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Environmental controls on the biogeography of diazotrophy and Trichodesmium in the Atlantic Ocean
Author(s) -
Snow J. T.,
Schlosser C.,
Woodward E. M. S.,
Mills M. M.,
Achterberg E. P.,
Mahaffey C.,
Bibby T. S.,
Moore C. M.
Publication year - 2015
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1002/2015gb005090
Subject(s) - trichodesmium , diazotroph , ocean gyre , oceanography , tropical atlantic , biogeography , ecology , biology , environmental science , subtropics , nitrogen fixation , sea surface temperature , geology , paleontology , bacteria
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 CO 2 , and nutrients including iron (Fe) and phosphorus (P), all suggested to be important. Synthesizing data from seven cruises collectively spanning large temporal and spatial scales across the Atlantic Ocean, including two previously unreported studies crossing the largely undersampled South Atlantic gyre, we assessed the relationship between proposed environmental drivers and both community N 2 fixation rates and the distribution of Trichodesmium . Simple linear regression analysis would suggest no relationship between any of the sampled environmental variables and N 2 fixation rates. However, considering the concentrations of iron and phosphorus together within a simplified resource‐ratio framework, illustrated using an idealized 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.