Contrasting juxtaposition of two paradigms for diazotrophy in an Earth System Model of intermediate complexity.

Löptien, Ulrike and Dietze, Heiner (2020) Contrasting juxtaposition of two paradigms for diazotrophy in an Earth System Model of intermediate complexity. Open Access Biogeosciences Discussions . DOI 10.5194/bg-2020-96.

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Nitrogen fixers, or diazotrophs, play a key role in the carbon and nitrogen cycle of the world oceans, but the controlling mechanisms are not comprehensively understood yet. The present study compares two paradigms on the ecological niche of diazotrophs in an Earth System Model (ESM). In our standard model configuration, which is representative for most of the state-of-the-art pelagic ecosystem models, diazotrophs take advantage of zooplankton featuring a lower food preference for diazotrophs than for ordinary phytoplankton. We compare this paradigm with the idea that diazotrophs are more competitive under oligotrophic conditions, characterized by low (dissolved, particulate, organic and inorganic) phosphorous availability. Both paradigms are supported by observational evidence and lead to a similar good agreement to the most recent and advanced observation-based nitrogen fixation estimate in our ESM framework. Further, we illustrate that the similarity between the two paradigms breaks in a RCP 8.5 anthropogenic emission scenario. We conclude that a more advanced understanding of the ecological niche of diazotrophs is mandatory for assessing the cycling of essential nutrients, especially under changing environmental conditions. Our results call for more in-situ measurements of cyanobacteria biomass if major controls of nitrogen fixation in the oceans are to be dissected.

Document Type: Article
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
Kiel University
Refereed: No
Open Access Journal?: Yes
DOI etc.: 10.5194/bg-2020-96
ISSN: 1810-6285
Related URLs:
Projects: Reduced Complexity Models, Towards a deeper Understanding Cyanobacteria Blooms in the Baltic Sea, Reducing uncertainties in projected Southern Ocean Carbon fluxes
Date Deposited: 26 Mar 2020 08:24
Last Modified: 26 Mar 2020 08:26

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