John E. Elliott

Heavy metal and metallothionein concentrations in Atlantic Canadian seabirds

Seabird tissues, collected during the 1988 breeding season from colonies on the Atlantic coast of Canada, were analyzed for toxic metals—Cd, Hg and Pb—and 18 other trace elements. Metallothionein (MT) was measured in kidney, and kidneys and livers underwent histopathological examination. Levels of most essential trace elements appear to be closely regulated in seabird tissues; values were in good agreement with those previously reported in the published literature. Liver-Se concentrations in Leachs storm-petrels (Oceanodroma leucorhoa) (77.6+7.49 μg/g dry weight) were much higher than values normally reported for freeliving birds and mammals. Cd levels varied greatly among individuals, but were always higher in kidney than in liver. Highest mean Cd concentrations (183+65 μg/g dry weight) were in kidneys of the planktivorous Leachs storm-petrels from the Gulf of St. Lawrence. A few individuals of this species had values >300 μg/g dry weight. Cd and metallothionein (MT) concentrations were positively correlated in kidneys of Leachs storm-petrels (r=0.692), Atlantic puffin (Fratercula arctica) (r=0.845) and herring gull (Larus argentatus) (r=0.866). Concentrations of total Hg varied greatly among species and individuals, but were consistently higher in liver than in kidney. Highest mean levels (21+28 μg/g) were in livers of the piscivorous double-crested cormorant (Phalacrocorax auritus) from Saint John Harbour in the Bay of Fundy. Concentrations of Hg and Se were positively correlated (r=0.736) in livers of Leachs storm-petrel, but not in other species. Pb concentrations were consistently greatest in bone, with mean levels being highest in herring gulls from a colony in the Bay of Fundy (63+36 μg/g). Histological examination of liver and kidney failed to reveal indications of tissue damage associated with elevated levels of heavy metals.

Environmental contaminants and reproductive success of great blue herons Ardea herodias in British Columbia, 1986–1987

In 1986, eggs were collected and productivity estimated at four great blue heron (Ardea herodias) colonies on the coast of British Columbia. Polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were present in all eggs in a qualitatively similar pattern among colonies. PCDD levels were significantly elevated at a colony near a kraft pulp mill at Crofton on Vancouver Island, although there was no correlation between the number of young raised in a nest and levels of either PCDDs, PCDFs, PCBs, organochlorine pesticides or mercury. In 1987, heron productivity was normal at three colonies, while the colony at Crofton failed to raise any young. A normal complement of eggs were apparently laid in about 57 nests, but during incubation they were destroyed and the broken eggshells were found in and beneath the nests. Analysis of eggs salvaged from nests showed that 2378-TCDD levels were about three times higher in 1987 than in 1986. At a colony in Vancouver, 2378-TCDF levels were significantly higher in 1987 than 1986 eggs. Levels of organochlorine pesticides and total mercury in eggs were generally low; highest residue levels were found in two mainland colonies, particularly at one adjacent to an agricultural area. Total PCB levels were low and did not differ significantly among locations. Analysis of PCB congener ratios indicated different sources of PCBs. Regurgitated prey samples collected in 1986 from four locations had generally low levels of PCDD, PCDF, mercury, lead and cadmium contamination.

Second generation anticoagulant rodenticides in predatory birds: Probabilistic characterisation of toxic liver concentrations and implications for predatory bird populations in Canada.

Second-generation anticoagulant rodenticides (SGARs) are widely used to control rodent pests but exposure and poisonings occur in non-target species, such as birds of prey. Liver residues are often analysed to detect exposure in birds found dead but their use to assess toxicity of SGARs is problematic. We analysed published data on hepatic rodenticide residues and associated symptoms of anticoagulant poisoning from 270 birds of prey using logistic regression to estimate the probability of toxicosis associated with different liver SGAR residues. We also evaluated exposure to SGARs on a national level in Canada by analysing 196 livers from great horned owls (Bubo virginianus) and red-tailed hawks (Buteo jamaicensis) found dead at locations across the country. Analysis of a broader sample of raptor species from Quebec also helped define the taxonomic breadth of contamination. Calculated probability curves suggest significant species differences in sensitivity to SGARs and significant likelihood of toxicosis below previously suggested concentrations of concern (<0.1mg/kg). Analysis of birds from Quebec showed that a broad range of raptor species are exposed to SGARs, indicating that generalised terrestrial food chains could be contaminated in the vicinity of the sampled areas. Of the two species for which we had samples from across Canada, great horned owls are exposed to SGARs to a greater extent than red-tailed hawks and the liver residue levels were also higher. Using our probability estimates of effect, we estimate that a minimum of 11% of the sampled great horned owl population is at risk of being directly killed by SGARs. This is the first time the potential mortality impact of SGARs on a raptor population has been estimated.

