Temporal Trends of Contaminants in the Eggs of Two Aquatic Bird Species Collected from the St. Lawrence (1969-ongoing).
Environment and Climate Change Canada (ECCC) has been monitoring levels of persistent organic pollutants and heavy metals in seabird eggs collected from the St. Lawrence River and Gulf of St. Lawrence, Canada, since the end of 1960s. Two sentinel species were selected to monitor aquatic ecosystem health and contamination based on their elevated position in the food web and relatively limited feeding range; the northern gannet (Morus bassanus) and the great blue heron (Ardea herodias) (Champoux et al., 2002; 2006; 2010; 2015; 2016 – available in supplemental information section *).
Current avian monitoring is completed as part of the St. Lawrence Action Plan (2011-2026), a Canada-Quebec agreement that aims to conserve, restore, protect, and enhance the St. Lawrence (http:\/\/planstlaurent.qc.ca\/en.html). Pollutants monitored include legacy organochlorine pesticides (e.g. DDT, dieldrin, and mirex), polychlorinated biphenyls (PCBs), brominated flame retardants (e.g. polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane), dioxins and furans, and metals (mercury and selenium). Some of these compounds are now regulated under various national (the Canadian Environmental Protection Act http:\/\/www.ec.gc.ca\/lcpe-cepa\/) and international conventions; for example, the Stockholm Convention on Persistent Organic Pollutants (http:\/\/chm.pops.int\/TheConvention\/Overview\/tabid\/3351\/), the United Nations Economic Commission for Europe Long-range Transboundary Air Pollution Protocols (http:\/\/www.unece.org\/env\/treaties\/welcome.html), and the Minamata Convention on Mercury (http:\/\/www.mercuryconvention.org\/).
Freshly laid eggs were collected at Bonaventure Island, home to a large colony comprised of approximately 120,000 northern gannets, situated off the coast of the Gaspé Peninsula. Great blue heron eggs were sampled from over 30 colonies spanning the length of the St. Lawrence from Cornwall, ON to the Gulf (see attached map files for gannet and heron sampling locations*). Eggs were further processed either individually or as a single pool for chemical analyses, and archived in the National Wildlife Specimen Bank at the National Wildlife Research Centre (Ottawa, ON).
Overall, levels of organochlorines, PCBs, and mercury in gannet eggs have declined through time, and those levels that were still detected, were well below the threshold levels for adverse effects on reproduction and embryo development (Champoux et al., 2015). Similarly, levels of brominated flame retardants, dioxins and furans in gannet eggs also appear to be decreasing over time (Champoux et al., 2016). Levels of organochlorines, PCBs, mercury and brominated flame retardants declined in great blue heron eggs in most regions along the St. Lawrence River (Champoux et al., 2002; 2006; 2010; Champoux and Boily in preparation). Levels of contaminants in heron eggs are below threshold levels known to cause adverse effects in wildlife, however, the presence of anthropogenic contaminants at low levels may still constitute a risk for wildlife health when the cumulative effects of other environmental stressors like climate change, food availability, disturbance and habitat loss are accounted for (Champoux et al., 2002).
In addition to measuring contaminants, naturally-occurring stable isotopes of nitrogen (N15\/N14 or delta 15N) and carbon (C13\/C12 or delta 13C) were also measured in eggs of both species to verify whether shifts in trophic position and foraging area, respectively, could influence levels and trends of contaminants measured in eggs (Champoux et al., 2015). To date, in gannet eggs, no temporal trends have been observed, however both positive and negative temporal trends were observed in delta 15N delta 13C ratios in heron eggs, in various sections of the River (Champoux and Boily in preparation). Stable isotopes will continue to be monitored in tandem with egg contaminants monitoring.
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