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  • 1
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    Biogeographical controls on the marine nitrogen fixers (2011)
    Wiley
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    Publication Date: 2011-04-21
    Description: We interpret the environmental controls on the global ocean diazotroph biogeography in the context of a three-dimensional global model with a self-organizing phytoplankton community. As is observed, the model's total diazotroph population is distributed over most of the oligotrophic warm subtropical and tropical waters, with the exception of the southeastern Pacific Ocean. This biogeography broadly follows temperature and light constraints which are often used in both field-based and model studies to explain the distribution of diazotrophs. However, the model suggests that diazotroph habitat is not directly controlled by temperature and light, but is restricted to the ocean regions with low fixed nitrogen and sufficient dissolved iron and phosphate concentrations. We interpret this regulation by iron and phosphate using resource competition theory which provides an excellent qualitative and quantitative framework.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Changes in the Arctic Ocean CO2 sink (1996{2007) : A regional model analysisARCTIC CO2 SINK (2013)
    Wiley
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    Publication Date: 2013-10-16
    Description: ABSTRACT [1]  The rapid recent decline of Arctic Ocean sea ice area increases the flux of solar radiation available for primary production and the area of open water for air-sea gas exchange. We use a regional physical-biogeochemical model of the Arctic Ocean, forced by the NCEP/NCAR atmospheric reanalysis to evaluate the mean present-day CO 2 sink and its temporal evolution. During the 1996–2007 period, the model suggests that the Arctic average sea surface temperature warmed by 0.04°C a −1 , that sea ice area decreased by ~0.1 x 10 6 km 2 a −1 , and that the biological drawdown of dissolved inorganic carbon increased. The simulated 1996–2007 time-mean Arctic Ocean CO 2 sink is 58 ± 6 Tg C a −1 . The increase in ice-free ocean area and consequent carbon drawdown during this period enhances the CO 2 sink by ~1.4 Tg C a −1 , consistent with estimates based on extrapolations of sparse data. A regional analysis suggests that, during the 1996–2007 period, the shelf regions of the Laptev, East Siberian, Chukchi, and Beaufort Seas experienced an increase in the efficiency of their biological pump due to decreased sea ice area, especially during the 2004–2007 period, consistent with independently published estimates of primary production. In contrast, the CO 2 sink in the Barents Sea is reduced during the 2004–2007 period due to a dominant control by warming and decreasing solubility. Thus the effect of decreasing sea-ice area and increasing sea surface temperature partially cancel, though the former is dominant.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    On nitrogen fixation and preferential remineralization of phosphorus (2012)
    Wiley
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    Publication Date: 2012-03-30
    Description: Regional and global nitrogen fixation rates are often estimated from geochemical tracers related to N* (= NO3− − 16PO43−). However the patterns of this tracer reflect the influence of numerous processes including nitrogen fixation, denitrification, remineralization of organic matter, variable stoichiometry, atmospheric deposition and physical transport. Here we have used idealized models to illustrate how preferential remineralization of organic phosphorous may explain observed features of N* distribution in the North Atlantic Ocean, including a subsurface maximum and an increased temporal variability in the mid-thermocline. If preferential remineralization of phosphorus is key in shaping the oceanic distribution of N*, published estimates of nitrogen fixation may be underestimating the marine nitrogen fixation rate by as much as a factor of three.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    A model of the Arctic Ocean carbon cycle (2011)
    Wiley
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    Publication Date: 2011-12-15
    Description: A three dimensional model of Arctic Ocean circulation and mixing, with a horizontal resolution of 18 km, is overlain by a biogeochemical model resolving the physical, chemical and biological transport and transformations of phosphorus, alkalinity, oxygen and carbon, including the air-sea exchange of dissolved gases and the riverine delivery of dissolved organic carbon. The model qualitatively captures the observed regional and seasonal trends in surface ocean PO4, dissolved inorganic carbon, total alkalinity, and pCO2. Integrated annually, over the basin, the model suggests a net annual uptake of 59 Tg C a−1, within the range of published estimates based on the extrapolation of local observations (20–199 Tg C a−1). This flux is attributable to the cooling (increasing solubility) of waters moving into the basin, mainly from the subpolar North Atlantic. The air-sea flux is regulated seasonally and regionally by sea-ice cover, which modulates both air-sea gas transfer and the photosynthetic production of organic matter, and by the delivery of riverine dissolved organic carbon (RDOC), which drive the regional contrasts in pCO2 between Eurasian and North American coastal waters. Integrated over the basin, the delivery and remineralization of RDOC reduces the net oceanic CO2 uptake by ∼10%.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Interconnection of nitrogen fixers and iron in the Pacific Ocean: Theory and numerical simulations (2012)
