Effects of sediment sorbed linear alkylbenzene sulphonate on juveniles of the Senegal sole, Solea senegalensis: toxicity and histological indicators.

Many synthetic organic substances, including surfactants, tend to be sorbed on suspended solids and to accumulate finally on bottom sediments, where benthic communities may be exposed to them. Concentrations of Linear Alkylbenzene Sulphonates (LAS) have been detected in estuarine and coastal sediments, presenting wide concentration ranges depending on the presence of treatment facilities, hydrodynamic conditions, organic matter content etc. Senegal sole, Solea senegalensis, larvae (40 days posthatching; dph) were exposed to increasing concentrations of LAS spiked sediments, comprised between 0.37 and 880.78 mg LAS x kg(-1) during 30 days. The obtained results showed that survival of exposed larvae was not significantly affected at environmentally relevant concentrations, the LC50 value being obtained after 30 days 876.46 mg x kg(-1). However, the histological and histopathological analyses carried out in target organs revealed, that first alterations from the normal pattern were observed at concentrations of 222.66 mg x kg(-1), presenting effects such as blood extravasation and hyperplasy of the lamellar epithelium in gills, increase of inter-myotomal spaces of the skeletal musculature and edematous separation of the skin from epidermis. At the highest exposure concentrations (755.27 and 880.78 mg LAS x kg(-1)), shrinkage of hepatocytes, nuclear pycnosis and blood stagnation are observed in the liver, degeneration of pancreatic cells, reduction of hemocytopoietic tissue in the kidney and vacuolisation of intestinal enterocytes was observed at histological level, as well as severe separation of the epidermis from the underlying tissues. Simultaneously, a significant increase of the wet weight with exposure concentration was observed in the test organisms.