WorldWideScience

Sample records for biogeochemistry

  1. Global Methane Biogeochemistry

    Science.gov (United States)

    Reeburgh, W. S.

    2003-12-01

    . Methane absorbs infrared radiation in the troposphere, as do CO2 and H2O, and is an important greenhouse gas (Lacis et al., 1981; Ramanathan et al., 1985).A number of review articles on atmospheric CH4 have appeared during the last 15 years. Cicerone and Oremland (1988) reviewed evidence for the temporal atmospheric increase, updated source estimates in the global CH4 budget, and placed constraints on the global budget, emphasizing that the total is well constrained, but that the constituent sources may be uncertain by a factor of 2 or more. This paper was part of a special section in Global Biogeochemical Cycles that resulted from a 1987 American Chemical Society Symposium, "Atmospheric Methane: Formation and Fluxes form the Biosphere and Geosphere." Tyler (1991) and Wahlen (1993) emphasized new information on stable isotopes of CH4 and 14CH4, respectively. Several reviews deal with the microbially mediated CH4 oxidation. King (1992) reviewed the ecology of microbial CH4 oxidation, emphasizing the important role of this process in global CH4 dynamics. R. S. Hanson and T. E. Hanson (1996) reviewed the physiology and taxonomy of methylotrophic bacteria, their role in the global carbon cycle, and the ecology of methanotrophic bacteria. Conrad (1996) reviewed the role of soils and soil microbial communities as controllers of CH4 fluxes, as well as those of H2, CO, OCS, N2O, and NO. Two meetings focusing on CH4 biogeochemistry were held in 1991: an NATO Advanced Science Workshop held at Mt. Hood, OR, and the Tenth International Symposium on Environmental Biogeochemistry (ISEB). A dedicated issue of Chemosphere (26(1-4), 1993) contains contributions from the NATO workshop; two additional volumes (Khalil, 1993 and Khalil, 2000) contain a report of the workshop and updates of important topics. Contributions to the ISEB meeting are presented in Oremland (1993). Wuebbles and Hayhoe (2002) reviewed the effects of CH4 on atmospheric chemistry and examined the direct and indirect

  2. The ecology and biogeochemistry of stream biofilms.

    Science.gov (United States)

    Battin, Tom J; Besemer, Katharina; Bengtsson, Mia M; Romani, Anna M; Packmann, Aaron I

    2016-04-01

    Streams and rivers form dense networks, shape the Earth's surface and, in their sediments, provide an immensely large surface area for microbial growth. Biofilms dominate microbial life in streams and rivers, drive crucial ecosystem processes and contribute substantially to global biogeochemical fluxes. In turn, water flow and related deliveries of nutrients and organic matter to biofilms constitute major constraints on microbial life. In this Review, we describe the ecology and biogeochemistry of stream biofilms and highlight the influence of physical and ecological processes on their structure and function. Recent advances in the study of biofilm ecology may pave the way towards a mechanistic understanding of the effects of climate and environmental change on stream biofilms and the biogeochemistry of stream ecosystems.

  3. Tenth international symposium on environmental biogeochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Ehrlich, H.L.

    1992-01-01

    The primary task of this Symposium on Environmental Biogeochemistry was to examine our current understanding of GLOBAL CHANGE AND THE BIOGEOCHEMISTRY OF RADIATIVE TRACE GASES. The symposium was divided into 12 non-overlapping sessions: Paleoatmospheres and paleoclimates; Global distributions and atmospheric reactions; Poster presentations on the topics of sessions 1, 2, 4, 5, and 7; Terrestrial systems and land use change - 1; Terrestrial and land use change - 11; Fluxes and cycling in aquatic systems; Metals, organics, and depositional environments; Poster presentations on the topics of sessions 6, 9, 10 and 12; Biological Mechanisms of formation and destruction - 1; Biological mechanisms of formation and destruction - 11; High latitude systems; and Global sources, sinks, and feedbacks.

  4. Sea Ice Biogeochemistry: A Guide for Modellers

    Science.gov (United States)

    Tedesco, Letizia; Vichi, Marcello

    2014-01-01

    Sea ice is a fundamental component of the climate system and plays a key role in polar trophic food webs. Nonetheless sea ice biogeochemical dynamics at large temporal and spatial scales are still rarely described. Numerical models may potentially contribute integrating among sparse observations, but available models of sea ice biogeochemistry are still scarce, whether their relevance for properly describing the current and future state of the polar oceans has been recently addressed. A general methodology to develop a sea ice biogeochemical model is presented, deriving it from an existing validated model application by extension of generic pelagic biogeochemistry model parameterizations. The described methodology is flexible and considers different levels of ecosystem complexity and vertical representation, while adopting a strategy of coupling that ensures mass conservation. We show how to apply this methodology step by step by building an intermediate complexity model from a published realistic application and applying it to analyze theoretically a typical season of first-year sea ice in the Arctic, the one currently needing the most urgent understanding. The aim is to (1) introduce sea ice biogeochemistry and address its relevance to ocean modelers of polar regions, supporting them in adding a new sea ice component to their modelling framework for a more adequate representation of the sea ice-covered ocean ecosystem as a whole, and (2) extend our knowledge on the relevant controlling factors of sea ice algal production, showing that beyond the light and nutrient availability, the duration of the sea ice season may play a key-role shaping the algal production during the on going and upcoming projected changes. PMID:24586604

  5. Sea ice biogeochemistry: a guide for modellers.

    Science.gov (United States)

    Tedesco, Letizia; Vichi, Marcello

    2014-01-01

    Sea ice is a fundamental component of the climate system and plays a key role in polar trophic food webs. Nonetheless sea ice biogeochemical dynamics at large temporal and spatial scales are still rarely described. Numerical models may potentially contribute integrating among sparse observations, but available models of sea ice biogeochemistry are still scarce, whether their relevance for properly describing the current and future state of the polar oceans has been recently addressed. A general methodology to develop a sea ice biogeochemical model is presented, deriving it from an existing validated model application by extension of generic pelagic biogeochemistry model parameterizations. The described methodology is flexible and considers different levels of ecosystem complexity and vertical representation, while adopting a strategy of coupling that ensures mass conservation. We show how to apply this methodology step by step by building an intermediate complexity model from a published realistic application and applying it to analyze theoretically a typical season of first-year sea ice in the Arctic, the one currently needing the most urgent understanding. The aim is to (1) introduce sea ice biogeochemistry and address its relevance to ocean modelers of polar regions, supporting them in adding a new sea ice component to their modelling framework for a more adequate representation of the sea ice-covered ocean ecosystem as a whole, and (2) extend our knowledge on the relevant controlling factors of sea ice algal production, showing that beyond the light and nutrient availability, the duration of the sea ice season may play a key-role shaping the algal production during the on going and upcoming projected changes.

  6. Sea ice biogeochemistry: a guide for modellers.

    Directory of Open Access Journals (Sweden)

    Letizia Tedesco

    Full Text Available Sea ice is a fundamental component of the climate system and plays a key role in polar trophic food webs. Nonetheless sea ice biogeochemical dynamics at large temporal and spatial scales are still rarely described. Numerical models may potentially contribute integrating among sparse observations, but available models of sea ice biogeochemistry are still scarce, whether their relevance for properly describing the current and future state of the polar oceans has been recently addressed. A general methodology to develop a sea ice biogeochemical model is presented, deriving it from an existing validated model application by extension of generic pelagic biogeochemistry model parameterizations. The described methodology is flexible and considers different levels of ecosystem complexity and vertical representation, while adopting a strategy of coupling that ensures mass conservation. We show how to apply this methodology step by step by building an intermediate complexity model from a published realistic application and applying it to analyze theoretically a typical season of first-year sea ice in the Arctic, the one currently needing the most urgent understanding. The aim is to (1 introduce sea ice biogeochemistry and address its relevance to ocean modelers of polar regions, supporting them in adding a new sea ice component to their modelling framework for a more adequate representation of the sea ice-covered ocean ecosystem as a whole, and (2 extend our knowledge on the relevant controlling factors of sea ice algal production, showing that beyond the light and nutrient availability, the duration of the sea ice season may play a key-role shaping the algal production during the on going and upcoming projected changes.

  7. Sulfur biogeochemistry of oil sands composite tailings

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Lesley; Stephenson, Kate [Earth Sciences, McMaster University (Canada)], email: warrenl@mcmaster.ca; Penner, Tara [Syncrude Environmental Research (Canada)

    2011-07-01

    This paper discusses the sulfur biogeochemistry of oil sands composite tailings (CT). The Government of Alberta is accelerating reclamation activities on composite tailings. As a CT pilot reclamation operation, Syncrude is currently constructing the first freshwater fen. Minor unpredicted incidents with H2S gas released from the dewatering process associated with these reclamations have been reported. The objective of this study is to ascertain the connection between microbial activity and H2S generation within CT and to assess the sulfur biogeochemistry of untreated and treated (fen) CT over seasonal and annual timescales. The microbial geochemical interactions taking place are shown using a flow chart. CT is composed of gypsum, sand, clay and organics like naphthenic acids and bitumen. Sulfur and Fe cycling in mining systems and their microbial activities are presented. The chemistry and the processes involved within CT are also given along with the results. It can be said that the diverse Fe and S metabolizing microorganisms confirm the ecology involved in H2S dynamics.

  8. Global Ocean Carbon and Biogeochemistry Coordination

    Science.gov (United States)

    Telszewski, Maciej; Tanhua, Toste; Palacz, Artur

    2016-04-01

    The complexity of the marine carbon cycle and its numerous connections to carbon's atmospheric and terrestrial pathways means that a wide range of approaches have to be used in order to establish it's qualitative and quantitative role in the global climate system. Ocean carbon and biogeochemistry research, observations, and modelling are conducted at national, regional, and global levels to quantify the global ocean uptake of atmospheric CO2 and to understand controls of this process, the variability of uptake and vulnerability of carbon fluxes into the ocean. These science activities require support by a sustained, international effort that provides a central communication forum and coordination services to facilitate the compatibility and comparability of results from individual efforts and development of the ocean carbon data products that can be integrated with the terrestrial, atmospheric and human dimensions components of the global carbon cycle. The International Ocean Carbon Coordination Project (IOCCP) was created in 2005 by the IOC of UNESCO and the Scientific Committee on Oceanic Research. IOCCP provides an international, program-independent forum for global coordination of ocean carbon and biogeochemistry observations and integration with global carbon cycle science programs. The IOCCP coordinates an ever-increasing set of observations-related activities in the following domains: underway observations of biogeochemical water properties, ocean interior observations, ship-based time-series observations, large-scale ocean acidification monitoring, inorganic nutrients observations, biogeochemical instruments and autonomous sensors and data and information creation. Our contribution is through the facilitation of the development of globally acceptable strategies, methodologies, practices and standards homogenizing efforts of the research community and scientific advisory groups as well as integrating the ocean biogeochemistry observations with the

  9. Computational Studies in Molecular Geochemistry and Biogeochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Felmy, Andrew R.; Bylaska, Eric J.; Dixon, David A.; Dupuis, Michel; Halley, James W.; Kawai, R.; Rosso, Kevin M.; Rustad, James R.; Smith, Paul E.; Straatsma, TP; Voth, Gregory A.; Weare, John H.; Yuen, David A.

    2006-04-18

    The ability to predict the transport and transformations of contaminants within the subsurface is critical for decisions on virtually every waste disposal option facing the Department of Energy (DOE), from remediation technologies such as in situ bioremediation to evaluations of the safety of nuclear waste repositories. With this fact in mind, the DOE has recently sponsored a series of workshops on the development of a Strategic Simulation Plan on applications of high perform-ance computing to national problems of significance to the DOE. One of the areas selected for application was in the area of subsurface transport and environmental chemistry. Within the SSP on subsurface transport and environmental chemistry several areas were identified where applications of high performance computing could potentially significantly advance our knowledge of contaminant fate and transport. Within each of these areas molecular level simulations were specifically identified as a key capability necessary for the development of a fundamental mechanistic understanding of complex biogeochemical processes. This effort consists of a series of specific molecular level simulations and program development in four key areas of geochemistry/biogeochemistry (i.e., aqueous hydrolysis, redox chemistry, mineral surface interactions, and microbial surface properties). By addressing these four differ-ent, but computationally related, areas it becomes possible to assemble a team of investigators with the necessary expertise in high performance computing, molecular simulation, and geochemistry/biogeochemistry to make significant progress in each area. The specific targeted geochemical/biogeochemical issues include: Microbial surface mediated processes: the effects of lipopolysacchardies present on gram-negative bacteria. Environmental redox chemistry: Dechlorination pathways of carbon tetrachloride and other polychlorinated compounds in the subsurface. Mineral surface interactions: Describing

  10. Wetland biogeochemistry and ecological risk assessment

    Science.gov (United States)

    Bai, Junhong; Huang, Laibin; Gao, Haifeng; Zhang, Guangliang

    2017-02-01

    Wetlands are an important ecotone between terrestrial and aquatic ecosystems and can provide great ecological service functions. Soils/sediments are one of the important components of wetland ecosystems, which support wetland plants and microorganisms and influence wetland productivity. Moreover, wetland soils/sediments serve as sources, sinks and transfers of carbon, nitrogen, phosphorus and chemical contaminants such as heavy metals. In natural wetland ecosystems, wetland soils/sediments play a great role in improving water quality as these chemical elements can be retained in wetland soils/sediments for a long time. Moreover, the biogeochemical processes of the abovementioned elements in wetland soils/sediments can drive wetland evolution and development, and their changes will considerably affect wetland ecosystem health. Therefore, a better understanding of wetland soil biogeochemistry will contribute to improving wetland ecological service functions.

  11. Everglqades Mercury: Biogeochemistry, Modeling, and Possible Mitigation

    Science.gov (United States)

    Orem, W. H.

    2015-12-01

    In the 1980s high levels of methylmercury (MeHg) were found in fish and other biota in the Florida Everglades, prompting fish consumption advisories. As part of Everglades restoration efforts Federal and State Agencies initiated a research program to study the underlying causes of the MeHg contamination. As part of this multi-agency effort, the U.S. Geological Survey developed the ACME (Aquatic Cycling of Mercury in the Everglades) project to examine the underlying biogeochemical factors controlling MeHg production and bioaccumulation in the ecosystem. Field studies by ACME and others identified the many factors impacting MeHg production in the Everglades. Thes factors include: high mercury deposition, large wetland area with organic-rich anaerobic soil, high sulfate loading in surface runoff, circumneutral pH, and high dissolved organic matter (DOM) content. Florida Department of Environmental Protection efforts that reduced local mercury emissions by 90%, produced only a small reduction in mercury deposition on the Everglades, suggesting that most Hg deposited on the ecosystem originates from distant sources, and beyond the reach of regulators. ACME studies demonstrated that high sulfate loading to the Everglades comes from discharge of canal water originating in the Everglades Agricultural Area (EAA). The use of sulfur in agriculture and soil oxidation in the EAA have been shown to be the principal sources of the sulfate loading. Sulfate entering the ecosystem drives microbial sulfate reduction and MeHg production, but inhibition of MeHg production by sulfide (a byproduct of microbial sulfate reduction) makes the biogeochemistry complex. Laboratory microcosm and field mesocosm experiments by ACME helped define the complexity of the sulfur/MeHg biogeochemistry, and demonstrated the key role of dissolved organic matter in MeHg production. A conceptual model was developed that relates MeHg production to sulfate loading, DOM, and soil composition. This conceptual

  12. Mesopelagic zone ecology and biogeochemistry - a synthesis

    Science.gov (United States)

    Robinson, Carol; Steinberg, Deborah K.; Anderson, Thomas R.; Arístegui, Javier; Carlson, Craig A.; Frost, Jessica R.; Ghiglione, Jean-François; Hernández-León, Santiago; Jackson, George A.; Koppelmann, Rolf; Quéguiner, Bernard; Ragueneau, Olivier; Rassoulzadegan, Fereidoun; Robison, Bruce H.; Tamburini, Christian; Tanaka, Tsuneo; Wishner, Karen F.; Zhang, Jing

    2010-08-01

    The mesopelagic zone is the oceanic region through which carbon and other elements must pass in order to reach deeper waters or the sea floor. However, the food web interactions that occur in the mesopelagic zone are difficult to measure and so, despite their crucial importance to global elemental cycles, are not very well known. Recent developments in technology and new approaches have advanced the study of the variability in and controls upon the distribution and diversity of organisms in the mesopelagic zone, including the roles of respiration, recycling, and repackaging of particulate and dissolved organic material. However, there are remarkably few syntheses of the ecology and biogeochemistry of the microbes and metazoa that permanently reside or habitually visit this 'twilight zone'. Without this synthesis, it is difficult to assess the impact of ongoing changes in ocean hydrography and chemistry, due to increasing atmospheric carbon dioxide levels, on the biological carbon pump. This paper reviews what is known about the distribution of microbes and metazoa in the mesopelagic zone in relation to their activity and impact on global biogeochemical cycles. Thus, gaps in our knowledge are identified and suggestions made for priority research programmes that will improve our ability to predict the effects of climate change on carbon sequestration.

  13. Interactions among hydrogeomorphology, vegetation, and nutrient biogeochemistry in floodplain ecosystems

    Science.gov (United States)

    Noe, G.B.

    2013-01-01

    Hydrogeomorphic, vegetative, and biogeochemical processes interact in floodplains resulting in great complexity that provides opportunities to better understand linkages among physical and biological processes in ecosystems. Floodplains and their associated river systems are structured by four dimensional gradients of hydrogeomorphology: longitudinal, lateral, vertical, and temporal components. These four dimensions create dynamic hydrologic and geomorphologic mosaics that have a large imprint on the vegetation and nutrient biogeochemistry of floodplains. Plant physiology, population dynamics, community structure, and productivity are all very responsive to floodplain hydrogeomorphology. The strength of this relationship between vegetation and hydrogeomorphology is evident in the use of vegetation as an indicator of hydrogeomorphic processes. However, vegetation also influences hydrogeomorphology by modifying hydraulics and sediment entrainment and deposition that typically stabilize geomorphic patterns. Nitrogen and phosphorus biogeochemistry commonly influence plant productivity and community composition, although productivity is not limited by nutrient availability in all floodplains. Conversely, vegetation influences nutrient biogeochemistry through direct uptake and storage as well as production of organic matter that regulates microbial biogeochemical processes. The biogeochemistries of nitrogen and phosphorus cycling are very sensitive to spatial and temporal variation in hydrogeomorphology, in particular floodplain wetness and sedimentation. The least studied interaction is the direct effect of biogeochemistry on hydrogeomorphology, but the control of nutrient availability over organic matter decomposition and thus soil permeability and elevation is likely important. Biogeochemistry also has the more documented but indirect control of hydrogeomorphology through regulation of plant biomass. In summary, the defining characteristics of floodplain ecosystems

  14. Developing an Ontology for Ocean Biogeochemistry Data

    Science.gov (United States)

    Chandler, C. L.; Allison, M. D.; Groman, R. C.; West, P.; Zednik, S.; Maffei, A. R.

    2010-12-01

    Semantic Web technologies offer great promise for enabling new and better scientific research. However, significant challenges must be met before the promise of the Semantic Web can be realized for a discipline as diverse as oceanography. Evolving expectations for open access to research data combined with the complexity of global ecosystem science research themes present a significant challenge, and one that is best met through an informatics approach. The Biological and Chemical Oceanography Data Management Office (BCO-DMO) is funded by the National Science Foundation Division of Ocean Sciences to work with ocean biogeochemistry researchers to improve access to data resulting from their respective programs. In an effort to improve data access, BCO-DMO staff members are collaborating with researchers from the Tetherless World Constellation (Rensselaer Polytechnic Institute) to develop an ontology that formally describes the concepts and relationships in the data managed by the BCO-DMO. The project required transforming a legacy system of human-readable, flat files of metadata to well-ordered controlled vocabularies to a fully developed ontology. To improve semantic interoperability, terms from the BCO-DMO controlled vocabularies are being mapped to controlled vocabulary terms adopted by other oceanographic data management organizations. While the entire process has proven to be difficult, time-consuming and labor-intensive, the work has been rewarding and is a necessary prerequisite for the eventual incorporation of Semantic Web tools. From the beginning of the project, development of the ontology has been guided by a use case based approach. The use cases were derived from data access related requests received from members of the research community served by the BCO-DMO. The resultant ontology satisfies the requirements of the use cases and reflects the information stored in the metadata database. The BCO-DMO metadata database currently contains information that

  15. Plant Biology and Biogeochemistry Department annual report 2000

    DEFF Research Database (Denmark)

    Kossmann, J.; Gissel Nielsen, G.; Nielsen, K.K.;

    2001-01-01

    The Department of Plant Biology and Biogeochemistry is engaged in basic and applied research to improve the scientific basis for developing new methods and technology for an environmentally benign industrial and agricultural production in the future. TheDepartment's expertise covers a wide range...

  16. Biogeochemistry of manganese in ferruginous Lake Matano, Indonesia

    DEFF Research Database (Denmark)

    Jones, CarriAyne; Crowe, Sean Andrew; Sturm, Arne

    2011-01-01

    This study explores Mn biogeochemistry in a stratified, ferruginous lake, a modern analogue to ferruginous oceans. Intense Mn cycling occurs in the chemocline where Mn is recycled at least 15 times before sedimentation. The product of biologically catalyzed Mn oxidation in Lake Matano is birnessi...

  17. Plant Biology and Biogeochemistry Department annual report 1999

    DEFF Research Database (Denmark)

    Jensen, A.; Gissel Nielsen, G.; Giese, H.;

    2000-01-01

    The Department of Plant Biology and Biogeochemistry is engaged in basic and applied research to improve the scientific knowledge of developing new methods and technology for the future environmentally benign industrial and agricultural production, thusexerting less stress and strain on the enviro......The Department of Plant Biology and Biogeochemistry is engaged in basic and applied research to improve the scientific knowledge of developing new methods and technology for the future environmentally benign industrial and agricultural production, thusexerting less stress and strain...... summarizes and highlights our results and achievements to give an idea of the research directions in theDepartment. Some 160 persons, including staff, undergraduate students, post-graduate scientists and visiting scientists from all over the world, address our research goals....

  18. The Biogeochemistry of Chromophoric Dissolved Organic Matter in Coastal Waters

    Science.gov (United States)

    2016-06-07

    The Biogeochemistry of Chromophoric Dissolved Organic Matter in Coastal Waters Robert F. Chen Environmental , Coastal and Ocean Sciences University of...properties to governing physical processes in high energy environments such as coastal seas. In addition, large spatial coverage over a wide range of...optical measurements of CDOM. In order to reliably predict the important photochemical, biological, and chemical processes governing CDOM, and hence its

  19. Soil biogeochemistry in the age of big data

    Science.gov (United States)

    Cécillon, Lauric; Barré, Pierre; Coissac, Eric; Plante, Alain; Rasse, Daniel

    2015-04-01

    Data is becoming one of the key resource of the XXIst century. Soil biogeochemistry is not spared by this new movement. The conservation of soils and their services recently came into the political agenda. However, clear knowledge on the links between soil characteristics and the various processes ensuring the provision of soil services is rare at the molecular or the plot scale, and does not exist at the landscape scale. This split between society's expectations on its natural capital, and scientific knowledge on the most complex material on earth has lead to an increasing number of studies on soils, using an increasing number of techniques of increasing complexity, with an increasing spatial and temporal coverage. From data scarcity with a basic data management system, soil biogeochemistry is now facing a proliferation of data, with few quality controls from data collection to publication and few skills to deal with them. Based on this observation, here we (1) address how big data could help in making sense of all these soil biogeochemical data, (2) point out several shortcomings of big data that most biogeochemists will experience in their future career. Massive storage of data is now common and recent opportunities for cloud storage enables data sharing among researchers all over the world. The need for integrative and collaborative computational databases in soil biogeochemistry is emerging through pioneering initiatives in this direction (molTERdb; earthcube), following soil microbiologists (GenBank). We expect that a series of data storage and management systems will rapidly revolutionize the way of accessing raw biogeochemical data, published or not. Data mining techniques combined with cluster or cloud computing hold significant promises for facilitating the use of complex analytical methods, and for revealing new insights previously hidden in complex data on soil mineralogy, organic matter and biodiversity. Indeed, important scientific advances have

  20. Plant Biology and Biogeochemistry Department annual project report 1999

    DEFF Research Database (Denmark)

    Jensen, A.; Gissel Nielsen, G.; Giese, H.;

    2000-01-01

    The Department of Plant Biology and Biogeochemistry is engaged in basic and applied research to improve the scientific knowledge of developing new methods and technology for the future, environmentally benign industrial and agricultural production, thusexerting less stress and strain on the envir......The Department of Plant Biology and Biogeochemistry is engaged in basic and applied research to improve the scientific knowledge of developing new methods and technology for the future, environmentally benign industrial and agricultural production, thusexerting less stress and strain...... project summarizes and highlights our results and achievements to give an idea of the researchdirections in the Department. Some 160 persons, including staff, undergraduate students, postgraduate scientists and visiting scientists from all over the world, address our research goals. The Department......’s contribution to education and training ispresented. Lists of publications, papers accepted for publications, guest lecturers, exchange of scientists and lectures and poster presentations at meetings are included in the report. Names of the scientific, technical and administrative staff members...

  1. Optimizing available network resources to address questions in environmental biogeochemistry

    Science.gov (United States)

    Hinckley, Eve-Lyn; Suzanne Andersen,; Baron, Jill S.; Peter Blanken,; Gordon Bonan,; William Bowman,; Sarah Elmendorf,; Fierer, Noah; Andrew Fox,; Keli Goodman,; Katherine Jones,; Danica Lombardozzi,; Claire Lunch,; Jason Neff,; Michael SanClements,; Katherine Suding,; Will Wieder,

    2016-01-01

    An increasing number of network observatories have been established globally to collect long-term biogeochemical data at multiple spatial and temporal scales. Although many outstanding questions in biogeochemistry would benefit from network science, the ability of the earth- and environmental-sciences community to conduct synthesis studies within and across networks is limited and seldom done satisfactorily. We identify the ideal characteristics of networks, common problems with using data, and key improvements to strengthen intra- and internetwork compatibility. We suggest that targeted improvements to existing networks should include promoting standardization in data collection, developing incentives to promote rapid data release to the public, and increasing the ability of investigators to conduct their own studies across sites. Internetwork efforts should include identifying a standard measurement suite—we propose profiles of plant canopy and soil properties—and an online, searchable data portal that connects network, investigator-led, and citizen-science projects.

  2. Rethinking Sediment Biogeochemistry After the Discovery of Electric Currents

    DEFF Research Database (Denmark)

    Nielsen, Lars Peter; Risgaard-Petersen, Nils

    2015-01-01

    of the oxygen consumption. In addition, it implies a separation of strong proton generators and consumers and the formation of measurable electric fields, which have several effects on mineral development and ion migration. This article reviews the work on electric currents and cable bacteria published through......The discovery of electric currents in marine sediments arose from a simple observation that conventional biogeochemistry could not explain: Sulfide oxidation in one place is closely coupled to oxygen reduction in another place, centimeters away. After experiments demonstrated that this resulted...... from electric coupling, the conductors were found to be long, multicellular, filamentous bacteria, now known as cable bacteria. The spatial separation of oxidation and reduction processes by these bacteria represents a shortcut in the conventional cascade of redox processes and may drive most...

  3. assessing contributions of jgofs; previewing Studies in Ocean Ecology, Biogeochemistry

    Science.gov (United States)

    Steinberg, Deborah K.; Ducklow, Hugh W.; Buesseler, Ken O.; Bowles, Margaret C.

    Despite impediments to travel imposed by global political and health concerns, 332 scientists and students from 32 countries gathered in Washington, D.C. in early May to celebrate the conclusion of the Joint Global Ocean Flux Study (JGOFS), and to assess both its accomplishments and the future course of research in ocean ecology and biogeochemistry.Launched in 1987 under the auspices of the Scientific Committee on Oceanic Research (SCOR), JGOFS became the first core project of the International Geosphere-Biosphere Programme (IGBP) 2 years later as its first field studies were getting underway. Global in scope and multinational and interdisciplinary from its inception, JGOFS adopted two major goals: to understand the processes controlling the cycling of carbon and other biogenic elements in the ocean and their exchange with the atmosphere and the sea floor, and to advance our capacity to predict the response of ocean systems to anthropogenic perturbations.

  4. Applying EMSL Capabilities to Biogeochemistry and Environmental Research

    Energy Technology Data Exchange (ETDEWEB)

    Felmy, Andy

    2007-04-19

    The Environmental Molecular Sciences laboratory (EMSL) is a national scientific user facility operated by the Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy's Office of Biological and Environmental Research. Located in Richland, Washington, EMSL offers researchers a comprehensive array of cutting-edge capabilities unmatched anywhere else in the world and access to the expertise of over 300 resident users--all at one location. EMSL's resources are available on a peer-reviewed proposal basis and are offered at no cost if research results are shared in the open literature. Researchers are encouraged to submit a proposal centered around one of EMSL's four Science Themes, which represent growing areas of research: (1) Geochemistry/Biogeochemistry and Subsurface Science; (2) Atmospheric Aerosol Chemistry; (3) Biological Interactions and Dynamics; and (4) Science of Interfacial Phenomena. To learn more about EMSL, visit www.emsl.pnl.gov.

  5. Impacts of sea spray geoengineering on ocean biogeochemistry

    Science.gov (United States)

    Partanen, Antti-Ilari; Keller, David P.; Korhonen, Hannele; Matthews, H. Damon

    2016-07-01

    We used an Earth system model of intermediate complexity to study the effects of Solar Radiation Management (SRM) by sea spray geoengineering on ocean biogeochemistry. SRM slightly decreased global ocean net primary productivity (NPP) relative to the control run. The lower temperatures in the SRM run decreased NPP directly but also indirectly increased NPP in some regions due to changes in nutrient availability resulting from changes in ocean stratification and circulation. Reduced light availability had a minor effect on global total NPP but a major regional effect near the nutrient-rich upwelling region off the coast of Peru, where light availability is the main limiting factor for phytoplankton growth in our model. Unused nutrients from regions with decreased NPP also fueled NPP elsewhere. In the context of RCP4.5 simulation used here, SRM decreased ocean carbon uptake due to changes in atmospheric CO2 concentrations, seawater chemistry, NPP, temperature, and ocean circulation.

  6. Microbial antimony biogeochemistry: Enzymes, regulation, and related metabolic pathways

    Science.gov (United States)

    Li, Jingxin; Qian Wang,; Oremland, Ronald S.; Kulp, Thomas R.; Rensing, Christopher; Wang, Gejiao

    2016-01-01

    Antimony (Sb) is a toxic metalloid that occurs widely at trace concentrations in soil, aquatic systems, and the atmosphere. Nowadays, with the development of its new industrial applications and the corresponding expansion of antimony mining activities, the phenomenon of antimony pollution has become an increasingly serious concern. In recent years, research interest in Sb has been growing and reflects a fundamental scientific concern regarding Sb in the environment. In this review, we summarize the recent research on bacterial antimony transformations, especially those regarding antimony uptake, efflux, antimonite oxidation, and antimonate reduction. We conclude that our current understanding of antimony biochemistry and biogeochemistry is roughly equivalent to where that of arsenic was some 20 years ago. This portends the possibility of future discoveries with regard to the ability of microorganisms to conserve energy for their growth from antimony redox reactions and the isolation of new species of “antimonotrophs.”

  7. Global terrestrial biogeochemistry: Perturbations, interactions, and time scales

    Energy Technology Data Exchange (ETDEWEB)

    Braswell, B.H. Jr.

    1996-12-01

    Global biogeochemical processes are being perturbed by human activity, principally that which is associated with industrial activity and expansion of urban and agricultural complexes. Perturbations have manifested themselves at least since the beginning of the 19th Century, and include emissions of CO{sub 2} and other pollutants from fossil fuel combustion, agricultural emissions of reactive nitrogen, and direct disruption of ecosystem function through land conversion. These perturbations yield local impacts, but there are also global consequences that are the sum of local-scale influences. Several approaches to understanding the global-scale implications of chemical perturbations to the Earth system are discussed. The lifetime of anthropogenic CO{sub 2} in the atmosphere is an important concept for understanding the current and future commitment to an altered atmospheric heat budget. The importance of the terrestrial biogeochemistry relative to the lifetime of excess CO{sub 2} is demonstrated using dynamic, aggregated models of the global carbon cycle.

  8. A Global Ocean Biogeochemistry General Circulation Model and its Simulations

    Institute of Scientific and Technical Information of China (English)

    XU Yongfu; LI Yangchun; CHU Min

    2013-01-01

    An ocean biogeochemistry model was developed and incorporated into a global ocean general circulation model (LICOM) to form an ocean biogeochemistry general circulation model (OBGCM).The model was used to study the natural carbon cycle and the uptake and storage of anthropogenic CO2 in the ocean.A global export production of 12.5 Pg C yr-1 was obtained.The model estimated that in the pre-industrial era the global equatorial region within ±15° of the equator released 0.97 Pg C yr-1 to the atmosphere,which was balanced by the gain of CO2 in other regions.The post-industrial air-sea CO2 flux indicated the oceanic uptake of CO2 emitted by human activities.An increase of 20-50 μmol kg-1 for surface dissolved inorganic carbon (DIC) concentrations in the 1990s relative to pre-industrial times was obtained in the simulation,which was consistent with data-based estimates.The model generated a total anthropogenic carbon inventory of 105 Pg C as of 1994,which was within the range of estimates by other researchers.Various transports of both natural and anthropogenic DIC as well as labile dissolved organic carbon (LDOC)were estimated from the simulation.It was realized that the Southern Ocean and the high-latitude region of the North Pacific are important export regions where accumulative air-sea CO2 fluxes are larger than the DIC inventory,whereas the subtropical regions are acceptance regions.The interhemispheric transport of total natural carbon (DIC+LDOC) was found to be northward (0.11 Pg C yr-1),which was just balanced by the gain of carbon from the atmosphere in the Southern Hemisphere.

  9. Comparative biogeochemistry-ecosystem-human interactions on dynamic continental margins

    Science.gov (United States)

    Levin, Lisa A.; Liu, Kon-Kee; Emeis, Kay-Christian; Breitburg, Denise L.; Cloern, James; Deutsch, Curtis; Giani, Michele; Goffart, Anne; Hofmann, Eileen E.; Lachkar, Zouhair; Limburg, Karin; Liu, Su-Mei; Montes, Enrique; Naqvi, Wajih; Ragueneau, Olivier; Rabouille, Christophe; Sarkar, Santosh Kumar; Swaney, Dennis P.; Wassman, Paul; Wishner, Karen F.

    2014-01-01

    The ocean’s continental margins face strong and rapid change, forced by a combination of direct human activity, anthropogenic CO2-induced climate change, and natural variability. Stimulated by discussions in Goa, India at the IMBER IMBIZO III, we (1) provide an overview of the drivers of biogeochemical variation and change on margins, (2) compare temporal trends in hydrographic and biogeochemical data across different margins (3) review ecosystem responses to these changes, (4) highlight the importance of margin time series for detecting and attributing change and (5) examine societal responses to changing margin biogeochemistry and ecosystems. We synthesize information over a wide range of margin settings in order to identify the commonalities and distinctions among continental margin ecosystems. Key drivers of biogeochemical variation include long-term climate cycles, CO2-induced warming, acidification, and deoxygenation, as well as sea level rise, eutrophication, hydrologic and water cycle alteration, changing land use, fishing, and species invasion. Ecosystem responses are complex and impact major margin services including primary production, fisheries production, nutrient cycling, shoreline protection, chemical buffering, and biodiversity. Despite regional differences, the societal consequences of these changes are unarguably large and mandate coherent actions to reduce, mitigate and adapt to multiple stressors on continental margins.

  10. Understanding the health impacts of urbanization in China: A living laboratory for urban biogeochemistry research

    Science.gov (United States)

    Zhu, Y. G.

    2015-12-01

    China has the largest population in the world, and by 2011, more than 50% of its population are now living in cities. This ongoing societal change has profound impacts on environmental quality and population health. In addition to intensive discharges of waste, urbanization is not only changing the land use and land cover, but also inducing fundamental changes in biogeochemical processes. Unlike biogeochemistry in non-urban environment, the biological component of urban biogeochemistry is dominated by direct human activities, such as air pollution derived from transport, wastewater treatment, garbage disposal and increase in impervious surface etc. Managing urban biogeochemistry will include source control over waste discharge, eco-infrastructure (such as green space and eco-drainage), resource recovery from urban waste stream, and integration with peri-urban ecosystem, particularly with food production system. The overall goal of managing urban biogeochemistry is for human health and wellbeing, which is a global challenge. In this paper, the current status of urban biogeochemistry research in China will be briefly reviewed, and then it will focus on nutrient recycling and waste management, as these are the major driving forces of environmental quality changes in urban areas. This paper will take a holistic view on waste management, covering urban metabolism analysis, technological innovation and integration for resource recovery from urban waste stream, and risk management related to waste recycling and recovery.

  11. Microbial reduction of iron and porewater biogeochemistry in acidic peatlands

    Directory of Open Access Journals (Sweden)

    K. Küsel

    2008-05-01

    Full Text Available Temporal drying of upper soil layers of acidic methanogenic peatlands might divert the flow of reductants from CH4 formation to other electron-accepting processes due to a renewal of alternative electron acceptors. In this study, we evaluated the in situ relevance of Fe(III-reducing microbial activities in peatlands of a forested catchment that differed in their hydrology. Intermittent seeps reduced sequentially nitrate, Fe(III, and sulfate during periods of water saturation. Due to the acidic soil conditions, released Fe(II was transported with the groundwater flow and accumulated as Fe(III in upper soil layers of a lowland fen apparently due to oxidation. Microbial Fe(III reduction in the upper soil layer accounted for 26.7 and 71.6% of the anaerobic organic carbon mineralization in the intermittent seep and the lowland fen, respectively. In an upland fen not receiving exogenous Fe, Fe(III reduction contributed only to 6.7%. Fe(II and acetate accumulated in deeper porewater of the lowland fen with maximum concentrations of 7 and 3 mM, respectively. Both supplemental glucose and acetate stimulated the reduction of Fe(III indicating that fermentative, incomplete, and complete oxidizers were involved in Fe(II formation in the acidic fen. Amplification of DNA yielded PCR products specific for Acidiphilium-, Geobacter-, and Geothrix-, but not for Shewanella- or Anaeroromyxobacter-related sequences. Porewater biogeochemistry observed during a 3-year-period suggests that increased drought periods and subsequent intensive rainfalls due to global climate change will further favor Fe(III and sulfate as alternative electron acceptors due to the storage of their reduced compounds in the soil.

  12. Microbial reduction of iron and porewater biogeochemistry in acidic peatlands

    Directory of Open Access Journals (Sweden)

    K. Küsel

    2008-11-01

    Full Text Available Temporal drying of upper soil layers of acidic methanogenic peatlands might divert the flow of reductants from CH4 formation to other electron-accepting processes due to a renewal of alternative electron acceptors. In this study, we evaluated the in situ relevance of Fe(III-reducing microbial activities in peatlands of a forested catchment that differed in their hydrology. Intermittent seeps reduced sequentially nitrate, Fe(III, and sulfate during periods of water saturation. Due to the acidic soil conditions, released Fe(II was transported with the groundwater flow and accumulated as Fe(III in upper soil layers of a lowland fen apparently due to oxidation. Microbial Fe(III reduction in the upper soil layer accounted for 26.7 and 71.6% of the anaerobic organic carbon mineralization in the intermittent seep and the lowland fen, respectively. In an upland fen not receiving exogenous Fe, Fe(III reduction contributed only to 6.7%. Fe(II and acetate accumulated in deeper porewater of the lowland fen with maximum concentrations of 7 and 3 mM, respectively. Both supplemental glucose and acetate stimulated the reduction of Fe(III indicating that fermentative, incomplete, and complete oxidizers were involved in Fe(II formation in the acidic fen. Amplification of DNA yielded PCR products specific for Acidiphilium-, Geobacter-, and Geothrix-, but not for Shewanella- or Anaeroromyxobacter-related sequences. Porewater biogeochemistry observed during a 3-year-period suggests that increased drought periods and subsequent intensive rainfalls due to global climate change will further favor Fe(III and sulfate as alternative electron acceptors due to the storage and enhanced re-oxidation of their reduced compounds in the soil.

  13. Biogeochemistry of the Kem' River estuary, White Sea (Russia

    Directory of Open Access Journals (Sweden)

    V. R. Shevchenko

    2005-01-01

    Full Text Available The biogeochemistry of the river-sea interface was studied in the Kem' River (the largest river flowing to the White Sea from Karelian coast estuary and adjacent area of the White Sea onboard the RV 'Ekolog' in summer 2001, 2002 and 2003. The study area can be divided into 3 zones: I - the estuary itself, with water depth from 1 to 5m and low salinity in the surface layer (salinity is lower than 0.2psu in the Kem' River and varies from 15 to 20psu in outer part of this zone; II - the intermediate zone with depths from 5 to 10m and salinity at the surface from 16 to 22psu; III - the marine zone with depths from 10 to 29 m and salinity 21-24.5psu. Highest concentrations of the suspended particulate matter (SPM were registered in the Kem' mouth (5-7mg/l. They sharply decreased to values org to nitrogen (N ratio (Corg/N in both suspended matter and bottom sediments decreases from the river to the marine part of the mixing zone (from 8.5 to 6.1 in the suspended matter and from 14.6 to 7.5 in the bottom sediments, demonstrating that content of terrestrial-derived organic matter decreases and content of marine organic matter increases from the river mouth to the sea. The Kem' estuary exhibits a similar character of biogeochemial processes as in the large Arctic estuaries, but the scale of these processes (amount of river input of SPM, POC, area of estuaries is different.

  14. The Sensitivity of Simulated Ocean Biogeochemistry to Forcing Fields Derived from NCEP and MERRA Reanalysis Products

    Science.gov (United States)

    Gregg, Watson; Casey, Nancy

    2010-01-01

    Ocean biogeochemistry models are typically forced by atmospheric and oceanic data derived from reanalysis products. For the NASA Ocean Biogeochemistry Model (NOBM) such reanalysis forcing fields include: surface wind stress, sea surface temperature, ice distributions, shortwave radiation, surface wind speeds and surface atmospheric pressure. Additionally, proper computation of ocean irradiance requires reanalysis products of relative humidity and precipitable water (in addition to aerosol and cloud information which is derived from satellite data). The question posed here is, does the choice of reanalysis products make a difference in the representation of ocean biology and biogeochemistry? NOBM was forced by NCEP and MERRA reanalysis products for the period 2002-2009. We find that in 2009 global distributions and abundances of biological variables (total chlorophyll and nutrients) and carbon (dissolved inorganic and organic carbon and surface pCO2) were similar between the two different forcing fields. Global statistical comparisons with satellite and in situ data also showed negligible differences.

  15. Effects of Nonnative Ungulate Removal on Plant Communities and Soil Biogeochemistry in Tropical Forests

    Science.gov (United States)

    Cole, R. J.; Litton, C. M.; Giardina, C. P.; Sparks, J. P.

    2014-12-01

    Non-native ungulates have substantial impacts on native ecosystems globally, altering both plant communities and soil biogeochemistry. Across tropical and temperate ecosystems, land managers fence and remove non-native ungulates to conserve native biodiversity, a costly management action, yet long-term outcomes are not well quantified. Specifically, knowledge gaps include: (i) the magnitude and time frame of plant community recovery; (ii) the response of non-native invasive plants; and (iii) changes to soil biogeochemistry. In 2010, we established a series of paired ungulate presence vs. removal plots that span a 20 yr. chronosequence in tropical montane wet forests on the Island of Hawaii to quantify the impacts and temporal legacy of feral pig removal on plant communities and soil biogeochemistry. We also compared soil biogeochemistry in targeted areas of low and high feral pig impact. Our work shows that both native and non-native vegetation respond positively to release from top-down control following removal of feral pigs, but species of high conservation concern recover only if initially present at the time of non-native ungulate removal. Feral pig impacts on soil biogeochemistry appear to last for at least 20 years following ungulate removal. We observed that both soil physical and chemical properties changed with feral pig removal. Soil bulk density and volumetric water content decreased while extractable base cations and inorganic N increased in low vs. high feral pig impact areas. We hypothesize that altered soil biogeochemistry facilitates continued invasions by non-native plants, even decades after non-native ungulate removal. Future work will concentrate on comparisons between wet and dry forest ecosystems and test whether manipulation of soil nutrients can be used to favor native vs. non-native plant establishment.

  16. Iron biogeochemistry across marine systems – progress from the past decade

    Directory of Open Access Journals (Sweden)

    E. Breitbarth

    2010-03-01

    Full Text Available Based on an international workshop (Gothenburg, 14–16 May 2008, this review article aims to combine interdisciplinary knowledge from coastal and open ocean research on iron biogeochemistry. The major scientific findings of the past decade are structured into sections on natural and artificial iron fertilization, iron inputs into coastal and estuarine systems, colloidal iron and organic matter, and biological processes. Potential effects of global climate change, particularly ocean acidification, on iron biogeochemistry are discussed. The findings are synthesized into recommendations for future research areas.

  17. Carbonate system biogeochemistry in a subterranean estuary - Waquoit Bay, USA

    Science.gov (United States)

    Liu, Qian; Charette, Matthew A.; Breier, Crystaline F.; Henderson, Paul B.; McCorkle, Daniel C.; Martin, William; Dai, Minhan

    2017-04-01

    Quantifying carbon fluxes associated with submarine groundwater discharge (SGD) remains challenging due to the complex biogeochemistry of the carbonate system in the subterranean estuary (STE). Here we conducted time series measurements of total alkalinity (TAlk) and dissolved inorganic carbon (DIC) in a well-studied coastal aquifer (Waquoit Bay, Massachusetts, USA). Groundwater samples were collected monthly from May 2009 to June 2010 across the freshwater-saltwater mixing zone of the Waquoit Bay (WB) STE. The concentrations of both TAlk and DIC in zero-salinity groundwater were variable, but were lower than those in the bay water (S ∼ 28). DIC underwent slightly non-conservative mixing between low and intermediate salinities while there was an apparent additional DIC source at high salinity (>20) in all seasons. TAlk concentrations exhibited even stronger variations, with evidence of both production and consumption in high salinity zones, and consistent TAlk consumption at intermediate salinity in summer and fall (June-December, 2009). The increases in DIC and TAlk at high salinity were attributed to aerobic respiration and denitrification in WB sediments during bay water recharge of the STE. We infer that the loss of TAlk at intermediate salinity reflects H+ production as reduced compounds (e.g. Fe2+) are oxidized within the STE. In terms of impacts on surface water inorganic carbon budgets, the SGD-derived DIC flux was mainly controlled by seasonal changes in SGD while a combination of TAlk concentration variability and SGD drove the TAlk flux. SGD-derived DIC, aqueous CO2, and H+ fluxes to the bay were ∼40-50% higher in summer vs. in winter, a result of enhanced marine groundwater flux and significant TAlk removal (proton addition) during periods of high seawater intrusion. Furthermore, the SGD-derived DIC flux was consistently greater than TAlk flux regardless of season, indicating that SGD serves to reduce the CO2 buffering capacity of surface water. Our

  18. The importance of shallow hydrothermal island arc systems in ocean biogeochemistry

    NARCIS (Netherlands)

    Hawkes, J.A.; Connelly, D.P.; Rijkenberg, M.J.A.; Achterberg, E.P.

    2014-01-01

    Hydrothermal venting often occurs at submarine volcanic calderas on island arc chains, typically at shallower depths than mid-ocean ridges. The effect of these systems on ocean biogeochemistry has been under-investigated to date. Here we show that hydrothermal effluent from an island arc caldera was

  19. From the forest to the sea and back again: Biogeochemistry in the Oregon Coast Range

    Science.gov (United States)

    Variations in plant community composition across the landscape can influence nutrient retention and loss at the watershed scale. A striking example of plant species influence is the role of N2-fixing red alder (Alnus rubra) in the biogeochemistry of Pacific Northwest forests. A...

  20. Second international symposium on the biogeochemistry of model estuaries: Estuarine processes in global change

    Energy Technology Data Exchange (ETDEWEB)

    1991-12-31

    This report consists of abstracts of papers presented at the symposium of Biogeochemistry. The main topics discussed at the meeting are; nutrient and mineral cycling, trace element distribution, sources and sinks of estuaries, sedimentation, importance of organic matter, and other biogeochemical processes of estuaries.

  1. Evolution to decay of upwelling and associated biogeochemistry over the southeastern Arabian sea shelf

    Digital Repository Service at National Institute of Oceanography (India)

    Gupta, G.V.M.; Sudheesh, V.; Sudharma, K.V.; Saravanane, N.; Dhanya, V.; Dhanya, K.R.; Lakshmi, G.; Sudhakar, M.; Naqvi, S.W.A.

    (SM). By changing an oligotrophic to a nutrient-replete condition, the upwelling is the major process that regulates the biogeochemistry of this shelf. Its onset is perceptible at 100m depth between January and March. The upwelling reaches the surface...

  2. Nitrogen Biogeochemistry in Urban Wetlands and Bioretention Systems: The Evolving Roles of Urban Stormwater Management Practices.

    Science.gov (United States)

    Description for AGU 2009 Fall Meeting, San Francisco, CA, December 14-18, 2009. I have been invited to speak in a session hosted by the Biogeosciences section of the American Geophysical Union. The session is titled “Biogeochemistry of Soil and Surface Water in Rural, Suburban ...

  3. Sediment biogeochemistry in an East African mangrove forest (Gazi Bay, Kenya)

    NARCIS (Netherlands)

    Middelburg, J.J.; Nieuwenhuize, J.; Slim, F.J.; Ohowa, B.

    1996-01-01

    The biogeochemistry of mangrove sediments was investigated in several mangrove forest communities in Gazi Bay, a coastal lagoon in Kenya, Africa. Carbon dioxide fluxes, sediment median grain sizes, sedimentary organic carbon, nitrogen and phosphorus contents and pore-water characteristics (ammonium,

  4. Influence of Sea Ice on Arctic Marine Sulfur Biogeochemistry in the Community Climate System Model

    Energy Technology Data Exchange (ETDEWEB)

    Deal, Clara [Univ. of Alaska, Fairbanks, AL (United States); Jin, Meibing [Univ. of Alaska, Fairbanks, AL (United States)

    2013-06-30

    Global climate models (GCMs) have not effectively considered how responses of arctic marine ecosystems to a warming climate will influence the global climate system. A key response of arctic marine ecosystems that may substantially influence energy exchange in the Arctic is a change in dimethylsulfide (DMS) emissions, because DMS emissions influence cloud albedo. This response is closely tied to sea ice through its impacts on marine ecosystem carbon and sulfur cycling, and the ice-albedo feedback implicated in accelerated arctic warming. To reduce the uncertainty in predictions from coupled climate simulations, important model components of the climate system, such as feedbacks between arctic marine biogeochemistry and climate, need to be reasonably and realistically modeled. This research first involved model development to improve the representation of marine sulfur biogeochemistry simulations to understand/diagnose the control of sea-ice-related processes on the variability of DMS dynamics. This study will help build GCM predictions that quantify the relative current and possible future influences of arctic marine ecosystems on the global climate system. Our overall research objective was to improve arctic marine biogeochemistry in the Community Climate System Model (CCSM, now CESM). Working closely with the Climate Ocean Sea Ice Model (COSIM) team at Los Alamos National Laboratory (LANL), we added 1 sea-ice algae and arctic DMS production and related biogeochemistry to the global Parallel Ocean Program model (POP) coupled to the LANL sea ice model (CICE). Both CICE and POP are core components of CESM. Our specific research objectives were: 1) Develop a state-of-the-art ice-ocean DMS model for application in climate models, using observations to constrain the most crucial parameters; 2) Improve the global marine sulfur model used in CESM by including DMS biogeochemistry in the Arctic; and 3) Assess how sea ice influences DMS dynamics in the arctic marine

  5. Biogeochemistry Science and Education Part One: Using Non-Traditional Stable Isotopes as Environmental Tracers Part Two: Identifying and Measuring Undergraduate Misconceptions in Biogeochemistry

    Science.gov (United States)

    Mead, Chris

    This dissertation is presented in two sections. First, I explore two methods of using stable isotope analysis to trace environmental and biogeochemical processes. Second, I present two related studies investigating student understanding of the biogeochemical concepts that underlie part one. Fe and Hg are each biogeochemically important elements in their own way. Fe is a critical nutrient for phytoplankton, while Hg is detrimental to nearly all forms of life. Fe is often a limiting factor in marine phytoplankton growth. The largest source, by mass, of Fe to the open ocean is windblown mineral dust, but other more soluble sources are more bioavailable. To look for evidence of these non-soil dust sources of Fe to the open ocean, I measured the isotopic composition of aerosol samples collected on Bermuda. I found clear evidence in the fine size fraction of a non-soil dust Fe source, which I conclude is most likely from biomass burning. Widespread adoption of compact fluorescent lamps (CFL) has increased their importance as a source of environmental Hg. Isotope analysis would be a useful tool in quantifying this impact if the isotopic composition of Hg from CFL were known. My measurements show that CFL-Hg is isotopically fractionated, in a unique pattern, during normal operation. This fractionation is large and has a distinctive, mass-independent signature, such that CFL Hg can be uniquely identified from other sources. Misconceptions research in geology has been a very active area of research, but student thinking regarding the related field of biogeochemistry has not yet been studied in detail. From interviews with 40 undergraduates, I identified over 150 specific misconceptions. I also designed a multiple-choice survey (concept inventory) to measure understanding of these same biogeochemistry concepts. I present statistical evidence, based on the Rasch model, for the reliability and validity of this instrument. This instrument will allow teachers and researchers to

  6. Tenth international symposium on environmental biogeochemistry. Final technical report, December 15, 1990--December 14, 1991

    Energy Technology Data Exchange (ETDEWEB)

    Ehrlich, H.L.

    1992-01-01

    The primary task of this Symposium on Environmental Biogeochemistry was to examine our current understanding of GLOBAL CHANGE AND THE BIOGEOCHEMISTRY OF RADIATIVE TRACE GASES. The symposium was divided into 12 non-overlapping sessions: Paleoatmospheres and paleoclimates; Global distributions and atmospheric reactions; Poster presentations on the topics of sessions 1, 2, 4, 5, and 7; Terrestrial systems and land use change - 1; Terrestrial and land use change - 11; Fluxes and cycling in aquatic systems; Metals, organics, and depositional environments; Poster presentations on the topics of sessions 6, 9, 10 and 12; Biological Mechanisms of formation and destruction - 1; Biological mechanisms of formation and destruction - 11; High latitude systems; and Global sources, sinks, and feedbacks.

  7. Impact of coral spawning on the biogeochemistry of a Hawaiian reef

    Science.gov (United States)

    Briggs, R. A.; Padilla-Gamiño, J. L.; Bidigare, R. R.; Gates, R. D.; Ruttenberg, K. C.

    2013-12-01

    We examined the impact of Montipora capitata coral spawning on local biogeochemistry in Kane'ohe Bay, Hawai'i. This event supplied labile, spawn-derived organic matter (SDOM) to the water column, triggering a cascading series of related effects on the biogeochemistry of the reef. Specifically, we measured the isotopic composition and nutrient ratios of spawning material and coral tissues, and utilized these signatures to track pathways of SDOM incorporation into this coral-dominated ecosystem. We observed: (1) shifts in the isotopic signatures of coral tissues after the spawning event, (2) rapid turnover of SDOM within the water column and enhanced deposition of POM to the sediment surface, (3) enhanced sediment efflux of NH after the spawning event that triggered a phytoplankton bloom in the overlying water, and (4) drawdown of dissolved nutrients in the water column after spawning that coincided with the occurrence of a water column phytoplankton bloom. Our results show that single-species spawning events can serve as a source of substantial nutrient input to the water column, contributing in similar ways to storm-driven river nutrient input, and with measurable impact on the biogeochemistry of the reef.

  8. Hydrogen Isotope Biogeochemistry of Plant Biomarkers in Tropical Trees from the Andes to Amazon

    Science.gov (United States)

    Feakins, S. J.; Ponton, C.; West, A. J.; Malhi, Y.; Goldsmith, G.; Salinas, N.; Bentley, L. P.

    2014-12-01

    Plant leaf waxes are well known biomarkers for terrestrial vegetation. Generally, their hydrogen isotopic composition (D/H) records the isotopic composition of precipitation, modulated by leaf water processes and a large biosynthetic fractionation. In addition, the D/H of methoxyl groups on tree wood lignin is an emerging technique thought to record the D/H of source waters, without leaf water complications. Using each of these biomarkers as proxies requires understanding D/H fractionations in plant systems, but few studies have directly studied hydrogen isotope biogeochemistry in tropical plants. An approach that has proven helpful is the paired analysis of plant waters and plant biomarkers: in order that fractionations can be directly computed rather than assumed. This presents logistical challenges in remote tropical forest environments. We report on a unique dataset collected by tree-climbers from 6 well-studied vegetation plots across a 4km elevation transect in the Peruvian Andes and Amazonia. We have measured the D/H of stem water and leaf water, and we compare these to precipitation isotopes and stream waters. The goal of the plant water studies is to understand plant water uptake and stem-leaf water isotopic offsets which can vary due to both transpiration and foliar uptake of water in tropical montane forests. We are in the process of measuring the D/H of plant biomarkers (n-alkanoic acids, n-alkanes and lignin methoxyl) in order to assess how these water isotopic signals are encoded in plant biomarkers. We compare the species-specific modern plant insights to the plant leaf wax n-alkanoic acid D/H that we have recently reported from soils and river sediments from the same region, in order to understand how signals of plant biogeochemistry are integrated into geological sedimentary archives. Progress and open questions in tropical isotope biogeochemistry will be discussed at the meeting.

  9. Agricultural intensification exacerbates spillover effects on soil biogeochemistry in adjacent forest remnants.

    Directory of Open Access Journals (Sweden)

    Raphael K Didham

    Full Text Available Land-use intensification is a central element in proposed strategies to address global food security. One rationale for accepting the negative consequences of land-use intensification for farmland biodiversity is that it could 'spare' further expansion of agriculture into remaining natural habitats. However, in many regions of the world the only natural habitats that can be spared are fragments within landscapes dominated by agriculture. Therefore, land-sparing arguments hinge on land-use intensification having low spillover effects into adjacent protected areas, otherwise net conservation gains will diminish with increasing intensification. We test, for the first time, whether the degree of spillover from farmland into adjacent natural habitats scales in magnitude with increasing land-use intensity. We identified a continuous land-use intensity gradient across pastoral farming systems in New Zealand (based on 13 components of farmer input and soil biogeochemistry variables, and measured cumulative off-site spillover effects of fertilisers and livestock on soil biogeochemistry in 21 adjacent forest remnants. Ten of 11 measured soil properties differed significantly between remnants and intact-forest reference sites, for both fenced and unfenced remnants, at both edge and interior. For seven variables, the magnitude of effects scaled significantly with magnitude of surrounding land-use intensity, through complex interactions with fencing and edge effects. In particular, total C, total N, δ15N, total P and heavy-metal contaminants of phosphate fertilizers (Cd and U increased significantly within remnants in response to increasing land-use intensity, and these effects were exacerbated in unfenced relative to fenced remnants. This suggests movement of livestock into surrounding natural habitats is a significant component of agricultural spillover, but pervasive changes in soil biogeochemistry still occur through nutrient spillover channels alone

  10. Bacterial community characterization and biogeochemistry of sediments from a tropical upwelling system (Cabo Frio, Southeastern Brazil)

    Science.gov (United States)

    Castelo-Branco, R.; Barreiro, A.; Silva, F. S.; Carvalhal-Gomes, S. B. V.; Fontana, L. F.; Mendonça-Filho, J. G.; Vasconcelos, V.

    2016-11-01

    The Cabo Frio Upwelling System is one of the largest and most productive areas in southeastern Brazil. Although it is well-known that bacterial communities play a crucial role in the biogeochemical cycles and food chain of marine ecosystems, little is known regarding the microbial communities in the sediments of this upwelling region. In this research, we address the effect of different hydrological conditions on the biogeochemistry of sediments and the diversity of bacterial communities. Biogeochemistry profiles of sediments from four sampling stations along an inner-outer transect on the continental shelf were evaluated and denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments was used to study the bacterial community composition in these sediments. Our sequencing analysis of excised bands identified Alpha- and Gammaproteobacteria, Bacteroidetes and bacteria belonging to the Firmicutes phyla as the phylogenetic groups, indicating the existence of great diversity in these marine sediments. In this multidisciplinary study, the use of multivariate analysis was crucial for understanding how biogeochemical profiles influence bacterial community distribution. A Principal Component Analysis (PCA) indicated that the biogeochemical variables exhibited a clear spatial pattern that is mainly related to hydrological conditions. A Correspondence Analysis (CA) revealed an important association between certain taxonomic groups and specific sampling locations. Canonical Correspondence Analysis (CCA) demonstrated that the biogeochemistry influences the structure of the bacterial community in sediments. Among the bacterial groups identified, the most taxonomically diverse classes (Alphaproteobacteria and Gammaproteobacteria) were found to be distributed regardless of any studied biogeochemical variables influences, whereas other groups responded to biogeochemical conditions which, in turn, were influenced by hydrological conditions. This finding

  11. Biogeochemistry and community ecology in a spring-fed urban river following a major earthquake.

    Science.gov (United States)

    Wells, Naomi S; Clough, Tim J; Condron, Leo M; Baisden, W Troy; Harding, Jon S; Dong, Y; Lewis, G D; Lear, Gavin

    2013-11-01

    In February 2011 a MW 6.3 earthquake in Christchurch, New Zealand inundated urban waterways with sediment from liquefaction and triggered sewage spills. The impacts of, and recovery from, this natural disaster on the stream biogeochemistry and biology were assessed over six months along a longitudinal impact gradient in an urban river. The impact of liquefaction was masked by earthquake triggered sewage spills (~20,000 m(3) day(-1) entering the river for one month). Within 10 days of the earthquake dissolved oxygen in the lowest reaches was urban natural disasters.

  12. Genes, isotopes, and ecosystem biogeochemistry. Dissecting methane flux at the leading edge of global change

    Energy Technology Data Exchange (ETDEWEB)

    Saleska, Scott [Univ. of Arizona, Tucson, AZ (United States); Rich, Virginia [The Ohio State Univ., Columbus, OH (United States); Tyson, Gene [Univ. of Queensland, St. Lucia (Australia); Chanton, Jeff [Florida State Univ., Tallahassee, FL (United States); Crill, Patrick [Stockholm Univ. (Sweden); Li, Changshen [Univ. of New Hampshire, Durham, NH (United States)

    2016-02-22

    This project integrates across three fields (microbiology, biogeochemistry, and modeling) to understand the mechanisms of methane cycling in thawing permafrost. We have made substantial progress in each area, and in cross-cutting interdisciplinary synthesis. Large releases of CH4 from thawing permafrost to the atmosphere, a strong positive feedback to global warming, are plausible but little is known about the controls on such release. Our project (“IsoGenie”) addresses the key question: What is the interplay of microbial communities and soil organic matter composition in the decomposition of organic C to CH4 across a permafrost thaw gradient?

  13. RRS "Charles Darwin" Cruise 150, 22 Aug - 15 Sep 2003. Benthic ecology and biogeochemistry of the Pakistan Margin

    OpenAIRE

    B. J. Bett

    2004-01-01

    RRS Charles Darwin cruise 150 forms part of a larger programme of research (“Benthic processes in the Arabian Sea: interrelationships between benthos, sediment, biogeochemistry and organic matter cycling”, NER/A/S/2000/01280), focusing on the benthic biogeochemistry of the Pakistan Margin, that includes four cruises in total (CD145, 146, 150 and 151). The primary objectives of the present cruise were: a) to revisit a series of five previously established study sites (A140, A300, A950, A1200 a...

  14. The Biogeochemistry from the Oligotrophic to the Ultraoligotrophic Mediterranean (BOUM experiment

    Directory of Open Access Journals (Sweden)

    T. Moutin

    2011-08-01

    Full Text Available The overall goal of the BOUM (Biogeochemistry from the Oligotrophic to the Ultraoligotrophic Mediterranean experiment was to obtain a better representation of the interactions between planktonic organisms and the cycle of biogenic elements in the Mediterranean Sea (MS, in the context of global climate change and, more particularly, on the role of the ocean in carbon sequestration through biological processes. The BOUM experiment was organized around three main objectives which are: (1 to give a longitudinal description of the biogeochemistry and the biological diversity of the MS during the strongest stratified period, (2 to study processes at the centre of three anticyclonic eddies, and (3 to obtain a representation of the main biogeochemical fluxes and the dynamics of the planktonic trophic network. The international BOUM cruise took place between 16 June and 20 July 2008, involved 32 scientists on board, and covered around 3000 km in the MS from the South of Cyprus to Marseilles (France. This paper describes in detail the objectives of the BOUM experiment, the implementation plan of the cruise, the water masses and general biogeochemical trends encountered, and lays particular emphasis on description of the sections and the main physical characteristics of the three anticyclonic eddies studied, before concluding with first order biogeochemical budgets and a general overview of the 24 other papers published in this special issue.

  15. Regionally coupled atmosphere-ocean-sea ice-marine biogeochemistry model ROM: 1. Description and validation

    Science.gov (United States)

    Sein, Dmitry V.; Mikolajewicz, Uwe; Gröger, Matthias; Fast, Irina; Cabos, William; Pinto, Joaquim G.; Hagemann, Stefan; Semmler, Tido; Izquierdo, Alfredo; Jacob, Daniela

    2015-03-01

    The general circulation models used to simulate global climate typically feature resolution too coarse to reproduce many smaller-scale processes, which are crucial to determining the regional responses to climate change. A novel approach to downscale climate change scenarios is presented which includes the interactions between the North Atlantic Ocean and the European shelves as well as their impact on the North Atlantic and European climate. The goal of this paper is to introduce the global ocean-regional atmosphere coupling concept and to show the potential benefits of this model system to simulate present-day climate. A global ocean-sea ice-marine biogeochemistry model (MPIOM/HAMOCC) with regionally high horizontal resolution is coupled to an atmospheric regional model (REMO) and global terrestrial hydrology model (HD) via the OASIS coupler. Moreover, results obtained with ROM using NCEP/NCAR reanalysis and ECHAM5/MPIOM CMIP3 historical simulations as boundary conditions are presented and discussed for the North Atlantic and North European region. The validation of all the model components, i.e., ocean, atmosphere, terrestrial hydrology, and ocean biogeochemistry is performed and discussed. The careful and detailed validation of ROM provides evidence that the proposed model system improves the simulation of many aspects of the regional climate, remarkably the ocean, even though some biases persist in other model components, thus leaving potential for future improvement. We conclude that ROM is a powerful tool to estimate possible impacts of climate change on the regional scale.

  16. The 2008 Emiliania huxleyi bloom along the Patagonian Shelf: Ecology, biogeochemistry, and cellular calcification

    Science.gov (United States)

    Poulton, Alex J.; Painter, Stuart C.; Young, Jeremy R.; Bates, Nicholas R.; Bowler, Bruce; Drapeau, Dave; Lyczsckowski, Emily; Balch, William M.

    2013-12-01

    blooms are significant contributors to the global production and export of calcium carbonate (calcite). The Patagonian Shelf is a site of intense annual coccolithophore blooms during austral summer. During December 2008, we made intensive measurements of the ecology, biogeochemistry, and physiology of a coccolithophore bloom. High numbers of Emiliania huxleyi cells and detached coccoliths (>1 × 103 mL-1 and >10 × 103 mL-1, respectively), high particulate inorganic carbon concentrations (>10 mmol C m-2), and high calcite production (up to 7.3 mmol C m-2 d-1) all characterized bloom waters. The bloom was dominated by the low-calcite-containing B/C morphotype of Emiliania huxleyi, although a small (30%, similar to estimates for E. huxleyi and indicative of a significant role for this diatom in bloom biogeochemistry. Cell-normalized calcification rates, when corrected for a high number of nonactive cells, were relatively high and when normalized to estimates of coccolith calcite indicate excessive coccolith production in the declining phase of the bloom. We find that low measures of calcite and calcite production relative to other blooms in the global ocean indicate that the dominance of the B/C morphotype may lead to overall lower calcite production. Globally, this suggests that morphotype composition influences regional bloom inventories of carbonate production and export and that climate-induced changes in morphotype biogeography could affect the carbon cycle.

  17. Ecosystem biogeochemistry considered as a distributed metabolic network ordered by maximum entropy production.

    Science.gov (United States)

    Vallino, Joseph J

    2010-05-12

    We examine the application of the maximum entropy production principle for describing ecosystem biogeochemistry. Since ecosystems can be functionally stable despite changes in species composition, we use a distributed metabolic network for describing biogeochemistry, which synthesizes generic biological structures that catalyse reaction pathways, but is otherwise organism independent. Allocation of biological structure and regulation of biogeochemical reactions is determined via solution of an optimal control problem in which entropy production is maximized. However, because synthesis of biological structures cannot occur if entropy production is maximized instantaneously, we propose that information stored within the metagenome allows biological systems to maximize entropy production when averaged over time. This differs from abiotic systems that maximize entropy production at a point in space-time, which we refer to as the steepest descent pathway. It is the spatio-temporal averaging that allows biological systems to outperform abiotic processes in entropy production, at least in many situations. A simulation of a methanotrophic system is used to demonstrate the approach. We conclude with a brief discussion on the implications of viewing ecosystems as self-organizing molecular machines that function to maximize entropy production at the ecosystem level of organization.

  18. Alquimia: Exposing mature biogeochemistry capabilities for easier benchmarking and development of next-generation subsurface codes

    Science.gov (United States)

    Johnson, J. N.; Molins, S.

    2015-12-01

    The complexity of subsurface models is increasing in order to address pressing scientific questions in hydrology and climate science. In particular, models that attempt to explore the coupling between microbial metabolic activity and hydrology at larger scales need an accurate representation of their underlying biogeochemical systems. These systems tend to be very complicated, and they result in large nonlinear systems that have to be coupled with flow and transport algorithms in reactive transport codes. The complexity inherent in implementing a robust treatment of biogeochemistry is a significant obstacle in the development of new codes. Alquimia is an open-source software library intended to help developers of these codes overcome this obstacle by exposing tried-and-true biogeochemical capabilities in existing software. It provides an interface through which a reactive transport code can access and evolve a chemical system, using one of several supported geochemical "engines." We will describe Alquimia's current capabilities, and how they can be used for benchmarking reactive transport codes. We will also discuss upcoming features that will facilitate the coupling of biogeochemistry to other processes in new codes.

  19. Biogeochemistry of sulfur and iron in Thioploca-colonized surface sediments in the upwelling area off central Chile

    DEFF Research Database (Denmark)

    Zopfi, Jakob; Michael E., Böttcher; Jørgensen, Bo Barker

    2008-01-01

    The biogeochemistry of sedimentary sulfur was investigated on the continental shelf off central Chile at water depths between 24 and 88 m under partial influence of an oxygen minimum zone. Dissolved and solid iron and sulfur species, including the sulfur intermediates sulfite, thiosulfate...

  20. Effective Management of Ocean Biogeochemistry and Ecological Data: the BCO-DMO Story

    Science.gov (United States)

    Chandler, C. L.; Groman, R. C.; Allison, M. D.; Wiebe, P. H.; Glover, D. M.; Gegg, S. R.

    2012-04-01

    Data availability expectations of the research community, environmental management decision makers, and funding agency representatives are changing. Consequently, data management practices in many science communities are changing as well. In an effort to improve access to data generated by ocean biogeochemistry and ecological researchers funded by the United States (US) National Science Foundation (NSF) Division of Ocean Sciences (OCE), the Biological and Chemical Oceanography Data Management Office (BCO-DMO) was created in late 2006. Currently, the main BCO-DMO objective is to ensure availability of data resulting from select OCE and Office of Polar Programs (OPP) research awards granted by the US NSF. An important requirement for the BCO-DMO data management system is that it provides open access to data that are supported by sufficient metadata to enable data discovery and accurate reuse. The office manages and serves all types of oceanographic data (in situ, experimental, model results) generated during the research process and contributed by the originating investigators from large national programs and medium-sized collaborative research projects, as well as researchers with single investigator awards. BCO-DMO staff members have made strategic use of standards and use of terms from controlled vocabularies while balancing the need to maintain flexible data ingest systems that accommodate the heterogeneous nature of ocean biogeochemistry and ecological research data. Many of the discrete ocean biogeochemistry data sets managed by BCO-DMO are still acquired manually, often with prototype sensor systems. Data sets such as these that are not "born-digital" present a significant management challenge. Use of multiple levels of term-mappings and development of an ontology has enabled BCO-DMO to incorporate a semantically enabled faceted search into the data access system that will improve data access through enhanced data discovery. BCO-DMO involves an ongoing

  1. Observed 20th century desert dust variability: impact on climate and biogeochemistry

    Directory of Open Access Journals (Sweden)

    N. M. Mahowald

    2010-11-01

    Full Text Available Desert dust perturbs climate by directly and indirectly interacting with incoming solar and outgoing long wave radiation, thereby changing precipitation and temperature, in addition to modifying ocean and land biogeochemistry. While we know that desert dust is sensitive to perturbations in climate and human land use, previous studies have been unable to determine whether humans were increasing or decreasing desert dust in the global average. Here we present observational estimates of desert dust based on paleodata proxies showing a doubling of desert dust during the 20th century over much, but not all the globe. Large uncertainties remain in estimates of desert dust variability over 20th century due to limited data. Using these observational estimates of desert dust change in combination with ocean, atmosphere and land models, we calculate the net radiative effect of these observed changes (top of atmosphere over the 20th century to be −0.14 ± 0.11 W/m2 (1990–1999 vs. 1905–1914. The estimated radiative change due to dust is especially strong between the heavily loaded 1980–1989 and the less heavily loaded 1955–1964 time periods (−0.57 ± 0.46 W/m2, which model simulations suggest may have reduced the rate of temperature increase between these time periods by 0.11 °C. Model simulations also indicate strong regional shifts in precipitation and temperature from desert dust changes, causing 6 ppm (12 PgC reduction in model carbon uptake by the terrestrial biosphere over the 20th century. Desert dust carries iron, an important micronutrient for ocean biogeochemistry that can modulate ocean carbon storage; here we show that dust deposition trends increase ocean productivity by an estimated 6% over the 20th century, drawing down an additional 4 ppm (8 PgC of carbon dioxide into the oceans. Thus, perturbations to desert dust over the 20th century inferred from observations are potentially important for climate and

  2. A mechanistic soil biogeochemistry model with explicit representation of microbial and macrofaunal activities and nutrient cycles

    Science.gov (United States)

    Fatichi, Simone; Manzoni, Stefano; Or, Dani; Paschalis, Athanasios

    2016-04-01

    The potential of a given ecosystem to store and release carbon is inherently linked to soil biogeochemical processes. These processes are deeply connected to the water, energy, and vegetation dynamics above and belowground. Recently, it has been advocated that a mechanistic representation of soil biogeochemistry require: (i) partitioning of soil organic carbon (SOC) pools according to their functional role; (ii) an explicit representation of microbial dynamics; (iii) coupling of carbon and nutrient cycles. While some of these components have been introduced in specialized models, they have been rarely implemented in terrestrial biosphere models and tested in real cases. In this study, we combine a new soil biogeochemistry model with an existing model of land-surface hydrology and vegetation dynamics (T&C). Specifically the soil biogeochemistry component explicitly separates different litter pools and distinguishes SOC in particulate, dissolved and mineral associated fractions. Extracellular enzymes and microbial pools are explicitly represented differentiating the functional roles of bacteria, saprotrophic and mycorrhizal fungi. Microbial activity depends on temperature, soil moisture and litter or SOC stoichiometry. The activity of macrofauna is also modeled. Nutrient dynamics include the cycles of nitrogen, phosphorous and potassium. The model accounts for feedbacks between nutrient limitations and plant growth as well as for plant stoichiometric flexibility. In turn, litter input is a function of the simulated vegetation dynamics. Root exudation and export to mycorrhiza are computed based on a nutrient uptake cost function. The combined model is tested to reproduce respiration dynamics and nitrogen cycle in few sites where data were available to test plausibility of results across a range of different metrics. For instance in a Swiss grassland ecosystem, fine root, bacteria, fungal and macrofaunal respiration account for 40%, 23%, 33% and 4% of total belowground

  3. Observed 20th Century Desert Dust Variability: Impact on Climate and Biogeochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Mahowald, Natalie [Cornell University; Kloster, Silvia [Cornell University; Engelstaedter, S. [Cornell University; Moore, Jefferson Keith [University of California, Irvine; Mukhopadhyay, S. [Harvard University; McConnell, J. R. [Desert Research Institute, Reno, NV; Albani, S. [Cornell University; Doney, Scott C. [Woods Hole Oceanographic Institution (WHOI), Woods Hole, MA; Bhattacharya, A. [Harvard University; Curran, M. A. J. [Antarctic Climate and Ecosystems Cooperative Research Centre; Flanner, Mark G. [University of Michigan; Hoffman, Forrest M [ORNL; Lawrence, David M. [National Center for Atmospheric Research (NCAR); Lindsay, Keith [National Center for Atmospheric Research (NCAR); Mayewski, P. A. [University of Maine; Neff, Jason [University of Colorado, Boulder; Rothenberg, D. [Cornell University; Thomas, E. [British Antarctic Survey, Cambridge, UK; Thornton, Peter E [ORNL; Zender, Charlie S. [University of California, Irvine

    2010-01-01

    Desert dust perturbs climate by directly and indirectly interacting with incoming solar and outgoing long wave radiation, thereby changing precipitation and temperature, in addition to modifying ocean and land biogeochemistry. While we know that desert dust is sensitive to perturbations in climate and human land use, previous studies have been unable to determine whether humans were increasing or decreasing desert dust in the global average. Here we present observational estimates of desert dust based on paleodata proxies showing a doubling of desert dust during the 20th century over much, but not all the globe. Large uncertainties remain in estimates of desert dust variability over 20th century due to limited data. Using these observational estimates of desert dust change in combination with ocean, atmosphere and land models, we calculate the net radiative effect of these observed changes (top of atmosphere) over the 20th century to be -0.14 {+-} 0.11 W/m{sup 2} (1990-1999 vs. 1905-1914). The estimated radiative change due to dust is especially strong between the heavily loaded 1980-1989 and the less heavily loaded 1955-1964 time periods (-0.57 {+-} 0.46 W/m{sup 2}), which model simulations suggest may have reduced the rate of temperature increase between these time periods by 0.11 C. Model simulations also indicate strong regional shifts in precipitation and temperature from desert dust changes, causing 6 ppm (12 PgC) reduction in model carbon uptake by the terrestrial biosphere over the 20th century. Desert dust carries iron, an important micronutrient for ocean biogeochemistry that can modulate ocean carbon storage; here we show that dust deposition trends increase ocean productivity by an estimated 6% over the 20th century, drawing down an additional 4 ppm (8 PgC) of carbon dioxide into the oceans. Thus, perturbations to desert dust over the 20th century inferred from observations are potentially important for climate and biogeochemistry, and our understanding

  4. Observed 20th century desert dust variability: impact on climate and biogeochemistry

    Directory of Open Access Journals (Sweden)

    N. M. Mahowald

    2010-05-01

    Full Text Available Desert dust perturbs climate by interacting with incoming solar and outgoing long wave radiation, thereby changing precipitation and temperature, in addition to modifying ocean and land biogeochemistry. While we know that desert dust is sensitive to perturbations in climate and human land use, previous studies have been unable to determine whether humans were in the net increasing or decreasing desert dust. Here we present observational estimates of desert dust based on paleodata proxies showing a doubling of desert dust during the 20th century over much, but not all the globe. Large uncertainties remain in estimates of desert dust variability over 20th century due to limited data. Using these observational estimates of desert dust change in combination with ocean, atmosphere and land models, we calculate the net radiative effect of these observed changes (top of atmosphere over the 20th century to be −0.14±0.11 W/m2 (1990–1999 vs. 1905–1914. The estimated radiative change due to aerosols is especially strong between the dusty 1980–1989 and the less dusty 1955–1964 time periods (−0.57±0.46 W/m2, which model simulations suggest may have reduced the rate of temperature increase between these time periods by 0.11 °C. Model simulations also indicate strong regional shifts in precipitation and temperature from the desert dust changes, causing 6 ppm (12 Pg C reduction in model carbon uptake by the terrestrial biosphere over the 20th century. Desert dust carries iron, an important micronutrient for ocean biogeochemistry that can modulate ocean carbon storage; here we show that dust deposition trends increase ocean productivity by an estimated 6% over the 20th century, drawing down an additional 4 ppm (8 Pg C of carbon dioxide into the oceans. Thus, perturbations to desert dust over the 20th century inferred from observations are potentially important for climate and biogeochemistry, and our understanding of these

  5. Hydrothermal Biogeochemistry

    Science.gov (United States)

    Shock, E.; Havig, J.; Windman, T.; Meyer-Dombard, D.; Michaud, A.; Hartnett, H.

