Fate and effects of 3,4‐dichloroaniline in the laboratory and in outdoor ponds: II. chronic toxicity to Daphnia SPP. and other invertebrates

Abstract

AbstractThe effects of 3,4,‐dichloroaniline (DCA) on survival, growth and reproduction of the planktonic crustacean Daphnia magna were evaluated in the laboratory using a procedure based on Organization for Economic Cooperation and Development guidelines. Effects on reproduction, the most sensitive of the measured biological responses, occurred at a concentration of 20 μg/L but not at 10 μg/L or at lower concentrations. These, and similar results reported elsewhere, were used to calculate the maximum acceptable toxicant concentration (MATC) for D. magna.In acute toxicity tests with D. magna and D. longispina the 48‐h EC50 values were 290 and 440 μg/L, respectively. An estimate of the MATC for D. longispina was then obtained by multiplication of the MATC for D. magna by the ratio of the 48‐h EC50 values for the two species.A field experiment was carried out to compare the chronic toxicity of DCA in the laboratory with effects on populations of zooplankton and communities of macroinvertebrates in outdoor ponds. Three ponds were treated with DCA at a nominal concentration of 45 μg/L and three at 450 μg/L. These concentrations were maintained in the water for 28 d. Three untreated ponds were used as controls. Population densities of the dominant species of zooplankton were monitored before, during and after treatment with DCA. Samples of the macroinvertebrate communities were taken immediately after the end of treatment. Birth, death and growth rates of D. longispina populations were monitored using Perspex cylinders to confine samples of adults in situ for periods of 24 h.Population densities of D. longispina were significantly affected (p ≤ 0.05) by both treatment levels. There were no adverse effects on the population densities of two species of copepods and no changes were observed in the structure of macroinvertebrate communities. It was concluded that the Cladocera were much more susceptible to DCA than were other groups of invertebrates in the outdoor ponds.Birth and growth rates of D. longispina populations were highly sensitive to the effects of DCA. They were depressed when concentrations of DCA were maintained at a level greater than the MATC and increased rapidly when concentrations decreased below this level. Thus, the MATC, derived from the results of toxicity tests, provided an accurate estimate of threshold concentrations affecting field populations of D. longispina.