Spatial and Temporal Variability of SeaWiFS Chlorophyll a Distributions West of the Antarctic Peninsula: Implications for Krill Production

Marina Marrari*, Kendra L. Daly and Chuanmin Hu

College of Marine Science

University of South Florida

140 Seventh Avenue South

St. Petersburg, FL 33701, USA

* Corresponding author: mmarrari@marine.usf.edu; Tel: 727-553-1207; Fax: 727-553-1186

Seasonal SeaWiFS chlorophyll distributions were investigated in relation to sea ice dynamics between 1997 and 2004 for waters west of the Antarctic Peninsula (45-75ºS, 50-80ºW) in order to better understand reproductive patterns and recruitment success of the Antarctic krill, Euphausia superba. Climatology patterns showed that the Bellingshausen Sea and Marguerite Bay region consistently had higher chlorophyll concentrations, which persisted throughout austral spring and summer, compared with more northern regions of the continental shelf along the Antarctic Peninsula and the western Scotia Sea. These predictable and long-lasting phytoplankton accumulations likely provided krill with the food levels required for successful reproduction and larval survival. Unusually high krill reproduction in 2000/2001 was coincident with widespread high positive chlorophyll anomalies and resulted in a relatively large juvenile recruitment during the following spring. In general, ice edge blooms were only a significant feature in the Bellingshausen Sea and, thus, were not likely to support krill reproduction in the northern Peninsula region. Instead, phytoplankton blooms during spring in the northern region appeared to be governed by shelf break processes, such as the upwelling of iron-rich deep water. Interannual differences in sea ice conditions in Marguerite Bay also probably contributed to the variable krill abundances observed in that area. Sea ice melted early in 2000/2001, allowing elevated phytoplankton blooms to develop within Marguerite Bay. In contrast, sea ice persisted throughout spring and summer 2001/2002 preventing the accumulation of phytoplankton, particularly in southern Marguerite Bay. Thus, above average chlorophyll concentrations and favorable sea ice conditions in coastal areas during spring and summer 2000/2001 likely supported the high densities of larval krill observed during fall in waters west of the Antarctic Peninsula.

STATUS UPDATE:

09/27/07: Received final version with U.S. GLOBEC contribution number.