Acute and chronic toxicity of copper and chromium to the freshwater calanoid copeppod Notodiaptomus conifer (SARS).

Abstract

Recent studies have shown that the lower basin of the Salado River is highly polluted with copper and chromium. In order to evaluate the effect of those metals on Notodiaptomus conifer, a representative calanoid copepod, we carried out two (acute and chronic) experimental assays. In the first one, the 24 and 48 h EC50 values were determined to nauplii and adults. Chronic assays were conducted to evaluate time of development for nauplii, time of development for each copepodite stages, total development time, growth, number of ovigerous females, fecundity and time required to produce the first egg sac. Additionally, the effect of those metals on the equiproportional model proposed for copepods was evaluated. Acute experiments reveled that juvenils were more sensible than adults. Although growth was not seriously affected by metal exposition, development time was delayed and reproductive variables were altered with the increase of metal concentrations. The deviation from the equiproportional model proposed for copepods proved to be a useful parameter to provide relevant information on toxicity of both metals along development time. In comparison with other zooplanktonic species, the highest sensitivity of N. conifer to copper and chromium makes it a suitable bioindicator in ecotoxicological tests.