Ecological characterization of streams, and fish-tissue analysis for mercury and lead at selected locations, Fort Gordon, Georgia, June 1999 to May 2000

Abstract

The U.S. Geological Survey, in cooperation with the Environmental and Natural Resources Management Office of the U.S. Army Signal Center and Fort Gordon, Ga., documented the ecological condition of selected water-bodies on the Fort Gordon military installation from June 1999 to May 2000. This study includes stream-habitat assessments, aquatic invertebrate and fish-community surveys in selected stream reaches, and analyses of mercury and lead concentrations in largemouth bass (Micropterous salmoides) muscle tissue from three impoundments. Assessment surveys indicate lower habitat value scores in some streams draining the more developed areas on Fort Gordon. A small tributary to Butler Creek--which drains parking lots associated with military motor pools and other impervious surfaces--is characterized by moderate levels of bank erosion and excess sediment in the stream channel compared to reference sites. Four other stream reaches are more similar to reference streams in respect to habitat conditions. Invertebrate communities in streams draining these urbanized watersheds are inhabited by 13 to 16 taxa per reach; whereas, 23 and 33 taxa were collected from the two reference stream reaches. Measures of invertebrate abundance, taxa richness, Ephemeroptera, Plecoptera, and Tricoptera Index are lower in streams draining urbanized watersheds. Measures of community similarity also indicate differences between streams draining urbanized areas and reference streams. Streams draining developed areas on Fort Gordon are inhabited by 3 to 10 fish species and included more species regarded as tolerant of degraded water-quality conditions; whereas, the two reference stream reaches support 4 and 10 species, respectively, including one species considered intolerant of degraded water-quality conditions. Mercury was detected in all largemouth bass collected from three impoundments on Fort Gordon. Wet-weight mercury concentrations in fish tissue analyzed from all sites range from 0.08 micrograms per gram to 1.33 micrograms per gram. Median mercury concentrations in fish tissue are 0.83 micrograms per gram at Soil Erosion Lake, 0.72 micrograms per gram at Lower Leitner Lake, and 0.22 micrograms per gram at Gordon Lake. Median mercury concentrations in fish tissue analyzed from Soil Erosion Lake and Lower Leitner Lake are more than two times higher than U.S. Environmental Protection Agency recommendation of 0.3 micrograms per gram for fish consumption. Lead concentrations are below the minimum reporting limit for all specimens analyzed from reservoirs sampled at Fort Gordon.