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Environmental controls on the biogeography of diazotrophy and Trichodesmiumin the Atlantic Ocean

Environmental controls on the biogeography of diazotrophy and Trichodesmiumin the Atlantic Ocean
Environmental controls on the biogeography of diazotrophy and Trichodesmiumin the Atlantic Ocean
The cyanobacterium Trichodesmium is responsible for a significant proportion of the annual 'new' nitrogen introduced into the global ocean. Despite being arguably the best studied marine diazotroph, the factors controlling the distribution and growth of Trichodesmium remain a subject of debate, with sea surface temperature, the partial pressure of CO2 and nutrients including iron (Fe) and phosphorus (P), all suggested to be important. Synthesising data from 7 cruises collectively spanning large temporal and spatial scales across the Atlantic Ocean, including 2 previously unreported studies crossing the largely under-sampled South Atlantic gyre, we assessed the relationship between proposed environmental drivers and both community N2 fixation rates and the distribution of Trichodesmium. Simple linear regression analysis would suggest no relationship between any of the sampled environmental variables and N2 fixation rates. However, considering the concentrations of iron and phosphorus together within a simplified resource-ratio framework, illustrated using an idealised numerical model, indicates the combined effects these nutrients have on Trichodesmium and broader diazotroph biogeography, alongside the reciprocal maintenance of different biogeographic provinces of the (sub)-tropical Atlantic in states of Fe or P oligotrophy by diazotrophy. The qualitative principles of the resource-ratio framework are argued to be consistent with both the previously described North–south Atlantic contrast in Trichodesmium abundance and the presence and consequence of a substantial non-Trichodesmium diazotrophic community in the western South Atlantic subtropical gyre. A comprehensive, observation-based explanation of the interactions between Trichodesmium and the wider diazotrophic community with iron and phosphorus in the Atlantic Ocean is thus revealed.
nitrogen fixation, trichodesmium, resource-ratio, nutrient stress, iron, phosphorus
0886-6236
865-884
Snow, J.T.
74cb4d5c-2d12-4707-920f-95f230f42cfc
Schlosser, C.
7990a0cc-cfe9-4dd5-9c45-899c03186207
Woodward, E.M.S.
3ac3b98f-78c7-4b43-acf9-bba3253752b5
Mills, M.M.
8e317c31-d48d-48a2-85b3-de0871d01f36
Achterberg, E.P.
685ce961-8c45-4503-9f03-50f6561202b9
Mahaffey, C.A.
e80d5f0e-723f-4bef-b71b-922546556174
Bibby, T.S.
e04ea079-dd90-4ead-9840-00882de27ebd
Moore, C.M.
7ec80b7b-bedc-4dd5-8924-0f5d01927b12
Snow, J.T.
74cb4d5c-2d12-4707-920f-95f230f42cfc
Schlosser, C.
7990a0cc-cfe9-4dd5-9c45-899c03186207
Woodward, E.M.S.
3ac3b98f-78c7-4b43-acf9-bba3253752b5
Mills, M.M.
8e317c31-d48d-48a2-85b3-de0871d01f36
Achterberg, E.P.
685ce961-8c45-4503-9f03-50f6561202b9
Mahaffey, C.A.
e80d5f0e-723f-4bef-b71b-922546556174
Bibby, T.S.
e04ea079-dd90-4ead-9840-00882de27ebd
Moore, C.M.
7ec80b7b-bedc-4dd5-8924-0f5d01927b12

Snow, J.T., Schlosser, C., Woodward, E.M.S., Mills, M.M., Achterberg, E.P., Mahaffey, C.A., Bibby, T.S. and Moore, C.M. (2015) Environmental controls on the biogeography of diazotrophy and Trichodesmiumin the Atlantic Ocean. Global Biogeochemical Cycles, 29 (6), 865-884. (doi:10.1002/2015GB005090).

Record type: Article

Abstract

The cyanobacterium Trichodesmium is responsible for a significant proportion of the annual 'new' nitrogen introduced into the global ocean. Despite being arguably the best studied marine diazotroph, the factors controlling the distribution and growth of Trichodesmium remain a subject of debate, with sea surface temperature, the partial pressure of CO2 and nutrients including iron (Fe) and phosphorus (P), all suggested to be important. Synthesising data from 7 cruises collectively spanning large temporal and spatial scales across the Atlantic Ocean, including 2 previously unreported studies crossing the largely under-sampled South Atlantic gyre, we assessed the relationship between proposed environmental drivers and both community N2 fixation rates and the distribution of Trichodesmium. Simple linear regression analysis would suggest no relationship between any of the sampled environmental variables and N2 fixation rates. However, considering the concentrations of iron and phosphorus together within a simplified resource-ratio framework, illustrated using an idealised numerical model, indicates the combined effects these nutrients have on Trichodesmium and broader diazotroph biogeography, alongside the reciprocal maintenance of different biogeographic provinces of the (sub)-tropical Atlantic in states of Fe or P oligotrophy by diazotrophy. The qualitative principles of the resource-ratio framework are argued to be consistent with both the previously described North–south Atlantic contrast in Trichodesmium abundance and the presence and consequence of a substantial non-Trichodesmium diazotrophic community in the western South Atlantic subtropical gyre. A comprehensive, observation-based explanation of the interactions between Trichodesmium and the wider diazotrophic community with iron and phosphorus in the Atlantic Ocean is thus revealed.

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Accepted/In Press date: May 2015
e-pub ahead of print date: 26 June 2015
Published date: June 2015
Keywords: nitrogen fixation, trichodesmium, resource-ratio, nutrient stress, iron, phosphorus
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 377438
URI: http://eprints.soton.ac.uk/id/eprint/377438
ISSN: 0886-6236
PURE UUID: 9145db30-3e28-43d4-8299-b82087a8a8bd
ORCID for C.M. Moore: ORCID iD orcid.org/0000-0002-9541-6046

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Date deposited: 26 May 2015 10:40
Last modified: 27 Apr 2022 01:41

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Contributors

Author: J.T. Snow
Author: C. Schlosser
Author: E.M.S. Woodward
Author: M.M. Mills
Author: E.P. Achterberg
Author: C.A. Mahaffey
Author: T.S. Bibby
Author: C.M. Moore ORCID iD

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