Lougee, L. A. Romberg Tiburon Center for Environmental Studies and San Francisco State University Biology Department, llougee@sfsu.edu
Bollens, S. A. Romberg Tiburon Center for Environmental Studies and San Francisco State University Biology Department, sbollens@sfsu.edu
Avent, S. R. Romberg Tiburon Center for Environmental Studies and San Francisco State University Biology Department, sravent@sfsu.edu

 
BEHAVIORAL RESPONSE AND TOLERANCE OF THREE ESTUARINE COPEPOD SPECIES TO HALOCLINES
 
San Francisco Bay, like many estuaries, undergoes drastic changes in salinity over time scales ranging from hours to years and spatial scales from cm to km. Zooplankton, many of which exhibit vertical migration behavior, often confront these changes in the form of haloclines. An attempt to understand if, how, and why zooplankton respond to haloclines was made using three bay copepods, Acartia (Acartiura) sp., Tortanus dextrilobatus, and Acartia californiensis in a controlled laboratory setting. Experiments involved placing 20 - 30 adult female copepods of a single species in a two-meter high tank containing a halocline and a duplicate tank without a halocline. The location of each organism was recorded once every hour for one to three days using an automated video microscopy system. In some instances food and predators were experimentally manipulated. Results indicate the vertical migration pattern of each species changed radically in response to haloclines of only 5 PSU-salinity difference. Additional experiments indicated these changes were not associated with any salinity induced mortality per se, although more subtle affects of physiological stress can not be ruled out. The relative importance of position maintenance, feeding, and predation in estuarine zooplankton migration will be discussed in light of these results.
 
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
 
Code: SS04TH1139S