    Wiley
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    Publication Date: 2012-01-26
    Description: We examine the interplay between iron supply, iron concentrations and phytoplankton communities in the Pacific Ocean. We present a theoretical framework which considers the competition for iron and nitrogen resources between phytoplankton to explain where nitrogen fixing autotrophs (diazotrophs, which require higher iron quotas, and have slower maximum growth) can co-exist with other phytoplankton. The framework also indicates that iron and fixed nitrogen concentrations can be strongly controlled by the local phytoplankton community. Together with results from a three-dimensional numerical model, we characterize three distinct biogeochemical provinces: 1) where iron supply is very low diazotrophs are excluded, and iron-limited nondiazotrophic phytoplankton control the iron concentrations; 2) a transition region where nondiazotrophic phytoplankton are nitrogen limited and control the nitrogen concentrations, but the iron supply is still too low relative to nitrate to support diazotrophy; 3) where iron supplies increase further relative to the nitrogen source, diazotrophs and other phytoplankton coexist; nitrogen concentrations are controlled by nondiazotrophs and iron concentrations are controlled by diazotrophs. The boundaries of these three provinces are defined by the rate of supply of iron relative to the supply of fixed nitrogen. The numerical model and theory provide a useful tool to understand the state of, links between, and response to changes in iron supply and phytoplankton community structure that have been suggested by observations.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Global relationship between phytoplankton diversity and productivity in the ocean (2014)
    Springer Nature
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    Publication Date: 2014-07-03
    Description: Article The mechanisms that determine the relationship between diversity and productivity in marine phytoplankton remain unclear. Here, Vallina et al. show that selective predation and transient competitive exclusion determine phytoplankton community composition. Nature Communications doi: 10.1038/ncomms5299 Authors: S. M. Vallina, M. J. Follows, S. Dutkiewicz, J. M. Montoya, P. Cermeno, M. Loreau
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 7
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    Emergent biogeography of microbial communities in a model ocean (2007)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2007-03-31
    Description: A marine ecosystem model seeded with many phytoplankton types, whose physiological traits were randomly assigned from ranges defined by field and laboratory data, generated an emergent community structure and biogeography consistent with observed global phytoplankton distributions. The modeled organisms included types analogous to the marine cyanobacterium Prochlorococcus. Their emergent global distributions and physiological properties simultaneously correspond to observations. This flexible representation of community structure can be used to explore relations between ecosystems, biogeochemical cycles, and climate change.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Follows, Michael J -- Dutkiewicz, Stephanie -- Grant, Scott -- Chisholm, Sallie W -- New York, N.Y. -- Science. 2007 Mar 30;315(5820):1843-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 54-1514 MIT, Cambridge, MA 02139, USA. mick@mit.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17395828" target="_blank"〉PubMed〈/a〉
    Keywords: Biomass ; Computer Simulation ; *Ecosystem ; Geography ; Light ; Mathematics ; Models, Biological ; Oceans and Seas ; Phytoplankton/growth & development/*physiology ; Prochlorococcus/growth & development/*physiology ; Seawater/*microbiology ; Temperature
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Patterns of diversity in marine phytoplankton (2010)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2010-02-27
    Description: Spatial diversity gradients are a pervasive feature of life on Earth. We examined a global ocean circulation, biogeochemistry, and ecosystem model that indicated a decrease in phytoplankton diversity with increasing latitude, consistent with observations of many marine and terrestrial taxa. In the modeled subpolar oceans, seasonal variability of the environment led to competitive exclusion of phytoplankton with slower growth rates and lower diversity. The relatively weak seasonality of the stable subtropical and tropical oceans in the global model enabled long exclusion time scales and prolonged coexistence of multiple phytoplankton with comparable fitness. Superimposed on the decline in diversity seen from equator to pole were "hot spots" of enhanced diversity in some regions of energetic ocean circulation, which reflected lateral dispersal.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Barton, Andrew D -- Dutkiewicz, Stephanie -- Flierl, Glenn -- Bragg, Jason -- Follows, Michael J -- New York, N.Y. -- Science. 2010 Mar 19;327(5972):1509-11. doi: 10.1126/science.1184961. Epub 2010 Feb 25.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA. adbarton@mit.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20185684" target="_blank"〉PubMed〈/a〉
