Nitrogen fixation by Trichodesmium spp.: An important source of new nitrogen to the tropical North Atlantic Ocean
Copyright 2005 by the American Geophysical Union DOI:10.1029/2004GB002331 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 resul...
Published in: | Global Biogeochemical Cycles |
---|---|
Main Authors: | , , , , , , , |
Other Authors: | , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Georgia Institute of Technology
2005
|
Subjects: | |
Online Access: | http://hdl.handle.net/1853/43085 https://doi.org/10.1029/2004GB002331 |
Summary: | Copyright 2005 by the American Geophysical Union DOI:10.1029/2004GB002331 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 X 10 ¹² 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. |
---|