Kustka, A. B.. Marine Sciences Research Center, kustka@msrc.sunysb.edu
Saņudo-Wilhelmy, S. B.. Marine Sciences Research Center, ssanudo@ccmail.sunysb.edu
Carpenter, E. J.. Marine Sciences Research Center, ecarpenter@ccmail.sunysb.edu

 
IRON QUOTAS OF SOUTH PACIFIC POPULATIONS OF THE PLANKTONIC NITROGEN FIXING CYANOBACTERIA, TRICHODESMIUM SPP.
 
Trichodesmium spp. plays a prominent role in the biogeochemical cycling of nitrogen and carbon due to their ability to add new nitrogen to open ocean surface waters. It has been hypothesized that ambient iron levels limit the productivity and nitrogen fixation of Trichodesmium, as dinitrogen reduction is both iron and energy expensive. Limitations on biomass and N2 fixation should be particularly evident in the South Pacific, where aeolian dust inputs are relatively low. Trace metal clean samples of Trichodesmium spp. colonies were collected during April 1998 at fifteen stations in the central and western South Pacific (New Caledonia - Tonga). Preliminary analysis indicates iron contents ranged from ~2 to 22 picomoles per colony, lower levels than previously reported for the more intensely studied Caribbean populations. The median iron to nitrogen ratio of our S. Pacific collections of 1:1800 (mol:mol) is consistent with the range of ratios observed for non nitrogen-fixing open ocean phytoplankton. Many stations exhibited low Trichodesmium densities, and the Trichodesmium depth-integrated abundance did not strongly co-vary with iron:nitrogen content. The iron content of colonies will be related to water column trace metal distributions.
 
Day: Thursday, Feb. 4
Time: 03:30 - 03:45pm
Location: Sweeney Center
 
Code: SS28TH0330S