Environmental contaminants in bald eagles on the coast of British Columbia: exposure and biological effects
Creators: name: Elliott, John E.
Publisher: name: University of British Columbia
Year: 2009

description: Attracted by abundant food and nesting sites, a large (about 4,000 pairs) Bald Eagle (Haliaeetus leucocephalus) population breeds and winters around the Strait of Georgia on the Pacific coast of Canada. Eagle habitat has been extensively modified by logging and waterfront development, while industrial effluents have contaminated food chains. Until recently, most pulp mills on the British Columbia coast used elemental chlorine bleaching and did not secondarily treat effluents, thus releasing chlorine containing chemicals, particularly polychiorinated dibenzo-p-dioxins (PCDDs) and polychiorinated dibenzofurans into the local environment. As top predators, Bald Eagles are exposed to elevated levels of PCDDs, PCDFs and the chemically related polychiorinated biphenyls (PCB5) and organochlorine pesticides. This thesis addressed spatial and temporal trends in chlorinated hydrocarbon exposure of Bald Eagles and toxicological consequences at treatment populations near pulp mills in the Strait of Georgia and in industrial areas of the Fraser River delta, and at reference areas on west coast Vancouver Island, Johnstone Strait and the Queen Charlotte Islands. Initial research during 1990-199 1 focused on eagles found dead or dying and determined that the majority of birds tested had low liver organochlorine levels (&lt; 5 mg/kg, N =59). A small proportion (&lt; 5 %) had levels of DDE, polychiorinated biphenyls (PCBs) and chiordane related compounds potentially diagnostic of acute poisoning. A larger proportion had PCDD/PCDF levels of possible concern; four of 19 eagles tested had TEQ5who &gt; 1000 rig/kg, all of which were adults in poor body condition found near pulp mills during the breeding season. In 1992, in ovo exposure to a gradient of environmental contaminants was studied by collecting eggs (N =25) for laboratory incubation. Hatching success was not significantly different between eggs from pulp mill versus reference sites. A hepatic cytochrome P450 1A (CYP1A) cross-reactive protein was induced sixfold in chicks from near a pulp mill at Powell River compared to those from a reference site (p &lt; 0.05); hepatic EROD and BROD activities were also significantly higher in chicks from pulp mill nests compared to reference sites (p &lt;0.0005 and p &lt; 0.02, respectively). Residual yolk sacs from near pulp mill sites had greater concentrations of 2,3,7,8-substituted PCDDs and PCDFs than reference areas. The hepatic CYP1A cross-reactive protein and EROD and BROD activities were positively correlated with concentrations of 2,3,7, 8-TCDD, 2,3,7,8-TCDF and toxic equivalents (TEQs) in yolk sacs. No concentration-related effects on histological or morphological parameters were found. Using hepatic CYP1A expression as a biomarker, a no-observed-effect-level (NOEL) of 100 ng/kg and a lowest-observed-effect-level (LOEL) of 210 ng/kg TEQ5WHO on a whole egg (wet weight basis) were suggested for Bald Eagle chicks. To investigate spatial patterns, trends and sources of contaminants to Bald Eagles, eggs were also collected during incubation, 1990-92, at the treatment and reference areas and analyzed for chlorinated hydrocarbons. Data on Bald Eagle avian and fish prey items from the study area were compiled and used as input to a bioaccumulation model. The model accurately predicted 2,3,7,8-TCDD levels in eagle eggs based on dietary concentrations, but was less accurate for other PCDDs and PCDFs. Using the LOEL levels in eagle eggs derived from the above study, concentrations of 2,3,7,8-TCDD in prey fish of 0.5 ng/kg and in fish-eating birds of 10 ng/kg are suggested as ecosystem guidelines to avoid TCDD-like toxicity in Bald Eagles. At all of the treatment and reference areas, Bald Eagle breeding success was measured for three years and blood samples of nestling eagles were collected for contaminant analysis. Average 3-year eagle productivity was high at most Strait of Georgia study sites, but was significantly lower at reference sites. Using nestling plasma lipid content as a marker of body condition, food supply appeared to be the main factor limiting eagle productivity on the British Columbia coast. However, at a sample of eagle nests adjacent to the dioxin fishery-closure zone near the pulp mill at Crofton, low productivity was probably not caused by low food availability. The cause of the low reproductive rate at Crofton has not been determined; however, a toxicological explanation has not been ruled out. Key Words: Bald Eagle, bioaccumulation, CYP1A, mortality, reproductive rate, 2,3,7,8- tetrachlorodibenzo—p-dioxin