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Nitrogen fixation by Trichodesmium spp.: An important source of new nitrogen to the tropical and subtropical North Atlantic Ocean
Author(s) -
Capone Douglas G.,
Burns James A.,
Montoya Joseph P.,
Subramaniam Ajit,
Mahaffey Claire,
Gunderson Troy,
Michaels Anthony F.,
Carpenter Edward J.
Publication year - 2005
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 - 10.1029/2004gb002331
Subject(s) - trichodesmium , photic zone , subtropics , oceanography , nitrogen fixation , tropical atlantic , environmental science , new production , tropics , nitrogen , phytoplankton , geology , nutrient , diazotroph , biology , sea surface temperature , ecology , chemistry , organic chemistry
The broad distribution and often high densities of the cyanobacterium Trichodesmium spp. in oligotrophic waters imply a substantial role for this one taxon in the oceanic N cycle of the marine tropics and subtropics. New results from 154 stations on six research cruises in the North Atlantic Ocean show depth‐integrated N 2 fixation by Trichodesmium spp. at many stations that equalled or exceeded the estimated vertical flux of NO 3 − into the euphotic zone by diapycnal mixing. Areal rates are consistent with those derived from several indirect geochemical analyses. Direct measurements of N 2 fixation rates by Trichodesmium are also congruent with upper water column N budgets derived from parallel determinations of stable isotope distributions, clearly showing that N 2 fixation by Trichodesmium is a major source of new nitrogen in the tropical North Atlantic. We project a conservative estimate of the annual input of new N into the tropical North Atlantic of at least 1.6 × 10 12 mol N by Trichodesmium N 2 fixation alone. This input can account for a substantial fraction of the N 2 fixation in the North Atlantic inferred by several of the geochemical approaches.