Initial effects of the toxic waste spill (Aznalcollar mine accident) on the aquatic macrofauna of the Guadalquivir Estuary

The initial effects of the toxic waste spill in April 1998 at the Aznalcoll ar mine (SW Spain) on the nektonic community of the Guadalquivir Estuary we re examined at three sampling sites using univariate and multivariate techn iques. Since studied communities showed a considerable seasonal trend, only seasonally homogenous periods were compared to analyse effects of the spil l: May-August 1997 (before spill) and May-August 1998 (after spill). Result s of both techniques (two-way nested ANOVA and ANOSIM tests, P > 0.05) indi cated that there was no significant difference between the nektonic communi ty of the estuary before and after the spill (monthly number of species, ab undance, biomass and similarity among samples). Conversely, an unusually hi gh density was observed at the outer sampling site immediately after the sp ill for species typical of more stagnant estuarine habitats. This feature s eems to indicate that the fauna in the estuarine area through which the unt reated water penetrated into the main course may have been disturbed. Resul ts also suggest that this initial sudden input of fresh water to the estuar y could have enhanced the effects of an increased river flow (a drop in the salinity). Nevertheless, longer temporal series of data, especially for pe rmanent estuarine inhabitants, are recommended before conclusions can be dr awn on the effects of the toxic waste spill on estuarine communities. (C) 1 999 Elsevier Science B.V. All rights reserved.