Comparison of polychlorinated dibenzodioxin levels with hepatic mixed‐function oxidase induction in great blue herons

As part of the Canadian Wildlife Service monitoring of great blue herons in British Columbia, eggs were collected from three colonies with low, intermediate, and high levels of PCDD and PCDF contamination: Nicomekl, Vancouver, and Crofton, respectively. One egg from each nest was used for chemical analysis by GC-MS; the others were hatched. Liver microsomes were prepared from the heron chicks and used for determination of cytochrome P-450-dependent activities. No erythromycin N-demethylase activity was found in any sample. Ethoxyresorufin O-dealkylase activity in the Nicomekl group was similar to that in pigeons, a control altricial species. The ethoxyresorufin activity in the herons from the Crofton colony was 2.6-fold higher than in the Nicomekl group. The Vancouver colony was intermediate. No difference among the three heron colonies was found in pentoxyresorufin O-dealkylase activity, although levels were 20-33 times that in the pigeon. Chemical analysis was carried out on paired heron eggs. Vancouver and Crofton eggs contained 13.5 and 21 times the levels of 2,3,7,8-TCDD compared to the Nicomekl group. The Crofton eggs contained higher levels of several other contaminants also. A highly significant correlation (p less than .001) was found between ethoxyresorufin O-dealkylase and 2,3,7,8-TCDD concentrations. The correlation coefficient did not change when ethoxyresorufin O-dealkylase was compared to total chemical contamination using several toxic equivalency factors. Multiple regression analysis resulted in only one predictor variable for ethoxyresorufin O-dealkylase: 2,3,7,8-TCDD.

Tracking Marine Pollution

Seabird monitoring studies are providing a global picture of an increasing range of marine pollutants. Visit a beach almost anywhere and you will see plastic waste floating in the water and heaped above the tide lines. That debris is both a source and an overt signal of the even more pervasive contamination of marine biota by persistent chemicals. Present at ultra-trace levels but often highly toxic, chemical pollutants can be challenging to measure and understand. As the most problematic compounds biomagnify in food chains, sampling of marine top predators yields a global picture of ocean pollution.

Brodifacoum Poisoning of Avian Scavengers During Rat Control on a Seabird Colony

Langara Island, at the north-western tip of British Columbias Queen Charlotte archipelago, was once nesting grounds for an estimated 500,000 seabirds. However, infestations of Norway rats (Rattus norvegicus) and their predation of eggs and breeding adults have caused extirpation or serious declines of all seabird species. By 1993, the breeding population of ancient murrelets (Synthliboramphus antiquus) had declined to 10% of its historical size. Successful eradication of rats on smaller New Zealand islands using the anticoagulant brodifacoum prompted its application on Langara Island. The island is also home to breeding bald eagles (Haliaeetus leucocephalus), peregrine falcons (Falco peregrinus), and other wildlife. No comprehensive studies of non-target impacts and potential for secondary poisoning were done during similar operations elsewhere; thus, in 1994 and 1995 we initiated a two-year study into the risk of secondary poisoning to non-target species. During 1994, rat carcasses were laid out with motion sensor cameras to identify potential scavengers. Ravens, northwestern crows and bald eagles were photographed at carcasses, and therefore at risk of feeding on rats that die above ground. During the baiting program, 19 rats were radio-tagged to determine the proportion dying above ground, and thus available to predators/scavengers. Ravens were found poisoned both from feeding directly on the bait, and predating/scavenging poisoned rats. Bald eagles were trapped and blood sampled for brodifacoum residue analysis and prothrombin time evaluation; 15% of the sampled population showed detectable residues but no adversely-affected birds were found. We conclude that the use of brodifacoum for rat removal on seabird islands poses a clear risk of secondary poisoning to avian scavengers. This risk must be weighed against the benefit of rat removal programs.

Monitoring biological effects of polychlorinated dibenzo‐p‐dioxins, dibenzofurans, and biphenyls in great blue heron chicks (Ardea herodias) in British Columbia

The Canadian Wildlife Service monitors levels of polychlorinated aromatic hydrocarbons in great blue heron (Ardea herodias) eggs in British Columbia as indicators of environmental contamination. The present project assessed the temporal effects of environmental contamination with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) on hepatic microsomal ethoxyresorufin O-deethylase (EROD) activities and several morphological parameters in heron hatchlings. Between 1990 and 1992, eggs were collected from two great blue heron colonies in British Columbia that had elevated levels of contamination in 1988: Vancouver in 1990 and 1992, and Crofton in 1991. Biological parameters in the hatchlings and chemical contaminant levels in matched eggs from the same clutch were measured and compared with the findings from the same colonies studied in 1988. Levels of TCDD and other PCDDs and PCDFs had decreased significantly in both colonies since 1988. A concomitant decrease in EROD activity and incidence of chick edema, increase in body weight, and improvement of the reproductive success of the Crofton colony was observed. Body, yolk-free body, stomach, and intestine weights, tibia wet, dry, and ash weights, and tibia length regressed negatively on TCDD level (p < .01; n = 54). Hepatic EROD activity regressed positively on TCDD level (r2 = .49; p = .00005; n = 54). Regression of these parameters on the sum of TCDD toxic equivalents (TEQ) resulted in similar relationships. The reduction in severity of the effects observed in the contaminated colonies in the recent collections, accompanied by the declines in levels of PCDDs and PCDFs, was consistent with the dose-response relationships determined in 1988.

