Running Head: N2 Fixation in the Gulf of California
نویسندگان
چکیده
10 We report significant rates of dinitrogen (N2) fixation in the central basins of the Gulf of 11 California (GC) during July-August 2005. Mixing model estimates based upon δN values of 12 particulate matter in the surface mixed layer indicate that N2 fixation provides as much as 35% to 13 48% of the phytoplankton-based nitrogen demand in the central Guaymas and Carmen basins. 14 Microscopic analyses identify the responsible genera as the N2-fixing endosymbiont, Richelia 15 intracellularis with lesser contributions from the large non-heterocystous diazotroph 16 Trichodesmium. Analyses of remotely sensed chlorophyll a and sea surface temperature indicate 17 that primary production levels are elevated in regions of the GC where oceanographic conditions 18 are ideal in summertime for the growth of N2-fixing organisms. These findings suggest that 19 biological N2 fixation must be taken into account when assessing past and present nitrogen 20 dynamics in this environmentally important region. 21 22 23 RUNNING HEAD: N2 FIXATION IN THE GULF OF CALIFORNIA 2
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