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New insights into the distributions of nitrogen fixation and diazotrophs revealed by high-resolution sensing and sampling methods

New insights into the distributions of nitrogen fixation and diazotrophs revealed by high-resolution sensing and sampling methods
New insights into the distributions of nitrogen fixation and diazotrophs revealed by high-resolution sensing and sampling methods
Nitrogen availability limits marine productivity across large ocean regions. Diazotrophs can supply new nitrogen to the marine environment via nitrogen (N2) fixation, relieving nitrogen limitation. The distributions of diazotrophs and N2 fixation have been hypothesized to be generally controlled by temperature, phosphorus, and iron availability in the global ocean. However, even in the North Atlantic where most research on diazotrophs and N2 fixation has taken place, environmental controls remain contentious. Here we measure diazotroph composition, abundance, and activity at high resolution using newly developed underway sampling and sensing techniques. We capture a diazotrophic community shift from Trichodesmium to UCYN-A between the oligotrophic, warm (25–29 °C) Sargasso Sea and relatively nutrient-enriched, cold (13–24 °C) subpolar and eastern American coastal waters. Meanwhile, N2 fixation rates measured in this study are among the highest ever recorded globally and show significant increase with phosphorus availability across the transition from the Gulf Stream into subpolar and coastal waters despite colder temperatures and higher nitrate concentrations. Transcriptional patterns in both Trichodesmium and UCYN-A indicate phosphorus stress in the subtropical gyre. Over this iron-replete transect spanning the western North Atlantic, our results suggest that temperature is the major factor controlling the diazotrophic community structure while phosphorous drives N2 fixation rates. Overall, the occurrence of record-high UCYN-A abundance and peak N2 fixation rates in the cold coastal region where nitrate concentrations are highest (~200 nM) challenges current paradigms on what drives the distribution of diazotrophs and N2 fixation.
1751-7362
2514-2526
Tang, Weiyi
adb1e1bd-a785-422b-a27f-f492014350d0
Cerdán-garcía, Elena
7171170a-2128-4369-87c3-cffddea2e414
Berthelot, Hugo
36e9059a-e1f9-468d-b5b7-12f356ba09a3
Polyviou, Despo
57dea764-2c54-44bb-a7ac-382ba19418cb
Wang, Seaver
8a646ccf-1dbc-4b7a-aef6-d70a08c151a0
Baylay, Alison
08ea69f8-9910-4c8b-86a9-602e45b8a44e
Whitby, Hannah
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Planquette, Hélène
d2e496e6-efd4-4c94-afac-15c139e5461b
Mowlem, Matthew
6f633ca2-298f-48ee-a025-ce52dd62124f
Robidart, Julie
a9b8d49c-c1e3-4a3b-a53c-685a0f2c7f93
Cassar, Nicolas
77fc58ca-3e20-44b5-b397-801ec4d8f5df
Tang, Weiyi
adb1e1bd-a785-422b-a27f-f492014350d0
Cerdán-garcía, Elena
7171170a-2128-4369-87c3-cffddea2e414
Berthelot, Hugo
36e9059a-e1f9-468d-b5b7-12f356ba09a3
Polyviou, Despo
57dea764-2c54-44bb-a7ac-382ba19418cb
Wang, Seaver
8a646ccf-1dbc-4b7a-aef6-d70a08c151a0
Baylay, Alison
08ea69f8-9910-4c8b-86a9-602e45b8a44e
Whitby, Hannah
5674cbba-a1ad-4392-a876-f293811225f5
Planquette, Hélène
d2e496e6-efd4-4c94-afac-15c139e5461b
Mowlem, Matthew
6f633ca2-298f-48ee-a025-ce52dd62124f
Robidart, Julie
a9b8d49c-c1e3-4a3b-a53c-685a0f2c7f93
Cassar, Nicolas
77fc58ca-3e20-44b5-b397-801ec4d8f5df

Tang, Weiyi, Cerdán-garcía, Elena, Berthelot, Hugo, Polyviou, Despo, Wang, Seaver, Baylay, Alison, Whitby, Hannah, Planquette, Hélène, Mowlem, Matthew, Robidart, Julie and Cassar, Nicolas (2020) New insights into the distributions of nitrogen fixation and diazotrophs revealed by high-resolution sensing and sampling methods. The ISME Journal, 14 (10), 2514-2526. (doi:10.1038/s41396-020-0703-6).

Record type: Article

Abstract

Nitrogen availability limits marine productivity across large ocean regions. Diazotrophs can supply new nitrogen to the marine environment via nitrogen (N2) fixation, relieving nitrogen limitation. The distributions of diazotrophs and N2 fixation have been hypothesized to be generally controlled by temperature, phosphorus, and iron availability in the global ocean. However, even in the North Atlantic where most research on diazotrophs and N2 fixation has taken place, environmental controls remain contentious. Here we measure diazotroph composition, abundance, and activity at high resolution using newly developed underway sampling and sensing techniques. We capture a diazotrophic community shift from Trichodesmium to UCYN-A between the oligotrophic, warm (25–29 °C) Sargasso Sea and relatively nutrient-enriched, cold (13–24 °C) subpolar and eastern American coastal waters. Meanwhile, N2 fixation rates measured in this study are among the highest ever recorded globally and show significant increase with phosphorus availability across the transition from the Gulf Stream into subpolar and coastal waters despite colder temperatures and higher nitrate concentrations. Transcriptional patterns in both Trichodesmium and UCYN-A indicate phosphorus stress in the subtropical gyre. Over this iron-replete transect spanning the western North Atlantic, our results suggest that temperature is the major factor controlling the diazotrophic community structure while phosphorous drives N2 fixation rates. Overall, the occurrence of record-high UCYN-A abundance and peak N2 fixation rates in the cold coastal region where nitrate concentrations are highest (~200 nM) challenges current paradigms on what drives the distribution of diazotrophs and N2 fixation.

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More information

Accepted/In Press date: 11 June 2020
e-pub ahead of print date: 24 June 2020
Published date: 1 October 2020

Identifiers

Local EPrints ID: 444445
URI: http://eprints.soton.ac.uk/id/eprint/444445
ISSN: 1751-7362
PURE UUID: fff3df61-69e5-45f1-ac28-9fd2f2327b88
ORCID for Elena Cerdán-garcía: ORCID iD orcid.org/0000-0002-0409-7722

Catalogue record

Date deposited: 19 Oct 2020 16:33
Last modified: 26 Nov 2021 03:09

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Contributors

Author: Weiyi Tang
Author: Hugo Berthelot
Author: Despo Polyviou
Author: Seaver Wang
Author: Alison Baylay
Author: Hannah Whitby
Author: Hélène Planquette
Author: Matthew Mowlem
Author: Julie Robidart
Author: Nicolas Cassar

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