Effects and fate of sediment-sorbed linear alkylbenzene sulphonate (LAS) on the bivalve mollusk Mytilus galloprovincialis Lmk.

The toxicity of LAS on aquatic animals has been evaluated in particular relation to its concentration in water, although it is well known that sediments play an important role as repositories and sources of many contaminants, including surfactants. The aim of this study was to evaluate the effects of sediment-sorbed LAS on the marine mussel Mytilus galloprovincialis exposed to sediments drugged with 132 mg/kg dry weight of LAS mixtures. Four experiments were performed and some physiological parameters (filtration, oxygen uptake, nitrogen excretion) were measured on control and treated animals. In order to study uptake and release of sediment-sorbed LAS by mussels, quantification of weight, percentage of organic matter, LAS concentration and LAS homologue distribution on faeces were determined. Results showed no significant differences in physiological responses of treated mussels compared to controls, and the absence of a toxic action of LAS contaminated sediments. Moreover one notable aspect was that higher LAS concentrations were found in faeces than in uningested sediments recovered from water. This fact is tentatively explained either as the result of decreased desorption in the mussel intestinal tract with respect to circulating water, or as enrichment in fine particles by mussel filter feeding activity.