ABSTRACT
This chapter discusses the use of microbial toxicity test systems in the assessment of contaminated sediments. It begins with brief discussions of indigenous, community-level enzyme activity tests and of liquid-phase tests on sediment extracts. Microbial enzyme activity measured in whole sediment samples has been shown to be a meaningful indicator of contamination. Microbial communities are useful monitors because they can respond rapidly to changes in environmental conditions and play a major role in ecosystem biogeochemistry. While liquid-phase microbial tests have yielded useful data, they do not expose the bacterial cells directly to sediment particles. Screening tests should be viewed as operationally defined detection systems, used to identify problem areas where more resources and intensive effort should be focused. There is an inevitable trade-off between the value of direct environmental relevance and sensitivity to measurement of chronic effects, both of which favor macroscale tests, and the capacity to evaluate large numbers of samples at a reasonable cost, which favors microscale tests.
