeochemical impacts of liming the ocean

    NASA Astrophysics Data System (ADS)

    Ilyina, T.; Wolf-Gladrow, D.; Munhoven, G.; Heinze, C.

    2011-12-01

    Fossil fuel CO2 emissions result in large-scale long-term perturbations in seawater chemistry. Oceans take up atmospheric CO2, and several geo-engineering approaches have been suggested to mitigate impacts of CO2 emissions and resulting ocean acidification that are based on this property. One of them is to enhance weathering processes to remove atmospheric CO2. This method involves dissolving rocks (i.e. limestone) or adding strong bases (i.e. calcium hydroxide) in the upper ocean and is termed as liming the oceans. The net effect of this approach is to increase ocean alkalinity, thereby increasing the oceanic capacity to store anthropogenic CO2. Another effect of adding alkalinity would be to drive seawater to higher pH values and thus counteract the ongoing ocean acidification. However, whereas adding bases only alter alkalinity of seawater, dissolution of carbonates perturb both, alkalinity and dissolved inorganic carbon budgets. Thus, on longer time scales, these two methods will likely have different biogeochemical effects in the ocean. Here we test enduring implications of the two approaches for marine carbon cycle using the global ocean biogeochemical model HAMOCC. In our model scenarios we add alkalinity in the amounts proportional to fossil fuel emissions. We compare the long-term effectiveness of the two geo-engineering approaches to decrease atmospheric CO2.

  14. Global Change: A Biogeochemical Perspective

    NASA Technical Reports Server (NTRS)

    Mcelroy, M.

    1983-01-01

    A research program that is designed to enhance our understanding of the Earth as the support system for life is described. The program change, both natural and anthropogenic, that might affect the habitability of the planet on a time scale roughly equal to that of a human life is studied. On this time scale the atmosphere, biosphere, and upper ocean are treated as a single coupled system. The need for understanding the processes affecting the distribution of essential nutrients--carbon, nitrogen, phosphorous, sulfur, and water--within this coupled system is examined. The importance of subtle interactions among chemical, biological, and physical effects is emphasized. The specific objectives are to define the present state of the planetary life-support system; to ellucidate the underlying physical, chemical, and biological controls; and to provide the body of knowledge required to assess changes that might impact the future habitability of the Earth.

  15. JMJD2A attenuation affects cell cycle and tumourigenic inflammatory gene regulation in lipopolysaccharide stimulated neuroectodermal stem cells

    SciTech Connect

    Das, Amitabh; Chai, Jin Choul; Jung, Kyoung Hwa; Das, Nando Dulal; Kang, Sung Chul; Lee, Young Seek; Seo, Hyemyung; Chai, Young Gyu

    2014-11-01

    JMJD2A is a lysine trimethyl-specific histone demethylase that is highly expressed in a variety of tumours. The role of JMJD2A in tumour progression remains unclear. The objectives of this study were to identify JMJD2A-regulated genes and understand the function of JMJD2A in p53-null neuroectodermal stem cells (p53{sup −/−} NE-4Cs). We determined the effect of LPS as a model of inflammation in p53{sup −/−} NE-4Cs and investigated whether the epigenetic modifier JMJD2A alter the expression of tumourigenic inflammatory genes. Global gene expression was measured in JMJD2A knockdown (kd) p53{sup −/−} NE-4Cs and in LPS-stimulated JMJD2A-kd p53{sup −/−} NE-4C cells. JMJD2A attenuation significantly down-regulated genes were Cdca2, Ccnd2, Ccnd1, Crebbp, IL6rα, and Stat3 related with cell cycle, proliferation, and inflammatory-disease responses. Importantly, some tumour-suppressor genes including Dapk3, Timp2 and TFPI were significantly up-regulated but were not affected by silencing of the JMJD2B. Furthermore, we confirmed the attenuation of JMJD2A also down-regulated Cdca2, Ccnd2, Crebbp, and Rest in primary NSCs isolated from the forebrains of E15 embryos of C57/BL6J mice with effective p53 inhibitor pifithrin-α (PFT-α). Transcription factor (TF) motif analysis revealed known binding patterns for CDC5, MYC, and CREB, as well as three novel motifs in JMJD2A-regulated genes. IPA established molecular networks. The molecular network signatures and functional gene-expression profiling data from this study warrants further investigation as an effective therapeutic target, and studies to elucidate the molecular mechanism of JMJD2A-kd-dependent effects in neuroectodermal stem cells should be performed. - Highlights: • Significant up-regulation of epigenetic modifier JMJD2A mRNA upon LPS treatment. • Inhibition of JMJD2A attenuated key inflammatory and tumourigenic genes. • Establishing IPA based functional genomics in JMJD2A-attenuated p53{sup

  16. Biogeochemical Process Comparison of the Five USGS Water, Energy, and Biogeochemical Budget (WEBB) Sites

    NASA Astrophysics Data System (ADS)

    Shanley, J. B.; Peters, N. E.; Aulenbach, B. T.; Blum, A. E.; Campbell, D. H.; Clow, D. W.; Larsen, M. C.; Mast, M. A.; Stallard, R. F.; Troester, J. W.; Walker, J. F.; Webb, R. M.; White, A. F.