    Keywords: *Biodiversity ; Biomass ; Climate ; *Ecosystem ; Environment ; Geography ; Models, Biological ; Oceans and Seas ; *Phytoplankton/growth & development/physiology ; Population Dynamics ; Seasons ; *Seawater
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Single-cell genomics reveals hundreds of coexisting subpopulations in wild Prochlorococcus (2014)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2014-04-26
    Description: Extensive genomic diversity within coexisting members of a microbial species has been revealed through selected cultured isolates and metagenomic assemblies. Yet, the cell-by-cell genomic composition of wild uncultured populations of co-occurring cells is largely unknown. In this work, we applied large-scale single-cell genomics to study populations of the globally abundant marine cyanobacterium Prochlorococcus. We show that they are composed of hundreds of subpopulations with distinct "genomic backbones," each backbone consisting of a different set of core gene alleles linked to a small distinctive set of flexible genes. These subpopulations are estimated to have diverged at least a few million years ago, suggesting ancient, stable niche partitioning. Such a large set of coexisting subpopulations may be a general feature of free-living bacterial species with huge populations in highly mixed habitats.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kashtan, Nadav -- Roggensack, Sara E -- Rodrigue, Sebastien -- Thompson, Jessie W -- Biller, Steven J -- Coe, Allison -- Ding, Huiming -- Marttinen, Pekka -- Malmstrom, Rex R -- Stocker, Roman -- Follows, Michael J -- Stepanauskas, Ramunas -- Chisholm, Sallie W -- New York, N.Y. -- Science. 2014 Apr 25;344(6182):416-20. doi: 10.1126/science.1248575.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Civil and Environmental Engineering, Massachusetts Institute of Technology (MIT), 77 Massachusetts Avenue, Cambridge, MA 02139, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24763590" target="_blank"〉PubMed〈/a〉
    Keywords: Atlantic Ocean ; Biological Evolution ; Ecosystem ; Genes, Bacterial ; *Genetic Variation ; *Genome, Bacterial ; Metagenomics ; Molecular Sequence Data ; Mutation ; Phylogeny ; Polymorphism, Single Nucleotide ; Prochlorococcus/classification/*genetics/*physiology ; Seasons ; Seawater/*microbiology ; Sequence Analysis, DNA ; Single-Cell Analysis
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    Environmental science. Rethinking the marine carbon cycle: factoring in the multifarious lifestyles of microbes (2015)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2015-02-14
    Description: The profound influence of marine plankton on the global carbon cycle has been recognized for decades, particularly for photosynthetic microbes that form the base of ocean food chains. However, a comprehensive model of the carbon cycle is challenged by unicellular eukaryotes (protists) having evolved complex behavioral strategies and organismal interactions that extend far beyond photosynthetic lifestyles. As is also true for multicellular eukaryotes, these strategies and their associated physiological changes are difficult to deduce from genome sequences or gene repertoires-a problem compounded by numerous unknown function proteins. Here, we explore protistan trophic modes in marine food webs and broader biogeochemical influences. We also evaluate approaches that could resolve their activities, link them to biotic and abiotic factors, and integrate them into an ecosystems biology framework.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Worden, Alexandra Z -- Follows, Michael J -- Giovannoni, Stephen J -- Wilken, Susanne -- Zimmerman, Amy E -- Keeling, Patrick J -- New York, N.Y. -- Science. 2015 Feb 13;347(6223):1257594. doi: 10.1126/science.1257594.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA. Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA. Integrated Microbial Biodiversity Program, Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada. azworden@mbari.org. ; Department of Earth Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. ; Department of Microbiology, Oregon State University, Corvallis, OR 97331, USA. ; Monterey Bay Aquarium Research Institute, Moss Landing, CA 95039, USA. ; Integrated Microbial Biodiversity Program, Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada. Department of Botany, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25678667" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biological Evolution ; *Carbon Cycle ; Eukaryota/*metabolism ; Phytoplankton/*metabolism ; Seawater/*microbiology ; Symbiosis ; Zooplankton/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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