An assessment of the ontario ministry of the environment protocols for conducting Daphnia magna acute lethal toxicity tests with pulp and paper mill effluents

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Abstract
The Ontario Ministry of the Environment protocols for conducting Daphnia magna acute lethal toxicity tests were evaluated for pulp and paper mill effluents. The evaluation included an interlaboratory study and an intralaboratory assessment using different dilution waters, test containers and pH adjustment. When the tests were conducted under similar conditions, the results (i.e., 48‐h LC50s) from four participating laboratories were similar. With one exception, the coefficients of variation for interlaboratory testing ranged from 3.0 to 17%. However, within a laboratory, the ratio of the highest to lowest LC50 values for a particular effluent ranged from 1.9 to 3.8 when using different dilution waters and ranged from 1.3 to 1.9 when the test solution pH was adjusted to the same level as the dilution water pH. The D. magna were found to be 1.5 to 4.0 times less sensitive than rainbow trout and 1.6 to 3.0 times less sensitive than Ceriodaphnia affinis to pulp and paper mill effluents, and dehydroabietic acid.