This study will evaluate the ability of metalimnetic phytoplankton to mitigate the effects on intergrated water column primary productivity of changes in piscivory. It is hypothesized that increased planktivory will lead to reduced grazing, increased epilimnetic chlorophyll, reduced transparency, and elimination of metalimnetic algae, thereby shifting the locus of production to the epilimnion with little change in total primary production. This mechanism could substantially alter the effects of cascading trophic interactions in lakes which support deep chlorophyll maxima. The hypothesis will be tested with a whole- lake planktivore addition experiment. Both experimental and control lakes presently support dense metalimnetic algal populations. Biomass budgets derived from this sampling and epilimnetic budgets derived from another project will be used to analyze the qualitative and quantitative effects of changes in planktivory within metalimnetic and epilimnetic algal populations, and the implications of those changes to total primary productivity.
