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The toxicological responses of three species to 103 surficial saltwater sediment samples from Sydney Harbour, and coastal lakes and estuaries on the south-east coast of New South Wales, Australia, were tested in a battery of four to six laboratory toxicity tests. This is the first large-scale toxicological study of sediments in Australia, the objective of which is to assess the protective and predictive abilities of North American biological effects-based sediment quality guidelines, recently adopted in Australia. Amphipods were exposed to whole sediments in survival and reburial tests, sea urchin fertilisation and larval development tests were conducted on porewaters, and bacterial bio-luminescence (Microtox) tests were conducted on organic solvent extracts and porewaters. Local indigenous species were used for the amphipod and sea urchin tests (Corophium sp. and Heliocidaris tuberculata, respectively). A wide range of responses, from <25 to 100% of negative controls were observed in all tests. Mean control-adjusted responses ranged from 46 to 96% for all tests. The percentages of highly toxic samples ranged from 11 to 83% in the various tests. The order of test sensitivity was: amphipod survival < Microtox test of porewaters < amphipod reburial < sea urchin larval development < sea urchin fertilisation < Microtox test of solvent extracts. Concordance between toxicity tests in classifying samples as highly toxic or not, ranged from 47 to 79%, indicating some similarities between test results, but not complete equivalence. Combined toxicity test results showed that the incidence of highly toxic responses occurring in the majority of tests (75-100% of tests) was low (5% of samples), but a large percentage of samples had highly toxic results in at least one test (76% of samples). Toxicity was more pervasive in the Sydney region than in coastal lakes and estuaries south of Sydney. The current study demonstrated the utility of indigenous invertebrate species and the Microtox bacterium in a sediment toxicity test battery for Australian saltwater sediments.

Interim sediment quality guidelines (ISQGs) adapted recently to Australia from North American effects-based guidelines were evaluated with matching chemical and toxicological data collected for sediments (n = 103) from Sydney Harbour and south coast estuaries of New South Wales. The incidence of toxicity for the test battery was low (7%) among samples with all chemical concentrations below ISQG-Low values, indicating these guidelines are accurate and protective of non-toxic conditions. The incidence of toxicity increased greatly (to 73%) when one or more ISQG-Low values were exceeded, suggesting that ISQG-Low guidelines are appropriate for compliance. Frequent toxic effects (in>75% of samples) were associated with chemical concentrations exceeding ISQG-High guidelines. As expected, the high guideline values were more predictive of adverse effects than the low guidelines. Predictive abilities of ISQGs were not markedly affected by normalization of organic compounds to organic carbon or the use of dilute acid extractions for metals, suggesting that the guidelines are applicable to a wide range of conditions.

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