Macroinvertebrate communities and water quality upstream and downstream of Castor canadensis dams of various ages.

Abstract

Beaver dams greatly alter stream ecosystems and the surrounding environment. This study aims to assess the effect of beaver dams of various ages on water quality and macroinvertebrate communities. Five beaver dams were located on Carp Creek and Maple River in Pellston, Michigan and classified according to their state of preservation, which roughly reflects dam age. At each dam, we took macroinvertebrate samples, dissolved oxygen (DO), flow, and substrate type measurements from four places both upstream and downstream from the dam. Water quality samples (total P, total N, conductivity, turbidity, and pH) were taken at two areas both upstream and downstream from the dam. We used the Shannon-Weiner Index and Sorensen’s Index along with SPSS to statistically analyze differences in macroinvertebrate densities and numbers. Water quality samples, flow, and DO were also analyzed.None of the water quality measures attained statistical significance. There was significantly more macroinvertebrate diversity downstream than upstream for two dams on Carp Creek (p<0.05). When macroinvertebrate data for all dams were grouped together, it was again found that there was significantly more diversity downstream (p<0.05). We observed that as dam class (i.e. age) increased, upstream and downstream macroinvertebrates trended towards becoming more similar.