CS34 River Dynamics
Date: Wednesday, June 12, 2002
Time: 4:30:00 PM
Location: View Royal
SlussTD, Center for Watershed Research, Department of Biology, University of Louisville, Louisville, USA, tamarasluss@yahoo.com
Jack, J, , Center for Watershed Research, Department of Biology, University of Louisville, Louisville, USA, jeff.jack@louisville.edu
Zooplankton may play a vital role in the Ohio River ecosystem by grazing and their impacts on nutrient cycling and carbon processing. We assessed the relationship between discharge and zooplankton population growth rates in a 110 kilometer reach of the Ohio River. Zooplankton were collected at four longitudinal sites every three weeks from March to September in a semi-Lagrangian manner. Zooplankton abundance and estimated flux, a ratio of individual abundance inputs to the output of the study reach, were calculated to determine whether the Ohio River acts as a source or a sink of zooplankton groups. When the river experienced long transit times (during periods of low discharge) then zooplankton population densities, specifically Bosmina, Daphnia, Calanoids, Brachionus, and Keratella increased within the reach. Zooplankton community densities were positively correlated with chlorophyll a and negatively with river transit times. Evidence of light limitation was observed; at the site below the tributary, light intensity was positively correlated with total zooplankton abundance and diversity. These physical factors may influence energy transfer, nutrient cycling, and carbon processing in the river by affecting zooplankton densities.