Top-down Trophic Cascades in Three Meromictic Lakes

Abstract

Projections of tropic cascades from a top-down model suggest that biotic characteristics of a lake can be predicted by the presence of planktivorous fish. From the same perspective, the presence of planktivorous fish can theoretically be predicted based off of the sampled biotic factors. Under such theory, the presence of planktivorous fish contributes to low zooplankton abundances, increased zooplankton predator-avoidance techniques, and subsequent growth increases of algae. Lakes without planktivorous fish would theoretically experience zooplankton population booms and subsequent decreased algae growth. These assumptions were used to describe the tropic interactions of Arco, Deming, and Josephine Lakes; three relatively similar meromictic lakes differing primarily from their absence or presence of planktivorous fish. Due to the presence of several other physical, chemical, and environmental factors that were not sampled, these assumptions did not adequately predict the relative abundances of zooplankton and algae in a lake based solely on the fish status. However, the theory did successfully predict the depth preferences of zooplankton based on the presence or absence of fish.