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Zooplankton are an important part of the aquatic ecology of all lakes and streams. As a result, numerous methods have been developed to assess the quality of waterbodies using various zooplankton species. Included in these is the freshwater species Daphnia magna. Current test methods using D. magna involve acute lethality test methods ranging from 24 to 96 h in duration and chronic test methods with durations of 21 to 28 d. Whereas the current acute and chronic test methods are useful, a need exists for a shorter-duration test method that will provide a chronic or subchronic endpoint with this, species. In the present study, a 4-d, static-renewal survival and growth test was developed for use with D. magna. The test results were compared to performance criteria and results from 7-d survival and reproduction tests with Ceriodaphnia dubia to determine the level of comparability between the two methods. Results from the 4-d D. magna survival and growth test method indicated that this method will produce consistent results with various reference toxicant materials and provide data that are both reproducible and useful for detecting potential toxicity in aquatic environments.

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Numerous methods exist for assessing the potential toxicity of sediments in aquatic systems. In this study, the results from 10-day bulk sediment toxicity test methods using Hyalella azteca and Chironomus tentans were compared to results from 96-h Pimephales promelas and Ceriodaphnia dubia renewed acute toxicity tests conducted using elutriate samples prepared from the same sediments. The goal of the study was to determine if the results from the elutriate tests were comparable to those obtained from the bulk sediment tests. Of the 25 samples analyzed, 16 were found to be toxic to at least one of the species tested, in either elutriate or bulk sediment tests. The C. tentans 10-day bulk sediment test was the most sensitive, with 12 sediment samples exhibiting toxicity to this species, whereas the H. azteca bulk sediment test and C. dubia 96-h elutriate test were the least sensitive, exhibiting toxicity in only 7 of the 25 sediments tested. The P. promelas elutriate test found 8 of the 25 sediments to be toxic. Based on the total number of sites found to show toxicity, results from testing indicate 96-h elutriate tests show a level of sensitivity comparable to 10-day bulk sediment tests in assessing toxicity quantitatively. However, the methods did not always find toxicity at the same sites, suggesting that the ability of elutriate tests to predict toxicity (quantitatively) is not statistically correlated with bulk sediment methods. This would indicate that a suite of toxicity test methods would provide the most complete measure of site condition; however, in circumstances where bulk sediment testing is not feasible, elutriate tests can provide a practical and credible alternative for toxicity assessment.