AbstractThe relative sensitivities and discrimination abilities of theDaphnia magna48‐h lethality assay of sediment pore water, thePhotobacterium phosphoreum15‐min bioluminescence inhibition (Microtox®) assay of sediment pore water and theChironomus tentans10‐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, theD. magnalethality assay was the least sensitive and discriminatory. The Microtox® assay was the most sensitive. Based on lethality, theC. tentansassay was less sensitive thanD. 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 ofC. tentansrelative to that on control sediment in which chironomids were observed. This sediment toxicity is also approximately that which killsD. 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 theD. magnalethality test could be used to predict which sediments were so toxic that benthic insects would not be expected to be present. A principal components analysis demonstrated that the Microtox® assay gave sufficiently different information that it could be included in a battery of sediment toxicity tests designed to accurately classify the toxicities of s
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