Biological effects of kepone and mirex in freshwater invertebrates.

Acute and chronic toxicity studies of Kepone (chlordecone) and mirex were conducted with daphnids (Daphnia magna), amphipods (Gammarus pseudolimnaeus), and larvae of a midge (Chironomus plumosus). Acute toxicities of Kepone ranged from a 48-hr EC50 of 350 microgram/L for midges to a 96-hr LC50 of 180 microgram/L for amphipods, whereas the acute toxicities of mirex to all three taxa exceeded 1000 microgram/L. Maximum acceptable toxicant concentrations (MATC's) for Kepone and mirex were estimated by measuring reproduction of daphnids, growth of amphipods, emergence of midges, and survival of all organisms. MATC for Kepone was estimated to be between 9 and 18 microgram/L for daphnids, between 1 and 2 microgram/L for amphipods, and between 8.4 and 18 microgram/L for midges; MATC for mirex exceeded 34 microgram/L for daphnids and midges, but less than 2.4 microgram/L for amphipods. The concentration of Kepone and mirex accumulated by daphnids was 760 and 8025 times, respectively, the concentration in water. Estimated times for elimination of 50% of the residues by daphnids were 141 hr for Kepone and 12 hr for mirex.