An international comparison of sediment toxicity tests in the North Sea

Toxicity testing of whole sediments was conducted as part of the Bremerhaven Workshop designed to test various methods (chemical and biological) for assessing the status of North Sea waters, sediments and biota. Six investigators from 4 countries were involved; laboratory testing was conducted after transporting field-collected sediments distances varying from tens of miles to thousands of miles. Sediments were tested from 2 contamination gradients, one from an abandoned drilling site, and the other from the mouth of the Elbe northwest across the German Bight. Methods included 11 different tests (20 end-points), 3 species of amphipod, a polychaete, a clam, an oyster and a bacterium. Amphipod 10 d acute lethality tests and a 48 h oyster larvae abnormal development test most clearly determined gradients in toxicity that corresponded with chemical and in situ community data. Lack of response was observed in Microtox and clam reburial tests. A polychaete growth test conducted in North America provided useful but not convincing information. A 24 h oyster larvae survival test conducted separately in England and The Netherlands gave results that were counter to the other tests and difficult to interpret. Survival and metamorphosis tests with older oyster larvae did not show consistent, interpretable gradients for the drilling site but did for the German Bight. The responsiveness of some tests may have been affected by a maximum 3 wk sediment holding time prior to testing; other tests did not provide usable information relative to either the burden of evidence of all tests, or corresponding chemical contamination data and benthic infaunal community structure. Based on the results of this workshop, currently the most useful sediment toxicity tests for general assessment and regulatory use in Europe are infaunal amphipod survival and 48 h oyster larval development tests.