Effects of Injected Organochlorines on Naturally Incubated Herring Gull Eggs

Abstract

Organochlorine contaminants were extracted from Lake Ontario herring gull (Larus argentatus) eggs and injected into relatively uncontaminated, unincubated gull eggs on Kent Island, New Brunswick. Synthetic mixtures of PCB's, DDE, mirex, photomirex and hexachlorobenzene were injected in a similar fashion. All eggs were incubated by their natural parents. No increases in embryonic or chick mortality were observed in any contaminant injected group when compared to the injected controls. The embryonic uptake of pollutants was similar in naturally contaminated eggs and injected eggs. The significance of these findings with regard to the reproductive failure of Lake Ontario herring gulls is discussed. J. WILDL. MANAGE. 42(3):484-493 Increased embryonic death has been reported in herring gull colonies having poor reproductive success in Lakes Michigan (Keith 1966, Ludwig and Tomoff 1966) and Ontario (Gilbertson and Hale 1974, Gilman et al. 1977). The levels of several organochlorine compounds contained in eggs from these colonies are amongst the highest levels found in the Great Lakes. Artificial incubation studies indicated that eggs from Lake Ontario were less likely to hatch than eggs from less contaminated areas (Gilman et al. 1977). These incubation studies provided conclusive evidence that some factor associated with the egg itself and not linked to parental incubation behavior was responsible for much of the egg failure observed on Lake Ontario colonies. Strong correlations have been established between high concentrations of organochlorines and poor reproductive success for many avian species (Jefferies 1973, Blus et al. 1974, Gilbertson 1974, Newton and Bogan 1974, Fyfe et al. 1976). Controlled laboratory feeding studies have indicated that some organochlorines can induce embryonic mortality, but there is considerable species variation (Peakall et al. 1972, Tumasonis et al. 1973). Injections of PCB's into chicken eggs have caused complete hatching failure (McLaughlin et al. 1963). The amounts injected (ca. 300 and 600 ppm on a whole egg basis) were approximately 2-4 times the amount presently found in Lake Ontario herring gull eggs (Gilman et al. 1977). Organochlorines other than PCB's have been found relatively nontoxic when injected into chicken eggs at levels below 250 ppm (Dunachie and Fletcher 1969). No report has been published on the effects of injecting organochlorine contaminants either individually or in combination into eggs of wild birds. The study reported in this paper was an attempt to establish whether a causal relationship existed between levels of organochlorine contaminants in the yolk 484 J. Wildl. Manage. 42(3):1978 This content downloaded from 157.55.39.43 on Fri, 30 Sep 2016 05:29:52 UTC All use subject to http://about.jstor.org/terms INJECTED ORGANOCHLORINES IN GULL EGGS* Gilman et al. 485 lipid and herring gull embryonic survival. We limited our study to the examination of the direct embryo-toxic effects of yolk-borne organochlorines and did not examine the possible effects of such contaminants on the egg during its formation. To test thoroughly this cause and effect relationship we attempted to simulate environmental conditions as closely as possible. We injected known quantities of contaminants extracted from Lake Ontario herring gull eggs and some laboratory mixtures of organochlorine contaminants into unincubated and relatively uncontaminated herring gull eggs in New Brunswick. We also permitted the adult New Brunswick herring gulls to incubate the injected eggs to eliminate the effects of either abnormal incubation (Fox et al. 1978) or artificial incubation. Our reasons for using unincubated eggs for injection were threefold. First, organochlorine contaminants of eggs are laid down during yolk formation and are present during ovulation, fertilization, oviposition, and incubation of the egg. Dunachie and Fletcher (1969) have found that chlorinated cyclodiene pesticides are more toxic when injected early in incubation than later. Second, the proportion of embryonic mortality in Great Lakes herring gulls occurring during the first 7 days of incubation was high and ranged from 26 percent in Lake Michigan (Keith 1966) to 89 percent in Lake Ontario (Gilbertson 1974). In addition, a high percentage of eggs from these heavily contaminated areas failed to show any embryonic development (Gilman unpublished, Keith 1966). Third, we hypothesized that the embryonic mortality resulting from the presence of injected contaminants that had been extracted from eggs from an area with an overall failure rate of 80 percent in 1975 (Gilman et al. 1977) would be greater than the possible 50 percent mortality induced by the trauma of injecting unincubated eggs (Khera and Lyon 1968). The authors wish to thank J. Ryder, Lakehead University, who assisted with the uptake study and C. Huntington who permitted us to use the facilities of Bowdoin Scientific Station on Kent Island, N.B. L. Reynolds, Ontario Research Foundation, performed the analyses required for the uptake study, and R. Norstrom and H. Won, Toxic Chemicals Division, CWS, Ottawa, provided valuable assistance in the extractions and analyses