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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Ecotoxicology
ROAD SALT TOXICITY STUDIES ON SELECT MICHIGAN WETLAND MACROINVERTEBRATES.
M.E. Benbow and R.W. Merritt. Department of Entomology, Michigan State University, E. Lansing, MI 48824-1115
Few studies have addressed the effects of road salt runoff on aquatic communities. As part of a study assessing these effects on mortality and production of wetland macroinvertebrates we conducted toxicity experiments designed to determine lethal road salt concentrations under a variety of test conditions. In an initial experiment, acute (96h) toxicity was determined using concentrations of 0, 500, 1000, 2500, 5000 and 10,000 mg/L on Callibaetis sp., Chaoborus sp., Hyallela sp. and Physella sp. under three test conditions: field PVC microcosms, containers adjacent to the wetland and in-door laboratory containers. In a second laboratory experiment using only Callibaetis and Physella a 18,825 mg/L concentration was added. Under all conditions, Physella had 100% mortality at 10,000 and 18,825 mg/L after 24h. Callibaetis showed a L50 of 10,000 mg/L usually after 48h depending on test condition, and 100% mortality at 18,825 mg/L after 24h; but at lower concentrations mortality was variable and growth continued. Chaoborus and Hyallela showed highly variable mortality (0 – 60%) depending on test condition and time. At concentrations < 10,000 mg/L, all taxa showed greater mortality in the microcosm and outside containers, indicating an effect of test condition on toxicity results.
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