Nitrogen fixation by Trichodesmium spp.: An important source of new nitrogen to the tropical and subtropical North Atlantic Ocean

	Become an AGU Member Subscribe to AGU Journals



Read Full Article (file size: 499879 bytes) Cited by GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 19, GB2024, doi:10.1029/2004GB002331, 2005 Nitrogen fixation by Trichodesmium spp.: An important source of new nitrogen to the tropical and subtropical North Atlantic Ocean Douglas G. Capone Wrigley Institute for Environmental Studies and Department of Biological Sciences, University of Southern California, Los Angeles, California, USA James A. Burns Wrigley Institute for Environmental Studies and Department of Biological Sciences, University of Southern California, Los Angeles, California, USA Joseph P. Montoya School of Biology, Georgia Institute of Technology, Atlanta, Georgia, USA Ajit Subramaniam Lamont Doherty Earth Observatory of, Columbia University, Palisades, New York, USA Claire Mahaffey Wrigley Institute for Environmental Studies and Department of Biological Sciences, University of Southern California, Los Angeles, California, USA Troy Gunderson Wrigley Institute for Environmental Studies and Department of Biological Sciences, University of Southern California, Los Angeles, California, USA Anthony F. Michaels Wrigley Institute for Environmental Studies and Department of Biological Sciences, University of Southern California, Los Angeles, California, USA Edward J. Carpenter Romberg Tiburon Center, San Francisco State University, Tiburon, California, USA Abstract 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 N₂ fixation by Trichodesmium spp. at many stations that equalled or exceeded the estimated vertical flux of NO₃ ⁻ into the euphotic zone by diapycnal mixing. Areal rates are consistent with those derived from several indirect geochemical analyses. Direct measurements of N₂ fixation rates by Trichodesmium are also congruent with upper water column N budgets derived from parallel determinations of stable isotope distributions, clearly showing that N₂ 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 × 10¹² mol N by Trichodesmium N₂ fixation alone. This input can account for a substantial fraction of the N₂ fixation in the North Atlantic inferred by several of the geochemical approaches. Received 6 July 2004; accepted 9 March 2005; published 8 June 2005. Keywords: North Atlantic; nitrogen fixation; trichodesmium. Index Terms: 4805 Oceanography: Biological and Chemical: Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4912); 4815 Oceanography: Biological and Chemical: Ecosystems, structure, dynamics, and modeling (0439); 4845 Oceanography: Biological and Chemical: Nutrients and nutrient cycling (0470, 1050); 4855 Oceanography: Biological and Chemical: Phytoplankton; 4840 Oceanography: Biological and Chemical: Microbiology and microbial ecology (0465). Read Full Article (file size: 499879 bytes) Cited by Citation: Capone, D. G., J. A. Burns, J. P. Montoya, A. Subramaniam, C. Mahaffey, T. Gunderson, A. F. Michaels, and E. J. Carpenter (2005), Nitrogen fixation by Trichodesmium spp.: An important source of new nitrogen to the tropical and subtropical North Atlantic Ocean, Global Biogeochem. Cycles, 19, GB2024, doi:10.1029/2004GB002331. Copyright 2005 by the American Geophysical Union.

Abstract