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(19-32) Ecotoxicological sensitivity of groundwater organisms. Schaefers, Christoph*,1, Egert, Edgar2, Stein, Bernd3, 1 Fraunhofer IME, 57377 Schmallenberg, Germany2 Universität Oldenburg, 26111 Oldenburg, Germany3 Umweltbundesamt, 14191 Berlin, Germany ABSTRACT- The sensitivities of groundwater organisms to three pesticides were investigated in lethality tests and compared with those of taxonomic relatives from surface waters. As crustaceans represent the most important groundwater taxa, copepod and amphipod species were selected as well as Syncarida, a group only present in groundwater. The specimen were taken from groundwater bodies, and tested at about 10 0C in the dark. Breeding or chronic test performance were not possible because of the life performances being retarded by a factor of 5-10 compared with surface water organisms. The pesticides were selected according to their toxicity to crustaceans, to the availability of comparative data sets and mainly to the differences of modes of action: the fungicide Cyprodinil inhibits anabolism, the pyrethroid lambda-Cyhalothrin is extremely neurotoxic, and the herbicide Bromoxynil-Octanoat is mainly cytotoxic due to the non-polar narcotic action of the Octanoat. The sensitivity distribution of lethal toxicity to groundwater species can be represented by taxonomically and physiologically comparable species of surface waters. Inhibition of the anabolism or the activity affect groundwater organisms less or clearly retarded as compared to surface water organisms. No indications for a physiologically higher sensitivity of groundwater organisms could be observed. Risk assessment based on standard organisms seems to be sufficiently protective also for groundwater communities at the actual state of knowledge. If there are concerns about potential effects to higher crustaceans, a representative species (e.g. Gammarus, Asellus, Hyalella) should be tested in order to be protective regarding the shallow norm of reaction of Syncarida (as shown with lambda-Cyhalothrin). The population dynamics of groundwater species allows only very slow and insufficient recovery, in terms of reproduction as well as of migration. Key words: species sensitivity, groundwater, pesticides, crustaceans |
