Author/s: Custer T.W., Custer C.M., Hines R.K., Stromborg K.L., Allen P.D., Melancon M.J. & Henshel D.S.

Title: Organochlorine Contaminants and Biomarker Response in Double-Crested Cormorants Nesting in Green Bay and Lake Michigan, Wisconsin, USA.

Journal: Arch. Environ. Contam. Toxicol. 40, 89-100 (2001)

Abstract: Double-crested cormorant (Phalacrocorax auritus) eggs at pipping and sibling 10-day-old chicks were collected from two colonies in Green Bay, WI, one colony in Lake Michigan, WI, and reference colonies in South Dakota and Minnesota. Egg contents and chicks were analyzed for organochlorine contaminants including polychlorinated biphenyl (PCB) congeners. Livers of embryos and chicks were assayed for hepatic microsomal ethoxyresorufin-O-dealkylase (EROD) activity. Eggshell thickness and the physical dimensions of embryo brains were measured. Concentrations of organochlorines, including p,p'-DDE (p,p'-dichlorodiphenyldichloroethylene), PCBs, and PCB congeners were generally an order of magnitude higher in eggs and chicks from Wisconsin than from reference locations. Total PCBs averaged 10-13 p,g/g wet weight in eggs from three Wisconsin colonies compared to 0.9 p,g/g PCBs from reference locations. Double-crested cormorant chicks accumulated on average 33-66 wg PCBs/day and 7-12 wg p,p'-DDE/day in the Wisconsin colonies compared to 0 wg PCBs/day and 1 wg p,p'-DDE/day in the reference colonies. At pipping, EROD activity in the livers of cormorant embryos was significantly higher in the Wisconsin colonies and significantly correlated with PCBs and the toxic equivalents (TEQs) of aryl hydrocarbon-active PCB congeners relative to 2,3,7,8-tetrachlorodibenzo p-dioxin. However, in 10-day-old chicks EROD activity was not consistently different among colonies and was not correlated with PCBs or TEQs. A significant negative relationship between embryo brain asymmetry and the size of the egg suggested that physical constraint might be an important factor influencing the response of this bioindicator. Thinner eggshells in two colonies located near Door County, Wisconsin, suggested that historic p,p'-DDE residues associated with orchards are still an important source of p,p'DDE in the local environment.

Double-crested cormorant (Phalacrocorax auritus) populations in the Great Lakes declined following the introduction of the agricultural pesticide p,p'-DDT (p,p'-dichlorodiphenyltrichloroethane) in the 1940s. p,p'-DDE (p,p'-dichlorodiphenyldichloroethylene), a metabolic product of p,p'-DDT, was considered the major contaminant responsible for the decline of double-crested cormorants in the Great Lakes (Peakall 1988). Elevated p,p'-DDE concentrations in double-crested cormorant eggs caused severe shell thinning leading to egg breakage during incubation (Gress et al. 1973; Weseloh et al. 1983) and double-crested cormorants were among the species to have suffered the greatest effects of the eggshell thinning syndrome (Anderson and Hickey 1972). Subsequent to the 1972 ban on p,p'-DDT use in the United States, environmental concentrations of p,p'-DDE declined and double-crested cormorant populations increased markedly in the Great Lakes (Weseloh et al. 1995). Even so, recent evidence suggests that p,p'-DDE contamination is still having a measurable reproductive effect on double-crested cormorants nesting in Green Bay, Wisconsin (Custer et aL. 1999).

Green Bay is also contaminated with polychlorinated biphenyls (PCBs), most of which reportedly originated from the deinking and repulping of recycled carbonless copy paper at paper mills on the Fox River (Figure 1) (Sullivan et al. 1983). Elevated PCB concentrations have been documented in Green Bay sediments (Sullivan et al. 1983; Hermanson et al. 1991; Ankley et al. 1992; Velleux and Endicot 1994; Manchester-Neesvig et al. 1996), fish (Sullivan et aL. 1983), and birds (Ankley et al. 1993; Custer and Custer 1995; Harris et al. 1993; Rattner et al. 1993; Hoffman et al. 1993; Kubiak et al. 1989; Custer et al. 1998, 1999). Even though eggs of double-crested cormorants from Green Bay have elevated PCB concentrations, PCB contamination does not seem to have a measurable effect on reproduction in this species in Green Bay (Custer et al. 1999).

Brain asymmetry and hepatic microsomal ethoxyresorufinO-dealkylase (EROD) activity in avian embryos are potential bioindicators of PCB and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) contamination. Brain asymmetry in birds has been associated with TCDD and related compounds and holds promise as a biomarker of contaminant exposure and effects (Henshel et al. 1997). EROD activity in avian embryos has been associated with PCB and TCDD concentrations in eggs (Rattner et al. 1993; Sanderson and Bellward 1995). Eggshell thickness, another bioindicator of chemical contamination, is often negatively correlated with p,p'-DDE concentrations in eggs (Weseloh et al. 1983; Custer et al. 1999). The objective of this study was to determine whether organochlorine concentrations in double-crested cormorant eggs and chicks differed among three colonies in Wisconsin and at two inland reference colonies. An additional objective was to determine whether EROD activity, brain asymmetry, and eggshell thickness differed among these locations in relation to organochlorine contamination. We predicted that p,p'-DDE and PCB concentrations in double-crested cormorant eggs and chicks from Wisconsin would be significantly greater than reference locations. We further predicted that these differences in contamination should be refiected in more brain asymmetry, higher EROD activity, and thinner eggshells in Wisconsin colonies than at the reference locations. Finally, we predicted differences among Wisconsin colonies in the PCB-associated biomarkers, brain asymmetry and EROD activity, based on their physical proximity to the source of PCBs, the Fox River.

Address: T.W. Custer, U.S. Geological Survey, Upper Midwest Environmental Sciences Center, 2630 Fanta Reed Road, La Crosse, Wisconsin 54603, USA

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