Meridional patterns of inorganic nutrient limitation and co-limitation of bacterial growth in the Atlantic Ocean

Michelle Hale, Richard Rivkin, William Li

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    Abstract

    Growth of heterotrophic bacteria is generally considered to be controlled by temperature and the availability of organic substrates, however there is evidence that bacterial growth can also be limited by the concentrations or supply rate of inorganic nutrients (i.e. nitrogen, phosphorus or iron). We examined spatial and seasonal patterns of organic carbon and inorganic nutrient (N and P) limitation of bacterial growth along each of two meridional transects through the Atlantic Ocean, during contrasting seasons. Here we used nutrient bioassays to demonstrate widespread inorganic nutrient limitation and co-limitation with organic carbon in the oligotrophic temperate, tropical and subtropical ocean. There were distinct seasonal and spatial differences in the inorganic and organic nutrient limitation of bacterial growth, with inorganic nitrogen as the primary limiting nutrient in May/June, and inorganic nitrogen and organic carbon co-limiting growth in October/November. There was no evidence that the availability of inorganic phosphorus limited bacterial growth in the Southern Hemisphere. We propose that the patterns of nutrient-dependent bacterial growth reflect seasonal and spatial differences in aeolian inputs and the quality of dissolved organic matter, and that bacteria directly compete with autotrophs for inorganic nutrients in the oligotrophic regions of the World Ocean. The findings of this study have important implications for understanding the balance between the biological and microbial carbon pumps, and the modelling of the net metabolic balance of the Ocean in response to climate-driven changes in nutrient inputs.
    Original languageEnglish
    Pages (from-to)90-98
    Number of pages9
    JournalProgress in Oceanography
    Volume158
    Early online date2 Dec 2016
    DOIs
    Publication statusPublished - 1 Nov 2017

    Keywords

    • Nannoplankton
    • growth rates
    • nutrients (mineral)
    • limiting factors
    • Atlantic Meridional Transect
    • Atlantic Ocean

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