Toxicity of sea-surface microlayer: effects on herring and turbot embryos

Abstract Marine fish eggs, from herring ( Clupea harengus ) and turbot ( Psetta maxima ), were used to test the effects of the sea-surface microlayer on embryonic development. The eggs were exposed in static systems to full strength microlayer and 1,10,50% dilutions. Depending on the sampling site (Helgoland harbour, Kiel Forde, Travemunde marina, Elbe Hamburg Port) and time, microlayer contained varying amounts of Zn, Cd, Cu, Ni, Fe, Pb and Co, in concentrations 100 times above those found in subsurface bulk water. Chlorinated hydrocarbon pesticides were not found at concentrations elevated above bulk water, but considerable amounts of petroleum hydrocarbons and phthalate esters were detected. Microlayer displayed differential concentration-dependent toxicity for each species used in the experiments. Effects on hatching time as well as total hatch (%) and number of abnormal larvae were recorded. Herring eggs were most affected by Helgoland microlayer (suspected effect of high metal content) while turbot eggs were most sensitive to Travemunde and Elbe microlayer (suspected effect of high petroleum hydrocarbons). The usefulness of microlayer studies as a tool for environmental assessment is discussed. An impact of microlayer effects on recruitment in sensitive species is deemed possible.