    2006-12-01

    Life in hot spring ecosystems is confronted with diverse challenges, and the responses to those challenges have dynamic biogeochemical consequences over narrow spatial and temporal scales. Within meters along hot spring outflow channels at Yellowstone, temperatures drop from boiling, and the near-boiling conditions of hot chemolithotrophic communities, to those that permit photosynthesis and on down to conditions where nematodes and insects graze on the edges of photosynthetic mats. Many major and trace element concentrations change only mildly in the water that flows through the entire ecosystem, while concentrations of other dissolved constituents (oxygen, sulfide, ammonia, total organic carbon) increase or decrease dramatically. Concentrations of metals and micronutrients range from toxic to inadequate for enzyme synthesis depending on the choice of hot spring. Precipitation of minerals may provide continuous growth of microbial niches, while dissolution and turbulent flow sweeps them away. Consequently, microbial communities change at the meter scale, and even more abruptly at the photosynthetic fringe. Isotopic compositions of carbon and nitrogen in microbial biomass reflect dramatic and continuous changes in metabolic strategies throughout the system. Chemical energy sources that support chemolithotrophic communities can persist at abundant or useless levels, or change dramatically owing to microbial activity. The rate of temporal change depends on the selection of hot spring systems for study. Some have changed little since our studies began in 1999. Others have shifted by two or more units in pH over several years, with corresponding changes in other chemical constituents. Some go through daily or seasonal desiccation cycles, and still others exhibit pulses of changing temperature (up to 40°C) within minutes. Taken together, hydrothermal ecosystems provide highly manageable opportunities for testing how biogeochemical processes respond to the scale of temporal, spatial, and compositional changes.

  6. Rapid reorganization in ocean biogeochemistry off Peru towards the end of the Little Ice Age

    Directory of Open Access Journals (Sweden)

    D. Gutiérrez

    2008-09-01

    Full Text Available Climate and ocean ecosystem variability has been well recognized during the twentieth century but it is unclear if modern ocean biogeochemistry is susceptible to the large, abrupt shifts that characterized the Late Quaternary. Time series from marine sediments off Peru show an abrupt centennial-scale biogeochemical regime shift in the early nineteenth century, of much greater magnitude and duration than present day multi-decadal variability. A rapid expansion of the subsurface nutrient-rich, oxygen-depleted waters resulted in higher biological productivity, including pelagic fish. The shift was likely driven by a northward migration of the Intertropical Convergence Zone and the South Pacific Subtropical High to their present day locations, coupled with a strengthening of Walker circulation, towards the end of the Little Ice Age. These findings reveal the potential for large reorganizations in tropical Pacific climate with immediate effects on ocean biogeochemical cycling and ecosystem structure.

  7. Nano-Scale Secondary Ion Mass Spectrometry - A new analytical tool in biogeochemistry and soil ecology

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, A M; Ritz, K; Nunan, N; Clode, P L; Pett-Ridge, J; Kilburn, M R; Murphy, D V; O' Donnell, A G; Stockdale, E A

    2006-10-18

    Soils are structurally heterogeneous across a wide range of spatio-temporal scales. Consequently, external environmental conditions do not have a uniform effect throughout the soil, resulting in a large diversity of micro-habitats. It has been suggested that soil function can be studied without explicit consideration of such fine detail, but recent research has indicated that the micro-scale distribution of organisms may be of importance for a mechanistic understanding of many soil functions. Due to a lack of techniques with adequate sensitivity for data collection at appropriate scales, the question 'How important are various soil processes acting at different scales for ecological function?' is challenging to answer. The nano-scale secondary ion mass spectrometer (NanoSIMS) represents the latest generation of ion microprobes which link high-resolution microscopy with isotopic analysis. The main advantage of NanoSIMS over other secondary ion mass spectrometers is the ability to operate at high mass resolution, whilst maintaining both excellent signal transmission and spatial resolution ({approx}50 nm). NanoSIMS has been used previously in studies focusing on presolar materials from meteorites, in material science, biology, geology and mineralogy. Recently, the potential of NanoSIMS as a new tool in the study of biophysical interfaces in soils has been demonstrated. This paper describes the principles of NanoSIMS and discusses the potential of this tool to contribute to the field of biogeochemistry and soil ecology. Practical considerations (sample size and preparation, simultaneous collection of isotopes, mass resolution, isobaric interference and quantification of the isotopes of interest) are discussed. Adequate sample preparation avoiding biases in the interpretation of NanoSIMS data due to artifacts and identification of regions-of interest are of most concerns in using NanoSIMS as a new tool in biogeochemistry and soil ecology. Finally, we review

  8. Quantifying the roles of ocean circulation and biogeochemistry in governing ocean carbon-13 and atmospheric carbon dioxide at the last glacial maximum

    OpenAIRE

    Tagliabue, A.; L. Bopp; Roche, D. M.; N. Bouttes; J.-C. Dutay; Alkama, R.; Kageyama, M.; Michel, E.; Paillard, D.

    2009-01-01

    We use a state-of-the-art ocean general circulation and biogeochemistry model to examine the impact of changes in ocean circulation and biogeochemistry in governing the change in ocean carbon-13 and atmospheric CO2 at the last glacial maximum (LGM). We examine 5 different realisations of the ocean's overturning circulation produced by a fully coupled atmosphere-ocean model under LGM forcing and suggested changes in the atmospheric deposition of iron and phytoplankton ph...

  9. Biogeochemistry of a Field-Scale Sulfate Reducing Bioreactor Treating Mining Influenced Water

    Science.gov (United States)

    Drennan, D.; Lee, I.; Landkamer, L.; Figueroa, L. A.; Webb, S.; Sharp, J. O.

    2012-12-01

    Acidity, metal release, and toxicity may be environmental health concerns in areas influenced by mining. Mining influenced waters (MIW) can be remediated through the establishment of Sulfate Reducing Bioreactors (SRBRs) as part of engineered passive treatment systems. The objective of our research is an enhanced understanding of the biogeochemistry in SRBRs by combining molecular biological and geochemical techniques. Bioreactor reactive substrate, settling pond water, and effluent (from the SRBR) were collected from a field scale SRBR in Arizona, which has been in operation for approximately 3 years. Schematically, the water passes through the SRBR; combines with flow that bypasses the SRBR into the and goes into the mixing pond, and finally is released as effluent to aerobic polishing cells. High throughput sequencing of extracted DNA revealed that Proteobacteria dominated the reactive substrate (61%), settling pond (93%), and effluent (50%), with the next most abundant phylum in all samples (excluding uncultured organisms) being Bacteriodes (1-17%). However, at the superclass level, the three samples were more variable. Gammaproteobacteria dominated the reactive substrate (35%), Betaproteobacteria in the settling pond (63%) and finally the effluent was dominated by Epsilonproteobacteria (Helicobacteraceae) (43%). Diversity was most pronounced in association with the reactor matrix, and least diverse in the settling pond. Putative functional analysis revealed a modest presence of sulfate/sulfur reducing bacteria (SRB) (>5%) in both the matrix and settling pond but a much higher abundance (43%) of sulfur reducing bacteria in the effluent. Interestingly this effluent population was composed entirely of the family Helicobacteraceae (sulfur reduction II via polysulfide pathway). Other putative functions of interest include metal reduction in the matrix (3%) and effluent (3%), as well as polysaccharide degradation, which was largely abundant in all samples (21

  10. Benthic foraminiferal bathymetry and sea-bed biogeochemistry in the Gulf of Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Loubere, P. (Northern Illinois Univ., DeKalb, IL (United States). Dept. of Geology); Gary, A. (Unocal, Brea, CA (United States). Science and Technology Div.)

    1992-01-01

    Box cores were collected down the slope of the northwest Gulf of Mexico so that the sea-bed biogeochemistry could be compared to established benthic Foraminiferal bathymetric zonations. Pore water geochemistry along with water columns and sedimentologic analyses were used to quantify bottom water temperatures, organic carbon flux, bottom water oxygen content and sedimentary environment. The prominent Foraminiferal boundary between 170 and 200m water depth is associated with position of the mud-line in the northwestern Gulf. Deeper than this, assemblage changes are more gradational and, between 200 and 600m, appear related to gradients in temperature, oxygen supply and organic carbon flux. Between 600 and 2,000m bathymetric zonation correlates to the organic carbon flux profile. An analysis of sediment pore water geochemistry and sedimentary features in the box cores shows that there is a progressive change in the vertical distribution and character of potential microhabitats within the sediments down the slope of the northwest Gulf. This gradient in habitats must influence the generation of benthic Foraminiferal assemblages, and it is largely controlled by the organic carbon flux to the sea-bed.

  11. EMSL Geochemistry, Biogeochemistry and Subsurface Science-Science Theme Advisory Panel Meeting

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Gordon E.; Chaka, Anne; Shuh, David K.; Roden, Eric E.; Werth, Charles J.; Hess, Nancy J.; Felmy, Andrew R.; Rosso, Kevin M.; Baer, Donald R.; Bailey, Vanessa L.; Bowden, Mark E.; Grate, Jay W.; Hoyt, David W.; Kuprat, Laura R.; Lea, Alan S.; Mueller, Karl T.; Oostrom, Martinus; Orr, Galya; Pasa-Tolic, Ljiljana; Plata, Charity; Robinson, E. W.; Teller, Raymond G.; Thevuthasan, Suntharampillai; Wang, Hongfei; Wiley, H. S.; Wilkins, Michael J.

    2011-08-01

    This report covers the topics of discussion and the recommendations of the panel members. On December 8 and 9, 2010, the Geochemistry, Biogeochemistry, and Subsurface Science (GBSS) Science Theme Advisory Panel (STAP) convened for a more in-depth exploration of the five Science Theme focus areas developed at a similar meeting held in 2009. The goal for the fiscal year (FY) 2011 meeting was to identify potential topical areas for science campaigns, necessary experimental development needs, and scientific members for potential research teams. After a review of the current science in each of the five focus areas, the 2010 STAP discussions successfully led to the identification of one well focused campaign idea in pore-scale modeling and five longer-term potential research campaign ideas that would likely require additional workshops to identify specific research thrusts. These five campaign areas can be grouped into two categories: (1) the application of advanced high-resolution, high mass accuracy experimental techniques to elucidate the interplay between geochemistry and microbial communities in terrestrial ecosystems and (2) coupled computation/experimental investigations of the electron transfer reactions either between mineral surfaces and outer membranes of microbial cells or between the outer and inner membranes of microbial cells.

  12. Stable Isotope Biogeochemistry of the Centennial Re-survey of the San Jacinto Mountains, CA

    Science.gov (United States)

    Fogel, M. L.; Swarth, E.; Swarth, C.; Smith-Herman, N.; Tremor, S.; Unitt, P.

    2009-12-01

    In 1908, the San Jacinto Mountains were first surveyed for their animal and plant diversity by Joseph Grinnell and Harry Swarth, Museum of Vertebrate Zoology, UC Berkeley. In 2008, continuing until 2011, the ecology and stable isotope biogeochemistry of the plants, insects, birds, and mammals is being re-surveyed. Results of carbon, nitrogen, and hydrogen isotopes in organic matter show the variation in regional climate and trophic structure. For example, δ15N of plants at more arid stations are more positive by 3-5‰. Plants on westward facing slopes have more negative δ15N (to -6‰) possibly indicating N sources from atmospheric N deposition originating from urban Los Angeles. Isotopic analyses of recent collections will be compared with historic, museum archived specimens of plants and resident birds species. Our initial results show that the carbon isotopic compositions of plants collected in 1908 and during the early part of the 20th century are 1.6‰ enriched in δ13C, as predicted with the rise in industrially influenced atmospheric CO2. Isotopic data will be augmented by species diversity to test the hypothesis that 100 years of human influence has affected the ecosystem in this area and in what manner.

  13. Critical zone study in Korea: integration of hydrogeology, mineralogy, sedimentology and molecular biogeochemistry

    Science.gov (United States)

    Lee, J. Y.; Kwon, K.; Jo, K. N.; Lee, J. S.

    2015-12-01

    Critical Zone (CZ) is the topmost layer of the Earth ranging from the vegetation canopy down to the soil, groundwater, and bedrock that sustains our ecosystem including human life. This CZ is being greatly influenced by the climate change and anthropogenic forces. We introduce the Critical Zone Frontier Research Laboratory (CFRL), a critical zone research lab recently funded by the Korean government for 2015-2020. The objective of CFRL is to unravel the relationships between climate and CZ changes to propose a prediction model for future responses of CZ to climate change. For this ultimate goal, we establish multiple CZ observatories in Kangwon areas and investigate soil, groundwater, and cave environments by integration of hydrogeology, mineralogy, sedimentology and molecular biogeochemistry. This study will enhance our understanding about CZ and local resolution of a climate change model. This research is financially supported by the Basic Research Laboratory Program through the National Research Foundation of Korea funded by the Ministry of Science, ICT and Future Planning.

  14. Integration of Biogeochemistry and Marine Ecosystem Model in Mercator-Ocean Systems

    Science.gov (United States)

    El Moussaoui, Abdelali; Dombrowsky, Eric; Moulin, Cyril; Bopp, Laurent; Aumont, Olivier

    2010-05-01

    Accounting for ocean biogeochemistry and marine ecosystem dynamic is of strong interest in the context of Earth System modelling to better represent the marine component to the global atmospheric cycle of greenhouse gazes that influence climate as CO2. Furthermore, treating the ocean as a whole is also the way to address large anthropogenic impacts on marine systems as climate change, nutrients loading, acidification, and eventually overfishing and habitat destructuring. To forecast how interactions between marine biogeochemical cycles and ecosystems respond to and force global change, several efforts have been promoted on biogeochemical integration into operational Mercator Ocean systems. The aim of this work is to implement a marine biogeochemical and ecosystem component at global scale into the MERCATOR operational system, using first PSY3 analysis at 1/4° then PSY4 at 1/12°. Previous works have conducted successfully the integration of a multi-nutrient and multi-plankton biogeochemical model (PISCES, N5P2Z2D2 type) into MERCATOR system. This allowed the use of MERCATOR operational analyses to drive near real time forecast of marine primary production. Results will be shown and advances on biogeochemical model integration within Mercator Systems will be discussed.

  15. Microbial communities and arsenic biogeochemistry at the outflow of an alkaline sulfide-rich hot spring

    Science.gov (United States)

    Jiang, Zhou; Li, Ping; van Nostrand, Joy D.; Zhang, Ping; Zhou, Jizhong; Wang, Yanhong; Dai, Xinyue; Zhang, Rui; Jiang, Dawei; Wang, Yanxin

    2016-04-01

    Alkaline sulfide-rich hot springs provide a unique environment for microbial community and arsenic (As) biogeochemistry. In this study, a representative alkaline sulfide-rich hot spring, Zimeiquan in the Tengchong geothermal area, was chosen to study arsenic geochemistry and microbial community using Illumina MiSeq sequencing. Over 0.26 million 16S rRNA sequence reads were obtained from 5-paired parallel water and sediment samples along the hot spring’s outflow channel. High ratios of As(V)/AsSum (total combined arsenate and arsenite concentrations) (0.59-0.78), coupled with high sulfide (up to 5.87 mg/L), were present in the hot spring’s pools, which suggested As(III) oxidation occurred. Along the outflow channel, AsSum increased from 5.45 to 13.86 μmol/L, and the combined sulfide and sulfate concentrations increased from 292.02 to 364.28 μmol/L. These increases were primarily attributed to thioarsenic transformation. Temperature, sulfide, As and dissolved oxygen significantly shaped the microbial communities between not only the pools and downstream samples, but also water and sediment samples. Results implied that the upstream Thermocrinis was responsible for the transformation of thioarsenic to As(III) and the downstream Thermus contributed to derived As(III) oxidation. This study improves our understanding of microbially-mediated As transformation in alkaline sulfide-rich hot springs.

  16. Advanced in situ spectroscopic techniques and their applications in environmental biogeochemistry: introduction to the special section.

    Science.gov (United States)

    Lombi, Enzo; Hettiarachchi, Ganga M; Scheckel, Kirk G

    2011-01-01

    Understanding the molecular-scale complexities and interplay of chemical and biological processes of contaminants at solid, liquid, and gas interfaces is a fundamental and crucial element to enhance our understanding of anthropogenic environmental impacts. The ability to describe the complexity of environmental biogeochemical reaction mechanisms relies on our analytical ability through the application and developmemnt of advanced spectroscopic techniques. Accompanying this introductory article are nine papers that either review advanced in situ spectroscopic methods or present original research utilizing these techniques. This collection of articles summarizes the challenges facing environmental biogeochemistry, highlights the recent advances and scientific gaps, and provides an outlook into future research that may benefit from the use of in situ spectroscopic approaches. The use of synchrotron-based techniques and other methods are discussed in detail, as is the importance to integrate multiple analytical approaches to confirm results of complementary procedures or to fill data gaps. We also argue that future direction in research will be driven, in addition to recent analytical developments, by emerging factors such as the need for risk assessment of new materials (i.e., nanotechnologies) and the realization that biogeochemical processes need to be investigated in situ under environmentally relevant conditions.

  17. Ocean biogeochemistry exhibits contrasting responses to a large scale reduction in dust deposition

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    A. Tagliabue

    2007-08-01

    Full Text Available Dust deposition of iron is thought to be an important control on ocean biogeochemistry and air-sea CO2 exchange. In this study, we examine the impact of a large scale, yet climatically realistic, reduction in the aeolian Fe input during a 240 year transient simulation. In contrast to previous studies, we find that the ocean biogeochemical cycles of carbon and nitrogen are relatively insensitive to a 60% reduction in Fe input from dust. Net primary productivity (NPP is reduced in the Fe limited regions, but the excess macronutrients that result are able to fuel additional NPP elsewhere. Overall, NPP and air-sea CO2 exchange are only reduced by around 3% between 1860 and 2100. While the nitrogen cycle is perturbed more significantly (by ~15%, reduced N2 fixation is balanced by a concomitant decline in denitrification. Feedbacks between N2 fixation and denitrification are controlled by variability in surface utilization of inorganic nitrogen and subsurface oxygen consumption, as well as the direct influence of Fe on N2 fixation. Overall, there is relatively little impact of reduced aeolian Fe input (<4% on cumulative CO2 fluxes over 240 years. The lower sensitivity of our model to changes in dust input is primarily due to the more detailed representation of the continental shelf Fe, which was absent in previous models.

  18. Insights on Biogeochemistry from the Triple Isotope System of Nitrate (Invited)

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    Meixner, T.; Michalski, G. M.; Dejwahk, N.; Riha, K. M.; Lohse, K. A.; Gallo, E. L.; McIntosh, J. C.; Brooks, P. D.

    2013-12-01

    Given its central role in biogeochemistry, its multiple valences and the reactive and unreactive gaseous forms, the nitrogen cycle has long proven a difficult biogeochemical system to unravel. The oxidized form of nitrogen, nitrate, has been of particular interest due to its hydrologic mobility and role as a common groundwater contaminant. While the use of δ15N and δ18O of nitrate have long helped us over the last decade to distinguish sources of contaminant and biogeochemical processes, such as nitrate reduction, the addition of Δ17O (the triple isotope approach) has quantified the variability and importance of atmospheric contributions of nitrate, as well as the fate and transport of nitrate in natural environments. In the process of following this atmospherically sourced nitrate through hydrologic systems we have been further able to elucidate the loss and transformation processes that influence nitrate of all origins in the environment. Here, we will highlight the utility of the triple isotope system in a semi-arid system with reference to studies in other settings. The Tucson basin has four main sources of nitrogen- atmospheric deposition, terrestrial N fixation, anthropogenic fertilizer, and sewage effluent. The triple isotope system enabled the identification of denitrification as a major loss pathway after effluent discharge. We were also able to quantify the contribution of atmospheric nitrate directly to the regional groundwater system, and identify spatial patterns in surface water and groundwater. By bringing additional nitrogen budget and tracer data to bear we were able to constrain the biogeochemical cycling of N in the Tucson basin. This study offers lessons for those working on the N cycle in other settings and the triple isotope system offers a unique tool to help isolate the different processes that influence nitrate concentrations in natural waters.

  19. No observed effect of ocean acidification on nitrogen biogeochemistry in a summer Baltic Sea plankton community

    Science.gov (United States)

    Paul, Allanah J.; Achterberg, Eric P.; Bach, Lennart T.; Boxhammer, Tim; Czerny, Jan; Haunost, Mathias; Schulz, Kai-Georg; Stuhr, Annegret; Riebesell, Ulf

    2016-07-01

    Nitrogen fixation by filamentous cyanobacteria supplies significant amounts of new nitrogen (N) to the Baltic Sea. This balances N loss processes such as denitrification and anammox, and forms an important N source supporting primary and secondary production in N-limited post-spring bloom plankton communities. Laboratory studies suggest that filamentous diazotrophic cyanobacteria growth and N2-fixation rates are sensitive to ocean acidification, with potential implications for new N supply to the Baltic Sea. In this study, our aim was to assess the effect of ocean acidification on diazotroph growth and activity as well as the contribution of diazotrophically fixed N to N supply in a natural plankton assemblage. We enclosed a natural plankton community in a summer season in the Baltic Sea near the entrance to the Gulf of Finland in six large-scale mesocosms (volume ˜ 55 m3) and manipulated fCO2 over a range relevant for projected ocean acidification by the end of this century (average treatment fCO2: 365-1231 µatm). The direct response of diazotroph growth and activity was followed in the mesocosms over a 47 day study period during N-limited growth in the summer plankton community. Diazotrophic filamentous cyanobacteria abundance throughout the study period and N2-fixation rates (determined only until day 21 due to subsequent use of contaminated commercial 15N-N2 gas stocks) remained low. Thus estimated new N inputs from diazotrophy were too low to relieve N limitation and stimulate a summer phytoplankton bloom. Instead, regeneration of organic N sources likely sustained growth in the plankton community. We could not detect significant CO2-related differences in neither inorganic nor organic N pool sizes, or particulate matter N : P stoichiometry. Additionally, no significant effect of elevated CO2 on diazotroph activity was observed. Therefore, ocean acidification had no observable impact on N cycling or biogeochemistry in this N-limited, post-spring bloom

  20. Geospatial observations on biodiversity and biogeochemistry of a tropical forest rhizosphere

    Science.gov (United States)

    Wolf, Jeffrey Arien

    Understanding the links between biodiversity and biogeochemistry in a spatial context within tropical forest plant communities is an unresolved problem. High plant diversity -- phylogenetic, functional, and genetic -- often characteristic of tropical forests, is poorly understood in the context of soils. I collected and georeferenced a large sample of surface soil cores (n=625, 6.25 cm diameter x 10 cm depth) from the Barro Colorado Island (BCI) 50 ha (0.5 km2) Forest Dynamics Plot (FDP), Republic of Panama (9.15 N, 79.8 W) -- described in Chapter One. In Chapter Two, I tested a commonly made assumption in research on plot scales in tropical forests, that abiotic controls entirely explain plot scale soil heterogeneity. To do this, I analyzed a high spatial resolution and multiple spatial scale (multiscale) set of topography features from airborne light detection and ranging (LiDAR), a bedrock map, and the geospatial soil chemical observations to test if abiotic controls (erosion, hydrology, bedrock) were sufficient to explain soil heterogeneity in the BCI tree community. In Chapter Three, I evaluate whether spatial variation in soil organic matter (SOM) and patterns of correlation with rock-derived nutrients are consistent with plants changing soils through litterfall. In Chapter Four, I document the first use of high-throughput DNA sequencing data for observing plant species roots in a tropical forest rhizosphere. The main findings of my dissertation are that at the plot scale in a tropical forest soil chemical heterogeneity was weakly related to abiotic controls and rock-derived macronutrients vary in association strength with soil organic matter in a manner consistent with plants exerting strong biotic controls on the spatial heterogeneity of soil calcium. Furthermore, that research is needed to understand plant nutrient cycling within the context of tropical forest plant communities.

  1. Imprint of past and present environmental conditions on microbiology and biogeochemistry of coastal Quaternary sediments

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    M. Beck

    2011-01-01

    Full Text Available To date, North Sea tidal-flat sediments have been intensively studied down to a depth of 5 m below seafloor (mbsf. However, little is known about the biogeochemistry, microbial abundance, and activity of sulfate reducers as well as methanogens in deeper layers. In this study, two 20 m-long cores were retrieved from the tidal-flat area of Spiekeroog Island, NW Germany. The drill sites were selected with a close distance of 900 m allowing to compare two depositional settings: first, a paleo-channel filled with Holocene sediments and second, a mainly Pleistocene sedimentary succession. Analyzing these cores, we wanted to test to which degree the paleo-environmental imprint is superimposed by present processes.

    In general, the numbers of bacterial 16S rRNA genes are one to two orders of magnitude higher than those of Archaea. The abundances of key genes for sulfate reduction and methanogenesis (dsrA and mcrA correspond to the sulfate and methane profiles. A co-variance of these key genes at sulfate-methane interfaces and enhanced ex situ AOM rates suggest that anaerobic oxidation of methane may occur in these layers. Microbial and biogeochemical profiles are vertically stretched relative to 5 m-deep cores from shallower sediments in the same study area, but still appear compressed compared to deep sea sediments. Our interdisciplinary analysis shows that the microbial abundances and metabolic rates are elevated in the Holocene compared to Pleistocene sediments. However, this is mainly due to present environmental conditions such as pore water flow and organic matter availability. The paleo-environmental imprint is still visible but superimposed by these processes.

  2. Paleo-environmental imprint on microbiology and biogeochemistry of coastal quaternary sediments

    Directory of Open Access Journals (Sweden)

    M. Beck

    2010-07-01

    Full Text Available To date, North Sea tidal flat sediments have been intensively studied down to a depth of 5 m below sea floor (mbsf. However, little is known about the biogeochemistry, microbial abundance, and activity of sulfate reducers as well of methanogens in deeper layers. For this study, we hypothesized that the imprint of the paleo-environment is reflected in current microbiogeochemical processes. Therefore, 20 m-long cores were retrieved from the tidal-flat area of Spiekeroog Island, NW Germany. Two drill sites were selected with a close distance of only 900 meters, but where sedimentation occurred under different environmental conditions: first, a paleo-channel filled with Holocene sediments and second, a mainly Pleistocene sedimentary succession. In general, the numbers of bacterial 16S rRNA genes are one to two orders of magnitude higher than those of Archaea. The abundances of key genes for sulfate reduction and methanogenesis (dsrA and mcrA correspond to the sulfate and methane profiles. A co-variance of these key genes at sulfate-methane interfaces and enhanced potential AOM rates suggest that anaerobic oxidation of methane may occur in these layers. Microbial and biogeochemical profiles are vertically stretched relative to 5 m-deep cores from shallower sediments in the same study area. Compared to the deep marine environment, the profiles are transitional between the shallow subsurface and the marine deep biosphere. Our interdisciplinary analysis shows that the microbial abundances and metabolic rates are elevated in the Holocene compared to Pleistocene sediments. However, this is mainly due to present environmental conditions such as pore water flow and organic matter availability. The paleo-environmental imprint is still visible but superimposed by these processes.

  3. Ba/Ca Ratios in North Pacific Bamboo Corals Record Changes in Intermediate Water Biogeochemistry

    Science.gov (United States)

    Serrato Marks, G.; LaVigne, M.; Hill, T. M.; Sauthoff, W.; Guilderson, T. P.; Roark, E. B.; Dunbar, R. B.

    2015-12-01

    Trace elemental ratios preserved in the skeleton of bamboo corals, which live for hundreds of years at >500m depth, have been utilized as archives of deep-ocean conditions. However, it was previously unclear whether trace element data from these corals were internally reproducible and could therefore be used as reliable climate proxies. This study tests the internal reproducibility of Ba/Ca in the calcite of nine bamboo corals to further develop a new proxy for dissolved Ba in seawater (BaSW). Trace element LA-ICP-MS data were collected along three replicate radii of varying lengths of the calcitic internodes of well-dated corals collected live from the Gulf of Alaska (720m and 643m) and the California Margin (870m, 1012m, 1295m, 1500m, 1521m, 1954m, and 2054m; samples from 1295-1521m are not yet dated). Data were aligned using visible bands measured with a petrographic microscope to account for irregular growth. Ba/Ca data filtered with a 50μm (1.5-2 year) moving average were reproducible within each coral to 2.9 ± 2.1% (n=3 radii/coral, 9 corals), suggesting that regional geochemical signals are recorded as reproducible Ba/Ca signals on >annual timescales. Coral Ba/Ca presents an excellent proxy for BaSW, which has been found to be correlated with refractory nutrients (e.g. silicate) and oxygen minima. Increasing BaSW with depth and increased variability near 1000m suggests that BaSW is not constant with depth or with time. Several factors, including barite saturation state, particulate organic carbon (POC) remineralization rate, and particle sinking time, may be involved in the observed changes in BaSW. Further examination of such mechanisms could provide new insights into modern changes in deep-sea biogeochemistry.

  4. Biogeochemistry of an Amazonian podzol-ferralsol soil system with white kaolin

    Science.gov (United States)

    Lucas, Y.; Montes, C. R.; Mounier, S.; Loustau Cazalet, M.; Ishida, D.; Achard, R.; Garnier, C.; Coulomb, B.; Melfi, A. J.

    2012-09-01

    The podzol-ferralsol soil systems, which cover great areas of Amazonia and other equatorial regions, are frequently associated with kaolin deposits and store and export large amounts of carbon. Although natural organic matter (NOM) plays a key role in their dynamics, little is known about their biogeochemistry. In order to assess the specific role of dissolved organic matter (DOM) on NOM storage in deep horizons and to determine possible relationships between kaolin formation and DOM properties, we studied the groundwater composition of a typical podzol-ferralsol soil catena from the Alto Rio Negro region, Brazil. Groundwater was sampled using tension-free lysimeters placed according to soil morphology. DOC, EH, pH, and dissolved Si, Al3+, Fe2+, and Fe3+ were analyzed for all samples and values are given in a database. Quantification of other dissolved ions, small carboxylic acids and SUVA254 index and acid-base microtitration was achieved on selected samples. Part of the DOM produced by the hydromorphic podzols is directly exported to the blackwater streams; another part percolates at greater depth, and more than 90% of it adsorbs in the Bh-Bhs horizons, allowing carbon storage at depth. Humic substances are preferentially adsorbed with regard to small carboxylic compounds. With regard to kaolin genesis, kaolinite precipitation is favored by Al release from NOM mineralization within the Bh-Bhs and kaolin bleaching is ensured by iron reduction due to acidity and relatively low EH. Fe2+ mobility can be related to small EH variations and enhanced by the significant concentration of small carboxylic acids. The long-term result of these processes is the thickening of the kaolin, and it can be inferred that kaolin is likely to occur where active, giant podzols are close to a slope gradient sufficient enough to lower the deep water table.

  5. BIBLE A whole-air sampling as a window on Asian biogeochemistry

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    Elliott, Scott; Blake, Donald R.; Blake, Nicola J.; Dubey, Manvendra K.; Rowland, F. Sherwood; Sive, Barkley C.; Smith, Felisa A.

    2003-02-01

    Asian trace gas and aerosol emissions into carbon, nitrogen, and other elemental cycles will figure prominently in near term Earth system evolution. Atmospheric hydrocarbon measurements resolve numerous chemical species and can be used to investigate sourcing for key geocarriers. A recent aircraft study of biomass burning and lightning (BIBLE A) explored the East Asian atmosphere and was unique in centering on the Indonesian archipelago. Samples of volatile organics taken over/between the islands of Japan, Saipan, Java, and Borneo are here examined as a guide to whole-air-based studies of future Asian biogeochemistry. The midlatitude onshore/offshore pulse and tropical convection strongly influence concentration distributions. As species of increasing molecular weight are considered, rural, combustion, and industrial source regimes emerge. Methane-rich inputs such as waste treatment and rice cultivation are evidenced in the geostrophic outflow. The Indonesian atmosphere is rich in biomass burning markers and also those of vehicular activity. Complexity of air chemistry in the archipelago is a direct reflection of diverse topography, land use, and local economies in a rapidly developing nation. Conspicuous in its absence is the fingerprint for liquefied petroleum gas leakage, but it can be expected to appear as demand for clean fossil fuels rises along with per capita incomes. Combustion tracers indicate high nitrogen mobilization rates, linking regional terrestrial geocycles with open marine ecosystems. Sea to air fluxes are superimposed on continental and marine backgrounds for the methyl halides. However, ocean hot spots are not coordinated and suggest an intricate subsurface kinetics. Levels of long-lived anthropogenic halocarbons attest to the success of international environmental treaties while reactive chlorine containing species track industrial air masses. The dozens of hydrocarbons resolvable by gas chromatographic methods will enable monitoring of

  6. Effects of canopy tree species on belowground biogeochemistry in a lowland wet tropical forest

    Science.gov (United States)

    Keller, Adrienne B.; Reed, Sasha C.; Townsend, Alan R.; Cleveland, Cory C.

    2013-01-01

    Tropical rain forests are known for their high biological diversity, but the effects of plant diversity on important ecosystem processes in this biome remain unclear. Interspecies differences in both the demand for nutrients and in foliar and litter nutrient concentrations could drive variations in both the pool sizes and fluxes of important belowground resources, yet our understanding of the effects and importance of aboveground heterogeneity on belowground biogeochemistry is poor, especially in the species-rich forests of the wet tropics. To investigate the effects of individual tree species on belowground biogeochemical processes, we used both field and laboratory studies to examine how carbon (C), nitrogen (N), and phosphorus (P) cycles vary under nine different canopy tree species – including three legume and six non-legume species – that vary in foliar nutrient concentrations in a wet tropical forest in southwestern Costa Rica. We found significant differences in belowground C, N and P cycling under different canopy tree species: total C, N and P pools in standing litter varied by species, as did total soil and microbial C and N pools. Rates of soil extracellular acid phosphatase activity also varied significantly among species and functional groups, with higher rates of phosphatase activity under legumes. In addition, across all tree species, phosphatase activity was significantly positively correlated with litter N/P ratios, suggesting a tight coupling between relative N and P inputs and resource allocation to P acquisition. Overall, our results suggest the importance of aboveground plant community composition in promoting belowground biogeochemical heterogeneity at relatively small spatial scales.

  7. Impact of enhanced vertical mixing on marine biogeochemistry: lessons for geo-engineering and natural variability

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    S. Dutreuil

    2009-01-01

    Full Text Available Artificially enhanced vertical mixing has been suggested as a means by which to fertilize the biological pump with subsurface nutrients and thus increase the oceanic CO2 sink. We use an ocean general circulation and biogeochemistry model (OGCBM to examine the impact of artificially enhanced vertical mixing on biological productivity and atmospheric CO2, as well as the climatically significant gases nitrous oxide (N2O and dimethyl sulphide (DMS during simulations between 2000 and 2020. Overall, we find a large increase in the amount of organic carbon exported from surface waters, but an overall increase in atmospheric CO2 concentrations by 2020. We quantified the individual effect of changes in dissolved inorganic carbon (DIC, alkalinity and biological production on the change in pCO2 at characteristic sites and found the increased vertical supply of carbon rich subsurface water to be primarily responsible for the enhanced CO2 outgassing, although increased alkalinity and, to a lesser degree, biological production can compensate in some regions. While ocean-atmosphere fluxes of DMS do increase slightly, which might reduce radiative forcing, the oceanic N2O source also expands. Our study has implications for understanding how natural variability in vertical mixing in different ocean regions (such as that observed recently in the Southern Ocean can impact the ocean CO2 sink via changes in DIC, alkalinity and carbon export.

  8. Biotic and human vulnerability to projected changes in ocean biogeochemistry over the 21st century.

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    Camilo Mora

    2013-10-01

    Full Text Available Ongoing greenhouse gas emissions can modify climate processes and induce shifts in ocean temperature, pH, oxygen concentration, and productivity, which in turn could alter biological and social systems. Here, we provide a synoptic global assessment of the simultaneous changes in future ocean biogeochemical variables over marine biota and their broader implications for people. We analyzed modern Earth System Models forced by greenhouse gas concentration pathways until 2100 and showed that the entire world's ocean surface will be simultaneously impacted by varying intensities of ocean warming, acidification, oxygen depletion, or shortfalls in productivity. In contrast, only a small fraction of the world's ocean surface, mostly in polar regions, will experience increased oxygenation and productivity, while almost nowhere will there be ocean cooling or pH elevation. We compiled the global distribution of 32 marine habitats and biodiversity hotspots and found that they would all experience simultaneous exposure to changes in multiple biogeochemical variables. This superposition highlights the high risk for synergistic ecosystem responses, the suite of physiological adaptations needed to cope with future climate change, and the potential for reorganization of global biodiversity patterns. If co-occurring biogeochemical changes influence the delivery of ocean goods and services, then they could also have a considerable effect on human welfare. Approximately 470 to 870 million of the poorest people in the world rely heavily on the ocean for food, jobs, and revenues and live in countries that will be most affected by simultaneous changes in ocean biogeochemistry. These results highlight the high risk of degradation of marine ecosystems and associated human hardship expected in a future following current trends in anthropogenic greenhouse gas emissions.

  9. Assimilation of remotely-sensed optical properties to improve marine biogeochemistry modelling

    Science.gov (United States)

    Ciavatta, Stefano; Torres, Ricardo; Martinez-Vicente, Victor; Smyth, Timothy; Dall'Olmo, Giorgio; Polimene, Luca; Allen, J. Icarus

    2014-09-01

    In this paper we evaluate whether the assimilation of remotely-sensed optical data into a marine ecosystem model improves the simulation of biogeochemistry in a shelf sea. A localized Ensemble Kalman filter was used to assimilate weekly diffuse light attenuation coefficient data, Kd(443) from SeaWiFs, into an ecosystem model of the western English Channel. The spatial distributions of (unassimilated) surface chlorophyll from satellite, and a multivariate time series of eighteen biogeochemical and optical variables measured in situ at one long-term monitoring site were used to evaluate the system performance for the year 2006. Assimilation reduced the root mean square error and improved the correlation with the assimilated Kd(443) observations, for both the analysis and, to a lesser extent, the forecast estimates, when compared to the reference model simulation. Improvements in the simulation of (unassimilated) ocean colour chlorophyll were less evident, and in some parts of the Channel the simulation of this data deteriorated. The estimation errors for the (unassimilated) in situ data were reduced for most variables with some exceptions, e.g. dissolved nitrogen. Importantly, the assimilation adjusted the balance of ecosystem processes by shifting the simulated food web towards the microbial loop, thus improving the estimation of some properties, e.g. total particulate carbon. Assimilation of Kd(443) outperformed a comparative chlorophyll assimilation experiment, in both the estimation of ocean colour data and in the simulation of independent in situ data. These results are related to relatively low error in Kd(443) data, and because it is a bulk optical property of marine ecosystems. Assimilation of remotely-sensed optical properties is a promising approach to improve the simulation of biogeochemical and optical variables that are relevant for ecosystem functioning and climate change studies.

  10. Skill assessment of three earth system models with common marine biogeochemistry

    Science.gov (United States)

    Séférian, Roland; Bopp, Laurent; Gehlen, Marion; Orr, James C.; Ethé, Christian; Cadule, Patricia; Aumont, Olivier; Salas y Mélia, David; Voldoire, Aurore; Madec, Gurvan

    2013-05-01

    We have assessed the ability of a common ocean biogeochemical model, PISCES, to match relevant modern data fields across a range of ocean circulation fields from three distinct Earth system models: IPSL-CM4-LOOP, IPSL-CM5A-LR and CNRM-CM5.1. The first of these Earth system models has contributed to the IPCC 4th assessment report, while the latter two are contributing to the ongoing IPCC 5th assessment report. These models differ with respect to their atmospheric component, ocean subgrid-scale physics and resolution. The simulated vertical distribution of biogeochemical tracers suffer from biases in ocean circulation and a poor representation of the sinking fluxes of matter. Nevertheless, differences between upper and deep ocean model skills significantly point to changes in the underlying model representations of ocean circulation. IPSL-CM5A-LR and CNRM-CM5.1 poorly represent deep-ocean circulation compared to IPSL-CM4-LOOP degrading the vertical distribution of biogeochemical tracers. However, their representations of surface wind, wind stress, mixed-layer depth and geostrophic circulations (e.g., Antarctic Circumpolar Current) have been improved compared to IPSL-CM4-LOOP. These improvements result in a better representation of large-scale structure of biogeochemical fields in the upper ocean. In particular, a deepening of 20-40 m of the summer mixed-layer depth allows to capture the 0-0.5 μgChl L-1 concentrations class of surface chlorophyll in the Southern Ocean. Further improvements in the representation of the ocean mixed-layer and deep-ocean ventilation are needed for the next generations of models development to better simulate marine biogeochemistry. In order to better constrain ocean dynamics, we suggest that biogeochemical or passive tracer modules should be used routinely for both model development and model intercomparisons.

  11. Groundwater arsenic contamination on the Ganges Delta: biogeochemistry, hydrology, human perturbations, and human suffering on a large scale

    Science.gov (United States)

    Harvey, Charles F.; Swartz, Christopher H.; Badruzzaman, Abu Bohran M.; Keon-Blute, Nicole; Yu, Winston; Ali, M. Ashraf; Jay, Jenny; Beckie, Roger; Niedan, Volker; Brabander, Daniel; Oates, Peter M.; Ashfaque, Khandaker N.; Islam, Shafiqul; Hemond, Harold F.; Ahmed, M. Feroze

    2005-02-01

    Over the last several decades, much of population of Bangladesh and West Bengal switched their water supply from surface water to groundwater. Tragically, much of the region's groundwater is dangerously contaminated by arsenic, and consumption of this water has already created severe health effects. Here we consider how groundwater flow may affect arsenic biogeochemistry and we compare the vertical patterns of groundwater chemistry at our intensive study site with the average values across the country. Detailed hydraulic data are presented from our field site that begins to characterize the groundwater flow system. To cite this article: C.F. Harvey et al., C. R. Geoscience 337 (2005).

  12. Iron biogeochemistry across marine systems at changing times – conclusions from the workshop held in Gothenburg, Sweden (14–16 May 2008

    Directory of Open Access Journals (Sweden)

    E. Breitbarth

    2009-07-01

    Full Text Available Based on an international workshop (Gothenburg, 14–16 May 2008, this review article aims to combine interdisciplinary knowledge from coastal and open ocean research on iron biogeochemistry. The major scientific findings of the past decade are structured into sections on natural and artificial iron fertilization, iron inputs into coastal and estuarine systems, colloidal iron and organic matter, and biological processes. Potential effects of global climate change, particularly ocean acidification, on iron biogeochemistry are discussed. The findings are synthesized into recommendations for future research areas.

  13. Impacts of mangrove density on surface sediment accretion, belowground biomass and biogeochemistry in Puttalam Lagoon, Sri Lanka

    Science.gov (United States)

    Phillips, D.H.; Kumara, M.P.; Jayatissa, L.P.; Krauss, Ken W.; Huxham, M.

    2017-01-01

    Understanding the effects of seedling density on sediment accretion, biogeochemistry and belowground biomass in mangrove systems can help explain ecological functioning and inform appropriate planting densities during restoration or climate change mitigation programs. The objectives of this study were to examine: 1) impacts of mangrove seedling density on surface sediment accretion, texture, belowground biomass and biogeochemistry, and 2) origins of the carbon (C) supplied to the mangroves in Palakuda, Puttalam Lagoon, Sri Lanka. Rhizophora mucronata propagules were planted at densities of 6.96, 3.26, 1.93 and 0.95 seedlings m−2along with an unplanted control (0 seedlings m−2). The highest seedling density generally had higher sediment accretion rates, finer sediments, higher belowground biomass, greatest number of fine roots and highest concentrations of C and nitrogen (N) (and the lowest C/N ratio). Sediment accretion rates, belowground biomass (over 1370 days), and C and N concentrations differed significantly between seedling densities. Fine roots were significantly greater compared to medium and coarse roots across all plantation densities. Sulphur and carbon stable isotopes did not vary significantly between different density treatments. Isotope signatures suggest surface sediment C (to a depth of 1 cm) is not derived predominantly from the trees, but from seagrass adjacent to the site.

  14. Potential effects of large-scale offshore tidal energy extraction in the Pentland Firth on North Sea biogeochemistry

    Science.gov (United States)

    van der Molen, Johan; Ruardij, Piet; Greenwood, Naomi

    2016-04-01

    Final results are presented of a model study to assess the potential wider area effects of large-scale tidal energy extraction in the Pentland Firth on the biogeochemistry. The coupled hydrodynamics-biogeochemistry model GETM-ERSEM-BFM was used in a shelf-wide application with a parameterisation of the effects of power extraction by tidal turbines on fluid momentum. Three secenario runs were carried out: a reference run without turbines, an 800 MW extraction run corresponding to current licenses, and an academic 8 GW extraction run. The changes simulated with the 800 MW extraction were negligible. The academic 8 GW extraction resulted in reductions in tidal elevations along the east coast of the UK that would be measurable (several cm.), and associated reductions in bed-shear stresses. These resulted in reductions in SPM concentrations, increased primary production, and increased biomass of zooplankton and benthic fauna. The effects were most pronounced in the shallow seas surrounding The Wash, with changes of up to 10%. These results indicate that, should tidal power generation substantially beyond the currently licensed amount be planned, either concentrated in one location or spread over multiple locations along the coast, further investigations are advisable.

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

    Science.gov (United States)

    Spivak, A.; Vanni, M. J.

    2010-12-01

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

  16. Link or sink: a modelling interpretation of the open Baltic biogeochemistry

    Directory of Open Access Journals (Sweden)

    J. W. Baretta

    2004-08-01

    Full Text Available A 1-D model system, consisting of the 1-D version of the Princeton Ocean Model (POM coupled with the European Regional Seas Ecosystem Model (ERSEM has been applied to a sub-basin of the Baltic Proper, the Bornholm basin. The model has been forced with 3h meteorological data for the period 1979-1990, producing a 12-year hindcast validated with datasets from the Baltic Environmental Database for the same period. The model results demonstrate the model to hindcast the time-evolution of the physical structure very well, confirming the view of the open Baltic water column as a three layer system of surface, intermediate and bottom waters. Comparative analyses of modelled hydrochemical components with respect to the independent data have shown that the long-term system behaviour of the model is within the observed ranges. Also primary production processes, deduced from oxygen (oversaturation are hindcast correctly over the entire period and the annual net primary production is within the observed range. The largest mismatch with observations is found in simulating the biogeochemistry of the Baltic intermediate waters. Modifications in the structure of the model (addition of fast-sinking detritus and polysaccharide dynamics have shown that the nutrient dynamics is linked to the quality and dimensions of the organic matter produced in the euphotic zone, highlighting the importance of the residence time of the organic matter within the microbial foodweb in the intermediate waters. Experiments with different scenarios of riverine nutrient loads, assessed in the limits of a 1-D setup, have shown that the external input of organic matter makes the open Baltic model more heterotrophic. The characteristics of the inputs also drive the dynamics of nitrogen in the bottom layers leading either to nitrate accumulation (when the external sources are inorganic, or to coupled nitrification-denitrification (under strong organic inputs. The model indicates the

  17. SEEDS for Big Dark Data Collection and Sharing in Biogeochemistry: LeafWeb as an Example

    Science.gov (United States)

    Gu, L.

    2015-12-01

    sharing. In this presentation, I will use LeafWeb (leafweb.ornl.gov) to demonstrate how the SEEDS principle can be implemented in the context of Earth system science and biogeochemistry.

  18. Biogeochemistry and biodiversity interact to govern N2 fixers (Fabaceae) across Amazon tropical forests

    Science.gov (United States)

    Batterman, Sarah; Hedin, Lars; Lloyd, Jon; Quesada, Beto

    2015-04-01

    Dinitrogen (N2)-fixing trees in the Fabaceae fulfill a central role in tropical rainforests by supplying nitrogen from the atmosphere, yet whether they will support a forest CO2 sink in the future by alleviating nitrogen limitation may depend on whether and how they are controlled by local environmental conditions. Theory predicts that soil nutrients govern the function of N2 fixers, yet there have been no large-scale field-based tests of this idea. Moreover, recent findings indicate that N2-fixing species behave differently in biogeochemical cycles, suggesting that any environmental control may differ by species, and that the diversity of N2-fixing trees may be critical for ensuring tropical forest function. In this talk, we will use the RAINFOR dataset of 108 (~1.0 ha) lowland tropical rainforest plots from across the Amazon Basin to test whether the abundance and diversity of N2-fixing trees are controlled by soil nutrient availability (i.e., increasing with phosphorus and decreasing with nitrogen), or if fixer abundance and diversity simply follow the dynamics of all tree species. We also test an alternative - but not mutually exclusive - hypothesis that the governing factor for fixers is forest disturbance. Results show a surprising lack of control by local nutrients or disturbance on the abundance or diversity of N2 fixers. The dominant driver of fixer diversity was the total number of tree species, with fixers comprising 10% of all species in a forest plot (R2 = 0.75, linear regression). When considering the dominant taxa of N2 fixers (Inga, Swartzia, Tachigali) alone, environmental factors (nitrogen, phosphorus and disturbance) became important and clearly governed their abundance. These taxa, which contain >60% of N2-fixing trees in the data set, appear to have evolved to specialize in different local environmental conditions. The strong biogeochemistry-by-biodiversity interaction observed here points to a need to consider individual species or taxa of N2

  19. Using Green's Functions to initialize and adjust a global, eddying ocean biogeochemistry general circulation model

    Science.gov (United States)

    Brix, H.; Menemenlis, D.; Hill, C.; Dutkiewicz, S.; Jahn, O.; Wang, D.; Bowman, K.; Zhang, H.

    2015-11-01

    The NASA Carbon Monitoring System (CMS) Flux Project aims to attribute changes in the atmospheric accumulation of carbon dioxide to spatially resolved fluxes by utilizing the full suite of NASA data, models, and assimilation capabilities. For the oceanic part of this project, we introduce ECCO2-Darwin, a new ocean biogeochemistry general circulation model based on combining the following pre-existing components: (i) a full-depth, eddying, global-ocean configuration of the Massachusetts Institute of Technology general circulation model (MITgcm), (ii) an adjoint-method-based estimate of ocean circulation from the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project, (iii) the MIT ecosystem model "Darwin", and (iv) a marine carbon chemistry model. Air-sea gas exchange coefficients and initial conditions of dissolved inorganic carbon, alkalinity, and oxygen are adjusted using a Green's Functions approach in order to optimize modeled air-sea CO2 fluxes. Data constraints include observations of carbon dioxide partial pressure (pCO2) for 2009-2010, global air-sea CO2 flux estimates, and the seasonal cycle of the Takahashi et al. (2009) Atlas. The model sensitivity experiments (or Green's Functions) include simulations that start from different initial conditions as well as experiments that perturb air-sea gas exchange parameters and the ratio of particulate inorganic to organic carbon. The Green's Functions approach yields a linear combination of these sensitivity experiments that minimizes model-data differences. The resulting initial conditions and gas exchange coefficients are then used to integrate the ECCO2-Darwin model forward. Despite the small number (six) of control parameters, the adjusted simulation is significantly closer to the data constraints (37% cost function reduction, i.e., reduction in the model-data difference, relative to the baseline simulation) and to independent observations (e.g., alkalinity). The adjusted air-sea gas

  20. IMBER (Integrated Marine Biogeochemistry and Ecosystem Research: Support of Ocean Carbon Research

    Science.gov (United States)

    Rimetz-Planchon, J.; Gattuso, J.; Maddison, L.; Bakker, D. C.; Gruber, N.

    2011-12-01

    IMBER (Integrated Marine Biogeochemistry and Ecosystem Research), co-sponsored by SCOR (Scientific Committee on Oceanic Research) and IGBP (International Geosphere-Biosphere Programme), coordinates research that focuses on understanding and predicting changes in oceanic food webs and biogeochemical cycles that arise from global change. An integral part of this overall goal is to understand the marine carbon cycle, with emphasis on changes that may occur as a result of a changing climate, increased atmospheric CO2 levels and/or reduced oceanic pH. To address these key ocean carbon issues, IMBER and SOLAS (Surface Ocean Lower Atmosphere Study), formed the joint SOLAS-IMBER Carbon, or SIC Working Group. The SIC Working Group activities are organised into three sub-groups. Sub-group 1 (Surface Ocean Systems) focuses on synthesis, instrumentation and technology development, VOS (Voluntary Observing Ships) and mixed layer sampling strategies. The group contributed to the development of SOCAT (Surface Ocean CO2 Atlas, www.socat.info), a global compilation of underway surface water fCO2 (fugacity of CO2) data in common format. It includes 6.3 million measurements from 1767 cruises from 1968 and 2008 by more than 10 countries. SOCAT will be publically available and will serve a wide range of user communities. Its public release is planned for September 2011. SOCAT is strongly supported by IOCCP and CARBOOCEAN. Sub-group 2 (Interior Ocean Carbon Storage) covers inventory and observations, natural variability, transformation and interaction with modelling. It coordinated a review of vulnerabilities of the decadal variations of the interior ocean carbon and oxygen cycle. It has also developed a plan to add dissolved oxygen sensors to the ARGO float program in order to address the expected loss of oxygen as a result of ocean warming. The group also focuses on the global synthesis of ocean interior carbon observations to determine the oceanic uptake of anthropogenic CO2 since

  1. Biogeochemistry and geomicrobiology of cold-water coral carbonate mounds - lessons learned from IODP Expedition 307

    Science.gov (United States)

    Ferdelman, Timothy; Wehrmann, Laura; Mangelsdorf, Kai; Kano, Akihiro; Williams, Trevor; Jean-Pierre, Henriet

    2010-05-01

    to be dominated by low rates of iron- and sulfate-reduction that occur in discrete layers within the mound. This was consistent with distributions of total cell-counts, acetate turnover (Webster et al. 2009) and hydrogenase activity (Soffiento et al. 2009). However, biomarker lipid distributions suggested that the Miocene sediments underlying the mound, into which sulfate is diffusing, as well as the sediments from the non-cold water coral reference site (U1318) contain higher abundances of living microbes. The results obtained from Expedition 307 are consistent with a picture emerging from other biogeochemical studies of cold-water coral mound and reef sites. Unless impacted by some external forcing (e.g. fluid flow or erosion event), the microbial activity in the underlying cold-water coral mound sediments is largely decoupled from the highly diverse, active surface ecosystem. References: Soffiento B, Spivack AJ, Smith DC, and D'Hondt S (2009) Hydrogenase activity in deeply buried sediments of the Arctic and North Atlantic Oceans. Geomicro. J. 26: 537-545. Webster, G, Blazejak A, Cragg BA, Schippers A, Sass H, Rinna J, Tang X, Mathes F, Ferdelman TG., Fry JC, Weightman AJ, and Parkes RJ. 2009. Subsurface microbiology and biogeochemistry of a deep, cold-water carbonate mound from the Porcupine Seabight (IODP Expediton 307). Env. Microbiol., 11, 239-257, doi:10.1111/j.1462-2920.01759.x.

  2. Microbial Community Structure and Arsenic Biogeochemistry in an Acid Vapor-Formed Spring in Tengchong Geothermal Area, China.

    Directory of Open Access Journals (Sweden)

    Zhou Jiang

    Full Text Available Arsenic biogeochemistry has been studied extensively in acid sulfate-chloride hot springs, but not in acid sulfate hot springs with low chloride. In this study, Zhenzhuquan in Tengchong geothermal area, a representative acid sulfate hot spring with low chloride, was chosen to study arsenic geochemistry and microbial community structure using Illumina MiSeq sequencing. Over 0.3 million 16S rRNA sequence reads were obtained from 6-paired parallel water and sediment samples along its outflow channel. Arsenic oxidation occurred in the Zhenxhuquan pool, with distinctly high ratios of arsenate to total dissolved arsenic (0.73-0.86. Coupled with iron and sulfur oxidation along the outflow channel, arsenic accumulated in downstream sediments with concentrations up to 16.44 g/kg and appeared to significantly constrain their microbial community diversity. These oxidations might be correlated with the appearance of some putative functional microbial populations, such as Aquificae and Pseudomonas (arsenic oxidation, Sulfolobus (sulfur and iron oxidation, Metallosphaera and Acidicaldus (iron oxidation. Temperature, total organic carbon and dissolved oxygen significantly shaped the microbial community structure of upstream and downstream samples. In the upstream outflow channel region, most microbial populations were microaerophilic/anaerobic thermophiles and hyperthermophiles, such as Sulfolobus, Nocardia, Fervidicoccus, Delftia, and Ralstonia. In the downstream region, aerobic heterotrophic mesophiles and thermophiles were identified, including Ktedonobacteria, Acidicaldus, Chthonomonas and Sphingobacteria. A total of 72.41-95.91% unassigned-genus sequences were derived from the downstream high arsenic sediments 16S rRNA clone libraries. This study could enable us to achieve an integrated understanding on arsenic biogeochemistry in acid hot springs.

  3. iMarNet: an ocean biogeochemistry model inter-comparison project within a common physical ocean modelling framework

    Directory of Open Access Journals (Sweden)

    L. Kwiatkowski

    2014-07-01

    Full Text Available Ocean biogeochemistry (OBGC models span a wide range of complexities from highly simplified, nutrient-restoring schemes, through nutrient-phytoplankton-zooplankton-detritus (NPZD models that crudely represent the marine biota, through to models that represent a broader trophic structure by grouping organisms as plankton functional types (PFT based on their biogeochemical role (Dynamic Green Ocean Models; DGOM and ecosystem models which group organisms by ecological function and trait. OBGC models are now integral components of Earth System Models (ESMs, but they compete for computing resources with higher resolution dynamical setups and with other components such as atmospheric chemistry and terrestrial vegetation schemes. As such, the choice of OBGC in ESMs needs to balance model complexity and realism alongside relative computing cost. Here, we present an inter-comparison of six OBGC models that were candidates for implementation within the next UK Earth System Model (UKESM1. The models cover a large range of biological complexity (from 7 to 57 tracers but all include representations of at least the nitrogen, carbon, alkalinity and oxygen cycles. Each OBGC model was coupled to the Nucleus for the European Modelling of the Ocean (NEMO ocean general circulation model (GCM, and results from physically identical hindcast simulations were compared. Model skill was evaluated for biogeochemical metrics of global-scale bulk properties using conventional statistical techniques. The computing cost of each model was also measured in standardised tests run at two resource levels. No model is shown to consistently outperform or underperform all other models across all metrics. Nonetheless, the simpler models that are easier to tune are broadly closer to observations across a number of fields, and thus offer a high-efficiency option for ESMs that prioritise high resolution climate dynamics. However, simpler models provide limited insight into more complex

  4. Microbial Community Structure and Arsenic Biogeochemistry in an Acid Vapor-Formed Spring in Tengchong Geothermal Area, China.

    Science.gov (United States)

    Jiang, Zhou; Li, Ping; Jiang, Dawei; Dai, Xinyue; Zhang, Rui; Wang, Yanhong; Wang, Yanxin

    2016-01-01

    Arsenic biogeochemistry has been studied extensively in acid sulfate-chloride hot springs, but not in acid sulfate hot springs with low chloride. In this study, Zhenzhuquan in Tengchong geothermal area, a representative acid sulfate hot spring with low chloride, was chosen to study arsenic geochemistry and microbial community structure using Illumina MiSeq sequencing. Over 0.3 million 16S rRNA sequence reads were obtained from 6-paired parallel water and sediment samples along its outflow channel. Arsenic oxidation occurred in the Zhenxhuquan pool, with distinctly high ratios of arsenate to total dissolved arsenic (0.73-0.86). Coupled with iron and sulfur oxidation along the outflow channel, arsenic accumulated in downstream sediments with concentrations up to 16.44 g/kg and appeared to significantly constrain their microbial community diversity. These oxidations might be correlated with the appearance of some putative functional microbial populations, such as Aquificae and Pseudomonas (arsenic oxidation), Sulfolobus (sulfur and iron oxidation), Metallosphaera and Acidicaldus (iron oxidation). Temperature, total organic carbon and dissolved oxygen significantly shaped the microbial community structure of upstream and downstream samples. In the upstream outflow channel region, most microbial populations were microaerophilic/anaerobic thermophiles and hyperthermophiles, such as Sulfolobus, Nocardia, Fervidicoccus, Delftia, and Ralstonia. In the downstream region, aerobic heterotrophic mesophiles and thermophiles were identified, including Ktedonobacteria, Acidicaldus, Chthonomonas and Sphingobacteria. A total of 72.41-95.91% unassigned-genus sequences were derived from the downstream high arsenic sediments 16S rRNA clone libraries. This study could enable us to achieve an integrated understanding on arsenic biogeochemistry in acid hot springs.

  5. Biogeochemistry of the Bay of Bengal: Physical, chemical and primary productivity characteristics of the central and western Bay of Bengal during summer monsoon 2001

    Digital Repository Service at National Institute of Oceanography (India)

    Madhupratap, M.; Gauns, M.; Ramaiah, N.; PrasannaKumar, S.; Muraleedharan, P.M.; DeSousa, S.N.; Sardessai, S.; Muraleedharan, U.D.

    . Both lie in the tropics and are relatively small basins coming under the influence of the seasonally reversing monsoons. They form excellent crucibles to study the variability in the biogeochemistry of the oceans. Differences between the physical... along the western margin (Fig. 1) were occupied, each for over a day, for measuring primary productivity and related parameters. Water samples collected from eight discrete depths (near surface, 10, 20 m and thereafter at 20 m intervals up to 120 m...

  6. Unravelling organic matter and nutrient biogeochemistry in groundwater-fed rivers under baseflow conditions: Uncertainty in in situ high-frequency analysis

    OpenAIRE

    M. Z. Bieroza; Heathwaite, A. L.

    2016-01-01

    In agricultural catchments, diffuse nutrient fluxes (mainly nitrogen N and phosphorus P), are observed to pollute receiving waters and cause eutrophication. Organic matter (OM) is important in mediating biogeochemical processes in freshwaters. Time series of the variation in nutrient and OM loads give insights into flux processes and their impact on biogeochemistry but are costly to maintain and challenging to analyse for elements that are highly reactive in the environment. We evaluated the ...

  7. How deep does disturbance go? The long-term effects of canopy disturbance on tropical forest soil biogeochemistry

    Science.gov (United States)

    Gutiérrez del Arroyo, O.; Silver, W. L.

    2015-12-01

    We used the Canopy Trimming Experiment (CTE), an ongoing ecosystem manipulation study in the Luquillo Experimental Forest (LEF), Puerto Rico to determine the decadal-scale effects of canopy disturbance and debris deposition on biogeochemistry throughout the soil profile of a wet tropical forest. These manipulations represent the most significant effects of hurricanes, which may increase in frequency or intensity with warming, strengthening their ecosystem-level effects on carbon (C) and nutrient cycling. Four replicated treatments were applied in 2005 using a complete randomized block design: canopy trimming + debris deposition, canopy trimming only, debris deposition only, and untreated control. In 2015, we sampled soils at 10 cm intervals to 1 m depth in each of 12 plots (3 per treatment). We measured gravimetric moisture content, pH, HCl and citrate-ascorbate (CA) extractable iron (Fe) species, organic (Po) and inorganic fractions of NaHCO3 and NaOH phosphorus (P), as well as total C and nitrogen (N). Soil moisture decreased markedly with depth up to ~60-70 cm, and then stabilized at ~33% down to 1 m. Across all treatments, pH increased significantly with depth, ranging from 4.6 in surface soils (0-10 cm) of trimmed plots to 5.2 in deep soils (80-90 cm) of control plots. Canopy trimming decreased pH significantly, possibly due to increased root activity in surface soils as vegetation recovered. Both HCl and CA extractable Fe showed strong depth dependance, decreasing linearly to 50 cm, and stabilizing at very low concentrations (soil profile (deposition significantly increased Po, revealing the role of hurricanes in subsidizing the available soil P pool in these highly productive, low-P wet tropical forests. Debris deposition also increased soil C and N concentrations in surface soils (soil profile in this wet tropical forest. However, effects were persistent and detectable after ten years of the CTE, suggesting that hurricanes result in long-term changes in

  8. Physico-Chemical Heterogeneity of Organic-Rich Sediments in the Rifle Aquifer, CO: Impact on Uranium Biogeochemistry.

    Science.gov (United States)

    Janot, Noémie; Lezama Pacheco, Juan S; Pham, Don Q; O'Brien, Timothy M; Hausladen, Debra; Noël, Vincent; Lallier, Florent; Maher, Kate; Fendorf, Scott; Williams, Kenneth H; Long, Philip E; Bargar, John R

    2016-01-01

    The Rifle alluvial aquifer along the Colorado River in west central Colorado contains fine-grained, diffusion-limited sediment lenses that are substantially enriched in organic carbon and sulfides, as well as uranium, from previous milling operations. These naturally reduced zones (NRZs) coincide spatially with a persistent uranium groundwater plume. There is concern that uranium release from NRZs is contributing to plume persistence or will do so in the future. To better define the physical extent, heterogeneity and biogeochemistry of these NRZs, we investigated sediment cores from five neighboring wells. The main NRZ body exhibited uranium concentrations up to 100 mg/kg U as U(IV) and contains ca. 286 g of U in total. Uranium accumulated only in areas where organic carbon and reduced sulfur (as iron sulfides) were present, emphasizing the importance of sulfate-reducing conditions to uranium retention and the essential role of organic matter. NRZs further exhibited centimeter-scale variations in both redox status and particle size. Mackinawite, greigite, pyrite and sulfate coexist in the sediments, indicating that dynamic redox cycling occurs within NRZs and that their internal portions can be seasonally oxidized. We show that oxidative U(VI) release to the aquifer has the potential to sustain a groundwater contaminant plume for centuries. NRZs, known to exist in other uranium-contaminated aquifers, may be regionally important to uranium persistence.

  9. Water column biogeochemistry of oxygen minimum zones in the eastern tropical North Atlantic and eastern tropical South Pacific oceans

    Science.gov (United States)

    Löscher, Carolin R.; Bange, Hermann W.; Schmitz, Ruth A.; Callbeck, Cameron M.; Engel, Anja; Hauss, Helena; Kanzow, Torsten; Kiko, Rainer; Lavik, Gaute; Loginova, Alexandra; Melzner, Frank; Meyer, Judith; Neulinger, Sven C.; Pahlow, Markus; Riebesell, Ulf; Schunck, Harald; Thomsen, Sören; Wagner, Hannes

    2016-06-01

    Recent modeling results suggest that oceanic oxygen levels will decrease significantly over the next decades to centuries in response to climate change and altered ocean circulation. Hence, the future ocean may experience major shifts in nutrient cycling triggered by the expansion and intensification of tropical oxygen minimum zones (OMZs), which are connected to the most productive upwelling systems in the ocean. There are numerous feedbacks among oxygen concentrations, nutrient cycling and biological productivity; however, existing knowledge is insufficient to understand physical, chemical and biological interactions in order to adequately assess past and potential future changes. In the following, we summarize one decade of research performed in the framework of the Collaborative Research Center 754 (SFB754) focusing on climate-biogeochemistry interactions in tropical OMZs. We investigated the influence of low environmental oxygen conditions on biogeochemical cycles, organic matter formation and remineralization, greenhouse gas production and the ecology in OMZ regions of the eastern tropical South Pacific compared to the weaker OMZ of the eastern tropical North Atlantic. Based on our findings, a coupling of primary production and organic matter export via the nitrogen cycle is proposed, which may, however, be impacted by several additional factors, e.g., micronutrients, particles acting as microniches, vertical and horizontal transport of organic material and the role of zooplankton and viruses therein.

  10. Developing a test-bed for robust research governance of geoengineering: the contribution of ocean iron biogeochemistry

    Science.gov (United States)

    Boyd, Philip W.; Bressac, Matthieu

    2016-11-01

    Geoengineering to mitigate climate change has long been proposed, but remains nebulous. Exploration of the feasibility of geoengineering first requires the development of research governance to move beyond the conceptual towards scientifically designed pilot studies. Fortuitously, 12 mesoscale (approx. 1000 km2) iron enrichments, funded to investigate how ocean iron biogeochemistry altered Earth's carbon cycle in the geological past, provide proxies to better understand the benefits and drawbacks of geoengineering. The utility of these iron enrichments in the geoengineering debate is enhanced by the GEOTRACES global survey. Here, we outline how GEOTRACES surveys and process studies can provide invaluable insights into geoengineering. Surveys inform key unknowns including the regional influence and magnitude of modes of iron supply, and stimulate iron biogeochemical modelling. These advances will enable quantification of interannual variability of iron supply to assess whether any future purposeful multi-year iron-fertilization meets the principle of `additionality' (sensu Kyoto protocol). Process studies address issues including upscaling of geoengineering, and how differing iron-enrichment strategies could stimulate wide-ranging biogeochemical outcomes. In summary, the availability of databases on both mesoscale iron-enrichment studies and the GEOTRACES survey, along with modelling, policy initiatives and legislation have positioned the iron-enrichment approach as a robust multifaceted test-bed to assess proposed research into climate intervention. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

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

    Science.gov (United States)

    Lagauzère, S.; Moreira, S.; Koschorreck, M.

    2011-02-01

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

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

    Science.gov (United States)

    Lagauzère, S.; Moreira, S.; Koschorreck, M.

    2010-10-01

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

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

    Directory of Open Access Journals (Sweden)

    S. Lagauzère

    2011-02-01

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

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

    Directory of Open Access Journals (Sweden)

    S. Lagauzère

    2010-10-01

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

  15. The ASIBIA sea-ice facility: First results from the Atmosphere-Sea-Ice-Biogeochemistry in the Arctic chamber

    Science.gov (United States)

    France, James L.; Thomas, Max

    2016-04-01

    Working in the natural ocean-ice-atmosphere system is very difficult, as conducting fieldwork on sea-ice presents many challenges ice including costs, safety, experimental controls and access. The new ASIBIA (Atmosphere-Sea-Ice-Biogeochemistry in the Arctic) coupled Ocean-Sea-Ice-(Snow)-Atmosphere chamber facility at the University of East Anglia, UK, we are aiming to perform controlled first-year sea-ice investigations in areas such as sea-ice physics, physicochemical and biogeochemical processes in sea-ice and quantification of the bi-directional flux of gases in various states of first-year sea-ice conditions. The facility is a medium sized chamber with programmable temperatures from -55°C to +30°C, allowing a full range of first year sea-ice growing conditions in both the Arctic and Antarctic to be simulated. The water depth can be up to 1 m (including up to 25 cm of sea-ice) and an optional 1 m tall Teflon film atmosphere on top of the sea-ice, thus creating a closed and coupled ocean-sea-ice-atmosphere mesocosm. Ice growth in the tank is well suited for studying first-year sea-ice physical properties, with in-situ ice-profile measurements of temperature, salinity, conductivity, pressure and spectral light transmission. Underwater and above ice cameras are installed to record the physical development of the sea-ice. Here, we present the data from the first suites of experiments in the ASIBIA chamber focussing on sea-ice physics and give a brief description of the capabilities of the facility going forward. The ASIBIA chamber was funded as part of an ERC consolidator grant to the late Prof. Roland von Glasow and we hope this work and further development of the facility will act as a lasting legacy.

  16. The relationship between sea ice bacterial community structure and biogeochemistry: A synthesis of current knowledge and known unknowns

    Directory of Open Access Journals (Sweden)

    Jeff S. Bowman

    2015-10-01

    Full Text Available Abstract Sea ice plays an important role in high latitude biogeochemical cycles, ecosystems, and climate. A complete understanding of how sea ice biogeochemistry contributes to these processes must take into account the metabolic functions of the sea ice bacterial community. While the roles of sea ice bacteria in the carbon cycle and sea ice microbial loop are evidenced by high rates of bacterial production (BP, their metabolic diversity extends far beyond heterotrophy, and their functionality encompasses much more than carbon turnover. Work over the last three decades has identified an active role for sea ice bacteria in phosphate and nitrogen cycling, mutualistic partnerships with ice algae, and even prokaryotic carbon fixation. To better understand the role of sea ice bacteria in the carbon cycle the existing sea ice BP and primary production data were synthesized. BP in sea ice was poorly correlated with primary production, but had a strong, variable relationship with chlorophyll a, with a positive correlation below 50 mg chlorophyll a m-3 and a negative correlation above this value. These results concur with previous work suggesting that BP can be inhibited by grazing or the production of bacteriostatic compounds. To extend existing observations and predictions of other community functions a metabolic inference technique was used on the available 16S rRNA gene data. This analysis provided taxonomic support for some observed metabolic processes, as well as underexplored processes such as sulfur oxidation and nitrogen fixation. The decreasing spatial and temporal extent of sea ice, and altered timing of ice formation and melt, are likely to impact the structure and function of sea ice bacterial communities. An adequate modeling framework and studies that can resolve the functional dynamics of the sea ice bacterial community, such as community gene expression studies, are urgently needed to predict future change.

  17. Final Report - Phase II - Biogeochemistry of Uranium Under Reducing and Re-oxidizing Conditions: An Integrated Laboratory and Field Study

    Energy Technology Data Exchange (ETDEWEB)

    Peyton, Brent; Sani, Rajesh

    2006-09-28

    Our understanding of subsurface microbiology is hindered by the inaccessibility of this environment, particularly when the hydrogeologic medium is contaminated with toxic substances. Past research in our labs indicated that the composition of the growth medium (e.g., bicarbonate complexation of U(VI)) and the underlying mineral phase (e.g., hematite) significantly affects the rate and extent of U(VI) reduction and immobilization through a variety of effects. Our research was aimed at elucidating those effects to a much greater extent, while exploring the potential for U(IV) reoxidation and subsequent re-mobilization, which also appears to depend on the mineral phases present in the system. The project reported on here was an extension ($20,575) of the prior (much larger) project. This report is focused only on the work completed during the extension period. Further information on the larger impacts of our research, including 28 publications, can be found in the final report for the following projects: 1) Biogeochemistry of Uranium Under Reducing and Re-oxidizing Conditions: An Integrated Laboratory and Field Study Grant # DE-FG03-01ER63270, and 2) Acceptable Endpoints for Metals and Radionuclides: Quantifying the Stability of Uranium and Lead Immobilized Under Sulfate Reducing Conditions Grant # DE-FG03-98ER62630/A001 In this Phase II project, the toxic effects of uranium(VI) were studied using Desulfovibrio desulfuricans G20 in a medium containing bicarbonate or 1, 4-piperazinediethane sulfonic acid disodium salt monohydrate (PIPES) buffer (each at 30 mM, pH 7). The toxicity of uranium(VI) was dependent on the medium buffer and was observed in terms of longer lag times and in some cases, no measurable growth. The minimum inhibiting concentration (MIC) was 140 M U(VI) in PIPES buffered medium. This is 36 times lower than previously reported for D. desulfuricans. These results suggest that U(VI) toxicity and the detoxification mechanisms of G20 depend greatly on the

  18. First Results from the ASIBIA (Arctic Sea-Ice, snow, Biogeochemistry and Impacts on the Atmosphere) Sea-Ice Chamber

    Science.gov (United States)

    Frey, M. M.; France, J.; von Glasow, R.; Thomas, M.

