CS29 Phytoplankton & Primary Production
Date: Monday, June 10, 2002
Time: 11:30:00 AM
Location: Oak Bay
 
SmithWO, VIMS, College of William and Mary, Gloucester Pt, USA, wos@vims.edu
Dennett, M, R, Woods Hole Oceanographic Institution, Woods Hole, USA, mdennett@whoi.edu
Caron, D, A, Department of Biological Sciences, University of Southern California, Los Angeles, USA, dcaron@wrigley.usc.edu
Mathot, S, , VIMS, College of William and Mary, Gloucester Pt., USA, sylviem@mac.com
 
TEMPORAL DYNAMICS OF THE FLAGELLATED AND COLONIAL STAGES OF PHAEOCYSTIS ANTARCTICA IN THE ROSS SEA
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Blooms of colonial P. antarctica occur over large areas in the southern Ross Sea., and sites where colonies occur often have significant vertical fluxes of carbon in the form of aggregated and flocculent material. Despite this fundamental role, the life history and temporal dynamics of this species are poorly known. Solitary P. antarctica cells numerically dominated the phytoplankton assemblage early in austral spring, although colony formation occurred almost immediately upon the onset of net population growth. The percentage of solitary cells relative to total cells was high in early austral spring but decreased to a minimum during late spring; specifically. Significant phytoplankton mortality rates were positively correlated with high ratios of solitary:total P. antarctica cells. The abundance of solitary P. antarctica cells began to increase again during late summer, but colonial cell numbers were always greater than those of solitary cells during this period. This increase in the contribution of solitary forms during summer may have been a consequence of more severe micronutrient limitation for the colonies, reduced microzooplankton grazing, or a combination of these and other factors.