Weight loss and net abnormalities of Hydropsyche betteni (caddisfly) larvae exposed to aqueous zinc

Abstract

AbstractCaddisfly larvae (Hydropsyche betteni) were collected near a zinc mining operation and exposed to elevated concentrations of zinc in an attempt to determine the efficacy of using weight change and capture net architecture for assessing the toxicological impact of metal exposure. One group of larvae was collected near the mine site (Adjacent) with another collected upstream and away from the mine (Remote). Weight change and capture net architecture was monitored on 400 individually identifiable larvae. The threshold‐observed‐effect concentration after 13 d was 7.6 mg/L for the Remote group and 30.2 mg/L for the Adjacent group. After 48 d, the highest test concentration of 42 mg/L resulted in a 23 and 19% loss in live‐body weight in the Remote and Adjacent groups, respectively, while control larvae from both groups gained 6% in comparison to initial pre‐exposure weights. Five weeks of exposure at 22 mg Zn/L or greater was required by both larval groups to statistically reduce the frequency of normal nets, indicating that the sensitivity of the net response was less sensitive than weight loss. Relative differences in weight changes and net architecture strongly suggest that the Adjacent larval group was slightly more tolerant than the Remote and that this increased tolerance may be related to chronic pre‐exposure to zinc prior to collection of larvae. This study demonstrates the utility of using weight loss, net architecture, and tissue burdens for assessing the impact of elevated zinc.