    2015-12-01

    The ocean-ice-atmosphere system is very complex, and there are numerous challenges with conducting fieldwork on sea-ice including costs, safety, experimental controls and access. By creating a new coupled Ocean-Sea-Ice-(Snow)-Atmosphere facility at the University of East Anglia, UK, we are able to perform controlled investigations in areas such as sea-ice physics, physicochemical and biogeochemical processes in sea-ice, and to quantify the bi-directional flux of gases in established, freezing and melting sea-ice. The environmental chamber is capable of controlled programmable temperatures from -55°C to +30°C, allowing a full range of first year sea-ice growing conditions in both the Arctic and Antarctic to be simulated. The sea-ice tank within the chamber measures 2.4 m x 1.4 m x 1 m water depth, with an identically sized Teflon film atmosphere on top of the tank. The tank and atmosphere forms a coupled, isolated mesocosm. Above the atmosphere is a light bank with dimmable solar simulation LEDs, and UVA and UVB broadband fluorescent battens, providing light for a range of experiments such as under ice biogeochemistry and photochemistry. Ice growth in the tank will be ideally suited for studying first-year sea-ice physical properties, with in-situ ice-profile measurements of temperature, salinity, conductivity, pressure and spectral light transmission. Under water and above ice cameras are installed to observe the physical development of the sea-ice. The ASIBIA facility is also well equipped for gas exchange and diffusion studies through sea-ice with a suite of climate relevant gas measuring instruments (CH4, CO2, O3, NOx, NOy permanently installed, further instruments available) able to measure either directly in the atmospheric component, or via a membrane for water side dissolved gases. Here, we present the first results from the ASIBIA sea-ice chamber, focussing on the physical development of first-year sea-ice and show the future plans for the facility over

  19. Using reactive transport codes to provide mechanistic biogeochemistry representations in global land surface models: CLM-PFLOTRAN 1.0

    Directory of Open Access Journals (Sweden)

    G. Tang

    2015-12-01

    Full Text Available We explore coupling to a configurable subsurface reactive transport code as a flexible and extensible approach to biogeochemistry in land surface models; our goal is to facilitate testing of alternative models and incorporation of new understanding. A reaction network with the CLM-CN decomposition, nitrification, denitrification, and plant uptake is used as an example. We implement the reactions in the open-source PFLOTRAN code, coupled with the Community Land Model (CLM, and test at Arctic, temperate, and tropical sites. To make the reaction network designed for use in explicit time stepping in CLM compatible with the implicit time stepping used in PFLOTRAN, the Monod substrate rate-limiting function with a residual concentration is used to represent the limitation of nitrogen availability on plant uptake and immobilization. To achieve accurate, efficient, and robust numerical solutions, care needs to be taken to use scaling, clipping, or log transformation to avoid negative concentrations during the Newton iterations. With a tight relative update tolerance to avoid false convergence, an accurate solution can be achieved with about 50 % more computing time than CLM in point mode site simulations using either the scaling or clipping methods. The log transformation method takes 60–100 % more computing time than CLM. The computing time increases slightly for clipping and scaling; it increases substantially for log transformation for half saturation decrease from 10−3 to 10−9 mol m−3, which normally results in decreasing nitrogen concentrations. The frequent occurrence of very low concentrations (e.g. below nanomolar can increase the computing time for clipping or scaling by about 20 %; computing time can be doubled for log transformation. Caution needs to be taken in choosing the appropriate scaling factor because a small value caused by a negative update to a small concentration may diminish the update and result in false convergence even

  20. On the role of mesoscale eddies for the biological productivity and biogeochemistry in the eastern tropical Pacific Ocean off Peru

    Directory of Open Access Journals (Sweden)

    L. Stramma

    2013-06-01

    Full Text Available Mesoscale eddies seem to play an important role for both the hydrography and biogeochemistry of the eastern tropical Pacific Ocean (ETSP off Peru. However, detailed surveys of these eddies are not available, which has so far hampered an in depth understanding of their implications for nutrient distribution and biological productivity. In this study three eddies along a section at 16°45' S have been surveyed intensively during R/V Meteor cruise M90 in November 2012. A coastal mode water eddy, an open ocean mode water eddy and an open ocean cyclonic eddy have been identified and sampled in order to determine both their hydrographic properties and their influence on the biogeochemical setting of the ETSP. In the thermocline the temperature of the coastal anticyclonic eddy was up to 2 °C warmer, 0.2 more saline and the swirl velocity was up to 35 cm s–1. The observed temperature and salinity anomalies, as well as swirl velocities of both types of eddies were about twice as large as had been described for the mean eddies in the ETSP and the observed heat and salt anomalies (AHA, ASA show a much larger variability than the mean AHA and ASA. We found that the eddies contributed significantly to productivity by maintaining pronounced subsurface maxima of chlorophyll. Based on a comparison of the coastal (young mode water eddy and the open ocean (old mode water eddy we conclude that the aging of eddies when they detach from the coast and move westward to the open ocean considerably influences the eddies' properties: chlorophyll maxima are weaker and nutrients are subducted. The coastal mode water eddy was found to be a hotspot of nitrogen loss in the OMZ, whereas, the open ocean cyclonic eddy was of negligible importance for nitrogen loss. Our results show that the important role the eddies play in the ETSP can only be fully deciphered and understood through dedicated high spatial and temporal resolution oceanographic/biogeochemical surveys.

  1. Overview of the US JGOFS Bermuda Atlantic Time-series Study (BATS): a decade-scale look at ocean biology and biogeochemistry

    Science.gov (United States)

    Steinberg, Deborah K.; Carlson, Craig A.; Bates, Nicholas R.; Johnson, Rodney J.; Michaels, Anthony F.; Knap, Anthony H.

    The Bermuda Atlantic Time-series Study (BATS) commenced monthly sampling in October 1988 as part of the US Joint Global Ocean Flux Study (JGOFS) program. The goals of the US JGOFS time-series research are to better understand the basic processes that control ocean biogeochemistry on seasonal to decadal time-scales, determine the role of the oceans in the global carbon budget, and ultimately improve our ability to predict the effects of climate change on ecosystems. The BATS program samples the ocean on a biweekly to monthly basis, a strategy that resolves major seasonal patterns and interannual variability. The core cruises last 4-5 d during which hydrography, nutrients, particle flux, pigments and primary production, bacterioplankton abundance and production, and often complementary ancillary measurements are made. This overview focuses on patterns in ocean biology and biogeochemistry over a decade at the BATS site, concentrating on seasonal and interannual changes in community structure, and the physical forcing and other factors controlling the temporal dynamics. Significant seasonal and interannual variability in phytoplankton and bacterioplankton production, biomass, and community structure exists at BATS. No strong relationship exists between primary production and particle flux during the 10 yr record, with the relationship slightly improved by applying an artificial lag of 1 week between production and flux. The prokaryotic picoplankton regularly dominate the phytoplankton community; diatom blooms are rare but occur periodically in the BATS time series. The increase in Chl a concentrations during bloom periods is due to increases by most of the taxa present, rather than by any single group, and there is seasonal succession of phytoplankton. The bacterioplankton often dominate the living biomass, indicating the potential to consume large amounts of carbon and play a major ecological role within the microbial food web. Bacterial biomass, production, and

  2. Biogeochemistry: Early phosphorus redigested

    Science.gov (United States)

    Poulton, Simon W.

    2017-02-01

    Atmospheric oxygen was maintained at low levels throughout huge swathes of Earth's early history. Estimates of phosphorus availability through time suggest that scavenging from anoxic, iron-rich oceans stabilized this low-oxygen world.

  3. Forensic Stable Isotope Biogeochemistry

    Science.gov (United States)

    Cerling, Thure E.; Barnette, Janet E.; Bowen, Gabriel J.; Chesson, Lesley A.; Ehleringer, James R.; Remien, Christopher H.; Shea, Patrick; Tipple, Brett J.; West, Jason B.

    2016-06-01

    Stable isotopes are being used for forensic science studies, with applications to both natural and manufactured products. In this review we discuss how scientific evidence can be used in the legal context and where the scientific progress of hypothesis revisions can be in tension with the legal expectations of widely used methods for measurements. Although this review is written in the context of US law, many of the considerations of scientific reproducibility and acceptance of relevant scientific data span other legal systems that might apply different legal principles and therefore reach different conclusions. Stable isotopes are used in legal situations for comparing samples for authenticity or evidentiary considerations, in understanding trade patterns of illegal materials, and in understanding the origins of unknown decedents. Isotope evidence is particularly useful when considered in the broad framework of physiochemical processes and in recognizing regional to global patterns found in many materials, including foods and food products, drugs, and humans. Stable isotopes considered in the larger spatial context add an important dimension to forensic science.

  4. Subsurface Biogeochemistry of Actinides

    Energy Technology Data Exchange (ETDEWEB)

    Kersting, Annie B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Univ. Relations and Science Education; Zavarin, Mavrik [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Glenn T. Seaborg Inst.

    2016-06-29

    A major scientific challenge in environmental sciences is to identify the dominant processes controlling actinide transport in the environment. It is estimated that currently, over 2200 metric tons of plutonium (Pu) have been deposited in the subsurface worldwide, a number that increases yearly with additional spent nuclear fuel (Ewing et al., 2010). Plutonium has been shown to migrate on the scale of kilometers, giving way to a critical concern that the fundamental biogeochemical processes that control its behavior in the subsurface are not well understood (Kersting et al., 1999; Novikov et al., 2006; Santschi et al., 2002). Neptunium (Np) is less prevalent in the environment; however, it is predicted to be a significant long-term dose contributor in high-level nuclear waste. Our focus on Np chemistry in this Science Plan is intended to help formulate a better understanding of Pu redox transformations in the environment and clarify the differences between the two long-lived actinides. The research approach of our Science Plan combines (1) Fundamental Mechanistic Studies that identify and quantify biogeochemical processes that control actinide behavior in solution and on solids, (2) Field Integration Studies that investigate the transport characteristics of Pu and test our conceptual understanding of actinide transport, and (3) Actinide Research Capabilities that allow us to achieve the objectives of this Scientific Focus Area (SFA and provide new opportunities for advancing actinide environmental chemistry. These three Research Thrusts form the basis of our SFA Science Program (Figure 1).

  5. Biogeochemistry: Oxygen burrowed away

    NARCIS (Netherlands)

    Meysman, F.J.R.

    2014-01-01

    Multicellular animals probably evolved at the seafloor after a rise in oceanic oxygen levels. Biogeochemical model simulations suggest that as these animals started to rework the seafloor, they triggered a negative feedback that reduced global oxygen.

  6. Toward a multivariate reanalysis of the North Atlantic Ocean biogeochemistry during 1998-2006 based on the assimilation of SeaWiFS chlorophyll data

    Science.gov (United States)

    Fontana, C.; Brasseur, P.; Brankart, J.-M.

    2013-01-01

    Today, the routine assimilation of satellite data into operational models of ocean circulation is mature enough to enable the production of global reanalyses describing the ocean circulation variability during the past decades. The expansion of the "reanalysis" concept from ocean physics to biogeochemistry is a timely challenge that motivates the present study. The objective of this paper is to investigate the potential benefits of assimilating satellite-estimated chlorophyll data into a basin-scale three-dimensional coupled physical-biogeochemical model of the North Atlantic. The aim is on the one hand to improve forecasts of ocean biogeochemical properties and on the other hand to define a methodology for producing data-driven climatologies based on coupled physical-biogeochemical modeling. A simplified variant of the Kalman filter is used to assimilate ocean color data during a 9-year period. In this frame, two experiments are carried out, with and without anamorphic transformations of the state vector variables. Data assimilation efficiency is assessed with respect to the assimilated data set, nitrate of the World Ocean Atlas database and a derived climatology. Along the simulation period, the non-linear assimilation scheme clearly improves the surface analysis and forecast chlorophyll concentrations, especially in the North Atlantic bloom region. Nitrate concentration forecasts are also improved thanks to the assimilation of ocean color data while this improvement is limited to the upper layer of the water column, in agreement with recent related literature. This feature is explained by the weak correlation taken into account by the assimilation between surface phytoplankton and nitrate concentrations deeper than 50 meters. The assessment of the non-linear assimilation experiments indicates that the proposed methodology provides the skeleton of an assimilative system suitable for reanalyzing the ocean biogeochemistry based on ocean color data.

  7. The ecological module of BOATS-1.0: a bioenergetically constrained model of marine upper trophic levels suitable for studies of fisheries and ocean biogeochemistry

    Science.gov (United States)

    Carozza, David Anthony; Bianchi, Daniele; Galbraith, Eric Douglas

    2016-04-01

    Environmental change and the exploitation of marine resources have had profound impacts on marine communities, with potential implications for ocean biogeochemistry and food security. In order to study such global-scale problems, it is helpful to have computationally efficient numerical models that predict the first-order features of fish biomass production as a function of the environment, based on empirical and mechanistic understandings of marine ecosystems. Here we describe the ecological module of the BiOeconomic mArine Trophic Size-spectrum (BOATS) model, which takes an Earth-system approach to modelling fish biomass at the global scale. The ecological model is designed to be used on an Earth-system model grid, and determines size spectra of fish biomass by explicitly resolving life history as a function of local temperature and net primary production. Biomass production is limited by the availability of photosynthetic energy to upper trophic levels, following empirical trophic efficiency scalings, and by well-established empirical temperature-dependent growth rates. Natural mortality is calculated using an empirical size-based relationship, while reproduction and recruitment depend on both the food availability to larvae from net primary production and the production of eggs by mature adult fish. We describe predicted biomass spectra and compare them to observations, and conduct a sensitivity study to determine how they change as a function of net primary production and temperature. The model relies on a limited number of parameters compared to similar modelling efforts, while retaining reasonably realistic representations of biological and ecological processes, and is computationally efficient, allowing extensive parameter-space analyses even when implemented globally. As such, it enables the exploration of the linkages between ocean biogeochemistry, climate, and upper trophic levels at the global scale, as well as a representation of fish biomass for

  8. The ecological module of BOATS-1.0: a bioenergetically-constrained model of marine upper trophic levels suitable for studies of fisheries and ocean biogeochemistry

    Directory of Open Access Journals (Sweden)

    D. A. Carozza

    2015-12-01

    Full Text Available Environmental change and the exploitation of marine resources have had profound impacts on marine communities, with potential implications for ocean biogeochemistry and food security. In order to study such global-scale problems, it is helpful to have computationally efficient numerical models that predict the first-order features of fish biomass production as a function of the environment, based on empirical and mechanistic understandings of marine ecosystems. Here we describe the ecological module of the BiOeconomic mArine Trophic Size-spectrum (BOATS model, which takes an Earth-system approach to modeling fish biomass at the global scale. The ecological model is designed to be used on an Earth System model grid, and determines size spectra of fish biomass by explicitly resolving life history as a function of local temperature and net primary production. Biomass production is limited by the availability of photosynthetic energy to upper trophic levels, following empirical trophic efficiency scalings, and by well-established empirical temperature-dependent growth rates. Natural mortality is calculated using an empirical size-based relationship, while reproduction and recruitment depend on both the food availability to larvae from net primary production and the production of eggs by mature adult fish. We describe predicted biomass spectra and compare them to observations, and conduct a sensitivity study to determine how the change as a function of net primary production and temperature. The model relies on a limited number of parameters compared to similar modeling efforts, while retaining realistic representations of biological and ecological processes, and is computationally efficient, allowing extensive parameter-space analyses even when implemented globally. As such, it enables the exploration of the linkages between ocean biogeochemistry, climate, and upper trophic levels at the global scale, as well as a representation of fish biomass for

  9. Biogeochemistry of Deltaic Floodplains: An overview of concepts and issues associated with the nutrient dynamics and stoichiometry of Wax Lake Delta, Louisiana

    Science.gov (United States)

    Twilley, R.; Henry, K. M.; Bevington, A.; Castaneda, E.; Branoff, B.; Rivera-Monroy, V.

    2013-12-01

    Nutrient biogeochemistry associated with the early stages of soil development in deltaic floodplains has not been well defined. Such a model should follow classic patterns of soil nutrient pools described for alluvial ecosystems that are dominated by mineral matter high in phosphorus and low in carbon and nitrogen. Shifts in the nutrient dynamics and stoichiometry of these newly emerged ecosystems should reflect complex feedback mechanisms during classic delta cycle. These ecogeomorphic processes of soil development are modified in most coastal regions by the anthropogenically enriched high-nitrate conditions due to agricultural fertilization in upstream watersheds. We will use the emerging Wax Lake delta (WLD) chronosequence as conceptual models of nutrient dynamics and stoichiometry of deltaic floodplain ecosystems. Throughout the 35-year chronosequence, soil nitrogen and organic matter content significantly increased by an order of magnitude, while phosphorus remained relatively constant, shifting the N:P ratio from nitrogen limitation (soils switched from net denitrification to net nitrogen fixation (-74.5 μmol N m-2 h-1). As soils in the WLD aged, the subsequent increase in organic matter stimulated net N2, oxygen, nitrate, and nitrite fluxes producing greater fluxes in more mature soils. These newly emerged landscapes are also potential sites of nitrate reduction along continental margins, protecting coastal waters from enriched watershed runoff of nitrate. However, recent evidence suggests wetlands are actually susceptible to nutrient enrichment additions due to ';biomass allocation strategies' that reduce soil strength and geomorphic development of coastal landscapes. Mineral rich delta floodplains do not show any of these vulnerabilities (during growth phase) compared to organic rich soils of deltaic coast (during maintenance phase). However, nitrate reduction efficiencies depend on soil organic matter accumulation and residence time of surface water flow

  10. The ecological module of BOATS-1.0: a bioenergetically-constrained model of marine upper trophic levels suitable for studies of fisheries and ocean biogeochemistry

    Science.gov (United States)

    Carozza, D. A.; Bianchi, D.; Galbraith, E. D.

    2015-12-01

    Environmental change and the exploitation of marine resources have had profound impacts on marine communities, with potential implications for ocean biogeochemistry and food security. In order to study such global-scale problems, it is helpful to have computationally efficient numerical models that predict the first-order features of fish biomass production as a function of the environment, based on empirical and mechanistic understandings of marine ecosystems. Here we describe the ecological module of the BiOeconomic mArine Trophic Size-spectrum (BOATS) model, which takes an Earth-system approach to modeling fish biomass at the global scale. The ecological model is designed to be used on an Earth System model grid, and determines size spectra of fish biomass by explicitly resolving life history as a function of local temperature and net primary production. Biomass production is limited by the availability of photosynthetic energy to upper trophic levels, following empirical trophic efficiency scalings, and by well-established empirical temperature-dependent growth rates. Natural mortality is calculated using an empirical size-based relationship, while reproduction and recruitment depend on both the food availability to larvae from net primary production and the production of eggs by mature adult fish. We describe predicted biomass spectra and compare them to observations, and conduct a sensitivity study to determine how the change as a function of net primary production and temperature. The model relies on a limited number of parameters compared to similar modeling efforts, while retaining realistic representations of biological and ecological processes, and is computationally efficient, allowing extensive parameter-space analyses even when implemented globally. As such, it enables the exploration of the linkages between ocean biogeochemistry, climate, and upper trophic levels at the global scale, as well as a representation of fish biomass for idealized studies

  11. Evaluation of an operational ocean model configuration at 1/12° spatial resolution for the Indonesian seas (NEMO2.3/INDO12) - Part 2: Biogeochemistry

    Science.gov (United States)

    Gutknecht, Elodie; Reffray, Guillaume; Gehlen, Marion; Triyulianti, Iis; Berlianty, Dessy; Gaspar, Philippe

    2016-04-01

    In the framework of the INDESO (Infrastructure Development of Space Oceanography) project, an operational ocean forecasting system was developed to monitor the state of the Indonesian seas in terms of circulation, biogeochemistry and fisheries. This forecasting system combines a suite of numerical models connecting physical and biogeochemical variables to population dynamics of large marine predators (tunas). The physical-biogeochemical coupled component (the INDO12BIO configuration) covers a large region extending from the western Pacific Ocean to the eastern Indian Ocean at 1/12° horizontal resolution. The NEMO-OPA (Nucleus for European Model of the Ocean) physical ocean model and the PISCES (Pelagic Interactions Scheme for Carbon and Ecosystem Studies) biogeochemical model are running simultaneously ("online" coupling), at the same resolution. The operational global ocean forecasting system (1/4°) operated by Mercator Océan provides the physical forcing, while climatological open boundary conditions are prescribed for the biogeochemistry. This paper describes the skill assessment of the INDO12BIO configuration. Model skill is assessed by evaluating a reference hindcast simulation covering the last 8 years (2007-2014). Model results are compared to satellite, climatological and in situ observations. Diagnostics are performed on nutrients, oxygen, chlorophyll a, net primary production and mesozooplankton. The model reproduces large-scale distributions of nutrients, oxygen, chlorophyll a, net primary production and mesozooplankton biomasses. Modelled vertical distributions of nutrients and oxygen are comparable to in situ data sets although gradients are slightly smoothed. The model simulates realistic biogeochemical characteristics of North Pacific tropical waters entering in the archipelago. Hydrodynamic transformation of water masses across the Indonesian archipelago allows for conserving nitrate and oxygen vertical distribution close to observations, in the

  12. Effects of long-term flooding on biogeochemistry and vegetation development in floodplains – a mesocosm experiment to study interacting effects of land use and water quality

    Directory of Open Access Journals (Sweden)

    A. M. Banach

    2009-03-01

    Full Text Available The frequent occurrence of summer floods in Eastern Europe, possibly related to climate change, urges the need to understand the consequences of combined water storage and nature rehabilitation as an alternative safety measure instead of raising and reinforcing dykes, for floodplain biogeochemistry and vegetation development. We used a mesocosm design to investigate the possibilities for the creation of permanently flooded wetlands along rivers, in relation to water quality (nitrate, sulphate and land use (fertilization. Flooding resulted in severe eutrophication of both sediment pore water and surface water, particularly for more fertilized soil and sulphate pollution. Vegetation development was mainly determined by soil quality, resulting in a strong decline of most species from the highly fertilized location, especially in combination with higher nitrate and sulphate concentrations. Soils from the less fertilized location showed, in contrast, luxurious growth of target Carex species regardless water quality. The observed interacting effects of water quality and agricultural use are important in assessing the consequences of planned measures for ecosystem functioning (including peat formation and biodiversity in river floodplains.

  13. Effects of long-term flooding on biogeochemistry and vegetation development in floodplains; a mesocosm experiment to study interacting effects of land use and water quality

    Directory of Open Access Journals (Sweden)

    R. C. J. H. Peters

    2009-07-01

    Full Text Available Raising safety levees and reinforcing dykes is not a sufficient and sustainable solution to the intense winter and summer floods occurring with increasing frequency in Eastern Europe. An alternative, creating permanently flooded floodplain wetlands, requires improved understanding of ecological consequences. A 9 month mesocosm study (starting in January, under natural light and temperature conditions, was initiated to understand the role of previous land use (fertility intensity and flooding water quality on soil biogeochemistry and vegetation development. Flooding resulted in severe eutrophication of both sediment pore water and surface water, particularly for more fertilized soil and sulphate pollution. Vegetation development was mainly determined by soil quality, resulting in a strong decline of most species from the highly fertilized location, especially in combination with higher nitrate and sulphate concentrations. Soils from the less fertilized location showed, in contrast, luxurious growth of target Carex species regardless water quality. The observed interacting effects of water quality and agricultural use are important in assessing the consequences of planned measures for ecosystem functioning and biodiversity in river floodplains.

  14. Effects of long-term flooding on biogeochemistry and vegetation development in floodplains - a mesocosm experiment to study interacting effects of land use and water quality

    Science.gov (United States)

    Banach, A. M.; Banach, K.; Peters, R. C. J. H.; Jansen, R. H. M.; Visser, E. J. W.; Stepniewska, Z.; Roelofs, J. G. M.; Lamers, L. P. M.

    2009-03-01

    The frequent occurrence of summer floods in Eastern Europe, possibly related to climate change, urges the need to understand the consequences of combined water storage and nature rehabilitation as an alternative safety measure instead of raising and reinforcing dykes, for floodplain biogeochemistry and vegetation development. We used a mesocosm design to investigate the possibilities for the creation of permanently flooded wetlands along rivers, in relation to water quality (nitrate, sulphate) and land use (fertilization). Flooding resulted in severe eutrophication of both sediment pore water and surface water, particularly for more fertilized soil and sulphate pollution. Vegetation development was mainly determined by soil quality, resulting in a strong decline of most species from the highly fertilized location, especially in combination with higher nitrate and sulphate concentrations. Soils from the less fertilized location showed, in contrast, luxurious growth of target Carex species regardless water quality. The observed interacting effects of water quality and agricultural use are important in assessing the consequences of planned measures for ecosystem functioning (including peat formation) and biodiversity in river floodplains.

  15. Effects of long-term flooding on biogeochemistry and vegetation development in floodplains; a mesocosm experiment to study interacting effects of land use and water quality

    Science.gov (United States)

    Banach, A. M.; Banach, K.; Peters, R. C. J. H.; Jansen, R. H. M.; Visser, E. J. W.; Stepniewska, Z.; Roelofs, J. G. M.; Lamers, L. P. M.

    2009-07-01

    Raising safety levees and reinforcing dykes is not a sufficient and sustainable solution to the intense winter and summer floods occurring with increasing frequency in Eastern Europe. An alternative, creating permanently flooded floodplain wetlands, requires improved understanding of ecological consequences. A 9 month mesocosm study (starting in January), under natural light and temperature conditions, was initiated to understand the role of previous land use (fertility intensity) and flooding water quality on soil biogeochemistry and vegetation development. Flooding resulted in severe eutrophication of both sediment pore water and surface water, particularly for more fertilized soil and sulphate pollution. Vegetation development was mainly determined by soil quality, resulting in a strong decline of most species from the highly fertilized location, especially in combination with higher nitrate and sulphate concentrations. Soils from the less fertilized location showed, in contrast, luxurious growth of target Carex species regardless water quality. The observed interacting effects of water quality and agricultural use are important in assessing the consequences of planned measures for ecosystem functioning and biodiversity in river floodplains.

  16. Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico, St. Petersburg, FL, May 6-8, 2008

    Science.gov (United States)

    Robbins, L.L.; Coble, P.G.; Clayton, T.D.; Cai, W.J.

    2009-01-01

    Despite their relatively small surface area, ocean margins may have a significant impact on global biogeochemical cycles and, potentially, the global air-sea fluxes of carbon dioxide. Margins are characterized by intense geochemical and biological processing of carbon and other elements and exchange large amounts of matter and energy with the open ocean. The area-specific rates of productivity, biogeochemical cycling, and organic/inorganic matter sequestration are high in coastal margins, with as much as half of the global integrated new production occurring over the continental shelves and slopes (Walsh, 1991; Doney and Hood, 2002; Jahnke, in press). However, the current lack of knowledge and understanding of biogeochemical processes occurring at the ocean margins has left them largely ignored in most of the previous global assessments of the oceanic carbon cycle (Doney and Hood, 2002). A major source of North American and global uncertainty is the Gulf of Mexico, a large semi-enclosed subtropical basin bordered by the United States, Mexico, and Cuba. Like many of the marginal oceans worldwide, the Gulf of Mexico remains largely unsampled and poorly characterized in terms of its air-sea exchange of carbon dioxide and other carbon fluxes. In May 2008, the Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico was held in St. Petersburg, FL, to address the information gaps of carbon fluxes associated with the Gulf of Mexico and to offer recommendations to guide future research. The meeting was attended by over 90 participants from over 50 U.S. and Mexican institutions and agencies. The Ocean Carbon and Biogeochemistry program (OCB; http://www.us-ocb.org/) sponsored this workshop with support from the National Science Foundation, the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, the U.S. Geological Survey, and the University of South Florida. The goal of

  17. Advance in Polar Subglacial Biogeochemistry Process%极地冰下生物地球化学过程研究进展

    Institute of Scientific and Technical Information of China (English)

    马红梅; 孙波; 姜苏; 安春雷; 史贵涛; 李院生

    2012-01-01

    The present research shows that life exists in subglacial environment.Biogeochemistry process,by means of its unique view,which combines the biology with the geochemistry,provides a new way to explain the existence of microbe in subglacial environment and their impact on the global climate change.At present,the study of the subglacial life mostly focuses on the temperature glaciers and polythermal glaciers,whereas on cold-based glaciers,the studies of the origination of life,the living conditions,the energy transform,the distribution characteristics,as well as the characterization of microbial community,are all at the preparatory stage.Based on the elucidation of the development of chemical weathering mechanism,this paper reviewc the latest progress of research in the application of biogeochemistry to explore the subglacial environment.Additionally,Future studies regarding the microbial survival in subglacial environment,the release of greenhouse,paleoclimate mutation exploration,and life exploration in other planet are discussed and recommended.%已有的研究结果表明:极地冰下存在生命活动的证据。生物地球化学过程以其独特的视角,从生物学和地球化学学科交叉的角度,对于诠释冰下环境微生物生存及其对全球气候的影响提供了一条新途径。目前对于冰下生命的研究多集中在温型冰川和多温型冰川,关于冷型冰川冰下环境的生物起源、生存条件、能源转化方式和生物体的空间分布特征及种属关系等研究均还处在起步阶段。在简要阐述冰下化学风化机理发展历程的基础上,对近年应用生物地球化学过程研究极地冰下环境的研究成果进行总结和分析。此外,针对该领域目前研究上的空白和热点,分别对利用生物地球化学过程研究冰下环境微生物生存和繁衍,冰下温室气体释放,重大古气候事件探索及星际生命探索等科学命题进行展望。

  18. A new model for the global biogeochemical cycle of carbonyl sulfide - Part 1: Assessment of direct marine emissions with an oceanic general circulation and biogeochemistry model

    Science.gov (United States)

    Launois, T.; Belviso, S.; Bopp, L.; Fichot, C. G.; Peylin, P.

    2014-08-01

    The global budget of tropospheric carbonyl sulfide (OCS) is believed to be at equilibrium because background air concentrations have remained roughly stable over at least the last decade. Since the uptakes of OCS by leaves (associated to photosynthesis) and soils have been revised significantly upwards recently, an equilibrated budget can only be obtained with a compensatory source of OCS. It has been assumed that the missing source of OCS comes from the low latitude ocean, following the incident solar flux. The present work uses parameterizations of major production and removal processes of organic compounds in the NEMO-PISCES Ocean General Circulation and Biogeochemistry Model to assess the marine source of OCS. In addition, the OCS photo-production rates computed with the NEMO-PISCES model were evaluated independently using UV absorption coefficient of chromophoric dissolved organic matter (derived from satellite ocean color) and apparent quantum yields available in the literature. Our simulations show global direct marine emissions of COS in the range of 573-3997 Gg S yr-1, depending mostly on the quantification of the absorption rate of chromophoric dissolved organic matter. The high estimates on that range are unlikely, as they correspond to a formulation that most likely overestimate photo-production process. Low and medium (813 Gg S yr-1) estimates derived from the NEMO-PISCES model are however consistent spatially and temporally with the suggested missing source of Berry et al. (2013), allowing thus to close the global budget of OCS given the recent estimates of leaf and soil OCS uptakes.

  19. A new model for the global biogeochemical cycle of carbonyl sulfide – Part 1: Assessment of direct marine emissions with an oceanic general circulation and biogeochemistry model

    Directory of Open Access Journals (Sweden)

    T. Launois

    2014-08-01

    Full Text Available The global budget of tropospheric carbonyl sulfide (OCS is believed to be at equilibrium because background air concentrations have remained roughly stable over at least the last decade. Since the uptakes of OCS by leaves (associated to photosynthesis and soils have been revised significantly upwards recently, an equilibrated budget can only be obtained with a compensatory source of OCS. It has been assumed that the missing source of OCS comes from the low latitude ocean, following the incident solar flux. The present work uses parameterizations of major production and removal processes of organic compounds in the NEMO-PISCES Ocean General Circulation and Biogeochemistry Model to assess the marine source of OCS. In addition, the OCS photo-production rates computed with the NEMO-PISCES model were evaluated independently using UV absorption coefficient of chromophoric dissolved organic matter (derived from satellite ocean color and apparent quantum yields available in the literature. Our simulations show global direct marine emissions of COS in the range of 573–3997 Gg S yr−1, depending mostly on the quantification of the absorption rate of chromophoric dissolved organic matter. The high estimates on that range are unlikely, as they correspond to a formulation that most likely overestimate photo-production process. Low and medium (813 Gg S yr−1 estimates derived from the NEMO-PISCES model are however consistent spatially and temporally with the suggested missing source of Berry et al. (2013, allowing thus to close the global budget of OCS given the recent estimates of leaf and soil OCS uptakes.

  20. Reconstruction of the biogeochemistry and ecology of photoautotrophs based on the nitrogen and carbon isotopic compositions of vanadyl porphyrins from Miocene siliceous sediments

    Directory of Open Access Journals (Sweden)

    Y. Kashiyama

    2008-05-01

    Full Text Available We determined both the nitrogen and carbon isotopic compositions of various vanadyl alkylporphyrins isolated from siliceous marine sediments of the Onnagawa Formation (middle Miocene, northeastern Japan to investigate the biogeochemistry and ecology of photoautotrophs living in the paleo-ocean. The distinctive isotopic signals support the interpretations of previous works that the origin of 17-nor-deoxophylloerythroetioporphyrin (DPEP is chlorophylls-c1-3, whereas 8-nor-DPEP may have originated from chlorophylls-a2 or b2 or bacteriochlorophyll-a. Although DPEP and cycloheptanoDPEP are presumably derived from common precursory pigments, their isotopic compositions differed in the present study, suggesting that the latter represents a specific population within the photoautotrophic community. The average δ15N value for the entire photoautotrophic community is estimated to be –2 to +1‰ from the δ15N values of DPEP (–6.9 to –3.6‰; n=7, considering that the empirical isotopic relationships that the tetrapyrrole nuclei of chloropigments are depleted in 15N by ~4.8‰ and enriched in 13C by ~1.8‰ relative to the whole cells. This finding suggests that nitrogen utilized in the primary production was supplied mainly through N2-fixation by diazotrophic cyanobacteria. Based on the δ13C values of DPEP (–17.9 to –15.6‰; n=7, we estimated isotopic fractionation associated with photosynthetic carbon fixation to be 8–14‰. This range suggests the importance of β-carboxylation and/or active transport of the carbon substrate, indicating in turn the substantial contribution of diazotrophic cyanobacteria to primary production. Based on the δ15N values of 17-nor-DPEP (–7.4 to –2.4‰ n=7, the δ15N range of chlorophylls-c-producing algae was estimated to be –3

  1. How deep can surface signals be traced in the critical zone? Merging biodiversity with biogeochemistry research in a central German Muschelkalk landscape

    Science.gov (United States)

    Küsel, Kirsten; Totsche, Kai; Trumbore, Susan; Lehmann, Robert; Steinhäuser, Christine; Herrmann, Martina

    2016-04-01

    The Earth's Critical Zone (CZ) is a thin living layer connecting atmosphere and geosphere, including aquifers. Humans live in the CZ and benefit from the vital supporting services it provides. However, the CZ is increasingly impacted by human activities including land and resource use, pollution and climate change. Recent interest in uniting the many disciplines studying this complex domain has initiated an international network of research infrastructure platforms that allow access to the CZ in a range of geologic settings. In this paper a new such infrastructure platform associated with the Collaborative Research Center AquaDiva is described, that uniquely seeks to combine CZ research with detailed investigation of the functional biodiversity of the subsurface. Overall, AquaDiva aims to test hypotheses about how water connects surface conditions set by land cover and land management to the biota and biogeochemical functions in the subsurface. With long-term and continuous observations, hypotheses about how seasonal variations and extreme events at the surface impact subsurface processes, community structure and function, are tested. AquaDiva has established the Hainich Critical Zone Exploratory (CZE) in central Germany in an alkaline geological setting of German Triassic Muschelkalk formations. The Hainich CZE includes specialized monitoring wells to access the vadose zone and two main groundwater complexes in limestone and marlstone parent materials along a ~6 km transect spanning forest, pasture and agricultural land uses. Initial results demonstrate fundamental differences in the biota and biogeochemistry of the two aquifer complexes that trace back to the land uses in their respective recharge areas. They also show the importance of antecedent conditions on the impact of precipitation events on responses in terms of groundwater dynamics, chemistry and ecology. Thus we find signals of surface land use and events can be detected in the subsurface CZ. Future

  2. Modeled responses of terrestrial ecosystems to elevated atmospheric CO2: A comparison of simulations by the biogeochemistry models of the Vegetation/Ecosystem Modeling and Analysis Project (VEMAP)

    Science.gov (United States)

    Pan, Y.; Melillo, J.M.; McGuire, A.D.; Kicklighter, D.W.; Pitelka, L.F.; Hibbard, K.; Pierce, L.L.; Running, S.W.; Ojima, D.S.; Parton, W.J.; Schimel, D.S.; Borchers, J.; Neilson, R.; Fisher, H.H.; Kittel, T.G.F.; Rossenbloom, N.A.; Fox, S.; Haxeltine, A.; Prentice, I.C.; Sitch, S.; Janetos, A.; McKeown, R.; Nemani, R.; Painter, T.; Rizzo, B.; Smith, T.; Woodward, F.I.

    1998-01-01

    Although there is a great deal of information concerning responses to increases in atmospheric CO2 at the tissue and plant levels, there are substantially fewer studies that have investigated ecosystem-level responses in the context of integrated carbon, water, and nutrient cycles. Because our understanding of ecosystem responses to elevated CO2 is incomplete, modeling is a tool that can be used to investigate the role of plant and soil interactions in the response of terrestrial ecosystems to elevated CO2. In this study, we analyze the responses of net primary production (NPP) to doubled CO2 from 355 to 710 ppmv among three biogeochemistry models in the Vegetation/Ecosystem Modeling and Analysis Project (VEMAP): BIOME-BGC (BioGeochemical Cycles), Century, and the Terrestrial Ecosystem Model (TEM). For the conterminous United States, doubled atmospheric CO2 causes NPP to increase by 5% in Century, 8% in TEM, and 11% in BIOME-BGC. Multiple regression analyses between the NPP response to doubled CO2 and the mean annual temperature and annual precipitation of biomes or grid cells indicate that there are negative relationships between precipitation and the response of NPP to doubled CO2 for all three models. In contrast, there are different relationships between temperature and the response of NPP to doubled CO2 for the three models: there is a negative relationship in the responses of BIOME-BGC, no relationship in the responses of Century, and a positive relationship in the responses of TEM. In BIOME-BGC, the NPP response to doubled CO2 is controlled by the change in transpiration associated with reduced leaf conductance to water vapor. This change affects soil water, then leaf area development and, finally, NPP. In Century, the response of NPP to doubled CO2 is controlled by changes in decomposition rates associated with increased soil moisture that results from reduced evapotranspiration. This change affects nitrogen availability for plants, which influences NPP. In

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

    Science.gov (United States)

    Heuer, V.B.; Pohlman, J.W.; Torres, M.E.; Elvert, M.; Hinrichs, K.-U.

    2009-01-01

    . Further, the isotopic relationship suggests a relative increase in acetate flow to acetoclastic methanogenesis with depth although its contribution to total methanogenesis is probably small. Our study demonstrates how the stable carbon isotope biogeochemistry of acetate can be used to identify pathways of microbial carbon turnover in subsurface environments. Our observations also raise new questions regarding the factors controlling acetate turnover in marine sediments. ?? 2009 Elsevier Ltd.

  4. Space agriculture: the effect of micro- and hypo-gravity on soil hydraulics and biogeochemistry in a bioregenerative soil-based cropping unit

    Science.gov (United States)

    Maggi, F.; Pallud, C. E.

    2010-12-01

    Abstract Increasing interest has developed towards growing plants in soil-based cropping modules as a long-term bioregenerative life support system in space and planetary explorations. Contrary to hydroponics, zeoponics and aeroponics, soil-based cropping would offer an effective approach to sustain food and oxygen production, decompose organic wastes, sequester carbon dioxide, and filter water for the crew. The hydraulic and biogeochemical functioning are highly complex in soil-based systems but such systems provide a self-sustainable microcosm that potentially offers compactness, low energy demand, near-ambient reactor temperatures and pressure, reliability, forgiveness of operational errors or neglect, and a rich biodiversity of microorganisms, all features which are fundamental for the sustainability and reliability of long-term manned space missions. However, the hydraulics and biogeochemical functioning of soil systems exposed to gravities lower than the Earth’s are still unknown. Since gravity is crucial in driving water flow, hypogravity will affect nutrient and oxygen transport in the liquid and gaseous phases, and could lead to suffocation of microorganisms and roots, and emissions of toxic gases. A highly mechanistic model coupling soil hydraulics and nutrient biogeochemistry previously tested on soils on Earth (g = 9.806 m s-2) is used to highlight the effects of gravity on the functioning of cropping units on Mars (0.38g), the Moon (0.16g), and in the international space station (ISS, nearly 0g). For each scenario, we have compared the net leaching of water, the leaching of NH3, NH4+, NO2- and NO3- solutes, the emissions of NH3, CO2, N2O, NO and N2 gases, the concentrations profiles of O2, CO2 and dissolved organic carbon (DOC) in soil, the pH, and the dynamics of various microbial functional groups within the root zone against the same control variables in the soil under terrestrial gravity. The tested hypo- and micro-gravity resulted in 90

  5. Biogeochemistry of landfill leachate plumes

    DEFF Research Database (Denmark)

    Christensen, Thomas Højlund; Kjeldsen, Peter; Bjerg, Poul Løgstrup

    2001-01-01

    is on dissolved organic matter, xenobiotic organic compounds, inorganic macrocomponents as anions and cations, and heavy metals. Laboratory as well as field investigations are included. This review is an up-date of an earlier comprehensive review. The review shows that most leachate contamination plumes...... the behavior of the contaminants in the plume as the leachate migrates away from the landfill. Diverse microbial communities have been identified in leachate plumes and are believed to be responsible for the redox processes. Dissolved organic C in the leachate, although it appears to be only slowly degradable...

  6. Modern biogeochemistry environmental risk assessment

    CERN Document Server

    Bashkin, Vladimir N

    2006-01-01

    Most books deal mainly with various technical aspects of ERA description and calculationsAims at generalizing the modern ideas of both biogeochemical and environmental risk assessment during recent yearsAims at supplementing the existing books by providing a modern understanding of mechanisms that are responsible for the ecological risk for human beings and ecosystem

  7. Marine Mo biogeochemistry in the context of dynamically euxinic mid-depth waters: A case study of the lower Cambrian Niutitang shales, South China

    Science.gov (United States)

    Cheng, Meng; Li, Chao; Zhou, Lian; Algeo, Thomas J.; Zhang, Feifei; Romaniello, Stephen; Jin, Cheng-Sheng; Lei, Li-Dan; Feng, Lian-Jun; Jiang, Shao-Yong

    2016-06-01

    mid-depth euxinic waters in nearshore areas of the Nanhua Basin due to relatively high availability of fluvial Fe-Mn oxides and their subsequent reduction below the chemocline. Within this redox framework, large sedimentary δ98Mo variations observed for the Niutitang shales can be explained through the combined effects of Mo isotopic fractionation associated with adsorption onto Fe-Mn-oxides and spatially variable H2S concentrations in the euxinic watermass. By compiling published data, we found that the large sedimentary δ98Mo variations previously observed in the early Cambrian Nanhua Basin and in other Neoproterozoic-Cambrian marine basins can be similarly explained. Our model provides a novel interpretation of the Mo biogeochemistry of early Earth oceans, within the framework of which Mo isotopes may serve to further our understanding of the oxygenation history of the Earth-surface system.

  8. Space agriculture in micro- and hypo-gravity: A comparative study of soil hydraulics and biogeochemistry in a cropping unit on Earth, Mars, the Moon and the space station

    Science.gov (United States)

    Maggi, Federico; Pallud, Céline

    2010-12-01

    Increasing interest is developing towards soil-based agriculture as a long-term bioregenerative life support during space and planetary explorations. Contrary to hydroponics and aeroponics, soil-based cropping would offer an effective approach to sustain food and oxygen production, decompose organic wastes, sequester carbon dioxide, and filter water. However, the hydraulics and biogeochemical functioning of soil systems exposed to gravities lower than the Earth's are still unknown. Since gravity is crucial in driving water flow, hypogravity will affect nutrient and oxygen transport in the liquid and gaseous phases, and could lead to suffocation of microorganisms and roots, and emissions of toxic gases. A highly mechanistic model coupling soil hydraulics and nutrient biogeochemistry previously tested on soils on Earth ( g=9.806 m s -2) is used to highlight the effects of gravity on the functioning of cropping units on Mars (0.38 g), the Moon (0.16 g), and in the international space station (ISS, nearly 0 g). For each scenario, we have compared the net leaching of water, the leaching of NH 3, NH 4+, NO 2- and NO 3- solutes, the emissions of NH 3, CO 2, N 2O, NO and N 2 gases, the concentrations profiles of O 2, CO 2 and dissolved organic carbon (DOC) in soil, the pH, and the dynamics of various microbial functional groups within the root zone against the same control variables in the soil under terrestrial gravity. The response of the soil ecodynamics was relatively linear; gravitational accelerations lower than the Earth's resulted in 90-100% lower water leaching rates, 95-100% lower nutrient leaching rates, and lower emissions of NH 3 and NO gases (80-95% and 30-40%, respectively). Lower N loss through leaching resulted in 60-100% higher concentration of the microbial biomass, but did not alter the vertical stratification of the microbial functional groups with respect to the stratification on Earth. However, the higher biomass concentration produced higher

  9. Biogeochemistry: Soil carbon in a beer can

    Science.gov (United States)

    Davidson, Eric A.

    2015-10-01

    Decomposition of soil organic matter could be an important positive feedback to climate change. Geochemical properties of soils can help determine what fraction of soil carbon may be protected from climate-induced decomposition.

  10. Heavy metals biogeochemistry in abandoned mining areas

    Directory of Open Access Journals (Sweden)

    Favas P. J. C.

    2013-04-01

    Full Text Available Plants growing on the abandoned Portuguese mines, highly contaminated with W, Sn, As, Cd, Cu, Zn and Pb, have been studied for their biogeochemical indication/prospecting and mine restoration potential. The results of analysis show that the species best suited for biogeochemical indicating are: aerial tissues of Halimium umbellatum (L. Spach, for As and W; leaves of Erica arborea L. for Bi, Sn, W and mostly Pb; stems of Erica arborea L. for Pb; needles of Pinus pinaster Aiton and aerial tissues of Pteridium aquilinum (L. Kuhn for W; and leaves of Quercus faginea Lam. for Sn. The aquatic plant studied (Ranunculus peltatus Schrank can be used to decrease the heavy metals, and arsenic amounts into the aquatic environment affected by acid mine drainages.

  11. Biogeochemistry of metalliferous mine tailings during phytostabilizatio

    Science.gov (United States)

    Chorover, J.; Root, R. A.; Hammond, C.; Wang, Y.; Maier, R. M.

    2015-12-01

    In the semi-arid southwest US, legacy mine tailings and the associated metal(loid) contaminants, are prone to wind dispersion and water erosion. Without remediation, tailings can remain barren for decades to centuries, providing a point source of toxic contamination. Successful mitigation of toxins (As, Pb) from fugitive dust is often limited to confinement and stabilization. Capping mine tailings with soil or gravel is an accepted, although expensive, strategy to reduce erosion. Revegetation via assisted direct planting (also known as phytostabilization) has the potential to be a cost-effective and self-sustaining alternative "green-technology" to expensive capping. The impact of phytostabilization, and requisite added organic carbon and irrigation on mechanisms of contaminant mobility is being investigated with concurrent highly-instrumented greenhouse mesocosms and in situ field studies using advanced microbiological tools and synchrotron x-ray based molecular probes. Composted treatments initially neutralized the near surface acid tailings (~2 to ~6.5). However, after 9 mo the mesocosms showed a gradual and eventual decrease back to pH 2. The exception was the root zone of Atriplex lentiformis, which buffered the acidic conditions for 12 months. Rhizosphere microbiota experienced a 5-log increase in the compost-amended compared to control greenhouse mesocosms. Weathering of the primary sulfidic mineral assemblage, indicated by the iron and sulfur speciation, was shown to control the mobility, speciation and bioavailability of both As and Pb via sequestration in (meta)stable neoformed jarosite phases as plumbojarosite and As(V) substituted for sulfate in hydronium jarosite, with important implications for human and environmental health risk management. We conclude that the disequilibrium imposed by phytostabilization results in an increase of heterotrophic biomass that is concurrent with a time series of geochemical transformations, which controls the species, fate, and bioavailability of toxic metal(loid)s. This long-term, multi-disciplinary, multi-scale study describes changes in contaminant lability promoted by biogeochemical weathering and helps establish the feasibility of phytostabilization.

  12. Forest biogeochemistry in response to drought.

    Science.gov (United States)

    Schlesinger, William H; Dietze, Michael C; Jackson, Robert B; Phillips, Richard P; Rhoades, Charles C; Rustad, Lindsey E; Vose, James M

    2016-07-01

    Trees alter their use and allocation of nutrients in response to drought, and changes in soil nutrient cycling and trace gas flux (N2 O and CH4 ) are observed when experimental drought is imposed on forests. In extreme droughts, trees are increasingly susceptible to attack by pests and pathogens, which can lead to major changes in nutrient flux to the soil. Extreme droughts often lead to more common and more intense forest fires, causing dramatic changes in the nutrient storage and loss from forest ecosystems. Changes in the future manifestation of drought will affect carbon uptake and storage in forests, leading to feedbacks to the Earth's climate system. We must improve the recognition of drought in nature, our ability to manage our forests in the face of drought, and the parameterization of drought in earth system models for improved predictions of carbon uptake and storage in the world's forests.

  13. Hydrography and biogeochemistry of the coastal ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A; Unnikrishnan, A

    The coastal ocean accounts for only 7% of the total oceanic area, but it plays a very important role in biogeochemical cycles. It not only exchanges energy and matter with the open ocean, but terrestrial inputs of materials such as freshwater...

  14. Biogeochemistry of a temperate forest nitrogen gradient

    Science.gov (United States)

    Perakis, Steven S.; Sinkhorn, Emily R.

    2011-01-01

    Wide natural gradients of soil nitrogen (N) can be used to examine fundamental relationships between plant–soil–microbial N cycling and hydrologic N loss, and to test N-saturation theory as a general framework for understanding ecosystem N dynamics. We characterized plant production, N uptake and return in litterfall, soil gross and net N mineralization rates, and hydrologic N losses of nine Douglas-fir (Pseudotsuga menziesii) forests across a wide soil N gradient in the Oregon Coast Range (USA). Surface mineral soil N (0–10 cm) ranged nearly three-fold from 0.29% to 0.78% N, and in contrast to predictions of N-saturation theory, was linearly related to 10-fold variation in net N mineralization, from 8 to 82 kg N·ha−1·yr−1. Net N mineralization was unrelated to soil C:N, soil texture, precipitation, and temperature differences among sites. Net nitrification was negatively related to soil pH, and accounted for −1·yr−1. Aboveground net primary production per unit net N mineralization varied inversely with soil N, suggesting progressive saturation of plant N demands at high soil N. Hydrologic N losses were dominated by dissolved organic N at low-N sites, with increased nitrate loss causing a shift to dominance by nitrate at high-N sites, particularly where net nitrification exceeded plant N demands. With the exception of N mineralization patterns, our results broadly support the application of the N-saturation model developed from studies of anthropogenic N deposition to understand N cycling and saturation of plant and microbial sinks along natural soil N gradients. This convergence of behavior in unpolluted and polluted forest N cycles suggests that where future reductions in deposition to polluted sites do occur, symptoms of N saturation are most likely to persist where soil N content remains elevated.

  15. Biogeochemistry of the North Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    DileepKumar, M.

    sure the material provided here will be of use to scientists and science students interested in IGBP. J S Singh Chairman, IGBP-WCRP-SCOPE National Committee Fax: (0542) 2368174 E-mail: jssingh@bhu.ac.in J S SINGH PhD FTWAS FNA FASc FNASc BANARAS HINDU... materials from the Indian subcontinent during heavy discharge periods facilitates removal of organic matter from the water column in the Bay of Bengal. The Arabian Sea assumes significance as it accounts for about 30% of the global midwater column nitrate...

  16. Biogeochemistry of microbial coal-bed methane

    Science.gov (United States)

    Strc, D.; Mastalerz, Maria; Dawson, K.; MacAlady, J.; Callaghan, A.V.; Wawrik, B.; Turich, C.; Ashby, M.

    2011-01-01

    Microbial methane accumulations have been discovered in multiple coal-bearing basins over the past two decades. Such discoveries were originally based on unique biogenic signatures in the stable isotopic composition of methane and carbon dioxide. Basins with microbial methane contain either low-maturity coals with predominantly microbial methane gas or uplifted coals containing older, thermogenic gas mixed with more recently produced microbial methane. Recent advances in genomics have allowed further evaluation of the source of microbial methane, through the use of high-throughput phylogenetic sequencing and fluorescent in situ hybridization, to describe the diversity and abundance of bacteria and methanogenic archaea in these subsurface formations. However, the anaerobic metabolism of the bacteria breaking coal down to methanogenic substrates, the likely rate-limiting step in biogenic gas production, is not fully understood. Coal molecules are more recalcitrant to biodegradation with increasing thermal maturity, and progress has been made in identifying some of the enzymes involved in the anaerobic degradation of these recalcitrant organic molecules using metagenomic studies and culture enrichments. In recent years, researchers have attempted lab and subsurface stimulation of the naturally slow process of methanogenic degradation of coal. Copyright ?? 2011 by Annual Reviews. All rights reserved.

  17. The Marine Biogeochemistry of Zinc Isotopes

    Science.gov (United States)

    2007-06-01

    dust (Niger) Sapropel (Mediterranean) 4* Deep-Sea Sediments * • Lobster Liver Mussel tissue Plankton Zooplankton Zinc ores * * * Sediment trap material...of natural plankton over large changes in nutrient concentrations in the Peru Upwelling Region. This suggests either that the isotope effect for Zn...hydrothermal fluids and minerals, cultured marine phytoplankton, natural plankton , and seawater. By measuring Zn isotopes in a diverse array of

  18. Biogeochemistry of Decomposition and Detrital Processing

    Science.gov (United States)

    Sanderman, J.; Amundson, R.

    2003-12-01

    Decomposition is a key ecological process that roughly balances net primary production in terrestrial ecosystems and is an essential process in resupplying nutrients to the plant community. Decomposition consists of three concurrent processes: communition or fragmentation, leaching of water-soluble compounds, and microbial catabolism. Decomposition can also be viewed as a sequential process, what Eijsackers and Zehnder (1990) compare to a Russian matriochka doll. Soil macrofauna fragment and partially solubilize plant residues, facilitating establishment of a community of decomposer microorganisms. This decomposer community will gradually shift as the most easily degraded plant compounds are utilized and the more recalcitrant materials begin to accumulate. Given enough time and the proper environmental conditions, most naturally occurring compounds can completely be mineralized to inorganic forms. Simultaneously with mineralization, the process of humification acts to transform a fraction of the plant residues into stable soil organic matter (SOM) or humus. For reference, Schlesinger (1990) estimated that only ˜0.7% of detritus eventually becomes stabilized into humus.Decomposition plays a key role in the cycling of most plant macro- and micronutrients and in the formation of humus. Figure 1 places the roles of detrital processing and mineralization within the context of the biogeochemical cycling of essential plant nutrients. Chapin (1991) found that while the atmosphere supplied 4% and mineral weathering supplied no nitrogen and internal nutrient recycling is the source for >95% of all the nitrogen and phosphorus uptake by tundra species in Barrow, Alaska. In a cool temperate forest, nutrient recycling accounted for 93%, 89%, 88%, and 65% of total sources for nitrogen, phosphorus, potassium, and calcium, respectively ( Chapin, 1991). (13K)Figure 1. A decomposition-centric biogeochemical model of nutrient cycling. Although there is significant external input (1) and output (2) from neighboring ecosystems (such as erosion), weathering of primary minerals (3), loss of secondary minerals (4), atmospheric deposition and N-fixation (5) and volatilization (6), the majority of plant-available nutrients are supplied by internal recycling through decomposition. Nutrients that are taken up by plants (7) are either consumed by fauna (8) and returned to the soil through defecation and mortality (10) or returned to the soil through litterfall and mortality (9). Detritus and humus can be immobilized into microbial biomass (11 and 13). Humus is formed by the transformation and stabilization of detrital (12) and microbial (14) compounds. During these transformations, SOM is being continually mineralized by the microorganisms (15) replenishing the inorganic nutrient pool (after Swift et al., 1979). The second major ecosystem role of decomposition is in the formation and stabilization of humus. The cycling and stabilization of SOM in the litter-soil system is presented in a conceptual model in Figure 2. Parallel with litterfall and most root turnover, detrital processing is concentrated at or near the soil surface. As labile SOM is preferentially degraded, there is a progressive shift from labile to passive SOM with increasing depth. There are three basic mechanisms for SOM accumulation in the mineral soil: bioturbation or physical mixing of the soil by burrowing animals (e.g., earthworms, gophers, etc.), in situ decomposition of roots and root exudates, and the leaching of soluble organic compounds. In the absence of bioturbation, distinct litter layers often accumulate above the mineral soil. In grasslands where the majority of net primary productivity (NPP) is allocated belowground, root inputs will dominate. In sandy soils with ample rainfall, leaching may be the major process incorporating carbon into the soil. (11K)Figure 2. Conceptual model of carbon cycling in the litter-soil system. In each horizon or depth increment, SOM is represented by three pools: labile SOM, slow SOM, and passive SOM. Inputs include aboveground litterfall and belowground root turnover and exudates, which will be distributed among the pools based on the biochemical nature of the material. Outputs from each pool include mineralization to CO2 (dashed lines), humification (labile→slow→passive), and downward transport due to leaching and physical mixing. Communition by soil fauna will accelerate the decomposition process and reveal previously inaccessible materials. Soil mixing and other disturbances can also make physically protected passive SOM available to microbial attack (passive→slow). There exists an amazing body of literature on the subject of decomposition that draws from many disciplines - including ecology, soil science, microbiology, plant physiology, biochemistry, and zoology. In this chapter, we have attempted to draw information from all of these fields to present an integrated analysis of decomposition in a biogeochemical context. We begin by reviewing the composition of detrital resources and SOM (Section 8.07.2), the organisms responsible for decomposition ( Section 8.07.3), and some methods for quantifying decomposition rates ( Section 8.07.4). This is followed by a discussion of the mechanisms behind decomposition ( Section 8.07.5), humification ( Section 8.07.6), and the controls on these processes ( Section 8.07.7). We conclude the chapter with a brief discussion on how current biogeochemical models incorporate this information ( Section 8.07.8).

  19. Marine biogeochemistry: Phytoplankton in a witch's brew

    Science.gov (United States)

    Behrenfeld, Michael

    2016-03-01

    Natural seafloor hydrocarbon seeps are responsible for roughly half of the oil released into the ocean. As these oils and gases rise to the surface, they transport nutrients upwards, benefiting phytoplankton in the upper sunlit layer.

  20. An Overview on Biogeochemistry During the Decade of 2001 to 2010%2001-2010年生物地球化学研究进展与展望

    Institute of Scientific and Technical Information of China (English)

    谢树成; 罗根明; 宋金明; 李超; 黄咸雨; 杨欢; 李一良; 黄俊华; 胡超涌

    2012-01-01

    阐述了21世纪第一个十年生物地球化学领域的重要研究进展和未来可能的重点发展方向.在近代陆-海系统碳循环的库和通量上已经取得了重要进展,并发现了一些参与氮、硫循环新的微生物功能群.阐述了显生宙生物大灭绝期间碳循环异常的特点及其可能的原因,但对氮、硫循环的了解比较薄弱.地球早期的碳、硫循环与生命起源、大气和海洋水化学条件的关系已经取得重要认识.生物地球化学过程可以通过生态毒理,以及大气成分和海洋水化学条件的改变影响生命系统.微生物地球化学功能的微区、原位、痕量示踪等技术得到快速发展.未来将加强地质历史时期碳、氮、硫循环的定量分析以及空间变化的研究,各种元素循环之间的相互关系及其界面过程、极端环境的生物地球化学过程将进一步受到重视.生命科学领域重要技术的引入将提升生物地球化学过程的研究.%The significant achievements and future research orientation of biogeochemistry during the decade of 2001 to 2010 are briefly reviewed. Some carbon pools and related flux have been quantified in modern marine/ocean and land ecosystems. New microbial functional groups involved in sulfur and nitrogen cycles of modern ecosystems have been identified. The features and the possible causes of the abnormal carbon cycle occurring during the biotic crisis in Phanerozoic have been deciphered but the biogeochemical cycles of sulfur and nitrogen need more investigation. The relationship of carbon and sulfur cycles of the early Earth with life origins, atmospheric and oceanic chemistry conditions has been understood. Biogeochemical impacts on ecosystems via the chemical substances, climatic and o-ceanic changes are reviewed concerning both the modern and the ancient times. Some biogeochemical techniques including geotraces, metagenomics, micro-scale and in-situ analyses are particularly

  1. Iron biogeochemistry in Antarctic pack ice during SIPEX-2

    Science.gov (United States)

    Lannuzel, Delphine; Chever, Fanny; van der Merwe, Pier C.; Janssens, Julie; Roukaerts, Arnout; Cavagna, Anne-Julie; Townsend, Ashley T.; Bowie, Andrew R.; Meiners, Klaus M.

    2016-09-01

    Our study quantified the spatial and temporal distribution of Fe and ancillary biogeochemical parameters at six stations visited during an interdisciplinary Australian Antarctic marine science voyage (SIPEX-2) within the East Antarctic first-year pack ice zone during September-October 2012. Unlike previous studies in the area, the sea ice Chlorophyll a, Particulate Organic Carbon and Nitrogen (POC and PON) maxima did not occur at the ice/water interface because of the snow loading and dynamic processes under which the sea ice formed. Iron in sea ice ranged from 0.9 to 17.4 nM for the dissolved (0.2 μm) fraction. Our results highlight that the concentration of particulate Fe in sea ice was highest when approaching the continent. The high POC concentration and high particulate iron to aluminium ratio in sea ice samples demonstrate that 71% of the particulate Fe was biogenic in composition. Our estimated Fe flux from melting pack ice to East Antarctic surface waters over a 30 day melting period was 0.2 μmol/m2/d of DFe, 2.7 μmol/m2/d of biogenic PFe and 1.3 μmol/m2/d of lithogenic PFe. These estimates suggest that the fertilization potential of the particulate fraction of Fe may have been previously underestimated due to the assumption that it is primarily lithogenic in composition. Our new measurements and calculated fluxes indicate that a large fraction of the total Fe pool within sea ice may be bioavailable and therefore, effective in promoting primary productivity in the marginal ice zone.

  2. Soil biogeochemistry, plant physiology and phytoremediation of cadmium contaminated soils

    Science.gov (United States)

    Cadmium (Cd) loading in soil and the environment has been accelerated worldwide due to enhanced industrialization and intensified agricultural production, particularly in the developing countries. Soil Cd pollution, resulting from both anthropogenic and geogenic sources, has posed an increasing chal...

  3. Carbon isotope biogeochemistry of plant resins and derived hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Murray, A.P.; Edwards, D.; Hope, J.M.; Boreham, C.J. [Australian Geological Survey Organisation, Canberra (Australia)] [and others

    1998-12-31

    Hydrocarbons derived from plant resins are major components of some terrigenous oils and bitumens. These compounds are structurally distinct and this makes then useful biomarkers applicable in petroleum exploration as well as sources of biogeochemical information about palaeoenvironment and palaeobotany. Although recent studies have elucidated the molecular structure of resinites, very little information has been available for the carbon isotope composition of resinites and no studies of resin-derived compounds in oils had been performed prior to the present study. Hence, carbon stable isotope analyses were carried out on a suite of modern and fossil resins of diverse origins, including compound specific isotope analysis of individual hydrocarbons produced during resin pyrolysis. Oils derived from resinite source organic matter were also analysed. The results showed that ``Class I`` resinites derived from gymnosperms were enriched in the heavy carbon isotope compared with those from angiosperms (``Class I`` resinites). Furthermore, both fossil resinites themselves and individual hydrocarbons derived from them were isotopically heavy compared with modern plant resins. The isotopic signatures of diterpanes and triterpanes in various early Tertiary oils from Australasia and Southeast Asia reflect their origins from gymnosperms and angiosperms, respectively. (author)

  4. Integrating biogeochemistry and ecology into ocean data assimilation systems

    DEFF Research Database (Denmark)

    Brasseur, Pierre; Gruber, Nicolas; Barciela, Rosa

    2009-01-01

    Monitoring and predicting the biogeochemical state of the ocean and marine ecosystems is an important application of operational oceanography that needs to be expanded. The accurate depiction of the ocean's physical environment enabled by Global Ocean Data Assimilation Experiment (GODAE) systems...... that are not yet considered essential, such as upper-ocean vertical fluxes that are critically important to biological activity. Further, the observing systems will need to be expanded in terms of in situ platforms (with intensified deployments of sensors for O-2 and chlorophyll, and inclusion of new sensors...... and temporal scales. In this paper, we discuss recent developments that enable coupling new biogeochemical models and assimilation components with the existing GODAE systems, and we examine the potential of such systems in several areas of interest: phytoplankton biomass monitoring in the open ocean, ocean...

  5. BioGeochemistry of antimony, Sources, Transfers, Impacts and Assessment

    Science.gov (United States)

    Le Roux, Gael; Pinelli, Eric; Hedde, Mickael; Guiresse, Maritxu; De Vleeschouwer, François; Silvestre, Jérôme; Enrico, Maxime; Gandois, Laure; Monna, Fabrice; Gers, Charles; Probst, Anne

    2013-04-01

    BioGeoSTIB is a project funded by ADEME (French Environmental Protection Agency). Its aim is to provide a better understanding of biogeochemical cycle disturbances of antimony by man. Specifically, it is focused on the atmosphere-soil-organism interfaces. Based on a multi-scale approach, the impact of antimony on organisms and organism communities and the factors of Sb dispersion in the environment aim to better characterized. This report gives the main results of 2 and 1 -2 years of research. Using peat bogs as environmental archives, we show that Sb contamination in soils date back to the beginning of the metallurgy. Atmospheric deposition of Sb largely increased by 100 times during the Industrial Revolution compared to natural levels (~0,001-0,01 mg m-2 an-1) estimated in the deepest peat layers. This disturbance in the antimony geochemical cycle modified its concentrations in soils. One main source of present Sb contamination is automotive traffic due to Sb in braking lines. This emerging contamination was characterized close to a roundabout. This additional source of Sb does not seem to impact soil fauna but Sb concentrations in soil solutions exceed 1 μg L-1. Genotoxicity tests have been performed on the model plant Vicia faba and show that antimony is genotoxic at its lowest concentrations and that there is a synergistic effect lead, a trace metal frequently found in association with antimony in the environment. It is a main issue to determine Sb critical loads in the environment but main identified lacks are thermodynamic data, which are not available yet, to model the behavior of Sb in soil solutions and the fact the antimony is always associated with other anthropogenic trace metals like lead. Critical thresholds of Sb have been determined for the first time based on genotoxicity experiment. Simulations show that these thresholds can be exceeded in the future, whereas present limits for invertebrates (US-EPA) are and will not be reached. However, scientific problems to complete the "critical load" approach are, as stated aabove, present lack of thermodynamic data on Sb to model its behavior in the soil solution and the fact the Sb is always linked to other trace metals, with potential ecological impacts too.

  6. Improved paleoenvironmental interpretations at the intersection between paleontology and biogeochemistry

    Science.gov (United States)

    Lyons, T. W.

    2012-04-01

    Paleoenviromental reconstructions, particularly those focused of oxygen levels in the ancient ocean, often rely on geochemical or paleoecological approaches but too infrequently exploit the added strength that comes with a combined approach. Trace metal, organic biomarker, and iron paleoredox proxies do well in distinguishing between ancient oxic water columns and anoxic, Fe-rich (ferruginous) and anoxic, sulfidic (euxinic) settings. Molybdenum isotope approaches may even allow us to estimate the amount of hydrogen sulfide in the ancient seawater. Where the challenges often arise are at intermediate redox states marked by episodes of only transient anoxia/euxinia where diagnostic geochemical end-member enrichments are muted. Unfortunately, rapid detrital sedimentation and depleted seawater metal inventories under anoxic/euxinic conditions on basin and ocean scales can yield similarly tempered metal enrichments. Intermediate geochemical signatures can also mark conditions of extremely low bottom-water oxygen (often referred to as 'suboxic') but with sulfide confined to the pore fluids and a lack of appreciable and persistent Fe availability in the water column. Also possible are protracted episodes of true anoxia that lack Fe or sulfide in the water column because of limited availability of the organic matter required to drive bacterial Fe and sulfate reduction. In contrast, benthic ecological relationships, both trace and body fossil, are very sensitive to redox fluctuations at the low oxygen end, even brief episodes of oxygenation, and across subtle spatiotemporal redox gradients, although they are not readily effective at distinguishing between ferruginous and euxinic bottom waters. The talk will explore the mechanistic underpinnings of some of the most important geochemical proxies and then view their relative strengths and weaknesses in light of the added insight gleaned via coupled paleoecological analysis. Beyond stronger interpretations of Phanerozoic paleoenvironments using the combined approach, subtle variations in chemical tracers can be calibrated with refined paleoredox resolution using fossils and extrapolated back to Precambrian intervals predating the evolutionary appearance of animals. Oxygen deficiencies of varying degree likely dominated most of the Precambrian marine record. Additional topics to be discussed are new and refined geochemical proxies that work best under intermediate redox states. Another interesting intersection of Fe and trace metal proxies and biology lies with the clear fingerprints of depositional settings with abundant free hydrogen sulfide in the pore fluids, often right at the sediment-water interface, but with oxygen in the bottom waters. Independent recognition of such conditions would have important impact on our interpretations of infaunal and epifaunal animal communities, including those that thrive at redox interfaces in symbiotic partnership with thiotrophic and methanotropic bacteria.

  7. Ocean biogeochemistry and atmospheric composition: Significance of the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; Jayakumar, D.A.

    character of CO 2 , respiration and photo synthesis cause a decrease and an increase of sea water pH, respectively. The relatively high pH of oceanic surface waters keeps pCO 2 at moderately low levels (Figure 3). This is largely responsible for Figure 1... productivity and hence in the rate at which CO 2 is removed from the atmosphere; this in turn can force climate changes 12 . How the balance is achieved on geological time scales is an important problem that is currently attracting the attention...

  8. Antimony and arsenic biogeochemistry in the western Atlantic Ocean

    Science.gov (United States)

    Cutter, Gregory A.; Cutter, Lynda S.; Featherstone, Alison M.; Lohrenz, Steven E.

    The subtropical to equatorial Atlantic Ocean provides a unique regime in which one can examine the biogeochemical cycles of antimony and arsenic. In particular, this region is strongly affected by inputs from the Amazon River and dust from North Africa at the surface, and horizontal transport at depth from high-latitude northern (e.g., North Atlantic Deep Water) and southern waters (e.g., Antarctic Bottom and Intermediate Waters). As a part of the 1996 Intergovernmental Oceanographic Commission's Contaminant Baseline Survey, data for dissolved As(III+V), As(III), mono- and dimethyl arsenic, Sb(III+V), Sb(III), and monomethyl antimony were obtained at six vertical profile stations and 44 sites along the 11,000 km transect from Montevideo, Uruguay, to Bridgetown, Barbados. The arsenic results were similar to those in other oceans, with moderate surface depletion, deep-water enrichment, a predominance of arsenate (>85% As(V)), and methylated arsenic species and As(III) in surface waters that are likely a result of phytoplankton conversions to mitigate arsenate "stress" (toxicity). Perhaps the most significant discovery in the arsenic results was the extremely low concentrations in the Amazon Plume (as low as 9.8 nmol/l) that appear to extend for considerable distances offshore in the equatorial region. The very low concentration of inorganic arsenic in the Amazon River (2.8 nmol/l; about half those in most rivers) is probably the result of intense iron oxyhydroxide scavenging. Dissolved antimony was also primarily in the pentavalent state (>95% antimonate), but Sb(III) and monomethyl antimony were only detected in surface waters and displayed no correlations with biotic tracers such as nutrients and chlorophyll a. Unlike As(III+V)'s nutrient-type vertical profiles, Sb(III+V) displayed surface maxima and decreased into the deep waters, exhibiting the behavior of a scavenged element with a strong atmospheric input. While surface water Sb had a slight correlation with dissolved Al, it is likely that atmospheric Sb is delivered with combustion by-products and not from mineral aerosols. In the Amazon Plume, antimony concentrations dropped substantially, and an Amazon River sample had a concentration (0.25 nmol/l) that was less than one-fourth those found in other major rivers. Using these river data, and estimates of atmospheric fluxes based on shipboard measurements and collections from Barbados, the atmospheric deposition of antimony to the equatorial Atlantic (2°S-8°N) is twice the Amazon flux, while the atmospheric deposition of arsenic is only 10% of the river's flux.

  9. Marine Primary and Secondary Aerosol emissions related to seawater biogeochemistry

    Science.gov (United States)

    Sellegri, Karine; D'Anna, Barbara; Marchand, Nicolas; Charriere, Bruno; Sempere, Richard; Mas, Sebastien; Schwier, Allison; Rose, Clémence; Pey, Jorge; Langley Dewitt, Helen; Même, Aurélie; R'mili, Badr; George, Christian; Delmont, Anne

    2014-05-01

    Marine aerosol contributes significantly to the global aerosol load and consequently has an important impact on both the Earth's albedo and climate. Different factors influence the way they are produced from the sea water and transferred to the atmosphere. The sea state (whitecap coverage) and sea temperature influence the size and concentration of primarily produced particles but also biogeochemical characteristics of the sea water may influence both the physical and chemical fluxes. In order to study marine emissions, one approach is to use semicontrolled environments such as mesocosms. Within the SAM project (Sources of marine Aerosol in the Mediterranean), we characterize the primary Sea Salt Aerosol (SSA) and Secondary aerosol formation by nucleation during mesocosms experiments performed in May 2013 at the Oceanographic and Marine Station STARESO in western Corsica. We followed both water and air characteristics of three mesocosms containing an immerged part filled with 3,3 m3 of sea water and an emerged part filled with filtered natural air. Mesocosms were equipped with a pack of optical and physicochemical sensors and received different treatments: one of these mesocosms was left unchanged as control and the two others were enriched by addition of nitrates and phosphates respecting Redfield ratio (N:P = 16) in order to create different levels of phytoplanctonic activities. The set of sensors in each mesocosm was allowed to monitor the water temperature, conductivity, pH, incident light, fluorescence of chlorophyll a, and dissolved oxygen concentration. The mesocosms waters were daily sampled for chemical and biological (dissolved organic matter (i.e. DOC and CDOM), particulate matter and related polar compounds, transparent polysaccharides and nutrients concentration) and biological (chlorophyll a, virus, bacteria, phytoplankton and zooplankton concentrations) analyses. Secondary new particle formation was followed on-line in the emerged parts of the mesocosms, while a primary production by bubble bursting was simulated from a sample of sea water in a dedicated set-up every day. The size segregated aerosol number fluxes, cloud condensation nuclei (CCN) fluxes, and biological and organic contents were determined as a function of the sea water characteristics.

  10. Aphid infestation affecting the biogeochemistry of European beech saplings

    Science.gov (United States)

    Michalzik, B.; Levia, D. F., Jr.; Bischoff, S.; Näthe, K.

    2014-12-01

    Mass outbreaks of herbivore insects are known to perturb the functional properties of forests. However, it is less clear how endemic to moderate aboveground herbivory affects the vertical flow of nutrients from tree canopies to the soil. Here, we report on the effects of low to moderate infestation levels of the woolly beech aphid (Phyllaphis fagi L.) on the nutrient dynamics and hydrology of European beech (Fagus sylvatica L.). In a potted sapling experiment, we followed the vertical dynamics of nutrients via throughfall (TF), stemflow (SF) and litter leachates (LL) collected over ten weeks underneath infested and uninfested control trees. Aphid infestation amplifies the fluxes of K+, Mn2+ and particulate nitrogen (0.45μm factor of up to 200 compared to TF.Imaging of leaf surfaces by scanning electron microscopy exhibited notable differences of the surface morphology and microbiology of control, lightly infested, and heavily infested leaves. This observation might point to an aphid-mediated alteration of the phyllosphere ecology triggering the microbial uptake of NH4-N and SO4-S and its transformation to particulate N by magnified biomass growth of the phyllosphere microflora, consequently changing the chemical partitioning and temporal availability of nitrogen.

  11. Coupling among Microbial Communities, Biogeochemistry, and Mineralogy across Biogeochemical Facies

    Energy Technology Data Exchange (ETDEWEB)

    Stegen, James C.; Konopka, Allan; McKinely, Jim; Murray, Christopher J.; Lin, Xueju; Miller, Micah D.; Kennedy, David W.; Miller, Erin A.; Resch, Charles T.; Fredrickson, Jim K.

    2016-07-29

    Physical properties of sediments are commonly used to define subsurface lithofacies and these same physical properties influence subsurface microbial communities. This suggests an (unexploited) opportunity to use the spatial distribution of facies to predict spatial variation in biogeochemically relevant microbial attributes. Here, we characterize three biogeochemical facies—oxidized, reduced, and transition—within one lithofacies and elucidate relationships among facies features and microbial community biomass, diversity, and community composition. Consistent with previous observations of biogeochemical hotspots at environmental transition zones, we find elevated biomass within a biogeochemical facies that occurred at the transition between oxidized and reduced biogeochemical facies. Microbial diversity—the number of microbial taxa—was lower within the reduced facies and was well-explained by a combination of pH and mineralogy. Null modeling revealed that microbial community composition was influenced by ecological selection imposed by redox state and mineralogy, possibly due to effects on nutrient availability or transport. As an illustrative case, we predict microbial biomass concentration across a three-dimensional spatial domain by coupling the spatial distribution of subsurface biogeochemical facies with biomass-facies relationships revealed here. We expect that merging such an approach with hydro-biogeochemical models will provide important constraints on simulated dynamics, thereby reducing uncertainty in model predictions.

