Broadwing Biological Consulting, 1944 Parkside Drive, Pickering, ON, L1V 3N5, Canada.
Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, Burlington, ON, L7S 1A1, Canada.
Ecotoxicol Environ Saf. 2019 Dec 30;186:109736. doi: 10.1016/j.ecoenv.2019.109736. Epub 2019 Oct 22.
Overwintering canvasbacks were collected in the Lake St. Clair region of the Great Lakes in the winter of 2008/09 and livers were analyzed for organochlorines, mercury (Hg), and selenium (Se). We found dramatic increases in hepatic concentrations of Hg, Se, sum PCBs, p,p'-DDE, and other organochlorines in canvasbacks in which concentrations in February were greater than concentrations in November when overwintering ducks arrived in the study area. Increases in contaminant burdens were generally greatest between December and January which also coincided with the period when ducks from Lake St. Clair (LSC) moved following freeze-up of the Lake to forage on the St. Clair River (SCR), an area of known historic contamination, and upstream of LSC. Body condition estimated using body metrics and measured using lipid reserves (after controlling for body size) increased in LSC ducks but subsequently decreased in SCR ducks. This rapid loss of body condition through loss of lipid reserves was one factor likely driving the dramatic increase in contaminant burdens and particularly for organochlorines which were inversely related to body condition in SCR ducks. Increased exposure due to foraging in closer proximity to contaminant sources and changes in diet associated with the movement of ducks may have also contributed to temporal trends. Concentrations overall were below those associated with toxicity with the exception of Se for which 30% of ducks exceeded the Se threshold that is considered elevated and one duck exceeded the threshold associated with possible toxicity. Fitness consequences of reduced lipid reserves include reduced survival, delayed migration, reduced breeding propensity, and transfer of contaminant burdens to eggs. Food availability, ice cover, and movements of canvasbacks are additional factors influencing contaminant accumulation and lipid reserves in waterfowl utilizing this important wintering location.
2008/09 年冬季，在大湖区的圣克莱尔湖地区收集了越冬的鸭，并分析了它们的肝脏中有机氯化合物、汞（Hg）和硒（Se）的含量。我们发现，2 月份肝脏中 Hg、Se、总 PCB、p,p'-DDE 和其他有机氯化合物的浓度在越冬鸭中急剧增加，而这些鸭在 11 月到达研究区域时的浓度较低。污染物负荷的增加通常在 12 月至 1 月之间最大，这也与圣克莱尔湖（LSC）的鸭子在湖面冻结后移往圣克莱尔河（SCR）觅食的时期相吻合，圣克莱尔河是一个已知存在历史污染的地区，位于 LSC 的上游。使用身体指标估计的身体状况，并通过测量脂质储备（在控制身体大小后），LSC 鸭的状况有所改善，但随后 SCR 鸭的状况却下降了。通过脂质储备的损失导致身体状况迅速下降，这可能是污染物负荷急剧增加的一个因素，特别是对 SCR 鸭的有机氯化合物，它们与身体状况呈反比。由于更接近污染物源觅食而增加的暴露，以及与鸭子移动相关的饮食变化，也可能导致了时间趋势。总的来说，除了 Se，其浓度都低于与毒性相关的浓度，30%的鸭子超过了被认为升高的 Se 阈值，一只鸭子超过了与可能毒性相关的阈值。脂质储备减少的后果包括生存能力降低、迁徙延迟、繁殖意愿降低以及将污染物负荷转移到蛋中。食物供应、冰层覆盖和鸭的移动是影响在这个重要越冬地利用的水禽中污染物积累和脂质储备的其他因素。