PCBs and DDE, but not PBDEs, increase with trophic level and marine input in nestling bald eagles

Concentrations of persistent contaminants often vary widely among individuals within a population. We hypothesized that such variation was caused mainly by differences in diet (biomagnification) and in coastal systems by the tendency of marine systems to act as contaminant sinks. We examined the relationship between contaminant concentrations and stable isotope ratios in nestling plasma from an apex predator with a particularly broad diet. Our study included freshwater, estuarine, inshore and pelagic breeding sites. Bald eagles (Haliaeetus leucocephalus) at the pelagic marine sites showed high trophic level and marine input, eagles at the freshwater sites showed low trophic level and marine input, and eagles at the estuarine and inshore marine sites had intermediate values. The relationship between trophic level and marine input may reflect longer food chains in pelagic compared to terrestrial ecosystems. summation operator PCBs and DDE concentrations generally increased with trophic level and marine input, with the exception of the freshwater sites, while summation operator PBDEs, hydroxylated-PBDEs and hydroxylated-PCBs increased with marine input, but were independent of trophic level. The relationships for summation operator PCBs and DDE were often slightly stronger with marine input than trophic level, suggesting that oceanographic processes may be more important than trophic level. At freshwater locations, spatial variation may be more important than trophic level due to the heterogeneity of contaminant profiles between feeding locations (lakes, rivers, agricultural fields). Adults had similar isotopic composition to their chicks but higher contamination. Based on nests where prey composition was determined independently, isotopic enrichment values for nestling plasma were 1.6+/-0.1 (delta(15)N) and -0.4+/-0.2 (delta(13)C). We conclude that trophic level and marine influence are significant factors influencing PCB and DDE concentrations in eagles. However, trophic level in particular did not influence PBDEs, possibly due to their being metabolized by eagles.

Organochlorines and eggshell thinning in Northern gannets (Sula bassanus) from Eastern Canada 1968-1984

The northern gannets (Sula bassanus) nesting on Bonaventure Island, Quebec, were studied from 1968 to 1984 in order to measure environmental contaminant levels and their relationship to productivity. Fresh eggs in 1969 contained a mean DDE level of 18.5 mg kg(-1) and had shells which were 17% thinner than pre-1947 samples. Unhatched eggs in 1969 had no outer calcified layer, a mean thickness 20% less than the pre-1947 mean, and mean DDE concentration of 30.6 mg kg(-1). Significantly higher levels of eight contaminants were measured in unhatched than in fresh eggs collected in 1969. DDE and shell thinning were also intercorrelated with nine other contaminants; these data strongly implicate toxic chemicals, particularly DDE, as the main cause for the low breeding success of Bonaventure gannets from 1966 to 1974. Extensive use of DDT to control forest insects around the Gulf of St Lawrence ceased in 1969. Use of DDT, dieldrin and PCBs was restricted in North America during the early 1970s. Residues of DDT, DDD, DDE, PCBs, dieldrin, HCB and chlordane-related compounds in gannet eggs decreased significantly during this study. Heptachlor epoxide remained constant while alpha-HCH appeared to increase. Estimated half-lives ranged from 3.1 years for DDD to 35.4 years for oxychlordane. The breeding success and population of the colony have coincidentally increased.

Heavy metal and metallothionein concentrations in seabirds from the Pacific coast of Canada

Seabird tissues, collected during the 1990 breeding season from colonies on the Pacific coast of Canada, were analysed for Cd, Hg, Pb and 19 other trace elements. Metallothionein (Mt) was measured in kidneys of three species. Ranges of essential trace metal concentrations were generally narrow, consistent with homeostatic control of these elements in seabird tissues. Cadmium concentrations were always higher in kidney than in liver. Highest mean Cd concentrations (306±78 μg g−1 dry wt) were in kidneys of planktivorous Leachs storm-petrels (Oceanodroma leucorhoa) from Hippa Island in the Queen Charlotte archipelago. Cadmium concentrations in kidneys of both Leachs storm-petrels and rhinoceros auklets (Cerorhinca monocerata) were significantly greater at northern colonies compared to those further south. Cadmium and Mt concentrations were positively correlated in kidneys across the three species for which measurements were made [rhinoceros auklet, Cassins auklet (Ptychoramphus aleuticus), and ancient murrelet (Synthliboramphus antiquus)] with an overall r = 0.82, p < 0.001. Mercury accumulation was not sufficiently great to be of toxicological concern in any of the 5 species. Highest mean Hg concentrations (6.37 μg g−1) were in livers of Leachs storm-petrels from Cleland Island on the west coast of Vancouver Island, and were significantly greater than in birds from further north on Hippa Island. Concentrations of hepatic Hg and Se were not correlated in the three species (rhinoceros auklet, Cassins auklet and ancient murrelet) for which Se was measured. Lead concentrations were consistently greatest in bone, with highest mean concentrations in fork-tailed storm-petrels (Oceanodroma furcata) (6.2 μg g−1 dry wt).