Organochlorine chemical residues in herring gulls, ring-billed gulls, and common terns of western lake superior

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Abstract

Residues of polychlorinated biphenyls (PCBs), DDE, DDT, and hexachlorobenzene (HCB) were analyzed for three age classes (e.g., pre-fledge muscle and blood, and post-fledge muscle) of the herring gull, ring-billed gull, and common tern for samples collected in the western end of Lake Superior in 1977. Concentrations of PCBs were highest and HCB concentrations were lowest of the chemicals analyzed in all four sample types and for all three species. Without exception, concentrations of all residues increased from the pre-fledge to the post-fledge stage despite this being a period of dilution. Residue concentrations of PCBs, DDE, and DDT in the eggs were higher (P < .01) for the herring gull than for the ring-billed gull and common tern, but concentrations in the latter two species were similar. All residue concentrations in the pre-fledge samples of the common tern and herring gull were similar (P > 0.05); both species had higher concentrations of PCBs and DDT than the ring-billed gull. The herring gull had higher residue concentrations of HCB and DDE than the ring-billed gull, but the common tern did not differ from the ring-billed gull for HCB or DDE. Residue concentrations among the three species were similar in the post-fledge samples, however, there was an increasing pattern of residue concentrations in the common tern relative to the gull species. Principal component analysis revealed that residue concentrations of PCBs, DDE, and DDT were highly correlated (r > .76) in all three sample types and the first principal component could express a high proportion of the variation (>65%) in residue concentrations. In contrast, HCB residues were more independent and correlated (r > .53) with the second principal component. There was little correspondence between blood residue samples and the pre-fledge muscle samples. Residue concentration differences among the species are probably related to different life histories. The concentrations are below those that affect reproduction in the gull species, but potential impairment cannot be excluded for the common tern.