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

Singh, Arvind, Bach, Lennart T. , Fischer, Tim, Hauss, Helena , Kiko, Rainer, Paul, Allanah J., Stange, Paul, Vandromme, Pieter and Riebesell, Ulf (2017) Niche construction by non-diazotrophs for N2 fixers in the eastern tropical North Atlantic Ocean. Open Access Geophysical Research Letters, 44 (13). pp. 6904-6913. DOI 10.1002/2017GL074218.

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Abstract

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.

Document Type: Article
Keywords: Ecosystem engineering, Environmental controls, Prochlorococcus, Redfield ratio, Synechococcus, Trichodesmium
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EOE-N Experimental Ecology - Food Webs
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > SFB 754
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EOE-B Experimental Ecology - Benthic Ecology
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Kiel University
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1002/2017GL074218
ISSN: 0094-8276
Projects: SFB754, Future Ocean, SOPRAN
Expeditions/Models/Experiments:
Date Deposited: 24 Jul 2017 09:15
Last Modified: 01 Feb 2019 15:01
URI: http://oceanrep.geomar.de/id/eprint/38859

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