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

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 t he contamination with mercury and organochlorine compounds. The sites were Alegarrobo, Concepcion, Maiquillahue Bay, Dona Sebastiana Island (Chalcao c hannel at Chiloe) and Magdalena Island (Straits of Magellan). We found diff erences among the sites: Kelp Gull eggs from Chiloe and Algarrobo had the g reatest concentrations of mercury (about 170 ng g(-1) fresh weight). Residu es of DDT were greatest in eggs from Algarrobo and Maiquillahue Bay, those of PCBs (polychlorinated biphenyls) greatest at Algarrobo and Concepcion. H CB had highest levels at Concepcion. Considering all organochlorines, sampl es from Algarrobo had the highest concentrations, those from Chiloe the low est. In consequence we found a geographical pattern from north to south, i. e., from areas with nr eater to less er human impact. In comparison with ot her studies, the levels of environmental chemicals found in Kelp Gulls from Chile are much lower than those known to cause adverse effects on reproduc tive success.