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Niche construction by non-diazotrophs for N2 fixers in the eastern tropical North Atlantic Ocean

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posted on 2023-05-20, 05:18 authored by Singh, A, Lennart BachLennart Bach, Fischer, T, Hauss, H, Kiko, R, Paul, AJ, Stange, P, Vandromme, P, Riebesell, U

Diazotrophic dinitrogen (N2) fixation contributes ~76% to “new” nitrogen inputs to the sunlit open ocean, but environmental factors determining N2 fixation rates are not well constrained. Excess phosphate (phosphate–nitrate/16 > 0) and iron availability control N2 fixation rates in the eastern tropical North Atlantic (ETNA), but it remains an open question how excess phosphate is generated within or supplied to the phosphate‐depleted sunlit layer. Our observations in the ETNA region (8°N–15°N, 19°W–23°W) suggest that Prochlorococcus and Synechococcus, the two ubiquitous non‐diazotrophic cyanobacteria with cellular N:P ratios higher than the Redfield ratio, create an environment of excess phosphate, which cannot be explained by diapycnal mixing, atmospheric, and riverine inputs. Thus, our results unveil a new biogeochemical niche construction mechanism by non‐diazotrophic cyanobacteria for their diazotrophic phylum group members (N2 fixers). Our observations may help to understand the prevalence of diazotrophy in low‐phosphate, oligotrophic regions.

History

Publication title

Geophysical Research Letters

Volume

44

Issue

13

Pagination

6904-6913

ISSN

0094-8276

Department/School

Institute for Marine and Antarctic Studies

Publisher

Amer Geophysical Union

Place of publication

2000 Florida Ave Nw, Washington, USA, Dc, 20009

Rights statement

Copyright 2019 American Geophysical Union

Repository Status

  • Open

Socio-economic Objectives

Expanding knowledge in the earth sciences

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