Assessment of Sediment Toxicity to Marine Benthos*

Most chemical contaminants entering the marine environment eventually accumulate in sediments and, thereby, potentially render the sediments toxic to benthic and demersal organisms. The assessment of the toxicological effects of sediment-associated chemicals can be made with a variety of relatively simple bioassays. The toxicity of contaminated sediments may be modified by abiotic factors, in addition to the absolute concentration of specific chemicals. The geological properties of sediments can also affect the apparent toxicity of a sediment by modifying the bioavailability of the contaminants or by exerting a direct stress on the test organism. Acute lethality tests have been developed for amphipods, cumaceans, copepods, shrimps, isopods, bivalves, polychaetes, and fish. Amphipods are among the most sensitive of benthic species. Pore water concentrations of contaminants are often correlated with toxicity. The bivalve larvae test procedure is a well-established and reliable indicator of water quality. A negative control of uncontaminated substrate must also accompany each run of a toxicity test procedure.