Test chambers and test procedures for in situ toxicity testing with zooplankton

Ecotoxicity assessment is usually done by classical tests under controlled conditions. However, field situations may not be accurately predicted by la boratory testing. In situ testing is a pertinent way for assessing the ecol ogical relevance of laboratory bioassays. The objectives of this study were to develop an in situ test chamber and respective test protocols suitable for ecotoxicity testing with zooplankton and to evaluate the use of laborat ory protocols (water column and solid phase) by comparing results obtained under controlled conditions with in situ results at an aquatic system recei ving acid mine drainage. At the most contaminated stations and at the refer ence stations, good agreement was found between in situ and classical testi ng. At intermediate stations, in situ toxicity was generally higher than th at in classical tests. Sample collection and preservation probably altered actual toxicity, thus emphasizing the need for caution in estimating or ext rapolating field effects from laboratory results.