Influence of 3,4-Dichloroaniline (3,4-DCA) on Benthic Invertebrates in Indoor Experimental Streams

The influence of 3,4-dichloroaniline (3,4-DCA) on benthic invertebrates has been examined. Acute toxicity tests were carried out with the following species: Pristina longiseta, Aelosoma variegatum (Oligochaeta), Hydrozetes lacustris (Acarina), Planorbarius corneus, and Gyraulus albus (Planorbidae). LC50 values (96 hr) were obtained for Pri. longiseta (2.5 mg/liter) and for Hy. lacustris (4.7 mg/liter). For all other species ranges of toxicity (maximal concentration with 0% dead to minimum concentration with 100% dead) were determined. These ranges were 0.8-20 mg/liter 3,4-DCA for Pri. longiseta, 1.6-20 mg/liter 3,4-DCA for Hy. lacustris, 10-20 mg/liter 3,4-DCA for G. albus, 50-100 mg/liter 3,4-DCA for Pl. corneus, and 10 mg/liter 3,4-DCA (maximal concentration with 0% dead; minimum concentration with 100% dead was not determined) for Ae. variegatum. In two experimental streams, the recolonization of benthic organisms into defined sample areas was studied. Therefore, a phase without chemical treatment was compared with a following exposure phase. Test concentrations were 0.2 and 1.4 mg/liter 3,4-DCA (nominal concentrations). Significant effects were the complete extinction of Pri. longiseta in 0.2 mg/liter 3,4-DCA within the first 3 weeks of exposure, as well as the reduction of immigrating individuals of another species of Pristina in both test concentrations, and of Hy. lacustris and Stentor sp. in 1.4 mg/liter 3,4-DCA. The total number of immigrated individuals was significantly reduced in 1.4 mg/liter 3,4-DCA. Diversity indices according to C. E. Shannon and W. Weaver (The Mathematical Theory of Communication. Univ. of Illinois Press, Urbana, 1949), evenness indices (E. C. Pielou, Ecological Diversity. Books on Demand, New York, 1975) and the indices of absolute variety (D. Oertel, Das Makrozoobenthos von Buhnenfeldern am mittleren Main unter besonderer Berucksichtigung der Einflusse von Stromung und Substrat. Diplomarbeit, Johannes Gutenberg-Universität, Mainz, 1987) were determined without and with 3,4-DCA treatment. Diversity and evenness were significantly decreased in 0.2 mg/liter 3,4-DCA.