PARENT SESSION
5E SPECIAL SYMPOSIUM: Effect assessment in marshlands and areas of high eocological value: the "Aznalcollar accident, Spain" case study
9:00 AM to 7:00 PM, Wednesday, 09 May 2001

(W/MF185) Histopathological Effects associated with the dilution of toxic mud from the Aznalcollar mining spill using Solea senegalensis.

Gonzalez de Canales, Maria Luisa¹, Riba, Inmaculada ², Bosco, Juan ¹, Garcia-López, Angel¹, Forja, Jesus², Gómez-Parra, Abelardo², Sarasquete, Carmen³, DelValls, Angel², ^{1 2 3}

ABSTRACT- Long-term exposure sediment toxicity tests (15 and 30 d) using the senegal sole (Solea senegalensis) were performed to identify the histopathological alterations associated with toxic mud from the Aznalcollar mining spill (AMS). Juvenile specimens of the fish were taken from our culture plant in the Marine Science Faculty at the University of Cadiz. Four different dilutions (0.5, 2, 8 & 20 % -dry sediment-) were carried out using clean sediment (located at the Bay of Cadiz, DelValls et al., 1998) as negative control. Fish were placed in toxicity tests and control by duplicate (6 fish per aquarium). Fish Samples were taken at 0, 15 and 30 days for histopathological and biochemical purposes. Liver, kidney, gut, gills, skin, spleen and heart were taken and fixed in a phosphate buffered 10% formaldehyde for histological investigation. All fixed materials were routinely processed and paraffin embedded. Sections of 5-6 microns were stained with hematoxilin-eosin (H&E) and blue alcian (BA) for identification of mucous cells. Chloride and mucous cells from gill filaments seemed to show an increase in size and number, possibly due to an osmorregulatory stress because of the exposition. Liver and gut showed an increase in lipid droplets deposition from the beginning to 15 days in all concentrations tested and derived in an almost reduction of lipid content in those exposed to higher dose at the end of the experimental period (30 days/20% of dilution). Hepatocytes and enterocytes from these organisms showed reduction in lipid content decrease in size and a degenerated appearance with a prominent nucleoli and cytoplasmic basophylia. No exposure-related light microscopical alterations were noticed in the rest of the organs in any of the experiments. The present experiment showed a time and dose-dependence in the occurrence of histopathological disorders in fish exposed to the AMS toxic mud.

Key words: Aznalcollar mining spill, sediment toxicity, histopathological effects, solea senegalensis