Temporal Variation in Ohio River Macroinvertebrates: A Historical Comparison of Rock Basket Sampling (1965–1971 and 2002)

ABSTRACT

The United States Environmental Protection Agency (USEPA) used rock basket artificial substrates to sample benthic macroinvertebrates of the Ohio River from 1965 to 1971. The objective of this study was to evaluate changes in the benthic assemblage and to assess health of the community since passage of the 1972 Clean Water Act (CWA). Rock baskets of the same configuration were placed in the vicinity of the historic locations and were allowed to colonize for the same six-week period in summer 2002. Macroinvertebrates collected from 2002 baskets were compared to those of historic samples by using non-metric multidimensional scaling, by employing proportional indices of community similarity, and by comparing commonly used macroinvertebrate metrics. Analyses were generally performed at the genus (insects) or order (non-insect) level to minimize taxonomic discrepancies between time periods. A total of 62 taxa groups was identified across all years, with midges and oligochaetes generally dominating. Only 10–16 taxa groups accounted for >93% of all individuals in each year, but taxa contributions varied greatly among years. The 2002 benthic assemblage was distinct from earlier years, with increases in total taxa richness and Ephemeroptera, Plecoptera, and Trichoptera taxa, and with a decline in the number of oligochaetes. Differences in 2002 data are partially attributed to a replacement of the amphipod Crangonyx sp. by Gammarus sp. and the invasion of the zebra mussel (Dreissena polymorpha) during the late 1980s. Our findings indicate the Ohio River benthic community today is markedly different from that of the 1960s and has shown general improvement since passage of the 1972 CWA.