    2001-12-01

    Input - output budgets (in wet deposition and streamwater) have been constructed for water and major solutes at the five USGS Water, Energy, and Biogeochemical Budget (WEBB) sites for the period 1992-97 (Peters et al., 2000). In this poster we interpret the net chemical fluxes to identify the controlling biogeochemical processes, as influenced by the strong physical and biological contrasts (climate, geology, physiography, and vegetation types) in the five diverse environments. The five sites are: Allequash Creek, Wisconsin (low-relief humid continental forest); Andrews Creek, Colorado (cold alpine, taiga/tundra, and subalpine boreal forest); Icacos River, Puerto Rico (lower montane, wet tropical forest); Panola Mountain, Georgia (humid subtropical piedmont forest); and Sleepers River, Vermont (humid northern hardwood forest). Base cations and Si produced by chemical weathering displayed a net export at each site. The magnitude and stoichiometry of export reflects mineralogy, climate (temperature and rainfall), and water residence time in the subsurface. The lowest and highest mass export generally was for Andrews Creek and Icacos River, respectively, consistent with their extreme mean annual temperatures (0/degC in Colorado to 21/degC in Puerto Rico) and the limited residence time of meltwater at Andrews Creek. Calcite in bedrock at the three coldest watersheds caused somewhat higher relative export of Ca, especially at Sleepers River where calcite weathering is a dominant control on stream chemistry. In contrast, the high Mg content of the volcaniclastic rocks at Icacos River and glacial deposits at Allequash Creek caused disproportionately high Mg export relative to the other sites. Relatively high Na export at Panola Mountain and K export at Sleepers River are probably caused by plagioclase and biotite weathering, respectively. SO4 is retained at the two warmest sites, Panola Mountain and Icacos River. SO4 adsorption is known to limit SO4- export in highly

  17. Iron-light colimitation in a global ocean biogeochemical model and the sensitivity of oceanic CO2 uptake to dust deposition

    NASA Astrophysics Data System (ADS)

    Nickelsen, L.; Oschlies, A.

    2012-12-01

    The iron hypothesis of glacial-interglacial cycles states that glacial increases in the deposition of dust enhanced the concentrations of the micronutrient iron in the ocean where it triggered phytoplankton growth and thus CO2 uptake. Indeed, iron fertilization experiments find that phytoplankton needs iron in particular for nitrate uptake, light harvesting, synthesis of chlorophyll and in the electron transport chain of photosynthesis. Previous global biogeochemical models used to extrapolate results from local culture and field experiments have suggested that the sensitivity of ocean biogeochemistry to changes in dust deposition is too low to account for the observed glacial-interglacial changes of atmospheric CO2 concentrations. Here we show that this sensitivity is increased significantly when iron-light colimitation, i.e. the impact of iron on light harvesting capabilities and chlorophyll synthesis, is explicitly considered in a global biogeochemical ocean model. Iron-light colimitation increases the shift of export production to higher latitudes at high dust deposition and amplifies iron limitation at low dust deposition. Our results suggest that iron fertilization by increased dust deposition may explain a substantially larger portion of the observed past CO2 variability than thought previously. Our results emphasize the role of iron as a key limiting nutrient for phytoplankton in the ocean, with a high potential for changes in oceanic iron supply affecting the global carbon cycle and climate.

  18. Biogeochemical evolution of a landfill leachate plume, Norman, Oklahoma.

    PubMed

    Cozzarelli, I M; Böhlke, J K; Masoner, J; Breit, G N; Lorah, M M; Tuttle, M L W; Jaeschke, J B

    2011-01-01

    Leachate from municipal landfills can create groundwater contaminant plumes that may last for decades to centuries. The fate of reactive contaminants in leachate-affected aquifers depends on the sustainability of biogeochemical processes affecting contaminant transport. Temporal variations in the configuration of redox zones downgradient from the Norman Landfill were studied for more than a decade. The leachate plume contained elevated concentrations of nonvolatile dissolved organic carbon (NVDOC) (up to 300 mg/L), methane (16 mg/L), ammonium (650 mg/L as N), iron (23 mg/L), chloride (1030 mg/L), and bicarbonate (4270 mg/L). Chemical and isotopic investigations along a 2D plume transect revealed consumption of solid and aqueous electron acceptors in the aquifer, depleting the natural attenuation capacity. Despite the relative recalcitrance of NVDOC to biodegradation, the center of the plume was depleted in sulfate, which reduces the long-term oxidation capacity of the leachate-affected aquifer. Ammonium and methane were attenuated in the aquifer relative to chloride by different processes: ammonium transport was retarded mainly by physical interaction with aquifer solids, whereas the methane plume was truncated largely by oxidation. Studies near plume boundaries revealed temporal variability in constituent concentrations related in part to hydrologic changes at various time scales. The upper boundary of the plume was a particularly active location where redox reactions responded to recharge events and seasonal water-table fluctuations. Accurately describing the biogeochemical processes that affect the transport of contaminants in this landfill-leachate-affected aquifer required understanding the aquifer's geologic and hydrodynamic framework. PMID:21314684

  19. Biogeochemical evolution of a landfill leachate plume, Norman, Oklahoma

    USGS Publications Warehouse

    Cozzarelli, Isabelle M.; Bohlke, Johnkarl F.; Masoner, Jason R.; Breit, George N.; Lorah, Michelle M.; Tuttle, Michele L.W.; Jaeschke, Jeanne B.

