Prezelin, B. B.. Univ. of California at Santa Barbara, barbara@icess.ucsb.edu
Hofmann, E. B.. Old Dominion University, hofmann@ccpo.odu.edu
Klinck, J. M.. Old Dominion University, klinck@ccpo.odu.edu
Mengelt, C. University of California at Santa Barbara, cmengelt@oce.orst.edu

 
THE LINKAGE BETWEEN UPPER CIRCUMPOLAR DEEP WATER (UPDW) AND PHYTOPLANKTON ASSEMBLAGES ON THE WEST ANTARCTIC PENINUSLA CONTINENTAL SHELF
 
Intrusion of the UPDW onto the western Antarctic shelf region in January 1993 provided opportunities for nutrient-rich, high silicate/nitrate ratio, warmer water to be injected into the upper mixed layer. Four sites, where bathymetric control produced upwelling of UCDW, were identified in a 50km by 400km band along the outer continental shelf. Localized subsurface diatom-dominated blooms were associated with each upwelling site and at one site that had experienced recent wind-driven upwelling of UCDW. Diatom-dominated blooms were not detected at any other shelf location, even though diatoms were present everywhere in the 80,000-km2 transect area and the UPDW lay beneath about one-third the area below 150m. We suggest that in the absence of episodic upwelling on the shelf, growth requirements for high silicate/nitrate or other upwelled constituents (i.e. trace metals) were not sufficiently met for diatoms to achieve high abundance or community dominance. We hypothesize that diatom-enriched communities will be evident at other times and under different seasonal conditions, if, AND only if, the above physical structuring events are also occurring. By comparison, phytoflagellate- and chlorophyte-dominated communities occupied transition water between UPDW and shelf waters, southerly flowing waters out of the Gerlache strait, and/or summertime glacial ice-melt surface waters.
 
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
 
Code: SS04TH1566S