The Kelp Gull as bioindicator of environmental chemicals in the Magellan region. A comparison with other coastal sites in Chile

Abstract

During the breeding seasons 1994/5 and 1995/6 we collected Kelp Gull (Larus dominicanus) eggs from five locations in central to south Chile to study the contamination with mercury and organochlorine compounds. The sites were Algarrobo, Concepcion, Maiquillahue Bay, Dona Sebastiana Island (Chalcao channel at Chiloe) and Magdalena Island (Straits of Magellan). We found differences among the sites: Kelp Gull eggs from Chiloe and Algarrobo had the greatest concentrations of mercury (about 170 ng g-1 fresh weight). Residues of DDT were greatest in eggs from Algarrobo and Maiquillahue Bay, those of PCBs (polychlorinated biphenyls) greatest at Algarrobo and Concepcion. HCB had highest levels at Concepcion. Considering all organochlorines, samples from Algarrobo had the highest concentrations, those from Chiloe the lowest. In consequence we found a geographical pattern from north to south, i.e., from areas with greater to lesser human impact. In comparison with other studies, the levels of environmental chemicals found in Kelp Gulls from Chile are much lower than those known to cause adverse effects on reproductive success.