The ecological effects of mining discharges on subtidal habitats dominated by macroalgae in northern Chile: population and community level studies

Abstract

In 1996/97, a study was carried out to evaluate several variables related to the potential ecological effects of soluble copper and iron released as the result of direct dumping of mine tailing into the littoral zone of the Pacific Ocean off northern Chile. Variables studied included:

1. content of copper and iron in mining discharges;

2. distribution of Cu and Fe in seawater at study sites;

3. distribution of Cu and Fe in the seaweed Lessonia trabeculata and in its alginates (obtained from frond, stipe and holdfast);

4. alterations in Lessonia morphology; and

5. variability in the macroinvertebrate community associated with Lessonia holdfasts and the inter-plant subtidal community.

The variables were evaluated for different depths and distance from discharge sources, as well as for control areas far from any mining activity. It was observed that tailings from copper mining caused more ecological perturbation than those from iron mining; however, the lack of organisms very close to tailing discharges could be caused by stress produced by loading of fine sediments rather than by the presence of heavy metals. This work shows that the concentrations of heavy metals in seawater, plants, and alginates of Lessonia in contaminated and control sites were highly variable, decreasing with depth and distance from the contamination source. What were originally considered as control areas far from anthropogenic metal release, showed high concentration of heavy metal due to natural orogenetic processes occurring along the Chilean coast.