An investigation of fish community and water quality compositions in an isolated side channel of the upper Mississippi River

Abstract

Varying degrees of connectivity between side channels and the main river channel are vital for sustainable ecological processes and functions for both aquatic and terrestrial communities. Within the Mississippi River, restoring side channel functional diversity is a top priority for many natural resource agencies. Buffalo Chute, located at river kilometer 41, is one of the several side channels, island complexes that becomes isolated from the main channel during low river stages leading to thermal and chemical stratifications and anoxic conditions. The purpose of this study was to better understand the impacts of side-channel isolation in the middle Mississippi River (MMR) by measuring fish community and water quality characteristics within an isolated waterbody. Therefore, we selected Buffalo Chute a representative side channel of the MMR to document water quality and fish community characteristics. Water quality measurements were summarized for the 2-year study. Thermal and chemical stratifications coupled with high water temperatures and anoxic conditions were observed in both years during summer. Oxygen reduction potential was lower in summer than winter, which could be attributed to excessive growth of microorganisms and increased biological oxygen demand. Specific conductivity, total phosphorus, total nitrogen, and chlorophyll a were higher in summer compared to winter. Differences in water quality characteristics may have resulted in lower mean fish species richness, diversity, and evenness observed during the following winter. We surveyed 45 sites over 2 years using multiple gears to assess fish assemblage characteristics. The data collected in Buffalo Chute provide some insight into how isolated side channels function during low flow periods. © 2012 Taylor & Francis.