A comparison of North American and West European oyster embryo-larval toxicity tests on North Sea sediments

Abstract

During the Bremerhaven Workshop, Pacific oyster embryos Crassostrea gigas were exposed both directly to sediment and to elutriates of sediment from 2 transects through contamination gradients in the North Sea. One transect consisted of 7 stations down-current from an abandoned drilling site off the Dutch coast. The other transect comprised 9 stations in the German Bight positioned in a northwesterly direction from the Elbe-Weser plume out to the Dogger Bank. The toxicity tests, conducted by 4 research laboratories, were carned out either immediately following sediment sampling on board a research vessel, or after periods of up to 4 wk after sediment collection at mainland laboratories in the UK, Canada and The Netherlands. Oyster embryo-larval sediment elutriate tests showed highest levels of tox~city at the most contaminated sites on the German Bight transect, but data were not consistent on the drill~ng site transect. The optimal method of sediment elutriation should be determined by further studies. Oyster embryos exposed directly to sediment over a 48 h period identified the most toxic and contaminated sites from both transects and gave comparable results to infaunal amphi-pod acute toxicity tests. This study has demonstrated that oyster embryo-larval tests can easily be carried out on board a seagoing research vessel, although there is no absolute requirement to do so when sediment samples can be returned to mainland laboratories within a few days after collection.