    2011-01-01

    Leachate from municipal landfills can create groundwater contaminant plumes that may last for decades to centuries. The fate of reactive contaminants in leachate-affected aquifers depends on the sustainability of biogeochemical processes affecting contaminant transport. Temporal variations in the configuration of redox zones downgradient from the Norman Landfill were studied for more than a decade. The leachate plume contained elevated concentrations of nonvolatile dissolved organic carbon (NVDOC) (up to 300 mg/L), methane (16 mg/L), ammonium (650 mg/L as N), iron (23 mg/L), chloride (1030 mg/L), and bicarbonate (4270 mg/L). Chemical and isotopic investigations along a 2D plume transect revealed consumption of solid and aqueous electron acceptors in the aquifer, depleting the natural attenuation capacity. Despite the relative recalcitrance of NVDOC to biodegradation, the center of the plume was depleted in sulfate, which reduces the long-term oxidation capacity of the leachate-affected aquifer. Ammonium and methane were attenuated in the aquifer relative to chloride by different processes: ammonium transport was retarded mainly by physical interaction with aquifer solids, whereas the methane plume was truncated largely by oxidation. Studies near plume boundaries revealed temporal variability in constituent concentrations related in part to hydrologic changes at various time scales. The upper boundary of the plume was a particularly active location where redox reactions responded to recharge events and seasonal water-table fluctuations. Accurately describing the biogeochemical processes that affect the transport of contaminants in this landfill-leachate-affected aquifer required understanding the aquifer's geologic and hydrodynamic framework.

  20. Global change and mercury cycling: challenges for implementing a global mercury treaty.

    PubMed

    Selin, Noelle E

    2014-06-01

    The Minamata Convention aims to protect human health and the environment from anthropogenic emissions and releases of mercury. In the present study, the provisions of the Minamata Convention are examined to assess their influence on global biogeochemical cycling of Hg. Although the convention's scope covers all major categories of atmospheric emissions, the degree to which it will affect future emissions trajectories remains unclear. A box model analysis shows that future global biogeochemical cycling under projected technological provisions would result mainly in avoided increases and that estimated differences in atmospheric concentrations resulting from policies would be on the order of 1% to 2% per year. Present experience suggests that scientific knowledge is not currently sufficient to attribute causes to changes of this magnitude. Enhancements to capacity to measure the effectiveness of the Minamata Convention are suggested, including both measurement and modeling. PMID:24038450

  1. Three Independent Forms of Regulation Affect Expression of Ho, Cln1 and Cln2 during the Cell Cycle of Saccharomyces Cerevisiae

    PubMed Central

    Breeden, L.; Mikesell, G.

    1994-01-01

    The G(1) cyclins (CLNs) bind to and activate the CDC28 kinase during the G(1) to S transition in Saccharomyces cerevisiae. Two G(1) cyclins are regulated at the RNA level so that their RNAs peak at the G(1)/S boundary. In this report we show that the cell cycle regulation of CLN1 and CLN2 is partially determined by the restricted expression of SWI4, a known trans-activator of SCB elements. When SWI4 is constitutively expressed or deleted, cell cycle regulation of CLN1/2 is reduced but not eliminated. In the absence of Swi6, another known regulator of both SCB and MCB elements, cell cycle regulation of the CLNs is also reduced, and the Start-dependence of HO transcription is eliminated. This indicates that Swi6 also plays an important role in the normal cell cycle regulation of all three promoters. When both Swi6 activity and the transcriptional regulation of SWI4 are eliminated, cell cycle regulation is further reduced, indicating that these are two independent pathways of regulation. However, a twofold fluctuation in transcript levels still persists under these conditions. This reveals a third source of cell cycle control, which could affect Swi4 activity post-transcriptionally, or reflect the existence of another unidentified regulator of these promoters. PMID:7896087

  2. Mechanisms of Physical-Biological-Biogeochemical Interaction at the Oceanic Mesoscale.

    PubMed

    McGillicuddy, Dennis J

    2016-01-01

    Mesoscale phenomena are ubiquitous and highly energetic features of ocean circulation. Their influence on biological and biogeochemical processes varies widely, stemming not only from advective transport but also from the generation of variations in the environment that affect biological and chemical rates. The ephemeral nature of mesoscale features in the ocean makes it difficult to elucidate the attendant mechanisms of physical-biological-biogeochemical interaction, necessitating the use of multidisciplinary approaches involving in situ observations, remote sensing, and modeling. All three aspects are woven through this review in an attempt to synthesize current understanding of the topic, with particular emphasis on novel developments in recent years. PMID:26359818

  3. Mechanisms of Physical-Biological-Biogeochemical Interaction at the Oceanic Mesoscale

    NASA Astrophysics Data System (ADS)

    McGillicuddy, Dennis J.

    2016-01-01

    Mesoscale phenomena are ubiquitous and highly energetic features of ocean circulation. Their influence on biological and biogeochemical processes varies widely, stemming not only from advective transport but also from the generation of variations in the environment that affect biological and chemical rates. The ephemeral nature of mesoscale features in the ocean makes it difficult to elucidate the attendant mechanisms of physical-biological-biogeochemical interaction, necessitating the use of multidisciplinary approaches involving in situ observations, remote sensing, and modeling. All three aspects are woven through this review in an attempt to synthesize current understanding of the topic, with particular emphasis on novel developments in recent years.

  4. Ovarian cycle-linked plasticity of δ-GABAA receptor subunits in hippocampal interneurons affects γ oscillations in vivo.

