Geographical distribution of organochlorine contaminants and reproductive parameters in Herring Gulls on Lake Superior in 1983

摘要: As part of the Great Lakes International Surveillance Plan, 1978–83, egg contaminant levels and reproductive output were determined for Herring Gull colonies on Lake Superior in 1983. Since 1974, has been widely used as a spatial temporal monitor organochlorine (OC) associated biological effects. Most eggs contained wide range OCs, main compounds being DDE, polychlorinated biphenyls (PCBs), dieldrin, heptachlor epoxide, oxychlordane, hexachlorobenzene mirex. Levels an additional ten OCs five dibenzo-p-dioxin (PCDD) congeners also some sites. Overall, varied significantly among colonies, but there was no obvious relationship to distribution contaminants sediments or fish species. OC had declined by up 84% since 1974. Eggshells only 8% thinner than before introduction DDT, shell thinning not cause breeding failure. Average from 0.15 1.57 young per apparently occupied nest 1983: at 56% value below that thought necessary maintain stable populations. The causes failure disappearence cannibalism chicks. Despite this, population appeared have increasing about 4% annum. Reduced availability forage during early 1980s most likely reason poor