  12. The Microbial Carbon Pump: A new Concept in Marine Biogeochemistry

    Science.gov (United States)

    Weinbauer, Markus; Jiao, Nianzhi

    2013-04-01

    Traditionally, three mechanisms, called pumps, have been suggested to explain the vertical distribution of carbon in the water column: The solubility pump, the carbonate pump and biological carbon pump (BCP). Recently, the conceptual framework of the microbial carbon pump (MCP) has been developed by the SCOR (Scientific Committee on Oceanic Research) WG 134. The MCP is defined as the transfer of labile organic matter into recalcitrant organic matter by microbial activity (microbial loop and viral shunt) causing long-term storage of carbon. The major pathways of the MCP are: 1) Direct exudation of microbial cells during production and proliferation, 2) viral lysis of microbial cells releasing microbial cell wall and cell surface macromolecules and 3) organic aggregate (particle) degradation and transformation.The MCP is important for understanding the marine carbon cycle, since the carbon content in marine dissolved organic matter (DOM, DOC) is similar to the carbon content of CO2 in the atmosphere. First estimates indiacte that the capacity of carbon sequestration into deep marine waters and sediments of the BCP and MCP is in the same order of magnitude (0.4 and 0.5-0.6 Gt C per yr). The fourth carbon pump is likely an important mechanism in the marine carbon cycle and potentially vulnerable to global change.

  13. Biogeochemistry: Long-term effects of permafrost thaw

    Science.gov (United States)

    Zona, Donatella

    2016-09-01

    Carbon emissions from the Arctic tundra could increase drastically as global warming thaws permafrost. Clues now obtained about the long-term effects of such thawing on carbon dioxide emissions highlight the need for more data.

  14. Impact of bacterial NO3- transport on sediment biogeochemistry

    DEFF Research Database (Denmark)

    Sayama, Mikio; Risgaard-Petersen, Nils; Nielsen, Lars Peter;

    2005-01-01

    Experiments demonstrated that Beggiatoa could induce a H2S-depleted suboxic zone of more than 10 mm in marine sediments and cause a divergence in sediment NO3– reduction from denitrification to dissimilatory NO3– reduction to ammonium. pH, O2, and H2S profiles indicated that the bacteria oxidized H......2S with NO3– and transported S0 to the sediment surface for aerobic oxidation....

  15. Biogeochemistry of Nutrient Elements in the Changjiang (Yangtze River) Estuary

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Based on the biogeochemical studies on nutrient elements in the Changjiang estuary,the main results and recent progresses are reviewed in this paper, such as the nutrient fluxes into the sea, the mixing behaviors, the distribution characteristics and transportation as well as the biogeochemical behaviors of nutrients in the plume frontal region. The exploring directions and research emphases in the future are proposed.

  16. Biogeochemistry of Antimony(V) in Microcosms under Sulfidogenic Conditions

    Science.gov (United States)

    O'Loughlin, E. J.; Johnson, C. R.; Antonopoulos, D. A.; Boyanov, M.; Flynn, T. M.; Koval, J. C.; Kemner, K. M.

    2015-12-01

    As the mining and use of antimony continues to increase, environmental concerns involving the element have grown. Antimony(V) and (III) are the two most environmentally-relevant oxidation states, but little is known about the redox transitions between the two in natural systems. To better understand the behavior of antimony in anoxic environments, we examined the transformations of Sb(V) under Fe(III)- and sulfate-reducing conditions in aqueous suspensions that contained 2 mM KSb(OH)6, 50 mM Fe(III) (as ferrihydrite), 10 mM sulfate, and 10 mM lactate, and were inoculated with sediment from a wetland on the campus of Argonne National Laboratory in Argonne, Illinois. Samples were collected over time to track changes in the concentrations of Sb, Fe(II), sulfate, and lactate, as well as the composition of the microbial community as determined by 16S rRNA gene inventories. We also examined the interaction of Sb(V) with pure Fe(II) mineral phases in aqueous suspensions containing 2 mM KSb(OH)6 and 50 mM Fe(II) as either magnetite, sideritre, vivianite, green rust, or mackinawite. X-ray absorption fine-structure spectroscopy was used to determine the valence state of Sb and its chemical speciation. Lactate was rapidly fermented to acetate and propionate concomittant with a bloom of Veillonellaceae. Utilization of propionate for dissimilatory sulfate reduction (DSR) was accompanied by an increase in Desulfobulbaceae. Sb K-edge X-Ray absorption near edge structure (XANES) analysis showed reduction of Sb(V) to Sb(III) within 4 weeks, concurrent with DSR and the formation of FeS. We observed variable responses in the ability of specific Fe(II) minerals to reduce Sb(V). No reduction was observed with magnetite, siderite, vivianite, or green rust. In the presence of mackinawite (FeS), however, Sb(V) was reduced to Sb(III) sulfide. These results suggest that the reduction of Sb(V) to Sb(III) is not likely under solely Fe(III)-reducing conditions, but is expected in sulfidogenic environments.

  17. Couplings between changes in the climate system and biogeochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Menon, Surabi; Denman, Kenneth L.; Brasseur , Guy; Chidthaisong, Amnat; Ciais, Philippe; Cox, Peter M.; Dickinson, Robert E.; Hauglustaine, Didier; Heinze, Christoph; Holland, Elisabeth; Jacob , Daniel; Lohmann, Ulrike; Ramachandran, Srikanthan; Leite da Silva Dias, Pedro; Wofsy, Steven C.; Zhang, Xiaoye

    2007-10-01

    The Earth's climate is determined by a number of complex connected physical, chemical and biological processes occurring in the atmosphere, land and ocean. The radiative properties of the atmosphere, a major controlling factor of the Earth's climate, are strongly affected by the biophysical state of the Earth's surface and by the atmospheric abundance of a variety of trace constituents. These constituents include long-lived greenhouse gases (LLGHGs) such as carbon dioxide (CO{sub 2}), methane (CH{sub 4}) and nitrous oxide (N{sub 2}O), as well as other radiatively active constituents such as ozone and different types of aerosol particles. The composition of the atmosphere is determined by processes such as natural and anthropogenic emissions of gases and aerosols, transport at a variety of scales, chemical and microphysical transformations, wet scavenging and surface uptake by the land and terrestrial ecosystems, and by the ocean and its ecosystems. These processes and, more generally the rates of biogeochemical cycling, are affected by climate change, and involve interactions between and within the different components of the Earth system. These interactions are generally nonlinear and may produce negative or positive feedbacks to the climate system. An important aspect of climate research is to identify potential feedbacks and assess if such feedbacks could produce large and undesired responses to perturbations resulting from human activities. Studies of past climate evolution on different time scales can elucidate mechanisms that could trigger nonlinear responses to external forcing. The purpose of this chapter is to identify the major biogeochemical feedbacks of significance to the climate system, and to assess current knowledge of their magnitudes and trends. Specifically, this chapter will examine the relationships between the physical climate system and the land surface, the carbon cycle, chemically reactive atmospheric gases and aerosol particles. It also presents the current state of knowledge on budgets of important trace gases. Large uncertainties remain in many issues discussed in this chapter, so that quantitative estimates of the importance of the coupling mechanisms discussed in the following sections are not always available. In addition, regional differences in the role of some cycles and the complex interactions between them limit our present ability to provide a simple quantitative description of the interactions between biogeochemical processes and climate change.

  18. Biogeochemistry of Dissolved Free Amino Acids in Marine Sediments.

    Science.gov (United States)

    1980-09-01

    fluoroapatite. Since only simple linear adsorption is included in the remineralization mouel. authigenic mineral formation could affect the calculated...predictions and also quite different from the ammonia profile. Authi- genic mineral formation is one possible explanation for the decreasing carbon dioxide

  19. Anthropogenic impacts on the biogeochemistry and cycling of antimony.

    Science.gov (United States)

    Shotyk, William; Krachler, Michael; Chen, Bin

    2005-01-01

    Antimony is a potentially toxic trace element with no known biological function. Antimony is commonly enriched in coals, and fossil fuel combustion appears to be the largest single source of anthropogenic Sb to the global atmosphere. Abundant in sulfide minerals, its emission to the atmosphere from anthropogenic activities is linked to the mining and metallurgy of non-ferrous metals, especially Pb, Cu, and Zn. In particular, the geochemical and mineralogical association of Sb with Pb minerals implies that, like Pb, Sb has been emitted to the environment for thousands of years because of Pb mining, smelting, and refining. In the US alone, there are more than 400 former secondary lead smelting operations and worldwide there are 133 Pb-Zn smelters in operation today. Antimony is used in creating and improving dozens of industrial and commercial materials including various alloys, ceramics, glasses, plastics, and synthetic fabrics, making waste incineration another important source of Sb to the environment. Enrichments of Sb in atmospheric aerosols, plants, soils, sediments, as well as alpine and polar snow and ice suggest that Sb contamination is extensive, but there are very few quantitative studies of the geographic extent, intensity, and chronology of this contamination. There is an urgent need to quantify the extent of human impacts and how these have changed with time. The decreasing inventories of anthropogenic Sb with time in peat cores from Switzerland and Scotland suggest that the atmospheric Sb flux may be declining, but there have been too few studies to make any general conclusions. In fact, some studies of sediments and biomonitors in central Europe show little decline in Sb concentrations during the past decades. There is an obvious need for reliable data from well dated archives such as polar snow and ice, peat bogs, and sediments. The air concentrations, extent of enrichment, particle size distribution, and rate of deposition of Sb in urban areas is cause for concern. The natural processes which controlled the Sb flux to the atmosphere in the pre-anthropogenic past are poorly understood. The cumulative amount of anthropogenic Sb in soils has not yet been quantified. The long-term fate of Sb in soils, including weathering and mobilization, has only started to be investigated. However, the limited data available suggests that, in some locations at least, anthropogenic Sb in soils may be more mobile than anthropogenic Pb. Further study of this problem is needed, as well as the chemical speciation of Sb in soil-water-plant-sediment systems, and the implications which this has for human and ecosystem health.

  20. Biogeochemistry and isotope geochemistry of a landfill leachate plume.

    Science.gov (United States)

    van Breukelen, Boris M; Röling, Wilfred F M; Groen, Jacobus; Griffioen, Jasper; van Verseveld, Henk W

    2003-09-01

    The biogeochemical processes were identified which improved the leachate composition in the flow direction of a landfill leachate plume (Banisveld, The Netherlands). Groundwater observation wells were placed at specific locations after delineating the leachate plume using geophysical tests to map subsurface conductivity. Redox processes were determined using the distribution of solid and soluble redox species, hydrogen concentrations, concentration of dissolved gases (N(2), Ar, and CH(4)), and stable isotopes (delta15N-NO(3), delta34S-SO(4), delta13C-CH(4), delta2H-CH(4), and delta13C of dissolved organic and inorganic carbon (DOC and DIC, respectively)). The combined application of these techniques improved the redox interpretation considerably. Dissolved organic carbon (DOC) decreased downstream in association with increasing delta13C-DOC values confirming the occurrence of degradation. Degradation of DOC was coupled to iron reduction inside the plume, while denitrification could be an important redox process at the top fringe of the plume. Stable carbon and hydrogen isotope signatures of methane indicated that methane was formed inside the landfill and not in the plume. Total gas pressure exceeded hydrostatic pressure in the plume, and methane seems subject to degassing. Quantitative proof for DOC degradation under iron-reducing conditions could only be obtained if the geochemical processes cation exchange and precipitation of carbonate minerals (siderite and calcite) were considered and incorporated in an inverse geochemical model of the plume. Simulation of delta13C-DIC confirmed that precipitation of carbonate minerals happened.

  1. The microbiology and biogeochemistry of the Dead Sea.

    Science.gov (United States)

    Nissenbaum, A

    1975-06-01

    The Dead Sea is a hypersaline water body. Its total dissolved salts content is on the average 322.6 gm/liter. The dominant cation is Mg (40.7 gm/liter), followed by Na (39.2 gm/liter), Ca (17 gm/liter) and K (7 gm/liter). The major anion is Cl (212 gm/liter), followed by Br (5 gm/liter); SO4 and HCO3, are very minor. The lake contains a limited variety of microorganisms and no higher organisms. The number of recorded species is very low, but the total biomass is reasonably high (about 10(5) bacteria/ml and 10(4) algal cells/ml). The indigenous flora is comprised mainly of obligate halophylic bacteria, such as the pink, pleomorphicHalobacterium sp., aSarcina-like coccus, and the facultative halophilic green alga,Dunaliella. Sulfate reducers can be isolated from bottom sediments. Recently a unique obligate magnesiophile bacteria was isolated from Dead Sea sediment. Several of the Dead Sea organisms possess unusual properties. TheHalobacterium sp. has extremely high intercellular K(+) concentration (up to 4.8M) and extraordinary specificity for K(+) over Na. TheDunaliella has very high intracellular concentration of glycerol (up to 2.1M). The microorganisms exert marked influence on some biogeochemical processes occurring in the lake, such as the control of the sulfur cycle and the formation and diagenesis of organic matter in the sediments. The Dead Sea is an excellent example of the development of two different mechanisms for adjusting to a hostile environment. The algae adjust to the high salinity by developing a mechanism for the exclusion of salts from the intracellular fluid and using glycerol for osmotic regulation. On the other hand, the bacteria adapt to the environment by adjusting their internal inorganic ionic strength, but not composition, to that of the medium. The problem of population dynamics and limiting factors for algal and bacterial productivity are discussed in view of the total absence of zooplankton and other consumers other than bacteria.

  2. Recent advances in the biogeochemistry of nitrogen in the ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; Voss, M.; Montoya, J.P.

    -scale geochemical measurements, and in- tegrative modeling (Gruber and Sarmiento, 1997; Brandes et Correspondence to: S. W. A. Naqvi (naqvi@nio.org) al., 1998; Brandes and Devol, 2002; Deutsch et al., 2004, 2007; Sigman et al., 2005; Devol et al., 2006), and conse... workshop, “Significant Processes, Observations, and Transformation in Oceanic Ni- trogen (SPOT-ON)” at the Institute for Baltic Sea Research, Warnem¨unde, Germany, from June 26 to 1 July 2005. Spon- sored by the Deutsche Forschungsgemeinschaft (DFG...

  3. Subglacial Lake Whillans microbial biogeochemistry: a synthesis of current knowledge.

    Science.gov (United States)

    Mikucki, J A; Lee, P A; Ghosh, D; Purcell, A M; Mitchell, A C; Mankoff, K D; Fisher, A T; Tulaczyk, S; Carter, S; Siegfried, M R; Fricker, H A; Hodson, T; Coenen, J; Powell, R; Scherer, R; Vick-Majors, T; Achberger, A A; Christner, B C; Tranter, M

    2016-01-28

    Liquid water occurs below glaciers and ice sheets globally, enabling the existence of an array of aquatic microbial ecosystems. In Antarctica, large subglacial lakes are present beneath hundreds to thousands of metres of ice, and scientific interest in exploring these environments has escalated over the past decade. After years of planning, the first team of scientists and engineers cleanly accessed and retrieved pristine samples from a West Antarctic subglacial lake ecosystem in January 2013. This paper reviews the findings to date on Subglacial Lake Whillans and presents new supporting data on the carbon and energy metabolism of resident microbes. The analysis of water and sediments from the lake revealed a diverse microbial community composed of bacteria and archaea that are close relatives of species known to use reduced N, S or Fe and CH4 as energy sources. The water chemistry of Subglacial Lake Whillans was dominated by weathering products from silicate minerals with a minor influence from seawater. Contributions to water chemistry from microbial sulfide oxidation and carbonation reactions were supported by genomic data. Collectively, these results provide unequivocal evidence that subglacial environments in this region of West Antarctica host active microbial ecosystems that participate in subglacial biogeochemical cycling.

  4. GROUNDWATER RADIOIODINE: PREVALENCE, BIOGEOCHEMISTRY, AND POTENTIAL REMEDIAL APPROACHES

    Energy Technology Data Exchange (ETDEWEB)

    Denham, M.; Kaplan, D.; Yeager, C.

    2009-09-23

    Iodine-129 ({sup 129}I) has not received as much attention in basic and applied research as other contaminants associated with DOE plumes. These other contaminants, such as uranium, plutonium, strontium, and technetium are more widespread and exist at more DOE facilities. Yet, at the Hanford Site and the Savannah River Site {sup 129}I occurs in groundwater at concentrations significantly above the primary drinking water standard and there is no accepted method for treating it, other than pump-and-treat systems. With the potential arrival of a 'Nuclear Renaissance', new nuclear power facilities will be creating additional {sup 129}I waste at a rate of 1 Ci/gigawatts energy produced. If all 22 proposed nuclear power facilities in the U.S. get approved, they will produce more {sup 129}I waste in seven years than presently exists at the two facilities containing the largest {sup 129}I inventories, ({approx}146 Ci {sup 129}I at the Hanford Site and the Savannah River Site). Hence, there is an important need to fully understand {sup 129}I behavior in the environment to clean up existing plumes and to support the expected future expansion of nuclear power production. {sup 129}I is among the key risk drivers at all DOE nuclear disposal facilities where {sup 129}I is buried, because of its long half-life (16 million years), high toxicity (90% of the body's iodine accumulates in the thyroid), high inventory, and perceived high mobility in the subsurface environment. Another important reason that {sup 129}I is a key risk driver is that there is the uncertainty regarding its biogeochemical fate and transport in the environment. We typically can define {sup 129}I mass balance and flux at sites, but can not accurately predict its response to changes in the environment. This uncertainty is in part responsible for the low drinking water standard, 1 pCi/L {sup 129}I, and the low permissible inventory limits (Ci) at the Savannah River Site, Hanford Site, and the former Yucca Mountain disposal facilities. The objectives of this report are to: (1) compile the background information necessary to understand behavior of {sup 129}I in the environment, (2) discuss sustainable remediation approaches to {sup 129}I contaminated groundwater, and (3) identify areas of research that will facilitate remediation of {sup 129}I contaminated areas on DOE sites. Lines of scientific inquiry that would significantly advance the goals of basic and applied research programs for accelerating {sup 129}I environmental remediation and reducing uncertainty associated with disposal of {sup 129}I waste are: (1) Evaluation of amendments or other treatment systems that can sequester subsurface groundwater {sup 129}I. (2) Develop analytical techniques for measurement of total {sup 129}I that eliminate the necessity of collecting and shipping large samples of groundwater. (3) Develop and evaluate ways to manipulate areas with organic-rich soil, such as wetlands, to maximize {sup 129}I sorption, minimizing releases during anoxic conditions. (4) Develop analytical techniques that can identify the various {sup 129}I species in the subsurface aqueous and solid phases at ambient concentrations and under ambient conditions. (5) Identify the mechanisms and factors controlling iodine-natural organic matter interactions at appropriate environmental concentrations. (6) Understand the biological processes that transform iodine species throughout different compartments of subsurface waste sites and the role that these processes have on {sup 129}I flux.

  5. Deep ocean biogeochemistry of silicic acid and nitrate

    Science.gov (United States)

    Sarmiento, J. L.; Simeon, J.; Gnanadesikan, A.; Gruber, N.; Key, R. M.; Schlitzer, R.

    2007-03-01

    Observations of silicic acid and nitrate along the lower branch of the global conveyor belt circulation show that silicic acid accumulation by diatom opal dissolution occurs at 6.4 times the rate of nitrate addition by organic matter remineralization. The export of opal and organic matter from the surface ocean occurs at a Si:N mole ratio that is much smaller than this almost everywhere (cf. Sarmiento et al., 2004). The preferential increase of silicic acid over nitrate as the deep circulation progresses from the North Atlantic to the North Pacific is generally interpreted as requiring deep dissolution of opal together with shallow remineralization of organic matter (Broecker, 1991). However, Sarmiento et al. (2004) showed that the primary reason for the low silicic acid concentration of the upper ocean is that the waters feeding the main thermocline from the surface Southern Ocean are depleted in silicic acid relative to nitrate. By implication, the same Southern Ocean processes that deplete the silicic acid in the surface Southern Ocean must also be responsible for the enhanced silicic acid concentration of the deep ocean. We use observations and results from an updated version of the adjoint model of Schlitzer (2000) to confirm that this indeed the case.

  6. Tropical forest soil microbial communities couple iron and carbon biogeochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Dubinsky, E.A.; Silver, W.L.; Firestone, M.K.

    2009-10-15

    We report that iron-reducing bacteria are primary mediators of anaerobic carbon oxidation in upland tropical soils spanning a rainfall gradient (3500 - 5000 mm yr-1) in northeast Puerto Rico. The abundant rainfall and high net primary productivity of these tropical forests provide optimal soil habitat for iron-reducing and iron-oxidizing bacteria. Spatially and temporally dynamic redox conditions make iron-transforming microbial communities central to the belowground carbon cycle in these wet tropical forests. The exceedingly high abundance of iron-reducing bacteria (up to 1.2 x 10{sup 9} cells per gram soil) indicated that they possess extensive metabolic capacity to catalyze the reduction of iron minerals. In soils from the higher rainfall sites, measured rates of ferric iron reduction could account for up to 44 % of organic carbon oxidation. Iron reducers appeared to compete with methanogens when labile carbon availability was limited. We found large numbers of bacteria that oxidize reduced iron at sites with high rates of iron reduction and large numbers of iron-reducers. the coexistence of large populations of ironreducing and iron-oxidizing bacteria is evidence for rapid iron cycling between its reduced and oxidized states, and suggests that mutualistic interactions among these bacteria ultimately fuel organic carbon oxidation and inhibit CH4 production in these upland tropical forests.

  7. Acid mine drainage biogeochemistry at Iron Mountain, California

    Directory of Open Access Journals (Sweden)

    Gihring Thomas M

    2004-06-01

    Full Text Available The Richmond Mine at Iron Mountain, Shasta County, California, USA provides an excellent opportunity to study the chemical and biological controls on acid mine drainage (AMD generation in situ, and to identify key factors controlling solution chemistry. Here we integrate four years of field-based geochemical data with 16S rRNA gene clone libraries and rRNA probe-based studies of microbial population structure, cultivation-based metabolic experiments, arsenopyrite surface colonization experiments, and results of intermediate sulfur species kinetics experiments to describe the Richmond Mine AMD system. Extremely acidic effluent (pH between 0.5 and 0.9 resulting from oxidation of approximately 1 × 105 to 2 × 105 moles pyrite/day contains up to 24 g/1 Fe, several g/1 Zn and hundreds of mg/l Cu. Geochemical conditions change markedly over time, and are reflected in changes in microbial populations. Molecular analyses of 232 small subunit ribosomal RNA (16S rRNA gene sequences from six sites during a sampling time when lower temperature (0.8 conditions predominated show the dominance of Fe-oxidizing prokaryotes such as Ferroplasma and Leptospirillum in the primary drainage communities. Leptospirillum group III accounts for the majority of Leptospirillum sequences, which we attribute to anomalous physical and geochemical regimes at that time. A couple of sites peripheral to the main drainage, "Red Pool" and a pyrite "Slump," were even higher in pH (>1 and the community compositions reflected this change in geochemical conditions. Several novel lineages were identified within the archaeal Thermoplasmatales order associated with the pyrite slump, and the Red Pool (pH 1.4 contained the only population of Acidithiobacillus. Relatively small populations of Sulfobacillus spp. and Acidithiobacillus caldus may metabolize elemental sulfur as an intermediate species in the oxidation of pyritic sulfide to sulfate. Experiments show that elemental sulfur which forms on pyrite surfaces is resistant to most oxidants; its solublization by unattached cells may indicate involvement of a microbially derived electron shuttle. The detachment of thiosulfate (S2O32- as a leaving group in pyrite oxidation should result in the formation and persistence of tetrathionate in low pH ferric iron-rich AMD solutions. However, tetrathionate is not observed. Although a S2O32--like species may form as a surface-bound intermediate, data suggest that Fe3+ oxidizes the majority of sulfur to sulfate on the surface of pyrite. This may explain why microorganisms that can utilize intermediate sulfur species are scarce compared to Fe-oxidizing taxa at the Richmond Mine site.

  8. Molecular Biogeochemistry of Modern and Ancient Marine Microbes

    Science.gov (United States)

    2010-02-01

    Oscillatoria neglecta Nostoc sp. Planktothrix agardhii Trichodesmium havanum Microcystis aeruginosa Leptolyngbya boryana Uncultured Synechocystis sp. Euglena ...Second, euglenids Euglena gracilis (Anding et al. 1971) and Astasia longa (Rohmer & Brandt 1973) and heterolobosea (Naegleria sp.; Raederstorff...Sterol biosynthesis in Euglena gracilis Z. Sterol precursors in light-grown and dark-grown Euglena gracilis Z. Eur. J. Biochem. 24, 259–263. (doi

  9. Treeline biogeochemistry and dynamics, Noatak National Preserve, northwestern Alaska

    Science.gov (United States)

    Stottlemyer, R.; Binkley, D.; Steltzer, H.; Wilson, F.H.; Galloway, J.P.

    2002-01-01

    The extensive boreal biome is little studies relative to its global importance. Its high soil moisture and low temperatures result in large below-ground reservoirs of carbon (C) and nitrogen (N). Presently, such high-latitude ecosystems are undergoing the largest temperature increases in global warming. Change in soil temperature or moisture in the large pools of soil organic matter could fundamentally change ecosystem C and N budgets. Since 1990, we have conducted treeline studies in a small (800 ha) watershed in Noatak National Preserve, northwestern Alaska. Our objectives were to (1) gain an understanding of treeline dynamics, structure, and function; and (2) examine the effects of global climate change, particularly soil temperature, moisture, and N availability, on ecosystem processes. Our intensive site studies show that the treeline has advanced into turdra during the past 150 years. Inplace and laboratory incubations indicate that soil organic-layer mineralization rates increase with a temperature change >5 degrees C. N availability was greatest in soils beneath alder and lowest beneath willow or cottongrass tussocks. Watershed output of inorganic N as NO3 was 70 percent greater than input. The high inorganic-N output likely reflects soil freeze-thaw cycles, shallow flowpaths to the stream, and low seasonal biological retention. Concentrations and flux of dissolved organic carbon (DOC) in streamwater increased during spring melt and in autumn, indicating a seasonal accumulation of soil and forest-floor DOC and a shallower flowpath for meltwater to the stream. In sum, our research suggests that treeling transitionzone processes are quite sensitive to climate change, especially those functions regulating the C and N cycles.

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

    DEFF Research Database (Denmark)

    Schippers, A.; Jørgensen, BB

    2002-01-01

    Pyrite (FeS2) and iron monosulfide (FeS) play a central role in the sulfur and iron cycles of marine sediments, They may be buried in the sediment or oxidized by O-2 after transport by bioturbation to the sediment surface. FeS2 and FeS may also be oxidized within the anoxic sediment in which NO3......-, Fe(III) oxides, or MnO2 are available as potential electron acceptors. In chemical experiments, FeS2 and FeS were oxidized by MnO2 but not with NO3- or amorphous Fe(III) oxide (Schippers and Jørgensen, 2001). Here we also show that in experiments with anoxic sediment slurries, a dissolution of tracer......-marked (FeS2)-Fe-55 occurred with MnO2 but not with NO3- or amorphous Fe(III) oxide as electron acceptor. To study a thermodynamically possible anaerobic microbial FeS, and FeS oxidation with NO3- or amorphous Fe(III) oxide as electron acceptor, more than 300 assays were inoculated with material from several...

  11. Microbial ecology and biogeochemistry of continental Antarctic soils

    Directory of Open Access Journals (Sweden)

    Don A Cowan

    2014-04-01

    Full Text Available The Antarctica Dry Valleys are regarded as the coldest hyperarid desert system on Earth. While a wide variety of environmental stressors including very low minimum temperatures, frequent freeze-thaw cycles and low water availability impose severe limitations to life, suitable niches for abundant microbial colonization exist. Antarctic desert soils contain much higher levels of microbial diversity than previously thought. Edaphic niches, including cryptic and refuge habitats, microbial mats and permafrost soils all harbour microbial communities which drive key biogeochemical cycling processes. For example, lithobionts (hypoliths and endoliths possess a genetic capacity for nitrogen and carbon cycling, polymer degradation and other system processes. Nitrogen fixation rates of hypoliths, as assessed through acetylene reduction assays, suggest that these communities are a significant input source for nitrogen into these oligotrophic soils. Here we review aspects of microbial diversity in Antarctic soils with an emphasis on functionality and capacity. We assess current knowledge regarding adaptations to Antarctic soil environments and highlight the current threats to Antarctic desert soil communities.

  12. The integral role of iron in ocean biogeochemistry

    Science.gov (United States)

    Tagliabue, Alessandro; Bowie, Andrew R.; Boyd, Philip W.; Buck, Kristen N.; Johnson, Kenneth S.; Saito, Mak A.

    2017-03-01

    The micronutrient iron is now recognized to be important in regulating the magnitude and dynamics of ocean primary productivity, making it an integral component of the ocean’s biogeochemical cycles. In this Review, we discuss how a recent increase in observational data for this trace metal has challenged the prevailing view of the ocean iron cycle. Instead of focusing on dust as the major iron source and emphasizing iron’s tight biogeochemical coupling to major nutrients, a more complex and diverse picture of the sources of iron, its cycling processes and intricate linkages with the ocean carbon and nitrogen cycles has emerged.

  13. Hydrothermal impacts on trace element and isotope ocean biogeochemistry

    Science.gov (United States)

    German, C. R.; Casciotti, K. A.; Dutay, J.-C.; Heimbürger, L. E.; Jenkins, W. J.; Measures, C. I.; Mills, R. A.; Obata, H.; Schlitzer, R.; Tagliabue, A.; Turner, D. R.; Whitby, H.

    2016-11-01

    Hydrothermal activity occurs in all ocean basins, releasing high concentrations of key trace elements and isotopes (TEIs) into the oceans. Importantly, the calculated rate of entrainment of the entire ocean volume through turbulently mixing buoyant hydrothermal plumes is so vigorous as to be comparable to that of deep-ocean thermohaline circulation. Consequently, biogeochemical processes active within deep-ocean hydrothermal plumes have long been known to have the potential to impact global-scale biogeochemical cycles. More recently, new results from GEOTRACES have revealed that plumes rich in dissolved Fe, an important micronutrient that is limiting to productivity in some areas, are widespread above mid-ocean ridges and extend out into the deep-ocean interior. While Fe is only one element among the full suite of TEIs of interest to GEOTRACES, these preliminary results are important because they illustrate how inputs from seafloor venting might impact the global biogeochemical budgets of many other TEIs. To determine the global impact of seafloor venting, however, requires two key questions to be addressed: (i) What processes are active close to vent sites that regulate the initial high-temperature hydrothermal fluxes for the full suite of TEIs that are dispersed through non-buoyant hydrothermal plumes? (ii) How do those processes vary, globally, in response to changing geologic settings at the seafloor and/or the geochemistry of the overlying ocean water? In this paper, we review key findings from recent work in this realm, highlight a series of key hypotheses arising from that research and propose a series of new GEOTRACES modelling, section and process studies that could be implemented, nationally and internationally, to address these issues. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.

  14. Efeitos das mudanças do uso da terra na biogeoquímica dos corpos d'água da bacia do rio Ji-Paraná, Rondônia Effects of land use changes in the biogeochemistry of fluvial systems of the Ji-Paraná river basin, Rondônia

    Directory of Open Access Journals (Sweden)

    Alex Vladimir Krusche

    2005-06-01

    Full Text Available Este trabalho discute os efeitos das mudanças do uso do solo na biogequímica dos rios da bacia de drenagem do rio Ji-Paraná (Rondônia. Nesta região, a distribuição espacial do desmatamento e das propriedades do solo resultam em sinais diferentes, possibilitando a divisão dos sistemas fluviais em três grupos: rios com águas pobres em íons e baixo impacto; rios com conteúdo iônico intermediário e impacto médio e rios com elevados conteúdo iônico e impacto antropogênico. As características biogeoquímicas dos rios têm relação significativa com a área de pasto, melhor parâmetro para prever a condutividade elétrica (r² = 0,87 e as concentrações de sódio (r² = 0,75, cloreto (r² = 0,69, potássio (r² = 0,63, fosfato (r² = 0.78, nitrogênio inorgânico (r² = 0.52, carbono inorgânico (r² = 0.81 e carbono orgânico (rain ² = 0.51 dissolvidos. Cálcio e magnésio tiveram sua variância explicada pelas características do solo e pastagem. Nossos resultados indicam que as mudanças observadas na micro-escala constituem "sinais biogeoquímicos" gerados pelo processamento do material nas margens dos rios. A medida em que os rios evoluem para ordens superiores, os sinais persistentes nos canais fluviais estão mais associdados às características da bacia de drenagem (solos e uso da terra. Apesar dos efeitos das mudanças observadas no uso do solo não serem ainda detectáveis na macro-escala (bacia amazônica, a disrupção da estrutura e funcionamento dos ecossistemas é detectável nas micro e meso escalas, com alterações significativas na ciclagem de nutrientes nos ecossistemas fluviais.In this article we present the results of the effects of land use change on the river biogeochemistry of the Ji-Paraná basin (Rondônia. In this region, the spatial distribution of deforestation and soil properties result in different biogeochemical signals, allowing the division of the fluvial systems into three groups: rivers with

  15. Seasonally varying nitrogen isotope biogeochemistry of particulate organic matter in Lake Kinneret, Israel

    Digital Repository Service at National Institute of Oceanography (India)

    Hadas, O.; Altabet, M.A.; Agnihotri, R.

    typically takes place in late April and May after the spring bloom when microbial degradation of abundant organic matter (OM) first consumed available O 2 and then used NO 3 - as an oxidant (electron acceptor). For example between March and June 2004... consuming NH 4 + and producing NO 3 - . In winter 2004, the nitrification period was not as well sampled, but stable post-nitrification values for δ 15 NO 3 - were also observed in the epilimnion but were ~5‰ higher than in 2005. It should be noted...

  16. Relating the Biogeochemistries of Zinc, Cobalt, and Phosphorus to Phytoplankton Activities in the Sea

    Science.gov (United States)

    2006-06-01

    meant a lot to me. What a nightmare beginning it was.. .the fateful Weatherbird cruise of losing equipment, breaking back-up equipment, breathing diesel ...approximately 15 m depth directly into an acid-washed HDPE carboy, housed in a trace-metal free bubble constructed of a HEPA filter and plastic sheeting...coccolithophores (Siegel et al., 1990). A springtime survey of phytoplankton showed that large phytoplankton (ultra & nano , cryptophytes, and coccolithophores) had

  17. Quantifying peat carbon accumulation in Alaska using a process-based biogeochemistry model

    Science.gov (United States)

    Wang, Sirui; Zhuang, Qianlai; Yu, Zicheng; Bridgham, Scott; Keller, Jason K.

    2016-08-01

    This study uses an integrated modeling framework that couples the dynamics of hydrology, soil thermal regime, and ecosystem carbon and nitrogen to quantify the long-term peat carbon accumulation in Alaska during the Holocene. Modeled hydrology, soil thermal regime, carbon pools and fluxes, and methane emissions are evaluated using observation data at several peatland sites in Minnesota, Alaska, and Canada. The model is then applied for a 10,000 year (15 ka to 5 ka; 1 ka = 1000 cal years before present) simulation at four peatland sites. We find that model simulations match the observed carbon accumulation rates at fen sites during the Holocene (R2 = 0.88, 0.87, 0.38, and -0.05 using comparisons in 500 year bins). The simulated (2.04 m) and observed peat depths (on average 1.98 m) were also compared well (R2 = 0.91). The early Holocene carbon accumulation rates, especially during the Holocene thermal maximum (HTM) (35.9 g C m- 2 yr- 1), are estimated up to 6 times higher than the rest of the Holocene (6.5 g C m- 2 yr- 1). Our analysis suggests that high summer temperature and the lengthened growing season resulted from the elevated insolation seasonality, along with wetter-than-before conditions might be major factors causing the rapid carbon accumulation in Alaska during the HTM. Our sensitivity tests indicate that, apart from climate, initial water table depth and vegetation canopy are major drivers to the estimated peat carbon accumulation. When the modeling framework is evaluated for various peatland types in the Arctic, it can quantify peatland carbon accumulation at regional scales.

  18. Metal biogeochemistry in surface-water systems; a review of principles and concepts

    Science.gov (United States)

    Elder, John F.

    1988-01-01

    Metals are ubiquitous in natural surface-water systems, both as dissolved constituents and as particulate constituents. Although concentrations of many metals are generally very low (hence the common term 'trace metals'), their effects on the water quality and the biota of surfacewater systems are likely to be substantial. Biogeochemical partitioning of metals results in a diversity of forms, including hydrated or 'free' ions, colloids, precipitates, adsorbed phases, and various coordination complexes with dissolved organic and inorganic ligands. Much research has been dedicated to answering questions about the complexities of metal behavior and effects in aquatic systems. Voluminous literature on the subject has been produced. This paper synthesizes the findings of aquatic metal studies and describes some general concepts that emerge from such a synthesis. Emphasis is on sources, occurrence, partitioning, transport, and biological interactions of metals in freshwater systems of North America. Biological interactions, in this case, refer to bioavailability, effects of metals on ecological characteristics and functions of aquatic systems, and roles of biota in controlling metal partitioning. This discussion is devoted primarily to the elements aluminum, arsenic, cadmium, chromium, copper, iron, lead, manganese, mercury, nickel, and zinc and secondarily to cobalt, molybdenum, selenium, silver, and vanadium. Sources of these elements are both natural and anthropogenic. Significant anthropogenic sources are atmospheric deposition, discharges of municipal and industrial wastes, mine drainage, and urban and agricultural runoff. Biogeochemical partitioning of metals is controlled by various characteristics of the water and sediments in which the metals are found. Among the most important controlling factors are pH, oxidation-reduction potential, hydrologic features, sediment grain size, and the existence and nature of clay minerals, organic matter, and hydrous oxides of manganese and iron. Partitioning is also controlled by biological processes that provide mechanisms for detoxification of metals and for enhanced uptake of nutritive metals. Partitioning is important largely because availability to biota is highly variable among different phases. Hence, accumulation in biological tissues and toxicity of an element are dependent not only on total concentration of the element but also on the factors that control partitioning.

  19. THE BIOGEOCHEMISTRY OF PHOTOSYNTHETIC PIGMENTS IN THE JIULONG RIVER ESTUARY AND WESTERN XIAMEN BAY

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    High performance liquid chromatography (HPLC) analysis of photosynthetic pigments in samples from Western Xiamen Bay and the Jiulong River Estuary showed that their major carotenoids were fucoxanthin, peridinin, zeaxanthin, violaxanthin, and diadinoxanthin. Diatoms dominated in the spring bloom, dinoflagellates in summer. Violaxanthin and chlorophyll b indicated the appearance of chrysophytes and green algae, most of which were freshwater species. The high phytoplankton biomass region was located at the inner part of the bay. Diatoms and dinoflagellates dominated phytoplankton communities, contributing to over 50% of total biomass. All the main diagnostic carotenoids were significantly (P<0.01) correlated negatively to dissolved inorganic phosphorus, suggesting that they were limited by phosphorus. The high negative linear relationship (P<0.0001) between dissolved inorganic phosphorus and peridinin (dinoflagellates indicator) implied the potential of dissolved inorganic phosphorus for triggering red tide events in this region.

  20. THE BIOGEOCHEMISTRY OF PHOTOSYNTHETIC PIGMENTS IN THE JIULONG RIVER ESTUARY AND WESTERN XIAMEN BAY

    Institute of Scientific and Technical Information of China (English)

    徐立; 洪华生; 王海黎; 陈伟琪

    2001-01-01

    High performance liquid chromatography (HPLC) analysis of photosynthetic pigments in samples from Western Xiamen Bay and the Jiulong River Estuary showed that their major carotenoids were fucoxnnthin, peridinin, zeaxanthin, violaxanthin, and diadinoxnnthin. Diatoms dominated in the spring bloom, dinotlagellates in summer. Violaxanthin and chlorophyll b indicated the appearance of chrysophytes and green algae, most of which were freshwater species. The high phytoplankton biomass re-gion was located at the inner part of the bay. Diatoms and dinoilagellates dominated phytoplankton com-munities, contributing to over 50% of total biomass. All the main diagnostic carotenoids were significantly (P < 0.01 ) correlated negatively to dissolved inorganic phosphorus, suggesting that they were limited by phosphorus. The high negative linear relationship ( P < 0. 0001 ) between dissolved inorganic phosphorus and peridinin (dinoflagellates indicator) implied the potential of dissolved inorganic phosphorus for trig-gefing red tide events in this region.

  1. Porewater biogeochemistry and soil metabolism in dwarf red mangrove habitats (Twin Cays, Belize)

    Science.gov (United States)

    Lee, R.Y.; Porubsky, W.P.; Feller, Ilka C.; McKee, K.L.; Joye, S.B.

    2008-01-01

    Seasonal variability in biogeochemical signatures was used to elucidate the dominant pathways of soil microbial metabolism and elemental cycling in an oligotrophic mangrove system. Three interior dwarf mangrove habitats (Twin Cays, Belize) where surface soils were overlain by microbial mats were sampled during wet and dry periods of the year. Porewater equilibration meters and standard biogeochemical methods provided steady-state porewater profiles of pH, chloride, sulfate, sulfide, ammonium, nitrate/nitrite, phosphate, dissolved organic carbon, nitrogen, and phosphorus, reduced iron and manganese, dissolved inorganic carbon, methane and nitrous oxide. During the wet season, the salinity of overlying pond water and shallow porewaters decreased. Increased rainwater infiltration through soils combined with higher tidal heights appeared to result in increased organic carbon inventories and more reducing soil porewaters. During the dry season, evaporation increased both surface water and porewater salinities, while lower tidal heights resulted in less reduced soil porewaters. Rainfall strongly influenced inventories of dissolved organic carbon and nitrogen, possibly due to more rapid decay of mangrove litter during the wet season. During both times of year, high concentrations of reduced metabolites accumulated at depth, indicating substantial rates of organic matter mineralization coupled primarily to sulfate reduction. Nitrous oxide and methane concentrations were supersaturated indicating considerable rates of nitrification and/or incomplete denitrification and methanogenesis, respectively. More reducing soil conditions during the wet season promoted the production of reduced manganese. Contemporaneous activity of sulfate reduction and methanogenesis was likely fueled by the presence of noncompetitive substrates. The findings indicate that these interior dwarf areas are unique sites of nutrient and energy regeneration and may be critical to the overall persistence and productivity of mangrove-dominated islands in oligotrophic settings. ?? 2008 Springer Science+Business Media B.V.

  2. Biogeochemistry of lead in the eastern Arabian Sea and western Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Rejomon, G.; DineshKumar, P.K.; Bahulayan, N.

    representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims... of Bengal is found to vary spatially and temporally due to significant differences in its interaction with anthropogenic particles transported through the atmosphere to its surface wa- ters and followed by sinking into the subsurface waters. This can happen...

  3. Emerging concepts on microbial processes in the bathypelagic ocean - ecology, biogeochemistry, and genomics

    Science.gov (United States)

    Nagata, Toshi; Tamburini, Christian; Arístegui, Javier; Baltar, Federico; Bochdansky, Alexander B.; Fonda-Umani, Serena; Fukuda, Hideki; Gogou, Alexandra; Hansell, Dennis A.; Hansman, Roberta L.; Herndl, Gerhard J.; Panagiotopoulos, Christos; Reinthaler, Thomas; Sohrin, Rumi; Verdugo, Pedro; Yamada, Namiha; Yamashita, Youhei; Yokokawa, Taichi; Bartlett, Douglas H.

    2010-08-01

    This paper synthesizes recent findings regarding microbial distributions and processes in the bathypelagic ocean (depth >1000 m). Abundance, production and respiration of prokaryotes reflect supplies of particulate and dissolved organic matter to the bathypelagic zone. Better resolution of carbon fluxes mediated by deep microbes requires further testing on the validity of conversion factors. Archaea, especially marine Crenarchaeota Group I, are abundant in deep waters where they can fix dissolved inorganic carbon. Viruses appear to be important in the microbial loop in deep waters, displaying remarkably high virus to prokaryote abundance ratios in some oceanic regions. Sequencing of 18S rRNA genes revealed a tremendous diversity of small-sized protists in bathypelagic waters. Abundances of heterotrophic nanoflagellates (HNF) and ciliates decrease with depth more steeply than prokaryotes; nonetheless, data indicated that HNF consumed half of prokaryote production in the bathypelagic zone. Aggregates are important habitats for deep-water microbes, which produce more extracellular enzymes (on a per-cell basis) than surface communities. The theory of marine gel formation provides a framework to unravel complex interactions between microbes and organic polymers. Recent data on the effects of hydrostatic pressure on microbial activities indicate that bathypelagic microbial activity is generally higher under in situ pressure conditions than at atmospheric pressures. High-throughput sequencing of 16S rRNA genes revealed a remarkable diversity of Bacteria in the bathypelagic ocean. Metagenomics and comparative genomics of piezophiles reveal not only the high diversity of deep sea microbes but also specific functional attributes of these piezophilic microbes, interpreted as an adaptation to the deep water environment. Taken together, the data compiled on bathypelagic microbes indicate that, despite high-pressure and low-temperature conditions, microbes in the bathypelagic ocean dynamically interact with complex mixtures of organic matter, responding to changes in the ocean's biogeochemical state.

  4. The Biogeochemistry beneath the Whillans Ice Stream, West Antarctica: Evidence for a Chemoautotrophically Driven Ecosystem

    Science.gov (United States)

    Purcell, A.; Mikucki, J.; Achberger, A.; Christner, B. C.; Michaud, A. B.; Mitchell, A. C.; Priscu, J. C.; Skidmore, M. L.; Vick-Majors, T.

    2015-12-01

    Antarctic sub ice environments represent some of the most understudied microbial ecosystems on Earth. The Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project recently sampled sediments and water from Subglacial Lake Whillans (SLW) and its hydrologically connected grounding zone where this lake system empties beneath the Ross Ice Shelf. Here we highlight findings on the diversity and metabolic capabilities of the microbial community detected in these samples. We utilized a hot water drill with a novel filtration and UV treatment system to insure that our entry and sampling did not contaminate our samples or the pristine subglacial ecosystem. Geochemical and microbiological data suggests the water column hosts an active microbial community sustained by the production of fixed carbon from chemosynthesis with energy derived from reduced nitrogen, sulfur, and iron compounds. These energy sources appear to be influenced by bedrock weathering at the sediment surface. For example, dominant 16S rRNA gene phylotypes in the water column suggest ammonia oxidation as a potential source of chemoautotrophic energy. While in the SLW surficial sediments, diversity analysis of functional genes involved in both sulfur oxidation and sulfate reduction (aprA, dsrA, and rdsrA), aprA gene abundance, and 16S rRNA gene analysis indicate that sulfur-oxidizing microbes are dominant. These preliminary results represents the first data on microbial community structure and function from an Antarctic subglacial lake and its grounding zone.

  5. Modelling potential impacts of bottom trawl fisheries on soft sediment biogeochemistry in the North Sea†

    Directory of Open Access Journals (Sweden)

    Parker Ruth

    2001-12-01

    Full Text Available Bottom trawling causes physical disturbance to sediments particularly in shelf areas. The disturbance due to trawling is most significant in deeper areas with softer sediments where levels of natural disturbance due to wave and tidal action are low. In heavily fished areas, trawls may impact the same area of seabed more than four times per year. A single pass of a beam trawl, the heaviest gear routinely used in shelf sea fisheries, can kill 5–65% of the resident fauna and mix the top few cm of sediment. We expect that sediment community function, carbon mineralisation and biogeochemical fluxes will be strongly affected by trawling activity because the physical effects of trawling are equivalent to those of an extreme bioturbator, and yet, unlike bioturbating macrofauna, trawling does not directly contribute to community metabolism. We used an existing box-model of a generalised soft sediment system to examine the effects of trawling disturbance on carbon mineralisation and chemical concentrations. We contrasted the effects of a natural scenario, where bioturbation is a function of macrobenthos biomass, with an anthropogenic impact scenario where physical disturbance results from trawling rather than the action of bioturbating macrofauna. Simulation results suggest that the effects of low levels of trawling disturbance will be similar to those of natural bioturbators but that high levels of trawling disturbance prevent the modelled system from reaching equilibrium due to large carbon fluxes between oxic and anoxic carbon compartments. The presence of macrobenthos in the natural disturbance scenario allowed sediment chemical storage and fluxes to reach equilibrium. This is because the macrobenthos are important carbon consumers in the system whose presence reduces the magnitude of available carbon fluxes. In soft sediment systems, where the level physical disturbance due to waves and tides is low, model results suggest that intensive trawling disturbance could cause large fluctuations in benthic chemical fluxes and storage.

  6. Regional Application of an Ecosystem Production Model for Studies of Biogeochemistry in the...

    Science.gov (United States)

    Potter, C. S.; Klooster, S.; Brooks, V.; Peterson, David L. (Technical Monitor)

    1997-01-01

    The degree to which primary production, soil carbon, and trace gas fluxes in tropical forests of the Amazon are limited by moisture availability and other environmental factors was examined using an ecosystem modeling application for the country of Brazil. A regional geographic information system (GIS) serves as the data source of climate drivers, satellite images, land cover, and soil properties for input to the NASA Ames-CASA (Carnegie-Ames-Stanford Approach) model over a 8-km grid resolution. Simulation results supports the hypothesis that net primary production (NPP) is limited by cloud interception of solar radiation over the humid northwestern portion of the region. Peak annual rates for NPP of nearly 1.4 kg C m-2yr -1are localized in the seasonally dry eastern Amazon in areas that we assume are primarily deep-rooted evergreen forest cover. Regional effects of forest conversion on NPP and soil carbon content are indicated in the model results, especially in seasonally dry areas. Comparison of model flux predictions along selected eco-climatic transects reveal moisture, soil, and land use controls on gradients of ecosystem production and soil trace gas emissions (CO2, N2O, and NO). These results are used to formulate a series of research hypotheses for testing in the next phase of regional modeling, which includes recalibration of the light-use efficiency term in CASA using field measurements of NPP, and refinements of vegetation index and soil property (texture and potential rooting depth) maps for the region.

  7. Stable isotope biogeochemistry of seabird guano fertilization: results from growth chamber studies with maize (Zea mays.

    Directory of Open Access Journals (Sweden)

    Paul Szpak

    Full Text Available BACKGROUND: Stable isotope analysis is being utilized with increasing regularity to examine a wide range of issues (diet, habitat use, migration in ecology, geology, archaeology, and related disciplines. A crucial component to these studies is a thorough understanding of the range and causes of baseline isotopic variation, which is relatively poorly understood for nitrogen (δ(15N. Animal excrement is known to impact plant δ(15N values, but the effects of seabird guano have not been systematically studied from an agricultural or horticultural standpoint. METHODOLOGY/PRINCIPAL FINDINGS: This paper presents isotopic (δ(13C and δ(15N and vital data for maize (Zea mays fertilized with Peruvian seabird guano under controlled conditions. The level of (15N enrichment in fertilized plants is very large, with δ(15N values ranging between 25.5 and 44.7‰ depending on the tissue and amount of fertilizer applied; comparatively, control plant δ(15N values ranged between -0.3 and 5.7‰. Intraplant and temporal variability in δ(15N values were large, particularly for the guano-fertilized plants, which can be attributed to changes in the availability of guano-derived N over time, and the reliance of stored vs. absorbed N. Plant δ(13C values were not significantly impacted by guano fertilization. High concentrations of seabird guano inhibited maize germination and maize growth. Moreover, high levels of seabird guano greatly impacted the N metabolism of the plants, resulting in significantly higher tissue N content, particularly in the stalk. CONCLUSIONS/SIGNIFICANCE: The results presented in this study demonstrate the very large impact of seabird guano on maize δ(15N values. The use of seabird guano as a fertilizer can thus be traced using stable isotope analysis in food chemistry applications (certification of organic inputs. Furthermore, the fertilization of maize with seabird guano creates an isotopic signature very similar to a high-trophic level marine resource, which must be considered when interpreting isotopic data from archaeological material.

  8. Iron from melting glaciers fuels the phytoplankton blooms in Amundsen Sea (Southern Ocean) : Iron biogeochemistry

    NARCIS (Netherlands)

    Gerringa, Loes J. A.; Alderkamp, Anne-Carlijn; Laan, Patrick; Thuroczy, Charles-Edouard; De Baar, Hein J. W.; Mills, Matthew M.; van Dijken, Gert L.; van Haren, Hans; Arrigo, Kevin R.

    2012-01-01

    Dissolved iron (DFe) and total dissolvable Fe (TDFe) were measured in January-February 2009 in Pine Island Bay, as well as in the Pine Island and Amundsen polynyas (Amundsen Sea, Southern Ocean). Iron (Fe) has been shown to be a limiting nutrient for phytoplankton growth, even in the productive cont

  9. Arabian Sea Biogeochemistry from 27 August 1994 to 19 December 1994 (NODC Accession 0000064)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Arabesque was a multidisciplinary oceanographic research project focused on the Arabian Sea and Northwest Indian Ocean during the monsoon and intermonsoon season in...

  10. Nutrient biogeochemistry of the eastern Arabian Sea during the southwest monsoon retreat

    Digital Repository Service at National Institute of Oceanography (India)

    George, R.; Muraleedharan, K.R.; Martin, G.D.; Sabu, P.; Gerson, V.J.; Dineshkumar, P.K.; Nair, S.M.; Chandramohanakumar, N.; Nair, K.K.C.

    et al. 2000). In this region, upwelling is driven by wind-forced Ekman transport away from the shore and the strength of the alongshore wind stress modulates the coastal divergence and hence the input of cold upwelled water over the shelf (Shetye et... al. 1990). A strengthening of the alongshore wind stress enhances upwelling and results in lower surface temperature and high concentration of nutrients over the shelf region. This wind-driven coastal upwelling phenomenon provides the nutrients...

  11. Occurrence of cyanobacteria - diatom symbiosis in the Bay of Bengal: Implications in biogeochemistry

    Digital Repository Service at National Institute of Oceanography (India)

    Kulkarni, V.V.; Chitari, R.R.; Narale, D.D.; Patil, J.S.; Anil, A.C.

    stream_size 7886 stream_content_type text/plain stream_name Curr_Sci_99_736.pdf.txt stream_source_info Curr_Sci_99_736.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 SCIENTIFIC CORRESPONDENCE..., New York, 1950, vol. 19, p. 643. 24. Garg, A., Taiwania, 2009, 54, 122–133. ACKNOWLEDGEMENTS. I thank DST, New Delhi for providing funds to carry out this work and the Directors, National Botani- cal Research Institute, Lucknow and Botani- cal...

  12. Mixing and its effects on biogeochemistry in the persistently stratified, deep, tropical Lake Matano, Indonesia

    DEFF Research Database (Denmark)

    Katsev, Sergei; Crowe, Sean; Mucci, Alfonso

    2010-01-01

    (-2) m(2) s(-1)). The estimated timescale of water renewal in the monimolimnion is several hundred years. Intense evaporation depletes the surface mixed layer of O-16 and H-1 isotopes, making it isotopically heavier. The lake waters become progressively isotopically lighter with depth, and the isotopic...... composition in the deep waters is close to those of the ground and tributary waters. The vertical distribution of K-z is used in a biogeochemical reaction-transport model. We show that, outside of a narrow thermocline region, the vertical distributions of dissolved oxygen, iron, methane, and phosphorus...

  13. Acetylene Fermentation: Relevance to Primordial Biogeochemistry and the Search for Life in the Outer Solar System

    Science.gov (United States)

    Oremland, R. S.; Baesman, S. M.; Miller, L. G.

    2013-12-01

    Acetylene is a highly reactive component of planet(oid)s with anoxic, methane-rich atmospheres, such as Jupiter, Saturn, Titan, and perhaps the primordial Earth. Included in this group is Enceladus, although it is not clear if the acetylene detected within its jets by Cassini was formed by photolysis of methane, from thermo-catalysis of organic matter in the orb's interior, or a fragmentation artifact of the mass spectrum of a larger hydrocarbon. Acetylene inhibits many microbial processes (e.g., methanogenesis, methane oxidation, hydrogen metabolism, denitrification) yet a number of anaerobes can use it as a carbon and energy source to support growth. The best studied is Pelobacter acetylenicus, which carries out a two-step reaction involving the enzymes acetylene hydratase and acetaldehyde dismutase. The former, a low potential W-containing enzyme, forms acetaldehyde while the latter produces ethanol and acetate. Metabolism of acetylene by mixed microbial communities (sediments and/or enrichment cultures) produces these intermediates, and when coupled with sulfate-reduction or methanogenesis respectively forms CO2 or an equal mixtures of CO2 plus CH4. It is not inconceivable that such an anaerobic, microbial food chain could exist in the waters beneath the ice cap of Enceladus, Titan, or even in the mesothermal atmospheric regions of the gas giants. Detection of the identified intermediate products of acetylene fermentation, namely acetaldehyde, ethanol, acetate and formate in the atmospheres of these planet(oid)s would constitute evidence for a microbial life signature. This evidence would be strongly reinforced if a stable carbon isotope fractionation was identified as well, whereby the products of acetylene fermentation were enriched in 12C relative to 13C (i.e., had a lighter δ13C signal) when compared to that of the starting acetylene. The most practical target to test this hypothesis would be Enceladus (if the detected acetylene is shown to be a real presence in the jet vapors) owing to the relative ease of sample collection and analysis either in future flybys or lander/collector missions.

  14. Contribution of riverine nutrients to the silicon biogeochemistry of the global ocean – a model study

    Directory of Open Access Journals (Sweden)

    C. Y. Bernard

    2011-03-01

    Full Text Available Continental shelf seas are known to support a large fraction of the global primary production. Yet, they are mostly ignored or neglected in global biogeochemical models. A number of processes that control the transfer of dissolved nutrients from rivers to the open ocean remain poorly understood. This applies in particular to dissolved silica which drives the growth of diatoms that form a large part of the phytoplankton biomass and are thus an important contributor to export production of carbon.

    Here, the representation of the biogeochemical cycling along continents is improved by coupling a high resolution database of riverine fluxes of nutrients to the global biogeochemical ocean general circulation model HAMOCC5-OM. Focusing on silicon (Si, but including the whole suite of nutrients – carbon (C, nitrogen (N and phosphorus (P in various forms – inputs are implemented in the model at coastal coupling points using the COSCAT global database of 156 mega-river-ensemble catchments from Meybeck et al. (2006. The catchments connect to the ocean through coastal segments according to three sets of criteria: natural limits, continental shelf topography, and geophysical dynamics.

    According to the model the largest effects on nutrient concentrations occur in hot spots such as the Amazon plume, the Arctic – with high nutrient inputs in relation to its total volume, and areas that encounter the largest increase in human activity, e.g., Southern Asia.

  15. Contribution of riverine nutrients to the silicon biogeochemistry of the global ocean – a model study

    Directory of Open Access Journals (Sweden)

    C. Y. Bernard

    2009-01-01

    Full Text Available Continental shelf seas are known to support a large fraction of the global primary production. Yet, continental shelf areas are mostly ignored or neglected in global biogeochemical models. A number of processes that control the transfer of dissolved nutrients from river to the open ocean remain poorly understood. This applies in particular to dissolved silica which drives the growth of diatoms that form a large part of the phytoplankton biomass and are thus an important contributor to export production of carbon.

    Here, the representation of the biogeochemical state along continents is improved by coupling a high resolution database of riverine fluxes of nutrients to the global biogeochemical ocean general circulation model MPI-OM/HAMOCC5. Focusing on silicon (Si, but including the whole suite of nutrients – carbon (C, nitrogen (N and phosphorus (P in various forms – inputs are implemented in the model at coastal coupling points using the COSCAT global database of 156 mega-river-ensemble catchments from Meybeck et al. (2006. The catchments connect to the ocean through coastal segments according to three sets of criteria: natural limits, continental shelf topography, and geophysical dynamics.

    According to the model the largest effects on nutrient concentrations occur in hot spots such as the Amazon plume, the Arctic – with high nutrient inputs in relation to its total volume, and areas that encounter the largest increase in human activity, e.g., Southern Asia.

  16. A general mathematical framework for representing soil organic matter dynamics in biogeochemistry models

    Science.gov (United States)

    Sierra, C. A.; Mueller, M.

    2013-12-01

    Recent work have highlighted the importance of nonlinear interactions in representing the decomposition of soil organic matter (SOM). It is unclear however how to integrate these concepts into larger biogeochemical models or into a more general mathematical description of the decomposition process. Here we present a mathematical framework that generalizes both previous decomposition models and recent ideas about nonlinear microbial interactions. The framework is based on a set of four basic principles: 1) mass balance, 2) heterogeneity in the decomposability of SOM, 3) transformations in the decomposability of SOM over time, 4) energy limitation of decomposers. This framework generalizes a large majority of SOM decomposition models proposed to date. We illustrate the application of this framework to the development of a continuous model that includes the ideas in the Dual Arrhenius Michaelis-Menten Model (DAMM) for explicitly representing temperature-moisture limitations of enzyme activity in the decomposition of heterogenous substrates.

  17. Biogeochemistry of the MAximum TURbidity Zone of Estuaries (MATURE): some conclusions

    NARCIS (Netherlands)

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

    1999-01-01

    In this paper, we give a short overview of the activities and main results of the MAximum TURbidity Zone of Estuaries (MATURE) project. Three estuaries (Elbe, Schelde and Gironde) have been sampled intensively during a joint 1-week campaign in both 1993 and 1994. We introduce the publicly available

  18. Climate change in Brazil: perspective on the biogeochemistry of inland waters.

    Science.gov (United States)

    Roland, F; Huszar, V L M; Farjalla, Vf; Enrich-Prast, A; Amado, A M; Ometto, J P H B

    2012-08-01

    Although only a small amount of the Earth's water exists as continental surface water bodies, this compartment plays an important role in the biogeochemical cycles connecting the land to the atmosphere. The territory of Brazil encompasses a dense river net and enormous number of shallow lakes. Human actions have been heavily influenced by the inland waters across the country. Both biodiversity and processes in the water are strongly driven by seasonal fluvial forces and/or precipitation. These macro drivers are sensitive to climate changes. In addition to their crucial importance to humans, inland waters are extremely rich ecosystems, harboring high biodiversity, promoting landscape equilibrium (connecting ecosystems, maintaining animal and plant flows in the landscape, and transferring mass, nutrients and inocula), and controlling regional climates through hydrological-cycle feedback. In this contribution, we describe the aquatic ecological responses to climate change in a conceptual perspective, and we then analyze the possible climate-change scenarios in different regions in Brazil. We also indentify some potential biogeochemical signals in running waters, natural lakes and man-made impoundments. The possible future changes in climate and aquatic ecosystems in Brazil are highly uncertain. Inland waters are pressured by local environmental changes because of land uses, landscape fragmentation, damming and diversion of water bodies, urbanization, wastewater load, and level of pollutants can alter biogeochemical patterns in inland waters over a shorter term than can climate changes. In fact, many intense environmental changes may enhance the effects of changes in climate. Therefore, the maintenance of key elements within the landscape and avoiding extreme perturbation in the systems are urgent to maintain the sustainability of Brazilian inland waters, in order to prevent more catastrophic future events.

  19. Biogeochemistry of dissolved organic matter in an anoxic intertidal creek bank

    Science.gov (United States)

    Seidel, Michael; Beck, Melanie; Riedel, Thomas; Waska, Hannelore; Suryaputra, I. G. N. A.; Schnetger, Bernhard; Niggemann, Jutta; Simon, Meinhard; Dittmar, Thorsten

    2014-09-01

    Seawater circulation in permeable coastal sediments is driven by tidal changes in hydraulic gradients. The resulting submarine groundwater discharge is a source of nutrients and dissolved organic matter (DOM) to the water column. Yet, little is known about the cycling of DOM within tidal sediments, because the molecular DOM characterization remains analytically challenging. One technique that can dissect the multitude of molecules in DOM is ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). To aim at a high resolution DOM analysis we study the seasonal turnover and marine and terrestrial sources of DOM in an intertidal creek bank of the southern North Sea down to 3 m depth and link the biogeochemical processes to FT-ICR-MS data and the analyses of inorganic porewater chemistry, δ13C of solid-phase extracted dissolved organic carbon (SPE-DOC), dissolved black carbon (DBC) and dissolved carbohydrates (DCHO). Increasing concentrations of dissolved Fe, Mn, P, total alkalinity, dissolved nitrogen, DOC and a concomitant decrease of sulfate along the seawater circulation path from the upper tidal flat to the tidal flat margin indicate continuous microbial activity. The relative increase of Si concentrations, unsaturated aliphatics, peptide molecular formulae and isotopically more 13C-enriched SPE-DOC towards the tidal flat margin suggests that remineralization processes mobilize DOM from buried algal (diatoms) and microbial biomass. Porewater in sediments ocean. Porewater DOM accumulating at the low water line is enriched in N and S. We hypothesize that this is partly due to DOM reacting with dissolved sulfide and ammonium which may increase the refractory character of the DOM, hence making it less bioavailable for in situ active microbes.

  20. The biogeochemistry of carbon in continental slope sediments: The North Carolina margin

    Energy Technology Data Exchange (ETDEWEB)

    Blair, N.; Levin, L.; DeMaster, D.; Plaia, G.; Martin, C.; Fornes, W.; Thomas, C.; Pope, R.

    1999-12-01

    The responses of the continental slope benthos to organic detritus deposition were studied with a multiple trace approach. Study sites were offshore of Cape Fear (I) and Cape Hatteras (III), N.C. (both 850 m water depth) and were characterized by different organic C deposition rates, macrofaunal densities (III>I in both cases) and taxa. Natural abundances of {sup 13}C and {sup 12}C in particulate organic carbon (POC), dissolved inorganic carbon (DIC) and macrofauna indicate that the reactive organic detritus is marine in origin. Natural abundance levels of {sup 14}C and uptake of {sup 13}C-labeled diatoms by benthic animals indicate that they incorporate a relatively young component of carbon into their biomass. {sup 13}C-labeled diatoms (Thalassiorsira pseudonana) tagged with {sup 210}Pb, slope sediment tagged with {sup 113}Sn and {sup 228}Th-labeled glass beads were emplaced in plots on the seafloor at both locations and the plots were sampled after 30 min., 1-1.5 d and 14 mo. At Site I, tracer diatom was intercepted at the surface primarily by protozoans and surface-feeding annelids. Little of the diatom C penetrated below 2 cm even after 14 months. Oxidation of organic carbon appeared to be largely aerobic. At Site III, annelids were primarily responsible for the initial uptake of tracer. On the time scale of days, diatom C was transported to a depth of 12 cm and was found in animals collected between 5-10 cm. The hoeing of tracer from the surface by the maldanid Praxillela sp. may have been responsible for some of the rapid nonlocal transport. Oxidation of the diatom organic carbon was evident to at least 10 cm depth. Anaerobic breakdown of organic matter is more important at Site III. Horizontal transport, which was probably biologically mediated, was an order of magnitude more rapid than vertical displacement over a year time scale. If the horizontal transport was associated with biochemical transformations of the organic matter, it may represent an important but nearly invisible diagenetic process.

  1. River delta network hydraulic residence time distributions and their role in coastal nutrient biogeochemistry

    Science.gov (United States)

    Hiatt, M. R.; Castaneda, E.; Twilley, R.; Hodges, B. R.; Passalacqua, P.

    2015-12-01

    River deltas have the potential to mitigate increased nutrient loading to coastal waters by acting as biofilters that reduce the impact of nutrient enrichment on downstream ecosystems. Hydraulic residence time (HRT) is known to be a major control on biogeochemical processes and deltaic floodplains are hypothesized to have relatively long HRTs. Hydrological connectivity and delta floodplain inundation induced by riverine forces, tides, and winds likely alter surface water flow patterns and HRTs. Since deltaic floodplains are important elements of delta networks and receive significant fluxes of water, sediment, and nutrients from distributary channels, biogeochemical transformations occurring within these zones could significantly reduce nutrient loading to coastal receiving waters. However, network-scale estimates of HRT in river deltas are lacking and little is known about the effects of tides, wind, and the riverine input on the HRT distribution. Subsequently, there lacks a benchmark for evaluating the impact of engineered river diversions on coastal nutrient ecology. In this study, we estimate the HRT of a coastal river delta by using hydrodynamic modeling supported by field data and relate the HRT to spatial and temporal patterns in nitrate levels measured at discrete stations inside a delta island at Wax Lake Delta. We highlight the control of the degree of hydrological connectivity between distributary channels and interdistributary islands on the network HRT distribution and address the roles of tides and wind on altering the shape of the distribution. We compare the observed nitrate concentrations to patterns of channel-floodplain hydrological connectivity and find this connectivity to play a significant role in the nutrient removal. Our results provide insight into the potential role of deltaic wetlands in reducing the nutrient loading to near-shore waters in response to large-scale river diversions.

  2. Coupled cycling of Fe and organic carbon in submarine hydrothermal systems: Impacts on Ocean Biogeochemistry?

    Science.gov (United States)

    German, Christopher; Sander, Sylvia; Legendre, Louis; Niquil, Nathalie; Working Group 135

    2014-05-01

    Submarine hydrothermal venting was first discovered in the late 1970s. For decades the potential impact that vent-fluxes could have on global ocean budgets was restricted to consideration of processes in hydrothermal plumes in which the majority of chemical species are incorporated into polymetallic sulfide and/or oxyhydroxide particles close to the ridge-crest and sink to the underlying seafloor. This restricted view of the role that hydrothermal systems might play in global-ocean budgets has been challenged, more recently, by the recognition that there might also be a significant flux of dissolved Fe from hydrothermal systems to the oceans that is facilitated through thermodynamically stable nanoparticles and organic complexation. The latest results from the recently completed US GEOTRACES program, which has traced high concentrations of dissolved Fe over long distances off-axis from the Southern East Pacific Rise near 15°S, only help to confirm the potential that such fluxes might be important at the global scale. In this paper we review field-based and modeling results, including investigations that we have carried out under the auspices of SCOR-InterRidge Working Group 135, that reveal potential relationships between organic carbon (Corg) and Fe in hydrothermal plumes and allow us to investigate the roles that hydrothermal systems may play in the global biogeochemical cycles of both Fe and Corg. Using the particularly well-studied EPR 9N hydrothermal system as our "type locality" - even though we recognize that no one site can adequately represent the diversity of all hydrothermal systems worldwide - our modeling efforts allow us to reach some significant conclusions concerning: the predicted partitioning of heat fluxes between focused and diffuse flow at ridge axes; and the recognition that while Corg fluxes associated with hydrothermal plume removal may be small on the global scale, they are likely to result in extremely pronounced fluxes, locally, to the seafloor in areas immediately surrounding deep sea hydrothermal systems.

  3. An initial investigation into the organic matter biogeochemistry of the Congo River

    Science.gov (United States)

    Spencer, Robert G.M.; Hernes, Peter J.; Aufdenkampe, Anthony K.; Baker, Andy; Gulliver, Pauline; Stubbins, Aron; Aiken, George R.; Dyda, Rachael Y.; Butler, Kenna D.; Mwamba, Vincent L.; Mangangu, Arthur M.; Wabakanghanzi, Jose N.; Six, Johan

    2012-01-01

    The Congo River, which drains pristine tropical forest and savannah and is the second largest exporter of terrestrial carbon to the ocean, was sampled in early 2008 to investigate organic matter (OM) dynamics in this historically understudied river basin. We examined the elemental (%OC, %N, C:N), isotopic (δ13C, Δ14C, δ15N) and biochemical composition (lignin phenols) of coarse particulate (>63 μm; CPOM) and fine particulate (0.7–63 μm; FPOM) OM and DOC, δ13C, Δ14C and lignin phenol composition with respect to dissolved OM (14C = -62.2 ± -13.2‰, n = 5) compared to CPOM and DOM (mean Δ14C = 55.7 ± 30.6‰, n = 4 and 73.4 ± 16.1‰, n = 5 respectively). The modern radiocarbon ages for DOM belie a degraded lignin compositional signature (i.e. elevated acid:aldehyde ratios (Ad:Al) relative to CPOM and FPOM), and indicate that the application of OM degradation patterns derived from particulate phase studies to dissolved samples needs to be reassessed: these elevated ratios are likely attributable to fractionation processes during solubilization of plant material. The relatively low DOM carbon-normalized lignin yields (Λ8; 0.67–1.12 (mg(100 mg OC)-1)) could also reflect fractionation processes, however, they have also been interpreted as an indication of significant microbial or algal sources of DOM. CPOM appears to be well preserved higher vascular plant material as evidenced by its modern radiocarbon age, elevated C:N (17.2–27.1) and Λ8 values (4.56–7.59 (mg(100 mg OC)-1)). In relation to CPOM, the aged FPOM fraction (320–580 ybp 14C ages) was comparatively degraded, as demonstrated by its nitrogen enrichment (C:N 11.4–14.3), lower Λ8 (2.80–4.31 (mg(100 mg OC)-1)) and elevated lignin Ad:Al values similar to soil derived OM. In this study we observed little modification of the OM signature from sample sites near the cities of Brazzaville and Kinshasa to the head of the estuary (~350 km) highlighting the potential for future studies to assess seasonal and long-term OM dynamics from this logistically feasible location and derive relevant information with respect to OM exported to the Atlantic Ocean. The relative lack of OM data for the Congo River Basin highlights the importance of studies such as this for establishing baselines upon which to gauge future change.

  4. Conquering a wicked problem: New challenges and opportunities for biogeochemistry and catchment science

    Science.gov (United States)

    Haygarth, P.

    2012-04-01

    Meeting the demands of good water quality such as those of the EU Water Framework Directive is a complicated, wicked problem. On the one hand the directive forces us to consider the catchment as a single functioning unit, a water body where ecological status can be assessed and classified. On the other hand, catchments are most obviously perturbed and managed in spatially and temporally discrete units. This makes assigning the 'cause' and 'response' particularly complicated - the familiar problem of managing diffuse pollution. This talk will explore some of these complexities in understanding the diffuse pollution 'cause' and 'response' in catchment science. Some particular opportunities may lie in cross team consortia style working, with multidisciplinary 'platforms' of study and value added information sharing. This should include nurturing full ownership and empowerment of the problem (and solutions) with the local communities - the solutions need to be encouraged to come from those who own and work in the catchments. The presentation will also consider some new opportunities for the sustainable management of phosphorus in catchments.

  5. The Biogeochemistry of Contaminant Groundwater Plumes Arising from Waste Disposal Facilities

    DEFF Research Database (Denmark)

    Bjerg, Poul Løgstrup; Albrechtsen, Hans-Jørgen; Kjeldsen, Peter

    2014-01-01

    Landfills with solid waste are abundant sources of groundwater pollution all over the world. Old uncontrolled municipal landfills are often large, heterogeneous sources with demolition waste, minor fractions of commercial or industrial waste, and organic waste from households. Strongly anaerobic ...... at landfill sites. Finally, the potential chemical or ecological impact from landfills located in former wetlands or near surface water bodies may deserve attention in future studies....

  6. Global Biogeochemistry Models and Global Carbon Cycle Research at Lawrence Livermore National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Covey, C; Caldeira, K; Guilderson, T; Cameron-Smith, P; Govindasamy, B; Swanston, C; Wickett, M; Mirin, A; Bader, D

    2005-05-27

    The climate modeling community has long envisioned an evolution from physical climate models to ''earth system'' models that include the effects of biology and chemistry, particularly those processes related to the global carbon cycle. The widely reproduced Box 3, Figure 1 from the 2001 IPCC Scientific Assessment schematically describes that evolution. The community generally accepts the premise that understanding and predicting global and regional climate change requires the inclusion of carbon cycle processes in models to fully simulate the feedbacks between the climate system and the carbon cycle. Moreover, models will ultimately be employed to predict atmospheric concentrations of CO{sub 2} and other greenhouse gases as a function of anthropogenic and natural processes, such as industrial emissions, terrestrial carbon fixation, sequestration, land use patterns, etc. Nevertheless, the development of coupled climate-carbon models with demonstrable quantitative skill will require a significant amount of effort and time to understand and validate their behavior at both the process level and as integrated systems. It is important to consider objectively whether the currently proposed strategies to develop and validate earth system models are optimal, or even sufficient, and whether alternative strategies should be pursued. Carbon-climate models are going to be complex, with the carbon cycle strongly interacting with many other components. Off-line process validation will be insufficient. As was found in coupled atmosphere-ocean GCMs, feedbacks between model components can amplify small errors and uncertainties in one process to produce large biases in the simulated climate. The persistent tropical western Pacific Ocean ''double ITCZ'' and upper troposphere ''cold pole'' problems are examples. Finding and fixing similar types of problems in coupled carbon-climate models especially will be difficult, given the lack of observations required for diagnosis and validation of biogeochemical processes.

  7. Warming up, turning sour, losing breath: ocean biogeochemistry under global change.

    Science.gov (United States)

    Gruber, Nicolas

    2011-05-28

    In the coming decades and centuries, the ocean's biogeochemical cycles and ecosystems will become increasingly stressed by at least three independent factors. Rising temperatures, ocean acidification and ocean deoxygenation will cause substantial changes in the physical, chemical and biological environment, which will then affect the ocean's biogeochemical cycles and ecosystems in ways that we are only beginning to fathom. Ocean warming will not only affect organisms and biogeochemical cycles directly, but will also increase upper ocean stratification. The changes in the ocean's carbonate chemistry induced by the uptake of anthropogenic carbon dioxide (CO(2)) (i.e. ocean acidification) will probably affect many organisms and processes, although in ways that are currently not well understood. Ocean deoxygenation, i.e. the loss of dissolved oxygen (O(2)) from the ocean, is bound to occur in a warming and more stratified ocean, causing stress to macro-organisms that critically depend on sufficient levels of oxygen. These three stressors-warming, acidification and deoxygenation-will tend to operate globally, although with distinct regional differences. The impacts of ocean acidification tend to be strongest in the high latitudes, whereas the low-oxygen regions of the low latitudes are most vulnerable to ocean deoxygenation. Specific regions, such as the eastern boundary upwelling systems, will be strongly affected by all three stressors, making them potential hotspots for change. Of additional concern are synergistic effects, such as ocean acidification-induced changes in the type and magnitude of the organic matter exported to the ocean's interior, which then might cause substantial changes in the oxygen concentration there. Ocean warming, acidification and deoxygenation are essentially irreversible on centennial time scales, i.e. once these changes have occurred, it will take centuries for the ocean to recover. With the emission of CO(2) being the primary driver behind all three stressors, the primary mitigation strategy is to reduce these emissions.