    PubMed

    Barth, Albert M I; Ferando, Isabella; Mody, Istvan

    2014-01-01

    GABAA receptors containing δ subunits (δ-GABAARs) are GABA-gated ion channels with extra- and perisynaptic localization, strong sensitivity to neurosteroids (NS), and a high degree of plasticity. In selective brain regions they are expressed on specific principal cells and interneurons (INs), and generate a tonic conductance that controls neuronal excitability and oscillations. Plasticity of δ-GABAARs in principal cells has been described during states of altered NS synthesis including acute stress, puberty, ovarian cycle, pregnancy and the postpartum period, with direct consequences on neuronal excitability and network dynamics. The defining network events implicated in cognitive function, memory formation and encoding are γ oscillations (30-120 Hz), a well-timed loop of excitation and inhibition between principal cells and PV-expressing INs (PV + INs). The δ-GABAARs of INs can modify γ oscillations, and a lower expression of δ-GABAARs on INs during pregnancy alters γ frequency recorded in vitro. The ovarian cycle is another physiological event with large fluctuations in NS levels and δ-GABAARs. Stages of the cycle are paralleled by swings in memory performance, cognitive function, and mood in both humans and rodents. Here we show δ-GABAARs changes during the mouse ovarian cycle in hippocampal cell types, with enhanced expression during diestrus in principal cells and specific INs. The plasticity of δ-GABAARs on PV-INs decreases the magnitude of γ oscillations continuously recorded in area CA1 throughout several days in vivo during diestrus and increases it during estrus. Such recurring changes in γ magnitude were not observed in non-cycling wild-type (WT) females, cycling females lacking δ-GABAARs only on PV-INs (PV-Gabrd (-/-)), and in male mice during a time course equivalent to the ovarian cycle. Our findings may explain the impaired memory and cognitive performance experienced by women with premenstrual syndrome (PMS) or premenstrual dysphoric

  5. Biogeochemical factors which regulate the formation and fate of sulfide in wetlands

    NASA Technical Reports Server (NTRS)

    Hines, Mark E.; Lyons, W. Berry; Gaudette, H. E.

    1992-01-01

    Coastal wetland areas occupy a small percentage of the terrestrial environment yet are extremely productive regions which support rapid rates of belowground bacterial activity. Wetlands appear to be significant as biogenic sources of gaseous sulfur, carbon, and nitrogen. These gases are important as tracers of man's activities, and they influence atmospheric chemistry. The interactions among wetland biogeochemical processes regulate the anaerobic production of reduced gases and influence the fate of these volatiles. Therefore, spatial and temporal variations in hydrology, salinity, temperature and specification, and growth of vegetation affect the type and magnitude of gas emissions thus hindering predictive estimates of gas flux. Our research is divided into two major components, the first is the biogeochemical characterization of a selected tidal wetland area in terms of factors likely to regulate sulfide flux; the second is a direct measurement of gaseous sulfur flux as related to changes in these biogeochemical conditions. Presently, we are near completion of phase one.

  6. BIOGEOCHEMICAL STUDIES OF PHOTOSYNTHETIC MICROBIAL MATS AND THEIR BIOTA

    NASA Technical Reports Server (NTRS)

    DesMarais, David; Discipulo, M.; Turk, K.; Londry, K. L.

    2005-01-01

    Photosynthetic microbial mats offer an opportunity to define holistic functionality at the millimeter scale. At the same time. their biogeochemistry contributes to environmental processes on a planetary scale. These mats are possibly direct descendents of the most ancient biological communities; communities in which oxygenic photosynthesis might have been invented. Mats provide one of the best natural systems to study how microbial populations associate to control dynamic biogeochemical gradients. These are self- sustaining, complete ecosystems in which light energy absorbed over a dial (24 hour) cycle drives the synthesis of spatially-organized, diverse biomass. Tightly-coupled microorganisms in the mat have specialized metabolisms that catalyze transformations of carbon, nitrogen, sulfur, and a host of other elements.

  7. Coupling a terrestrial biogeochemical model to the common land model

    SciTech Connect

    Shi, Xiaoying; Mao, Jiafu; Wang, Yingping; Dai, Yongjiu; Tang, Xuli

    2011-01-01

    A terrestrial biogeochemical model (CASACNP) was coupled to a land surface model (the Common Land Model, CoLM) to simulate the dynamics of carbon substrate in soil and its limitation on soil respiration. The combined model, CoLM-CASACNP, was able to predict long-term carbon sources and sinks that CoLM alone could not. The coupled model was tested using measurements of belowground respiration and surface fluxes from two forest ecosystems. The combined model simulated reasonably well the diurnal and seasonal variations of net ecosystem carbon exchange, as well as seasonal variation in the soil respiration rate of both the forest sites chosen for this study. However, the agreement between model simulations and actual measurements was poorer under dry conditions. The model should be tested against more measurements before being applied globally to investigate the feedbacks between the carbon cycle and climate change.

  8. Reconstructing disturbances and their biogeochemical consequences over multiple timescales

    USGS Publications Warehouse

    McLauchlan, Kendra K.; Higuera, Philip E.; Gavin, Daniel G.; Perakis, Steven S.; Mack, Michelle C.; Alexander, Heather; Battles, John; Biondi, Franco; Buma, Brian; Colombaroli, Daniele; Enders, Sara K.; Engstrom, Daniel R.; Hu, Feng Sheng; Marlon, Jennifer R.; Marshall, John; McGlone, Matt; Morris, Jesse L.; Nave, Lucas E.; Shuman, Bryan; Smithwick, Erica A.H.; Urrego, Dunia H.; Wardle, David A.; Williams, Christopher J.; Williams, Joseph J.

