Sweeney, C. Lamont-Doherty Earth Observatory, csweeney@ldeo.columbia.edu
Codispoti, L. A. Old Dominion University, lou@ccpo.odu.edu
Gordon, L. I. Oregon State University, School of Oceanography, lgordon@oce.orst.edu
Millero, F. D. University of Miami, Rosenstiel School of Marine and Atmospheric Science, millero@oj.rsmas.miami.edu
Smith, W. O. The college of William and Mary, Virginia Institute of Marine Science, wos@vims.edu

With the onset of the bloom in the southwestern Ross Sea, decrease observed in the nutrients and the carbon dioxide concentrations below the winter values is due primarily to dilution by ice melt and biological utilization. By normalizing the nutrients and carbon values to a constant salinity to correct for ice melting, we were able to observe the biological utilization of nutrients and carbon. Ratios of total inorganic carbon (C) to phosphate and total inorganic nitrogen (N) to phosphate show two very distinct regimes. Based on the net utilization of silicate verses C and N, a regime dominated by diatoms and another by Phaeocystis was identified. The diatom regime was characterized by a low C/P (76+/-2) and low N/P (9.6+/-0.3) ratios; in contrast, the Phaeocystis regime showed high C/P (144+/-3) and high N/P (19.7+/-0.4) ratios. The C/N ratio (7.3+/-0.2) in the two regimes was similar. This suggests that Phaeocystis will utilize less phosphate per unit carbon than diatoms as long as total inorganic nitrogen is not limiting. The dominant regimes tended to homogenize through lateral mixing or succession of species as the bloom progressed. The mixed layer depth is a key physical constraint to the diatom growth.
Day: Wednesday, Feb. 3
Time: 04:30 - 04:45pm
Location: Sweeney Center
Code: SS31WE0430S