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

Type Article
Date 2020-10
Language English
Author(s) Tang Weiyi1, Cerdán-García Elena2, Berthelot Hugo3, Polyviou Despo2, Wang Seaver1, Baylay Alison2, Whitby Hannah3, Planquette Helene5, Mowlem Matthew4, Robidart Julie4, Cassar Nicolas1, 3
Affiliation(s) 1 : Division of Earth and Ocean Sciences, Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA
2 : Department of Ocean and Earth Sciences, National Oceanography Centre, University of Southampton, European Way, SO14 3ZH, Southampton, UK
3 : CNRS, Univ Brest, IRD, Ifremer, LEMAR, F-29280 Plouzané, France
4 : Ocean Technology and Engineering Group, National Oceanography Centre, European Way, SO14 3ZH, Southampton, UK
5 : CNRS, Univ Brest, IRD, Ifremer, LEMAR, F-29280 Plouzané, France
Source Isme Journal (1751-7362) (Springer Science and Business Media LLC), 2020-10 , Vol. 14 , N. 10 , P. 2514-2526
DOI 10.1038/s41396-020-0703-6
WOS© Times Cited 4
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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Tang Weiyi, Cerdán-García Elena, Berthelot Hugo, Polyviou Despo, Wang Seaver, Baylay Alison, Whitby Hannah, Planquette Helene, Mowlem Matthew, Robidart Julie, Cassar Nicolas (2020). New insights into the distributions of nitrogen fixation and diazotrophs revealed by high-resolution sensing and sampling methods. Isme Journal, 14(10), 2514-2526. Publisher's official version : https://doi.org/10.1038/s41396-020-0703-6 , Open Access version : https://archimer.ifremer.fr/doc/00635/74705/