  8. Impact of Bacterial NO3- Transport on Sediment Biogeochemistry

    DEFF Research Database (Denmark)

    Nielsen, Lars Peter

    2005-01-01

    Experiments demonstrated that Beggiatoa could induce a H2S-depleted suboxic zone of more than 10 mm in marine sediments and cause a divergence in sediment NO3- reduction from denitrification to dissimilatory NO3- reduction to ammonium. pH, O2, and H2S profiles indicated that the bacteria oxidized H......2S with NO3- and transported S0 to the sediment surface for aerobic oxidation....

  9. Biogeochemistry of Redox at Repository Depth and Implications for the Canister

    Energy Technology Data Exchange (ETDEWEB)

    Bath, Adrian; Hermansson, Hans-Peter

    2009-08-15

    The present groundwater chemical conditions at the candidate sites for a spent nuclear fuel repository in Sweden (the Forsmark and Laxemar sites) and processes affecting its future evolution comprise essential conditions for the evaluation of barrier performance and long-term safety. This report reviews available chemical sampling information from the site investigations at the candidate sites, with a particular emphasis on redox active groundwater components and microbial populations that influence redox affecting components. Corrosion of copper canister material is the main barrier performance influence of redox conditions that is elaborated in the report. One section addresses native copper as a reasonable analogue for canister materials and another addresses the feasibility of methane hydrate ice accumulation during permafrost conditions. Such an accumulation could increase organic carbon availability in scenarios involving microbial sulphate reduction. The purpose of the project is to evaluate and describe the available knowledge and data for interpretation of geochemistry, microbiology and corrosion in safety assessment. A conclusive assessment of the sufficiency of information can, however, only be done in the future context of a full safety assessment. The authors conclude that SKB's data and models for chemical and microbial processes are adequate and reasonably coherent. The redox conditions in the repository horizon are predominantly established through the SO{sub 4}2-/HS- and Fe3+/Fe2+ redox couples. The former may exhibit a more significant buffering effect as suggested by measured Eh values, while the latter is associated with a lager capacity due to abundant Fe(II) minerals in the bedrock. Among a large numbers of groundwater features considered in geochemical equilibrium modelling, Eh, pH, temperature and concentration of dissolved sulphide comprise the most essential canister corrosion influences. Groundwater sulphide may originate from sulphide minerals and ongoing sulphate reduction as indicated by SRB populations, and may be limited by organic carbon availability. Another possible route for sulphate reduction is by coupling with anaerobic methane oxidation. However, during present day conditions methane levels at Forsmark and Laxemar are probably too low for any essential sulphide production by that route. Methane hydrate could accumulate in fractures and repository void spaces beneath permafrost, but the potential impacts would be minimised by low porosity in crystalline rocks down to and below repository depth

  10. A Visual Approach Towards Introduction of Bio-Geochemistry at Non-Ambient Conditions

    Science.gov (United States)

    Sharma, A.

    2005-12-01

    Visualization of processes is considered an important aspect of education at an introductory as well as advanced levels. To facilitate a deeper understanding of the mechanisms in which chemistry takes place in geological processes, molecular interaction mechanisms have been introduced in novel ways by computer animated models. As successful such approach may be, it does little to provide a 'real' visualization of the various controls and mechanisms. Any attempts on observing real geochemical systems is further complicated by the fact that most of the ongoing geochemical activity is at non-ambient conditions. In this presentation, the author will introduce techniques and examples of direct visualization of 'chemistry at extremes' that are currently under use in classroom and are aimed towards future development of web-based interactive lectures. In this approach the author is using various optical cells to demonstrate 'model' system behavior under non-ambient conditions to infer further details regarding possible on-going geochemistry in the deep subsurface. As an example, observations and in-situ spectroscopic measurements are used to demonstrate changes in the chemical properties of fluids from sub-critical to super-critical conditions. Such direct observation approach has been helpful in not only providing a visual perspective of 'extreme' processes, but also helpful in introducing some rather advanced topics to a more receptive introductory student population ranging from elementary school to college. This presentation will provide some example successfully used in the classroom and provide an introduction to a web-based interactive learning tool accessible to a wider student population.

  11. High-speed limnology: using advanced sensors to investigate spatial variability in biogeochemistry and hydrology.

    Science.gov (United States)

    Crawford, John T; Loken, Luke C; Casson, Nora J; Smith, Colin; Stone, Amanda G; Winslow, Luke A

    2015-01-06

    Advanced sensor technology is widely used in aquatic monitoring and research. Most applications focus on temporal variability, whereas spatial variability has been challenging to document. We assess the capability of water chemistry sensors embedded in a high-speed water intake system to document spatial variability. This new sensor platform continuously samples surface water at a range of speeds (0 to >45 km h(-1)) resulting in high-density, mesoscale spatial data. These novel observations reveal previously unknown variability in physical, chemical, and biological factors in streams, rivers, and lakes. By combining multiple sensors into one platform, we were able to detect terrestrial-aquatic hydrologic connections in a small dystrophic lake, to infer the role of main-channel vs backwater nutrient processing in a large river and to detect sharp chemical changes across aquatic ecosystem boundaries in a stream/lake complex. Spatial sensor data were verified in our examples by comparing with standard lab-based measurements of selected variables. Spatial fDOM data showed strong correlation with wet chemistry measurements of DOC, and optical NO3 concentrations were highly correlated with lab-based measurements. High-frequency spatial data similar to our examples could be used to further understand aquatic biogeochemical fluxes, ecological patterns, and ecosystem processes, and will both inform and benefit from fixed-site data.

  12. Biogeochemistry and biodiversity of methane cycling in subsurface marine sediments (Skagerrak, Denmark)

    DEFF Research Database (Denmark)

    Parkes, R.John; Cragg, Barry A.; Banning, Natasha

    2007-01-01

    , Methanomicrobiales, Methanosaeta Archaea, with abundance changes with depth corresponding to changes in activities and sulfate-reducing bacteria (SRB). Below the SMTZ to 1.7 m CH4 became progressively more 13C depleted (δ13C -82‰) indicating a zone of CH4 recycling which was consistent with the presence of 13C...

  13. Implication of future large-scale stratospheric aerosol injection on the land and ocean biogeochemistry

    Science.gov (United States)

    Tjiputra, Jerry; Grini, Alf

    2015-04-01

    In this study, we address several outstanding and emerging issues of future climate geoengineering, particularly its impact on the global biogeochemical. Applying a state-of-the-art fully interactive Earth system model, we simulate two cases of artificial stratospheric aerosol injection (SAI) on top of future RCP8.5 scenario. In the first case, the SAI brings the projection of global mean surface temperature down to the RCP4.5 level by the end of this century. For the same climate target, the non-mitigated, climate engineered scenario leads to approximately 100% and 50% more carbon sinks by the ocean and terrestrial biosphere, respectively. Consequently, the reduction in ocean surface pH is approximately three times stronger than the mitigated RCP4.5 scenario. In the second SAI case, stronger climate engineering (CE) could bring the projected temperature at 2100 down to the 2000 level. In this case, warming still occurs in the Arctic regions. Compared to the reference RCP8.5 without CE, the net global cumulative carbon uptake by land and ocean only increase slightly. Regionally, the biggest difference in carbon inventory were simulated in the mid-latitude northern hemisphere over land and the North Atlantic and Southern Oceans. Over land, reduced soil respiration overcomes reduction in the net primary production associated primarily with the cooler climate. In the North Atlantic, stabilized meridional overturning allows for more carbon sequestered into the ocean interior, while the absence of poleward amplification of Southern Annual Mode leads to less outgassing of natural carbon in the Southern Ocean. CE-induced cooling also alleviates the reduction of net primary production in the equatorial Pacific related to stratification change. Following SAI termination in 2100, rapid warming in the next few years was simulated, bringing the global temperature up to the reference RCP8.5 simulation level. By 2200, the net cumulative carbon sinks by land and ocean is insignificantly different than the scenario without climate engineering, implying that future CE impact on the climate-carbon cycle feedback is likely to be relatively weak and short lived.

  14. Aggregate-Scale Variation in Iron Biogeochemistry Controls Element Cycling from Nitrogen to Uranium

    Science.gov (United States)

    Fendorf, S. E.; Ying, S.; Jones, L. C.; Jones, M. E.

    2014-12-01

    Iron exerts a major control on element cycling in soils by serving as a prominent sorbent (principally when present as an oxide phase) and as an electron acceptor (in the ferric-form) or donor (ferrous-form) in both chemical and microbially-mediated reactions. Within the aggregated structure of soils, steep chemical gradients arise from the supply of oxygen and nutrients along macropores that are rapidly consumed (relative to supply) within the micropore domains of aggregate interiors. As a consequence, iron undergoes a dynamic biogeochemical cycle whereby ferric (hydr)oxides form within aggregate exteriors while ferrous-iron generation dominates within interior regions. Further, inter-aggregate cycling of iron can transpire through the supply of electron donors and acceptors, linked with diffusive controlled response to gradients. Coupling to iron transformation are the varying retention of adsorptives such as lead and phosphorus and the redox alterations of elements from nitrogen to uranium. Nitrate, for example, diffusing into aggregate interiors encounters ferrous-iron fronts where the ensuring oxidation of Fe(II)-coupled to nitrate reduction transpires. The outcome of aggregate-scale iron transformations, described within this presentation, is fundamental controls on the cycling of redox active elements from nutrients such as carbon and nitrogen to contaminants such arsenic and uranium.

  15. Biogeochemistry of the surficial sediments of the western and eastern continental shelves of India

    Digital Repository Service at National Institute of Oceanography (India)

    Jacob, J.; Chandramohanakumar, N.; Jayaraj, K.A.; Raveendran, T.V.; Balachandran, K.K.; Joseph, T.; Nair, M.; Achuthankutty, C.T.; Nair, K.K.C.; George, R.; Ravi, Z.P.

    continental shelves of India were studied for their total organic matter content and the labile constituents such as total carbohydrates and proteins to get a better understanding of the hydrological and biogeochemical differences of the two regions...

  16. Environmental metabolomics: Elucidating the metabolic reactions that link the "bio" and "geo" in biogeochemistry

    Science.gov (United States)

    Higgins, M. B.

    2012-12-01

    One goal of environmental microbiology is to gain a quantitative knowledge of chemical processes that occur within individual microbes and microbial ecosystems. While recent advances in techniques that combine stable isotope measurements with phylogenetic identification have been able to link key microbial players to biogeochemical processes, the precise details of metabolic pathways and their kinetics under various environmental conditions remain a challenge to measure. "Omics" approaches that focus on gene and transcript identification elucidate the biological potential for biochemical reactions but not their cellular rates. The emerging field of environmental metabolomics uses high-resolution mass spectrometry for high-throughput quantitation of large suites of cellular metabolites. Using stable-isotope labeling of microbial samples, such an approach enables both the identification of metabolites involved in biochemical pathways and an estimate of changes in cellular metabolite pool sizes under different environmental conditions, as well as kinetic measurements of biochemical fluxes.

  17. Impact of tropical cyclone on biogeochemistry of the central Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naik, H.; Naqvi, S.W.A.; Suresh, T.; Narvekar, P.V.

    convection. Second, nutrient injection into the euphotic zone lags behind surface cooling by several days. For example, despite the aforementioned decrease in SST through December recorded by the moored arrays, surface nitrate (NO 3 C0 )concentrations along... samples were filtered and preserved for Chl a analysis in the shore laboratory following the standard fluorescence technique [Naqvi et al., 2002], but during transit from the ship filters from the second leg were accidentally lost. The CTD fluorescence...

  18. Biogeochemistry of organic and inorganic arsenic species in a forested catchment in Germany.

    Science.gov (United States)

    Huang, Jen-How; Matzner, Egbert

    2007-03-01

    Little is known about the fate and behavior of diffuse inputs of arsenic (As) species in forested catchments which often are the sources of drinking water. The objective of this study was to investigate the mobility and transformation of different As species in forest ecosystems to assess the environmental risk related to the diffuse pollution of As. We determined concentrations and fluxes in precipitation, litterfall, soil solutions (Oa horizon and 20- and 90-cm depth), and runoff of organic and inorganic As species and Astotal in a forest ecosystem in NE-Bavaria, Germany. The concentrations of Astotal were mostly catchment amounted to 3.8 g As ha(-1) yr(-1). The annual fluxes of total organic As species was highest in total deposition (1.1 g As ha(-1) yr(-1)) and decreased largely with depth in the soil profile. The annual runoff of total organic As species was only 0.08 g As ha(-1) yr(-1). Significant correlations in soil solutions and runoff were found between Astotal and dissolved organic C and Fe. Correlations between Astotal concentrations in runoff and water fluxes were seasonally dependent and with a steeper slope in the growing season than in the dormant season. The elevated concentrations of organic As species in throughfall indicate microbial methylation of As in the phyllosphere, but no evidence for methylation in the soil was found. The mass balance of the catchment points out the strong retention and probable degradation or oxidation of organic As species and arsenite but also to mobilizable pools of Astotal and arsenate. The forest floor is presently a source, whereas the mineral soil is a sink for Astotal and arsenate. The As concentrations in runoff seem to be controlled by As mobilization from forest floor and riparian wetland soils during heavy rain events and superficial flow. The risk for excessment of the drinking water threshold concentrations of As in runoff and soil solutions is considered low at our site.

  19. History and prospect of catchment biogeochemistry: a european perspective based on acid rain

    NARCIS (Netherlands)

    Breemen, van N.; Wright, R.F.

    2004-01-01

    Hydrochemical monitoring of catchments provided a philosophical framework as well as hard data to understand and quantify the linked biological and abiotic processes that explain how atmospheric deposition of S and N changed soils and waters in nonagricultural areas across Europe. Initially, as a to

  20. Nitrate Biogeochemistry and Reactive Transport in California Groundwater: LDRD Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Esser, B K; Beller, H; Carle, S; Cey, B; Hudson, G B; Leif, R; LeTain, T; Moody-Bartel, C; Moore, K; McNab, W; Moran, J; Tompson, A

    2006-02-24

    Nitrate is the number one drinking water contaminant in the United States. It is pervasive in surface and groundwater systems,and its principal anthropogenic sources have increased dramatically in the last 50 years. In California alone, one third of the public drinking-water wells has been lost since 1988 and nitrate contamination is the most common reason for abandonment. Effective nitrate management in groundwater is complicated by uncertainties related to multiple point and non-point sources, hydrogeologic complexity, geochemical reactivity, and quantification of denitrification processes. In this paper, we review an integrated experimental and simulation-based framework being developed to study the fate of nitrate in a 25 km-long groundwater subbasin south of San Jose, California, a historically agricultural area now undergoing rapid urbanization with increasing demands for groundwater. The modeling approach is driven by a need to integrate new and archival data that support the hypothesis that nitrate fate and transport at the basin scale is intricately related to hydrostratigraphic complexity, variability of flow paths and groundwater residence times, microbial activity, and multiple geochemical reaction mechanisms. This study synthesizes these disparate and multi-scale data into a three-dimensional and highly resolved reactive transport modeling framework.

  1. Biogeochemistry of heavy metals in contaminated excessively moistened soils (Analytical review)

    Science.gov (United States)

    Vodyanitskii, Yu. N.; Plekhanova, I. O.

    2014-03-01

    The biogeochemical behavior of heavy metals in contaminated excessively moistened soils depends on the development of reducing conditions (either moderate or strong). Upon the moderate biogenic reduction, Cr as the metal with variable valence forms low-soluble compounds, which decreases its availability to plants and prevents its penetration into surface- and groundwater. Creation of artificial barriers for Cr fixation on contaminated sites is based on the stimulation of natural metal-reducing bacteria. Arsenic, being a metalloid with a variable valence, is mobilized upon the moderate biogenic reduction. The mobility of siderophilic heavy metals with a constant valence grows under the moderate reducing conditions at the expense of dissolution of iron (hydr)oxides as carriers of these metals. Zinc, which can enter the newly formed goethite lattice, is an exception. Strong reduction processes in organic excessively moist and flooded soils (usually enriched in S) lead to the formation of low-soluble sulfides of heavy elements with both variable (As) and constant (Cu, Ni, Zn, and Pb) valence. On changing aquatic regime in overmoistened soils and their drying, sulfides of heavy metals are oxidized, and previously fixed metals are mobilized.

  2. Biogeochemistry of mercury in soils and sediments in a mining-impacted watershed, California

    Science.gov (United States)

    Holloway, J. M.; Goldhaber, M. B.

    2004-12-01

    The East Davis Creek watershed, located in the California Coast Ranges, is host to historic mines that provided mercury for recovery of gold in the Sierra Nevada goldfields in the mid-to-late 1800s. Bedrock in this watershed includes marine sedimentary rock, serpentinite, and hydrothermally altered serpentinite. Cinnabar (HgS) found in the altered serpentinite is the primary ore mineral for mercury. We evaluated the hypothesis that mercury is sequestered in soil organic matter downstream from source areas, releasing a fraction as water-soluble methylmercury. Microbial biomass and the presence of sulfur-reducing bacteria implicated in mercury methylation were quantified using phospholipid fatty acid (PLFA) data. Methylation incubations were performed on soil and sediment inoculated with water from Davis Creek Reservoir and sealed in glass containers under an anoxic headspace for 21 days. Methylmercury was measured on extracts of the soils at the start and at the end of the incubation period. Two sources of mercury to stream sediments, a soil with an altered serpentinite parent and mine tailings, were incubated. Stream sediment, an overbank deposit soil and a wetland soil forming from these sediments were also incubated. The overbank deposit soil is periodically flooded. The wetland soil around the edge of Davis Creek Reservoir is perennially saturated with water. The altered serpentinite soil and mine tailings had the highest total mercury concentrations (170 and 150 ng Hg /g, respectively). Total mercury concentrations in stream sediments are low (¡Ü1 ng Hg/g), with higher mercury concentrations in the overbank (3 ng/g) and wetland soils (18 ng Hg/g). Mercury leached from altered serpentinite soils and mine tailings may be transported downstream and sequestered through sorption to organic matter in the overbank and wetland soils. PLFA biomarkers for Desulfobacter (10Me16:0) and Desulfovibrio (i17:1) were present in all incubated materials, with lower concentrations in mine tailings and stream sediment relative to the three soils examined. Methylmercury was initially present in greater concentrations in the overbank deposit (23 ng HgMe/g) soils. The elevated methyl mercury in the overbank deposit soil may be due to the greater biomass of sulfur reducing bacteria indicated by the 10Me16:0 and i17:1 biomarkers. During the 21-day incubation, methylmercury increased from 0.6 to 15 ng HgMe/g in the wetland soil concomitantly with sulfate decreasing from 130 to 7.0 mg SO4=/g. Methylmercury concentrations did not change appreciably in the other soils, although sulfate decreased from 19 to 2.0 mg SO4=/g in the overbank deposit soil. These data suggest that overbank deposits and wetland soils sequester mercury leached from upstream sources, with a fraction of this mercury released through microbial methylation.

  3. Impacts of phosphate amendments on lead biogeochemistry at a contaminated site.

    Science.gov (United States)

    Cao, Xinde; Ma, Lena Q; Chen, Ming; Singh, Satya P; Harris, Willie G

    2002-12-15

    Soil amendments can be used to cost-effectively reduce the bioavailability and mobility of toxic metals in contaminated soils. In this study a field demonstration was conducted at a Pb-contaminated site to evaluate the effectiveness of P-induced Pb immobilization. Phosphate was applied at a 4.0 molar ratio of P to Pb with three treatments: T1, 100% of P from H3PO4; T2, 50% P from H3PO4 + 50% P from Ca(H2PO4)2; and T3, 50% P from H3PO4 + 5% phosphate rock. Phosphate amendments effectively transformed soil Pb from the nonresidual (sum of exchangeable, carbonate, Fe/Mn, and organic) to the residual fraction, with residual Pb increase by 19-48% for T1, 22-50% for T2, and 11-55% for T3, respectively. Lead immobilization was attributed to the P-induced formation of chloropyromorphite [Pb10(PO4)6Cl2], which was identified in the surface soil, subsurface soil, and plant rhizosphere soil. Occurrence of chloropyromorphite was evident 220 days after P addition for T1 and T2 treatments and 330 days for T3. Visual MINTEQ model and activity-ratio diagram indicated that lead phosphate minerals controlled Pb2+ activities in the P-treated soils. Phosphate treatments significantly reduced Pb translocation from the roots to the shoots in the St. Augustine grass (Stenotaphrum secundatum), possibly via the formation of chloropyromorphite on the cell walls of roots. This field observation suggested that P amendments are efficient in reducing Pb mobility via in situ formation of insoluble chloropyromorphite minerals at a field setting. Lead immobilization shows a long-term stability. A mixture of H3PO4 and phosphate rock yields the best overall results for in situ Pb immobilization, with less soil pH change and less P leaching. Application of combined H3PO4 with phosphate rock may provide an effective alternative to the current phosphate remediation technologies for contaminated soils.

  4. One-carbon (bio?)geochemistry in subsurface waters of the serpentinizing Coast Range Ophiolite

    Science.gov (United States)

    Hoehler, T. M.; McCollom, T.; Schrenk, M. O.; Kubo, M.; Cardace, D.

    2011-12-01

    Serpentinization - the aqueous alteration of ultramafic rocks - typically imparts a highly reducing and alkaline character to the reacting fluids. In turn, these can influence the speciation and potential for metabolism of one-carbon compounds in the system. We examined the aqueous geochemistry and assessed the biological potential of one-carbon compounds in the subsurface of the McLaughlin Natural Reserve (Coast Range Ophiolite, California, USA). Fluids from wells sunk at depths of 25-90 meters have pH values ranging from 9.7 to 11.5 and dissolved inorganic carbon (DIC concentrations) generally below 60 micromolar. Methane is present at concentrations up to 1.3 millimolar (approximately one-atmosphere saturation), and hydrogen concentrations are below 15 nanomolar, suggesting active consumption of H2 and production of CH4. However, methane production from CO2 is thermodynamically unfavorable under these conditions. Additionally, the speciation of DIC predominantly into carbonate at these high pH values creates a problem of carbon availability for any organisms that require CO2 (or bicarbonate) for catabolism or anabolism. A potential alternative is carbon monoxide, which is present in these waters at concentrations 2000-fold higher than equilibrium with atmospheric CO. CO is utilized in a variety of metabolisms, including methanogenesis, and bioavailability is not adversely affected by pH-dependent speciation (as for DIC). Methanogenesis from CO under in situ conditions is thermodynamically favorable and would satisfy biological energy requirements with respect to both Gibbs Energy yield and power.

  5. Stable isotopes and changing paradigms on soil nitrogen and carbon biogeochemistry

    Directory of Open Access Journals (Sweden)

    J. A. Carreira

    2010-01-01

    Full Text Available Muchos de los modelos conceptuales e ideas desarrollados en el ámbito de la biogeoquímica se basan en diagramas de flujo que representan las reservas de nutrientes como "cajas" interconectadas por "flechas" que indican los procesos abióticos y bióticos que regulan su transformación y flujo entre reservas. El uso de isótopos estables permite integrar dichos procesos en el espacio y en el tiempo, y por ello han jugado un papel central en la comprensión de los ciclos de nutrientes como el N y el C en los ecosistemas, y en particular en el suelo. Aquí revisamos el proceso de cambio de paradigmas que ha tenido lugar respecto al reciclado de estos nutrientes en el suelo; un proceso en el que los isótopos estables han contribuido significativamente a través de tres aproximaciones principales: (i como integradores en balances de entrada/salida que consideran como "cajas negras" a compartimentos amplios del ecosistema, (ii como trazadores para revelar procesos intermedios que operan dentro de las "cajas negras" y el destino final de los nutrientes, y (iii como marcadores o indicadores de uso, disponibilidad y estrés por nutrientes en las plantas. También se discuten los retos actuales y las perspectivas de futuro a este respecto.

  6. CMIP5 earth system models with biogeochemistry: An assessment for the southwest Pacific Ocean

    Science.gov (United States)

    Rickard, Graham J.; Behrens, Erik; Chiswell, Stephen M.

    2016-10-01

    An assessment is made of the ability of CMIP5 models to represent the seasonal biogeochemical cycles over the late twentieth century in the southwest Pacific Ocean. In particular, sea surface temperature (SST), surface chlorophyll a, nitrate, phosphate, silicate, and the depth of the seasonal thermocline, are examined to quantify the physical-biogeochemical capabilities of each model; the result is a "ranking" estimate enabling model ensemble generation. The better/less ranked ensembles we refer to as inner/outer, respectively. The ensembles then allow less well-observed variables such as iron and vertically integrated primary production to be assessed. The assessment establishes model output confidence limits for setting bounds on future model scenario ecosystem change projections. By the end of the twenty first century under Representative Concentration Pathways (RCP) RCP4.5 and/or RCP8.5, our best estimates suggest that there will be average domain wide increases in SST and surface iron, but average decreases in surface chlorophyll a, nitrate, and phosphate, accompanied by relatively large decreases in the depth of the seasonal thermocline (all changes realized by both ensembles). On the other hand, for surface silicate the inner ensemble suggests general declines, and vice versa for the outer ensemble. For integrated primary production, the ensembles predict declines in subtropical water, but elsewhere generally less significant changes.

  7. Biogeochemistry and ecology of Pyrosoma spinosum from the Central Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Gauns, M.; Mochemadkar, S.; Pratihary, A.K.; Roy, R.; Naqvi, S.W.A.

    (flagellates and cyanobacteria) that seems to offer favorable conditions for episodic occurrence of swarms of these filter feeders. Low carbon content (37% of total dry weight) and the lower molar (carbon-to-nitrogen) ratio (5) in P. spinosum suggest growth...

  8. Influence of carbon sequestration on biogeochemistry of carbon in the ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Sarma, V.V.S.S.

    stream_size 8 stream_content_type text/plain stream_name Proc_Natl_Conf_Global_Temp_Rise_2007_125.pdf.txt stream_source_info Proc_Natl_Conf_Global_Temp_Rise_2007_125.pdf.txt Content-Encoding ISO-8859-1 Content-Type text...

  9. Core sediment biogeochemistry in specific zones of Cochin Estuarine System (CES)

    Indian Academy of Sciences (India)

    P S Akhil; Manju P Nair; C H Sujatha

    2013-12-01

    Geochemical composition is a set of data for predicting the climatic condition existing in an ecosystem. Both the surficial and core sediment geochemistry are helpful in monitoring, assessing and evaluating the marine environment. The aim of the research work is to assess the relationship between the biogeochemical constituents in the Cochin Estuarine System (CES), their modifications after a long period of anoxia and also to identify the various processes which control the sediment composition in this region, through a multivariate statistical approach. Therefore the study of present core sediment geochemistry has a critical role in unraveling the benchmark of their characterization. Sediment cores from four prominent zones of CES were examined for various biogeochemical aspects. The results have served as rejuvenating records for the prediction of core sediment status prevailing in the CES.

  10. A Dynamic Information Framework (DIF): A Portal for the Changing Biogeochemistry of Aquatic Systems

    Science.gov (United States)

    Richey, J. E.; Fernandes, E. C. M.

    2014-12-01

    The ability of societies to adapt to climate and landuse change in aquatic systems is functionally and practically expressed by how regional stakeholders are able to address complex management issues. These targets represent a very complex set of intersecting issues of scale, cross-sector science and technology, education, politics, and economics. Implications transcend individual projects and ministries. An immediate challenge is to incorporate the realities of changing environmental conditions in these sectors into the policies and projects of the Ministries nominally responsible. Ideally this would be done on the basis of the absolute best understanding of the issues involved, and done in a way that optimizes a multi-stakeholder return. Central to a response is "actionable information-" the synthesis and "bringing to life" of the key information that integrates the end-to-end knowledge required to provide the high-level decision support to make the most informed decisions. But, in practice, the information necessary and even perspectives are virtually absent, in much of especially the developing world. To meet this challenge, we have been developing a Dynamic Information Framework (DIF), primarily through collaborations with the World Bank in Asia, Africa, and Brazil. The DIF is, essentially a decision support structure, built around "earth system" models. The environment is built on progressive information layers that are fed through hydrological and geospatial landscape models to produce outputs that address specific science questions related to water resources management of the region. Information layers from diverse sources are assembled, according to the principles of how the landscape is organized, and computer models are used to bring the information "to life." A fundamental aspect to a DIF is not only the convergence of multi-sector information, but how that information can be conveyed, in the most compelling, and visual, manner. Deployment of the environment in the Cloud facilitates access for stakeholders.

  11. Current understanding of Phaeocystis ecology and biogeochemistry, and perspectives for future research

    NARCIS (Netherlands)

    Verity, Peter G.; Brussaard, Corina P.; Nejstgaard, Jens C.; van Leeuwe, Maria A.; Lancelot, Christiane; Medlin, Linda K.

    2007-01-01

    The phytoplankton genus Phaeocystis has well-documented, spatially and temporally extensive blooms of gelatinous colonies; these are associated with release of copious amounts of dimethyl sulphide (an important climate-cooling aerosol) and alterations of material flows among trophic levels and expor

  12. Late Holocene variations in Pacific surface circulation and biogeochemistry inferred from proteinaceous deep-sea corals

    Directory of Open Access Journals (Sweden)

    T. P. Guilderson

    2013-09-01

    Full Text Available δ15N and δ13C data obtained from samples of proteinaceous deep-sea corals collected from the North Pacific Subtropical Gyre (Hawaiian Archipelago and the central equatorial Pacific (Line Islands document multidecadal to century-scale variability in the isotopic composition of surface-produced particulate organic matter exported to the deep sea. Comparison of the δ13C data, where Line Islands samples are 0.6‰ more positive than the Hawaiian samples, supports the contention that the North Pacific Subtropical Gyre is more efficient than the tropical upwelling system at trapping and/or recycling nutrients within the mixed layer. δ15N values from the Line Islands samples are also more positive than those from the central gyre, and within the Hawaiian samples there is a gradient with more positive δ15N values in samples from the main Hawaiian Islands versus the French Frigate Shoals in the Northwestern Hawaiian Islands. The gradient in the Hawaiian samples likely reflects the relative importance of algal acquisition of metabolic N via dissolved seawater nitrate uptake versus nitrogen fixation. The Hawaiian sample set also exhibits a strong decrease in δ15N values from the mid-Holocene to present. We hypothesize that this decrease is most likely the result of decreasing trade winds, and possibly a commensurate decrease in entrainment of more positive δ15N-NO3 subthermocline water masses.

  13. Magnetic minerals in the environment: a journey between physics and biogeochemistry

    Science.gov (United States)

    Egli, R.

    2009-04-01

    Magnetic minerals are universally present in rocks and sediments. Their abundance and variety in sediments is controlled by several processes taking place at the Earth's surface, which include erosion, transport in water and in the atmosphere, and a variety of diagenetic processes where iron is chemically cycled. Each process imprints a particular signature on the magnetic minerals affected by it, either through grain size sorting, transport paths connected to different reservoirs, or crystal growth. This in turn controls the bulk magnetic properties of sediments, which can be used as a proxy for given environmental processes. Magnetic proxies have the advantage of being based on inexpensive, non-destructive measurements. On the other hand, a disadvantage of such proxies is the lack of strict physical models needed to understand the magnetic properties of non-ideal magnetic particles on one hand, and of accurate models for physical, chemical and biological processes affecting their occurrence. Early environmental magnetism studies were based on simple bulk magnetic measurements, such as susceptibility and hysteresis parameters. Such studies where able to discriminate among different chemical compositions (e.g. ferrimagnetic vs. antiferromagnetic minerals), as well as providing a rough grain size estimate. Because of the simultaneous occurrence of different magnetic minerals with distinct grain size distributions (e.g. ultrafine authigenic vs coarse detrital particles), the need of appropriate unmixing techniques became soon evident. Along with this approach, the sediment is supposed to contain a certain number of magnetic grain families, called magnetic components. Each component is generated by specific environmental processes. Examples include loessic components, generated by the aeolian transport of dust, pedogenic components, generated by weathering of parent material and iron cycling in topsoils, and biogenic components, which are given by iron biomieralization products, such as magnetosomes. Different methods spanning from cluster analysis to coercivity analysis have been recently used to identify such components. By comparison with end-members, obtained by measuring reference samples, it is possible to calibrate magnetic measurements in order to obtain parameters such as mass concentration and grain size, that can be directly used to model specific processes that affect those components. This approach requires knowledges spanning from rock and mineral physics, to geochemistry and biology, and provides precise parameters, such as concentration, that, unlike magnetic measurements, can be compared directly with geochemical proxies. I will discuss a few examples based on authigenic minerals formed in lake sediments and soils, showing how certain interpretation problems can be solved and new questions are raised at the same time.

  14. Microbial biogeochemistry of Boiling Springs Lake: a physically dynamic, oligotrophic, low-pH geothermal ecosystem.

    Science.gov (United States)

    Siering, P L; Wolfe, G V; Wilson, M S; Yip, A N; Carey, C M; Wardman, C D; Shapiro, R S; Stedman, K M; Kyle, J; Yuan, T; Van Nostrand, J D; He, Z; Zhou, J

    2013-07-01

    Boiling Springs Lake (BSL) in Lassen Volcanic National Park, California, is North America's largest hot spring, but little is known about the physical, chemical, and biological features of the system. Using a remotely operated vessel, we characterized the bathymetry and near-surface temperatures at sub-meter resolution. The majority of the 1.2 ha, pH 2.2 lake is 10 m deep and 50-52 °C, but temperatures reach 93 °C locally. We extracted DNA from water and sediments collected from warm (52 °C) and hot (73-83 °C) sites separated by 180 m. Gene clone libraries and functional gene microarray (GeoChip 3.0) were used to investigate the BSL community, and uptake of radiolabeled carbon sources was used to assess the relative importance of heterotrophic vs. autotrophic production. Microbial assemblages are similar in both sites despite the strong temperature differential, supporting observations of a dynamic, convectively mixed system. Bacteria in the Actinobacteria and Aquificales phyla are abundant in the water column, and Archaea distantly related to known taxa are abundant in sediments. The functional potential appears similar across a 5-year time span, indicating a stable community with little inter-annual variation, despite the documented seasonal temperature cycle. BSL water-derived DNA contains genes for complete C, N, and S cycles, and low hybridization to probes for N and S oxidation suggests that reductive processes dominate. Many of the detected genes for these processes were from uncultivated bacteria, suggesting novel organisms are responsible for key ecosystem services. Selection imposed by low nutrients, low pH, and high temperature appear to result in low diversity and evenness of genes for key functions involved in C, N, and S cycling. Conversely, organic degradation genes appear to be functionally redundant, and the rapid assimilation of radiolabeled organic carbon into BSL cells suggests the importance of allochthonous C fueling heterotrophic production in the BSL C cycle.

  15. Biogeochemistry in the initial phase of the constructed catchment Chicken Creek

    Science.gov (United States)

    Schaaf, Wolfgang; Claudia, Zönnchen

    2014-05-01

    We studied biogeochemical processes over a period of 8 years at the constructed catchment Chicken Creek, NE Germany. The site with a size of 6 ha and defined boundary conditions serves as a research infrastructure to study feedback mechansims during early ecosystem development. Gypsum dissolution and decalcification were important processes controlling soil solution and surface water composition and element budgets of the catchment. With invading vegetation, different patches formed. Element transformation within these patches was studied in controlled microcosm experiments using soil from the catchment and labelled plant litter of dominating species. Litter from Lotus corniculatus with low C/N ratio increased decalcification due to faster decomposition and nitrification. Potassium leached from litter was almost completely retained in the sandy soils. These results were not mere additive effects of parent materials plus plant litter, but reflect differences in biogeochemical process intensities and could result in an increasing heterogeneity of soil properties, nutrient availability, and element leaching fluxes with time. Similar trends were recorded at the field site. Compared the the low organic carbon contents in the soil (< 2 mg g-1), DOC concentrations were high. Both 14C dating of field samples and 13C labelling in the microcosms indicated that old inherited carbon was the main source of DOC.

  16. Visualizing Microbial Biogeochemistry: NanoSIMS and Stable Isotope Probing (Invited)

    Science.gov (United States)

    Pett-Ridge, J.; Weber, P. K.

    2009-12-01

    Linking phylogenetic information to function in microbial communities is a key challenge for microbial ecology. Isotope-labeling experiments provide a useful means to investigate the ecophysiology of microbial populations and cells in the environment and allow measurement of nutrient transfers between cell types, symbionts and consortia. The combination of Nano-Secondary Ion Mass Spectrometry (NanoSIMS) analysis, in situ labeling and high resolution microscopy allows isotopic analysis to be linked to phylogeny and morphology and holds great promise for fine-scale studies of microbial systems. In NanoSIMS analysis, samples are sputtered with an energetic primary beam (Cs+, O-) liberating secondary ions that are separated by the mass spectrometer and detected in a suite of electron multipliers. Five isotopic species may be analyzed concurrently with spatial resolution as fine as 50nm. A high sensitivity isotope ratio ‘map’ can then be generated for the analyzed area. NanoSIMS images of 13C, 15N and Mo (a nitrogenase co-factor) localization in diazotrophic cyanobacteria show how cells differentially allocate resources within filaments and allow calculation of nutrient uptake rates on a cell by cell basis. Images of AM fungal hyphae-root and cyanobacteria-rhizobia associations indicate the mobilization and sharing (stealing?) of newly fixed C and N. In a related technique, “El-FISH”, stable isotope labeled biomass is probed with oligonucleotide-elemental labels and then imaged by NanoSIMS. In microbial consortia and cyanobacterial mats, this technique helps link microbial structure and function simultaneously even in systems with unknown and uncultivated microbes. Finally, the combination of re-engineered universal 16S oligonucleotide microarrays with NanoSIMS analyses may allow microbial identity to be linked to functional roles in complex systems such as mats and cellulose degrading hindgut communities. These newly developed methods provide correlated oligonucleotide, functional enzyme and metabolic image data and should help unravel the metabolic processes of complex microbial communities in soils, biofilms and aquatic systems.

  17. Autonomous Marine Robotic Technology Reveals an Expansive Benthic Bacterial Community Relevant to Regional Nitrogen Biogeochemistry.

    Science.gov (United States)

    Valentine, David L; Fisher, G Burch; Pizarro, Oscar; Kaiser, Carl L; Yoerger, Dana; Breier, John A; Tarn, Jonathan

    2016-10-06

    Benthic accumulations of filamentous, mat-forming bacteria occur throughout the oceans where bisulfide mingles with oxygen or nitrate, providing key but poorly quantified linkages between elemental cycles of carbon, nitrogen and sulfur. Here we used the autonomous underwater vehicle Sentry to conduct a contiguous, 12.5 km photoimaging survey of sea-floor colonies of filamentous bacteria between 80 and 579 m water depth, spanning the continental shelf to the deep suboxic waters of the Santa Barbara Basin (SBB). The survey provided >31 000 images and revealed contiguous, white-colored bacterial colonization coating > ∼80% of the ocean floor and spanning over 1.6 km, between 487 and 523 m water depth. Based on their localization within the stratified waters of the SBB we hypothesize a dynamic and annular biogeochemical zonation by which the bacteria capitalize on periodic flushing events to accumulate and utilize nitrate. Oceanographic time series data bracket the imaging survey and indicate rapid and contemporaneous nitrate loss, while autonomous capture of microbial communities from the benthic boundary layer concurrent with imaging provides possible identities for the responsible bacteria. Based on these observations we explore the ecological context of such mats and their possible importance in the nitrogen cycle of the SBB.

  18. Stable isotope fractionation at a glacial hydrothermal field: implications for biogeochemistry and biosignatures on Mars

    Science.gov (United States)

    Cousins, C.; Bowden, R.; Fogel, M.; Cockell, C.; Crawford, I.; Gunn, M.; Karlsson, M. T.; Thorsteinsson, T.

    2012-12-01

    Hydrothermal environments that arise through the interaction between volcanogenic heat and glacial ice are ideal sites for understanding microbial biogeochemical processes on Earth, and also potentially on Mars where similar volcano-cryosphere interactions are thought to have occurred in the past. The Kverkfjöll subglacial basaltic volcano in central Iceland is geographically isolated, with little influence from flora, fauna, and human activity. Major environmental inputs include geothermal heat, meltwater from ice and snow, and outgassing of CO2, H2S, and SO2. Large physiochemical gradients exist, from steaming fumaroles and boiling hydrothermal pools, to frozen geothermal ground and glacial ice. Stable isotope measurements of total organic carbon, total sulphur, and total nitrogen were coupled with metagenomic analysis of the residing microbial communities, with the aim to identify biogeochemical relationships and processes operating within the Kverkfjöll geothermal environment, and also to identify any isotopic biosignatures that could be preserved within geothermal sediments. This study focused on a variety of samples taken along a hot spring stream that fed into a large ice-confined geothermal lake. Samples analysed range from unconsolidated hot spring sediments, well-developed microbial mats, and dissolved sulphate from hot spring fluids. From the anoxic spring source, the stream water increases in dissolved oxygen, decreases in temperature, yet maintains a pH of ~4. The spring environment is dominated by dissolved sulphate (~2.3 mM), with lower levels of nitrate (~50 μM), phosphorus (~5μM), and ammonium (~1.5 μM). Stable S isotope analysis reveals a fractionation of ~3.2 ‰ between sediment sulphide (as pyrite; δ34S ~0‰), and dissolved water sulphate (δ34S ~3.2 ‰) consistently along the hot spring stream, indicating the presence of an active sulphur cycle, although not one dominated by sulphate reduction (e.g. very negative sulphide δ34S). This fractionation trend was absent within lake sediments, possibly due to a number of mixed sources feeding into the lake, in addition to the spring stream. δ13C in sediments becomes increasingly more negative going downstream, along with increasing removal of TOC. Microbial mats were largely similar with very positive C isotope ratios (δ13C -9.4 to -12.6 ‰) typical of sulphur oxidizing microbes. Bulk genomic DNA was extracted from sediments and mats in order to identify firstly the community composition via 454-pyrosequencing, and secondly the functional diversity within these physiochemically varied environments. This metagenomic data will be combined with stable isotope patterns to elucidate the metabolic potential of hydrothermal environments at Kverkfjöll, which can be used to infer potential biogeochemical pathways of signatures of such pathways on Mars in similar, past environments.

  19. Contrasting biogeochemistry of nitrogen in the Atlantic and Pacific oxygen minimum zones

    Directory of Open Access Journals (Sweden)

    E. Ryabenko

    2011-08-01

    Full Text Available We present new data for the stable isotope ratio of inorganic nitrogen species from the contrasting oxygen minimum zones (OMZs of the Eastern Tropical North Atlantic, south of Cape Verde, and the Eastern Tropical South Pacific off Peru. Differences in minimum oxygen concentration and corresponding N-cycle processes for the two OMZs are reflected in strongly contrasting δ15N distributions. Pacific surface waters are marked by strongly positive values for δ15N-NO3 reflecting fractionation associated with subsurface N-loss and partial NO3 utilization. This contrasts with negative values in NO3 depleted surface waters of the Atlantic which are lower than can be explained by N supply via N2 fixation. We suggest the negative values reflect inputs of nitrate, possibly transient, associated with deposition of Saharan dust. Strong signals of N-loss processes in the subsurface Pacific OMZ are evident in the isotope and N2O data, both of which are compatible with a contribution of canonical denitrification to overall N-loss. However the apparent N isotope fractionation factor observed is relatively low (εd = 11.4 ‰ suggesting an effect of influence from denitrification in sediments. Identical positive correlation of N2O vs. AOU for waters with oxygen concentrations [O2] > 50 μmol l−1 in both regions reflect a nitrification source. Sharp decrease in N2O concentrations is observed in the Pacific OMZ due to denitrification under oxygen concentrations O2 < 5 μmol l−1.

  20. Hierarchical and dynamic seascapes: A quantitative framework for scaling pelagic biogeochemistry and ecology

    Science.gov (United States)

    Kavanaugh, Maria T.; Hales, Burke; Saraceno, Martin; Spitz, Yvette H.; White, Angelicque E.; Letelier, Ricardo M.

    2014-01-01

    Comparative analyses of oceanic ecosystems require an objective framework to define coherent study regions and scale the patterns and processes observed within them. We applied the hierarchical patch mosaic paradigm of landscape ecology to the study of the seasonal variability of the North Pacific to facilitate comparative analysis between pelagic ecosystems and provide spatiotemporal context for Eulerian time-series studies. Using 13-year climatologies of sea surface temperature (SST), photosynthetically active radiation (PAR), and chlorophyll a (chl-a), we classified seascapes in environmental space that were monthly-resolved, dynamic and nested in space and time. To test the assumption that seascapes represent coherent regions with unique biogeochemical function and to determine the hierarchical scale that best characterized variance in biogeochemical parameters, independent data sets were analyzed across seascapes using analysis of variance (ANOVA), nested-ANOVA and multiple linear regression (MLR) analyses. We also compared the classification efficiency (as defined by the ANOVA F-statistic) of resultant dynamic seascapes to a commonly-used static classification system. Variance of nutrients and net primary productivity (NPP) were well characterized in the first two levels of hierarchy of eight seascapes nested within three superseascapes (R2 = 0.5-0.7). Dynamic boundaries at this level resulted in a nearly 2-fold increase in classification efficiency over static boundaries. MLR analyses revealed differential forcing on pCO2 across seascapes and hierarchical levels and a 33% reduction in mean model error with increased partitioning (from 18.5 μatm to 12.0 μatm pCO2). Importantly, the empirical influence of seasonality was minor across seascapes at all hierarchical levels, suggesting that seascape partitioning minimizes the effect of non-hydrographic variables. As part of the emerging field of pelagic seascape ecology, this effort provides an improved means of monitoring and comparing oceanographic biophysical dynamics and an objective, quantitative basis by which to scale data from local experiments and observations to regional and global biogeochemical cycles.

  1. Microbial communities and biogeochemistry in an area of Engraulis encrasicolus spawning in the Sicilian Channel

    Directory of Open Access Journals (Sweden)

    Rosabruna La Ferla

    2014-06-01

    The rates of production, hydrolysis and degradation activities were quite low, in agreement with the general oligotrophy of the area and in agreement with this findings, picophytoplankton contribution to total production amounted to over than 65%. In terms of metabolic activities, different spatial distributions were observed between the autotrophic and heterotrophic components. In particular, heterotrophic metabolism showed high values in the layer located below the thermocline and above the DCM. Concerning the enzymatic activities, total leucine aminopeptidase activity showed the highest rates, followed by alkaline phosphatase and beta-Glucosidase (Caruso et al., 2014. Distribution of the dissolved enzymatic activities acting on proteins varied widely along the column, accounting for 5 to 90% of the total enzymatic activity and always prevailed on dissolved b-GLU. Total enzymatic activity rates were comparable to those obtained in the oligotrophic zones of Ionian and Mediterranean Sea (Zaccone et al., 2012, while the analysis of the dissolved fraction was the first report for the Mediterranean. In conclusion, the multidisciplinary scientific approach used in this study depicted a complex picture of the study area evidencing a high heterogeneity and dynamism of plankton communities, probably associated to peculiar hydrology of this ecosystem. On the whole, the study area appeared to be characterized by a relatively efficient microbial food web. However, low trophic conditions were stressed by all the biological and biochemical patterns, suggesting an important role of heterotrophic processes in this area in the examined summer period. Consequently, how and how much the microbial web sustains fish reproduction and larval survival need a more comprehensive analysis and will be focused in further research.

  2. Approaches to characterizing biogeochemistry effects of groundwater and surface water interaction at the riparian interface

    Science.gov (United States)

    Groundwater-surface water interaction (GSI) in riparian ecosystems strongly influences biological activity that controls nutrient flux and processes. Shallow groundwater in riparian zones is a hot spot for nitrogen removal processes, a storage zone for solutes, and a target for ...

  3. Differences and implications in biogeochemistry from maximizing entropy production locally versus globally

    Directory of Open Access Journals (Sweden)

    J. J. Vallino

    2011-06-01

    Full Text Available In this manuscript we investigate the use of the maximum entropy production (MEP principle for modeling biogeochemical processes that are catalyzed by living systems. Because of novelties introduced by the MEP approach, many questions need to be answered and techniques developed in the application of MEP to describe biological systems that are responsible for energy and mass transformations on a planetary scale. In previous work we introduce the importance of integrating entropy production over time to distinguish abiotic from biotic processes under transient conditions. Here we investigate the ramifications of modeling biological systems involving one or more spatial dimensions. When modeling systems over space, entropy production can be maximized either locally at each point in space asynchronously or globally over the system domain synchronously. We use a simple two-box model inspired by two-layer ocean models to illustrate the differences in local versus global entropy maximization. Synthesis and oxidation of biological structure is modeled using two autocatalytic reactions that account for changes in community kinetics using a single parameter each. Our results show that entropy production can be increased if maximized over the system domain rather than locally, which has important implications regarding how biological systems organize and supports the hypothesis for multiple levels of selection and cooperation in biology for the dissipation of free energy.

  4. Differences and implications in biogeochemistry from maximizing entropy production locally versus globally

    Directory of Open Access Journals (Sweden)

    J. J. Vallino

    2011-01-01

    Full Text Available In this manuscript we investigate the use of the maximum entropy production (MEP principle for modeling biogeochemical processes that are catalyzed by living systems. Because of novelties introduced by the MEP approach, many questions need to be answered and techniques developed in the application of MEP to describe biological systems that are responsible for energy and mass transformations on a planetary scale. In previous work we introduce the importance of integrating entropy production over time to distinguish abiotic from biotic processes under transient conditions. Here we investigate the ramifications of modeling biological systems involving one or more spatial dimensions. When modeling systems with spatial dimensions, entropy production can be maximized either locally at each point in space asynchronously or globally over the system domain synchronously. We use a simple two-box model inspired by two-layer ocean models to illustrate the differences in local versus global entropy maximization. Synthesis and oxidation of biological structure is modeled using two autocatalytic reactions that account for changes in community kinetics using a single parameter each. Our results show that entropy production can be increased if maximized over the system domain rather than locally, which has important implications regarding how biological systems organize and supports the hypothesis for multiple levels of selection and cooperation in biology for the dissipation of free energy.

  5. Changes in soil biogeochemistry following disturbance by girdling and mountain pine beetles in subalpine forests.

    Science.gov (United States)

    Trahan, Nicole A; Dynes, Emily L; Pugh, Evan; Moore, David J P; Monson, Russell K

    2015-04-01

    A recent unprecedented epidemic of beetle-induced tree mortality has occurred in the lodgepole pine forests of Western North America. Here, we present the results of studies in two subalpine forests in the Rocky Mountains, one that experienced natural pine beetle disturbance and one that experienced simulated disturbance imposed through bole girdling. We assessed changes to soil microclimate and biogeochemical pools in plots representing different post-disturbance chronosequences. High plot tree mortality, whether due to girdling or beetle infestation, caused similar alterations in soil nutrient pools. During the first 4 years after disturbance, sharp declines were observed in the soil dissolved organic carbon (DOC) concentration (45-51 %), microbial biomass carbon concentration (33-39 %), dissolved organic nitrogen (DON) concentration (31-42%), and inorganic phosphorus (PO4(3-)) concentration (53-55%). Five to six years after disturbance, concentrations of DOC, DON, and PO4(3-) recovered to 71-140 % of those measured in undisturbed plots. Recovery was coincident with observed increases in litter depth and the sublitter, soil O-horizon. During the 4 years following disturbance, soil ammonium, but not nitrate, increased to 2-3 times the levels measured in undisturbed plots. Microbial biomass N increased in plots where increased ammonium was available. Our results show that previously observed declines in soil respiration following beetle-induced disturbance are accompanied by losses in key soil nutrients. Recovery of the soil nutrient pool occurs only after several years following disturbance, and is correlated with progressive mineralization of dead tree litter.

  6. Microbially-accelerated consolidation of oil sands tailings. Pathway II: solid phase biogeochemistry

    Directory of Open Access Journals (Sweden)

    Tariq eSiddique

    2014-03-01

    Full Text Available Consolidation of clay particles in aqueous tailings suspensions is a major obstacle to effective management of oil sands tailings ponds in northern Alberta, Canada. We have observed that microorganisms indigenous to the tailings ponds accelerate consolidation of mature fine tailings (MFT during active metabolism by using two biogeochemical pathways. In Pathway I, microbes alter porewater chemistry to indirectly increase consolidation of MFT. Here, we describe Pathway II comprising significant, direct and complementary biogeochemical reactions with MFT mineral surfaces. An anaerobic microbial community comprising Bacteria (predominantly Clostridiales, Synergistaceae and Desulfobulbaceae and Archaea (Methanolinea/Methanoregula and Methanosaeta transformed FeIII minerals in MFT to amorphous FeII minerals during methanogenic metabolism of an added organic substrate. Synchrotron analyses suggested that ferrihydrite (5Fe2O3. 9H2O and goethite (α-FeOOH were the dominant FeIII minerals in MFT. The formation of amorphous iron sulfide (FeS and possibly green rust entrapped and masked electronegative clay surfaces in amended MFT. Both Pathways I and II reduced the surface charge potential (repulsive forces of the clay particles in MFT, which aided aggregation of clays and formation of networks of pores, as visualized using cryo-scanning electron microscopy. These reactions facilitated the egress of porewater from MFT and increased consolidation of tailings solids. These results have large-scale implications for management and reclamation of oil sands tailings ponds, a burgeoning environmental issue for the public and government regulators.

  7. Impact of human interventions on nutrient biogeochemistry in the Pamba River, Kerala, India.

    Science.gov (United States)

    David, Shilly Elizabeth; Chattopadhyay, Mahamaya; Chattopadhyay, Srikumar; Jennerjahn, Tim C

    2016-01-15

    Anthropogenic inputs nowadays are the major source of nutrients to the coastal area. While a wealth of data exists from high latitude regions, little is known on the amount and composition of nutrient fluxes from densely populated tropical catchments. The South Indian Pamba River is a prime example in this respect because of its manifold human interventions such as the Sabarimala pilgrimage, the largest pilgrim centre in the world and agricultural practices. In order (i) to identify direct cause-effect relationships, (ii) to quantify land use specific nutrient inputs and (iii) to assess the respective impacts water was sampled along the river course during the pre monsoon, south west monsoon and north east monsoon periods in 2010 to 2012. Sampling segments were chosen according to prevailing land use. A socioeconomic survey on agricultural practices was conducted to collect information on the type, time and quantity of fertilizer application. Our results indicate (i) little human activities in the forest segment resulted in a low nutrient yield; (ii) pilgrim activities led to high ammonium and phosphate yields in the temple segment; (iii) specific fertilizer management resulted in moderate and maximum nitrate yields in the respective agriculture segments. Annual NPK fertilizer inputs to the catchment were 95 kg ha(-1) yr(-1).The average yield for the Pamba River catchment amounted to 3.5 kg ha(-1) yr(-1) of DIN and 0.2 kg ha(-1) yr(-1) of phosphate-P. As opposing predictions for densely-populated regions the N and P yields of the Pamba River are moderate to low on a global scale. It highlights the need for land use specific quantitative estimates from tropical regions in order to improve the global database and local water quality management.

  8. The sensitivity of soil O2 and redox biogeochemistry to landscape position and climate

    Science.gov (United States)

    Silver, W. L.; Ruan, L.; O'Connell, C.; Gutiérrez del Arroyo, O.

    2015-12-01

    Soil oxygen (O2) availability and associated redox dynamics are key drivers of carbon and nitrogen cycling and greenhouse gas emissions in terrestrial ecosystems. However, few studies have measured soil O2 availability, and even fewer have related this to biogeochemical cycling over space and time. Redox dynamics are likely to play a particularly important role in humid tropical forests characterized by high rainfall, near constant warm temperatures, high biological activity, and finely textured soils, all of which contribute to periodic O2 depletion throughout the soil profile. These ecosystems exhibit rapid C turnover and are a globally important source of the major greenhouse gases. We report on an extensive network of galvanic O2 sensors and time-domain reflectometry along topographic gradients in a lower montane wet tropical forest in Puerto Rico (n = 105 sensors). Within the sensor field we also installed three automated surface flux chambers in each topographic zone (ridge, slope and valley). A Cavity Ring-Down Spectroscopy (CRDS) gas analyzer was used to measure pseudo-continuous fluxes of CO2, N2O, and CH4. Soil O2 concentrations decrease nonlinearly from ridges to valleys along topographic gradients. Soil moisture was the best single predictor of soil O2 concentrations explaining over 50% of the variability in the data, even in these well-drained soils. Drought conditions dramatically altered soil O2 dynamics in both time and space, and showed that redox drivers differed by topographic position. Both ridges and slopes produced higher CO2 fluxes than valleys. Daily CH4 emissions went up to ~2000 g CH4 ha-1d-1 for valleys (hot spots and hot moments). Soil O2 dynamics also helped explain patterns in reactive Fe species and C storage, as well as pH along the catena. Our results highlight the potential for soil O2 concentrations as an integrator of biogeochemical dynamics in variable redox environments. They also provide a mechanism for identifying and exploring the role of hot spots and hot moments in space and time.

  9. The Biogeochemistry of Contaminant Groundwater Plumes Arising from Waste Disposal Facilities

    DEFF Research Database (Denmark)

    Bjerg, Poul Løgstrup; Albrechtsen, Hans-Jørgen; Kjeldsen, Peter;

    2014-01-01

    Landfills with solid waste are abundant sources of groundwater pollution all over the world. Old uncontrolled municipal landfills are often large, heterogeneous sources with demolition waste, minor fractions of commercial or industrial waste, and organic waste from households. Strongly anaerobic...... leachate with a high content of dissolved organic carbon, salts, and ammonium, as well as specific organic compounds and metals is released from the waste for decades or centuries. Landfill leachate plume hosts a variety of biogeochemical processes, which is the key to understand the significant potential...... at landfill sites. Finally, the potential chemical or ecological impact from landfills located in former wetlands or near surface water bodies may deserve attention in future studies....

  10. Biogeochemistry of hypersaline springs supporting a mid-continent marine ecosystem: an analogue for martian springs?

    Science.gov (United States)

    Grasby, Stephen E; Londry, Kathleen L

    2007-08-01

    Hypersaline springs that host unique mid-continent marine ecosystems were examined in central Manitoba, Canada. The springs originate from a reflux of glacial meltwater that intrudes into underlying bedrock and dissolved buried salt beds. Two spring types were distinguished based both on flow rate and geochemistry. High flow springs (greater than 10 L/s) hosted extensive marine microbial mats, which were dominated by algae but also included diverse microbes. These varied somewhat between springs as indicated by changes in profiles of fatty acid methyl esters. Culture studies confirmed the presence of sulfate-reducing bacteria in sediments at the high flow sites. In contrast, low flow springs were affected by solar evaporation, increasing salinity, and temperature. These low flow springs behaved more like closed nutrient-limited systems and did not support microbial mats. Direct comparison of the high and low flow springs revealed interesting implications for the potential to record biosignatures in the rock record. High flow springs have abundant, well-developed microbial mats, which desiccate and are cemented along the edges of the spring pools; however, the high mass flux overwhelms any geochemical signature of microbial activity. In contrast, the nutrient-limited low flow sites develop strong geochemical signatures of sulfate reduction, even in the absence of microbial mats, due to less dilution with the lower flows. Geochemical and physical evidence for life did not correlate with the abundance of microbial life but, rather, with the extent to which the biological system formed a closed ecosystem.

  11. Observations of nitrogen and phosphorus biogeochemistry in a surface flow constructed wetland.

    Science.gov (United States)

    Erler, Dirk V; Tait, Douglas; Eyre, Bradley D; Bingham, Michael

    2011-11-15

    Free surface water constructed wetlands (CWs) provide a buffer between domestic wastewater treatment plants and natural waterways. Understanding the biogeochemical processes in CWs is crucial to improve their performance. In this study we measured a range of water and sediment parameters, and biogeochemical processes, in an effort to describe the processing of nutrients within two wetland cells in series. As a whole the studied CW effectively absorbed both nitrogen (N) and phosphorus (P) emanating from the waste treatment plant. However the two individual cells showed marked differences related to the availability of oxygen within the water column and the sediments. In one cell we speculated that the prevalence of surface plant species reduced its ability to function as a net nutrient sink. Here we observed a build-up of sediment organic matter, sediment anoxia, a decoupling of nitrification-denitrification, and a flux of N and P out of the sediments to the overlying water. The availability of DO in the surface sediments of the second studied cell led to improved coupling between nitrification-denitrification and a net uptake of both NH4+ and PO4(3-). We hypothesise that the dominance of deeply rooted macrophytes in the second cell was responsible for the improved sediment quality.

  12. Biogeochemistry of selenium isotopes: processes, cycling and paleoenvironmental applications. (Utrecht Studies in Earth Sciences 24)

    OpenAIRE

    Mitchell, K.A.

    2012-01-01

    Selenium (Se) is an essential trace element, which, with multiple oxidation states and six stable isotopes, has been suggested as a potentially powerful environmental tracer and paleoenvironmental proxy. Chapter 1 provides a literature review of the Se cycle. While the Se cycle shares some similarities with the S cycle, there are major differences that become apparent from a synthesis of the existing literature, we therefore compare the oceanic cycles of Se and S in Chapter 2. The biogeochemi...

  13. Modeling Microbial Biogeochemistry from Terrestrial to Aquatic Ecosystems Using Trait-Based Approaches

    Science.gov (United States)

    King, E.; Molins, S.; Karaoz, U.; Johnson, J. N.; Bouskill, N.; Hug, L. A.; Thomas, B. C.; Castelle, C. J.; Beller, H. R.; Banfield, J. F.; Steefel, C. I.; Brodie, E.

    2014-12-01

    Currently, there is uncertainty in how climate or land-use-induced changes in hydrology and vegetation will affect subsurface carbon flux, the spatial and temporal distribution of flow and transport, biogeochemical cycling, and microbial metabolic activity. Here we focus on the initial development of a Genome-Enabled Watershed Simulation Capability (GEWaSC), which provides a predictive framework for understanding how genomic information stored in a subsurface microbiome affects biogeochemical watershed functioning, how watershed-scale processes affect microbial function, and how these interactions co-evolve. This multiscale framework builds on a hierarchical approach to multiscale modeling, which considers coupling between defined microscale and macroscale components of a system (e.g., a catchment being defined as macroscale and biogeofacies as microscale). Here, we report our progress in the development of a trait-based modeling approach within a reactive transport framework that simulates coupled guilds of microbes. Guild selection is driven by traits extracted from, and physiological properties inferred from, large-scale assembly of metagenome data. Meta-genomic, -transcriptomic and -proteomic information are also used to complement our existing biogeochemical reaction networks and contributes key reactions where biogeochemical analyses are unequivocal. Our approach models the rate of nutrient uptake and the thermodynamics of coupled electron donors and acceptors for a range of microbial metabolisms including heterotrophs and chemolitho(auto)trophs. Metabolism of exogenous substrates fuels catabolic and anabolic processes, with the proportion of energy used for each based upon dynamic intracellular and environmental conditions. In addition to biomass development, anabolism includes the production of key enzymes, such as nitrogenase for nitrogen fixation or exo-enzymes for the hydrolysis of extracellular polymers. This internal resource partitioning represents a trade-off against biomass formation and results in microbial population emergence across a fitness landscape. We use this model in simulations to explore the controls on community emergence and impact on rates of reactions that contribute to the cycling of carbon across distinct redox zones of an aquifer.

  14. The impact of electrogenic sulfur oxidation on the biogeochemistry of coastal sediments: A field study

    NARCIS (Netherlands)

    Van de Velde, S.; Lesven, L.; Burdorf, L.D.W.; Hidalgo-Martinez, S.; Geelhoed, J.S.; van Rijswijk, P.; Gao, Y.; Meysman, F.J.R.

    2016-01-01

    Electro-active sediments distinguish themselves from other sedimentary environments by the presence of microbiallyinduced electrical currents in the surface layer of the sediment. The electron transport is generated by metabolic activity oflong filamentous cable bacteria, in a process referred to as

  15. Thunderbolt in biogeochemistry: galvanic effects of lightning as another source for metal remobilization.

    Science.gov (United States)

    Schaller, Jörg; Weiske, Arndt; Berger, Frank

    2013-11-04

    Iron and manganese are relevant constituents of the earth's crust and both show increasing mobility when reduced by free electrons. This reduction is known to be controlled by microbial dissimilation processes. Alternative sources of free electrons in nature are cloud-to-ground lightning events with thermal and galvanic effects. Where thermal effects of lightning events are well described, less is known about the impact of galvanic lightning effects on metal mobilization. Here we show that a significant mobilization of manganese occurs due to galvanic effects of both positive and negative lightning, where iron seems to be unaffected with manganese being abundant in oxic forms in soils/sediments. A mean of 0.025 mmol manganese (negative lightning) or 0.08 mmol manganese (positive lightning) mobilization may occur. We suggest that lightning possibly influences biogeochemical cycles of redox sensitive elements in continental parts of the tropics/subtropics on a regional/local scale.

  16. Validating the scalability of soft X-ray spectromicroscopy for quantitative soil ecology and biogeochemistry research.

    Science.gov (United States)

    Dynes, James J; Regier, Tom Z; Snape, Ian; Siciliano, Steven D; Peak, Derek

    2015-01-20

    Synchrotron-based soft-X-ray scanning transmission X-ray microscopy (STXM) has the potential to provide nanoscale resolution of the associations among biological and geological materials. However, standard methods for how samples should be prepared, measured, and analyzed to allow the results from these nanoscale imaging and spectroscopic tools to be scaled to field scale biogeochemical results are not well established. We utilized a simple sample preparation technique that allows one to assess detailed mineral, metal, and microbe spectroscopic information at the nano- and microscale in soil colloids. We then evaluated three common approaches to collect and process nano- and micronscale information by STXM and the correspondence of these approaches to millimeter scale soil measurements. Finally, we assessed the reproducibility and spatial autocorrelation of nano- and micronscale protein, Fe(II) and Fe(III) densities in a soil sample. We demonstrate that linear combination fitting of entire spectra provides slightly different Fe(II) mineral densities compared to image resonance difference mapping but that difference mapping results are highly reproducible between among sample replicates. Further, STXM results scale to the mm scale in complex systems with an approximate geospatial range of 3 μm in these samples.

  17. Sulfur in the South Florida ecosystem: Distribution, sources, biogeochemistry, impacts, and management for restoration

    Science.gov (United States)

    Orem, W.; Gilmour, C.; Axelrad, D.; Krabbenhoft, D.; Scheidt, D.; Kalla, P.; McCormick, P.; Gabriel, M.; Aiken, G.

    2011-01-01

    Sulfur is broadly recognized as a water quality issue of significance for the freshwater Florida Everglades. Roughly 60% of the remnant Everglades has surface water sulfate concentrations above 1 mg l-1, a restoration performance measure based on present sulfate levels in unenriched areas. Highly enriched marshes in the northern Everglades have average sulfate levels of 60 mg l-1. Sulfate loading to the Everglades is principally a result of land and water management in South Florida. The highest concentrations of sulfate (average 60-70 mg l-1) in the ecosystem are in canal water in the Everglades Agricultural Area (EAA). Potential sulfur sourcesin the watershed are many, but geochemical data and a preliminary sulfur mass balance for the EAA are consistent with sulfur presently used in agricultural, and sulfur released by oxidation of organic EAA soils (including legacy agricultural applications and natural sulfur) as the primary sources of sulfate enrichment in the EAA canals. Sulfate loading to the Everglades increases microbial sulfate reduction in soils, leading to more reducing conditions, greater cycling of nutrients in soils, production of toxic sulfide, and enhanced methylmercury (MeHg) production and bioaccumulation. Wetlands are zones of naturally high MeHg production, but the combination of high atmospheric mercury deposition rates in South Florida and elevated sulfate loading leads to increased MeHg production and MeHg risk to Everglades wildlife and human consumers. Sulfate from the EAA drainage canals penetrates deep into the Everglades Water Conservation Areas, and may extend into Everglades National Park. Present plans to restore sheet flow and to deliver more water to the Everglades may increase overall sulfur loads to the ecosystem, and move sulfate-enriched water further south. However, water management practices that minimize soil drying and rewetting cycles can mitigate sulfate release during soil oxidation. A comprehensive Everglades restoration strategy should include reduction of sulfur loads as a goal because of the many detrimental impacts of sulfate on the ecosystem. Monitoring data show that the ecosystem response to changes in sulfate levels is rapid, and strategies for reducing sulfate loading may be effective in the near term. A multifaceted approach employing best management practices for sulfur in agriculture, agricultural practices that minimize soil oxidation, and changes to stormwater treatment areas that increase sulfate retention could help achieve reduced sulfate loads to the Everglades, with resulting benefits. Copyright ?? 2011 Taylor & Francis Group, LLC.

  18. Effects of Introduced Grasses, Grazing and Fire on Regional Biogeochemistry in Hawaii

    Science.gov (United States)

    Elmore, A. J.; Asner, G. P.

    2003-12-01

    African grasses introduced for grazing have expanded in geographic extent in mesic tropical systems of Hawaii and other regions of the world. Grassland expansion leads to increases in fire frequency, speeding woodland and forest destruction at greater geographic scales than occurs with grazing alone. At Pu'uwa'awa'a Ranch, Hawaii, restoration of the native woodland habitat has become a critical objective following the introduction and dominance of the African grass species Pennisetum clandestinum and P. setaceum. Grazing and grass-fueled fires have destroyed over 60% of the original forest. To stabilize these communities, managers must balance the combined effects of grazing and fire. Grazing reduces the recruitment success of native tropical trees, but grazing also reduces fire risk by moderating grass fuel conditions and restricting the extent and density of the most flammable grass species. Our study focuses on two questions: (1) What grazing intensity is necessary to change the fire conditions of a region given in situ soil and precipitation conditions? (2) Have long-term grazing conditions altered soil carbon and nitrogen stocks? We used high resolution imaging spectrometer data to measure photosynthetic and non-photosynthetic vegetation cover, analysis of soil carbon and nitrogen stocks, and measurements of plant community composition along gradients in grazing intensity. P. setaceum, the more flammable alien grass, was dominant where grazing intensity was low and at lower elevations where precipitation is low. The less flammable grass, P. clandestinum, occurred in regions of high grazing intensity and higher precipitation. Grazing influenced the dominance of P. setaceum and P. clandestinum only where precipitation and soil characteristics were suitable for both grasses to occur. At suitable sites, grazing reduced fire conditions through a species sift towards P. clandestinum. Soil carbon and nitrogen stocks decreased with grazing intensity, which was correlated with the fractional cover of P. setaceum. Soil carbon also increased with precipitation. These results show how grazing impacts fire conditions and soil chemistry through changes in species composition, and not through removal of carbon inputs (direct removal of biomass).

  19. Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico, St. Petersburg, FL

    Science.gov (United States)

    Robbins, L. L.; Coble, P. G.; Clayton, T. D.; Cai, W. J.

    2008-01-01

    Despite their relatively small surface area, ocean margins may have a significant impact on global biogeochemical cycles and, potentially, the global air-sea fluxes of carbon dioxide. Margins are characterized by intense geochemical and biological processing of carbon and other elements and exchange large amounts of matter and energy with the open ocean. The area-specific rates of productivity, biogeochemical cycling, and organic/inorganic matter sequestration are high in coastal margins, with as much as half of the global integrated new production occurring over the continental shelves and slopes (Walsh, 1991; Doney and Hood, 2002; Jahnke, in press). However, the current lack of knowledge and understanding of biogeochemical processes occurring at the ocean margins has left them largely ignored in most of the previous global assessments of the oceanic carbon cycle (Doney and Hood, 2002). A major source of North American and global uncertainty is the Gulf of Mexico, a large semi-enclosed subtropical basin bordered by the United States, Mexico, and Cuba. Like many of the marginal oceans worldwide, the Gulf of Mexico remains largely unsampled and poorly characterized in terms of its air-sea exchange of carbon dioxide and other carbon fluxes. The goal of the workshop was to bring together researchers from multiple disciplines studying terrestrial, aquatic, and marine ecosystems to discuss the state of knowledge in carbon fluxes in the Gulf of Mexico, data gaps, and overarching questions in the Gulf of Mexico system. The discussions at the workshop were intended to stimulate integrated studies of marine and terrestrial biogeochemical cycles and associated ecosystems that will help to establish the role of the Gulf of Mexico in the carbon cycle and how it might evolve in the face of environmental change.

  20. Contribution of collagen stable isotope biogeochemistry to the paleobiology of extinct endemic vertebrates from Tenerife (Canary Islands, Spain).

    Science.gov (United States)

    Bocherens, H; Michaux, J; Billiou, D; Castanet, J; Garcìa-Talavera, F

    2003-09-01

    The paleodiet and paleoenvironmental context of two extinct species from Tenerife island, one giant rat Canariomys bravoi and one giant lizard Gallotia goliath, have been investigated using carbon and nitrogen isotopic compositions of fossil bone collagen. Preliminary to this study, a calibration of the isotopic variations of bone collagen from modern Rat Rattus rattus, Rabbit Oryctolagus cuniculus and Lizard Gallotia galotti relative to environmental conditions on Tenerife Islands has been attempted. No clear relationship could be found between collagen delta13C and delta15N values and aridity; the only relevant factors seem to be seashore proximity for rat, and the relative amount of C3 and CAM plants. It seems that anthropic activities have interfered with the expected relationships between collagen isotopic compositions and environmental conditions. Most fossil specimens yielded well preserved collagen. The isotopic composition of giant rat and giant lizard collagen suggest a purely C3 environment, possibly more humid than today on Tenerife. Large ranges of nitrogen isotopic compositions, especially within giant rats, may be due to local environmental conditions. Further work is needed in order to provide more valuable paleobiological information in order to better understand the role of environmental factors in the evolution and extinction of insular endemic species on Tenerife.

  1. From the Belly of the Beast: Biogeochemistry and geomicrobiology of a fluid seep at Chimaera [Yanartas], Turkey

    Science.gov (United States)

    Woycheese, K. M.; Yargicoglu, E. N.; Cardace, D.; Meyer-Dombard, D. R.

    2012-12-01

    Serpentinization is proposed to support chemolithotrophic growth of microorganisms in surface and subsurface environments1. Abiotic CH4 production associated with terrestrial ophiolitic outcrops has been reported in southeastern Turkey2. The Yanartas (Chimaera) seep, located within the Tekirova ophiolite in Çirali, Antalya, Turkey, is one of the largest onshore CH4 seeps documented2-5. The seep consists of dozens of flames erupting from fractures within the ophiolite outcrop that burn continuously on CH4 (80-90% of gas composition2) produced by subsurface serpentinization reactions. Previous studies have focused on gas geochemistry from these seeps2, 4, 5. While past reports have not found active fluid seeps at Yanartas2, in February 2012, a fluid seep (possibly ephemeral) originating from a fracture was identified, which supported microbial mats over an outflow channel several m in length. This is the first investigation of the biogeochemical and geomicrobiological properties of this newly-discovered fluid seep. The fluid seep emits from a fracture that is actively burning, and travels down slope along the ophiolite outcrop for ~10 m. Sediment temperatures under the vent source were 50-60°C, while fluid emitting from the fracture was 18.5°C. The pH of the fluid at the vent source was 11.9, indicative of subterranean serpentinization. Approximately 7.3 m downstream, the pH dropped to 9.4, potentially due to meteoric water mixing. Fluid samples were collected along the outflow channel for major ion analysis, trace element analysis, dissolved inorganic carbon (DIC), and dissolved organic carbon (DOC). Biofilm and biomineralized microbial mats were collected for bulk C and N composition, 13C and 15N isotopes, and microscopy. Weight % total C (CT) in solids generally increases with distance from the source, while weight % organic C (Corg) decreases, reflective of a higher degree of carbonate biomineralization downstream. δ13C of solids indicates a general trend of increased 13C enrichment with distance from the source in both Corg and CT. δ15N becomes more positive with distance from the source, and does not suggest active nitrogen fixation along the outflow channel. Scanning electron microscopy (SEM) equipped with X-ray energy dispersive spectroscopy (XEDS) and X-ray diffraction (XRD) confirms that the biomineralized microbial mats are primarily composed of carbonates. Microbial samples were collected for cultivation, phylogenetic and function-based DNA analysis. Samples will be screened for methanotrophy, C fixation, and N cycling. Successful cultures have been obtained from Yanartas samples, demonstrating growth on a wide variety of carbon substrates (e.g. organic acids, yeast extract, peptone, and sugars). This is the first report of biofilms and surface fluids associated with serpentinization at the Yanartas seep. 1. McCollom, T.M. & W. Bach (2009) GCA. 73(3): 856-875 2. Etiope, G.; Schoell, M. & H. Hosgörmez (2011) EPSL. 310: 96-104 3. de Boer, J.Z.; Chanton, J. & M. Zeitlhöfler (2007) Geowissenshaftliche. 158(4): 997-1003 4. Hosgörmez, H. (2007) J Asian Earth Sci. 30: 131-141

  2. Hydrography and biogeochemistry of the north western Bay of Bengal and the north eastern Arabian Sea during winter monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Balachandran, K.K.; Laluraj, C.M.; Jyothibabu, R.; Madhu, N.V.; Muraleedharan, K.R.; Vijay, J.G.; Maheswaran, P.A.; Ashraf, T.T.M.; Nair, K.K.C.; Achuthankutty, C.T.

    in the Arabian Sea is driven by net heat loss from the ocean, whereas the Bay of Bengal does not contribute to such large heat loss to the atmosphere. It appears that the subduction of high saline Arabian Sea water mass is the mechanism behind the formation of a...

