Changes in biotic and habitat indices in response to dam removals in Ohio

摘要

Dams on rivers modify habitat and water chemistry, resulting in degradation of fish and macroinvertebrate community integrity within and, in some cases, downstream of the dam pools. Thus, removal of a dam is usually accompanied by the expectation of improved habitat quality and biotic integrity. The Ohio Environmental Protection Agency applies a Qualitative Habitat Evaluation Index, an Index of Biotic Integrity (IBI, fishes), and an Invertebrate Community Index (ICI) to assess stream habitat quality and the habitat-dependent structural and functional integrity of the fish and invertebrate communities. Our objective was to demonstrate that these three indices reliably detect differences in the quality of habitat and fish and macroinvertebrate communities between dam pools and free-flowing reaches and that they are sensitive to changes in habitat and biotic condition following dam removal. Data from 21 stream reaches in Ohio containing dams showed that habitat and biota in dam pools possess lower quality than nearby upstream and downstream reaches. Case studies of dam removals on the Cuyahoga, Olentangy, and Sandusky Rivers confirmed that the indices are sensitive to the rapid changes in habitat and biotic communities that accompany return of dam pools to free-flowing conditions. IBI and ICI scores indicated that the former dam pools had met or exceeded the designated aquatic life use criteria within 1 yr following dam removal. We conclude that the IBI and ICI are valuable tools for measuring the rapidity and extent of changes in the fish and macro-invertebrate communities, respectively, following dam removal.