Decline in the Diversity of Benthic Invertebrates in the Wave-zone of Eastern Lake Erie, 1974–2001

Abstract

In May 2001, we revisited seven sites in the wave-zone of the north shore of the eastern basin of Lake Erie that had been sampled in 1974/75 by Barton and Hynes. Qualitative collections of benthic invertebrates were made using the same methods in both surveys. Total diversity dropped from 122 taxa in 1974/75 to 83 in 2001. The most substantial changes were the disappearance of formerly abundant Ephemeroptera, Trichoptera, and other insects, and the appearance of Dreissena bugensis and Echinogammarus ischnus. No Dreissena polymorpha was found but D. bugensis occurred at every site in 2001, accounting for 19.5% of the animals collected. Amphipoda were numerically dominant in both years: the relative abundances of E. ischnus and Gammarus fasciatus together were similar to that of G. fasciatus alone in 1974/75. Gastropoda were relatively more important in 2001. The reduced biodiversity in the fauna of the wave-zone of eastern Lake Erie appears to have been caused primarily by the establishment of dreissenid mussels.