| Summary: | Sediments have been recognized as a potential source of contamination in aquatic
environments. Toxicity testing has been used as a tool for studying sediment related
toxicity, although many aspects of the methodology are still evolving. However, it
has been debated whether or not the results of laboratory assays can be
extrapolated to ecosystems effects. As well, questions arise about changes that
occur in sediments when they are manipulated in the laboratory during toxicity
testing.
This study examined the effects of sampling method on sediment toxicity. Toxicity
tests were performed on sediment which had been mixed (homogenized) and the
toxicity compared to that of undisturbed sediment cores, where the integrity of the
sediment had been maintained. Toxicity tests performed on the sediment included
Daphnia magna, Chironomus tentans, and Microtox®. Chemical analysis of the
sediment was also done, including metals, polynuclear aromatic hydrocarbons
(PAH), ammonia, and metal/sulfide ratios.
It was found that the method of sampling affected toxicity of sediments to
Chironomus tentans in about half the cases. However, the method of sampling did
not affect toxicity to Daphnia magna, probably because the type of contaminants
found in the sediments were not available to the Daphnia. Daphnia magna were
unresponsive to all sediment tested. A bacterial luminescence bioassay (Microtox®)
was also performed to compare the sensitivities of the different toxicity tests. It was found that the Microtox® Solid Phase Test was the most sensitive of all the tests,
and was able to distinguish between contaminated and uncontaminated sediment.
The measurement of metal/AVS ratio in sediment was not found to be a useful tool in
determining whether a sediment would be toxic or non-toxic to organisms.
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