USING THE CLAM Scrobicularia plana AND THE AMPHIPOD Ampelisca brevicornis TO DETERMINE SEDIMENT TOXICITY IN THE GUADALQUIVIR ESTUARY AFTER THE AZNALCOLLAR MINING SPILL

摘要

The Guadalquivir Estuary was impacted by the accidental release of 5 million cubic meters of acid waste from the processing of pyrite ore (25th April 1998). The waste entered ecologically sensitive and protected areas such as the National Park of Donana. The monitoring of the impact of the accidental spill showed that it was acute and that affects only to specific areas in the estuary. An integrative approach using chemical and biological measurements were performed on environmental samples from the estuary and also in dilution tests using toxic mud from the accidental spill together with clean sediment. The amphipod Ampelisca brevicornis and the clam Scrobicularia plana were selected as organisms for the tests. After 10 days of exposure for the amphipods and 96 hours for the clams to the environmental sediment samples and to the dilution tests, the mortality of the amphipods and the clams were recorded. The results show that the Guadalquivir area is not highly affected by the mining spill. However, some areas located in the Brazo de la Torre artificial channel that presents a low hydrodynamic and high residence times of contaminants in sediments, were cataloged as stressed based on moderate levels of heavy metals from the accidental spill (Zn and Cd) that are correlated to the measured toxic effect.