Comparison of Three Sediment Bioassay Methods Using Detroit River Sediments

摘要

The relative sensitivities and discrimination abilities of the Daphnia magna 48-h lethality assay of sediment pore water, the Photobacterium phosphoreum 15-min bioluminescence inhibition (Microtox R) assay of sediment pore water and the Chironomus tentans 10-d growth reduction assay of whole Detroit River sediments were investigated and predictive relationships developed. While all three assays demonstrated the toxicity of some sediments and all of them identified the most and least toxic sediments, the D. magna lethality assay was the least sensitive and discriminatory. The Microtox R assay was the most sensitive. Based on lethality, the C. tentans assay was less sensitive than D. magna, but growth inhibition was sensitive and the most discriminatory of the three assays. Chironomids were not observed in the sediments that caused a 30% decrease in growth of C. tentans relative to that on control sediment in which chironomids were observed. This sediment toxicity is also approximately that which kills D. magna. Some locations were deemed very toxic by one or two assays but not toxic by the others. The results of all of the assays were correlated, but none of the assays accurately predicted the results of the other two. It was concluded that the D. magna lethality test could be used to predict which sediments were so toxic that benthic insects would not be expected to be present.