EFFECTS OF STORAGE TIME ON TOXICITY OF SEDIMENTS FROM PUGET-SOUND, WASHINGTON

The effects of sediment storage time were determined for three sediment toxicity tests: the amphipod test using Rhepoxynius abronius, the polychaete test using Neanthes sp., and the Microtox(R) test using Photobacterium phosphoreum. Sediments were collected from a reference area and a contaminated area in Puget Sound to determine the effects of storage time on each type of sediment. Toxicity comparisons were also made between the two kinds of sediment to simulate the manner in which the data might be analyzed in a regulatory or decision-making context. Sediments were stored at 4 degrees C for as long as 16 weeks. Results of all three toxicity tests varied significantly with storage time for each type of sediment. Amphipod survival generally decreased with storage time, whereas luminescence in the Microtox test and polychaete biomass varied unpredictably. The significance of differences between results for the two sediments varied unpredictably with storage time for the amphipod and Microtox tests. By contrast, differences were consistently significant for all storage times for the polychaete test, primarily because of the large differences in the test response between sediments. These results suggest that effects of storage time are greater for results indicative of low to intermediate levels of toxicity than for results indicative of high levels of toxicity. It is recommended that sediments be tested as soon as possible after field collection to minimize the potential for alterations of toxicity during storage.