CS39A Zooplankton - Feeding, Reproduction, Growth and Molecular Diversity
Date: Tuesday, June 11, 2002
Time: 11:00:00 AM
Location: View Royal
 
SchampelJH, Arizona State University, Tempe, USA, john.schampel@asu.edu
Schulz, K, L, S.U.N.Y.-Syracuse, Syracuse, USA, 
Sterner, R, W, University of Minnesota, St. Paul, USA, 
 
EXPLAINING POSITIVE SLOPES IN DILUTION GRAZING STUDIES: OBSERVATIONS FROM LAKE SUPERIOR
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We used the dilution grazing technique (Landry and Hassett 1982) to estimate grazing rates in Lake Superior and obtained results (positive slopes) not interpretable in light of any known published studies. We constructed a model of the dilution method, and our findings highlight three important issues. First, density-dependent losses to grazers via predation can generate nonlinearities in relationships between dilution and prey apparent growth rate (a.g.r.) similar to saturated feeding kinetics. Second, grazer mortality via predation can generate positive relationships between dilution and prey a.g.r. Third, both of these relationships change with incubation duration. When we parameterized this model with values measured in Lake Superior, it generated relationships very consistent with our observed grazing results.