Some populations of common terns (Sterna hirundo) breeding at inland lakes in North America are declining, including the Laurentian Great Lakes. Terns nesting at inland colonies forage in freshwater during the breeding season and primarily in coastal marine environments during the nonbreeding season. As piscivores, they are susceptible to dietary Hg exposure. To characterize patterns of Hg exposure in this population, we 1) quantified within and among season differences in total mercury (THg) concentrations (μg/g) in blood and feathers at 2 Lake Superior breeding colonies, and 2) documented spatial and temporal variation in exposure by studying adult foraging ecology using geospatial tracking devices and stable isotopes. We used general linear models to assess the relationship between isotopic composition and THg concentrations in bird tissues relative to sex, age, colony location, and season. The THg concentrations were lowest in winter‐grown feathers (geometric mean [95% confidence limits]): 1.32 (1.09–1.59) μg/g dw (n = 60), higher at the more industrially influenced colony (chick feathers: 4.95 [4.62–5.37] μg/g dw [n = 20]), and increased with a riverine‐based diet. During the breeding season, Hg exposure varied along a gradient from lake to river, with adult females having lower blood THg concentrations than males (females: 0.83 [0.67–1.03]) μg/g ww (n = 7); males: 1.15 (0.92–1.45) μg/g ww (n = 5). Stable isotope values suggested adults obtained 42 ± 12% (n = 12) of their diet from the river during incubation, which was validated with tracking data. During chick‐rearing, chicks obtained 68 ± 19% (n = 44) of their diet from the river. Our results indicate colony location, foraging behavior, and season influenced Hg exposure for these Lake Superior colonies and underscores the importance of local contamination with respect to exposure. Integr Environ Assess Manag 2021;17:398–410. © 2020 SETAC

中文翻译：

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觅食生态区分普通燕鸥的生命阶段和汞暴露 (Sterna hirundo)

一些常见的燕鸥种群（Sterna hirundo) 北美内陆湖泊的繁殖正在下降，包括劳伦森五大湖。在内陆殖民地筑巢的燕鸥在繁殖季节在淡水中觅食，在非繁殖季节主要在沿海海洋环境中觅食。作为食鱼动物，它们容易受到饮食中汞的影响。为了描述该人群中汞暴露的模式，我们 1) 量化了苏必利尔湖 2 个繁殖区血液和羽毛中总汞 (THg) 浓度 (μg/g) 的季节内和季节差异，以及 2) 记录了空间和时间变化通过使用地理空间跟踪设备和稳定同位素研究成年觅食生态的暴露。我们使用一般线性模型来评估鸟类组织中同位素组成和 THg 浓度与性别、年龄、菌落位置和季节之间的关系。n  = 60），在受工业影响较大的群体中更高（鸡羽毛：4.95 [4.62-5.37] μg/g dw [ n  = 20]），并随着以河流为基础的饮食而增加。在繁殖季节，汞暴露量从湖泊到河流呈梯度变化，成年雌性的血液总汞浓度低于雄性（雌性：0.83 [0.67-1.03]）μg/g ww（n  = 7）；男性：1.15 (0.92–1.45) μg/g ww ( n  = 5)。稳定的同位素值表明成年人在孵化期间从河流中获得了 42 ± 12% ( n  = 12) 的饮食，这已通过跟踪数据得到验证。在雏鸡饲养期间，雏鸡获得 68 ± 19% ( n = 44) 他们的饮食来自河流。我们的结果表明，这些苏必利尔湖群落的群落位置、觅食行为和季节影响了汞暴露，并强调了局部污染对暴露的重要性。2021 年整合环境评估管理；17:398–410。© 2020 SETAC