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Notes: Abstract The effects of lindane on the hatching, survival and development ofChironomus riparius Meigen were investigated over a complete life-cycle. Pupation and adult emergence were identified as the criteria most sensitive to lindane. The no-observed-effect-concentration (NOEL) and lowest-observed-effect-concentration (LOEC) of lindane to the life-cycle of C. riparius were determined as 1.1 and 9.9 μg/L, respectively. The results are discussed with respect to previous toxicity data and the potential role of life-cycle toxicity tests in hazard evaluation.

Notes: Abstract. Acute and sublethal toxicity of the organochlorine insecticide lindane to the amphipod crustacean Hyalella azteca was investigated. Acute experiments were conducted for a maximum test exposure period of 240 h with adult and neonate H. azteca. Median lethal concentrations (LC50s) determined for adult Hyalella included a 48-h LC50 of 47.6 μg/L and 240-h LC50 of 26.9 μg/L. For neonate H. azteca 24-, 48-, and 240-h LC50s were 29.5, 14.8, and 9.8 μg lindane/L, respectively. Neonate H. azteca were approximately three times more sensitive than adults. Two sublethal toxicity bioassays were developed based on the direct and indirect disruption of the precopulatory or mate guarding behavior of Hyalella. This reproductive behavior is readily quantifiable and of ecological significance as it is a vital component of the mating success of the species. The direct disruption bioassay examined the separation of precopulatory pairs maintained in control water and a range of lindane concentrations during a 24-h exposure period. Median separation times (ST50s) were determined and the LOEC was 24.4 μg lindane/L. The indirect disruption bioassay consisted of a test exposure period of just 4 h after which an invertebrate anesthetic solution was administered to induce separation of precopulatory pairs. The LOEC was 17.3 μg lindane/L, suggesting that the indirect precopulatory separation bioassay was comparable to the 24-h direct separation study. Both bioassays are rapid, relatively simple to perform, and have yielded effect concentrations that correspond with LC50 values determined using adult and neonate H. azteca life stages over more prolonged lindane exposures. Following some modification, these behavioral bioassays may be suitable for use in the hazard evaluation of sediments and for deployment as in situ toxicity tests.

Notes: Abstract Laboratory tests were developed to allow identification of the effects of toxicants on the predator-prey interaction between Hydra oligactis Pallas and Daphnia magna Strauss. Three test methods, which differed with respect to initial Daphnia population, test period, and management of predation level, were used to determine the influence of the organochlorine insecticide lindane on the interaction. The criteria examined were the population structures of the two species. The lindane treatments did not alter the production of Hydra. However, the final population structure of Daphnia was variously affected by the toxicant in the different test systems. The most sensitive endpoint, with a lowest observed effect concentration of 4 μg/L lindane determined after a 14 day exposure period, was increased recruitment of juvenile Daphnia in a test system which incorporated management of the Hydra. The results are compared to previously reported data derived from single species chronic tests, and the suitability of the test methods for hazard evaluation is discussed.

Notes: Abstract. The feeding response of juvenile amphipod Gammarus pulex (L.) was investigated following exposure to freshwater pollutants. The method employed is nondestructive, provides a rapid indication of the status of groups of individuals, and is based on a time-response analysis of the consumption of the eggs of Artemia salina and the determination of median feeding times or FT50s. The feeding activity of juvenile G. pulex was found to be a sensitive response criterion for use in assessing the sublethal toxicity of copper, lindane, and 3,4-dichloroaniline (3,4-DCA). Reductions in gammarid feeding activity were identified following 96 hours exposure at 12.1 μg/L copper or 8.4 μg/L lindane and 240 hours exposure at 918 μg/L 3,4-DCA. However, a significant increase was observed in the feeding rate of gammarids that had been exposed for 240 h at 0.09 μg/L lindane in comparison with control values. The increase in feeding rate may be interpreted as a possible stimulatory effect associated with the toxicant action of lindane. Increases in gammarid feeding activity were not determined during the experiments conducted with either copper or 3,4-DCA. A sustained reduction in G. pulex feeding rates may cause growth inhibition and impaired reproduction which have previously been identified as sublethal responses of other freshwater organisms exposed to comparable concentrations of lindane, 3,4-DCA, or copper. The feeding bioassay was also used as a tool in an investigation of species interactions in toxicant systems. The feeding responses of G. pulex, which had been maintained in the presence of Asellus aquaticus (as interacting pairs) and exposed to a range of concentrations of lindane or 3,4-DCA, were recorded and compared. The findings illustrate the complex nature of test systems that integrate the stresses of toxicant and competition. In the lindane test system a reduction in gammarid feeding activity was observed following a 96-h exposure with A. aquaticus at 3.8 and 6.0 μg/L lindane (mean measured concentrations). After a 240-h exposure period a decrease in feeding rate was recorded only for gammarids that had been exposed to 6.5 μg/L lindane, however exposure to very low concentrations of lindane (0.1 and 0.9 μg/L) resulted in a significant increase in gammarid feeding activity. In the experiment conducted with 3,4-DCA the calculation of median feeding times or FT50s of gammarids that had been exposed for 96 and 240 h in the toxicant treatment groups with A. aquaticus was largely precluded (in most groups less than 50% of the A. salina eggs were eaten). However, control group FT50 values were determined on each occasion the bioassay was performed, indicating that a substantial reduction in gammarid feeding activity had occurred in the majority of the 3,4-DCA treatment groups.