EXECUTIVE SUMMARY
From a literature review, eight sublethal tests were recommended for further laboratory evaluation, and possibly for subsequent field validation: Microtox™ chronic test, Selenastrum microplate, multi-species algal microplate; duckweed, Ceriodaphnia; nematode; fathead minnow, larval growth; trout early life-stages. Ceriodaphnia was scored highest. The nematode test might prove to be a simple assay to represent multi-cellular animals. Fluorescence should be considered as an endpoint in algal tests, because of apparent speed, economy, and freedom from interference by turbidity.
Many sublethal tests are now relatively fast and cheap to carry out. The literature indicates that they would be useful tools for the Canadian metal mining industry, for predicting effects of effluents in receiving-waters. For monitoring, toxicity tests on the effluent have major advantages of speed and economy over field surveys.
A complete strategy for monitoring discharges should include three tactics. (1) Measurements at the end of the effluent pipe. (2) Comparison with water quality objectives, both chemical and biological; tests on the effluent could be used to calculate conditions expected in the receiving water. (3) Periodic ecological surveys to check that the first two approaches are effective.
Literature reports on validating sublethal effluent tests as predictors of effects in receiving communities have used polluted rivers or semi-natural communities in various mesocosms, notably artificial stream channels with a diversity of biota.
Twenty-eight published reports gave useful information of validation; some comparisons· were subjective, and most could not be called rigorous scientific “predictive” experiments. One report was rigorous and objective, and found 88% agreement in comparing the toxicity of 43 effluents with effects in waterbodies. Eight well-publicized studies in rivers by the U.S. Environmental Protection Agency received criticism for inappropriate comparisons; statistical re-analysis showed a good relationship between toxicity of receiving-water and instream communities.
Among 72 comparisons in different experiments, there were 53 cases of general agreement between effluent tests and field effects, and 9.cases of disagreement, for 85% agreement. Ten other cases were not directly useful because they used values derived from the literature, because field effects were absent or inconsistent, or because they considered only lethal effects. Of the 62 useful cases, 50 were for mixed effluent and only 2 were for mining waste. Most comparisons were with communities in natural rivers, and only 10 of 62 used mesocosms.
AETE