    2014-01-01

    Ongoing changes in disturbance regimes are predicted to cause acute changes in ecosystem structure and function in the coming decades, but many aspects of these predictions are uncertain. A key challenge is to improve the predictability of postdisturbance biogeochemical trajectories at the ecosystem level. Ecosystem ecologists and paleoecologists have generated complementary data sets about disturbance (type, severity, frequency) and ecosystem response (net primary productivity, nutrient cycling) spanning decadal to millennial timescales. Here, we take the first steps toward a full integration of these data sets by reviewing how disturbances are reconstructed using dendrochronological and sedimentary archives and by summarizing the conceptual frameworks for carbon, nitrogen, and hydrologic responses to disturbances. Key research priorities include further development of paleoecological techniques that reconstruct both disturbances and terrestrial ecosystem dynamics. In addition, mechanistic detail from disturbance experiments, long-term observations, and chronosequences can help increase the understanding of ecosystem resilience.

  9. A GIS approach to conducting biogeochemical research in wetlands

    NASA Technical Reports Server (NTRS)

    Brannon, David P.; Irish, Gary J.

    1985-01-01

    A project was initiated to develop an environmental data base to address spatial aspects of both biogeochemical cycling and resource management in wetlands. Specific goals are to make regional methane flux estimates and site specific water level predictions based on man controlled water releases within a wetland study area. The project will contribute to the understanding of the Earth's biosphere through its examination of the spatial variability of methane emissions. Although wetlands are thought to be one of the primary sources for release of methane to the atmosphere, little is known about the spatial variability of methane flux. Only through a spatial analysis of methane flux rates and the environmental factors which influence such rates can reliable regional and global methane emissions be calculated. Data will be correlated and studied from Landsat 4 instruments, from a ground survey of water level recorders, precipitation recorders, evaporation pans, and supplemental gauges, and from flood gate water release; and regional methane flux estimates will be made.

  10. Nitrogen cycling responses to mountain pine beetle disturbance in a high elevation whitebark pine ecosystem

    USGS Publications Warehouse

    Keville, Megan P.; Reed, Sasha C.; Cleveland, Cory C.

    2013-01-01

    Ecological disturbances can significantly affect biogeochemical cycles in terrestrial ecosystems, but the biogeochemical consequences of the extensive mountain pine beetle outbreak in high elevation whitebark pine (WbP) (Pinus albicaulis) ecosystems of western North America have not been previously investigated. Mountain pine beetle attack has driven widespread WbP mortality, which could drive shifts in both the pools and fluxes of nitrogen (N) within these ecosystems. Because N availability can limit forest regrowth, understanding how beetle-induced mortality affects N cycling in WbP stands may be critical to understanding the trajectory of ecosystem recovery. Thus, we measured above- and belowground N pools and fluxes for trees representing three different times since beetle attack, including unattacked trees. Litterfall N inputs were more than ten times higher under recently attacked trees compared to unattacked trees. Soil inorganic N concentrations also increased following beetle attack, potentially driven by a more than two-fold increase in ammonium (NH4+) concentrations in the surface soil organic horizon. However, there were no significant differences in mineral soil inorganic N or soil microbial biomass N concentrations between attacked and unattacked trees, implying that short-term changes in N cycling in response to the initial stages of WbP attack were restricted to the organic horizon. Our results suggest that while mountain pine beetle attack drives a pulse of N from the canopy to the forest floor, changes in litterfall quality and quantity do not have profound effects on soil biogeochemical cycling, at least in the short-term. However, continuous observation of these important ecosystems will be crucial to determining the long-term biogeochemical effects of mountain pine beetle outbreaks.

  11. Life cycle assessment of lignocellulosic ethanol: a review of key factors and methods affecting calculated GHG emissions and energy use.

    PubMed

    Gerbrandt, Kelsey; Chu, Pei Lin; Simmonds, Allison; Mullins, Kimberley A; MacLean, Heather L; Griffin, W Michael; Saville, Bradley A

    2016-04-01

    Lignocellulosic ethanol has potential for lower life cycle greenhouse gas emissions compared to gasoline and conventional grain-based ethanol. Ethanol production 'pathways' need to meet economic and environmental goals. Numerous life cycle assessments of lignocellulosic ethanol have been published over the last 15 years, but gaps remain in understanding life cycle performance due to insufficient data, and model and methodological issues. We highlight key aspects of these issues, drawing on literature and a case study of corn stover ethanol. Challenges include the complexity of feedstock/ecosystems and market-mediated aspects and the short history of commercial lignocellulosic ethanol facilities, which collectively have led to uncertainty in GHG emissions estimates, and to debates on LCA methods and the role of uncertainty in decision making. PMID:26807514

  12. PFLOTRAN: Recent Developments Facilitating Massively-Parallel Reactive Biogeochemical Transport

    NASA Astrophysics Data System (ADS)

    Hammond, G. E.