  3. Sediment biogeochemistry and microbial activity at natural hydrocarbon seeps and at sites impacted by anthropogenic hydrocarbon discharges

    Science.gov (United States)

    Joye, S. B.; Sibert, R.; Battles, J.; Fields, L.; Kleindienst, S.; Crespo-Medina, M.; Hunter, K.; Meile, C. D.; Montoya, J. P.

    2013-12-01

    Natural hydrocarbon seeps occur along the seafloor where geologic faults facilitate transfer of deeply sourced fluids enriched in gas, oil, and dissolved organic matter through shallow sediments and into the water column. At natural seeps, microbial populations specialize in hydrocarbon degradation and rates of microbial activity, including sulfate reduction and anaerobic oxidation of methane, can be extremely high. As a result, the biogeochemical signature of sediments near areas of active natural seepage is distinct: high concentrations of metabolic end products, such as dissolved inorganic carbon and hydrogen sulfide, abound, and often, high dissolved inorganic carbon concentrations result in the precipitation of authigenic carbonate minerals. We examined microbial processes and biogeochemical signatures at two natural seeps, Green Canyon 600 and Mississippi Canyon 118. Higher and more frequent seepage loci at the Green Canyon 600 site led to more widespread hotspots of elevated microbial activity and distinct geochemistry. However, rates of microbial activity were comparable at the two sites in areas of active hydrocarbon seepage. The microbial communities at the two sites were surprisingly different. The second group of sites was impacted by anthropogenic hydrocarbon discharges instead of natural seepage. One site, Oceanus 26, lies near the Deepwater Horizon/Macondo wellhead and was impacted by weathered oil sedimentation during the Macondo discharge. The second set of impacted sites, noted as Taylor Energy, lie near a sunken platform and compromised riser, which have together resulted in persistent hydrocarbon discharge to the adjacent oceanic system for more than 6 years. Rates of microbial activity in the upper sediments at Oceanus 26 were depressed relative to activity in the deeper layers, suggesting inhibition by the presence of weathered oil or an microbial community unable to weather the carbon available in the layer. At the Taylor energy site, sediment microbial activity from sites near the source of the discharge was distinct from control sites, 10 nm away, and not impacted by the persistent leak. Thus, the microbial communities present at natural hydrocarbon seeps are well adapted to metabolizing the hydrocarbons that persistently flux through the system. However, the microbial communities at anthropogenically-impacted sites exhibit a different response - inhibition of activity - to hydrocarbon addition. Together these data illustrate that anthropogenic hydrocarbon discharges exert clear impacts on the benthos that need to be studied in much more detail.

  4. ERSEM 15.06: a generic model for marine biogeochemistry and the ecosystem dynamics of the lower trophic levels

    Science.gov (United States)

    Butenschön, Momme; Clark, James; Aldridge, John N.; Icarus Allen, Julian; Artioli, Yuri; Blackford, Jeremy; Bruggeman, Jorn; Cazenave, Pierre; Ciavatta, Stefano; Kay, Susan; Lessin, Gennadi; van Leeuwen, Sonja; van der Molen, Johan; de Mora, Lee; Polimene, Luca; Sailley, Sevrine; Stephens, Nicholas; Torres, Ricardo

    2016-04-01

    The European Regional Seas Ecosystem Model (ERSEM) is one of the most established ecosystem models for the lower trophic levels of the marine food web in the scientific literature. Since its original development in the early nineties it has evolved significantly from a coastal ecosystem model for the North Sea to a generic tool for ecosystem simulations from shelf seas to the global ocean. The current model release contains all essential elements for the pelagic and benthic parts of the marine ecosystem, including the microbial food web, the carbonate system, and calcification. Its distribution is accompanied by a testing framework enabling the analysis of individual parts of the model. Here we provide a detailed mathematical description of all ERSEM components along with case studies of mesocosm-type simulations, water column implementations, and a brief example of a full-scale application for the north-western European shelf. Validation against in situ data demonstrates the capability of the model to represent the marine ecosystem in contrasting environments.

  5. Trace metal biogeochemistry in mangrove ecosystems: a comparative assessment of acidified (by acid sulfate soils) and non-acidified sites.

    Science.gov (United States)

    Nath, Bibhash; Birch, Gavin; Chaudhuri, Punarbasu

    2013-10-01

    The generation of acidity and subsequent mobilization of toxic metals induced by acid sulfate soils (ASSs) are known to cause severe environmental damage to many coastal wetlands and estuaries of Australia and worldwide. Mangrove ecosystems serve to protect coastal environments, but are increasingly threatened from such ASS-induced acidification due to variable hydrological conditions (i.e., inundation-desiccation cycles). However, the impact of such behaviors on trace metal distribution, bio-availability and accumulation in mangrove tissues, i.e., leaves and pneumatophores, are largely unknown. In this study, we examined how ASS-induced acidifications controlled trace metal distribution and bio-availability in gray mangrove (Avicennia marina) soils and in tissues in the Kooragang wetland, New South Wales, Australia. We collected mangrove soils, leaves and pneumatophores from a part of the wetland acidified from ASS (i.e., an affected site) for detailed biogeochemical studies. The results were compared with samples collected from a natural intertidal mangrove forest (i.e., a control site) located within the same wetland. Soil pH (mean: 5.90) indicated acidic conditions in the affected site, whereas pH was near-neutral (mean: 7.17) in the control site. The results did not show statistically significant differences in near-total and bio-available metal concentrations, except for Fe and Mn, between affected and control sites. Iron concentrations were significantly (p values≤0.001) greater in the affected site, whereas Mn concentrations were significantly (p values≤0.001) greater in the control site. However, large proportions of near-total metals were potentially bio-available in control sites. Concentrations of Fe and Ni were significantly (p values≤0.001) greater in leaves and pneumatophores of the affected sites, whereas Mn, Cu, Pb and Zn were greater in control sites. The degree of metal bio-accumulation in leaves and pneumatophores suggest contrasting hydrological behaviors and near-surface geochemical conditions favoring differential metal uptake by mangrove plants in the two sites.

  6. First autonomous bio-optical profiling float in the Gulf of Mexico reveals dynamic biogeochemistry in deep waters.

    Science.gov (United States)

    Green, Rebecca E; Bower, Amy S; Lugo-Fernández, Alexis

    2014-01-01

    Profiling floats equipped with bio-optical sensors well complement ship-based and satellite ocean color measurements by providing highly-resolved time-series data on the vertical structure of biogeochemical processes in oceanic waters. This is the first study to employ an autonomous profiling (APEX) float in the Gulf of Mexico for measuring spatiotemporal variability in bio-optics and hydrography. During the 17-month deployment (July 2011 to December 2012), the float mission collected profiles of temperature, salinity, chlorophyll fluorescence, particulate backscattering (bbp), and colored dissolved organic matter (CDOM) fluorescence from the ocean surface to a depth of 1,500 m. Biogeochemical variability was characterized by distinct depth trends and local "hot spots", including impacts from mesoscale processes associated with each of the water masses sampled, from ambient deep waters over the Florida Plain, into the Loop Current, up the Florida Canyon, and eventually into the Florida Straits. A deep chlorophyll maximum (DCM) occurred between 30 and 120 m, with the DCM depth significantly related to the unique density layer ρ = 1023.6 (R2 = 0.62). Particulate backscattering, bbp, demonstrated multiple peaks throughout the water column, including from phytoplankton, deep scattering layers, and resuspension. The bio-optical relationship developed between bbp and chlorophyll (R2 = 0.49) was compared to a global relationship and could significantly improve regional ocean-color algorithms. Photooxidation and autochthonous production contributed to CDOM distributions in the upper water column, whereas in deep water, CDOM behaved as a semi-conservative tracer of water masses, demonstrating a tight relationship with density (R2 = 0.87). In the wake of the Deepwater Horizon oil spill, this research lends support to the use of autonomous drifting profilers as a powerful tool for consideration in the design of an expanded and integrated observing network for the Gulf of Mexico.

  7. Biogeochemistry of mercury and methylmercury in sediment cores from Sundarban mangrove wetland, India--a UNESCO World Heritage Site.

    Science.gov (United States)

    Chatterjee, Mousumi; Canário, João; Sarkar, Santosh Kumar; Branco, Vasco; Godhantaraman, Nallamuthu; Bhattacharya, Bhaskar Deb; Bhattacharya, Asokkumar

    2012-09-01

    This study was performed to elucidate the distribution, concentration trend and possible sources of total mercury (Hg(T)) and methylmercury (MeHg) in sediment cores (levels in sediments could be explained by sediment transport by the tidal Hugli (Ganges) River that would dilute the Hg(T) values via sediment mixing processes. A broader variation of MeHg proportions (%) were also observed in samples suggesting that other environmental variables such as organic carbon and microbial activity may play a major role in the methylation process. An overall elevated concentration of Hg(T) in surface layers (0-4 cm) of the core is due to remobilization of mercury from deeper sediments. Based on the index of geoaccumulation (I (geo)) and low effects-range (ER-L) values, it is considered that the sediment is less polluted by Hg(T) and there is less ecotoxicological risk. The paper provides the first information of MeHg in sediments from this wetland environment and the authors strongly recommend further examination of Hg(T) fluxes for the development of a detailed coastal MeHg model. This could provide more refine estimates of a total flux into the water column.

  8. First autonomous bio-optical profiling float in the Gulf of Mexico reveals dynamic biogeochemistry in deep waters.

    Directory of Open Access Journals (Sweden)

    Rebecca E Green

    Full Text Available Profiling floats equipped with bio-optical sensors well complement ship-based and satellite ocean color measurements by providing highly-resolved time-series data on the vertical structure of biogeochemical processes in oceanic waters. This is the first study to employ an autonomous profiling (APEX float in the Gulf of Mexico for measuring spatiotemporal variability in bio-optics and hydrography. During the 17-month deployment (July 2011 to December 2012, the float mission collected profiles of temperature, salinity, chlorophyll fluorescence, particulate backscattering (bbp, and colored dissolved organic matter (CDOM fluorescence from the ocean surface to a depth of 1,500 m. Biogeochemical variability was characterized by distinct depth trends and local "hot spots", including impacts from mesoscale processes associated with each of the water masses sampled, from ambient deep waters over the Florida Plain, into the Loop Current, up the Florida Canyon, and eventually into the Florida Straits. A deep chlorophyll maximum (DCM occurred between 30 and 120 m, with the DCM depth significantly related to the unique density layer ρ = 1023.6 (R2 = 0.62. Particulate backscattering, bbp, demonstrated multiple peaks throughout the water column, including from phytoplankton, deep scattering layers, and resuspension. The bio-optical relationship developed between bbp and chlorophyll (R2 = 0.49 was compared to a global relationship and could significantly improve regional ocean-color algorithms. Photooxidation and autochthonous production contributed to CDOM distributions in the upper water column, whereas in deep water, CDOM behaved as a semi-conservative tracer of water masses, demonstrating a tight relationship with density (R2 = 0.87. In the wake of the Deepwater Horizon oil spill, this research lends support to the use of autonomous drifting profilers as a powerful tool for consideration in the design of an expanded and integrated observing network for the Gulf of Mexico.

  9. Sea-bed biogeochemistry and benthic foraminiferal bathymetric zonation on the slope of the northwest Gulf of Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Loubere, P. (Northern Illinois Univ., DeKalb, IL (United States)); Gary, A. (Unocal Science and Technology Division, Brea, CA (United States)); Lagoe, M. (Univ. of Texas, Austin, TX (United States))

    1993-10-01

    The bathymetric zonation of benthic Foraminiferal taxa in the northwest Gulf of Mexico is summarized and compared to several important environmental parameters measured in boxcores collected along a depth transect. The parameters are bottom water temperature, organic carbon flux, bottom water oxygen content, biogeochemical gradients within the sediments and sedimentation regime. The prominent Foraminiferal boundary between 170 and 200 m is associated with the position of the mudline in the northwest Gulf. Below this, assemblage changes are more gradational with water depth and, between 200 and 600 m, appear to be related to gradients in temperature, oxygen supply and organic carbon flux. Between 600 and 2000 m bathymetric zonation correlates to the organic carbon flux profile. An analysis of sediment pore water geochemistry and sedimentary features in the box-cores shows that there is a progressive change in the vertical distribution and character of potential microhabitats within the sediments down the slope of the northwest Gulf. From 250 to about 700 m water depth the biogenic structures observed in the sediments are abundant and complex, and the biogeochemical gradients in the sediments are steep. The visible complexity and chemical gradients gradually decrease with increasing water depth so that by 1000 m the anoxic boundary is deeper than 7 cm in our boxcores. At water depths greater than 1200 m the sediments are homogeneous, oxidized, hemipelagites. The published Foraminiferal bathymetric zonation of the N.W. Gulf appears to follow this gradient in sedimentary environments which must influence the generation of benthic Foraminiferal assemblages. The gradient is largely controlled by the organic carbon flux to the sea-bed. 42 refs., 8 figs., 3 tabs.

  10. Mechanistically-Based Field-Scale Models of Uranium Biogeochemistry from Upscaling Pore-Scale Experiments and Models

    Energy Technology Data Exchange (ETDEWEB)

    Tim Scheibe; Alexandre Tartakovsky; Brian Wood; Joe Seymour

    2007-04-19

    Effective environmental management of DOE sites requires reliable prediction of reactive transport phenomena. A central issue in prediction of subsurface reactive transport is the impact of multiscale physical, chemical, and biological heterogeneity. Heterogeneity manifests itself through incomplete mixing of reactants at scales below those at which concentrations are explicitly defined (i.e., the numerical grid scale). This results in a mismatch between simulated reaction processes (formulated in terms of average concentrations) and actual processes (controlled by local concentrations). At the field scale, this results in apparent scale-dependence of model parameters and inability to utilize laboratory parameters in field models. Accordingly, most field modeling efforts are restricted to empirical estimation of model parameters by fitting to field observations, which renders extrapolation of model predictions beyond fitted conditions unreliable. The objective of this project is to develop a theoretical and computational framework for (1) connecting models of coupled reactive transport from pore-scale processes to field-scale bioremediation through a hierarchy of models that maintain crucial information from the smaller scales at the larger scales; and (2) quantifying the uncertainty that is introduced by both the upscaling process and uncertainty in physical parameters. One of the challenges of addressing scale-dependent effects of coupled processes in heterogeneous porous media is the problem-specificity of solutions. Much effort has been aimed at developing generalized scaling laws or theories, but these require restrictive assumptions that render them ineffective in many real problems. We propose instead an approach that applies physical and numerical experiments at small scales (specifically the pore scale) to a selected model system in order to identify the scaling approach appropriate to that type of problem. Although the results of such studies will generally not be applicable to other broad classes of problems, we believe that this approach (if applied over time to many types of problems) offers greater potential for long-term progress than attempts to discover a universal solution or theory. We are developing and testing this approach using porous media and model reaction systems that can be both experimentally measured and quantitatively simulated at the pore scale, specifically biofilm development and metal reduction in granular porous media. The general approach we are using in this research follows the following steps: (1) Perform pore-scale characterization of pore geometry and biofilm development in selected porous media systems. (2) Simulate selected reactive transport processes at the pore scale in experimentally measured pore geometries. (3) Validate pore-scale models against laboratory-scale experiments. (4) Perform upscaling to derive continuum-scale (local darcy scale) process descriptions and effective parameters. (5) Use upscaled models and parameters to simulate reactive transport at the continuum scale in a macroscopically heterogeneous medium.

  11. Biogeochemistry and plant physiological traits interact to reinforce patterns of post-fire dominance in boreal forests

    Science.gov (United States)

    Shenoy, A.; Kielland, K.; Johnstone, J. F.

    2011-12-01

    Increases in the frequency, extent, and severity of fire in the North American boreal region are projected to continue under a warming climate and are likely to be associated with changes in future vegetation composition. In interior Alaska, fire severity is linked to the relative dominance of deciduous versus coniferous canopy species. Severely burned areas have high levels of deciduous recruitment and subsequent stand dominance, while lightly burned areas exhibit black spruce self-replacement. To elucidate potential mechanisms by which differential fire severity results in differential post-fire vegetation development, we examined changes in soil nitrogen (N) supply (NO3- and NH4+) and in situ 15N uptake by young aspen (Populus tremuloides) and black spruce (Picea mariana) trees growing in lightly and severely burned areas. We hypothesized that (a) soil nitrate supply would be higher in severely burned sites and (b) since conifers have been shown to have a reduced physiological capacity for NO3- uptake, aspen would display greater rates of NO3- uptake than spruce in severely burned sites. Our results suggested that the composition and magnitude of inorganic N supply 14 years after the fire was nearly identical in high-severity and low-severity sites, and nitrate represented nearly 50% of the supply. However, both aspen and spruce took up substantially more NH4+-N than NO3- -N regardless of fire severity. Surprisingly, spruce exhibited only a moderately lower rate of NO3- uptake (μg N/g root-1h-1) than aspen. At the stand level, aspen took up nearly an order-of-magnitude more N per hectare in severely burned sites compared to lightly burned sites, while spruce exhibited the opposite pattern of N uptake with respect to fire severity. Whereas ammonium appeared to be preferred by both species, nitrate represented a larger component of N uptake (based on the NO3-:NH4+ uptake ratio) in aspen (0.7) than in spruce (0.4). We suggest that these species-specific differences in N preference coupled with their respective physiological response to fire severity represent a positive feedback loop that reinforce the opposing stand dominance patterns that have developed at the two ends of the fire severity spectrum. Shifts in forest composition from the current dominance by conifers to a future landscape dominated by deciduous forest are of concern due to impacts on climate-albedo feedbacks, forest productivity, ecosystem carbon storage, and wildlife habitat use.

  12. High-Speed Limnology: A Sensor Platform for Investigating Processes and Spatial Variability in Hydrology and Biogeochemistry

    Science.gov (United States)

    Crawford, J. T.; Loken, L. C.; Casson, N. J.; Stanley, E. H.; Striegl, R. G.; Winslow, L.

    2014-12-01

    Inland water sensor data acquisition is dominated by a fixed station reference frame, where water passes over a stationary sensor. These single point measurements are useful in understanding temporal patterns, but the assumptions needed to apply them to entire ecosystems are rarely tested. No single location within a stream reach or on a lake's surface appropriately represents the inherent spatial variability, and extrapolations from these single points should be used with caution. In this context, we illustrate the approach of "taking the sensor to the water," in either a quasi-Lagrangian or spatially explicit view. We present a sensor platform capable of rapid and dynamic (0-60 km hr-1) spatial sampling in navigable waters using multiple flow-through systems and a unique intake manifold connected to a small boat. We highlight data collected on medium-sized lakes (1.6 to 39 km2), and a heterogeneous reach of the upper Mississippi River (35 km). We use these datasets to infer hypolimnetic upwelling sensed from temperature and dissolved oxygen in a eutrophic lake and estimate the relative contributions of riverine and littoral methane production and epilimnetic transport. In addition to mapping the mixing dynamics of surface waters, we can estimate biogeochemical transformations by comparing multiple sensor outputs and applying conservative mixing models. We present apparent loss of riverine fDOM entering a eutrophic lake, effects of a constructed fringing wetland on solutes and nitrate cycling in a large river reach. This relatively simple platform uses sensors designed for the traditional fixed reference framework and will contribute to a new understanding of the spatial heterogeneity inherent in aquatic ecosystems.

  13. Nitrate isotopes illuminate the black box of paddy soil biogeochemistry: water and carbon management control nitrogen sources and sinks

    Science.gov (United States)

    Wells, N. S.; Clough, T. J.; Johnson-Beebout, S. E.; Buresh, R. J.

    2010-12-01

    Accurate prediction of the available nitrogen (N) pool in submerged paddy soils is needed in order to produce rice, one of the world’s most essential crops, in an economically and environmentally sustainable manner. By applying emerging nitrate dual-isotope (δ15N- δ18O- NO3-) techniques to paddy systems, we were able to obtain a unique process-level quantification of the synergistic impacts of carbon (C) and water management on N availability. Soil and water samples were collected from fallow experimental plots, with or without organic C amendments, that were maintained under 1 of 3 different hydrologic regimens: continuously submerged, water excluded, or alternate wetting and drying. In continuously submerged soils the δ15N-NO3- : δ18O-NO3- signal of denitrification was not present, indicating that there was no N attenuation. Biological nitrogen fixation (BNF) was the dominant factor in defining the available N pool under these conditions, with δ15N-NO3- approaching atmospheric levels as size of the pool increased. Using an isotope-based pool-mixing model, it was calculated that 10±2 µg N g-1 soil were contributed by BNF during the fallow. A lack of BNF combined with removal via denitrification (δ15N-NO3- : δ18O-NO3- = 1) caused relatively lower available N levels in dried and alternate wetting-drying soils during this period. Magnitude and net impact of denitrification was defined by the extent of drying and C availability, with rice straw C additions driving tighter coupling of nitrification and denitrification (δ15N:δ18O straw amendments ultimately retained a significantly larger available N pool due to enhanced input from soil organic matter. These findings underline the necessity of, and validate a new means for, accurate quantification micro-scale biogeochemical interactions for developing farm-scale management practices that can maximize N storage and minimize environmentally undesirable losses.

  14. Effects of ozone on net primary production and carbon sequestration in the conterminous United States using a biogeochemistry model

    Science.gov (United States)

    Felzer, B.; Kicklighter, D.; Melillo, J.; Wang, C.; Zhuang, Q.; Prinn, R.

    2004-07-01

    The effects of air pollution on vegetation may provide an important control on the carbon cycle that has not yet been widely considered. Prolonged exposure to high levels of ozone, in particular, has been observed to inhibit photosynthesis by direct cellular damage within the leaves and through possible changes in stomatal conductance. We have incorporated empirical equations derived for trees (hardwoods and pines) and crops into the Terrestrial Ecosystem Model to explore the effects of ozone on net primary production (NPP) and carbon sequestration across the conterminous United States. Our results show a 2.6 6.8% mean reduction for the United States in annual NPP in response to modelled historical ozone levels during the late 1980s-early 1990s. The largest decreases (over 13% in some locations) occur in the Midwest agricultural lands, during the mid-summer when ozone levels are highest. Carbon sequestration since the 1950s has been reduced by 18 38 Tg C yr1 with the presence of ozone. Thus the effects of ozone on NPP and carbon sequestration should be factored into future calculations of the United States' carbon budget.

  15. The biogeochemistry of carbon cycle in summer of the Prydz Bay,Antarctic Ⅰ :Characteristics of DOC distribution

    Institute of Scientific and Technical Information of China (English)

    扈传昱; 潘建明; 刘小涯; 张海生

    2004-01-01

    The distributions and changes of dissolved organic carbon in the Prydz Bay and out open sea were investigated during CHINARE-15 ( the 15th Chinese National Antarctic Research Expedition). The results showed that the content of DOC was higher in the Prydz Bay and outer open sea compared to those typical of surface oceanic levels ( 70-80 μM) , average content of DOC in the surface water was 102.32 μM,the range was 68.23-125.92 μM. The vertical distribution of DOC in the water column was similar to many ocean sites, that is to say, the content of upper water is higher than deep water, a subsurface maximum persisted between 25-50 m. The DOC pool in the Prydz Bay were consisted with labile, semi-labile and refractory pools, in which refractory pools was mainly part. The concentration of refractory DOC was 92.34 and 76.89 μM in Prydz Bay and outer open sea, and account 77% and 82% for total DOC, respectively.

  16. FINAL REPORT: Mechanistically-Base Field Scale Models of Uranium Biogeochemistry from Upscaling Pore-Scale Experiments and Models

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Brian D.

    2013-11-04

    Biogeochemical reactive transport processes in the subsurface environment are important to many contemporary environmental issues of significance to DOE. Quantification of risks and impacts associated with environmental management options, and design of remediation systems where needed, require that we have at our disposal reliable predictive tools (usually in the form of numerical simulation models). However, it is well known that even the most sophisticated reactive transport models available today have poor predictive power, particularly when applied at the field scale. Although the lack of predictive ability is associated in part with our inability to characterize the subsurface and limitations in computational power, significant advances have been made in both of these areas in recent decades and can be expected to continue. In this research, we examined the upscaling (pore to Darcy and Darcy to field) the problem of bioremediation via biofilms in porous media. The principle idea was to start with a conceptual description of the bioremediation process at the pore scale, and apply upscaling methods to formally develop the appropriate upscaled model at the so-called Darcy scale. The purpose was to determine (1) what forms the upscaled models would take, and (2) how one might parameterize such upscaled models for applications to bioremediation in the field. We were able to effectively upscale the bioremediation process to explain how the pore-scale phenomena were linked to the field scale. The end product of this research was to produce a set of upscaled models that could be used to help predict field-scale bioremediation. These models were mechanistic, in the sense that they directly incorporated pore-scale information, but upscaled so that only the essential features of the process were needed to predict the effective parameters that appear in the model. In this way, a direct link between the microscale and the field scale was made, but the upscaling process helped inform potential users of the model what kinds of information would be needed to accurately characterize the system.

  17. Elucidating the fate, transport and processes controlling carbon on the landscape: Biogeochemistry tools for the 21st century

    Science.gov (United States)

    McFarlane, K. J.; Keiluweit, M.; Nico, P. S.; Ognibene, T.; Mayali, X.; Nuccio, E.; Weber, P. K.; Pett-Ridge, J.; Guilderson, T. P.

    2013-12-01

    Globally, more carbon is stored belowground as soil organic matter than in terrestrial vegetation and the atmosphere combined. A critical scientific question is how soils serve as sources and sinks for atmospheric carbon dioxide (CO2) and how these sinks will evolve with expected changes in atmospheric CO2 concentrations, climate, and land-use. Carbon initially enters belowground soil pools as plant detritus, roots, and root exudates. Once in the soil, this organic matter serves as a substrate for decomposer organisms including soil animals, bacteria, and fungi. Most of this carbon is consumed and respired as CO2, but some is converted to microbial biomass and byproducts, which may leave the soil as dissolved organic carbon, be used as a substrate by other microbes, or be stabilized within the soil mineral matrix. Mechanisms that result in the stabilization of soils include: climate stabilization, physical protection within aggregates and organo-mineral complexes, and protection of potential substrates due to physiochemical barriers. These processes, which span broad temporal and spatial scales, are poorly constrained in many dynamic land surface models. At LLNL, we have developed a suite of analytical tools that allow us to follow the movement of carbon at the cell to landscape scale, including: ';Chip-SIP', ';STXM-SIMS', and new sample interfaces for accelerator mass spectrometry (AMS). Experiments, field-based and in vivo, allow us to further the mechanistic understanding of factors that control the fate, transport, and sequestration potential of belowground carbon. The Chip-SIP approach allows us to interrogate which microbial species in a complex community incorporate specific substrates (e.g. cellulose) in order to understand the production of biofuels and better elucidate energy and carbon transfers in wetlands and soils. To disentangle the complex interactions at soil-microbial-film-mineral interfaces with minimal disruption we are using a combination of high-resolution microspectroscopy (STXM-NEXAFS), electron microscopy (SEM), and nano-scale imaging mass spectrometry (nanoSIMS) collectively known as STXM-SIMS. This approach allows us to track labeled litter, exudates and microbial necromass onto microaggregate surfaces and elucidate how organic matter source and environmental conditions influences the physical and molecular fate of soil organic matter. Isotopic characterization (14C, 13C, 2H) of CH4, CO2, dissolved organic carbon (DOC) and physical sources of carbon provide the mechanistic fingerprints of the biogeochemical pathways that cycle carbon through the landscape. Building on our expertise in accelerator mass spectrometry (AMS), we are developing methods for 'direct injection' of CO2 for AMS-14C analyses. Our initial focus has been on a liquid-sample (HPLC) sample interface. The ability to handle liquid samples and continuous flows of liquid will enable more widespread and routine use of AMS in biological and environmental applications. Applied examples of these novel techniques, addressing critical questions in the biogeosciences, will be presented.

  18. Exopolymer alteration of physical properties of sea ice and implications for ice habitability and biogeochemistry in a warmer Arctic.

    Science.gov (United States)

    Krembs, Christopher; Eicken, Hajo; Deming, Jody W

    2011-03-01

    The physical properties of Arctic sea ice determine its habitability. Whether ice-dwelling organisms can change those properties has rarely been addressed. Following discovery that sea ice contains an abundance of gelatinous extracellular polymeric substances (EPS), we examined the effects of algal EPS on the microstructure and salt retention of ice grown from saline solutions containing EPS from a culture of the sea-ice diatom, Melosira arctica. We also experimented with xanthan gum and with EPS from a culture of the cold-adapted bacterium Colwellia psychrerythraea strain 34H. Quantitative microscopic analyses of the artificial ice containing Melosira EPS revealed convoluted ice-pore morphologies of high fractal dimension, mimicking features found in EPS-rich coastal sea ice, whereas EPS-free (control) ice featured much simpler pore geometries. A heat-sensitive glycoprotein fraction of Melosira EPS accounted for complex pore morphologies. Although all tested forms of EPS increased bulk ice salinity (by 11-59%) above the controls, ice containing native Melosira EPS retained the most salt. EPS effects on ice and pore microstructure improve sea ice habitability, survivability, and potential for increased primary productivity, even as they may alter the persistence and biogeochemical imprint of sea ice on the surface ocean in a warming climate.

  19. Field Continuous Measurement of Dissolved Gases with a CF-MIMS: Applications to the Physics and Biogeochemistry of Groundwater Flow.

    Science.gov (United States)

    Chatton, Eliot; Labasque, Thierry; de La Bernardie, Jérôme; Guihéneuf, Nicolas; Bour, Olivier; Aquilina, Luc

    2017-01-17

    In the perspective of a temporal and spatial exploration of aquatic environments (surface and groundwater), we developed a technique for field continuous measurements of dissolved gases with a precision better than 1% for N2, O2, CO2, He, Ar, 2% for Kr, 8% for Xe, and 3% for CH4, N2O and Ne. With a large resolution (from 1 × 10(-9) to 1 × 10(-2) ccSTP/g) and a capability of high frequency analysis (1 measure every 2 s), the CF-MIMS (Continuous Flow Membrane Inlet Mass Spectrometer) is an innovative tool allowing the investigation of a large panel of hydrological and biogeochemical processes in aquatic systems. Based on the available MIMS technology, this study introduces the development of the CF-MIMS (conception for field experiments, membrane choices, ionization) and an original calibration procedure allowing the quantification of mass spectral overlaps and temperature effects on membrane permeability. This study also presents two field applications of the CF-MIMS involving the well-logging of dissolved gases and the implementation of groundwater tracer tests with dissolved (4)He. The results demonstrate the analytical capabilities of the CF-MIMS in the field. Therefore, the CF-MIMS is a valuable tool for the field characterization of biogeochemical reactivity, aquifer transport properties, groundwater recharge, groundwater residence time and aquifer-river exchanges from few hours to several weeks experiments.

  20. The role of wildfires and forest succession in stream biogeochemistry within the continuous permafrost zone of Central Siberia

    Science.gov (United States)

    Prokushkin, Anatoly

    2016-04-01

    Wildfires transform boreal and subarctic forested landscapes leading to the changes in organic matter and inorganic nutrient turnover in terrestrial ecosystems. To get an insight to the fire effect on C fluxes and general hydrochemical characteristics of streams draining continuous permafrost terrains of Central Siberian Plateau (64o N 100o E), we have selected the chronosequence of basins (n = 17) which were severely affected by fires (>80% of basin area) in the time range from 1 to 116 years ago. Stream waters were sampled continuously during frost free seasons (May-September) of 2006-2015. Four streams have been equipped with water level, temperature and conductivity probes for continuous monitoring. The strongest negative effect of wildfires on dissolved organic carbon (DOC) concentrations in streams has occurred right after a fire event, and minimum mean annual concentrations of DOC appeared between 15 and 20 years elapsed after a fire. The most pronounced decrease in DOC concentrations during an annual cycle found in freshet period (May-June) and summer-fall storm events: differences of DOC concentrations among "intact" (>100 years after fire) and recent fire basins (active layer thickness (ALT) within analyzed watersheds have demonstrated that fire-driven deepening of ALT results in increasing stream inorganic compounds concentrations. The inverse relationship found between DOC and ALT might be attributed to deeper infiltration of solutions, sorption of DOC on clay minerals, and an increasing rate of DOC microbiological mineralization to CO2 due to increased soil temperatures. Post-fire forest recovery and, particularly, the accumulation of organic mater in the moss-lichen layer and soil organic horizon on watersheds accounted for increasing mean DOC concentrations in the streams. In opposite, increased insulation of soils by organic matter accumulating on the soil surface leads to steadily decreasing ALT and constrains an infiltration of solutes to subsoil. As a result, inorganic solute loading to stream channels is tended to decrease during post-fire forest succession in permafrost affected terrains.

  1. Nitrogen biogeochemistry in urban wetlands and bioretention systems: The evolving roles of urban stormwater management practices (Invited)

    Science.gov (United States)

    Stander, E. K.; Borst, M.; Ehrenfeld, J. G.; O'Connor, T. P.; Rowe, A. A.

    2009-12-01

    Traditional stormwater management practices, designed and constructed to rapidly and efficiently route runoff away from established infrastructure, have resulted in the disruption of natural drainage patterns in urban landscapes. The modified in-stream flow incises urban streams and reduces regional groundwater recharge, thus altering hydrologic patterns and regimes in urban wetlands and riparian zones. Water table dynamics and in situ nitrogen cycling processes were quantified in 14 palustrine, forested wetlands and correlated with watershed-scale land cover metrics in urban northern New Jersey. Variability in nitrogen cycling process rates was, in some cases, explained by altered hydrological regimes. However, land cover and hydrologic characteristics did not always exhibit the predicted effects, as demonstrated by dry and/or flashy water tables in less developed watersheds and denitrification rates that did not always reflect hydrological conditions. Inorganic nitrogen inputs and outputs were characterized in throughfall and soil leachate in nine of the 14 wetlands. Atmospheric nitrogen deposition rates were higher in wetlands located in more impervious and densely populated urban sub-watersheds, but nitrate losses through leaching were generally low and did not correlate with landscape-level descriptors of urban intensity. Two wetlands did display net loss of nitrate, and the results of dual isotope analysis suggested the direct pass-through of atmospheric nitrate on four sampling dates in two sites; these findings point to decreased nitrate retention capacity in some urban wetlands. New stormwater management practices designed to mimic natural drainage patterns are currently being developed and implemented in existing urban watersheds and new developments. These practices, which include rain gardens, pervious pavement, and green roofs, are intended to reduce peak flows to urban streams and, in many cases, also provide water quality functions. Rain gardens in particular have a documented ability to remove heavy metals and phosphorus from urban stormwater runoff, but their coarse-textured, low organic matter content soils are less able to remove nitrate through denitrification. Research at the US Environmental Protection Agency explores the use of media carbon amendments and deep zones of saturation to facilitate denitrification by providing labile carbon and anoxic conditions in experimental rain garden mesocosms. Initial results highlight the importance of conducting bench-scale testing of bioretention media before installation in full-scale, working rain gardens, particularly when media characteristics have been modified to promote stressor removal. If these low impact development practices can increase groundwater recharge and reduce stream incision, natural hydrologic regimes may be restored to urban wetlands and riparian zones.

  2. Biogeochemistry of N, P and SI in the Gulf of Riga surface sediments: Implications of seasonally changing factors

    DEFF Research Database (Denmark)

    Aigars, Juris; Dalsgaard, Tage; Poikane, Rita;

    2015-01-01

    dependency from seasonally fluctuating near-bottom water oxygen concentration levels. At the same time, clear temperature impact could be detected only in case of oxygen consumption, denitrification rates and fluxes of dissolved organic nitrogen. The seasonally increasing near-bottom water temperature seems......A seasonal study of sediment–water nutrient fluxes and denitrification rates was conducted at two sites in the Gulf of Riga, Baltic Sea, located at 44 and 45 m depth. The sediment was muddy with a total carbon content of 4.83–5.16 mmol g−1 dry weight and inhabited by Marenzelleria spp., 10–130 ind...... m−2, and Crustacea, 70–120 ind m−2. The near-bottom water temperature and oxygen concentration varied from 3 to 9 °C and from 122 to 394 µM, respectively, during the study. The oxygen and nutrient fluxes as well as denitrification that was sustained by nitrates from water column showed clear...

  3. Exploring the impact of agriculture on nitrogen and phosphorus biogeochemistry in global rivers during the twentieth century (Invited)

    Science.gov (United States)

    Bouwman, L.; Beusen, A.; Van Beek, L. P.

    2013-12-01

    Nutrients are transported from land to sea through the continuum formed by soils, groundwater, riparian zones, floodplains, streams, rivers, lakes, and reservoirs. The hydrology, ecology and biogeochemical processing in each of these components are strongly coupled and result in retention of a significant fraction of the nutrients transported. This paper analyzes the global changes in nutrient biogeochemical processes and retention in rivers during the past century (1900-2000); this period encompasses dramatic increases in human population and economic human activities including agriculture that have resulted in major changes in land use, nutrient use in agriculture, wastewater flows and human interventions in the hydrology (1). We use the hydrological PCR-GLOBWB model (2) for the period 1900-2000, including climate variability and the history of dam construction and land use conversion. Global agricultural and natural N and P soil budgets for the period 1900-2000 are the starting point to simulate nutrient flows from the soil via surface runoff and leaching through the groundwater system and riparian zones. In-stream processes are described with the nutrient spiraling concept. In the period 1900-2000, the global soil N budget surplus (inputs minus withdrawal in harvested crops) for agricultural and natural ecosystems increased from 118 to 202 Tg yr-1, and the global P budget increased from Philosophical Transactions of the Royal Society B: Biological Sciences. 2013;368(20130112). 2. Van Beek LPH, Wada Y, Bierkens MFP. Global monthly water stress: 1. Water balance and water availability. Water Resour Res. 2011;47(7):W07517.

  4. "Advances in Linked Air Quality, Farm Management and Biogeochemistry Models to Address Bidrectional Ammonia Flux in CMAQ"

    Science.gov (United States)

    Recent increases in anthropogenic inputs of nitrogen to air, land and water media pose a growing threat to human health and ecosystems. Modeling of air-surface N flux is one area in need of improvement. Implementation of a linked air quality and cropland management system is de...

  5. Advances in Linked Air Quality, Farm Management and Biogeochemistry Models to Address Bidirectional Ammonia Flux in CMAQ

    Science.gov (United States)

    Recent increases in anthropogenic inputs of nitrogen to air, land and water media pose a growing threat to human health and ecosystems. Modeling of air-surface N flux is one area in need of improvement. Implementation of a linked air quality and cropland management system is de...

  6. Deglacial variability in Okhotsk Sea Intermediate Water ventilation and biogeochemistry: Implications for North Pacific nutrient supply and productivity

    Science.gov (United States)

    Lembke-Jene, Lester; Tiedemann, Ralf; Nürnberg, Dirk; Kokfelt, Ulla; Kozdon, Reinhard; Max, Lars; Röhl, Ursula; Gorbarenko, Sergey A.

    2017-03-01

    The modern North Pacific plays a critical role in marine biogeochemical cycles, as an oceanic sink of CO2 and by bearing some of the most productive and least oxygenated waters of the World Ocean. The capacity to sequester CO2 is limited by efficient nutrient supply to the mixed layer, particularly from deeper water masses in the Pacific's subarctic and marginal seas. The region is in addition only weakly ventilated by North Pacific Intermediate Water (NPIW), which receives its characteristics from Okhotsk Sea Intermediate Water (OSIW). Here, we present reconstructions of intermediate water ventilation and productivity variations in the Okhotsk Sea that cover the last glacial termination between eight and 18 ka, based on a set of high-resolution sediment cores from sites directly downstream of OSIW formation. In a multi-proxy approach, we use total organic carbon (TOC), chlorin, biogenic opal, and CaCO3 concentrations as indicators for biological productivity. C/N ratios and XRF scanning-derived elemental ratios (Si/K and Fe/K), as well as chlorophycean algae counts document changes in Amur freshwater and sediment discharge that condition the OSIW. Stable carbon isotopes of epi- and shallow endobenthic foraminifera, in combination with 14C analyses of benthic and planktic foraminifera imply decreases in OSIW oxygenation during deglacial warm phases from c. 14.7 to 13 ka (Bølling-Allerød) and c. 11.4 to 9 ka (Preboreal). No concomitant decreases in Okhotsk Sea benthic-planktic ventilation ages are observed, in contrast to nearby, but southerly locations on the Japan continental margin. We attribute Okhotsk Sea mid-depth oxygenation decreases in times of enhanced organic matter supply to maxima in remineralization within OSIW, in line with multi-proxy evidence for maxima in primary productivity and supply of organic matter. Sedimentary C/N and Fe/K ratios indicate more effective entrainment of nutrients into OSIW and thus an increased nutrient load of OSIW during deglacial warm periods. Correlation of palynological and sedimentological evidence from our sites with hinterland reference records suggests that millennial-scale changes in OSIW oxygen and nutrient concentrations were largely influenced by fluvial freshwater runoff maxima from the Amur, caused by a deglacial northeastward propagation of the East Asian Summer Monsoon that increased precipitation and temperatures, in conjunction with melting of permafrost in the Amur catchment area. We suggest that OSIW ventilation minima and the high lateral supply of nutrients and organic matter during the Allerød and Preboreal are mechanistically linked to concurrent maxima in nutrient utilization and biological productivity in the subpolar Northwest Pacific. In this scenario, increased export of nutrients from the Okhotsk Sea during deglacial warm phases supported subarctic Pacific shifts from generally Fe-limiting conditions to transient nutrient-replete regimes through enhanced advection of mid-depth nutrient- and Fe-rich OSIW into the upper ocean. This mechanism may have moderated the role of the subarctic Pacific in the deglacial CO2 rise on millennial timescales by combining the upwelling of old carbon-rich waters with a transient delivery of mid-depth-derived bio-available Fe and silicate.

  7. Importance of Organic Matter-Uranium Biogeochemistry to Uranium Plume Persistence in the Upper Colorado River Basin

    Science.gov (United States)

    Bargar, J.; Janot, N.; Jones, M. E.; Bone, S. E.; Lezama-Pacheco, J.; Fendorf, S. E.; Long, P. E.; Williams, K. H.; Bush, R. P.

    2014-12-01

    Recent evidence suggests that biologically driven redox reactions, fueled by sedimentary lenses enriched in detrital organic matter, play major roles in maintaining the persistent uranium groundwater plume in the subsurface at the U.S. Department of Enery's Rifle, CO field research site. Biogeochemical cycling of C, N, Fe, and S is highly active in these organic-rich naturally reduced zones (NRZs), and uranium is present as U(IV). The speciation of these elements profoundly influences the susceptibility of uranium to be reoxidized and remobiliized and contribute to plume persistence. However, uranim speciation in particular is poorly constrained in these sytems. To better evaluate the importance of NRZs to uranium mobility and plume persistence at the Rifle site, the DOE-BER-funded SLAC SFA team has characterized vertical concentration profiles and speciation of uranium, iron, sulfur, and NOM in well bores at high spatial resolution (4 inch intervals). Up to 95% of the sedimentary uranium pool was found to be concentrated in NRZs, where it occurs dominantly as non-crystalline forms of U(IV). Uranium accumulation and the presence of the short-lived sulfide mackinawite (FeS) at NRZ-aquifer interfaces indicate that NRZs actively exchange solutes with the surrounding aquifer. Moreover, sediment textures indicate that NRZs are likely to be abundant in riparian zones throughout the upper Colorado River basin (U.S.A.), which contains most of the contaminated DOE legacy uranium ore processing sites in the U.S. These results suggest that NRZ-uranium interactions may be important to plume persistence regionally and emphasize the importance of understanding molecular-scale processes.

  8. Amino acid biogeochemistry and bacterial contribution to sediment organic matter along the western margin of the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, L.; Garg, A.; Borole, D.V.

    and TN analysis. Concentrations of TOC and TN were determined by combusting pre-weighed samples in Elemental analyzer (Thermo Electron Corporation, Flash ES 1112 Series). Atropine was used as a standard. The C/N ratio was calculated as the molar ratio... 100 where, D-AA and THAA are molar concentrations 2.6. Contribution of peptidoglycan to THAA In order to determine the relative contribution of peptidoglycan (THAApep) to the total hydrolysable AA (THAA...

  9. Enumeration of bacteria from a Trichodesmium spp. bloom of the eastern Arabian Sea: Elucidation of their possible role in biogeochemistry

    Digital Repository Service at National Institute of Oceanography (India)

    Basu, S.; Matondkar, S.G.P.; Furtado, I.

    al., 1981).Gram staining was performed by both traditional and the KOH method (Buck, 1982). The enzyme activities of isolates were studied by measuring zones of hydrolysis on starch, casein and tributyrin agar (Podogorska and Mudryk, 2003). Growth... to absorbance A at wavelength λ and l is the optical path length (m). The exponential spectral slopes were then obtained by performing non-linear iterative least-squares fit of the CDOM spectrum to the equation: Ac λ = Ac λo e S (λo - λ) where, Ac...

  10. Growing up green on serpentine soils: Biogeochemistry of serpentine vegetation in the Central Coast Range of California

    Science.gov (United States)

    Oze, C.; Skinner, C.; Schroth, A.W.; Coleman, R.G.

    2008-01-01

    Serpentine soils derived from the weathering of ultramafic rocks and their metamorphic derivatives (serpentinites) are chemically prohibitive for vegetative growth. Evaluating how serpentine vegetation is able to persist under these chemical conditions is difficult to ascertain due to the numerous factors (climate, relief, time, water availability, etc.) controlling and affecting plant growth. Here, the uptake, incorporation, and distribution of a wide variety of elements into the biomass of serpentine vegetation has been investigated relative to vegetation growing on an adjacent chert-derived soil. Soil pH, electrical conductivity, organic C, total N, soil extractable elements, total soil elemental compositions and plant digestions in conjunction with spider diagrams are utilized to determine the chemical relationships of these soil and plant systems. Plant available Mg and Ca in serpentine soils exceed values assessed in chert soils. Magnesium is nearly 3 times more abundant than Ca in the serpentine soils; however, the serpentine soils are not Ca deficient with Ca concentrations as high as 2235 mg kg-1. Calcium to Mg ratios (Ca:Mg) in both serpentine and chert vegetation are greater than one in both below and above ground tissues. Soil and plant chemistry analyses support that Ca is not a limiting factor for plant growth and that serpentine vegetation is actively moderating Mg uptake as well as tolerating elevated concentrations of bioavailable Mg. Additionally, results demonstrate that serpentine vegetation suppresses the uptake of Fe, Cr, Ni, Mn and Co into its biomass. The suppressed uptake of these metals mainly occurs in the plants' roots as evident by the comparatively lower metal concentrations present in above ground tissues (twigs, leaves and shoots). This research supports earlier studies that have suggested that ion uptake discrimination and ion suppression in the roots are major mechanisms for serpentine vegetation to tolerate the chemistry of serpentine soils. ?? 2008 Elsevier Ltd.

  11. Nitrogen isotopes in Tree-Rings - An approach combining soil biogeochemistry and isotopic long series with statistical modeling

    Science.gov (United States)

    Savard, Martine M.; Bégin, Christian; Paré, David; Marion, Joëlle; Laganière, Jérôme; Séguin, Armand; Stefani, Franck; Smirnoff, Anna

    2016-04-01

    Monitoring atmospheric emissions from industrial centers in North America generally started less than 25 years ago. To compensate for the lack of monitoring, previous investigations have interpreted tree-ring N changes using the known chronology of human activities, without facing the challenge of separating climatic effects from potential anthropogenic impacts. Here we document such an attempt conducted in the oil sands (OS) mining region of Northeastern Alberta, Canada. The reactive nitrogen (Nr)-emitting oil extraction operations began in 1967, but air quality measurements were only initiated in 1997. To investigate if the beginning and intensification of OS operations induced changes in the forest N-cycle, we sampled white spruce (Picea glauca (Moench) Voss) stands located at various distances from the main mining area, and receiving low, but different N deposition. Our approach combines soil biogeochemical and metagenomic characterization with long, well dated, tree-ring isotopic series. To objectively delineate the natural N isotopic behaviour in trees, we have characterized tree-ring N isotope (15N/14N) ratios between 1880 and 2009, used statistical analyses of the isotopic values and local climatic parameters of the pre-mining period to calibrate response functions and project the isotopic responses to climate during the extraction period. During that period, the measured series depart negatively from the projected natural trends. In addition, these long-term negative isotopic trends are better reproduced by multiple-regression models combining climatic parameters with the proxy for regional mining Nr emissions. These negative isotopic trends point towards changes in the forest soil biogeochemical N cycle. The biogeochemical data and ultimate soil mechanisms responsible for such changes will be discussed during the presentation.

  12. Effects of excess nitrogen on biogeochemistry of a temperate hardwood forest: Evidence of nutrient redistribution by a forest understory species

    Science.gov (United States)

    Gilliam, Frank S.; Billmyer, Jake H.; Walter, Christopher A.; Peterjohn, William T.

    2016-12-01

    Excess nitrogen (N) in terrestrial ecosystems can arise from anthropogenically-increased atmospheric N deposition, a phenomenon common in eastern US forests. In spite of decreased N emissions over recent years, atmospheric concentrations of reactive N remain high in areas within this region. Excess N in forests has been shown to alter biogeochemical cycling of essential plant nutrients primarily via enhanced production and leaching of nitrate, which leads to loss of base cations from the soil. The purpose of our study was to investigate this phenomenon using a multifaceted approach to examine foliar nutrients of two herbaceous layer species in one N-treated watershed (WS3-receiving aerial applications of 35 kg N/ha/yr as ammonium sulfate, from 1989 to the present) and two untreated reference watersheds at the Fernow Experimental Forest, WV, USA. In 1993, we analyzed foliar tissue of Viola rotundifolia, a dominant herb layer species and prominent on all seven sample plots in each watershed. In 2013 and 2014, we used foliar tissue from Rubus allegheniensis, which had become the predominant species on WS3 and had increased, though to a lesser extent, in cover on both reference watersheds. Foliar N and potassium (K) were higher and foliar calcium (Ca) was lower on WS3 than on the reference watersheds for both species. Magnesium (Mg) was lower on WS3 for Viola, but was not different among watersheds for Rubus. Results support the stream chemistry-based observation that excess N lowers plant-available Ca and, to a lesser degree, Mg, but not of K. Foliar manganese (Mn) of Rubus averaged >4 times that of Viola, and was >50% higher on WS3 than on the reference watersheds. A Mn-based mechanism is proposed for the N-meditated increase in Rubus on WS3. Data suggest that excess N deposition not only alters herb community composition and biogeochemical cycling of forest ecosystems, but can do so simultaneously and interactively.

  13. Biogeochemistry of stable Ca and radiogenic Sr isotopes in a larch-covered permafrost-dominated watershed of Central Siberia

    Science.gov (United States)

    Bagard, Marie-Laure; Schmitt, Anne-Désirée; Chabaux, François; Pokrovsky, Oleg S.; Viers, Jérôme; Stille, Peter; Labolle, François; Prokushkin, Anatoly S.

    2013-08-01

    Stable Ca and radiogenic Sr isotope compositions were measured in different compartments (stream water, soil solutions, rocks, soils and soil leachates and vegetation) of a small permafrost-dominated watershed in the Central Siberian Plateau. The Sr and Ca in the area are supplied by basalt weathering and atmospheric depositions, which significantly impact the Sr isotopic compositions. Only vegetation significantly fractionates the calcium isotopes within the watershed. These fractionations occur during Ca uptake by roots and along the transpiration stream within the larch trees and are hypothesised to be the result of chromatographic processes and Ca oxalate crystallisations during Ca circulation or storage within plant organs. Biomass degradation significantly influences the Ca isotopic compositions of soil solutions and soil leachates via the release of light Ca, and organic and organo-mineral colloids are thought to affect the Ca isotopic compositions of soil solutions by preferential scavenging of 40Ca. The imprint of organic matter degradation on the δ44/40Ca of soil solutions is much more significant for the warmer south-facing slope of the watershed than for the shallow and cold soil active layer of the north-facing slope. As a result, the available stock of biomass and the decomposition rates appear to be critical parameters that regulate the impact of vegetation on the soil-water system in permafrost areas. Finally, the obtained δ44/40Ca patterns contrast with those described for permafrost-free environments with a much lower δ44/40Ca fractionation factor between soils and plants, suggesting specific features of organic matter decomposition in permafrost environments. The biologically induced Ca isotopic fractionation observed at the soil profile scale is not pronounced at the scale of the streams and large rivers in which the δ44/40Ca signature may be controlled by the heterogeneity of lithological sources.

  14. Subsurface microbiology and biogeochemistry of a deep, cold-water carbonate mound from the Porcupine Seabight (IODP Expedition 307).

    Science.gov (United States)

    Webster, Gordon; Blazejak, Anna; Cragg, Barry A; Schippers, Axel; Sass, Henrik; Rinna, Joachim; Tang, Xiaohong; Mathes, Falko; Ferdelman, Timothy G; Fry, John C; Weightman, Andrew J; Parkes, R John

    2009-01-01

    The Porcupine Seabight Challenger Mound is the first carbonate mound to be drilled (approximately 270 m) and analyzed in detail microbiologically and biogeochemically. Two mound sites and a non-mound Reference site were analyzed with a range of molecular techniques [catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH), quantitative PCR (16S rRNA and functional genes, dsrA and mcrA), and 16S rRNA gene PCR-DGGE] to assess prokaryotic diversity, and this was compared with the distribution of total and culturable cell counts, radiotracer activity measurements and geochemistry. There was a significant and active prokaryotic community both within and beneath the carbonate mound. Although total cell numbers at certain depths were lower than the global average for other subseafloor sediments and prokaryotic activities were relatively low (iron and sulfate reduction, acetate oxidation, methanogenesis) they were significantly enhanced compared with the Reference site. In addition, there was some stimulation of prokaryotic activity in the deepest sediments (Miocene, > 10 Ma) including potential for anaerobic oxidation of methane activity below the mound base. Both Bacteria and Archaea were present, with neither dominant, and these were related to sequences commonly found in other subseafloor sediments. With an estimate of some 1600 mounds in the Porcupine Basin alone, carbonate mounds may represent a significant prokaryotic subseafloor habitat.

  15. Potentiostatically Poised Electrodes Mimic Iron Oxide and Interact with Soil Microbial Communities to Alter the Biogeochemistry of Arctic Peat Soils

    Directory of Open Access Journals (Sweden)

    Largus T. Angenent

    2013-09-01

    Full Text Available Dissimilatory metal-reducing bacteria are ubiquitous in soils worldwide, possess the ability to transfer electrons outside of their cell membranes, and are capable of respiring with various metal oxides. Reduction of iron oxides is one of the more energetically favorable forms of anaerobic respiration, with a higher energy yield than both sulfate reduction and methanogenesis. As such, this process has significant implications for soil carbon balances, especially in the saturated, carbon-rich soils of the northern latitudes. However, the dynamics of these microbial processes within the context of the greater soil microbiome remain largely unstudied. Previously, we have demonstrated the capability of potentiostatically poised electrodes to mimic the redox potential of iron(III- and humic acid-compounds and obtain a measure of metal-reducing respiration. Here, we extend this work by utilizing poised electrodes to provide an inexaustable electron acceptor for iron- and humic acid-reducing microbes, and by measuring the effects on both microbial community structure and greenhouse gas emissions. The application of both nonpoised and poised graphite electrodes in peat soils stimulated methane emissions by 15%–43% compared to soils without electrodes. Poised electrodes resulted in higher (13%–24% methane emissions than the nonpoised electrodes. The stimulation of methane emissions for both nonpoised and poised electrodes correlated with the enrichment of proteobacteria, verrucomicrobia, and bacteroidetes. Here, we demonstrate a tool for precisely manipulating localized redox conditions in situ (via poised electrodes and for connecting microbial community dynamics with larger ecosystem processes. This work provides a foundation for further studies examining the role of dissimilatory metal-reducing bacteria in global biogeochemical cycles.

  16. The influence of Indian Ocean Dipole (IOD) on biogeochemistry of carbon in the Arabian Sea during 1997–1998

    Indian Academy of Sciences (India)

    V V S S Sarma

    2006-08-01

    Data on ocean color chlorophyll (Chl )obtained using Sea-viewing Wide Field of view Sensor (SeaWiFS),sea surface temperature (SST)by Advanced Very High Resolution Radiometer (AVHRR),and sea surface height (SSH)by TOPEX/POSEIDON were analyzed to examine the influence of Indian Ocean Dipole (IOD)on the physical and biogeochemical processes with special reference to phytoplankton primary production and air –sea fluxes of carbon dioxide in the Arabian Sea.Positive SST anomalies (SSTA)were found in the Arabian Sea (0.4 to 1.8°C) with higher values in the southwestern Arabian Sea that decreased towards north.The SSH anomalies (SSHA)and turbulent kinetic energy anomalies (TKEA)suggest decreased mixing during the IOD compared to the normal period.Chlorophyll displayed significant negative correlations with SSTA and SSHA in the Arabian Sea.Consistently, Chl showed negative anomalies (low Chl )during the IOD period which could be due to reduced inputs of nutrients.The photic zone integrated primary production decreased by 30%during the IOD period compared to the normal whereas pCO2 levels were higher (by 10-20 atm). However,sea to air fluxes were lower by 10% during the IOD period due to prevailing weaker winds.Primary production seems to be the key process controlling the surface pCO2 levels in the Arabian Sea.In future,the in fluence of IOD on ecosystem structure,export production and bacterial respiration rates are to be probed through in situ time-series observations.

  17. Long-term variation in above and belowground plant inputs alters soil organic matter biogeochemistry at the molecular-level

    Science.gov (United States)

    Simpson, M. J.; Pisani, O.; Lin, L.; Lun, O.; Simpson, A.; Lajtha, K.; Nadelhoffer, K. J.

    2015-12-01

    The long-term fate of soil carbon reserves with global environmental change remains uncertain. Shifts in moisture, altered nutrient cycles, species composition, or rising temperatures may alter the proportions of above and belowground biomass entering soil. However, it is unclear how long-term changes in plant inputs may alter the composition of soil organic matter (SOM) and soil carbon storage. Advanced molecular techniques were used to assess SOM composition in mineral soil horizons (0-10 cm) after 20 years of Detrital Input and Removal Treatment (DIRT) at the Harvard Forest. SOM biomarkers (solvent extraction, base hydrolysis and cupric (II) oxide oxidation) and both solid-state and solution-state nuclear magnetic resonance (NMR) spectroscopy were used to identify changes in SOM composition and stage of degradation. Microbial activity and community composition were assessed using phospholipid fatty acid (PLFA) analysis. Doubling aboveground litter inputs decreased soil carbon content, increased the degradation of labile SOM and enhanced the sequestration of aliphatic compounds in soil. The exclusion of belowground inputs (No roots and No inputs) resulted in a decrease in root-derived components and enhanced the degradation of leaf-derived aliphatic structures (cutin). Cutin-derived SOM has been hypothesized to be recalcitrant but our results show that even this complex biopolymer is susceptible to degradation when inputs entering soil are altered. The PLFA data indicate that changes in soil microbial community structure favored the accelerated processing of specific SOM components with littler manipulation. These results collectively reveal that the quantity and quality of plant litter inputs alters the molecular-level composition of SOM and in some cases, enhances the degradation of recalcitrant SOM. Our study also suggests that increased litterfall is unlikely to enhance soil carbon storage over the long-term in temperate forests.

  18. Aquifer Biogeochemistry and N Flux to Coastal Waters from Injected Wastewater Effluent in Kā´anapali, Maui, Hawaíi

    Science.gov (United States)

    Fackrell, J.; Glenn, C. R.; Popp, B. N.; Whittier, R. B.; Dulaiova, H.

    2015-12-01

    We utilized N and C species concentration data along with δ15N values of dissolved NO3- and δ13C values of dissolved inorganic C to evaluate the stoichiometry of biogeochemical reactions occurring within a subsurface plume originating from underground wastewater effluent injection at Lahaina Wastewater Reclamation Facility (LWRF) and discharging at several nearby submarine springs. Additionally, we compared LWRF time series data, injection rates, and treatment history with submarine spring time series data to assess correlation between input and output variables. We found that heterotrophic denitrification is the primary mechanism of N attenuation within the effluent plume and that chlorination of injected effluent for disinfection purposes may suppress microbial activity responsible for this N attenuation, resulting in increased N loading to the coastal ocean. The replacement of chlorination with UV disinfection may restore the biogeochemical reactions responsible for the N loss in the aquifer and return of N-attenuating conditions in the effluent plume, reducing N flux to coastal waters.

  19. The carbon isotope biogeochemistry of the individual hydrocarbons in bat guano and the ecology of insectivorous bats in the region of Carlsbad, New Mexico

    Science.gov (United States)

    Desmarais, D. J.; Mitchell, J. M.; Meinschein, W. G.; Hayes, J. M.

    1980-01-01

    The structures and C-13 contents of individual alkanes extracted from bat guano found in the Carlsbad region of New Mexico can be related to both the photosynthetic pathways of the local plants and the feeding habits of the insects that support the bats. Carbon isotopic analyses of the 62 most important plant species in the Pecos River Valley, the most significant feeding area for the Carlsbad bats, reveal the presence of 29 species with C3 photosynthesis and 33 species, mostly grasses, with C4 photosynthesis. Although the abundances of nonagricultural C3 and C4 plants are similar, alfalfa and cotton, both C3 plants, constitute over 95 per cent of the crop biomass. The molecular composition of the bat guano hydrocarbons is fully consistent with an insect origin. Two isotopically distinct groups of insect branched alkanes were discerned. These two groups of alkanes derived from two chemotaxonomically distinct populations of insects possessing distinctly different feeding habits. It is likely that one population grazes predominantly on crops whereas the other population prefers native vegetation. This and other isotopic evidence supports the notion that crop pests constitute a major percentage of the bats' diet.

  20. The carbon isotope biogeochemistry of the individual hydrocarbons in bat guano and the ecology of the insectivorous bats in the region of Carlsbad, New Mexico

    Science.gov (United States)

    Des Marais, D. J.; Mitchell, J. M.; Meinschein, W. G.; Hayes, J. M.

    1980-01-01

    The structures and C-13 contents of individual hydrocarbons extracted from bat guano found in the Carlsbad region of New Mexico are analyzed in order to elucidate details of the carbon flow in the plant-insect-bat ecosystem. Carbon isotopic analyses indicate that equivalent numbers of plants with C3 and C4 photosynthetic pathways occupy the feeding area of the bats, which supports alfalfa and cotton as well as native plants. The molecular composition of the guano is consistent with an origin in two distinct populations of insects with different feeding habits, one of which may graze predominantly on crops. It is also pointed out that isotopic analyses of more ancient guano deposits may be useful in characterizing prevalent vegetation and climate of earlier periods.

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

    Science.gov (United States)

    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 fractionation in soil solution samples might be ascribed to aforementioned biogeochemical redistribution of organic sulfur.

  2. Geochemical Rate/RNA Integration Study (GRIST): A Pilot Field Experiment for Inter-Calibration of Biogeochemistry and Nucleic Acid Measurements Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Bronk, Deborah

    2007-01-08

    The Geochemical Rate/RNA Integration Study (GRIST) project sought to correlate biogeochemical flux rates with measurements of gene expression and mRNA abundance to demonstrate the application of molecular approaches to estimate the presence and magnitude of a suite of biogeochemical processes. The study was headed by Lee Kerkhoff of Rutgers University. In this component of the GRIST study, we characterized ambient nutrient concentrations and measured uptake rates for dissolved inorganic nitrogen (DIN, ammonium, nitrate and nitrite) and dissolved organic nitrogen (urea and dissolved free amino acids) during two diel studies at the Long-Term Ecosystem Observatory (LEO-15) on the New Jersey continental shelf.

  3. Spatial and temporal patterns of CH4 and N2O fluxes in terrestrial ecosystems of North America during 1979–2008: application of a global biogeochemistry model

    Directory of Open Access Journals (Sweden)

    G. Chen

    2010-04-01

    Full Text Available Continental-scale estimations of terrestrial methane (CH4 and nitrous oxide (N2O fluxes over a long time period are crucial to accurately assess the global balance of greenhouse gases and enhance our understanding and prediction of global climate change and terrestrial ecosystem feedbacks. Using a process-based global biogeochemical model, the Dynamic Land Ecosystem Model (DLEM, we quantified simultaneously CH4 and N2O fluxes in North America's terrestrial ecosystems from 1979 to 2008. During the past 30 years, approximately 14.69±1.64 T g C a−1 (1 T g=1012 g of CH4, and 1.94±0.16 T g N a−1 of N2O were released from terrestrial ecosystems in North America. At the country level, both the United States and Canada acted as CH4 sources to the atmosphere, but Mexico mainly oxidized and consumed CH4 from the atmosphere. Wetlands in North America contributed predominantly to the regional CH4 source, while all other ecosystems acted as sinks for atmospheric CH4, of which forests accounted for 36.8%. Regarding N2O emission in North America, the United States, Canada, and Mexico contributed 56.19%, 18.23%, and 25.58%, respectively, to the continental source over the past 30 years. Forests and croplands were the two ecosystems that contributed most to continental N2O emission. The inter-annual variations of CH4 and N2O fluxes in North America were mainly attributed to year-to-year climatic variability. While only annual precipitation was found to have a significant effect on annual CH4 flux, both mean annual temperature and annual precipitation were significantly correlated to annual N2O flux. The regional estimates and spatiotemporal patterns of terrestrial ecosystem CH4 and N2O fluxes in North America generated in this study provide useful information for global change research and policy making.

  4. Biogeochemistry of Metalliferous Peats: Sulfur Speciation and Depth Distributions of dsrAB Genes and Cd, Fe, Mn, S, and Zn in Soil Cores

    Energy Technology Data Exchange (ETDEWEB)

    Martinez,C.; Yanez, C.; Yoon, S.; Bruns, M.

    2007-01-01

    Spatial relationships between concentrations of Cd, Fe, Mn, S, and Zn and bacterial genes for dissimilatory sulfate reduction were studied in soils of the Manning peatland region in western New York. Peat cores were collected within a field exhibiting areas of Zn phytotoxicity, and pH and elemental concentrations were determined with depth. The oxidation states of S were estimated using S-XANES spectroscopy. Soil microbial community DNA was extracted from peat soils for ribosomal RNA intergenic spacer analysis (RISA) of diversity profiles with depth. To assess the presence of sulfate-reducing microorganisms (SRM), DNA extracts were also used as templates for PCR detection of dsrAB genes coding for dissimilatory (bi)sulfite reductase. Elemental distributions, S redox speciation, and detection of dsrAB genes varied with depth and water content. The pH of peat soils increased with depth. The highest concentrations of Zn, Cd, and S occurred at intermediate depths, whereas Mn concentrations were highest in the topmost peat layers. Iron showed a relatively uniform distribution with depth. Concentrations of redox sensitive elements, S and Mn, but not Fe, seemed to respond to variations in water content and indicated vertical redox stratification in peat cores where topmost peats were typically acidic and oxidizing and deeper peats were typically circumneutral and reducing. Even then, S-XANES analyses showed that surface peats contained >50% of the total S in reduced forms while deep peats contained generally <5% of the total S in oxidized forms. While bacterial RISA profiles of the peats were diverse, dsrAB gene detection followed redox stratification chemistry closely. For the most part, dsrAB genes were detected in deeper peats, where S accumulation was evident, while they were not detected in topmost peat layers where Mn accumulation indicated oxic conditions. Combined chemical, spectroscopic, and microbiological analyses indicated that prolonged exposure to dry-wet cycles resulted in the formation of two redox-stratified zones with distinct chemical and microbiological signatures within peat cores of the Manning peatland region. As illustrated in this study, changes in redox conditions affect bacterial community composition and downward mobility of toxic elements, which has implications for water contamination and the design of metal remediation strategies.

  5. Biogeochemistry of mercury in a river-reservoir system: impact of an inactive chloralkali plant on the Holston River-Cherokee Reservoir, Virginia and Tennessee

    Energy Technology Data Exchange (ETDEWEB)

    Hildebrand, S. G.; Lindberg, S. E.; Turner, R. R.; Huckabee, J. W.; Strand, R. H.; Lund, J. R.; Andren, A. W.

    1980-08-01

    Elevated mercury concentrations in fish species from the North Fork of the Holston River were observed in the early 1970's. The source of the mercury was a chloralkali plant which had ceased operation in 1972. Mercury continues to be released to the river from two large (approx. 40-ha) waste disposal ponds at the plant site. This report presents results of a study of the emission of mercury to the environment from the abandoned waste ponds and of the distribution of mercury in water, sediment, and biota of the Holston River-Cherokee Reservoir System in Virginia and eastern Tennessee.

  6. New insights into the biogeochemistry of extremely acidic environments revealed by a combined cultivation-based and culture-independent study of two stratified pit lakes.

    Science.gov (United States)

    Falagán, Carmen; Sánchez-España, Javier; Johnson, David Barrie

    2014-01-01

    The indigenous microbial communities of two extremely acidic, metal-rich stratified pit lakes, located in the Iberian Pyrite Belt (Spain), were identified, and their roles in mediating transformations of carbon, iron, and sulfur were confirmed. A combined cultivation-based and culture-independent approach was used to elucidate microbial communities at different depths and to examine the physiologies of isolates, which included representatives of at least one novel genus and several species of acidophilic Bacteria. Phosphate availability correlated with redox transformations of iron, and this (rather than solar radiation) dictated where primary production was concentrated. Carbon fixed and released as organic compounds by acidophilic phototrophs acted as electron donors for acidophilic heterotrophic prokaryotes, many of which catalyzed the dissimilatory reduction in ferric iron; the ferrous iron generated was re-oxidized by chemolithotrophic acidophiles. Bacteria that catalyze redox transformations of sulfur were also identified, although these Bacteria appeared to be less abundant than the iron oxidizers/reducers. Primary production and microbial numbers were greatest, and biogeochemical transformation of carbon, iron, and sulfur, most intense, within a zone of c. 8-10 m depth, close to the chemocline, in both pit lakes. Archaea detected in sediments included two Thaumarchaeota clones, indicating that members of this recently described phylum can inhabit extremely acidic environments.

  7. The role of soil biogeochemistry in wine taste: Soil factors influencing grape elemental composition, photosynthetic biomarkers and Cu/Zn isotopic signature of Vitis vinifera

    Science.gov (United States)

    Blotevogel, Simon; Oliva, Priscia; Darrozes, José; Viers, Jérôme; Audry, Stéphane; Courjault-Radé, Pierre; Orgogozo, Laurent; Le Guedard, Marina; Schreck, Eva

    2015-04-01

    Understanding the influence of soil composition in wine taste is of great economic and environmental interest in France and around the world. Nevertheless the impact of soil composition on wine taste is still controversially discussed. Since inorganic soil components do not have a proper taste and do not enter the plant anyway, their influence needs to be induced by nutrient absorption and its impact on plant functioning and grape composition. Indeed recent development of geological tracers of origin proof the existence of soil chemical and isotopic signatures in wine. However, type and scale of the impact of soil composition on wine taste are not well understood yet, and little experimental evidence exists due to the complexity of mechanisms involved. Thus, to provide evidence for the impact of soil composition on grape composition and potentially wine taste, we studied soil and plant material from two relevant vineyards (Soave, Italia). On those two directly adjacent vineyards, two different wines are produced with the same plant material and cultivation techniques. The vineyards only differ by their underlying bedrock - limestone versus basaltic rock - and thus present suitable conditions for investigating the impact of soil composition on grapes and wine. Pedological and mineralogical parameters were analyzed for the two vineyards whereas chemical extractions (citrate, CaCl2) were performed to determine nutrient bioavailability in both soils. Elemental compositions were determined by ICP-MS analyses in different compartments (soils, vine leaves and grapes). Isotopic fractionation of Cu and Zn was investigated in various samples as source tracers and in order to better understand fractionation mechanisms involved. Finally, plant health was studied using the Omega-3 biomarker which determines the fatty acid composition in vine leaves, directly involved in photosynthetic processes. Results show that the vineyards are characterized by two different soil types due to the geological difference. These soils differ in elemental compositions and bioavailability of mineral nutrients, preconditions for a potential influence on plants and wine. Elemental ratios of soils are partly transmitted to leaves and grapes of correspondent plants, including nutrients such as Ca. Plant photosynthetic functioning is significantly better on the limestone vineyard due to lower Cu bioavailability: Omega-3 values are negatively linked to Cu bioavailability in corresponding soils. These observations suggest a difference in organic molecule synthesis depending on the vineyard soil, which might include components relevant for taste and fermentation. Cu and Zn isotopic ratios do not differ between both soils. The main fractionation of Cu and Zn isotopes occurs at the soil-plant interface making those isotopes suitable tracers for uptake mechanisms. As a result Zn isotope ratios reveal a strong recycling of Zn in the soil-plant continuum. Our results show a significant influence of soil composition on grape composition, plant biochemistry and potentially wine taste. Determination of organic and sensorial composition of grapes and wine is ongoing and will be discussed in further communications.

  8. A preliminary biogeochemistry-based quantification of primary productivity of end-Permian deep-water basin in Dongpan Section ,Guangxi ,South China

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yang; HE Weihong; FENG Qinglai

    2007-01-01

    In this Paper,the mean primary productivity of the Talung Formation in the deep-water basin(50-500 m depth)of Dongpan,Guangxi,South China,was calculated,of the content of the trace element Cu.Results showed that the primary productivity obtained was comparable with the previously-reported data for the black shale of the Phosphoria Formation,a Permian phosphate deposit in the northwest United States,and also similar to that of the modern deposit in the Cariaco basin,Venezuela.It was observed that the primary productivity increased with the enhanced abundance of algae and photosynthetic bacteria,and with the decrease in both the radiolarian individuals and the body size of brachiopods during the faunal mass extinction.This ecological coupling indicates that the changes of primary productivity are closely related to the propagation and the decline of producers(algae and bacteria),and that consumers(radiolarians and brachiopods)probably have little influence on the changes of primary productivity.

  9. 亚马孙河流域汞的生物地球化学研究%Biogeochemistry of Mercury in the Amazonian Environment

    Institute of Scientific and Technical Information of China (English)

    Julio Cesar Wasserman; Sandra Hacon; Maria Angélica Wasserman

    2003-01-01

    本文阐述和评论了影响亚马孙河流域汞循环的途径,并提出了新的研究方向.对于汞污染源的讨论,无论是天然的还是人为的,都缺乏基本的论据.毫无疑问,黄金矿山释放的汞已经局部地提高了环境中汞的浓度,但在整个亚马孙河流域,与一些学者在远离金矿的土壤中测出的高浓度数值相比,这种负荷并不显著.土壤中汞的高浓度现象有一个合理的解释,即B层(淀积层)是在地质时期蓄积了汞的"海绵体",当发生侵蚀和森林火灾时,汞又被释放回循环体系.源于人类活动导致的亚马孙河流域森林的环境退化,很可能会加速汞的释放.汞在还原性的缺氧环境--沉积物和水中--的转换也是理解汞的环境甲基化的一个关键性问题.在亚马孙河流域环境所做的这项研究非常有限,研究结果只能得出受限的结论,进一步的工作应注重结合时间和空间变化的监测计划.

  10. Spatial and temporal patterns of CH4 and N2O fluxes in terrestrial ecosystems of North America during 1979–2008: application of a global biogeochemistry model

    Directory of Open Access Journals (Sweden)

    C. Lu

    2010-09-01

    Full Text Available Continental-scale estimations of terrestrial methane (CH4 and nitrous oxide (N2O fluxes over a long time period are crucial to accurately assess the global balance of greenhouse gases and enhance our understanding and prediction of global climate change and terrestrial ecosystem feedbacks. Using a process-based global biogeochemical model, the Dynamic Land Ecosystem Model (DLEM, we quantified simultaneously CH4 and N2O fluxes in North America's terrestrial ecosystems from 1979 to 2008. During the past 30 years, approximately 14.69 ± 1.64 T g C a−1 (1 T g = 1012 g of CH4, and 1.94 ± 0.1 T g N a−1 of N2O were released from terrestrial ecosystems in North America. At the country level, both the US and Canada acted as CH4 sources to the atmosphere, but Mexico mainly oxidized and consumed CH4 from the atmosphere. Wetlands in North America contributed predominantly to the regional CH4 source, while all other ecosystems acted as sinks for atmospheric CH4, of which forests accounted for 36.8%. Regarding N2O emission in North America, the US, Canada, and Mexico contributed 56.19%, 18.23%, and 25.58%, respectively, to the continental source over the past 30 years. Forests and croplands were the two ecosystems that contributed most to continental N2O emission. The inter-annual variations of CH4 and N2O fluxes in North America were mainly attributed to year-to-year climatic variability. While only annual precipitation was found to have a significant effect on annual CH4 flux, both mean annual temperature and annual precipitation were significantly correlated to annual N2O flux. The regional estimates and spatiotemporal patterns of terrestrial ecosystem CH4 and N2O fluxes in North America generated in this study provide useful information for global change research and policy making.

  11. Copper, zinc and lead biogeochemistry in aquatic and land plants from the Iberian Pyrite Belt (Portugal) and north of Morocco mining areas.

    Science.gov (United States)

    Durães, Nuno; Bobos, Iuliu; Ferreira da Silva, Eduardo; Dekayir, Abdelilah

    2015-02-01

    The ability of aquatic (Juncus effusus L., Scirpus holoschoenus L., Thypha latifolia L. and Juncus sp.) and land (Cistus ladanifer L., Erica andevalensis C.-R., Nerium oleander L., Isatis tinctoria L., Rosmarinus officinalis L., Cynodon dactylon L. and Hordeum murinum L.) plants from Portugal (Aljustrel, Lousal and São Domingos) and Morocco (Tighza and Zeida) mining areas to uptake, translocate and tolerate heavy metals (Cu, Zn and Pb) was evaluated. The soils (rhizosphere) of the first mining area are characterized by high acidity conditions (pH 2-5), whereas from the second area, by alkaline conditions (pH 7.0-8.5). Physicochemical parameters and mineralogy of the rhizosphere were determined from both areas. Chemical analysis of plants and the rhizosphere was carried out by inductively coupled plasma emission spectrometry. The sequential chemical extraction procedure was applied for rhizosphere samples collected from both mining areas. In the acid conditions, the aquatic plants show a high capacity for Zn bioaccumulation and translocation and less for Pb, reflecting the following metal mobility sequence: Zn > Cu > Pb. Kaolinite detected in the roots by infrared spectroscopy (IR) contributed to metal fixation (i.e. Cu), reducing its translocation to the aerial parts. Lead identified in the roots of land plants (e.g. E. andevalensis) was probably adsorbed by C-H functional groups identified by IR, being easily translocated to the aerial parts. It was found that aquatic plants are more efficient for phytostabilization than bioaccumulation. Lead is more bioavailable in the rhizosphere from Morocco mining areas due to scarcity of minerals with high adsorption ability, being absorbed and translocated by both aquatic and land plants.

