Biogeosciences
www.biogeosciences.net
1726-4170
1726-4189
4
3
2007
10.5194/bg-4-369-2007
http://www.biogeosciences.net/4/369/2007/
http://www.biogeosciences.net/4/369/2007/bg-4-369-2007.html
http://www.biogeosciences.net/4/369/2007/bg-4-369-2007.pdf
369
376
2007-06-22
Spatial variation in N<sub>2</sub>-fixation rate and diazotroph activity in the Tropical Atlantic
J. P. Montoya
montoya@gatech.edu
M. Voss
D. G. Capone
Georgia Institute of Technology, Atlanta GA, USA
Institut für Ostseeforschung, Warnemünde, Germany
University of Southern California, Los Angeles CA, USA
A variety of N<sub>2</sub>-fixers occur in oligotrophic waters and these
diazotrophs make a substantial contribution to the nitrogen budget of the
upper water column. A synthesis of previously published and new rate
measurements for the North Atlantic provides insight into the role of two
different groups of N<sub>2</sub>-fixers (<i>Trichodesmium</i> and small diazotrophs) in supporting
N<sub>2</sub> fixation in the tropical Atlantic. The highest rates of N<sub>2</sub>
fixation occurred in the western part of the basin, but the full data set
showed no significant difference between the eastern and western parts of
the basin in overall rates of N<sub>2</sub>-fixation by the two groups of
diazotrophs. N<sub>2</sub>-fixation by <i>Trichodesmium</i> was strongly dominant in the western part
of the basin while small diazotrophs played a much larger role to the east
of 40° W. The reasons for this shift in dominance are unclear, as is the
identity of the small organisms fixing N<sub>2</sub> in the water column.
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