2023 Early Hearing Detection & Intervention Conference

March 5-7, 2023 • Cincinnati, OH

5/20/2019 | 9:45 AM - 10:00 AM | IMPACTS OF SMALL, LOW-HEAD DAMS ON STREAM MACROINVERTEBRATE ASSEMBLAGES | 151 ABC

IMPACTS OF SMALL, LOW-HEAD DAMS ON STREAM MACROINVERTEBRATE ASSEMBLAGES

Small, former mill dams are prevalent in the northeastern USA, creating abrupt discontinuities in habitat and water quality and fragmenting biotic assemblages. These dams are variable in their spatial and temporal impacts on water quality, geomorphology, and, presumably, biota. We compared macroinvertebrate assemblages within upstream reaches, dam-created impoundments, and downstream reaches at 12 dam sites across multiple years with corresponding temperature, dissolved oxygen, and habitat data. The impact of dams on stream macroinvertebrates varied among streams, with expected losses of species, reductions in biotic integrity, and increases in warmwater taxa downstream of dams evident at only a few sites. The lack of patterned responses suggests that the impacts of dams on water quality and habitat may not be sufficient to affect macroinvertebrates or that other factors obscure effects of the dams. Although impacts in stream reaches were limited, the impounded area created by dams contained a different macroinvertebrate assemblage than free-flowing stream reaches, and we have documented the loss of common stream-dwelling taxa in impoundments. An understanding of variable responses to dams and mechanisms of impact may help prioritize dam removal and set expectations for restoration.

Invertebrate
Disturbance
Restoration

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Presenters/Authors

Allison Roy (), U.S. Geological Survey, Massachusetts Cooperative Fish and Wildlife Research Unit, University of Massachusetts Amherst, aroy@eco.umass.edu;