  12. Bottom RedOx Model (BROM v.1.1): a coupled benthic-pelagic model for simulation of water and sediment biogeochemistry

    Science.gov (United States)

    Yakushev, Evgeniy V.; Protsenko, Elizaveta A.; Bruggeman, Jorn; Wallhead, Philip; Pakhomova, Svetlana V.; Yakubov, Shamil Kh.; Bellerby, Richard G. J.; Couture, Raoul-Marie

    2017-02-01

    Interactions between seawater and benthic systems play an important role in global biogeochemical cycling. Benthic fluxes of some chemical elements (e.g., C, N, P, O, Si, Fe, Mn, S) alter the redox state and marine carbonate system (i.e., pH and carbonate saturation state), which in turn modulate the functioning of benthic and pelagic ecosystems. The redox state of the near-bottom layer in many regions can change with time, responding to the supply of organic matter, physical regime, and coastal discharge. We developed a model (BROM) to represent key biogeochemical processes in the water and sediments and to simulate changes occurring in the bottom boundary layer. BROM consists of a transport module (BROM-transport) and several biogeochemical modules that are fully compatible with the Framework for the Aquatic Biogeochemical Models, allowing independent coupling to hydrophysical models in 1-D, 2-D, or 3-D. We demonstrate that BROM is capable of simulating the seasonality in production and mineralization of organic matter as well as the mixing that leads to variations in redox conditions. BROM can be used for analyzing and interpreting data on sediment-water exchange, and for simulating the consequences of forcings such as climate change, external nutrient loading, ocean acidification, carbon storage leakage, and point-source metal pollution.

  13. Marine biogeochemistries of Be and Al: A study based on cosmogenic 10Be, Be and Al in marine calcite, aragonite, and opal

    Indian Academy of Sciences (India)

    Weiquan Dong; Devendra Lal; Barbara Ransom; Wolfgang Berger; Marc W Caffee

    2001-06-01

    The geochemical behaviors of Be and Al in ocean waters have been successfully studied in recent years using natural, cosmogenic, radioactive 10Be and 26Al as tracers. The present day dissolved concentrations and distribution of the stable and radioactive isotopes of Be and Al in ocean waters have revealed their short residence times and appreciable effects of exchange uxes at the coastal and ocean-sediment interfaces. It follows that concentrations of these particle-active elements must have varied in the past with temporal changes in climate, biological productivity and aeolian ux of continental detritus to the oceans. We therefore investigated the feasibility of extending the measurements of Be and Al isotope concentrations in marine systems to the 103-106 BP time scale. We report here the discovery of significant amounts of intrinsic Be and Al in marine foraminiferal calcite and coral aragonite, and of Al in opal (radiolarians) and aragonite (coral), which makes it possible to determine 10Be/Be and 26Al/Al in oceans in the past. We also report measured 10Be/9Be in foraminiferal calcite in Pacific Ocean cores, which reveal that the concentrations and ratios of the stable and cosmogenic isotopes of Be and Al have varied significantly in the past 30 ky. The implications of these results are discussed.

  14. Cobalt Biogeochemistry in the South Atlantic: A Full-Depth Zonal Ocean Section of Total Dissolved Cobalt, and Development of a High Throughput Cobalt ICP-MS Method

    Science.gov (United States)

    Noble, A. E.; Saito, M. A.; Goepfert, T. J.

    2008-12-01

    This study presents the first high-resolution full-depth zonal section of total dissolved cobalt from a recent cruise transecting the South Atlantic Ocean along approximately 11S. This section demonstrates that current electrochemical analytical techniques are capable of producing the high precision and high resolution datasets for total dissolved cobalt expected to be generated as a part of the international GEOTRACES Program. The micronutritive role of cobalt may affect community structure in different regions of the oceans, a compelling reason to include cobalt in the trace element analyses planned for the GEOTRACES Program. This cobalt section reveals an advective source of cobalt from the African coast near Namibia, which we propose to be due to the Benguela Current interacting with reducing shelf sediments. These high concentrations of cobalt were also observed within the oxygen minimum zone that extends across much of the South Atlantic basin in this section, and are likely indicative of redox cycling of cobalt in the water column. Nutrient-like vertical structure of cobalt was observed in the surface waters across the majority of the basin due to biological utilization, and the expected hybrid-type trend is observed at depth, with scavenging of cobalt below the nutricline. Deepwater concentrations of cobalt were around 50pM across the basin below 3000m. Analysis of the shelf-life of refrigerated filtered samples stored without acidification for electrochemical cobalt analysis demonstrated that those samples which were collected specifically within oxygen minimum zones may underestimate cobalt if not analyzed within a few weeks of collection. These results motivate our on-going development of a method to measure cobalt in acidified samples via inductively coupled plasma mass spectrometry (ICP-MS). The benefit of this technique would be twofold: acidification would extend the shelf-life of the samples significantly, and samples would be preserved identically to those intended for other ICP-MS total metal analyses such as iron, manganese, cadmium, and zinc. Initial method development indicates that UV-irradiation is required to destroy natural cobalt-binding ligands, which we proposed is due to incomplete dissociation of organic cobalt complexes at pH values typically used for sample acidification.

  15. Complexities of Nitrogen Isotope Biogeochemistry in Plant-Soil Systems: Implications for the Study of Ancient Agricultural and Animal Management Practices

    Directory of Open Access Journals (Sweden)

    Paul eSzpak

    2014-06-01

    Full Text Available Nitrogen isotopic studies have potential to shed light on the structure of ancient ecosystems, agropastoral regimes, and human-environment interactions. Until relatively recently, however, little attention was paid to the complexities of nitrogen transformations in ancient plant-soil systems and their potential impact on plant and animal tissue nitrogen isotopic compositions. This paper discusses the importance of understanding nitrogen dynamics in ancient contexts, and highlights several key areas of archaeology where a more detailed understanding of these processes may enable us to answer some fundamental questions. This paper explores two larger themes that are prominent in archaeological studies using stable nitrogen isotope analysis: (1 agricultural practices (use of animal fertilizers, burning of vegetation or shifting cultivation, and tillage and (2 animal domestication and husbandry (grazing intensity/stocking rate and the foddering of domestic animals with cultigens. The paucity of plant material in ancient deposits necessitates that these issues are addressed primarily through the isotopic analysis of skeletal material rather than the plants themselves, but the interpretation of these data hinges on a thorough understanding of the underlying biogeochemical processes in plant-soil systems. Building on studies conducted in modern ecosystems and under controlled conditions, these processes are reviewed, and their relevance discussed for ancient contexts.

  16. Biogeochemistry of a large, meromictic tropical lake (Lake Kivu, East Africa): insights from a stable isotope study covering an annual cycle

    Science.gov (United States)

    Morana, Cedric; Darchambeau, François; Muvundja, Fabrice; Roland, Fleur; Kelemen, Zita; Commarieu, Marc-Vincent; Leporcq, Bruno; Alunga, Georges; Masilya, Pascal; Descy, Jean-Pierre; Borges, Alberto V.; Bouillon, Steven

    2014-05-01

    Lake Kivu (East Africa) is a large (2370 km2) and deep (maximum depth of 485 m) meromictic lake. Its vertical structure consists of an oxic and nutrient-poor mixed layer down to 70 m maximum, and a permanently anoxic monimolimnion rich in dissolved gases (methane and carbon dioxide) and nutrients. Seasonal variation of the vertical position of the oxic-anoxic interface is driven by contrasting air humidity and wind speed regimes between rainy (October-May) and dry (June-September) seasons. The latter is characterized by a deepening of the oxic zone, and an increased input of dissolved gases and inorganic nutrients. The mean annual photic depth is 18 m, but water transparency slightly decreases during the dry season. In this study, we present a comprehensive data set covering a full annual cycle at a fortnightly resolution, which combine hydrochemical data, δ13C and δ15N measurements of particulate organic carbon and nitrogen (POC, PN) and zooplankton, δ13C of dissolved organic and inorganic carbon (DOC, DIC), nutrients and gases (CH4) concentrations, phytoplankton biomass and composition. In the euphotic zone, phytoplankton biomass was constant during the rainy season, but doubled during the dry season. In contrast, δ13C-DIC increased linearly with time during the rainy season, deviating from the values expected at isotopic equilibrium with the atmosphere, then suddenly decreased in the dry season due to the vertical mixing with 13C-depleted DIC. Results of mass-balance calculations indicate that the δ13C-DIC increase reflects the net autotrophic status of the mixed layer. Irrespective of the season, the δ13C-POC signatures were constant from the surface to the oxic-anoxic interface, then showed a local and abrupt excursion to values as low as -40o reflecting the incorporation of a 13C-depleted source in the POC. While the large pool of DIC is the main carbon source for POC in surface waters, CH4 contributes significantly to C fixation at the oxic-anoxic interface all year round. The δ13C signature of the DOC pool shows very little variation in the mixolimnion and thus appears to be uncoupled from the POC pool, suggesting that old and refractory compounds constitute the major part of the DOC pool. Also the more labile and freshly produced DOC that reflects the δ13C signature of the POC, is rapidly mineralized. Finally, we noticed a shift toward higher values in the δ15N-PN during the dry season (from 0.5o to 4.0) and δ15N-PN was significantly related to the proportion of cyanobacteria in the euphotic zone. Hence the variation of δ15N-PN in surface waters could either reflects a change in the dominant phytoplankton taxa or in the biogeochemical processes controlling the upward nitrate and ammonium fluxes. Zooplankton δ15N signatures mirrored the seasonal changes in δ15N-PN and were significantly correlated to phytoplankton biomass, highlighting their dependence on autochtonous sources of organic matter in this large lake.

  17. Biogeochemistry of plant-soil system in a limestone area: A case study of Mt. Kinsho-zan, Gifu prefecture, central Japan

    Science.gov (United States)

    Ueno, S.; Sugitani, K.; Ono, M.

    2010-12-01

    Limestone contains few of the nutrients essential for plant growth, such as Si, K, and P. Owing to its high concentrations of alkali earth elements and the resulting high pH, P and Fe tend to be sparingly available for plants in soils developed in limestone areas. Because of this limited availability of nutrients in calcareous soils, certain typical calcareous plants are known to occasionally dominate. On Mt. Kinsho-zan, a limestone mountain in Gifu prefecture, central Japan, however, typical calcareous plants are not seen; various non-calcareous plants appear and do not seem to be malnourished. In addition to the nutrients supplied by precipitation and eolian dusts, litter decomposition may supply nutrients, which could circulate in the plant-soil system. In this study, the soil properties (water content, loss on ignition, and pH) and the chemical compositions of soils, plant leaves (Chamaecyparis obtusa), and parental rocks (limestone) were analyzed to clarify the biogeochemical cycle of the plant-soil system on Mt. Kinsho-zan. A mountain composed of sandstone and mudstone, which lies near the main research area, was chosen for comparison. Chemical compositions were analyzed using an X-ray fluorescence spectrometer (Spectris Co., Ltd Panalytical Division Axios-N system). Ten major elements were analyzed in all samples, and 13 and 4 trace elements were analyzed for soils and plants and for limestones, respectively. In the limestone samples, the concentrations were as follows: SiO2 = 0.12-0.22wt%, Al2O3 = 0.054-0.13wt%, Fe2O3 = 0.021-0.057wt%, CaO = 55.12-55.33wt%, K2O = 40-55 ppm, TiO2 = 29-48 ppm, and Zr = 12-14 ppm. In soils developed in the limestone area, SiO2 = 43.48-55.46wt%, Al2O3 = 25.47-34.92wt%, Fe2O3 = 10.75-13.64wt%, CaO = 0.46-5.61wt%, K2O = 1.30-1.72wt%, TiO2 = 1.02-1.36wt%, and Zr = 240-319 ppm. Concentrations of Fe2O3, MnO, and P2O5 in soils from the limestone area are two times higher than those in soils from the sandstone-mudstone area; the concentrations of CaO are about 10 times higher than those in soils from the sandstone-mudstone area. Compared to the sandstone-mudstone area, 13 elements in soils and 10 elements in leaves from the limestone area have higher concentrations. Soils from the limestone area contain higher concentrations of MnO, Ni, and Zn than those from the sandstone-mudstone area. Concentrations of these elements in leaves, in contrast, tend to be lower in the limestone area than in the sandstone-mudstone area; Si shows the opposite result. Both soils and leaves in the limestone area contain more Ca and P than those in the sandstone-mudstone area. In the limestone area, CaO/TiO2 and P2O5/TiO2 ratios in soils are lower than those in rocks, suggesting leaching of Ca and P, whereas the upper soil samples have higher values than the lower soil samples. Calcareous dust transported from a nearby excavated research field may have been deposited on the surface layer. Zr/TiO2 ratios in soils are lower than those in rocks, suggesting that materials with low Zr/TiO2 values have been transported into soils. The soils in the limestone area likely contain significant amounts of allochthonous materials, in addition to the weathering products of parental rocks.

  18. A novel adaptive biogeochemical model, and its 3-D application for a decadal hindcast simulation of the biogeochemistry of the southern North Sea

    Science.gov (United States)

    Kerimoglu, Onur; Hofmeister, Richard; Wirtz, Kai

    2016-04-01

    Adaptation and acclimation processes are often ignored in ecosystem-scale model implementations, despite the long-standing recognition of their importance. Here we present a novel adaptive phytoplankton growth model where acclimation of the community to the changes in external resource ratios is accounted for, using optimality principles and dynamic physiological traits. We show that the model can reproduce the internal stoichiometries obtained at marginal supply ratios in chemostat experiments. The model is applied in a decadal hindcast simulation of the southern North Sea, where it is coupled to a 2-D benthic model and a 3-D hydrodynamic model in an approximately 1.5km horizontal resolution at the German Bight coast. The model is shown to have good skill in capturing the steep, coastal gradients in the German Bight, suggested by the match between the estimated and observed dissolved nutrient and chlorophyll concentrations. We then analyze the differential sensitivity of the coastal and off-shore zones to major drivers of the system, such as riverine nutrient loads. We demonstrate that the relevance of phytoplankton acclimation varies across coastal gradients and can become particularly significant in terms of summer nutrient depletion.

  19. DAYCENT Simulations to Test the Influence of Fire Regime and Fire Suppression on Trace Gas Fluxes and Nitrogen Biogeochemistry of Colorado Forests

    Directory of Open Access Journals (Sweden)

    Mark A. Gathany

    2012-07-01

    Full Text Available Biological activity and the physical environment regulate greenhouse gas fluxes (CH4, N2O and NO from upland soils. Wildfires are known to alter these factors such that we collected daily weather records, fire return intervals, or specific fire years, and soil data of four specific sites along the Colorado Front Range. These data were used as primary inputs into DAYCENT. In this paper we test the ability of DAYCENT to simulate four forested sites in this area and to address two objectives: (1 to evaluate the short-term influence of fire on trace gas fluxes from burned landscapes; and (2 to compare trace gas fluxes among locations and between pre-/post- fire suppression. The model simulations indicate that CH4 oxidation is relatively unaffected by wildfire. In contrast, gross nitrification rates were reduced by 13.5–37.1% during the fire suppression period. At two of the sites, we calculated increases in gross nitrification rates (>100%, and N2O and NO fluxes during the year of fire relative to the year before a fire. Simulated fire suppression exhibited decreased gross nitrification rates presumably as nitrogen is immobilized. This finding concurs with other studies that highlight the importance of forest fires to maintain soil nitrogen availability.

  20. [Dietary behavior of the Middle Ages in Grenoble: application of isotopic biogeochemistry of the Saint-Laurent cemetery (XIIIth-XVth centuries, Isère, France)].

    Science.gov (United States)

    Herrscher, E; Bocherens, H; Valentin, F; Colardelle, R

    2001-05-01

    Isotopic analysis of 13C and 15N of 47 bones from Saint-Laurent de Grenoble cemetery (Grenoble, Isère), from the end of medieval period (XIIIth-XVth centuries AD) allowed to define the food status of animals with regard to the humans and to discuss the variability amongst adults. Adults who died young and those with small stature may have had diets poor in animal protein. The consumption of animal proteins was more important in the XVth than in the XIVth century and could illustrate a typical urban food economy providing its population with a more diversified diet than in rural areas.

  1. Linking sedimentary sulfur and iron biogeochemistry to growth patterns of a cold-water coral mound in the Porcupine Basin, S.W. Ireland (IODP Expedition 307).

    Science.gov (United States)

    Wehrmann, L M; Titschack, J; Böttcher, M E; Ferdelman, T G

    2015-09-01

    Challenger Mound, a 150-m-high cold-water coral mound on the eastern flank of the Porcupine Seabight off SW Ireland, was drilled during Expedition 307 of the Integrated Ocean Drilling Program (IODP). Retrieved cores offer unique insight into an archive of Quaternary paleo-environmental change, long-term coral mound development, and the diagenetic alteration of these carbonate fabrics over time. To characterize biogeochemical carbon-iron-sulfur transformations in the mound sediments, the contents of dithionite- and HCl-extractable iron phases, iron monosulfide and pyrite, and acid-extractable calcium, magnesium, manganese, and strontium were determined. Additionally, the stable isotopic compositions of pore-water sulfate and solid-phase reduced sulfur compounds were analyzed. Sulfate penetrated through the mound sequence and into the underlying Miocene sediments, where a sulfate-methane transition zone was identified. Small sulfate concentration decreases (<7 mM) within the top 40 m of the mound suggested slow net rates of present-day organoclastic sulfate reduction. Increasing δ(34)S-sulfate values due to microbial sulfate reduction mirrored the decrease in sulfate concentrations. This process was accompanied by oxygen isotope exchange with water that was indicated by increasing δ(18)O-sulfate values, reaching equilibrium with pore-water at depth. Below 50 mbsf, sediment intervals with strong (34)S-enriched imprints on chromium-reducible sulfur (pyrite S), high degree-of-pyritization values, and semi-lithified diagenetic carbonate-rich layers characterized by poor coral preservation, were observed. These layers provided evidence for the occurrence of enhanced microbial sulfate-reducing activity in the mound in the past during periods of rapid mound aggradation and subsequent intervals of non-deposition or erosion when geochemical fronts remained stationary. During these periods, especially during the Early Pleistocene, elevated sulfate reduction rates facilitated the consumption of reducible iron oxide phases, coral dissolution, and the subsequent formation of carbonate cements.

  2. Ecology and biogeochemistry of the Antarctic Circumpolar Current during austral spring : a summary of Southern Ocean JGOFS cruise ANT X/6 of R.V. Polavstern

    NARCIS (Netherlands)

    Smetacek, V.; Baar, H.J.W. de; Bathmann, U.V.; Lochte, K.; Rutgers van der Loeff, M.M.

    1997-01-01

    The R.V. Polarstern cruise ANT X/6, part of the international Southern Ocean JGOFS programme, investigated phytoplankton spring bloom development and its biogeochemical effects in different water masses of the Atlantic sector of the Southern Ocean: the Polar Frontal region (PFr), the southern Antarc

  3. Relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in Monterey Bay, California

    Science.gov (United States)

    Rathburn, Anthony E.; PéRez, M. Elena; Martin, Jonathan B.; Day, Shelley A.; Mahn, Chris; Gieskes, Joris; Ziebis, Wiebke; Williams, David; Bahls, Amanda

    2003-12-01

    As part of an ongoing effort to explore the use of foraminifera as a means to assess modern and ancient methane release, we compared ambient pore water chemistry with the distribution and stable isotopic composition of living (rose Bengal stained) foraminifera in MBARI ROV Ventana tube cores taken from modern seepage areas (about 1000 m water depth) in Monterey Bay, California. Benthic foraminiferal isotopic differences between sites clearly indicate that methane-influenced pore waters affect foraminiferal distributions and carbonate isotope geochemistry. Carbon isotope signatures of living benthic foraminifera did not conform to the very negative (-30 to -48‰), methane-influenced carbon isotope values of the pore waters they live in. Instead, the influence of methane seep pore waters was reflected in the greater range and carbon isotopic variability of living seep foraminifera compared with published δ13C values of foraminifera living in nonseep habitats. It is not clear what relative influences biological, ecological, and physical factors have on the carbon isotopic signatures observed in seep foraminifera. Substantial carbon isotope differences can exist between individuals of the same seep species. For instance, δ13C values of living Globobulimina pacifica varied by as much as 2.9‰ between seeps within 8 km of each other, whereas δ13C values of living Uvigerina peregrina varied by as much as 1.95‰ within the same seep. Provided there is no diagenetic alteration of the test carbonate, isotopic results of individual seep foraminifera support the hypothesis that foraminifera can be used to assess past and present methane seepage.

  4. Arsenic biogeochemistry and human health risk assessment in organo-arsenical pesticide-applied acidic and alkaline soils: an incubation study.

    Science.gov (United States)

    Datta, Rupali; Sarkar, Dibyendu; Sharma, Saurabh; Sand, Kumarswamy

    2006-12-15

    Organo-arsenical compounds are considered non-carcinogenic, and hence, are still allowed by the regulatory agencies for use in agriculture as pesticides. Due to rapid encroachment of suburban areas into former agricultural lands, the potential for human exposure to soil-arsenic has increased tremendously in recent years. However, insufficient data is available on the stability of organo-arsenicals in soils; as to whether they remain in an organic form, or are converted over time to potentially carcinogenic inorganic forms. A static incubation study was conducted to estimate soil speciation and in-vitro bioavailability (i.e., bioaccessibility) of arsenic as a function of soil properties. Two chemically variant soil types were chosen, based on their potential differences with respect to arsenic reactivity: an acid sand with minimal arsenic retention capacity and an alkaline clay loam with relatively high concentrations of Fe/Al and Ca/Mg. The soils were amended with dimethylarsenic acid (DMA) at three rates, 45, 225 and 450 mg/kg, and incubated for 1 year. A sequential extraction scheme was employed to identify the geochemical forms of arsenic in soils, which were correlated with the in-vitro bioavailable fractions of arsenic. Human health risk calculated in terms of excess cancer risk (ECR) showed that risk assessment based on bioaccessible arsenic concentrations instead of the traditional total soil arsenic is a more realistic approach. Results showed that soil properties (such as pH, Fe/Al content and soil texture) of the two soils dictated the geochemical speciation, and hence, bioaccessibility of arsenic from DMA, indicating that the use of organic arsenicals as pesticides in mineral soils may not be a safe practice from a human health risk perspective.

  5. Comparative effects of climate on ecosystem nitrogen and soil biogeochemistry in U.S. national parks. FY 2001 Annual Report (Res. Rept. No. 94)

    Science.gov (United States)

    Stottlemyer, R.; Edmonds, R.; Scherbarth, L.; Urbanczyk, K.; Van Miegroet, H.; Zak, J.

    2002-01-01

    In 1998, the USGS Global Change program funded research for a network of Long-Term Reference Ecosystems initially established in national parks and funded by the National Park Service. The network included Noland Divide, Great Smoky Mountains National Park, Tennessee; Pine Canyon, Big Ben National park, Texas; West Twin Creek, Olympic National Park, Washingtona?? Wallace Lake, Isle Royale National Park, Michigan; and the Asik watershed, Noatak National Preserve, Alaska. The watershed ecosystem model was used since this approach permits additional statistical power in detection of trends among variables, and the watershed in increasingly a land unit used in resource management and planning. The ecosystems represent a major fraction of lands administered by the National Park Service, and were chosen generally for the contrasts among sites. For example, tow of the site, Noland and West Twin, are characterized by high precipitation amounts, but Noland receives some of the highest atmospheric nitrogen (N) inputs in North America. In contrast, Pine Canyon and Asik are warm and cold desert sites respectively. The Asik watershed receives treeline) of the boreal biome in the North America while Wallace is at the southern ecotone between boreal and northern hardwoods. The research goal for these sites is to gain a basic understanding of ecosystem structure and function, and the response to global change especially atmospheric inputs and climate.

  6. Education, fish consumption, well water, chicken coops, and cooking fires: Using biogeochemistry and ethnography to study exposure of children from Yucatan, Mexico to metals and arsenic.

    Science.gov (United States)

    Arcega-Cabrera, Flor; Fargher, Lane F

    2016-10-15

    Around the world, the nocuous health effects of exposure to environmental contaminants, especially metals and Arsenic, are a growing health concern. This is especially the case in Mexico, where corruption and ineffective political administration are contributing to increasing deterioration in the environment. Importantly, shallow soils and the karstic nature of bedrock in Yucatan, Mexico make the subterranean aquifer especially susceptible to contamination because contaminates are carried to it with little resistance. Given these environmental conditions, we developed a multi/interdisciplinary project to evaluate the impact of metal and Arsenic pollution on a sample of 107 children, ages 6 to 9years, living in the urban areas of Progreso, Merida, and Ticul, in the State of Yucatan using urine and blood samples. In addition, ethnographic research was carried out in the homes of the children that participated in the study to identify potential exposure pathways. This research proved invaluable because the complexity of human social organization, lifestyles, and geographical patterning create an intricate array of exposure pathways that vary across social sectors and geographic space. In the following article, we use nonparametric univariate statistical analysis to reveal potential exposure pathways among sub-populations included in our sample. These analyses show that children from poor/marginal families tend to be exposed to Copper, Lead, and Nickel; whereas, children, from wealthier families, tend to be exposed to Cadmium, Arsenic, and inorganic Copper (Copper Sulfate).

  7. Notes on HP1 a software package for simulating variably-saturated water flow, heat transport, solute transport, and biogeochemistry in porous media. HP1 Version 2.2

    Energy Technology Data Exchange (ETDEWEB)

    Jacques, D.; Simunek, J.

    2010-01-15

    HP1 is a comprehensive modeling tool in terms of processes and reactions for simulating reactive transport and biogeochemical processes in variably-saturated porous media. HP1 results from coupling the water and solute transport model HYDRUS-1D (Simunek et al., 2009a) and PHREEQC-2 (Parkhurst and Appelo, 1999). This note provides an overview of how to set up and execute a HP1 project using version 2.2.002 of HP1 and version 4.13 of the graphical user interface (GUI) of HYDRUS-1D. A large part of this note are step-by-step instructions for selected examples involving mineral dissolution and precipitation, cation exchange, surface complexation and kinetic degradation networks. The implementation of variably-saturated flow conditions, changing boundary conditions, a layered soil profile or immobile water is also illustrated.

  8. Avaliação biogeoquímica dos solos e do medronheiro na área mineira da Panasqueira Biogeochemistry evaluation of soils and arbutus trees in the Panasqueira mine area

    Directory of Open Access Journals (Sweden)

    B. Godinho

    2010-01-01

    Full Text Available As Minas da Panasqueira são uma das mais importantes minas em laboração em Portugal. Ao longo de 100 anos de explora­ção de tungsténio, cobre e estanho produzi­ram-se resíduos que foram amontoados à superfície, em escombreiras, provocando impactos ambientais elevados. Este trabalho teve como objectivo o estudo biogeoquími­co da envolvente das Minas da Panasqueira através da avaliação de solos e plantas de medronheiro (Arbutus unedo L.. Os solos apresentam-se contaminados (mg kg-1 em As (922, Cd (3, Cu (215, Pb (77, W (138 e Zn (260. Nas plantas, apenas o cádmio ocorre em concentrações médias (1,53 mg kg-1 acima do limite tolerável pela generalidade das plantas, no entanto, nenhuma planta apresentava sinais de toxi­cidade. O medronheiro parece ser tolerante às elevadas concentrações totais e da frac­ção disponível (solução DTPA desses ele­mentos nos solos, podendo por isso, ser usado em programas de fitoestabilização e para aproveitamento dos frutos com o objectivo de produzir aguardente.Panasqueira mine is one of the most im­portant mines in Portugal. Over the last cen­tury exploration of tungsten, copper and tin has contributed to produce many waste ma­terials that constitute tailings with huge di­mensions generating high visual and chemi­cal impacts. The objective of this work was to study the biogeochemical impact of min­ing on the soils and arbutus trees (Arbutus unedo L. in this area. Soils developed on waste materials or hosted rocks are contaminated with (mg kg-1 As (922, Cd (3, Cu (215, Pb (77, W (138 and Zn (260. In plants, cadmium is the only element that exceeded the vege­tation tolerant limit, but none of the sampled plants showed visual signs of toxicity. Ar­butus tree seems to be tolerant to the high soil concentrations (total and available frac­tion of the hazardous elements. Therefore arbutus trees can be used in phytostabiliza­tion as a soil remediation strategy. Further studies could also allow the use of their fruits for alcohol production.

  9. The biogeochemistry of freshwater Mollusca from Huaihe River watershed and water pollution control%淮河流域贝类生物地球化学研究与水污染治理

    Institute of Scientific and Technical Information of China (English)

    李玉成

    2004-01-01

    简介贝类生物地球化学及其在淮河流域生态环境研究中的应用.这方面研究不仅仅揭示了流域生态环境的灾难性现状,更重要的是为水污染防治,特别是有毒污染物防治提供科学依据.贝类生物地球化学研究在环境预警和生态修复方面有重要应用前景.

  10. FINAL REPORT - Biogeochemistry of Uranium Under Reducing and Re-oxidizing Conditions:An Integrated Laboratory and Field Study and Acceptable Endpoints for Metals and Radionuclides: Quantifying the Stability of Uranium and Lead Immobilized Under Sulfate Reducing Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Brent Peyton; James Amonette; Haluk Beyenal; Gill Geesey; Zbigniew Lewandowski; Rajesh Sani

    2005-10-07

    Our understanding of subsurface microbiology is hindered by the inaccessibility of this environment, particularly when the hydrogeologic medium is contaminated with toxic substances. Research in our labs indicated that the composition of the growth medium (e.g., bicarbonate complexation of U(VI)) and the underlying mineral phase (e.g., hematite) significantly affects the rate and extent of U(VI) reduction and immobilization through a variety of effects. Our research was aimed at elucidating those effects to a much greater extent, while exploring the potential for U(IV) reoxidation and subsequent re-mobilization, which also appears to depend on the mineral phases present in the system. In situ coupons with a variety of mineral phases were placed in monitoring wells at the NABIR FRC. These coupons showed that the mineral phase composition significantly affected the resulting attached phase microbial community. Our comparative use of both batch and open flow reactors (more representative of field conditions) indicates that hydrodynamics and continual influx of substrate and contaminants can also yield significantly different results than those obtained with closed serum bottles. To this end, the following overall experimental hypothesis tested was the following: On a mineral surface under anaerobic conditions, accumulations of secondary inorganic precipitates are controlled by a) the bacteria associated with the mineral surface, b) the electron acceptors available for anaerobic bacterial respiration, and c) local hydrodynamics and pH buffers govern micro- and meso-scale interaction of U in the presence of electron donors and acceptors, and nutrients.

  11. Microbiology and biogeochemistry of sediments and rhizosphere of mangroves: bacterial production, sulphate-reduction and methylation of mercury with methodological focus on incubation-extraction of {sup 14}C-leucine; Microbiologia e biogeoquimica de sedimentos e rizosfera de manguezais: producao bacteriana, sulfato-reducao e metilacao do mercurio com enfoque metodologico na incubacao-extracao de {sup 14}C-leucina

    Energy Technology Data Exchange (ETDEWEB)

    Feijo, Issabella Vitoria Abduche

    2015-07-01

    Mangroves are one of the most important ecosystems when it comes to cycling of various elements, including carbon and mercury. Microbiological processes that occur in sediment are essential for carbon mineralization, its conversion into biomass and for availability of mercury to the food chain. Sulfate-reducing bacteria are one of the main groups responsible for degradation of organic compounds in marine sediments and mercury methylation, especially in the rhizosphere of macrophyte. The aim of this study was to evaluate bacterial production (BP) over different sedimentary profiles as well as mercury methylation (% MeHg), sulfate reduction rates (SRR) and bacterial production in the rhizosphere of a ubiquitous mangrove tree. Radiochemical approaches were used to access bacterial production ({sup 14}C-leucine), sulfate reduction ({sup 35}SO{sub 4}) and mercury methylation ({sup 203}Hg). Study area was located at Coroa Grande (Sepetiba bay) and Jequia mangrove (Guanabara bay). Methodological studies using {sup 14}C-leucine as a tool to assess bacterial production in mangrove sediment were not found. In this context, we tested two leucine uptake methodologies for measuring bacterial production in mangrove sediments according to Baath et al. (2001) Soil Biol. Biochem., v.33,p. 1571-1574 and Fischer and Pusch (1999) Appl. Environ. Microbiol., v.6, p.4411-4418. Our results suggest that an adaptation of both techniques were suitable to measure BP in mangrove sediment. We also provided underlying parameters of the method such as saturation level and linearity of leucine incorporation that can be used as guidance for future studies in mangrove. Once the methodology was established, we accessed BP along a shallow sedimentary profile in three physiographic mangroves types: basin, fringe and riverine. BP was highly heterogeneous in different physiographic types of mangroves and along the sediment profiles.The mangrove located at Guanabara bay presented BP which was 50 times higher than tho one located at Sepetiba bay. We also estimated the contribution for BP of different groups using metabolic inhibitors: prokaryotic, eukaryotic, sulphate-reducing bacteria (SRB) and methanogenic. Our results showed that bacteria are the major group in carbon cycling in all location and sulfate-reducing bacteria would not be the main group involved in the degradation of organic matter in the studied mangroves. Regarding the formation of MeHg in mangrove sediment, this work is the first to assess mercury methylation in the rhizosphere (pneumatophores and feeding roots) of a mangrove tree (Avicennia schaueriana). Our results showed that mercury methylation and sulphate reduction were significantly higher in the rhizosphere of feeding roots (p <0.05). Bacterial production as also higher in rhizosphere but with no significant difference with bulk sediment (p>0.05). There was a significant positive correlation between sulfate-reducing and PB (r{sup 2} = 0.29, p <0.05). No significant correlation was found neither with BP and %MeHg, nor with SRR and %MeHg. Sites where sulfate reduction was higher, %MeHg decreased. Our data suggested that other groups in addition to the SRB may be involved in methylation of mercury in mangrove rhizosphere. (author)

  12. Modelling global fresh surface water temperature

    NARCIS (Netherlands)

    Beek, L.P.H. van; Eikelboom, T.; Vliet, M.T.H. van; Bierkens, M.F.P.

    2011-01-01

    Temperature directly determines a range of water physical properties including vapour pressure, surface tension, density and viscosity, and the solubility of oxygen and other gases. Indirectly water temperature acts as a strong control on fresh water biogeochemistry, influencing sediment concentrati

  13. West Coast fish, mammal, bird life history and abunance parameters - Developing end-to-end models of the California Current Large Marine Ecosystem

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to develop spatially discrete end-to-end models of the California Current LME, linking oceanography, biogeochemistry, food web...

  14. Land cover change and soil fertility decline in tropical regions

    NARCIS (Netherlands)

    Hartemink, A.E.; Veldkamp, A.; Bai, Zhanguo

    2008-01-01

    Land cover changes influence the biogeochemistry, hydrology, and climate of the earth. Studies that assessed land cover changes at the global scale mostly focused on: deforestation, cropland expansion, dry land degradation, urbanisation, pasture expansion, and agricultural intensification. For the a

  15. Ocean science: The rise of Rhizaria

    Science.gov (United States)

    Caron, David A.

    2016-04-01

    Large amoeba-like organisms known as Rhizaria have often been overlooked in studies of ocean biology and biogeochemistry. Underwater imaging and ecological network analyses are revealing their roles. See Article p.465 & Letter p.504

  16. Physical oceanography - Developing end-to-end models of the California Current Large Marine Ecosystem

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to develop spatially discrete end-to-end models of the California Current LME, linking oceanography, biogeochemistry, food web...

  17. Atlantis model outputs - Developing end-to-end models of the California Current Large Marine Ecosystem

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to develop spatially discrete end-to-end models of the California Current LME, linking oceanography, biogeochemistry, food web...

  18. Model outputs - Developing end-to-end models of the Gulf of California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to develop spatially discrete end-to-end models of the northern Gulf of California, linking oceanography, biogeochemistry, food web...

  19. West Coast fish, mammal, and bird species diets - Developing end-to-end models of the California Current Large Marine Ecosystem

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to develop spatially discrete end-to-end models of the California Current LME, linking oceanography, biogeochemistry, food web...

  20. Microbial mediators of the sulfur, nitrogen, and iron cycles in freshwater ecosystems

    NARCIS (Netherlands)

    Haaijer, S.C.M.

    2007-01-01

    Human activities and concominant sulfur and nitrogen pollution endanger freshwater ecosystem quality. Improved knowledge on wetland biogeochemistry is a necessity to protect these valuable and fragile ecosystems. Effects of increased nitrate concentrations (stimulation of sulfide mineral oxidation,

  1. Oxygen deficiency in the North Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A

    in contact with oxygen-depleted waters. Impacts of the oxygen deficiency on regional biogeochemistry, especially anaerobic nitrogen transformaions, are described. A comparison of the perrenial, mesopelagic OMZ in the open Northwestern Indian Ocean is made...

  2. 78 FR 8128 - Request for Nominations of Experts to the EPA Office of Research and Development's Board of...

    Science.gov (United States)

    2013-02-05

    ... scientific, engineering, and social science fields. EPA will consider nominees from academia, industry... resources --soil biogeochemistry --system ecology --landscape ecology --urban ecology Engineering --biochemical engineering --bioenvironmental engineering --civil engineering (drinking water treatment...

  3. Preface to: Indian Ocean biogeochemical processes and ecological variability

    Digital Repository Service at National Institute of Oceanography (India)

    Hood, R.R.; Naqvi, S.W.A.; Wiggert, J.D.

    initiating a new international research program. This initiative (Sustained Indian Ocean Biogeochemistry and Ecosystem Research or SIBER) has been formally approved and is now sponsored by the Integrated Marine Biogeochem istry and Ecosystem Research...

  4. Gulf of California species and catch spatial distributions and historical time series - Developing end-to-end models of the Gulf of California

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The purpose of this project is to develop spatially discrete end-to-end models of the northern Gulf of California, linking oceanography, biogeochemistry, food web...

  5. Mycorrhizal responses to biochar in soil-concepts and mechanisms.

    NARCIS (Netherlands)

    Warnock, D.D.; Lehmann, J.; Kuyper, T.W.; Rillig, M.C.

    2007-01-01

    Experiments suggest that biomass-derived black carbon (biochar) affects microbial populations and soil biogeochemistry. Both biochar and mycorrhizal associations, ubiquitous symbioses in terrestrial ecosystems, are potentially important in various ecosystem services provided by soils, contributing t

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

    DEFF Research Database (Denmark)

    Le Quéré, Corinne; Buitenhuis, Erik T.; Moriarty, Róisín

    2016-01-01

    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...... 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....

  7. 现代酸性矿山废水环境中的真核微生物:生物多样性、生理学、生物地球化学特征及其对古环境和早期生命演化的指示%MICROEUKARYOTES IN MODERN ACID MINE DRAINAGE ENVIRONMENTS : DIVERSITY, PHYSIOLOGY, BIOGEOCHEMISTRY,AND PALEOENVIRONMENTAL IMPLICATIONS

    Institute of Scientific and Technical Information of China (English)

    Shamik Dasgupta; 方家松; 李江涛; 张利; 王嘉妮; 韦兵兵

    2013-01-01

    The acid mine drainage ( AMD) environment is considered as a modern analog to environments in the early Earth. The metal-laden, low-pH water of the AMD is similar to certain aqueous environment thought to have existed in Archean and early Proterozoic oceans in areas of active volcanism. Despite the low pH, high metal content, and nutrient-deprived nature of the environment, both prokaryotes and eukaryotes thrive in AMD. Of interest is the acidophilic, photosynthetic microeukaryote Euglena mutabilis. This review provides a comprehensive overview of the biochemistry, physiology, and biogeochemical signatures constructed by Euglenids in AMD and their broad implications in understanding biochemical evolution and paleoenvironmental conditions on the primitive Earth. The formation of biofilms and the conservation of compartmentalized aerobic and anaerobic biosynthetic pathways of wax esters and sterols in mitochondria may have allowed euglenids to survive and diversify on early Earth. The Fe-rich stromatolites, lipids and their carbon isotopic ratios, which are linked to the acidic environment and the unique physiology and biochemistry of the acidophiles are biosignatures that can be used for elucidating the plausible linkage between eukaryotic evolution, oxygenation of the early atmosphere, formation of BIF, and environmental evolution of the early Earth.%现代酸性矿山废水(AMD)环境被认为是地球早期环境的理想对应物.AMD的水环境具有金属含量高、pH低的特点,这与太古代-早元古代时期海洋的某些环境条件十分类似.然而,尽管AMD的环境条件恶劣,但仍然栖息着非常丰富的原核和真核微生物,在这其中那些嗜酸的、营光合作用的真核微生物类群(特别是Euglena mutabilis)更是引起众多科学家极大的研究兴趣.本文全面概述了在AMD环境中发现的真核微生物Euglenids种群的生物化学、生理学和生物地球化学特征,以及这些特征对于理解生命演化和早期地球环境条件等方面的指示性作用.Euglenids的细胞具备区域化功能,因而具备需氧和厌氧的蜡酯和甾醇的双生物合成途径,同时它们还可以形成生物膜,所有这些均使得Euglenids能够在早期地球极端恶劣的环境条件下生存并持续演化.在AMD酸性环境中发育的富铁叠层石、嗜酸微生物的脂类化合物及其碳同位素比值以及它们独特的生理和生化特征可用于阐述真核生物的演化、地球早期大气中氧气的产生、条带状富铁建造的形成以及地球早期的环境演化等.

  8. Microorganisms and their roles in fundamental biogeochemical cycles.

    Science.gov (United States)

    Madsen, Eugene L

    2011-06-01

    Biogeochemistry is the discipline that strives to understand intricate processes, often microbially mediated ones, that transform and recycle both organic and inorganic substances in soils, sediments, and waters. These processes, manifestations of diverse and highly evolved cellular mechanisms catalyzed by Bacteria and Archaea, maintain the biosphere. Progress in biogeochemistry relies upon the underlying science of environmental microbiology. Over the last 2 years, important discoveries have advanced the ecological, physiological, biochemical, and genomic bases for a variety of microbiological processes including anaerobic methane oxidation, photosynthesis, phosphorous uptake, biodegradation of organic pollutants, and numerous aspects of the nitrogen and sulfur cycles. Here recent literature is assessed and placed within a five-stage paradigm for making scientific progress in environmental microbiology, biogeochemistry, and biotechnology.

  9. Biogeochemical Transformations in the History of the Ocean

    Science.gov (United States)

    Lenton, Timothy M.; Daines, Stuart J.

    2017-01-01

    The ocean has undergone several profound biogeochemical transformations in its 4-billion-year history, and these were an integral part of the coevolution of life and the planet. This review focuses on changes in ocean redox state as controlled by changes in biological activity, nutrient concentrations, and atmospheric O2. Motivated by disparate interpretations of available geochemical data, we aim to show how quantitative modeling—spanning microbial mats, shelf seas, and the open ocean—can help constrain past ocean biogeochemical redox states and show what caused transformations between them. We outline key controls on ocean redox structure and review pertinent proxies and their interpretation. We then apply this quantitative framework to three key questions: How did the origin of oxygenic photosynthesis transform ocean biogeochemistry? How did the Great Oxidation transform ocean biogeochemistry? And how was ocean biogeochemistry transformed in the Neoproterozoic-Paleozoic?

  10. Influence of hydraulics on the uptake of ammonium by two freshwater plants

    NARCIS (Netherlands)

    Bal, K.D.; Brion, N.; Woule-Ebongué, V.; Schoelynck, J.; Jooste, A.; Barrón, C.; Dehairs, F.; Meire, P.; Bouma, T.J.

    2013-01-01

    1 Macrophytes are important in the biogeochemistry of flowing rivers, although most information so far has relied on measurements of nutrients in plant tissues. This yields only indirect information on the nutrient uptake fluxes by roots and shoots and about nutrient translocation between roots an

  11. Comparing reconstructed past variations and future projections of the Baltic Sea ecosystem—first results from multi-model ensemble simulations

    DEFF Research Database (Denmark)

    Meier, H E Markus; Andersson, Helén C; Arheimer, Berit;

    2012-01-01

    Multi-model ensemble simulations for the marine biogeochemistry and food web of the Baltic Sea were performed for the period 1850–2098, and projected changes in the future climate were compared with the past climate environment. For the past period 1850–2006, atmospheric, hydrological and nutrient...

  12. Gas Transport and Exchange through Wetland Plant Aerenchyma

    DEFF Research Database (Denmark)

    Sorrell, Brian Keith; Brix, Hans

    2013-01-01

    Aerenchyma, the large airspaces in aquatic plants, is a rapid gas transport pathway between atmosphere and soil in wetlands. Oxygen transport aerates belowground tissue and oxidizes rhizosphere soil, an important process in wetland biogeochemistry. Most plant O2 transport occurs by diffusion...

  13. Biogeochemical Considerations Related To The Remediation Of I-129 Plumes

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, D. I. [Savannah River Site (SRS), Aiken, SC (United States); Yeager, C. [Los Alamos National Laboratory , Los Alamos, NM (United States); Denham, M. E. [Savannah River Site (SRS), Aiken, SC (United States); Zhang, S. [Texas A& amp; M University, Galveston, TX (United States); Xu, C. [Texas A& amp; M University, Galveston, TX (United States); Schwehr, K. A. [Texas A& amp; M University, Galveston, TX (United States); Li, H. P. [Texas A& amp; M University, Galveston, TX (United States); Brinkmeyer, R. [Texas A& amp; M University, Galveston, TX (United States); Santschi, P. H. [Texas A& amp; M University, Galveston, TX (United States)

    2012-09-24

    The objectives of this report were to: provide a current state of the science of radioiodine biogeochemistry relevant to its fate and transport at the Hanford Site; conduct a review of Hanford Site data dealing with groundwater {sup 129}I; and identify critical knowledge gaps necessary for successful selection, implementation, and technical defensibility in support of remediation decisions.

  14. Snow cover manipulation effects on microbial community structure and soil chemistry in a mountain bog

    NARCIS (Netherlands)

    Robroek, B.J.M.; Heijboer, A.; Jassey, V.E.J.; Hefting, M.M.; Rouwenhorst, T.G.; Buttler, A.; Bragazza, L.

    2013-01-01

    Background and Aims Alterations in snow cover driven by climate change may impact ecosystem functioning, including biogeochemistry and soil (microbial) processes. We elucidated the effects of snow cover manipulation (SCM) on above-and belowground processes in a temperate peatland. Methods In a Swiss

  15. Biogeochemical context impacts seawater pH changes resulting from atmospheric sulfur and nitrogen deposition

    NARCIS (Netherlands)

    Hagens, M.; Hunter, K.A.; Liss, P.S.; Middelburg, J.J.

    2014-01-01

    Seawater acidification can be induced both by absorption of atmospheric carbon dioxide (CO2) and by atmospheric deposition of sulfur and nitrogen oxides and ammonia. Their relative significance, interplay, and dependency on water column biogeochemistry are not well understood. Using a simple biogeoc

  16. A physically based model of global freshwater surface temperature

    NARCIS (Netherlands)

    Beek, van L.P.H.; Eikelboom, T.; Vliet, van M.T.H.; Bierkens, M.F.P.

    2012-01-01

    Temperature determines a range of physical properties of water and exerts a strong control on surface water biogeochemistry. Thus, in freshwater ecosystems the thermal regime directly affects the geographical distribution of aquatic species through their growth and metabolism and indirectly through

  17. Lime muds and their genesis off-Northwestern India during the late Quaternary

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.; AnilKumar, A.; Naqvi, S.W.A.; Chivas, A.R.; Sekar, B.; Kessarkar, P.M.

    and Wilber R J 1993 Great Bahama Bank aragonitic muds: mostly inorgani- cally precipitated, mostly exported; J. Sedim. Petrol. 63 589–595. Mitterer R M 1972 Biogeochemistry of aragonite mud and ooids; Geochim Cosmochim Acta 36 1407–1422. Morse J W...

  18. High export of dissolved silica from the Greenland Ice Sheet

    NARCIS (Netherlands)

    Meire, L.; Meire, P.; Struyf, E.; Krawczyk, D.W.; Arendt, K.E.; Yde, J.C.; Juul-Pedersen, T.; Hopwood, M. J.; Rysgaard, S.; Meysman, F.J.R.

    2016-01-01

    Silica is an essential element for marine life and plays a key role in the biogeochemistry ofthe ocean. Glacial activity stimulates rock weathering, generating dissolved silica that is exported tocoastal areas along with meltwater. The magnitude of the dissolved silica export from large glacial area

  19. Spectroscopic Evidence of Uranium Immobilization in Acidic Wetlands by Natural Organic Matter and Plant Roots

    Science.gov (United States)

    Biogeochemistry of uranium in wetlands plays important roles in U immobilization in storage ponds of U mining and processing facilities but has not been well understood. The objective of this work was to study molecular mechanisms responsible for high U retention by Savannah Ri...

  20. How nitrogen and sulphur addition, and a single drought event affect root phosphatase activity in Phalaris arundinacea

    NARCIS (Netherlands)

    Robroek, B.J.M.; Adema, E.B.; Venterink, H.O.; Leonardson, L.; Wassen, M.J.

    2009-01-01

    Conservation and restoration of fens and fen meadows often aim to reduce soil nutrients, mainly nitrogen (N) andphosphorus (P). The biogeochemistry of P has received much attention as P-enrichment is expected to negatively impact on species diversity in wetlands. It is known that N, sulphur (S) and

  1. The sum is more than its parts: Key species in the functioning of cold-water coral reef communities

    NARCIS (Netherlands)

    Mueller, C.E.

    2014-01-01

    Cold-water coral reefs are hotspots of biodiversity and biogeochemistry in the deep-sea, solely fuelled by external energy sources. Hence, food input, processing and recycling play a major role in the functioning of these ecosystems. In this thesis we aimed to study energy flow and metabolism of col

  2. Stochastic Convection Parameterizations

    Science.gov (United States)

    Teixeira, Joao; Reynolds, Carolyn; Suselj, Kay; Matheou, Georgios

    2012-01-01

    computational fluid dynamics, radiation, clouds, turbulence, convection, gravity waves, surface interaction, radiation interaction, cloud and aerosol microphysics, complexity (vegetation, biogeochemistry, radiation versus turbulence/convection stochastic approach, non-linearities, Monte Carlo, high resolutions, large-Eddy Simulations, cloud structure, plumes, saturation in tropics, forecasting, parameterizations, stochastic, radiation-clod interaction, hurricane forecasts

  3. The role of trans-disciplinary skills in environmental education and science

    Science.gov (United States)

    In the past three decades there have been tremendous changes in how environmental scientists address issues relating to societal needs. In the early 1980s interdisciplinary work may have involved one or two related disciplines such as limnology, statistics and biogeochemistry in...

  4. Manure-DNDC: a biogeochemical process model for quantifying greenhouse gas and ammonia emissions from livestock manure systems

    Science.gov (United States)

    From the point of view of biogeochemistry, manure is a complex of organic matter containing minor minerals. When manure is excreted by animals, it undergoes a series of reactions such as decomposition, hydrolysis, ammonia volatilization, nitrification, denitrification, and fermentation from which ca...

  5. Variations in concentrations and fluxes of dimethylsulfide (DMS) from the Indian estuaries

    Digital Repository Service at National Institute of Oceanography (India)

    Viswanadham, R.; Bharathi, M.D.; Sarma, V.V.S.S.

    . Biogeochemistry 83: 245-275. Suzuki, R., and T. Ishimaru. 1990. An improved method for the determination of phytoplankton chlorophyll using N,N-dimethylformamide. Journal of Oceanography 46: 190-194. Turner, S.M., G. Malin, P. Liss, D.S. Harbour, and P...

  6. Production of macroaggregates from dissolved exopolymeric substances (EPS) of bacterial and diatom origin

    Digital Repository Service at National Institute of Oceanography (India)

    Bhaskar, P.V.; Grossart, H.P.; Bhosle, N.B.; Simon, M.

    the UGC-DAAD fellowship given to PVB. This work was also supported by the Deutsche Forschungsgemeinschaft within the Research Group ?BioGeoChemistry of the Wadden Sea? (TP-5). We thank Birgit K?rzel and Yvonne Hilker for their assistance...

  7. Development and Application of Flow Duration Curves for Stream Restoration

    Science.gov (United States)

    2016-02-01

    biogeochemistry. Palmer and Bernhardt (2006) identify the linking of hydrologic processes with ecological outcomes as a starting point for effective, holistic...Bledsoe. 2009. Streams and urbanization. Chapter 6 In The Water Environment of Cities, ed. L. A. Baker, 93-123. New York: Springer . Bratkovich, S., L

  8. Dynamics of organic and inorganic carbon across contiguous mangrove and seagrass systems (Gazi Bay, Kenya)

    NARCIS (Netherlands)

    Bouillon, S.; Dehairs, F.; Velimirov, B.; Abril, G.; Borges, A.V.

    2007-01-01

    We report on the water column biogeochemistry in adjacent mangrove and seagrass systems in Gazi Bay (Kenya), with a focus on assessing the sources and cycling of organic and inorganic carbon. Mangrove and seagrass-derived material was found to be the dominant organic carbon sources in the water colu

  9. Carbon sources in the North Sea evaluated by means of radium and stable carbon isotope tracers

    NARCIS (Netherlands)

    Burt, W.J.; Thomas, H.; Hagens, M.; Pätsch, J.; Clargo, N.; Salt, L.A.; Winde, V.; Böttcher, M.E.

    2016-01-01

    A multitracer approach is applied to assess the impact of boundary fluxes (e.g., benthic input from sedimentsor lateral inputs from the coastline) on the acid-base buffering capacity, and overall biogeochemistry,of the North Sea. Analyses of both basin-wide observations in the North Sea and transect

  10. Radium isotopes as a tracer of sediment-water column exchange in the North Sea

    NARCIS (Netherlands)

    Burt, W. J.; Thomas, H.; Paetsch, J.; Omar, A. M.; Schrum, C.; Daewel, U.; Brenner, H.; de Baar, H. J. W.

    2014-01-01

    Sediment-water column exchange plays an important role in coastal biogeochemistry. We utilize short-lived radium isotopes (Ra-224 and Ra-223) to understand and quantify the dominant processes governing sediment-water column exchange throughout the North Sea. Our comprehensive survey, conducted in Se

  11. The Thermodynamics of Marine Biogeochemical Cycles: Lotka Revisited.

    Science.gov (United States)

    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.

  12. The Thermodynamics of Marine Biogeochemical Cycles: Lotka Revisited

    Science.gov (United States)

    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.

  13. Nutrient dynamics, transfer and retention along the aquatic continuum from land to ocean: towards integration of ecological and biogeochemical models

    Directory of Open Access Journals (Sweden)

    A. F. Bouwman

    2013-01-01

    Full Text Available In river basins, soils, groundwater, riparian zones and floodplains, streams, rivers, lakes and reservoirs act as successive filters in which the hydrology, ecology and biogeochemical processing are strongly coupled and together act to retain a significant fraction of the nutrients transported. This paper compares existing river ecology concepts with current approaches to describe river biogeochemistry, and assesses the value of these concepts and approaches for understanding the impacts of interacting global change disturbances on river biogeochemistry. Through merging perspectives, concepts, and modeling techniques, we propose integrated model approaches that encompass both aquatic and terrestrial components in heterogeneous landscapes. In this model framework, existing ecological and biogeochemical concepts are extended with a balanced approach for assessing nutrient and sediment delivery, on the one hand, and nutrient in-stream retention on the other hand.

  14. Groundwater-Surface Water Mixing Shifts Ecological Assembly Processes and Stimulates Organic Carbon Turnover

    Science.gov (United States)

    Stegen, J.; Fredrickson, J.; Wilkins, M.; Konopka, A.; Nelson, W.; Arntzen, E.; Chrisler, W.; Chu, R. K.; Danczak, B.; Fansler, S.; Kennedy, D.; Resch, T.; Tfaily, M. M.

    2015-12-01

    Environmental transitions often result in resource mixtures that overcome limitations to microbial metabolism, resulting in biogeochemical hot spots and moments. Riverine systems where groundwater mixes with surface water (the hyporheic zone) are spatially complex and temporally dynamic, making development of predictive models challenging. Spatial and temporal variations in hyporheic zone microbial communities are a key, but understudied, component of riverine biogeochemical function. To investigate the coupling among groundwater-surface water mixing, microbial communities, and biogeochemistry we applied ecological theory, aqueous biogeochemistry, DNA sequencing, and ultra-high resolution organic carbon profiling to field samples collected across times and locations representing a broad range of mixing conditions. Our results indicate that groundwater-surface water mixing in the hyporheic zone simultaneously (i) stimulated heterotrophic respiration, (ii) altered organic carbon composition, (iii) caused ecological processes to shift from stochastic to deterministic, and (iv) selected for microbial taxa capable of degrading a broad suite of organic compounds.

  15. Improving Intercomparability of Marine Biogeochemical Time Series

    Science.gov (United States)

    Benway, Heather M.; Telszewski, Maciej; Lorenzoni, Laura

    2013-04-01

    Shipboard biogeochemical time series represent one of the most valuable tools scientists have to quantify marine elemental fluxes and associated biogeochemical processes and to understand their links to changing climate. They provide the long, temporally resolved data sets needed to characterize ocean climate, biogeochemistry, and ecosystem variability and change. However, to monitor and differentiate natural cycles and human-driven changes in the global oceans, time series methodologies must be transparent and intercomparable when possible. To review current shipboard biogeochemical time series sampling and analytical methods, the International Ocean Carbon Coordination Project (IOCCP; http://www.ioccp.org/) and the Ocean Carbon and Biogeochemistry Program (http://www.us-ocb.org/) convened an international ocean time series workshop at the Bermuda Institute for Ocean Sciences.

  16. The formation of the ocean’s anthropogenic carbon reservoir

    Science.gov (United States)

    Iudicone, Daniele; Rodgers, Keith B.; Plancherel, Yves; Aumont, Olivier; Ito, Takamitsu; Key, Robert M.; Madec, Gurvan; Ishii, Masao

    2016-11-01

    The shallow overturning circulation of the oceans transports heat from the tropics to the mid-latitudes. This overturning also influences the uptake and storage of anthropogenic carbon (Cant). We demonstrate this by quantifying the relative importance of ocean thermodynamics, circulation and biogeochemistry in a global biochemistry and circulation model. Almost 2/3 of the Cant ocean uptake enters via gas exchange in waters that are lighter than the base of the ventilated thermocline. However, almost 2/3 of the excess Cant is stored below the thermocline. Our analysis shows that subtropical waters are a dominant component in the formation of subpolar waters and that these water masses essentially form a common Cant reservoir. This new method developed and presented here is intrinsically Lagrangian, as it by construction only considers the velocity or transport of waters across isopycnals. More generally, our approach provides an integral framework for linking ocean thermodynamics with biogeochemistry.

  17. Paleodust variability since the Last Glacial Maximum and implications for iron inputs to the ocean

    Science.gov (United States)

    Albani, S.; Mahowald, N. M.; Murphy, L. N.; Raiswell, R.; Moore, J. K.; Anderson, R. F.; McGee, D.; Bradtmiller, L. I.; Delmonte, B.; Hesse, P. P.; Mayewski, P. A.

    2016-04-01

    Changing climate conditions affect dust emissions and the global dust cycle, which in turn affects climate and biogeochemistry. In this study we use observationally constrained model reconstructions of the global dust cycle since the Last Glacial Maximum, combined with different simplified assumptions of atmospheric and sea ice processing of dust-borne iron, to provide estimates of soluble iron deposition to the oceans. For different climate conditions, we discuss uncertainties in model-based estimates of atmospheric processing and dust deposition to key oceanic regions, highlighting the large degree of uncertainty of this important variable for ocean biogeochemistry and the global carbon cycle. We also show the role of sea ice acting as a time buffer and processing agent, which results in a delayed and pulse-like soluble iron release into the ocean during the melting season, with monthly peaks up to ~17 Gg/month released into the Southern Oceans during the Last Glacial Maximum (LGM).

  18. Marine phytoplankton and the changing ocean iron cycle

    Science.gov (United States)

    Hutchins, D. A.; Boyd, P. W.

    2016-12-01

    The availability of the micronutrient iron governs phytoplankton growth across much of the ocean, but the global iron cycle is changing rapidly due to accelerating acidification, stratification, warming and deoxygenation. These mechanisms of global change will cumulatively affect the aqueous chemistry, sources and sinks, recycling, particle dynamics and bioavailability of iron. Biological iron demand will vary as acclimation to environmental change modifies cellular requirements for photosynthesis and nitrogen acquisition and as adaptive evolution or community shifts occur. Warming, acidification and nutrient co-limitation interactions with iron biogeochemistry will all strongly influence phytoplankton dynamics. Predicting the shape of the future iron cycle will require understanding the responses of each component of the unique biogeochemistry of this trace element to many concurrent and interacting environmental changes.

  19. Quantification of ammonia oxidation rates and the distribution of ammonia-oxidizing Archaea and Bacteria in marine sediment depth profiles from Catalina Island, California

    OpenAIRE

    J. Michael eBeman; Victoria Jean Bertics; Thomas eBraunschweiler; Jesse eWilson

    2012-01-01

    Microbial communities present in marine sediments play a central role in nitrogen biogeochemistry at local to global scales. Along the oxidation-reduction gradients present in sediment profiles, multiple nitrogen cycling processes (such as nitrification, denitrification, nitrogen fixation, and anaerobic ammonium oxidation) are active and actively coupled to one another—yet the microbial communities responsible for these transformations and the rates at which they occur are still poorly under...

  20. Quantification of ammonia oxidation rates and the distribution of ammonia-oxidizing Archaea and Bacteria in marine sediment depth profiles from Catalina Island, California

    OpenAIRE

    Beman, J. M.; Bertics, Victoria J.; Braunschweiler, Thomas; Wilson, Jesse M.

    2012-01-01

    Microbial communities present in marine sediments play a central role in nitrogen biogeochemistry at local to global scales. Along the oxidation–reduction gradients present in sediment profiles, multiple nitrogen cycling processes (such as nitrification, denitrification, nitrogen fixation, and anaerobic ammonium oxidation) are active and actively coupled to one another – yet the microbial communities responsible for these transformations and the rates at which they occur are still poorly unde...

  1. 2011 U.S. Pacific Environmental Security Conference (PESC) held in Honolulu, Hawaii on 14-17 March 2011

    Science.gov (United States)

    2011-03-01

    measures must be updated because of new diseases and health threats. There are also logistic chal- lenges to delivery systems. Mr. Bowling pointed out...areas: • Coral diseases of Hawaii • Evolutionary biology • Sequencing of the coral genome • Coral reef biogeochemistry The UH has also been doing...would see 50-plus days a year above 90 degrees Fahr - enheit. The impact of these higher temperatures would be less 103 mountain snowpack and greater

  2. Our Changing Planet: The U.S. Climate Change Science Program for Fiscal Years 2004 and 2005

    Science.gov (United States)

    2004-07-01

    and climate change. Ice Sheet Glaciers Ocean Circulation, Sea Level, Biogeochemistry H2O, CO2 , CH4, N2O, O3, etc. Aerosols Clouds ATMOSPHERIC... paleoclimate data will provide long-term context for recent observed temperature increases. within 2 years Reanalyses of historical climate data for...and implications for the global carbon cycle. The buildup of CO2 and methane in the atmosphere and the fraction of carbon being taken up by North

  3. The U.S. Climate Change Science Program. Vision for the Program and Highlights of the Scientific Strategic Plan

    Science.gov (United States)

    2003-07-01

    issue that must be addressed by the world.” – President Bush, June 11, 2001 Ice Sheet Glaciers Ocean Circulation, Sea Level, Biogeochemistry H2O, CO2 ... paleoclimate data will provide long- term context for recent observed temperature increases. within 2 years Reanalyses of historical climate data for key...of CO2 and methane in the atmosphere and the frac- tion of carbon being taken up by North America’s ecosystems and coastal oceans are key factors in

  4. Extracellular electron transfer mechanism in Shewanella loihica PV- 4 biofilms formed at indium tin oxide and graphite electrodes

    OpenAIRE

    2013-01-01

    Electroactive biofilms are capable of extracellular electron transfer to insoluble metal oxides and electrodes; such biofilms are relevant to biogeochemistry, bioremediation, and bioelectricity production. We investigated the extracellular electron transfer mechanisms in Shewanella loihica PV-4 viable biofilms grown at indium tin oxide (ITO) and graphite electrodes in potentiostat-controlled electrochemical cells poised at 0.2 V vs. Ag/AgCl. Chronoamperometry and confocal microscopy showed hi...

  5. Soil Temperature and Moisture Effects on Soil Respiration and Microbial Community Abundance

    Science.gov (United States)

    2015-04-13

    we assessed their abundance. Commonly, the response of ammonia oxidizers (Avrahami and Bohannan 2007), nitrifiers, and denitrifiers (Stres et al...snowfall. Soil Biology and Biochemistry 57:217–227. Avrahami, S., and B. J. M. Bohannan. 2007. Response of Nitrosospira sp. Strain AF-like ammonia ...Sullivan, and N. C. van Gestel. 2011. The temperature responses of soil respiration in deserts: a seven desert synthesis . Biogeochemistry 103:71–90

  6. Ocean iron fertilization - Moving forward in a sea of uncertainty

    Digital Repository Service at National Institute of Oceanography (India)

    Buesseler, K.O.; Doney, S.C.; Karl, D.M.; Boyd, P.W.; Caldeira, K.; Chai, F.; Coale, K.H.; de Baar, H.J.W.; Falkowski, P.G.; Johnson, K.S.; Lampitt, R.S.; Michaels, A.F.; Naqvi, S.W.A.; Smetacek, V.; Takeda, S.; Watson, A.J.

    , better ecosystem parame- terization, inclusion of other greenhouse gases, and improved iron biogeochemistry. • Analysis of the costs, benefits, and impacts of OIF relative to other climate and carbon mitigation schemes and to the impacts of global change... potential risks, as well as potential benefits; moving forward on OIF should only be done if society is willing to acknowledge explic- itly that it will result in alteration of ocean ecosystems and that some of the conse- quences may be unforeseen. We...

  7. Microbial dynamics in natural aquifers

    OpenAIRE

    Bajracharya, Bijendra Man

    2016-01-01

    Microorganisms in groundwater form ecosystems that can transform chemical compounds. Quantitatively understanding microbial dynamics in soils and groundwater is thus essential for pollutant dynamics and biogeochemistry in the subsurface. This dissertation addresses three factors influencing microbial dynamics in aquifers and soils, namely: (1) the influence of grazing on bacteria in eutrophic aquifers, posing the question whether the carrying capacity of bacteria, which has been observed i...

  8. CLM4-BeTR, a generic biogeochemical transport and reaction module for CLM4: model development, evaluation, and application

    Directory of Open Access Journals (Sweden)

    J. Tang

    2012-09-01

    Full Text Available To improve regional and global biogeochemistry modeling and climate predictability, we have developed a generic reactive transport module for the land model CLM4 (called CLM4-BeTR (Biogeochemical Transport and Reactions. CLM4-BeTR represents the transport, interactions, and biotic and abiotic transformations of an arbitrary number of tracers (aka chemical species in an arbitrary number of phases (e.g. dissolved, gaseous, sorbed, aggregate. An operator splitting approach was employed and consistent boundary conditions were derived for each modeled sub-process. Tracer fluxes, associated with hydrological processes such as surface run-on and run-off, belowground drainage, and ice to liquid conversion were also computed consistently with the bulk water fluxes calculated by the soil physics module in CLM4. The transport code was evaluated and found be in good agreement with several analytical test cases. The model was then applied at the Harvard Forest site with a representation of depth-dependent belowground biogeochemistry. The results indicated that, at this site, (1 CLM4-BeTR was able to simulate soil-surface CO2 effluxes and soil CO2 profiles accurately; (2 the transient surface CO2 effluxes calculated based on the tracer transport mechanism were in general not equal to the belowground CO2 production rates and that their differences varied according to the seasonal cycle of soil physics and biogeochemistry; (3 losses of CO2 through processes other than surface gas efflux were less than 1% of the overall soil respiration; and (4 the contributions of root respiration and heterotrophic respiration have distinct temporal signals in surface CO2 effluxes and soil CO2 concentrations. The development of CLM4-BeTR will allow detailed comparisons between ecosystem observations and predictions and insights to the modeling of terrestrial biogeochemistry.

  9. Beyond Interdisciplinarity: Integrated Climate System Sciences at University of Hamburg

    Science.gov (United States)

    Beckmann, Aike; Eden, Carsten; Hachfeld, Berit; Harms, Ingo; Held, Hermann; Hort, Matthias

    2013-04-01

    We present the philosophy and implementation of a combined MSc and PhD study program in climate system sciences (SICCS) that bring together environmental physics, geoscience, biogeochemistry and climate related economic and social sciences. The philosophy of SICCS includes the perspective for both students and lectures to work on, to develop and to communicate an integrative "world map" of climate and earth science. We report about first results, difficulties and experiences after successful implementation of the program.

  10. Photosynthetic Versatility in the Genome of Geitlerinema sp. PCC 9228 (Formerly Oscillatoria limnetica ‘Solar Lake’), a Model Anoxygenic Photosynthetic Cyanobacterium

    OpenAIRE

    2016-01-01

    Anoxygenic cyanobacteria that use sulfide as the electron donor for photosynthesis are a potentially influential but poorly constrained force on Earth’s biogeochemistry. Their versatile metabolism may have boosted primary production and nitrogen cycling in euxinic coastal margins in the Proterozoic. In addition, they represent a biological mechanism for limiting the accumulation of atmospheric oxygen, especially before the Great Oxidation Event and in the low-oxygen conditions of the Proteroz...

  11. Critical load of atmospheric nitrogen deposition in French forests: modelling soil and vegetation response in a context of climate change

    OpenAIRE

    Rizzetto, Simon; Gaudio, Noémie; Belyazid, Salim; Gégout, Jean-Claude; Alard, Didier; Corcket, Emmanuel; Sverdrup, Harald; Probst, Anne

    2014-01-01

    Anthropogenic activities highly contributed to increased nitrogen and sulfur atmospheric emissions since 1880. Nitrogen deposition is known to severely impact ecosystem functioning by infl uencing soil biogeochemistry, nutrient balance, and consequently tree growth, forest health, and biodiversity. Since the 1980s, within the Geneva Convention on Long-Range Transboundary Air Pollution, European countries have joined their efforts to abate atmospheric pollution. The concept of N critical loads...

  12. Nitrogen fixation amplifies the ocean biogeochemical response to decadal timescale variations in mineral dust deposition

    OpenAIRE

    Moore, J. Keith; Doney, Scott C.; Lindsay, Keith; Mahowald, Natalie; Michaels, Anthony F.

    2011-01-01

    A global ocean biogeochemical model is used to quantify the sensitivity of marine biogeochemistry and air–sea CO2 exchange to variations in dust deposition over decadal timescales. Estimates of dust deposition generated under four climate states provide a large range in total deposition with spatially realistic patterns; transient ocean model experiments are conducted by applying a step-function change in deposition from a current climate control. Relative to current conditions, higher dust d...

  13. Atmospheric iron deposition: global distribution, variability, and human perturbations

    OpenAIRE

    N. Mahowald; S. Engelstaedter; Luo, C; Sealy, A.; Artaxo, P.; Benitez-Nelson, C.R.; Bonnet, S.; Chen, Y.; Chuang, P. Y.; Cohen, D.; Dulac, F.; B. Herut; Johansen, A.M.; N. Kubilay; Losno, R.

    2009-01-01

    Atmospheric inputs of iron to the open ocean are hypothesized to modulate ocean biogeochemistry. This review presents an integration of available observations of atmospheric iron and iron deposition, and also covers bioavailable iron distributions. Methods for estimating temporal variability in ocean deposition over the recent past are reviewed. Desert dust iron is estimated to represent 95% of the global atmospheric iron cycle, and combustion sources of iron are responsible for the remaining...

  14. Disassembling Iron Availability to Phytoplankton

    OpenAIRE

    2012-01-01

    The bioavailability of iron to microorganisms and its underlying mechanisms have far reaching repercussions to many natural systems and diverse fields of research, including ocean biogeochemistry, carbon cycling and climate, harmful algal blooms, soil and plant research, bioremediation, pathogenesis, and medicine. Within the framework of ocean sciences, short supply and restricted bioavailability of Fe to phytoplankton is thought to limit primary production and curtail atmospheric CO2 drawdow...

  15. Disassembling iron availability to phytoplankton

    OpenAIRE

    2012-01-01

    The bioavailability of iron to microorganisms and its underlying mechanisms have far reaching repercussions to many natural systems and diverse fields of research, including ocean biogeochemistry, carbon cycling and climate, harmful algal blooms, soil and plant research, bioremediation, pathogenesis and medicine. Within the framework of ocean sciences, short supply and restricted bioavailability of Fe to phytoplankton is thought to limit primary production and curtail atmospheric CO2 drawdown...

  16. Influence of anthropogenic aerosol deposition on the relationship between oceanic productivity and warming

    OpenAIRE

    Wang, Rong; Balkanski, Yves; Bopp, Laurent; Aumont, Olivier; Boucher, Olivier; Ciais, Philippe; Gehlen, Marion; Peñuelas, Josep; Éthé, Christian; Hauglustaine, Didier; Li, Bengang; Liu, Junfeng; Zhou, Feng; TAO, SHU

    2015-01-01

    International audience; Satellite data and models suggest that oceanic productivity is reduced in response to less nutrient supply under warming. In contrast, anthropogenic aerosols provide nutrients and exert a fertilizing effect, but its contribution to evolution of oceanic productivity is unknown. We simulate the response of oceanic biogeochemistry to anthropogenic aerosols deposition under varying climate from 1850 to 2010. We find a positive response of observed chlorophyll to deposition...

  17. Organic biomarkers in deep-sea regions affected by bottom trawling: pigments, fatty acids, amino acids and carbohydrates in surface sediments from the La Fonera (Palamós) Canyon, NW Mediterranean Sea

    OpenAIRE

    E. Sañé; Martín, J.; Puig, P.; Palanques, A.

    2013-01-01

    Deep-sea ecosystems are in general adapted to a limited variability of physical conditions, resulting in high vulnerability and slow recovery rates from anthropogenic perturbations such as bottom trawling. Commercial trawling is the most recurrent and pervasive of human impacts on the deep-sea floor, but studies on its consequences on the biogeochemistry of deep-sea sediments are still scarce. Pigments, fatty acids, amino acids and carbohydrates were analysed in sediments fr...

  18. Organic biomarkers in deep-sea regions affected by bottom trawling: pigments, fatty acids, amino acids and carbohydrates in surface sediments from the La Fonera (Palamós) Canyon, NW Mediterranean Sea

    OpenAIRE

    E. Sañé; Martín, J.; Puig, P.; Palanques, A.

    2012-01-01

    Deep-sea ecosystems are in general adapted to a limited variability of physical conditions, resulting in high vulnerability and slow recovery rates from anthropogenic perturbations such as bottom trawling. Commercial trawling is the most recurrent and pervasive of human impacts on the deep-sea floor, but studies on its consequences on the biogeochemistry of deep-sea sediments are still scarce. Pigments, fatty acids, amino acids and carbohydrates were analyzed in sediments from the flanks of t...

  19. Atmospheric deposition impacts on nutrients and biological budgets of the Mediterranean Sea, results from the high resolution coupled model NEMOMED12/PISCES

    Science.gov (United States)

    Richon, Camille; Dutay, Jean-Claude; Dulac, François; Desboeufs, Karine; Nabat, Pierre; Guieu, Cécile; Aumont, Olivier; Palmieri, Julien

    2016-04-01

    Atmospheric deposition is at present not included in regional oceanic biogeochemical models of the Mediterranean Sea, whereas, along with river inputs, it represents a significant source of nutrients at the basin scale, especially through intense desert dust events. Moreover, observations (e.g. DUNE campaign, Guieu et al. 2010) show that these events significantly modify the biogeochemistry of the oligotrophic Mediterranean Sea. We use a high resolution (1/12°) version of the 3D coupled model NEMOMED12/PISCES to investigate the effects of high resolution atmospheric dust deposition forcings on the biogeochemistry of the Mediterranean basin. The biogeochemical model PISCES represents the evolution of 24 prognostic tracers including five nutrients (nitrate, ammonium, phosphate, silicate and iron) and two phytoplankton and zooplanktons groups (Palmiéri, 2014). From decadal simulations (1982-2012) we evaluate the influence of natural dust and anthropogenic nitrogen deposition on the budget of nutrients in the basin and its impact on the biogeochemistry (primary production, plankton distributions...). Our results show that natural dust deposition accounts for 15% of global PO4 budget and that it influences primarily the southern part of the basin. Anthropogenic nitrogen accounts for 50% of bioavailable N supply for the northern part. Deposition events significantly affect biological production; primary productivity enhancement can be as high as 30% in the areas of high deposition, especially during the stratified period. Further developments of the model will include 0D and 1D modeling of bacteria in the frame of the PEACETIME project.

