The impact of stream obstructions on the aquatic invertebrate community: implications for stream management.

Abstract

We investigated the impact of obstructions on the diversity of aquatic invertebrate organisms in Carp Creek in order to examine the implications of stream management. The impact of obstructions throughout the creek increase the range of substrate availability and the range of water velocity. Velocity is a mechanism through which the presence of logs impact the diversity of benthic organisms. We asked the following questions: does the presence of obstructions influence species diversity, species richness, and the absolute abundance of aquatic invertebrate organisms in Carp Creek? We sampled 15 sites that were equally divided between three locations (the head, middle, and mouth). In experiment one, we sampled sediment-dwelling organisms. In the process of sampling plots in experiment one, we observed a substantial number of organisms on the log. In experiment two, we sampled an additional 12 sites which allowed us to examine sediment and log-dwelling organisms. In experiment one, we found that the presence of obstructions did not increase species richness or abundance, but did increase species diversity. For experiment two, the presence of logs increased species richness and abundance of aquatic invertebrate organisms, but it did not increase species diversity, which suggest that there is a trade off between species richness and species evenness. We can not determine from the data gathered the impact of the removal of obstructions. However, we, as stream managers suggest that the presence of the most deteriorated logs benefit the aquatic invertebrate community in the creek.