CS35 Trophic Dynamics
Date: Friday, June 14, 2002
Time: 10:30:00 AM
Location: Carson A
 
BurkartGA, Utah State University, Logan, USA, greta@cc.usu.edu
Luecke, C, , Utah State University, Logan, , luecke@cnr.usu.edu
Gross, D, , Utah State University, Logan, USA, donovan@cc.usu.edu
 
ZOOPLANKTON GRAZING PATTERNS IN LAKES WITH AND WITHOUT FISH: VARIATION DUE TO PHYTOPLANKTON EDIBILITY AND ZOOPLANKTON TAXA
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The presence of fish can alter biomass and composition of zooplankton communities, which, in turn can affect energy flow from phytoplankton to zooplankton. In 2000 and 2001, we analyzed seasonal differences in zooplankton biomass, community composition and grazing rates in Arctic lakes with and without fish. Over both summers, mean zooplankton biomass in the fishless lake was 4 times higher than biomass in the lake with fish; however, community grazing rates in the fishless lake were only 2 times higher than rates in the lake with fish. To investigate the discrepancy between zooplankton biomass and grazing rates, we performed community level grazing experiments in which zooplankton from the fishless lake grazed on phytoplankton from the lake with fish and vice versa. This experiment suggested that the zooplankton community from the fishless lake may graze at a higher rate on phytoplankton from the lake with fish. Furthermore, Diaptomus gracilis grazing rates per unit biomass were significantly higher in the fishless lake. These findings suggest that the discrepancy between zooplankton grazing rates and biomasses are related to differences in edibility of phytoplankton.