Effects of Algae-Grazing Fishes on Biotic Communities and Ecosystem Processes in North Temperate Streams

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This project builds on three years of investigation on the effects of grazer-algae interactions and predator-grazer-algae interactions in north temperate streams to ask fundamental questions about the influence of grazing fishes (Campostoma) on biotic communities and ecosystem-level processes or rates in stream systems. The previous research demonstrated a link between predatory fishes that influenced distributions of the algae-grazing minnows, which in turn has strong effects on disribution and kinds of attached algae. The previous research also suggested that grazing by Campostoma could have a direct influence upon the taxa of algae that dominated Ozark stream substrates, maintaining a "lawn" of primary productivity, and changes in kinds of algae could influence phenomena such as nitrogen fixation, C:N ratios, or bacterial flora. This research tests, through a combination of laboratory and field manipulations, the hypothesis that grazing fishes have prevasive effects throughout the structure and function of temperate stream ecosystems. Fish have largely been overlooked as grazers in north temperate streams. The present study will use laboratory stream comparisons of Campostoma to a variety of invertebrate taxa with regard to strength of grazing effects upon system phenomena.