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  • Springer Nature  (3)
  • Molecular Diversity Preservation International  (1)
  • Nature Research
  • 2020-2022  (4)
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  • 1
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    The global biological microplastic particle sink (2020)
    Springer Nature
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    Publication Date: 2020-10-07
    Description: Every year, about four percent of the plastic waste generated worldwide ends up in the ocean. What happens to the plastic there is poorly understood, though a growing body of evidence suggests it is rapidly spreading throughout the global ocean. The mechanisms of this spread are straightforward for buoyant larger plastics that can be accurately modelled using Lagrangian particle models. But the fate of the smallest size fractions (the microplastics) are less straightforward, in part because they can aggregate in sinking marine snow and faecal pellets. This biologically-mediated pathway is suspected to be a primary surface microplastic removal mechanism, but exactly how it might work in the real ocean is unknown. We search the parameter space of a new microplastic model embedded in an earth system model to show that biological uptake can significantly shape global microplastic inventory and distributions and even account for the budgetary “missing” fraction of surface microplastic, despite being an inefficient removal mechanism. While a lack of observational data hampers our ability to choose a set of “best” model parameters, our effort represents a first tool for quantitatively assessing hypotheses for microplastic interaction with ocean biology at the global scale.
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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  • 2
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    A committed fourfold increase in ocean oxygen loss (2021)
    Springer Nature
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    Publication Date: 2021-04-16
    Description: Less than a quarter of ocean deoxygenation that will ultimately be caused by historical CO2 emissions is already realized, according to millennial-scale model simulations that assume zero CO2 emissions from year 2021 onwards. About 80% of the committed oxygen loss occurs below 2000 m depth, where a more sluggish overturning circulation will increase water residence times and accumulation of respiratory oxygen demand. According to the model results, the deep ocean will thereby lose more than 10% of its pre-industrial oxygen content even if CO2 emissions and thus global warming were stopped today. In the surface layer, however, the ongoing deoxygenation will largely stop once CO2 emissions are stopped. Accounting for the joint effects of committed oxygen loss and ocean warming, metabolic viability representative for marine animals declines by up to 25% over large regions of the deep ocean, posing an unavoidable escalation of anthropogenic pressure on deep-ocean ecosystems.
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 3
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    Zooplankton grazing of microplastic can accelerate global loss of ocean oxygen (2021)
    Springer Nature
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    Publication Date: 2021-04-21
    Description: Global warming has driven a loss of dissolved oxygen in the ocean in recent decades. We demonstrate the potential for an additional anthropogenic driver of deoxygenation, in which zooplankton consumption of microplastic reduces the grazing on primary producers. In regions where primary production is not limited by macronutrient availability, the reduction of grazing pressure on primary producers causes export production to increase. Consequently, organic particle remineralisation in these regions increases. Employing a comprehensive Earth system model of intermediate complexity, we estimate this additional remineralisation could decrease water column oxygen inventory by as much as 10% in the North Pacific and accelerate global oxygen inventory loss by an extra 0.2–0.5% relative to 1960 values by the year 2020. Although significant uncertainty accompanies these estimates, the potential for physical pollution to have a globally significant biogeochemical signal that exacerbates the consequences of climate warming is a novel feedback not yet considered in climate research.
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 4
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    Independence of a Marine Unicellular Diazotroph to the Presence of NO3− (2021)
    Molecular Diversity Preservation International
    Details
    Publication Date: 2021-10-01
    Description: Marine nitrogen (N2) fixation was historically considered to be absent or reduced in nitrate (NO3−) rich environments. This is commonly attributed to the lower energetic cost of NO3− uptake compared to diazotrophy in oxic environments. This paradigm often contributes to making inferences about diazotroph distribution and activity in the ocean, and is also often used in biogeochemical ocean models. To assess the general validity of this paradigm beyond the traditionally used model organism Trichodesmium spp., we grew cultures of the unicellular cyanobacterium Crocosphaera watsonii WH8501 long term in medium containing replete concentrations of NO3−. NO3− uptake was measured in comparison to N2 fixation to assess the cultures’ nitrogen source preferences. We further measured culture growth rate, cell stoichiometry, and carbon fixation rate to determine if the presence of NO3− had any effect on cell metabolism. We found that uptake of NO3− by this strain of Crocosphaera was minimal in comparison to other N sources (~2–4% of total uptake). Furthermore, availability of NO3− did not statistically alter N2 fixation rate nor any aspect of cell physiology or metabolism measured (cellular growth rate, cell stoichiometry, cell size, nitrogen fixation rate, nitrogenase activity) in comparison to a NO3− free control culture. These results demonstrate the capability of a marine diazotroph to fix nitrogen and grow independently of NO3−. This lack of sensitivity of diazotrophy to NO3− suggests that assumptions often made about, and model formulations of, N2 fixation should be reconsidered.
    Electronic ISSN: 2076-2607
    Topics: Biology
    Published by Molecular Diversity Preservation International
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