Swimmers Itch Control - Effect on Water Quality

Abstract

Copper sulfate (CuSO4) has been applied annually since 1944 to as much as 3% of the surface area of Houghton L§ke to control the snail vectors of "swimmers' itch" (schistosome dermatitis). To investigate the effects and fate of the approximately one million pounds of copper which have been applied to Houghton Lake, water, sediments, aquatic macroinvertebrates and fish were analyzed for copper. Dissolved copper in lake water was below detectable limits (<0.01 mg/1), while total coppper associated with particulate matter in lake water ranged from 0.02 to 0.75 mg/1. Copper content of lake sediments ranged from 1.4 to 254.9 nig/kg dry weight. Higher concentrations were generally found associated with sediment which had large organic fractions. The highest concentration found in sediments from areas which were treated annually with copper sulfate was 35.3 mg/kg copper (dry weight). Copper content of macroinvertebrates (Ephemera simulans, El 1iptio dilatatus and Orconectes s p .) ranged from 3.0 to 48.0 mg/kg wet weight. Ephemera simulans was the only macroinvertebrate which showed a significant relationship between its body copper content and the copper content of associated sediments. Average copper concentrations of bottom feeding fish, panfish and predatory fish were 1.7, 0.6, and 0.4 mg/kg wet weight, respectively. Copper concentrations in warmwater fishes from Michigan background water quality stations ranged from 0.2 to 0.7 mg/kg. Copper was not found to be accumulating in the sandy sediments of treatment areas, but was being transported by suspended organic particulates to the organic sediments in deeper areas of the lake. Wave action appears to be the major cause of copper mobilization within Houghton Lake. Laboratory tests showed that the organic sediments of Houghton Lake had the capability of adsorbing up to 8,700 mg/kg copper (dry weight) before an amount toxic to aquatic life appeared in overlying water