Surface microlayer contamination and toxicity in the German Bight

Abstract

Samples of sea-surface microlayer and near-surface bulkwater were collected at 5 stations in the German Bight area of the North Sea and at Wilhelmshaven, Germany, during the Bremerhaven Workshop in March 1990. Samples were analyzed for concentrations of heavy metals, organotin and tributyltin (TBT) and tested for toxicity using 5 different bioassays. Results indicate that: (1) sea surface contamination is widespread and extends at least 100 km from shore, (2) the surface microlayer contains higher concentrations of metal and organometal contaminants and is more toxic to marine organisms than the subsurface bulkwater, (3) echinoderm larvae, molluscan bivalve larvae and copepod toxicity tests all represent feasible options for offshore pollution assessment, (4) larval survival in bioassays was inversely related to the concentrations of several contaminant metals in the microlayer, (5) glass plate, screen and rotating drum samplers all collect samples which are similar in metal concentrations and toxicity, but the drum offers several operational advantages for routine sampling and monitoring of sea surface contamination, and (6) the threat of surface microlayer contamination to the recruitment of North Sea fisheries warrants further examination.