las comunidades de peces del río guadiamar y el accidente minero ...

Las comunidades de peces del río Guadiamar
y el accidente minero de Aznalcóllar
Introduction
On April 25th 1998, a 50-meter breach opened in the tailing pond dike of the
Aznalcóllar mine (SW Spain). This breach caused the release of about 4 hm 3 of acidic
water with dissolved metallic compounds and 2 hm 3 of mud mainly composed by
floated pyrite (Aguilar et al., 2003). To stop the spill from reaching Doñana National
Park, downstream, several dams were constructed (López-Pamo et al., 1999).
Nevertheless, 67 km of the Guadiamar River’s main channel were polluted with toxic
spill whose primary composition was Fe (34-37%), S (35-40%), Zn (0.8%), Pb (0.8%),
As (0.5%), Cu (0.2%), Sb (0.05%), Co (0.006%), Tl (0.005%), Bi (0.005%), Cd
(0.0025%), Ag (0.0025%), Hg (0.001%) and Se (0.001%) (Grimalt and Macpherson,
1999). As a consequence, approximately 2000 ha of riparian vegetation forests were
contaminated (Murillo et al., 1999), causing the death of 170 kg of red swamp
crayfishes and nearly a hundred different vertebrates (Aguilar et al., 2003). Fish were
the most affected vertebrates, and during the days following the accident 37.4 t were
collected from different areas, including carps (75-80%), mullets (10-16%), barbels (6-
8%), eels (4%) and other species (5%) (Valls and Blasco, 2005). Unfortunately, the
coarse mechanical removal of contaminants from the stream and flood plain aggravated
the effects of the toxic spill, with major implications for the geomorphological
characteristics of the river (Gallart et al., 1999). After these cleanup operations in the
affected area, a Recovery Plan (PICOVER) was implemented, aimed at repairing the
damaged ecosystems and transforming the affected area into a green corridor between
two well conserved ecosystems: Sierra Morena in the north and Doñana National Park
in the south (Cárdenas and Hidalgo, 2007; Márquez-Ferrando, 2009). The dimensions
and effects of heavy metal contamination resulting from the spill were immediately
studied in different environments such as soil (Cabrera et al., 1999), groundwater
(Manzano et al., 1999), and sediments and water (Van Geen et al., 1999). The
consequences for biota within or around the affected area were also readily investigated,
focusing on plankton, periphyton and macroinvertebrates (Prat et al., 1999); molluscs,
crustaceans and fish (Blasco et al., 1999; Drake et al., 1999); plants (Murillo et al.,
1999) and birds (Hernández et al., 1999; Benito et al., 1999). Over the years, several
studies have monitored the recovery of previous abiotic and biotic states (e.g., soil,
Fernández et al., 2007; water, Olias et al., 2005; vegetation, Madejón et al., 2010;
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