Critical evaluation of CROSERF test methods for oil dispersant toxicity testing under subarctic conditions.

The aquatic organisms toxicity testing protocols developed by the chemical response to oil spills: Ecological Research Forum (CROSERF) were evaluated for applicability to assessing chemical dispersant toxicity under subarctic conditions. CROSERF participants developed aquatic toxicity testing protocols with the foremost objective of standardizing test methods and reducing inter-laboratory variability. A number of refinements are recommended to adapt the CROSERF protocols for testing with subarctic species under conditions of expected longer oil persistence. Recommended refinements of the CROSERF protocols include testing fresh and moderately weathered oil under conditions of moderate mixing energy, preparing toxicity test solutions using variable dilutions rather than variable loading, performing tests with subarctic species using static exposures in open chambers, increasing the duration of tests from 4 to 7 days, quantifying approximately 40 PAHs and their alkyl homologs, assessing the potential for photoenhanced toxicity, and incorporating a bioaccumulation endpoint by measuring tissue concentrations of PAHs. Refinements in the preparation of oil dosing solutions, exposure and light regimes, and analytical chemistry should increase the utility of the test results for interpreting the toxicity of chemically dispersed oil and making risk management decisions regarding dispersant use under subarctic conditions.