Luecke, C. Utah State University, luecke@cc.usu.edu
Budy, P. US Fish and Wildlife Service, Phaedra_budy@mail.fws.org

 
UNDERSTANDING PATTERNS OF TROPHIC TRANSFER EFFICIENCY USING MESOCOSMS IN LAKES OF VARYING TROPHIC STATUS
 
We employed mesocosms in lakes of three trophic states to assess the degree of trophic transfer from phytoplankton to planktivorous fish. Fish density had a large effect on trophic transfer in lakes of both oligotrophic and eutrophic status. Nutrient additions had significant effects on the biomass of higher trophic levels only when fish densities were low. At high fish densities, zooplankton biomass remained extremely low allowing phytoplankton biomass to increase in the presence of enhanced nutrient conditions. High densities of planktivorous fish resulted in a bottleneck of trophic transfer such that the phytoplantkon response to nutrient increases did not result in increases in zooplankton biomass or fish growth. These experimental results confirm the patterns reported in Hairston and Hairston's review of trophic-level dynamics indicating that trophic structure determines ecological efficiency in lake ecosystems.
 
Day: Thursday, Feb. 4
Time: 11:30 - 11:45am
Location: Eldorado Hotel
 
Code: SS51TH1130E