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Optimality-based Trichodesmium diazotrophy in the North Atlantic subtropical gyre

Optimality-based Trichodesmium diazotrophy in the North Atlantic subtropical gyre
Optimality-based Trichodesmium diazotrophy in the North Atlantic subtropical gyre
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.
Atmospheric deposition, Nitrogen fixation, Optimality-based model, Preferential remineralization, Subtropical North Atlantic
0142-7873
946-963
Fernández-Castro, B.
8017e93c-d5ee-4bba-b443-9c72ca512d61
Pahlow, M.
6d26a9ea-d2f6-408a-8b6b-9311de387f77
Mouriño-Carballido, B.
c1dbf004-40db-4dbb-ac0c-2fe2c96d40b3
Marañón, E.
92f9d2a8-cfe4-4f67-86a1-793af860899a
Oschlies, A.
d87645a2-42d7-4879-a481-d5385d5b85bf
Fernández-Castro, B.
8017e93c-d5ee-4bba-b443-9c72ca512d61
Pahlow, M.
6d26a9ea-d2f6-408a-8b6b-9311de387f77
Mouriño-Carballido, B.
c1dbf004-40db-4dbb-ac0c-2fe2c96d40b3
Marañón, E.
92f9d2a8-cfe4-4f67-86a1-793af860899a
Oschlies, A.
d87645a2-42d7-4879-a481-d5385d5b85bf

Fernández-Castro, B., Pahlow, M., Mouriño-Carballido, B., Marañón, E. and Oschlies, A. (2016) Optimality-based Trichodesmium diazotrophy in the North Atlantic subtropical gyre. Journal of Plankton Research, 38 (4), 946-963. (doi:10.1093/plankt/fbw047).

Record type: Article

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.

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More information

Accepted/In Press date: 4 June 2016
e-pub ahead of print date: 8 July 2016
Published date: 1 August 2016
Keywords: Atmospheric deposition, Nitrogen fixation, Optimality-based model, Preferential remineralization, Subtropical North Atlantic

Identifiers

Local EPrints ID: 453896
URI: http://eprints.soton.ac.uk/id/eprint/453896
ISSN: 0142-7873
PURE UUID: 16fd8727-37d0-4c94-b3d1-fbed8ab718a1
ORCID for B. Fernández-Castro: ORCID iD orcid.org/0000-0001-7797-854X

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Date deposited: 25 Jan 2022 17:46
Last modified: 26 Jan 2022 03:03

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Contributors

Author: M. Pahlow
Author: B. Mouriño-Carballido
Author: E. Marañón
Author: A. Oschlies

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