    2015-12-01

    With the recent shift towards modeling carbon and nitrogen cycling in support of climate-related initiatives, emphasis has been placed on incorporating increasingly mechanistic biogeochemistry within Earth system models to more accurately predict the response of terrestrial processes to natural and anthropogenic climate cycles. PFLOTRAN is an open-source subsurface code that is specialized for simulating multiphase flow and multicomponent biogeochemical transport on supercomputers. The object-oriented code was designed with modularity in mind and has been coupled with several third-party simulators (e.g. CLM to simulate land surface processes and E4D for coupled hydrogeophysical inversion). Central to PFLOTRAN's capabilities is its ability to simulate tightly-coupled reactive transport processes. This presentation focuses on recent enhancements to the code that enable the solution of large parameterized biogeochemical reaction networks with numerous chemical species. PFLOTRAN's "reaction sandbox" is described, which facilitates the implementation of user-defined reaction networks without the need for a comprehensive understanding of PFLOTRAN software infrastructure. The reaction sandbox is written in modern Fortran (2003-2008) and leverages encapsulation, inheritance, and polymorphism to provide the researcher with a flexible workspace for prototyping reactions within a massively parallel flow and transport simulation framework. As these prototypical reactions mature into well-accepted implementations, they can be incorporated into PFLOTRAN as native biogeochemistry capability. Users of the reaction sandbox are encouraged to upload their source code to PFLOTRAN's main source code repository, including the addition of simple regression tests to better ensure the long-term code compatibility and validity of simulation results.

  13. Nitrogen and Sulfur Deposition Effects on Forest Biogeochemical Processes.

    NASA Astrophysics Data System (ADS)

    Goodale, C. L.

    2014-12-01

    Chronic atmospheric deposition of nitrogen and sulfur have widely ranging biogeochemical consequences in terrestrial ecosystems. Both N and S deposition can affect plant growth, decomposition, and nitrous oxide production, with sometimes synergistic and sometimes contradictory responses; yet their separate effects are rarely isolated and their interactive biogeochemical impacts are often overlooked. For example, S deposition and consequent acidification and mortality may negate stimulation of plant growth induced by N deposition; decomposition can be slowed by both N and S deposition, though through different mechanisms; and N2O production may be stimulated directly by N and indirectly by S amendments. Recent advances in conceptual models and whole-ecosystem experiments provide novel means for disentangling the impacts of N and S in terrestrial ecosystems. Results from a new whole-ecosystem N x S- addition experiment will be presented in detail, examining differential response of tree and soil carbon storage to N and S additions. These results combine with observations from a broad array of long-term N addition studies, atmospheric deposition gradients, stable isotope tracer studies, and model analyses to inform the magnitude, controls, and stability of ecosystem C storage in response to N and S addition.

  14. Hydro-biogeochemical Controls on Geophysical Signatures (Invited)

    NASA Astrophysics Data System (ADS)

    Atekwana, E. A.

    2013-12-01

    Geophysical techniques such as seismic, magnetic and electrical techniques have historically played a major role in oil exploration. Their main use has been for delineation basin geometry, structures and hydrocarbon traps and for understanding the subsurface stratigraphy. Their use for investigating microbial processes has only recently been recognized over the last decade resulting in the development of biogeophysics as a frontier research area which bridges the fields of environmental microbiology, biogeochemistry, geomicrobiology. Recent biogeophysical studies have demonstrated the potential of geophysical technologies to (1) probe the presence of microbial cells and biofilms in subsurface geologic media, (2) investigate the interactions between microorganisms and subsurface geologic media, (3) assess biogeochemical transformations, biomineralization, and biogeochemical reaction rates, and (4) investigate the alteration of physical properties of subsurface geologic media induced by microorganisms. The unique properties of geophysical datasets (e.g. non-invasive data acquisition, spatially continuous properties retrieved) make them attractive for probing microbial processes affecting fate and transport of contaminants. This presentation will provide an updated understanding of major controls on geophysical signatures by highlighting some of the important advancements in biogeophysical studies at hydrocarbon contaminated environments. Important challenges that provide an opportunity for further research in this new field will also be examined.

  15. How do changes in the Diurnal Cycle affect Bi-stability and Climate Sensitivity in the Habitable Zone?

    NASA Astrophysics Data System (ADS)

    Boschi, R.; Valerio, L.

    2013-09-01

    In this study we deal with the effect of varying the length of the diurnal cycle on its bi-stability properties. By using a general circulation model, PlaSim, we consider several values for the diurnal cycle, from tidally locked, to that of 1 Earth day. For each value of the diurnal cycle, we slowly modulate the solar constant between 1510 and 1000 Wm-2 and perform a hysteresis experiment. It is found that the width of the bi-stable region, i.e. the range of climate states - determined here by changes in S* - which support two climatic attractors, reduces when the diurnal cycle is increased in length and disappears - signifying the merging of both attractors - for climates with a diurnal cycle greater than 180 days. Crucial to the loss of bi-stability is the longitudinally asymmetric distribution of solar radiation, incident on the planet's surface, leading to the development of equatorial sea-ice. For diurnal cycles where bi-stability is found, the longitudinally asymmetric heating is sufficiently compensated for by the strength of the zonal winds and the rate of solar distribution, which redistribute heat and maintain the meridional temperature gradient across all longitudes. Conversely, for mono-stable regimes, the energy transport associated with zonal winds becomes insufficient to compensate for the increase in the length of the diurnal cycle, resulting in large zonal temperature gradients along the equatorial band. Furthermore, the results found here confirm and reenforce the robustness of those found in Boschi et al (2013), showing that, for climates which support bistability, it may be possible to parameterise variables such as the material entropy production and the meridional heat transport in terms of the surface and emission temperatures, within reasonably well defined upper and lower bounds, even when considering a wide range of planetary rotation speeds and changes to the infrared opacity. This paves the way for the possibility of practically deducing

