"Electro-fishing" in the lab: a new method to detect acute effects of heavy metals and organic pollutants in invertebrate indicator organisms.

Acute toxicity of heavy metals and organic pollutants was examined using Rhabditis oxycerca (Nematoda) and Paramecium spec. (Protozoa, Ciliata) as indicator organisms. The substances tested were based on the composition found in the river Odra. They were used in graduated dilution series (1000-fold, 500-, 250-, 167-, 125-, 100-, and 83-fold of the Odra concentration). In a special apparatus with an electric field the animals were induced to migrate from the anode to the cathode. Their migration activity (distance) and the number of migrating animals were influenced by the substances tested. To assess the extent of damage, results were compared with controls (tap water) and reference substances (aldicarb and chloracetamide). The investigations showed that heavy metal concentrations > 100-fold of the Odra concentration led to behavioural changes of both test organisms. The organic pollutants, in contrast, did not cause detectable changes in ciliates and only led to slight reductions in the migration activity of nematodes, without concentration-dependent gradations.