Comparisons between microscale and whole-sediment assays for freshwater sediment toxicity assessment

The use of several microscale assays for evaluating freshwater sediment toxicity was investigated to develop a representative and cost-effective test battery. The bioassays evaluated (18 assays total) included microscale assays performed on solid-phase, pore water, and organic extracts as well as conventional standardized whole-sediment assays with Chironomus riparius and Hyalella azteca on 10 sediment samplescollected in the St. Lawrence/Great Lakes system. Selected sediment physical and chemical characteristics were also conducted to aid in the interpretation of results. Benthic invertebrate assays such as C. riparius and H. azteca endpoints were found to correlate well to contaminant levels. Microscale assays such as ATP (adenosine. triphosphate) measurement of sediment microbial biomass gave promising results to predict whole-sediment toxicity to benthic invertebrates. Most assays on pore water did not adequately represent whole-sediment toxicity, whereas organic extracts appeared to be more representative, alleviating some potential confounding factors such as interference due to toxicity caused by ammonia. [ABSTRACT FROM AUTHOR]