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EAST GALLATIN RIVER, MONTANA: MACROINVERTEBRATE DISTRIBUTION AND WATER ANALYSIS 1973-1974
Citation:
Luedtke, R., R. Russo, AND R. Thurston. EAST GALLATIN RIVER, MONTANA: MACROINVERTEBRATE DISTRIBUTION AND WATER ANALYSIS 1973-1974. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-76/106.
Description:
Macroinvertebrate samples from seven stations and water chemistry samples from 10 stations in the East Gallatin River, Montana, were collected on thirteen dates throughout the year between June 1973 and August 1974. The stations were selected to cover a stretch of the river both above and below the City of Bozeman sewage treatment plant. Marked changes in the macroinvertebrate populations were observed in the region immediately downstream from the sewage outfall. Recovery, in terms of increasing numbers of species and total numbers of clean-water forms and decreasing numbers of tolerant forms, appeared to be complete with 15-20 km below the outfall. Several species diversity indices were calculated but failed to be illustrative of the observed changes in the benthic insect community. Concentrations of a number of the chemical species measured showed a marked increase immediately below the sewage outfall; NH3-N and PO4-P showed the greatest increase (five- to seven-fold). These higher concentrations gradually diminished until at approx. 50 km downstream they were comparable to levels above the sewage outfall. With the exception of NO2-N, none of the variables measured reached concentrations generally considered to be acutely toxic to fishes or aquatic macroinvertebrates.