THALLIUM IN THE MARINE ENVIRONMENT: FIRST ECOTOXICOLOGICAL ASSESSMENTS IN THE GUADALQUIVIR ESTUARY AND ITS POTENTIAL ADVERSE EFFECT ON THE DOÑANA EUROPEAN NATURAL RESERVE AFTER THE AZNALCÓLLAR MINING SPILL (SW SPAIN)

Recibido en septiembre de 1998; aceptado en marzo de 1999 Thallium (Tl) is an extremely toxic but little-studied element in the marine environment and practically no information has been reported on the levels of Tl in marine organisms. After the Aznalcóllar mining spill (April 1998), high levels of metals were put into the environment. This acid-contaminated medium was responsible for the initial pollution effects measured in the Guadiamar River, which is an affluent of the Guadalquivir River and very close to the biggest natural reserve in Europe (Doñana). Four different species were used in the monitoring from April to September 1998 and a sediment field bioassay to check bioacumulation was performed. We present the first ecotoxicological evaluation of the mining spill in the Guadalquivir River, with reference to Tl, a little-known metal. Also, Pb and Cd data were compared to Tl during field sediment testing. Results show low levels of this metal in all of the organisms studied and they do not show any increase in the level of this metal, ranging fro