Abstract

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 from copper and iron processing are discharged to the ocean. The studies on the effects of mining pollution 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 1500 km of coast (in polluted and control areas), we studied (1) the chemical characterization of copper and iron discharges, (2) the distribution of heavy metals in Lessonia trabeculata (frond, stipe and holdfast), (3) the distribution of heavy metals in seawater, (4) changes on Lessonia composition and quality of phycocolloid and morphology, (5) the effects upon the macroinvertebrate community associated with Lessonia holdfast and on the rocky subtidal community. Ail 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 he caused by the accumulation of fine sediments more than the heavy metal content per se. This work shows that the 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 upwelling 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.