TOXICITY OF HARBOR CANAL SEDIMENTS BEFORE DREDGING AND AFTER OFF SHORE DISPOSAL

Dredge material from an entrance waterway to the port of Rotterdam and sediments from the North Sea off-shore disposal site were tested for toxicity using three different sediment bioassays, The goals of the st udy were to evaluate if bioassays generate useful additional informati on to chemical based sediment quality criteria, and to investigate pot ential changes in toxicity of dredge material after off-shore disposal , Sediment elutriates were tested with larvae of the oyster Crassostre a gigas, whole sediments with the infaunal amphipod Bathyporeia sarsi, and sediment suspensions with the blue mussel Mytilus edulis. The con tamination of the investigated dredge material was low according to th e limited set of chemical parameters that was analysed, Nevertheless t he three bioassays showed that some of the dredge material samples sig nificantly affected the survival of oyster larvae and the amphipod B. sarsi, as well as the aerial survival time of mussels, Toxicity was re duced at the off-shore disposal site, probably due to the dispersal of the most polluted finer sediment fractions by strong residual current s, It is concluded that the sediment bioassays used for this study are a meaningful tool that should be incorparated in decision making fram eworks for the management of dredge material. (C) 1997 Elsevier Scienc e Ltd.