  16. Thermodynamic constraints on the utility of ecological stoichiometry for explaining global biogeochemical patterns.

    PubMed

    Helton, Ashley M; Ardón, Marcelo; Bernhardt, Emily S

    2015-10-01

    Carbon and nitrogen cycles are coupled through both stoichiometric requirements for microbial biomass and dissimilatory metabolic processes in which microbes catalyse reduction-oxidation reactions. Here, we integrate stoichiometric theory and thermodynamic principles to explain the commonly observed trade-off between high nitrate and high organic carbon concentrations, and the even stronger trade-off between high nitrate and high ammonium concentrations, across a wide range of aquatic ecosystems. Our results suggest these relationships are the emergent properties of both microbial biomass stoichiometry and the availability of terminal electron acceptors. Because elements with multiple oxidation states (i.e. nitrogen, manganese, iron and sulphur) serve as both nutrients and sources of chemical energy in reduced environments, both assimilative demand and dissimilatory uses determine their concentrations across broad spatial gradients. Conceptual and quantitative models that integrate rather than independently examine thermodynamic, stoichiometric and evolutionary controls on biogeochemical cycling are essential for understanding local to global biogeochemical patterns. PMID:26259672

  17. Treating cattle with progesterone as well as a GnRH analogue affects oestrous cycle length and fertility.

    PubMed

    Lynch, P R; Macmillan, K L; Taufa, V K

    1999-08-16

    Initiating the chronic administration of progesterone to cattle during metoestrus will produce shortened oestrous cycles containing one or two wave-like sequences of ovarian follicle development. Conception rates are reduced to inseminations at the oestrus preceding these shortened cycles. In contrast, a single injection of the GnRH analogue, buserelin, around mid-dioestrus can lengthen the oestrous cycle by increasing the proportion of cycles with three waves of follicular development and may also increase conception rates. A series of trials was conducted to test the hypothesis that the adverse effects of progesterone on oestrous cycle length and conception rate could be prevented with a strategic injection of GnRH. In Trial 1, progesterone was administered per vaginum to heifers for 10 days from Day 2 or 3 (Oestrus = Day 0) and with (n = 42) or without (n = 46) an injection of a GnRH analogue (10 microg buserelin) on Day 12 or 13. Other heifers (n = 44) served as an untreated control group. The average inter-oestrous interval (IOI) for those heifers treated only with progesterone was 17.0 days and was less (p<0.05) than the average intervals for those also receiving GnRH (20.2 days) or in the control group (20.0 days). In Trial 2, 45 heifers were inseminated following a synchronised oestrus. Progesterone was administered as in Trial 1 to 22 of the heifers. Their conception rate was 45.4% and this was less (p<0.05) than the 73.9% obtained with their 23 untreated contemporaries. Trial 3 was completed using 530 cows in commercial dairyherds. The 259 cows receiving progesterone and GnRH (buserelin) after their first inseminations had a conception rate of 68.3% compared to 56.1% for their 271 untreated herdmates (p<0.05%). Heifer calves born to treated cows had heavier birthweights (33.4 vs. 31.1 kg; p<0.05), but birthweights of bull calves were unaffected (35.5 vs. 35.8 kg). Gestation lengths for cows conceiving to first inseminations were similar for treated and

  18. Do antibiotics have environmental side-effects? Impact of synthetic antibiotics on biogeochemical processes.

    PubMed

    Roose-Amsaleg, Céline; Laverman, Anniet M

    2016-03-01

    Antibiotic use in the early 1900 vastly improved human health but at the same time started an arms race of antibiotic resistance. The widespread use of antibiotics has resulted in ubiquitous trace concentrations of many antibiotics in most environments. Little is known about the impact of these antibiotics on microbial processes or "non-target" organisms. This mini-review summarizes our knowledge of the effect of synthetically produced antibiotics on microorganisms involved in biogeochemical cycling. We found only 31 articles that dealt with the effects of antibiotics on such processes in soil, sediment, or freshwater. We compare the processes, antibiotics, concentration range, source, environment, and experimental approach of these studies. Examining the effects of antibiotics on biogeochemical processes should involve environmentally relevant concentrations (instead of therapeutic), chronic exposure (versus acute), and monitoring of the administered antibiotics. Furthermore, the lack of standardized tests hinders generalizations regarding the effects of antibiotics on biogeochemical processes. We investigated the effects of antibiotics on biogeochemical N cycling, specifically nitrification, denitrification, and anammox. We found that environmentally relevant concentrations of fluoroquinolones and sulfonamides could partially inhibit denitrification. So far, the only documented effects of antibiotic inhibitions were at therapeutic doses on anammox activities. The most studied and inhibited was nitrification (25-100 %) mainly at therapeutic doses and rarely environmentally relevant. We recommend that firm conclusions regarding inhibition of antibiotics at environmentally relevant concentrations remain difficult due to the lack of studies testing low concentrations at chronic exposure. There is thus a need to test the effects of these environmental concentrations on biogeochemical processes to further establish the possible effects on ecosystem functioning. PMID

  19. Lower temperature during the dark cycle affects disease development on Lygodium microphyllum (Old World climbing fern) by Bipolaris sacchari

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Growth chamber studies were conducted to examine environmental parameters affecting disease development by the indigenous pathogen Bipolaris sacchari isolate LJB-1L on the invasive weed Lygodium microphyllum (Old World climbing fern). Initial studies examined three different temperature regimes (20...

