Bersano, J. JG. Texas A&M University, jbersano@utmsi.utmsi.utexas.edu
Buskey, E. JG. University of Texas at Austin, buskey@utmsi.utexas.edu
Lavrentyev, P. P. University of Akron, 330-972-8445

 
FIELD OBSERVATIONS ON THE FEEDING OF Acartia tonsa (CRUSTACEA: COPEPODA) IN TEXAS BROWN TIDE WATERS
 
Blooms of Aureoumbra lagunensis, a small phytoplankton species known as the Texas brown tide, have been occurring in south Texas for over eight years. The reasons for the persistence of this species in Laguna Madre and adjacent areas are still unknown. Previous researchers suggested that removal of microzooplanktonic grazers by copepod predation would be an important mechanism, due to the absence of adequate sized phytoplankton. Between July 1997 and July 1998, five field studies were carried out in Baffin Bay and Corpus Christi Bay. Grazing impacts of the copepod Acartia tonsa on natural phytoplankton and microzooplankton assemblages, were assessed by incubation experiments. Selective feeding was observed for different chlorophyll fractions and distinct microzooplankton groups. In some occasions A. tonsa grazed down chlorophyll fractions > 10 um while low grazing was observed for fractions between 2-10 um. Feeding on ciliates and flagellates varied for different areas and cruises. Sometimes A. tonsa selected for flagellates and sometimes for ciliates. The results show some indications of cascade effects, corroborating the idea that copepod predation on microzooplankton could alleviate grazing pressure on A. lagunenis and other phytoplankton groups < 10 um.
 
Day: Friday, Feb. 5
Time: 02:45 - 03:00pm
Location: Eldorado Hotel
 
Code: SS42FR0245E