The development of toxicity tests for freshwater pollutants and their validation in stream and pond mesocosms

The number and variety of Freshwater species and bioassay procedures curren tly recommended in European Directives for assessing the risk posed by poll utants to freshwater ecosystems is rather limited. The aim of the three con secutive European Commission-sponsored programmes described here was to mod ify or develop new laboratory methods that could be used for evaluating tox icity to freshwater species and which would be suitable for incorporation i nto the current "notification scheme" for new substances. An essential phas e of each project was a validation process in which results of laboratory t ests were compared with values obtained in the field using structural and f unctional responses of communities. The laboratory tests were developed by Fraunhofer-Institut fur Umweltchemie und Okotoxikologie (FhG) Potsdam-Rehbr ucke with algae, protozoa and a variety of in vitro cellular/subcellular pr eparations; by the Stare University of Ghent with water column invertebrate s, and by Cardiff University with benthic invertebrates. The laboratory tes ts included in vitro procedures, conventional whole organism single species tests, simple multi-species systems and microcosms. The field validation w as carried out by Shell Research Sittingbourne employing artificial streams and by FhG Schmallenberg and GSF-Forschungszentrum fur Umwelt und Gesundhe it, Munich with artificial ponds and included single species responses but also structural and functional community responses. The same reference chem icals: lindane, copper, 3,4-dichloroaniline and atrazine were used by all l aboratories. A comparison of the most sensitive toxicity response determine d for each reference chemical using the laboratory toxicity tests, with tha t determined by the field simulation procedures revealed that for the refer ence chemicals lindane, copper and atrazine, adverse effects were not detec ted either for single organisms or for structural and functional characteri stics of the community or ecosystem, at concentrations below those identifi ed in the laboratory toxicity tests. In the case of dichloroaniline, howeve r, effects on the population dynamics of one species in the pond mesocosm w ere recorded at a concentration x16 below that reported in the laboratory. We conclude that appropriately designed, relatively simple and inexpensive laboratory toxicity tests with a selection of test species are generally ad equate, with small application factors, for predicting the environmental ri sk of polluting chemicals to freshwater ecosystems. (C) 2000 Elsevier Scien ce Ltd. All rights reserved.