Consumer distribution and diversity affects prairie stream ecosystem properties

Algae and macroinvertebrate properties are influenced by numerous factors, including structure and richness of stream fish assemblages. We used experimental streams located on Konza Prairie Biological Station to test the effects of fish assemblage composition on ecosystem properties. We hypothesized that effects of fishes would diminish with assemblage richness and no up-to-down stream effects would be evident. Each experimental unit included 3 riffles and 3 pools and was replicated three times across 4 treatments; 3 community treatments of increasing diversity and 1 no fish control.  Samples were taken from multiple locations within each pool and riffle to quantify magnitude and heterogeneity of algal and macroinvertebrate structure. Fish distribution was quantified, and differed with richness where fishes concentrated in downstream pools as richness increased. The presence of a dominant grazer kept benthic algal filament lengths short, whereas control streams became overgrown with floating algal mats. This shift from benthic to floating algae diminished as assemblage richness increased.