  20. High-Cycle Fatigue Resistance of Si-Mo Ductile Cast Iron as Affected by Temperature and Strain Rate

    NASA Astrophysics Data System (ADS)

    Matteis, Paolo; Scavino, Giorgio; Castello, Alessandro; Firrao, Donato

    2015-09-01

    Silicon-molybdenum ductile cast irons are used to fabricate exhaust manifolds of internal combustion engines of large series cars, where the maximum pointwise temperature at full engine load may be higher than 973 K (700 °C). In this application, high-temperature oxidation and thermo-mechanical fatigue (the latter being caused by the engine start and stop and by the variation of its power output) have been the subject of several studies and are well known, whereas little attention has been devoted to the high-cycle fatigue, arising from the engine vibration. Therefore, the mechanical behavior of Si-Mo cast iron is studied here by means of stress-life fatigue tests up to 10 million cycles, at temperatures gradually increasing up to 973 K (700 °C). The mechanical characterization is completed by tensile and compressive tests and ensuing fractographic examinations; the mechanical test results are correlated with the cast iron microstructure and heat treatment.

  1. How does the exchange of one oxygen atom with sulfur affect the catalytic cycle of carbonic anhydrase?

    PubMed

    Schenk, Stephan; Kesselmeier, Jürgen; Anders, Ernst

    2004-06-21

    We have extended our investigations of the carbonic anhydrase (CA) cycle with the model system [(H(3)N)(3)ZnOH](+) and CO(2) by studying further heterocumulenes and catalysts. We investigated the hydration of COS, an atmospheric trace gas. This reaction plays an important role in the global COS cycle since biological consumption, that is, uptake by higher plants, algae, lichens, and soil, represents the dominant terrestrial sink for this gas. In this context, CA has been identified by a member of our group as the key enzyme for the consumption of COS by conversion into CO(2) and H(2)S. We investigated the hydration mechanism of COS by using density functional theory to elucidate the details of the catalytic cycle. Calculations were first performed for the uncatalyzed gas phase reaction. The rate-determining step for direct reaction of COS with H(2)O has an energy barrier of deltaG=53.2 kcal mol(-1). We then employed the CA model system [(H(3)N)(3)ZnOH](+) (1) and studied the effect on the catalytic hydration mechanism of replacing an oxygen atom with sulfur. When COS enters the carbonic anhydrase cycle, the sulfur atom is incorporated into the catalyst to yield [(H(3)N)(3)ZnSH](+) (27) and CO(2). The activation energy of the nucleophilic attack on COS, which is the rate-determining step, is somewhat higher (20.1 kcal mol(-1) in the gas phase) than that previously reported for CO(2). The sulfur-containing model 27 is also capable of catalyzing the reaction of CO(2) to produce thiocarbonic acid. A larger barrier has to be overcome for the reaction of 27 with CO(2) compared to that for the reaction of 1 with CO(2). At a well-defined stage of this cycle, a different reaction path can emerge: a water molecule helps to regenerate the original catalyst 1 from 27, a process accompanied by the formation of thiocarbonic acid. We finally demonstrate that nature selected a surprisingly elegant and efficient group of reactants, the [L(3)ZnOH](+)/CO(2)/H(2)O system, that helps

  2. Form of supplemental selenium fed to cycling cows affects systemic concentrations of progesterone but not those of estradiol.

    PubMed

    Cerny, Katheryn L; Anderson, Les; Burris, Walter R; Rhoads, Michelle; Matthews, James C; Bridges, Phillip J

    2016-03-15

    In areas where soils are deficient in selenium (Se), dietary supplementation of this trace mineral directly to cattle is recommended. Selenium status affects fertility, and the form of Se supplemented to cows affects tissue-specific gene expression profiles. The objective of this study was to determine whether the form of Se consumed by cows would affect follicular growth and the production of steroids. Thirty-three Angus-cross cows that had ad libitum access of a mineral mix containing 35 ppm of Se in free-choice vitamin-mineral mixes as either inorganic (ISe), organic (OSe), or a 50/50 mix of ISe and OSe (MIX) for 180 days were used. After 170 days of supplementation, all cows were injected with 25-mg PGF2α to induce regression of the CL and then monitored for behavioral estrus (Day 0). From Day 4 to Day 8 after estrus, follicular growth was determined by transrectal ultrasonography. On Day 6, cows were injected with PGF2α (20 then 15 mg, 8-12 hours apart) to induce regression of the developing CL and differentiation of the dominant follicle of the first follicular wave into a preovulatory follicle. On Day 8, 36 hours after PGF2α (20 mg), the contents of the preovulatory follicle were aspirated by ultrasound-guided follicular puncture. Blood collected on Days 6 and 8 and follicular fluid collected on Day 8 was analyzed for concentrations of progesterone and estradiol. Form of Se supplemented to cows affected (P = 0.04) the systemic concentration of progesterone on Day 6, but not on Day 8. Form of Se did not affect the systemic concentration of estradiol on Day 6 or Day 8. Form of Se tended to affect (P = 0.07) the concentration of progesterone, but not that of estradiol, in the follicular fluid. Form of Se did not affect diameter of the dominant ovarian follicle on Days 4 to 6, but tended to affect (P = 0.08) the diameter of the preovulatory follic