Keywords: mining pollution, Chile, subtidal habitats, heavy metals, costal marine communities
The effects of mining pollution on subtidal habitats of northern Chile
Mining is the most important commercial activity in Chile, producing more than 60% of the total national income. In northern Chile, where mining extraction is concentrated, solid and liquid pollutants resulting form copper and iron ore processing are discharged to the ocean. The studies on the effects of mining on coastal marine environments in Chile mainly consist of the evaluation of heavy metal concentrations in organisms and intertidal sediments. There are no references on the effects of mining discharges on populations and communities of the shallow subtidal habitats. During 1996-1997, covering more than 1500km of coast (in polluted and control areas), we studied: the chemical characterisation of copper and iron discharges; the distribution of heavy metals in Lessonia trabeculata (frond, stipe and holdfast); the distribution of heavy metals in seawater; changes on Lessonia composition and quality of Phycocolloid and morphology; and the effects upon the macroinvertebrate community associated with Lessonia holdfast and on the rocky subtidal community. All these variables were examined over time, at different depths and at various distances from the discharge source. We show here that tailings from copper mining cause more ecological perturbation than those from iron extraction. However, the lack of organisms in areas close to mining activities could be caused by the accumulation of fine sediments more than the heavy metal content per se. This work shows that levels of heavy metals in seawater, plants and alginates of Lessonia in contaminated and pristine sites are highly variable. In this context, environmental factors, such as temperature, wind intensity, tidal regimes, water movement, wave impact, coastal circulation, local orogenetic processes, tectonic movement, shore topography, coastal up welling and global oceanographic phenomena, such as El Nino, must be considered in the future in the interpretation of the effects of heavy metals in coastal marine communities.