  20. Silicon and zinc biogeochemical cycles coupled through the Southern Ocean

    Science.gov (United States)

    Vance, Derek; Little, Susan H.; de Souza, Gregory F.; Khatiwala, Samar; Lohan, Maeve C.; Middag, Rob

    2017-02-01

    Zinc is vital for the physiology of oceanic phytoplankton. The striking similarity of the depth profiles of zinc to those of silicate suggests that the uptake of both elements into the opaline frustules of diatoms, and their regeneration from these frustules, should be coupled. However, the zinc content of diatom opal is negligible, and zinc is taken up into and regenerated from the organic parts of diatom cells. Thus, since opaline frustules dissolve deep in the water column while organic material is regenerated in the shallow subsurface ocean, there is little reason to expect the observed close similarity between zinc and silicate, and the dissimilarity between zinc and phosphate. Here we combine observations with simulations using a three-dimensional model of ocean circulation and biogeochemistry to show that the coupled distribution of zinc and silicate, as well as the decoupling of zinc and phosphate, can arise in the absence of mechanistic links between the uptake of zinc and silicate, and despite contrasting regeneration length scales. Our simulations indicate that the oceanic zinc distribution is, in fact, a natural result of the interaction between ocean biogeochemistry and the physical circulation through the Southern Ocean hub. Our analysis demonstrates the importance of uptake stoichiometry in controlling ocean biogeochemistry, and the utility of global-scale elemental covariation in the ocean in understanding these controls.

  1. Strong sensitivity of Southern Ocean carbon uptake and nutrient cycling to wind stirring

    Directory of Open Access Journals (Sweden)

    K. B. Rodgers

    2013-09-01

    Full Text Available Here we test the hypothesis that winds have an important role in determining the rate of exchange of CO2 between the atmosphere and ocean through wind stirring over the Southern Ocean. This is tested with a sensitivity study using an ad hoc parameterization of wind stirring in an ocean carbon cycle model. The objective is to identify the way in which perturbations to the vertical density structure of the planetary boundary in the ocean impacts the carbon cycle and ocean biogeochemistry. Wind stirring leads to reduced uptake of CO2 by the Southern Ocean over the period 2000–2006, with differences of order 0.9 Pg C yr−1 over the region south of 45° S. Wind stirring impacts not only the mean carbon uptake, but also the phasing of the seasonal cycle of carbon and other species associated with ocean biogeochemistry. Enhanced wind stirring delays the seasonal onset of stratification, and this has large impacts on both entrainment and the biological pump. It is also found that there is a strong sensitivity of nutrient concentrations exported in Subantarctic Mode Water (SAMW to wind stirring. This finds expression not only locally over the Southern Ocean, but also over larger scales through the impact on advected nutrients. In summary, the large sensitivity identified with the ad hoc wind stirring parameterization offers support for the importance of wind stirring for global ocean biogeochemistry, through its impact over the Southern Ocean.

  2. Research on Biogeochemical Cycling of Several Macroelements in Soil%土壤环境中几种常量元素的生物地球化学研究进展

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    通过对生物地球化学的概念以及生物地球环境化学循环进行阐述,进而得出了土壤环境生物地球化学循环的概念。通过对土壤中的生物地球化学循环所存在的物态进行分析,总结出土壤生物地球化学循环所研究的物态包括三种:即固、液、气三相物态。进而提出土壤生物地球化学中的几种主要养分元素碳、氮、磷、硫在液相物质或气相物质影响下,在土壤-生物界面之间进行迁移和传递的研究进展,得出其在生物地球化学循环中的作用。%The concept of biogeochemistry and biological chemical cycle were described as well as soil environmental biogeochemistry cycle. The state of matter in soil during the biogeochemical cycle was analyzed, the state includes three types: solid, liquid, gas phase. Several main nutrient elements in the soil biogeochemistry were put forward, such as carbon, nitrogen, phosphorus and sulfur. Research progress in their migration and transfer between soil and biological interface was discussed, its role in the biogeochemical cycle was obtained.

  3. Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model

    Science.gov (United States)

    Dutkiewicz, S.; Hickman, A. E.; Jahn, O.; Gregg, W. W.; Mouw, C. B.; Follows, M. J.

    2015-02-01

    We present a numerical model of the ocean that couples a three-stream radiative transfer component with a marine biogeochemical-ecosystem in a dynamic three-dimensional physical framework. The radiative transfer component resolves spectral irradiance as it is absorbed and scattered within the water column. We explicitly include the effect of several optically important water constituents (the phytoplankton community, detrital particles, and coloured dissolved organic matter, CDOM). The model is evaluated against in situ observed and satellite derived products. In particular we compare to concurrently measured biogeochemical, ecosystem and optical data along a north-south transect of the Atlantic Ocean. The simulation captures the patterns and magnitudes of these data, and estimates surface upwelling irradiance analogous to that observed by ocean colour satellite instruments. We conduct a series of sensitivity experiments to demonstrate, globally, the relative importance of each of the water constituents, and the crucial feedbacks between the light field and the relative fitness of phytoplankton types, and the biogeochemistry of the ocean. CDOM has proportionally more importance at short wavelengths and in more productive waters, phytoplankton absorption is especially important at the deep chlorophyll a (Chl a) maximum, and absorption by water molecules is relatively most important in the highly oligotrophic gyres. Sensitivity experiments in which absorption by any of the optical constituents was increased led to a decrease in the size of the oligotrophic regions of the subtropical gyres: lateral nutrient supplies were enhanced as a result of decreasing high latitude productivity. Scattering does not as strongly affect the ecosystem and biogeochemistry fields within the water column but is important for setting the surface upwelling irradiance, and hence sea surface reflectance. Having a model capable of capturing bio-optical feedbacks will be important for

  4. Absence of snow cover reduces understory plant cover and alters plant community composition in boreal forests.

    Science.gov (United States)

    Kreyling, Juergen; Haei, Mahsa; Laudon, Hjalmar

    2012-02-01

    Snow regimes affect biogeochemistry of boreal ecosystems and are altered by climate change. The effects on plant communities, however, are largely unexplored despite their influence on relevant processes. Here, the impact of snow cover on understory community composition and below-ground production in a boreal Picea abies forest was investigated using a long-term (8-year) snow cover manipulation experiment consisting of the treatments: snow removal, increased insulation (styrofoam pellets), and control. The snow removal treatment caused longer (118 vs. 57 days) and deeper soil frost (mean minimum temperature -5.5 vs. -2.2°C) at 10 cm soil depth in comparison to control. Understory species composition was strongly altered by the snow cover manipulations; vegetation cover declined by more than 50% in the snow removal treatment. In particular, the dominant dwarf shrub Vaccinium myrtillus (-82%) and the most abundant mosses Pleurozium schreberi (-74%) and Dicranum scoparium (-60%) declined strongly. The C:N ratio in V. myrtillus leaves and plant available N in the soil indicated no altered nitrogen nutrition. Fine-root biomass in summer, however, was negatively affected by the reduced snow cover (-50%). Observed effects are attributed to direct frost damage of roots and/ or shoots. Besides the obvious relevance of winter processes on plant ecology and distribution, we propose that shifts in the vegetation caused by frost damage may be an important driver of the reported alterations in biogeochemistry in response to altered snow cover. Understory plant performance clearly needs to be considered in the biogeochemistry of boreal systems in the face of climate change.

  5. GEOCHEMISTRY

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    <正>20102226 Liu Congqiang(State Key Laboratory of Environmental Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550002,China);Lang Yunchao Researches on Biogeochemical Processes and Nutrient Cycling in Karstic Ecological Systems,Southwest China:A review(Earth Science Frontiers,ISSN1005-2321,CN11-3370/P,16(6),2009,p.1-12,36 refs.)Key words:biogeochemistry,karst environmentBased on the previous studies,this paper introduces the researches on biogeochemical processes and nutrient cycling occurri

  6. Spatial variations of DMS, DMSP and phytoplankton in the Bay of Bengal during the summer monsoon 2001

    Digital Repository Service at National Institute of Oceanography (India)

    Shenoy, D; Paul, J.T.; Gauns, M.; Ramaiah, N.; DileepKumar, M.

    ., Holmen, K. and Leck, C., (1993). Experimental determination of the diffusion coefficient of dimethylsulfide in water. J. Geophys. Res., 98, 16481-16486. Sharma, S., Barrie, L. A., Plummer, D., McConnell, J. C., Brickell, P. C., Levasseur, M...). The biogeochemistry of dimethylsulphide in the South China Sea. J. Mar. Res., 57, 189-211. Yang, G. P., Cong, X. D., Zhang, Z.B., & Zhao, W. (2000). Dimethylsulfide in the South China Sea Chin. J. Oceanol. Limnol., 18, 162-168. 18Table 1. Average (range...

  7. Planetary Biology and Microbial Ecology: Molecular Ecology and the Global Nitrogen cycle

    Science.gov (United States)

    Nealson, Molly Stone (Editor); Nealson, Kenneth H. (Editor)

    1993-01-01

    This report summarizes the results of the Planetary Biology and Molecular Ecology's summer 1991 program, which was held at the Marine Biological Laboratory in Woods Hole, Massachusetts. The purpose of the interdisciplinary PBME program is to integrate, via lectures and laboratory work, the contributions of university and NASA scientists and student interns. The goals of the 1991 program were to examine several aspects of the biogeochemistry of the nitrogen cycle and to teach the application of modern methods of molecular genetics to field studies of organisms. Descriptions of the laboratory projects and protocols and abstracts and references of the lectures are presented.

  8. Late holocene primary productivity and sea surface temperature variations in the northeastern Arabian Sea: Implications for winter monsoon variability.

    Digital Repository Service at National Institute of Oceanography (India)

    Boll, A.; Luckge, A.; Munz, P.; Forke, S.; Schulz, H.; Ramaswamy, V.; Rixen, T.; Gaye; Emeis, K.-C.

    , Sven Forke4, Hartmut Schulz3, V. Ramaswamy5, Tim Rixen1,4, Birgit Gaye1, Kay-Christian Emeis6,1 1. Institute of Biogeochemistry and Marine Chemistry, University of Hamburg, Bundesstr. 55, 20146 Hamburg, Germany 2. Bundesanstalt für... al., 2001; Gaye-Haake et al., 2005]. Sediments deposited within the OMZ off Pakistan are characterized by well preserved, varve- like lamination with altering dark and light sediment layers as well as high input of lithogenic material originating...

  9. Sulfide intrusion in the tropical seagrasses Thalassia testudinum and Syringodium filiforme

    DEFF Research Database (Denmark)

    Holmer, Marianne; Pedersen, Ole; Krause-Jensen, Dorte;

    2009-01-01

    and on proximity to anthropogenic nutrient sources. Meadow characteristics (shoot density, above- and below-ground biomass, nutrient content) were sampled along with sediment biogeochemistry. Sulfide intrusion was high in T. testudinum, as up to 96% of total sulfur in the plant was derived from sediment......-derived sulfides. The sulfide intrusion was negatively correlated to the turnover of sulfides in the sediments regulated by both plant parameters and sediment sulfur pools. Sediment iron content played an indirect role by affecting sulfide turnover rates. Leaf production was negatively correlated with sulfide...

  10. The Blue Dot Workshop: Spectroscopic Search for Life on Extrasolar Planets

    Science.gov (United States)

    Des Marais, David J. (Editor)

    1997-01-01

    This workshop explored the key questions and challenges associated with detecting life on an extrasolar planet. The final product will be a NASA Conference Publication which includes the abstracts from 21 talks, summaries of key findings, and recommendations for future research. The workshop included sessions on three related topics: the biogeochemistry of biogenic gases in the atmosphere, the chemistry and spectroscopy of planetary atmospheres, and the remote sensing of planetary atmospheres and surfaces. With the observation that planetary formation is probably a common phenomenon, together with the advent of the technical capability to locate and describe extrasolar planets, this research area indeed has an exciting future.

  11. Preface: Special Issue of the 5th International Symposium on Biological and Environmental Chemistry of DMS(P) and Related Compounds, Goa, India, 19–22 October 2010

    Digital Repository Service at National Institute of Oceanography (India)

    Stefels, J.; Shenoy, D.M.; Simo, R.; Malin, G.; Levasseur, M.; Belviso, S.; DileepKumar, M.

    • Dileep Kumar Published online: 4 August 2012 � Springer Science+Business Media B.V. 2012 This Special Issue of Biogeochemistry contains a selection of papers presented at the 5th International Symposium on Biological and Environmental Chem- istry of DMS... will be held in Barcelona, Spain, will be announced soon. Two major publications in the 80s stimulated the work of this truly international DMS research com- munity. Shaw (1983) was the first to propose a link between ocean biota and Earth’s radiation budget...

  12. Formation and Reactivity of Biogenic Iron Microminerals

    Energy Technology Data Exchange (ETDEWEB)

    Beveridge, Terrance J.; Ferris, F. Grant

    2002-08-10

    Radionuclide and heavy metal contaminants at DOE sites pose immediate and long-term environmental problems. Under the NABIR program, bacteria are being considered for their role in the cycling of these contaminants because they influence many redox reactions in the subsurface. Dissimilatory metal reducing bacteria (DMRB) are particularly important to controlling the biogeochemistry of subsurface environments through enzymatic reduction of iron and manganese minerals. During reduction of FeIII, biogenic FeII phases form at the cell-mineral interface which may profoundly influence metal reduction.

  13. The Development of New User Research Capabilities in Environmental Molecular Science: Workshop Report

    Energy Technology Data Exchange (ETDEWEB)

    Felmy, Andrew R.; Baer, Donald R.; Fredrickson, Jim K.; Gephart, Roy E.; Rosso, Kevin M.

    2006-10-31

    On August 1, and 2, 2006, 104 scientists representing 40 institutions including 24 Universities and 5 National Laboratories gathered at the W.R. Wiley Environmental Molecular Sciences Laboratory, a National scientific user facility, to outline important science challenges for the next decade and identify major capabilities needed to pursue advanced research in the environmental molecular sciences. EMSL’s four science themes served as the framework for the workshop. The four science themes are 1) Biological Interactions and Interfaces, 2) Geochemistry/Biogeochemistry and Surface Science, 3) Atmospheric Aerosol Chemistry, and 4) Science of Interfacial Phenomena.

  14. Phytozome Comparative Plant Genomics Portal

    Energy Technology Data Exchange (ETDEWEB)

    Goodstein, David; Batra, Sajeev; Carlson, Joseph; Hayes, Richard; Phillips, Jeremy; Shu, Shengqiang; Schmutz, Jeremy; Rokhsar, Daniel

    2014-09-09

    The Dept. of Energy Joint Genome Institute is a genomics user facility supporting DOE mission science in the areas of Bioenergy, Carbon Cycling, and Biogeochemistry. The Plant Program at the JGI applies genomic, analytical, computational and informatics platforms and methods to: 1. Understand and accelerate the improvement (domestication) of bioenergy crops 2. Characterize and moderate plant response to climate change 3. Use comparative genomics to identify constrained elements and infer gene function 4. Build high quality genomic resource platforms of JGI Plant Flagship genomes for functional and experimental work 5. Expand functional genomic resources for Plant Flagship genomes

  15. Determination of phosphorus in natural waters: A historical review.

    Science.gov (United States)

    Worsfold, Paul; McKelvie, Ian; Monbet, Phil

    2016-04-28

    The aim of this paper is to introduce a virtual special issue that reviews the development of analytical approaches to the determination of phosphorus species in natural waters. The focus is on sampling and sample treatment, analytical methods and quality assurance of the data. The export of phosphorus from anthropogenic activities (from diffuse and point sources) can result in increased primary production and eutrophication, and potentially the seasonal development of toxic algal blooms, which can significantly impact on water quality. Therefore the quantification of phosphorus species in natural waters provides important baseline data for studying aquatic phosphorus biogeochemistry, assessing ecosystem health and monitoring compliance with legislation.

  16. Changes in the coastal and marine environments

    Digital Repository Service at National Institute of Oceanography (India)

    DeSousa, S.N.; Ahmed, A; DileepKumar, M.; Jagtap, T.G.; Sardessai, S.; Hassan, A

    /plain; charset=UTF-8 10 Changes in the Coastal and Marine Environments S.N. de Sousa, Ahsan Uddin Ahmed, M.D. Kumar, T.G. Jagtap, S. Sardessai and A. Hassan 1. BIOGEOCHEMISTRY OF THE NORTH INDIAN OCEAN The Indian Ocean is bounded in the north... heating and cooling of the northern Indian Ocean, the northwest Pacific and the Asian landmass (Prasanna Kumar et a!., 2004a; Zahn, 2003). At intermediate levels, the two high salinity water masses that are formed in the northwestern region - The Persian...

  17. Meet the Editor: Global Biogeochemical Cycles

    Science.gov (United States)

    Kumar, Mohi

    Meinrat Andreae was named the editor of the AGU's journal Global Biogeochemical Cycles last year.Andreae, director of the biogeochemistry department at the Max Plank Institute for Chemistry (MPIC), located in Mainz, Germany said that he plans to maintain the journal as a resource that highlights the broad spectrum of interdisciplinary themes that showcase the interactions between the biosphere and the geosphere. “Our special niche is in the field of larger-scale, more integrative studies that have global scope,” he explained.

  18. Distribution and ecology of the Trichodesmium spp. in the Arabian Sea: Ship and satellite studies

    Digital Repository Service at National Institute of Oceanography (India)

    Parab, S.G.; Matondkar, S.G.P.; Raman, M.; Dwivedi, R.M.

    by HPLC (Wright et al., 1991; Bidigare and Charles, 2002). Pigments were separated in a C-18 reverse-phase column using the eluent gradient program of Wright, et al. (1991) as adapted by Bidigare and Charles (2002) as detailed in Parab, et al. (2006...., 2011. Enumeration of bacteria from a Trichodesmium spp. bloom of the eastern Arabian Sea: Elucidation of their possible role in biogeochemistry. Journal of Applied Phycology 23, 309-319. 4. Bidigare, R. G., Charles, C. T., 2002. HPLC phytoplankton...

  19. Seeing the unseen-bioturbation in 4D

    DEFF Research Database (Denmark)

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

    2015-01-01

    Understanding spatial and temporal patterns of bioirrigation induced by benthic fauna ventilation is critical given its significance on benthic nutrient exchange and biogeochemistry in coastal ecosystems. The quantification of this process challenges marine scientists because faunal activities...... and behaviors are concealed in an opaque sediment matrix. Here, we use a hybrid medical imaging technique, positron emission tomography and computed tomography (PET/CT) to provide a qualitative visual and fully quantitative description of bioirrigation in 4D (space and time). As a study case, we present images...

  20. Isolation of Phyllosilicate–Iron Redox Cycling Microorganisms from an Illite–Smectite Rich Hydromorphic Soil

    OpenAIRE

    Shelobolina, Evgenya S.; Hiromi eKonishi; Huifang eXu; Jason eBenzine; Mai Yia eXiong; Tao eWu; Marco eBlöthe; Eric eRoden

    2012-01-01

    The biogeochemistry of phyllosilicate–Fe redox cycling was studied in a Phalaris arundinacea (reed canary grass) dominated redoximorphic soil from Shovelers Sink, a small glacial depression near Madison, WI. The clay size fraction of Shovelers Sink soil accounts for 16% of the dry weight of the soil, yet contributes 74% of total Fe. The dominant mineral in the clay size fraction is mixed layer illite–smectite, and in contrast to many other soils and sediments, Fe(III) oxides are present in lo...

  1. Arctic River organic matter transport

    Science.gov (United States)

    Raymond, Peter; Gustafsson, Orjan; Vonk, Jorien; Spencer, Robert; McClelland, Jim

    2016-04-01

    Arctic Rivers have unique hydrology and biogeochemistry. They also have a large impact on the Arctic Ocean due to the large amount of riverine inflow and small ocean volume. With respect to organic matter, their influence is magnified by the large stores of soil carbon and distinct soil hydrology. Here we present a recap of what is known of Arctic River organic matter transport. We will present a summary of what is known of the ages and sources of Arctic River dissolved and particulate organic matter. We will also discuss the current status of what is known about changes in riverine organic matter export due to global change.

  2. Biostimulation

    Energy Technology Data Exchange (ETDEWEB)

    Hazen, Terry C.

    2009-03-01

    Biostimulation is one of the most mature methods of bioremediation of hydrocarbons, yet recent advances in geophysics, stable isotope analyses, and molecular microbiology promise dramatic increases in the depth, breadth, and throughput of biostimulation strategies. Using a systems biology approach we can now understand not only what microbes are present, but their in situ activities to trace nutrients, electron donors, electron acceptors, contaminants, and environmental stressors. Using this knowledge in combination with critical biogeochemistry, hydrology, geology, and toxicology will be enabling to develop conceptual and numerical models for the best biostimulation strategy and better long-term stewardship of the environment.

  3. Mid-Pacific Marine Laboratory. Annual report for the period, 1 October 1977--30 September 1978

    Energy Technology Data Exchange (ETDEWEB)

    Reese, E.S.; Johnson, V.R. Jr.

    1979-03-01

    Studies on behavior included reproduction and sociobiology of reef fishes and aggression, hearing, and ultrasonic telemetry in sharks. Ecological studies included population, growth, and mortality studies on birds, corals, crustacea, echinoderms, fishes, molluscs, and rats. Geochemistry studies included biogeochemistry of reef organisms and hydrogeochemistry of groundwater. Geology studies included bioerosion of sea urchins, biology of endolithic processes, and survey of soils. Oceanography studies were conducted on lagoon circulation. Physiological studies were conducted on symbiosis in corals and utilization of organic material by Foraminifera. Studies on systematics of algae, echinoderms, and fishes were conducted. (HLW)

  4. Evaluating the ocean biogeochemical components of earth system models using atmospheric potential oxygen (APO and ocean color data

    Directory of Open Access Journals (Sweden)

    C. D. Nevison

    2014-06-01

    Full Text Available The observed seasonal cycles in atmospheric potential oxygen (APO at a range of mid to high latitude surface monitoring sites are compared to those inferred from the output of 6 Earth System Models participating in the fifth phase of the Coupled Model Intercomparison Project (CMIP5. The simulated air–sea O2 fluxes are translated into APO seasonal cycles using a matrix method that takes into account atmospheric transport model (ATM uncertainty among 13 different ATMs. Half of the ocean biogeochemistry models tested are able to reproduce the observed APO cycles at most sites, to within the current large ATM uncertainty, while the other half generally are not. Net Primary Production (NPP and net community production (NCP, as estimated from satellite ocean color data, provide additional constraints, albeit more with respect to the seasonal phasing of ocean model productivity than the overall magnitude. The present analysis suggests that, of the tested ocean biogeochemistry models, CESM and GFDL ESM2M are best able to capture the observed APO seasonal cycle at both Northern and Southern Hemisphere sites. In the northern oceans, the comparison to observed APO suggests that most models tend to underestimate NPP or deep ventilation or both.

  5. Saharan dust enhances carbon sequestration in the North Atlantic

    Science.gov (United States)

    Pabortsava, Katsiaryna; Lampitt, Richard; Le Moigne, Frederic; Sanders, Richard; Statham, Peter

    2016-04-01

    We present unique time-series data from sediment traps deployed at 3000 m depth in the subtropical North (NOG) and South (SOG) Atlantic oligotrophic gyres during 2007-2010. The sampling sites have similar physical properties and carbon fixation rates but different surface ocean biogeochemistry owing to enhanced input of Saharan dust in the North. NOG and SOG sites are thus ideal to investigate the effects of dust input on carbon sequestration in low-nutrient low-chlorophyll oceans. Analyses of the trap material (chemical, microscopic and stable isotope) revealed significant inter-basin differences in the downward particle flux and its composition, showing that biogeochemical differences at the surface have major effects on deep ocean sequestration scenarios. Particulate organic carbon flux in the dustier Northern gyre was twice that in the dust-poor Southern gyre. We conclude that this is a consequence of tight coupling between fertilization and ballasting due to dust deposition. We suggest that excess of micronutrient Fe from the dust increased phytoplankton biomass by stimulating di-nitrogen fixation, while dust particles caused rapid and more efficient transport to depth via ballasting. These findings present compelling direct evidence of two distinct biogeochemical provinces in the subtropical oligotrophic Atlantic not only with respect to surface nutrient biogeochemistry but also with respect to carbon sequestration.

  6. Watershed responses to Amazon soya bean cropland expansion and intensification.

    Science.gov (United States)

    Neill, Christopher; Coe, Michael T; Riskin, Shelby H; Krusche, Alex V; Elsenbeer, Helmut; Macedo, Marcia N; McHorney, Richard; Lefebvre, Paul; Davidson, Eric A; Scheffler, Raphael; Figueira, Adelaine Michela e Silva; Porder, Stephen; Deegan, Linda A

    2013-06-05

    The expansion and intensification of soya bean agriculture in southeastern Amazonia can alter watershed hydrology and biogeochemistry by changing the land cover, water balance and nutrient inputs. Several new insights on the responses of watershed hydrology and biogeochemistry to deforestation in Mato Grosso have emerged from recent intensive field campaigns in this region. Because of reduced evapotranspiration, total water export increases threefold to fourfold in soya bean watersheds compared with forest. However, the deep and highly permeable soils on the broad plateaus on which much of the soya bean cultivation has expanded buffer small soya bean watersheds against increased stormflows. Concentrations of nitrate and phosphate do not differ between forest or soya bean watersheds because fixation of phosphorus fertilizer by iron and aluminium oxides and anion exchange of nitrate in deep soils restrict nutrient movement. Despite resistance to biogeochemical change, streams in soya bean watersheds have higher temperatures caused by impoundments and reduction of bordering riparian forest. In larger rivers, increased water flow, current velocities and sediment flux following deforestation can reshape stream morphology, suggesting that cumulative impacts of deforestation in small watersheds will occur at larger scales.

  7. Effects of ozone depletion and UV-B radiation on humans and the environment

    Energy Technology Data Exchange (ETDEWEB)

    Solomon, K.R. [Guelph Univ., ON (Canada). Centre for Toxicology

    2008-03-15

    This paper summarized current research related to the effects of ultraviolet (UV-B) radiation on human health and the environment. Effects included direct responses in human as well as effects on biogeochemistry and the environmental cycling of substances. UV radiation has many harmful effects on the skin, eyes, and immune systems of humans. Skin cancer is a leading cause of death among fair-skinned populations exposed to UV radiation. The role of UV radiation in cataract formation was discussed, as well as issues related to the suppression of immune responses. The link between sunlight exposure and vitamin D levels in human populations was examined. The effects of UV radiation on terrestrial and aquatic ecosystems were reviewed. Issues related to biogeochemistry and atmospheric processes were discussed. The review suggested that changes in the intensity of solar UV radiation due to ozone depletion will have important repercussions for all organisms on the planet. It was concluded that the combined effects of UV-B radiation and climate change will not be easy to predict. 201 refs., 4 figs.

  8. Natural ocean carbon cycle sensitivity to parameterizations of the recycling in a climate model

    Directory of Open Access Journals (Sweden)

    A. Romanou

    2013-07-01

    Full Text Available Sensitivities of the oceanic biological pump within the GISS climate modeling system are explored here. Results are presented from twin control simulations of the air-sea CO2 gas exchange using two different ocean models coupled to the same atmosphere. The two ocean models (Russell ocean model and Hybrid Coordinate Ocean Model, HYCOM use different vertical coordinate systems, and therefore different representations of column physics. Both variants of the GISS climate model are coupled to the same ocean biogeochemistry module (the NASA Ocean Biogeochemistry Model, NOBM which computes prognostic distributions for biotic and abiotic fields that influence the air-sea flux of CO2 and the deep ocean carbon transport and storage. In particular, the model differences due to remineralization rate changes are compared to differences attributed to physical processes modeled differently in the two ocean models such as ventilation, mixing, eddy stirring and vertical advection. The Southern Ocean emerges as a key region where the CO2 flux is as sensitive to biological parameterizations as it is to physical parameterizations. Mixing in the Southern Ocean is shown to be a~good indicator of the magnitude of the biological pump efficiency regardless of physical model choice.

  9. Spatial Variation in the Origin of Dissolved Organic Carbon in Snow on the Juneau Icefield, Southeast Alaska.

    Science.gov (United States)

    Fellman, Jason B; Hood, Eran; Raymond, Peter A; Stubbins, Aron; Spencer, Robert G M

    2015-10-01

    Dissolved organic carbon (DOC) plays a fundamental role in the biogeochemistry of glacier ecosystems. However, the specific sources of glacier DOC remain unresolved. To assess the origin and nature of glacier DOC, we collected snow from 10 locations along a transect across the Juneau Icefield, Alaska extending from the coast toward the interior. The Δ(14)C-DOC of snow varied from -743 to -420‰ showing progressive depletion across the Icefield as δ(18)O of water became more depleted (R(2) = 0.56). Older DOC corresponded to lower DOC concentrations in snow (R(2) = 0.31) and a decrease in percent humic-like fluorescence (R(2) = 0.36), indicating an overall decrease in modern DOC across the Icefield. Carbon isotopic signatures ((13)C and (14)C) combined with a three-source mixing model showed that DOC deposited in snow across the Icefield reflects fossil fuel combustion products (43-73%) and to a lesser extent marine (21-41%) and terrestrial sources (1-26%). Our finding that combustion aerosols are a large source of DOC to the glacier ecosystem during the early spring (April-May) together with the pronounced rates of glacier melting in the region suggests that the delivery of relic DOC to the ocean may be increasing and consequently impacting the biogeochemistry of glacial and proglacial ecosystems in unanticipated ways.

  10. Quantifying Net Carbon Exchanges Between the Atmosphere and Terrestrial Biosphere in the Arctic: What Have We Learned through Decade Regional Modeling Studies?

    Science.gov (United States)

    Zhuang, Q.

    2014-12-01

    Observed Arctic warming has been projected to continue in this century. Permafrost degradation is thus expected to continue, exposing large amounts of carbon for decomposition. Dynamics of Arctic landscape and hydrology are complicated due to changing climate and thawing permafrost, affecting the carbon biogeochemical cycling in the region. Further, human activities together with changing climate transform the regional land use and land cover, including wildfires, logging, and agricultural land conversion. This presentation will review the effects of factors, controls, and processes as well as landscape types (e.g., forests vs. lakes) on carbon biogeochemistry based on regional modeling studies and observations. Specific effects on carbon dynamics to be discussed will include: 1) thawing permafrost; 2) fire disturbances; 2) atmospheric carbon dioxide; 3) inorganic and organic nitrogen uptake by plants; 4) priming; 5) aerobic and anaerobic organic matter decomposition; and 6) various complexities of microbial physiology of soils. Partitioning the contribution of these processes to regional carbon dynamics shall help us improve the terrestrial biogeochemistry models, an important component of Earth System Models that are used to project our future climate.

  11. A 3-D variational assimilation scheme in coupled transport-biogeochemical models: Forecast of Mediterranean biogeochemical properties.

    Science.gov (United States)

    Teruzzi, Anna; Dobricic, Srdjan; Solidoro, Cosimo; Cossarini, Gianpiero

    2014-01-01

    [1] Increasing attention is dedicated to the implementation of suitable marine forecast systems for the estimate of the state of the ocean. Within the framework of the European MyOcean infrastructure, the pre-existing short-term Mediterranean Sea biogeochemistry operational forecast system has been upgraded by assimilating remotely sensed ocean color data in the coupled transport-biogeochemical model OPATM-BFM using a 3-D variational data assimilation (3D-VAR) procedure. In the present work, the 3D-VAR scheme is used to correct the four phytoplankton functional groups included in the OPATM-BFM in the period July 2007 to September 2008. The 3D-VAR scheme decomposes the error covariance matrix using a sequence of different operators that account separately for vertical covariance, horizontal covariance, and covariance among biogeochemical variables. The assimilation solution is found in a reduced dimensional space, and the innovation for the biogeochemical variables is obtained by the sequential application of the covariance operators. Results show a general improvement in the forecast skill, providing a correction of the basin-scale bias of surface chlorophyll concentration and of the local-scale spatial and temporal dynamics of typical bloom events. Further, analysis of the assimilation skill provides insights into the functioning of the model. The computational costs of the assimilation scheme adopted are low compared to other assimilation techniques, and its modular structure facilitates further developments. The 3D-VAR scheme results especially suitable for implementation within a biogeochemistry operational forecast system.

  12. Effect of the redox dynamics on microbial-mediated As transformation coupled with Fe and S in flow-through sediment columns.

    Science.gov (United States)

    Moon, Hee Sun; Kim, Bo-A; Hyun, Sung Pil; Lee, Yoon-Ho; Shin, Doyun

    2017-05-05

    Arsenic (As) biogeochemistry coupled with iron (Fe) and sulfur (S) was studied using columns packed with As(V)-contaminated sediments under two phases: a reduction phase followed by an oxidation phase. During the reduction phase, four identical columns inoculated with G. sulfurreducens were stimulated with 3mM acetate for 60days. The As(III) in the effluent rapidly increased then gradually decreased. The Fe(II) and sulfate concentration indicated ferrous sulfide precipitation inside the column after day 14 and X-ray absorption near edge structure spectra showed that As(III) was enriched at the column outlet. The genera Desulfosporosinus and Anaeromyxobacter as well as the Geobacter inoculum played a primary role in As reduction. During the oxidation phase, dissolved oxygen was consumed by heterotrophic aerobes belonging to the phylum Cloroflexi in the column with acetate, resulting in more As in the effluent. When only nitrate was injected, sulfur-oxidizing bacteria such as Thiobacillus thioparus instantly oxidized the sulfide formed during the first phase, resulting in less As(V) in the aqueous phase compared to the column with dissolved oxygen alone. This study showed that redox gradients and dynamics linked to Fe and S biogeochemistry have an important role in controlling As mobility in subsurface environments.

  13. Copper in the sea: a bibliography

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, R.L.

    1977-04-01

    Life in the sea is vulnerable to the influx of trace metals resulting from man's activities. Although many pollutants introduced to the sea eventually degrade to less harmful forms, trace metals accumulate in sediments and have a continued potential for effect on biota. Copper has a toxic potential exceeding all other metals due to the quantity discharged and its toxicological effect. Fortunately, copper in the oceans is rendered less bioavailable or less toxic by its ready interaction with the complex chemical components of seawater. This bibliography was prepared to illustrate the status of current knowledge of the biogeochemistry of copper and to aid the development of research programs to define the effects of copper discharged to the marine environment. The references are categorized to aid the reader to locate literature concerning specific aspects of the biogeochemistry of copper. A brief comment describing the important findings in each category is given. Although this bibliography is not exhaustive, the listed references are likely representative of current knowledge.

  14. Arctic Ocean shelf biogeochemical cycling under climate change

    Science.gov (United States)

    Bellerby, Richard; Silyakova, Anna; Slagstad, Dag

    2014-05-01

    Changes to Arctic Ocean biogeochemistry will result from a complex array of climate and chemical perturbations over the next decades. Changes to freshwater and nutrient supply through ice melt and continental runoff; warming of the ocean and an increasing ocean acidification through partial equilibrium with a rising anthropogenic CO2 load will change the nature of Arctic Ocean ecological and biogeochemical coupling. This is no more apparent on the shelf regions where there is strong influence from land sources of freshwater and total alkalinity. This presentation will document our combined approach of studying Arctic biogeochemical change through coupled observational, experimental and modelling campaigns. We have identified large changes in recent anthropogenic carbon transport to the Arctic and have characterised the associated regional and water mass ocean acidification. We have determined, through targeted Arctic pelagic ecosystem perturbations experiments, changes to ecosystem structure, succession and biogeochemical cycling under high CO2. Observations have been incorporated into regional, coupled physical-ecosystem-carbon biogeochemical models (informed at the boundaries by downscaled global earth system models) to develop scenarios of change in biogeochemical pathways. We have identified large regional variability in ocean acidification that is shown to impact on shelf biogeochemistry, ecosystems and climate feedbacks in the Arctic Ocean.

  15. Experiments with Seasonal Forecasts of ocean conditions for the Northern region of the California Current upwelling system

    Science.gov (United States)

    Siedlecki, Samantha A.; Kaplan, Isaac C.; Hermann, Albert J.; Nguyen, Thanh Tam; Bond, Nicholas A.; Newton, Jan A.; Williams, Gregory D.; Peterson, William T.; Alin, Simone R.; Feely, Richard A.

    2016-06-01

    Resource managers at the state, federal, and tribal levels make decisions on a weekly to quarterly basis, and fishers operate on a similar timeframe. To determine the potential of a support tool for these efforts, a seasonal forecast system is experimented with here. JISAO’s Seasonal Coastal Ocean Prediction of the Ecosystem (J-SCOPE) features dynamical downscaling of regional ocean conditions in Washington and Oregon waters using a combination of a high-resolution regional model with biogeochemistry and forecasts from NOAA’s Climate Forecast System (CFS). Model performance and predictability were examined for sea surface temperature (SST), bottom temperature, bottom oxygen, pH, and aragonite saturation state through model hindcasts, reforecast, and forecast comparisons with observations. Results indicate J-SCOPE forecasts have measurable skill on seasonal timescales. Experiments suggest that seasonal forecasting of ocean conditions important for fisheries is possible with the right combination of components. Those components include regional predictability on seasonal timescales of the physical environment from a large-scale model, a high-resolution regional model with biogeochemistry that simulates seasonal conditions in hindcasts, a relationship with local stakeholders, and a real-time observational network. Multiple efforts and approaches in different regions would advance knowledge to provide additional tools to fishers and other stakeholders.

  16. Spin-Up and Tuning of the Global Carbon Cycle Model Inside the GISS ModelE2 GCM

    Science.gov (United States)

    Aleinov, Igor; Kiang, Nancy Y.; Romanou, Anastasia

    2015-01-01

    Planetary carbon cycle involves multiple phenomena, acting at variety of temporal and spacial scales. The typical times range from minutes for leaf stomata physiology to centuries for passive soil carbon pools and deep ocean layers. So, finding a satisfactory equilibrium state becomes a challenging and computationally expensive task. Here we present the spin-up processes for different configurations of the GISS Carbon Cycle model from the model forced with MODIS observed Leaf Area Index (LAI) and prescribed ocean to the prognostic LAI and to the model fully coupled to the dynamic ocean and ocean biology. We investigate the time it takes the model to reach the equilibrium and discuss the ways to speed up this process. NASA Goddard Institute for Space Studies General Circulation Model (GISS ModelE2) is currently equipped with all major algorithms necessary for the simulation of the Global Carbon Cycle. The terrestrial part is presented by Ent Terrestrial Biosphere Model (Ent TBM), which includes leaf biophysics, prognostic phenology and soil biogeochemistry module (based on Carnegie-Ames-Stanford model). The ocean part is based on the NASA Ocean Biogeochemistry Model (NOBM). The transport of atmospheric CO2 is performed by the atmospheric part of ModelE2, which employs quadratic upstream algorithm for this purpose.

  17. Atmospheric transport and deposition of mineral dust to the ocean: implications for research needs.

    Science.gov (United States)

    Schulz, Michael; Prospero, Joseph M; Baker, Alex R; Dentener, Frank; Ickes, Luisa; Liss, Peter S; Mahowald, Natalie M; Nickovic, Slobodan; García-Pando, Carlos Pérez; Rodríguez, Sergio; Sarin, Manmohan; Tegen, Ina; Duce, Robert A

    2012-10-01

    This paper reviews our knowledge of the measurement and modeling of mineral dust emissions to the atmosphere, its transport and deposition to the ocean, the release of iron from the dust into seawater, and the possible impact of that nutrient on marine biogeochemistry and climate. Of particular concern is our poor understanding of the mechanisms and quantities of dust deposition as well as the extent of iron solubilization from the dust once it enters the ocean. Model estimates of dust deposition in remote oceanic regions vary by more than a factor of 10. The fraction of the iron in dust that is available for use by marine phytoplankton is still highly uncertain. There is an urgent need for a long-term marine atmospheric surface measurement network, spread across all oceans. Because the southern ocean is characterized by large areas with high nitrate but low chlorophyll surface concentrations, that region is particularly sensitive to the input of dust and iron. Data from this region would be valuable, particularly at sites downwind from known dust source areas in South America, Australia, and South Africa. Coordinated field experiments involving both atmospheric and marine measurements are recommended to address the complex and interlinked processes and role of dust/Fe fertilization on marine biogeochemistry and climate.

  18. Relationships between ocean anoxia, the biological pump, and marine animal life during the Permian-Triassic mass extinction (Invited)

    Science.gov (United States)

    Meyer, K. M.; Schaal, E. K.; Payne, J.

    2013-12-01

    Ocean anoxia/euxinia and carbon cycle instability have long been linked to the end-Permian mass extinction and the Early Triassic interval of delayed or interrupted biotic recovery. Many hypotheses to explain this extinction event invoke the release of greenhouse gases during the emplacement of the Siberian Traps, which likely triggered abrupt changes in marine biogeochemical cycling, atmospheric chemistry, and biodiversity. However, the precise ways in which volcanism and these perturbations are linked and how they governed the tempo and mode of biotic recovery remain poorly understood. Here we highlight new C, Ca, and Sr isotopic data that serve to link volcanic CO2 inputs to changes in marine biogeochemistry and environmental change. We then examine the relationship between ocean biogeochemistry, the biological pump, and marine animal ecosystems during the end-Permian mass extinction and Early Triassic recovery. Finally, we use numerical simulations to probe whether these relationships also explain broad Phanerozoic trends in ocean nutrient status, anoxia, and productivity of marine ecosystems.

  19. δ13C-CH4 in ice core samples

    DEFF Research Database (Denmark)

    Sperlich, Peter

    Ice core records of δ13C-CH4 reflect the variability of CH4 biogeochemistry in response to climate change and show this system is far more complex than expected. The first part of this work is concerned with the development of analytical techniques that allow 1) precise referencing and 2) measure......Ice core records of δ13C-CH4 reflect the variability of CH4 biogeochemistry in response to climate change and show this system is far more complex than expected. The first part of this work is concerned with the development of analytical techniques that allow 1) precise referencing and 2......) measurements of δ13C-CH4 in ice core samples as is required when δ13C-CH4 records that are measured in several laboratories are merged for analysis. Both the referencing and measurement techniques have been compared to further laboratories which proofed the accuracy of the analytical systems. The second part...

  20. Characterization and Phenanthrene Sorption of Natural and Pyrogenic Organic Matter Fractions.

    Science.gov (United States)

    Jin, Jie; Sun, Ke; Wang, Ziying; Yang, Yan; Han, Lanfang; Xing, Baoshan

    2017-03-07

    Pyrogenic humic acid (HA) is released into the environment during the large-scale application of biochar. However, the biogeochemistry of pyrogenic organic matter (PyOM) fractions and their sorption of hydrophobic organic compounds (HOCs) are poorly understood in comparison with natural organic matter (NOM) fractions. HA and humin (HM) fractions isolated from soils and the oxidized biochars were characterized. Sorption of phenanthrene (PHE) by these fractions was also examined. The characterization results demonstrate that pyrogenic HAs are different from natural HAs, with the former having lower atomic H/C ratios, more abundant aromatic C, and higher concentrations of surface carboxylic groups. Compared with the fresh biochars, the Koc of PHE on their oxidized biochars, pyrogenic HA, and HM fractions were undiminished, which is encouraging for the use of biochar in soil remediation. The PyOM fractions exhibited stronger nonlinear sorption than the NOM fractions. In addition, the PyOM fractions had higher sorption capacity than the NOM fractions due to their low polar C content and high aryl C content. The results obtained from this work will shed new light on the impact of the addition of biochar on the biogeochemistry of soil organic matter and on the fate of HOCs in biochar-amended soil.

  1. Microbial and biogeochemical responses to projected future nitrate enrichment in the California upwelling system

    Directory of Open Access Journals (Sweden)

    Katherine Rose Marie Mackey

    2014-11-01

    Full Text Available Coastal California is a dynamic upwelling region where nitrogen (N and iron (Fe can both limit productivity and influence biogeochemistry over different spatial and temporal scales. With global change, the flux of nitrate from upwelling is expected to increase over the next century, potentially driving additional oceanic regions toward Fe limitation. In this study we explored the effect of changes in Fe/N ratio on native phytoplankton from five currently Fe-replete sites near the major California upwelling centers at Bodega Bay and Monterey Bay using nutrient addition incubation experiments. Despite the high nitrate levels (13-30 M in the upwelled water, phytoplankton at three of the five sites showed increased growth when 10 M nitrate was added. None of the sites showed enhanced growth following addition of 10 nM Fe. Nitrate additions favored slow sinking single-celled diatoms over faster sinking chain-forming diatoms, suggesting that future increases in nitrate flux could affect carbon and silicate export and alter grazer populations. In particular, solitary cells of Cylindrotheca were more abundant than the toxin-producing genus Pseudonitzschia following nitrate addition. These responses suggest the biogeochemistry of coastal California could change in response to future increases in nitrate, and multiple stressors like ocean acidification and hypoxia may further result in ecosystem shifts.

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

    Science.gov (United States)

    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.

  3. The Science of Middle Nature

    Science.gov (United States)

    Pataki, D. E.; Pincetl, S.

    2012-12-01

    In the field of biogeochemistry, urbanization is often considered as an "alteration" or "disturbance" to the earth's surface and its natural processes. This view is an outcome of the view of nature inherent in earth system science and ecology, in which nature is defined as separate from humans and society. However, other disciplines are based in alternative views of nature in which humans are more integral components of the landscape. Urban planning, landscape architecture, agriculture, and horticulture, for example, more fully integrate the role of landscape design and management in the functioning of human-dominated ecosystems. We suggest that the field of urban biogeochemistry has been somewhat limited by the predominant, disturbance-based view of the role of nature in cities, and that more deeply evaluating and broadening the concept of nature inherent in studies of urban processes can enhance our understanding of the role of urbanization in the earth system. A particularly useful concept is the "middle nature" proposed by Cosgrove (1993), which serves a purpose of "actively transforming nature into culture." It is this view of urban landscapes as middle nature, or transformation of urban space into human-dominated nature with a purpose, that is lacking from the current scientific discourse about the role of biogeochemistry in urban ecosystem services. A scientific evaluation of middle nature implies studying the performance of urban designs to meet intended cultural and environmental goals, including beauty, social equity, governance, and social capital as well as environmental quality. We describe our work in evaluating the transformed urban landscapes of Los Angeles from multiple perspectives that focus on urban livability, equity, and beauty as well as the physical impacts of plants and soils on the environment. The outcomes of this process do not necessary meet the traditional demands of biophysical ecology such as utilizing native species, maximizing

  4. The Science of Middle Nature (Invited)

    Science.gov (United States)

    Pataki, D. E.; Pincetl, S.; Hinners, S.

    2013-12-01

    In the field of biogeochemistry, urbanization is often considered as an 'alteration' or 'disturbance' to the earth's surface and its natural processes. This view is an outcome of the view of nature inherent in earth system science and ecology, in which nature is defined as separate from humans and society. However, other disciplines are based in alternative views of nature in which humans are more integral components of the landscape. Urban planning, landscape architecture, agriculture, and horticulture, for example, more fully integrate the role of landscape design and management in the functioning of human-dominated ecosystems. We suggest that the field of urban biogeochemistry has been somewhat limited by the predominant, disturbance-based view of the role of nature in cities, and that more deeply evaluating and broadening the concept of nature inherent in studies of urban processes can enhance our understanding of the role of urbanization in the earth system. A particularly useful concept is the 'middle nature' proposed by Cosgrove (1993), which serves a purpose of 'actively transforming nature into culture.' It is this view of urban landscapes as middle nature, or transformation of urban space into human-dominated nature with a purpose, that is lacking from the current scientific discourse about the role of biogeochemistry in urban ecosystem services. A scientific evaluation of middle nature implies studying the performance of urban designs to meet intended cultural and environmental goals, including beauty, social equity, governance, and social capital as well as environmental quality. We describe our work in evaluating the transformed urban landscapes of Los Angeles and Salt Lake City from multiple perspectives that focus on urban livability, equity, and beauty as well as the physical impacts of plants and soils on the environment. The outcomes of this process do not necessary meet the traditional demands of biophysical ecology such as utilizing native

  5. Plant functional type mapping for earth system models

    Directory of Open Access Journals (Sweden)

    B. Poulter

    2011-11-01

    Full Text Available The sensitivity of global carbon and water cycling to climate variability is coupled directly to land cover and the distribution of vegetation. To investigate biogeochemistry-climate interactions, earth system models require a representation of vegetation distributions that are either prescribed from remote sensing data or simulated via biogeography models. However, the abstraction of earth system state variables in models means that data products derived from remote sensing need to be post-processed for model-data assimilation. Dynamic global vegetation models (DGVM rely on the concept of plant functional types (PFT to group shared traits of thousands of plant species into usually only 10–20 classes. Available databases of observed PFT distributions must be relevant to existing satellite sensors and their derived products, and to the present day distribution of managed lands. Here, we develop four PFT datasets based on land-cover information from three satellite sensors (EOS-MODIS 1 km and 0.5 km, SPOT4-VEGETATION 1 km, and ENVISAT-MERIS 0.3 km spatial resolution that are merged with spatially-consistent Köppen-Geiger climate zones. Using a beta (ß diversity metric to assess reclassification similarity, we find that the greatest uncertainty in PFT classifications occur most frequently between cropland and grassland categories, and in dryland systems between shrubland, grassland and forest categories because of differences in the minimum threshold required for forest cover. The biogeography-biogeochemistry DGVM, LPJmL, is used in diagnostic mode with the four PFT datasets prescribed to quantify the effect of land-cover uncertainty on climatic sensitivity of gross primary productivity (GPP and transpiration fluxes. Our results show that land-cover uncertainty has large effects in arid regions, contributing up to 30% (20% uncertainty in the sensitivity of GPP (transpiration to precipitation. The availability of PFT datasets that are consistent

  6. Plant functional type mapping for earth system models

    Directory of Open Access Journals (Sweden)

    B. Poulter

    2011-08-01

    Full Text Available The sensitivity of global carbon and water cycling to climate variability is coupled directly to land cover and the distribution of vegetation. To investigate biogeochemistry-climate interactions, earth system models require a representation of vegetation distributions that are either prescribed from remote sensing data or simulated via biogeography models. However, the abstraction of earth system state variables in models means that data products derived from remote sensing need to be post-processed for model-data assimilation. Dynamic global vegetation models (DGVM rely on the concept of plant functional types (PFT to group shared traits of thousands of plant species into just several classes. Available databases of observed PFT distributions must be relevant to existing satellite sensors and their derived products, and to the present day distribution of managed lands. Here, we develop four PFT datasets based on land-cover information from three satellite sensors (EOS-MODIS 1 km and 0.5 km, SPOT4-VEGETATION 1 km, and ENVISAT-MERIS 0.3 km spatial resolution that are merged with spatially-consistent Köppen-Geiger climate zones. Using a beta (β diversity metric to assess reclassification similarity, we find that the greatest uncertainty in PFT classifications occur most frequently between cropland and grassland categories, and in dryland systems between shrubland, grassland and forest categories because of differences in the minimum threshold required for forest cover. The biogeography-biogeochemistry DGVM, LPJmL, is used in diagnostic mode with the four PFT datasets prescribed to quantify the effect of land-cover uncertainty on climatic sensitivity of gross primary productivity (GPP and transpiration fluxes. Our results show that land-cover uncertainty has large effects in arid regions, contributing up to 30 % (20 % uncertainty in the sensitivity of GPP (transpiration to precipitation. The availability of plant functional type datasets that

  7. CLM4-BeTR, a generic biogeochemical transport and reaction module for CLM4: model development, evaluation, and application

    Directory of Open Access Journals (Sweden)

    J. Y. Tang

    2013-01-01

    Full Text Available To improve regional and global biogeochemistry modeling and climate predictability, we have developed a generic reactive transport module for the land model CLM4 (called CLM4-BeTR (Biogeochemical Transport and Reactions. CLM4-BeTR represents the transport, interactions, and biotic and abiotic transformations of an arbitrary number of tracers (aka chemical species in an arbitrary number of phases (e.g., dissolved, gaseous, sorbed, aggregate. An operator splitting approach was employed and consistent boundary conditions were derived for each modeled sub-process. Aqueous tracer fluxes, associated with hydrological processes such as surface run-on and run-off, belowground drainage, and ice to liquid conversion were also computed consistently with the bulk water fluxes calculated by the soil physics module in CLM4. The transport code was evaluated and found in good agreement with several analytical test cases using a time step of 30 min. The model was then applied at the Harvard Forest site with a representation of depth-dependent belowground biogeochemistry. The results indicated that, at this site, (1 CLM4-BeTR was able to simulate soil–surface CO2 effluxes and soil CO2 profiles accurately; (2 the transient surface CO2 effluxes calculated based on the tracer transport mechanism were in general not equal to the belowground CO2 production rates with the magnitude of the difference being a function of averaging timescale and site conditions: differences were large (−20 ~ 20% on hourly, smaller (−5 ~ 5% at daily timescales, and persisted to the monthly timescales with a smaller magnitude (<4%; (3 losses of CO2 through processes other than surface gas efflux were less than 1% of the overall soil respiration; and (4 the contributions of root respiration and heterotrophic respiration have distinct temporal signals in surface CO2 effluxes and soil CO2 concentrations. The

  8. Circumpolar distribution and carbon storage of thermokarst landscapes.

    Science.gov (United States)

    Olefeldt, D; Goswami, S; Grosse, G; Hayes, D; Hugelius, G; Kuhry, P; McGuire, A D; Romanovsky, V E; Sannel, A B K; Schuur, E A G; Turetsky, M R

    2016-10-11

    Thermokarst is the process whereby the thawing of ice-rich permafrost ground causes land subsidence, resulting in development of distinctive landforms. Accelerated thermokarst due to climate change will damage infrastructure, but also impact hydrology, ecology and biogeochemistry. Here, we present a circumpolar assessment of the distribution of thermokarst landscapes, defined as landscapes comprised of current thermokarst landforms and areas susceptible to future thermokarst development. At 3.6 × 10(6) km(2), thermokarst landscapes are estimated to cover ∼20% of the northern permafrost region, with approximately equal contributions from three landscape types where characteristic wetland, lake and hillslope thermokarst landforms occur. We estimate that approximately half of the below-ground organic carbon within the study region is stored in thermokarst landscapes. Our results highlight the importance of explicitly considering thermokarst when assessing impacts of climate change, including future landscape greenhouse gas emissions, and provide a means for assessing such impacts at the circumpolar scale.

  9. On dealing with the pollution costs in agriculture: A case study of paddy fields.

    Science.gov (United States)

    Yaqubi, Morteza; Shahraki, Javad; Sabouhi Sabouni, Mahmood

    2016-06-15

    The main purpose of this study is to evaluate marginal abatement cost of the main agricultural pollutants. In this sense, we construct three indices including Net Global Warming Potential (NGWP) and Nitrogen Surplus (NS), simulated by a biogeochemistry model, and also an Environmental Impact Quotient (EQI) for paddy fields. Then, using a Data Envelopment Analysis (DEA) model, we evaluate environmental inefficiencies and shadow values of these indices. The results show that there is still room for improvement at no extra cost just through a better input management. Besides, enormous potential for pollution reduction in the region is feasible. Moreover, in paddy cultivation, marginal abatement cost of pesticides and herbicides are much bigger than nitrogen surplus and greenhouse gasses. In addition, in the status quo, the mitigation costs are irrelevant to production decisions. Finally, to deal with the private pollution costs, market-based instruments are proved to be better than command-and-control regulation.

  10. Environmental effects of ozone depletion and its interactions with climate change: progress report, 2015.

    Science.gov (United States)

    2016-02-01

    The Environmental Effects Assessment Panel (EEAP) is one of three Panels that regularly informs the Parties (countries) to the Montreal Protocol on the effects of ozone depletion and the consequences of climate change interactions with respect to human health, animals, plants, biogeochemistry, air quality, and materials. The Panels provide a detailed assessment report every four years. The most recent 2014 Quadrennial Assessment by the EEAP was published as a special issue of seven papers in 2015 (Photochem. Photobiol. Sci., 2015, 14, 1-184). The next Quadrennial Assessment will be published in 2018/2019. In the interim, the EEAP generally produces an annual update or progress report of the relevant scientific findings. The present progress report for 2015 assesses some of the highlights and new insights with regard to the interactive nature of the effects of UV radiation, atmospheric processes, and climate change.

  11. Use of Flow Cytometry to Measure Biogeochemical Rates and Processes in the Ocean

    Science.gov (United States)

    Lomas, Michael W.; Bronk, Deborah A.; van den Engh, Ger

    2011-01-01

    An important goal of marine biogeochemists is to quantify the rates at which elements cycle through the ocean's diverse microbial assemblage, as well as to determine how these rates vary in time and space. The traditional view that phytoplankton are producers and bacteria are consumers has been found to be overly simplistic, and environmental metagenomics is discovering new and important microbial metabolisms at an accelerating rate. Many nutritional strategies previously attributed to one microorganism or functional group are also or instead carried out by other groups. To tease apart which organism is doing what will require new analytical approaches. Flow cytometry, when combined with other techniques, has great potential for expanding our understanding of microbial interactions because groups can be distinguished optically, sorted, and then collected for subsequent analyses. Herein, we review the advances in our understanding of marine biogeochemistry that have arisen from the use of flow cytometry.

  12. Direct determination of thickness of sea surface microlayer using a pH microelectrode at original location

    Institute of Scientific and Technical Information of China (English)

    张正斌; 蔡卫君; 刘莲生; 刘春颖; 陈飞舟

    2003-01-01

    By using a pH microelectrode and ultramicro-vernier shift equipment,a new method to determine directly the thickness of the sea surface microlayer (SML) at original location, is advanced and founded, which is an important innovation on the SML sampling method and the SML research. Applying the intersecting straight line method, the SML thickness was found to be approximately 60 μm. This result is consistent not only with the measurement result, (50±10) μm, obtained with the conventional glass plate method, but also with the sudden change layer of physical and chemical properties of seawater, and with the results reported in the literature. The determination method will have the ocean biogeochemistry significance on marine chemistry.

  13. Paleoclimate. Enhanced tropical methane production in response to iceberg discharge in the North Atlantic.

    Science.gov (United States)

    Rhodes, Rachael H; Brook, Edward J; Chiang, John C H; Blunier, Thomas; Maselli, Olivia J; McConnell, Joseph R; Romanini, Daniele; Severinghaus, Jeffrey P

    2015-05-29

    The causal mechanisms responsible for the abrupt climate changes of the Last Glacial Period remain unclear. One major difficulty is dating ice-rafted debris deposits associated with Heinrich events: Extensive iceberg influxes into the North Atlantic Ocean linked to global impacts on climate and biogeochemistry. In a new ice core record of atmospheric methane with ultrahigh temporal resolution, we find abrupt methane increases within Heinrich stadials 1, 2, 4, and 5 that, uniquely, have no counterparts in Greenland temperature proxies. Using a heuristic model of tropical rainfall distribution, we propose that Hudson Strait Heinrich events caused rainfall intensification over Southern Hemisphere land areas, thereby producing excess methane in tropical wetlands. Our findings suggest that the climatic impacts of Heinrich events persisted for 740 to 1520 years.

  14. Southern Ocean biological impacts on global ocean oxygen

    Science.gov (United States)

    Keller, David P.; Kriest, Iris; Koeve, Wolfgang; Oschlies, Andreas

    2016-06-01

    Southern Ocean (SO) physical and biological processes are known to have a large impact on global biogeochemistry. However, the role that SO biology plays in determining ocean oxygen concentrations is not completely understood. These dynamics are investigated here by shutting off SO biology in two marine biogeochemical models. The results suggest that SO biological processes reduce the ocean's oxygen content, mainly in the deep ocean, by 14 to 19%. However, since these processes also trap nutrients that would otherwise be transported northward to fuel productivity and subsequent organic matter export, consumption, and the accompanying oxygen consumption in midlatitude to low-latitude waters, SO biology helps to maintain higher oxygen concentrations in these subsurface waters. Thereby, SO biology can influence the size of the tropical oxygen minimum zones. As a result of ocean circulation the link between SO biological processes and remote oxygen changes operates on decadal to centennial time scales.

  15. High export of dissolved silica from the Greenland Ice Sheet

    Science.gov (United States)

    Meire, L.; Meire, P.; Struyf, E.; Krawczyk, D. W.; Arendt, K. E.; Yde, J. C.; Juul Pedersen, T.; Hopwood, M. J.; Rysgaard, S.; Meysman, F. J. R.

    2016-09-01

    Silica is an essential element for marine life and plays a key role in the biogeochemistry of the ocean. Glacial activity stimulates rock weathering, generating dissolved silica that is exported to coastal areas along with meltwater. The magnitude of the dissolved silica export from large glacial areas such as the Greenland Ice Sheet is presently poorly quantified and not accounted for in global budgets. Here we present data from two fjord systems adjacent to the Greenland Ice Sheet which reveal a large export of dissolved silica by glacial meltwater relative to other macronutrients. Upscaled to the entire Greenland Ice Sheet, the export of dissolved silica equals 22 ± 10 Gmol Si yr-1. When the silicate-rich meltwater mixes with upwelled deep water, either inside or outside Greenland's fjords, primary production takes place at increased silicate to nitrate ratios. This likely stimulates the growth of diatoms relative to other phytoplankton groups.

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

    DEFF Research Database (Denmark)

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

    2015-01-01

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

  17. Cadmium contamination of agricultural soils and crops resulting from sphalerite weathering.

    Science.gov (United States)

    Robson, T C; Braungardt, C B; Rieuwerts, J; Worsfold, P

    2014-01-01

    The biogeochemistry and bioavailability of cadmium, released during sphalerite weathering in soils, were investigated under contrasting agricultural scenarios to assess health risks associated with sphalerite dust transport to productive soils from mining. Laboratory experiments (365 d) on temperate and sub-tropical soils amended with sphalerite (soil accumulated ≈38% (29 μmol kg(-1)) of the liberated Cd, exceeding food safety limits. In contrast, rice grown in flooded sub-tropical soil accumulated far less Cd (0.60 μmol kg(-1)) due to neutral soil pH and Cd bioavailability was possibly also controlled by secondary sulfide formation. The results demonstrate long-term release of Cd to soil porewaters during sphalerite weathering. Under oxic conditions, Cd may be sufficiently bioavailable to contaminate crops destined for human consumption; however flooded rice production limits the impact of sphalerite contamination.

  18. Incidence of lesions on Fungiidae corals in the eastern Red Sea is related to water temperature and coastal pollution

    KAUST Repository

    Furby, K.A.

    2014-07-01

    As sea surface temperatures rise and the global human population increases, large-scale field observations of marine organism health and water quality are increasingly necessary. We investigated the health of corals from the family Fungiidae using visual observations in relation to water quality and microbial biogeochemistry parameters along 1300 km of the Red Sea coast of Saudi Arabia. At large scales, incidence of lesions caused by unidentified etiology showed consistent signs, increasing significantly from the northern to southern coast and positively correlated to annual mean seawater temperatures. Lesion abundance also increased to a maximum of 96% near the populous city of Jeddah. The presence of lesioned corals in the region surrounding Jeddah was strongly correlated with elevated concentrations of ammonium and changes in microbial communities that are linked to decreased water quality. This study suggests that both high seawater temperatures and nutrient pollution may play an indirect role in the formation of lesions on corals. © 2014 Elsevier Ltd.

  19. Extracellular Electron Transport Coupling Biogeochemical Processes Centimeters

    DEFF Research Database (Denmark)

    Risgaard-Petersen, Nils; Fossing, Henrik; Christensen, Peter Bondo;

    2010-01-01

    Recent observations in marine sediment have revealed  conductive networks transmitting electrons from oxidation processes in the anoxic zone to oxygen reduction in the oxiczone [1]. The electrochemical processes and conductors seem to be biologically controlled and may account for more than half...... confirmed the depth range of the electric communication and indicated donation of electrons directly from organotrophic bacteria. The separation of oxidation and reduction processes created steep pH gradients eventually causing carbonate precipitation at the surface. The results indicate that electron...... of the oxygen uptake in laboratory incubations of initially homogenized and stabilized sediment. Using microsensors and process rate measurements we further investigated the effect of the electric currents on sediment biogeochemistry. Dissolved sulfide readily donated electrons to the networks and could...

  20. Electric currents couple spatially separated biogeochemical processes in marine sediment

    DEFF Research Database (Denmark)

    Nielsen, Lars Peter; Risgaard-Petersen, Nils; Fossing, Henrik;

    2010-01-01

    be coupled by electric currents in nature. Here we provide evidence that electric currents running through defaunated sediment couple oxygen consumption at the sediment surface to oxidation of hydrogen sulphide and organic carbon deep within the sediment. Altering the oxygen concentration in the sea water...... in the sediment was driven by electrons conducted from the anoxic zone. A distinct pH peak in the oxic zone could be explained by electrochemical oxygen reduction, but not by any conventional sets of aerobic sediment processes. We suggest that the electric current was conducted by bacterial nanowires combined...... with pyrite, soluble electron shuttles and outer-membrane cytochromes. Electrical communication between distant chemical and biological processes in nature adds a new dimension to our understanding of biogeochemistry and microbial ecology....

  1. Chemical characterisation of african dust transported to Canary Region

    Science.gov (United States)

    Gelado, M. D.; López, P.; Prieto, S.; Collado, C.; Hernández, J. J.

    2009-04-01

    African dust pulses have important effects on the climate conditions and the marine biogeochemistry in the Canary Region. Aerosol samples have been collected at three stations on Gran Canaria Island (Taliarte at sea level, Tafira 269 m a.s.l. and Pico de la Gorra 1930 m a.s.l.) during 2000-2008. Elemental characterisation of the collected mineral aerosol and back trajectories of the air masses are used to distinguish regional African sources of dust. Dust aerosol samples from North Sahara (Morocco, North Algeria and Tunisia), West and Central Sahara (20°-30°N, 18°W-50°E) and Sahel (0°-20°N, 18°W-50°E) have shown different Ca/Ti, Al/Ti and Fe/Al ratios. Ti appears as a better tracer element of specific source of dust than Fe, probably due to a less mineral alteration during the atmospheric transport.

  2. New AGU Mass Media Fellow Initiated College Science Communication Course

    Science.gov (United States)

    Weiss, Peter

    2010-10-01

    Marissa Weiss, this year's AGU Mass Media Fellow, feels so strongly about communicating science that she and a fellow graduate student started a course on the subject. Three years ago, she and the other student in the biogeochemistry and environmental biocomplexity program at Cornell University, Ithaca, N. Y., developed—with the aid of mentors—a semester­long science communication class. The course has since become a regular offering at Cornell, where Weiss defended her dissertation in ecology this past August. A soil ecologist, Weiss showed in her thesis research that nitrogen pollution can cause slowing of soil decomposition because of a declining abundance of microbes that break the soil down.

  3. Genomic Encyclopedia of Bacterial and Archaeal Type Strains, Phase III: the genomes of soil and plant-associated and newly described type strains.

    Science.gov (United States)

    Whitman, William B; Woyke, Tanja; Klenk, Hans-Peter; Zhou, Yuguang; Lilburn, Timothy G; Beck, Brian J; De Vos, Paul; Vandamme, Peter; Eisen, Jonathan A; Garrity, George; Hugenholtz, Philip; Kyrpides, Nikos C

    2015-01-01

    The Genomic Encyclopedia of Bacteria and Archaea (GEBA) project was launched by the JGI in 2007 as a pilot project to sequence about 250 bacterial and archaeal genomes of elevated phylogenetic diversity. Herein, we propose to extend this approach to type strains of prokaryotes associated with soil or plants and their close relatives as well as type strains from newly described species. Understanding the microbiology of soil and plants is critical to many DOE mission areas, such as biofuel production from biomass, biogeochemistry, and carbon cycling. We are also targeting type strains of novel species while they are being described. Since 2006, about 630 new species have been described per year, many of which are closely aligned to DOE areas of interest in soil, agriculture, degradation of pollutants, biofuel production, biogeochemical transformation, and biodiversity.

  4. Hydrocarbon biodegradation in intertidal wetland sediments.

    Science.gov (United States)

    McGenity, Terry J

    2014-06-01

    Intertidal wetlands, primarily salt marsh, mangrove and mudflats, which provide many essential ecosystem services, are under threat on numerous fronts; a situation that is made worse by crude-oil pollution. Microbes are the main vehicle for remediation of such sediments, and new discoveries, such as novel biodegradation pathways, means of accessing oil, multi-species interactions, and community-level responses to oil addition, are helping us to understand, predict and monitor the fate of oil. Despite this, there are many challenges, not least because of the heterogeneity of these ecosystems and the complexity of crude oil. For example, there is growing awareness about the toxicity of the oxygenated products that result from crude-oil weathering, which are difficult to degrade. This review highlights how developments in areas as diverse as systems biology, microbiology, ecology, biogeochemistry and analytical chemistry are enhancing our understanding of hydrocarbon biodegradation and thus bioremediation of oil-polluted intertidal wetlands.

  5. Indirect emissions from biofuels: how important?

    Science.gov (United States)

    Melillo, Jerry M; Reilly, John M; Kicklighter, David W; Gurgel, Angelo C; Cronin, Timothy W; Paltsev, Sergey; Felzer, Benjamin S; Wang, Xiaodong; Sokolov, Andrei P; Schlosser, C Adam

    2009-12-04

    A global biofuels program will lead to intense pressures on land supply and can increase greenhouse gas emissions from land-use changes. Using linked economic and terrestrial biogeochemistry models, we examined direct and indirect effects of possible land-use changes from an expanded global cellulosic bioenergy program on greenhouse gas emissions over the 21st century. Our model predicts that indirect land use will be responsible for substantially more carbon loss (up to twice as much) than direct land use; however, because of predicted increases in fertilizer use, nitrous oxide emissions will be more important than carbon losses themselves in terms of warming potential. A global greenhouse gas emissions policy that protects forests and encourages best practices for nitrogen fertilizer use can dramatically reduce emissions associated with biofuels production.

  6. Distribution and Changes of Specification of Phosphorus in the Yellow Sea

    Institute of Scientific and Technical Information of China (English)

    Chen Hongtao; Chen Shuzhu; Zhang Jing; Liu Sumei; Wu Qiangming

    2002-01-01

    The studies on the distribution and varatiation of the specification of phosphorus in the southern part of the Yellow Sea are made. The biogeochemistry of phosphorus in the Yellow Sea is discussed. The phosphorus is slightly higher in the bottom than in the surface waters in the southern part of the Yellow Sea and the dissolved organic phosphorus is the main form. The transfer patterns between various forms of particulate and dissolved phosphorus are different in the bottom and surface, probably due to the contribution of dissolved organic phosphorus. The distributions of dissolved inorganic phosphorus and dissolved organic phosphorus are mainly affected by the biological processes and could act as a prediction factor for the red tide. The supply of N and P in most of the areas in the southern part of the Yellow Sea is sufficient, without apparent limitation of N or P.

  7. Dendritic network models: Improving isoscapes and quantifying influence of landscape and in-stream processes on strontium isotopes in rivers

    Science.gov (United States)

    Brennan, Sean R.; Torgersen, Christian E.; Hollenbeck, Jeff P.; Fernandez, Diego P.; Jensen, Carrie K.; Schindler, Daniel E.

    2016-05-01

    A critical challenge for the Earth sciences is to trace the transport and flux of matter within and among aquatic, terrestrial, and atmospheric systems. Robust descriptions of isotopic patterns across space and time, called "isoscapes," form the basis of a rapidly growing and wide-ranging body of research aimed at quantifying connectivity within and among Earth's systems. However, isoscapes of rivers have been limited by conventional Euclidean approaches in geostatistics and the lack of a quantitative framework to apportion the influence of processes driven by landscape features versus in-stream phenomena. Here we demonstrate how dendritic network models substantially improve the accuracy of isoscapes of strontium isotopes and partition the influence of hydrologic transport versus local geologic features on strontium isotope ratios in a large Alaska river. This work illustrates the analytical power of dendritic network models for the field of isotope biogeochemistry, particularly for provenance studies of modern and ancient animals.

  8. Integration of Earth System Models and Workflow Management under iRODS for the Northeast Regional Earth System Modeling Project

    Science.gov (United States)

    Lengyel, F.; Yang, P.; Rosenzweig, B.; Vorosmarty, C. J.

    2012-12-01

    The Northeast Regional Earth System Model (NE-RESM, NSF Award #1049181) integrates weather research and forecasting models, terrestrial and aquatic ecosystem models, a water balance/transport model, and mesoscale and energy systems input-out economic models developed by interdisciplinary research team from academia and government with expertise in physics, biogeochemistry, engineering, energy, economics, and policy. NE-RESM is intended to forecast the implications of planning decisions on the region's environment, ecosystem services, energy systems and economy through the 21st century. Integration of model components and the development of cyberinfrastructure for interacting with the system is facilitated with the integrated Rule Oriented Data System (iRODS), a distributed data grid that provides archival storage with metadata facilities and a rule-based workflow engine for automating and auditing scientific workflows.

  9. Enhanced tropical methane production in response to iceberg discharge in the North Atlantic

    Science.gov (United States)

    Rhodes, Rachael H.; Brook, Edward J.; Chiang, John C. H.; Blunier, Thomas; Maselli, Olivia J.; McConnell, Joseph R.; Romanini, Daniele; Severinghaus, Jeffrey P.

    2015-05-01

    The causal mechanisms responsible for the abrupt climate changes of the Last Glacial Period remain unclear. One major difficulty is dating ice-rafted debris deposits associated with Heinrich events: Extensive iceberg influxes into the North Atlantic Ocean linked to global impacts on climate and biogeochemistry. In a new ice core record of atmospheric methane with ultrahigh temporal resolution, we find abrupt methane increases within Heinrich stadials 1, 2, 4, and 5 that, uniquely, have no counterparts in Greenland temperature proxies. Using a heuristic model of tropical rainfall distribution, we propose that Hudson Strait Heinrich events caused rainfall intensification over Southern Hemisphere land areas, thereby producing excess methane in tropical wetlands. Our findings suggest that the climatic impacts of Heinrich events persisted for 740 to 1520 years.

  10. Bridging the gap between marine biogeochemical and fisheries sciences; configuring the zooplankton link

    DEFF Research Database (Denmark)

    Mitra, Aditee; Castellani, Claudia; Gentleman, Wendy

    2014-01-01

    phytoplankton- dominated biogeochemistry or on aspects of fisheries regulation. In consequence the roles of zooplankton communities (protists and metazoans) linking phytoplankton and fish communities are typically under-represented if not (especially in fisheries models) ignored. Where represented in ecosystem...... models, zooplankton are usually incorporated in an extremely simplistic fashion, using empirical descriptions merging various interacting physiological functions governing zooplankton growth and development, and thence ignoring physiological feedback mechanisms. Here we demonstrate, within a modelled...... plankton food-web system, how trophic dynamics are sensitive to small changes in parameter values describing zooplankton vital rates and thus the importance of using appropriate zooplankton descriptors. Through a comprehensive review, we reveal the mismatch between empirical understanding and modelling...

  11. Groundwater interactions with Lobelia lakes- effects on the aquatic plant, Littorella uniflora

    DEFF Research Database (Denmark)

    Ommen, Daniela Oliveira; Vinther, Hanne Fogh; Krüger, Laila

    aquatic plants whose leaves grow in a rosette form and have a large root base. The large root system enables the plants to better assimilate nutrients from the sediments, and the uptake of CO2 which is used for photosynthesis, and to release O2 into otherwise anoxic sediments. Lake Hampen is situated high....... The macrophytes themselves can also affect the biogeochemistry by changing the concentration of the dissolved CO2, O2 and nutrients in the sediment. The main objective of this project is to investigate how plant growth in Lobelia lakes is influenced by the inlet and outlet of groundwater; and which role...... the plants have in the cycling of the nutrients in these lakes. To fulfil these objectives several smaller studies are to be carried out, these include the determination of the groundwater flow pattern, the determination of the Littorella uniflora coverage within the lake and to establish how this coverage...

  12. Mercury methylation by a microbial community from sediments of the Adour Estuary (Bay of Biscay, France)

    Energy Technology Data Exchange (ETDEWEB)

    Duran, R. [Equipe Environnement et Microbiologie, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, Avenue de l' Universite, IBEAS BP1155, 64013 Pau Cedex (France)], E-mail: robert.duran@univ-pau.fr; Ranchou-Peyruse, M.; Menuet, V. [Equipe Environnement et Microbiologie, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, Avenue de l' Universite, IBEAS BP1155, 64013 Pau Cedex (France); Monperrus, M.; Bareille, G. [Equipe Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, 64013 Pau Cedex (France); Goni, M.S.; Salvado, J.C. [Equipe Environnement et Microbiologie, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, Avenue de l' Universite, IBEAS BP1155, 64013 Pau Cedex (France); Amouroux, D. [Equipe Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, 64013 Pau Cedex (France); Guyoneaud, R. [Equipe Environnement et Microbiologie, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, Avenue de l' Universite, IBEAS BP1155, 64013 Pau Cedex (France); Donard, O.F.X. [Equipe Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR CNRS 5254, Universite de Pau et des Pays de l' Adour, 64013 Pau Cedex (France)] (and others)

    2008-12-15

    In order to study the influence of microorganisms on the mercury biogeochemistry, the metal content and the structure of microbial communities were determined in sediments from stations along the Adour Estuary. The comparison of the bacterial communities and their distribution in function of the environmental parameters by Canonical Correspondence Analysis (CCA) revealed the influence of metals on the bacterial communities structure. Sediments where the bacterial communities are mostly influenced by methylmercury were incubated in slurries with or without mercury, under oxic and anoxic conditions. Methylmercury production was detected in the anoxic biotic slurries with a net methylation yield of 0.3% after 24 h. CCA based on T-RFLP profiles revealed the impact of mercury addition on the bacterial communities structure. In addition, 17 bacterial strains, mainly sulphate-reducing bacteria involved in mercury methylation, were isolated and identified. - Role of oxic/anoxic cycles and microbial activities on the methylmercury formation in Adour (France) estuarine sediments.

  13. Cultivation of Hard-To-Culture Subsurface Mercury-Resistant Bacteria and Discovery of New merA Gene Sequences

    DEFF Research Database (Denmark)

    Rasmussen, Lasse Dam; Zawadsky, C.; Binnerup, Svend Jørgen

    2008-01-01

    Mercur