Use of protozoan communities to assess the ecotoxicological hazard of contaminated sediments

Protozoan communities developed on artificial substrates were used in a series of in situ and laboratory tests to evaluate the toxic potential of harbor sediments contaminated with polychlorinated biphenyl (PCB). Colonization dynamics in polluted and clean harbors were compared. Laboratory tests were community bioassays using standard techniques to produce sediment elutriate. Results of the in situ colonization and the community tests measuring structural changes (e.g., “decolonization”) were similar. In general, sediments from the contaminated harbor caused significant (p ⩽ 0.05) reductions in the number of taxa, in total protozoan abundance, and in phototroph abundance; however, the abundance of heterotrophic species increased in some in situ tests. Process-level parameters (e.g., respiration; island-epicenter colonization rates) were more sensitive than measurements of community structure. Phototrophs were more sensitive to sediment elutriate than were other trophic types. The information provided by this series of protozoan community tests is more complex than that provided by single-species bioassays. Although community tests may provide more information on the effects of sediment contamination on actual ecosystems than tests based on single species, they require careful interpretation to avoid misleading conclusions.