SPATIAL AND TEMPORAL VARIABILITY IN TOXICITY OF HAMILTON HARBOR SEDIMENTS - EVALUATION OF THE HYALELLA-AZTECA 4-WEEK CHRONIC TOXICITY TEST

A recently proposed static chronic toxicity test for sediments using 0-1 week old Hyalella azteca was applied to sediments collected on seven different dates and at five sites over a 3-year period in Hamilton Harbour, Ontario. Survival varied dramatically, from 0 to oven 80%, at several sites, indicating that sediment samples must be collected on a number of different dates at each site if an accurate assessment of potential toxic effects to biota is to be made. Repeatability of the test was good. Furthermore, the variation in survival in sediments collected over a series of closely spaced sites in the vicinity of the two most toxic sites was much less than the variability observed between sampling dates. This suggests that the high temporal variability in sediment toxicity is real, and is not an artifact of the test procedure or high spatial variability in the sediments around the sampling sites. Although highly variable, the data suggest that the toxicity of Hamilton Harbour sediments has been decreasing over the study period. Toxicity could not be correlated with the concentrations of metals, chlorinated organic compounds, or PAHs.