Density and size dependent uptake of various PAC in organisms of a model food chain

The fate of hydrocarbons discharged at sea was studied in laboratory exposu res examining the uptake of PAC (polyaromatic compounds) in marine organism s. Methodology and species selection were guided by the Northwest European (OSPAR) convention. The acute toxicity of poorly soluble substances is norm ally assessed by preparing water accommodated fractions (WAF). Following su ch tests we studied PAC uptake in unicellular algae, crustaceans and fish. Preparation of WAF was first improved because in the standard procedure, oi l droplet size increased with oil loading and flask size. At similar exposu re levels the proportion of large molecular weight PAC associated with alga e increased when the density of algae decreased. However, as body size incr eased via crustaceans to fish more of the smaller molecular weight PAC were bioconcentrated. Organism density and type of organism thus influence the abundance of PAC in food chains.