Optimality-based Trichodesmium diazotrophy in the North Atlantic subtropical gyre.

Fernandez-Castro, B., Pahlow, Markus, Mourino-Carballido, B., Maranon, E. and Oschlies, Andreas (2016) Optimality-based Trichodesmium diazotrophy in the North Atlantic subtropical gyre. Journal of Plankton Research, 38 (4). pp. 946-963. DOI 10.1093/plankt/fbw047.

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Abstract

A recent optimality-based model for phytoplankton growth and diazotrophy was applied at two stations located in the oligotrophic western and the ultra-oligotrophic eastern subtropical North Atlantic. Contrary to the common view that diazotrophy is favoured by nitrogen (N) depletion relative to the Redfield equivalent of phosphorus (P), we find that optimality-based diazotrophy could explain N fixation in both regions in spite of relatively high N:P supply ratios. This is possible because the availability of an additional source of N for diazotrophs makes them strong competitors for P under oligotrophic conditions. The best reproduction of observations, especially of net primary production, is only achieved with preferential remineralization of P relative to N and atmospheric deposition. In line with observations, a higher rate of nitrogen fixation is predicted for the eastern site, owing to a larger niche for diazotrophs resulting from stronger oligotrophy and lower N:P supply ratios due to weaker atmospheric N deposition. Because the competitive advantage of diazotrophs under nutrient starvation diminishes with increasing supply N:P ratio, the predicted increase of atmospheric N deposition due to anthropogenic activity could negatively affect N2 fixation in the Atlantic Ocean.

Document Type: Article
Keywords: optimality-based model; nitrogen fixation; atmospheric deposition; preferential remineralization; subtropical North Atlantic
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
OceanRep > The Future Ocean - Cluster of Excellence > FO-R05
OceanRep > SFB 754 > B2
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > SFB 754
Kiel University
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1093/plankt/fbw047
ISSN: 0142-7873
Projects: VARITROP, NICANOR, CREST, SFB754, Future Ocean, PalMod in-kind
Date Deposited: 13 Jul 2016 09:10
Last Modified: 01 Feb 2019 15:11
URI: http://oceanrep.geomar.de/id/eprint/33354

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