Benthic Macroinvertebrates

Monitoring efforts from 1991 through 1998 showed evidence of only subtle impacts to the benthic macroinvertebrate communities of Big Bayou and Little Bayou creeks potentially associated with PGDP operations or effluent discharges.

The taxonomic richness of pollution intolerant taxa (EPT taxa) downstream of PGDP and in reference sites (BBK 12.5 and MAK 13.8) are generally comparable (Figure 1).
However, unusually high total densities and densities of mayflies on some sample dates (Figure 1) suggest subtle impacts from factors such as nutrient enrichment.
In general, the benthic macroinvertebrate communities of sites downstream of the PGDP have remained in a "steady state" since 1991, thus, indicating that major changes have not occurred in the water quality of the streams during the 1991-1998 period.

Figure 1. Means for total density and total taxonomic richness of mayflies (Ephemeroptera) in Big Bayou Creek, Little Bayou Creek, and Massac Creek in Paducah, Kentucky, September 1991 - March 1997. BBK = Big Bayou Creek kilometer; LUK = Little Bayou Creek kilometer; MAK = Massac Creek kilometer.

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Last Modified: April 17, 2001