In contrast to the results of this study, Strömgren et al. (1986)observed significant reductions in shell growth of the mussel M.edulis exposed to high concentrations of a microencapsulated mixture of n-alkanes. Concentrations used in our study were, however,approximately 1,000 times less than those used by Strömgren et al.(1986) and were the likely cause of the observed differences. Interestingly,Strömgren et al. (1986) found no difference in the effect of the aromatic and the n-alkane hydrocarbon mixtures on shell growth. Typically, aromatics are viewed as being more toxic than aliphatic hydrocarbons (Anderson et al. 1974). Given that very little is known about the effects of hydrocarbons on shell production (Strömgren 1986, Strömgren et al. 1986) further research in this area is clearly warranted.