ABSTRACT
Benthic macroinvertebrates, as a group, are often the optimal assessment tool in determinations of sediment toxicity. Sediment toxicity testing began with freshwater benthic macroinvertebrates, namely the mayfly, Hexagenia limbata, and the midge, Chironomus tentans, in 1977. Sediment/water contact time in sediment toxicity assays may exert substantial effects on overlying water quality and therefore organism response. Perhaps the most important issue in sediment toxicity testing is the appropriate sediment phase to test. Given the sensitive and tenuous nature of sediment integrity, exposure conditions are particularly crucial in determining contaminant behavior and organism or community response. Natural geochemical properties, such as sediment texture, may influence the response of infaunal animals in sediment tests. Indigenous animals may be present in field-collected sediments. The benthic community is comprised of several taxonomic levels of organisms, and many have been used in toxicity assessments, including bacteria, protozoans, nematodes, bryozoans, oligochaetes, amphipods, gastropods, pelecypods, insects, and periphyton.
