Date of Award

8-2010

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Jasmine Saros

Second Committee Member

Kevin Simon

Third Committee Member

Michael Kinnison

Abstract

Introduction and removal of strictly planktivorous fish in lakes can alter plankton communities via cascading interactions in food webs. Less is known about the large-scale and long-term effects of introduction of fish with more generalist feeding habits. Both whole-lake biomanipulation and paleolimnological approaches were used to analyze the responses of plankton communities to the introduction of white perch (Morone americana), a fish that often numerically dominates fish assemblages and switches from strict planktivory to omnivory during ontogeny. In a lake-scale removal of perch from a eutrophic lake, zooplankton body size decreased but there was no cascading effect on the algal community due to the role of "bottom-up" drivers. Paleolimnological analyses of oligotrophic lakes demonstrate an increase in cladoceran body size, inferred from fossil ephippia, and a decrease in algal production, inferred from fossil pigments, following white perch introduction. These results are counter to predictions from a top-down trophic cascade as may be expected from the introduction of strictly planktivorous fish. This study highlights the importance of trophic interactions in structuring lake food webs and the utility of combining approaches that span spatial and temporal scales to investigate complex trophic interactions in lakes.

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