The St. Lawrence River in Eastern Ontario, Canada, has been a designated an area of concern due to past industrial contamination of sediment in some areas and transport of mercury from tributaries. Previous research using bats as sentinel species identified elevated concentrations of total mercury (THg) in fur of local bats and species-specific variation between little brown bats (Myotis lucifugus) and big brown bats (Eptesicus fuscus). Here, we investigated the mercury exposure pathways for these two species by testing the hypothesis that diet variation, particularly the reliance on aquatic over terrestrial insects, is a determinant of local bat mercury concentrations. We analyzed THg concentration and stable isotope ratios of δ¹⁵N and δ¹³C in fur of little and big brown bats, and in aquatic and terrestrial insects. Big brown bats, especially males, accumulated significantly higher THg concentrations in their fur compared to little brown bats. However, this difference was not related to diet because big brown bats consumed terrestrial insects, which were lower in mercury than aquatic insects, the primary prey for little brown bats. We also evaluated whether fur THg concentrations translate into molecular changes in tissues linked to (methyl)mercury toxicity by quantifying tissue changes in global DNA methylation and mitochondrial DNA abundance. No significant changes in DNA molecular markers were observed in relation to fur THg concentration, suggesting mercury exposure to local bats did not impact molecular level changes at the DNA level. Higher mercury in bats was not associated with local aquatic contamination or genotoxicity in this study area.

加拿大安大略省东部的圣劳伦斯河由于过去一些地区的沉积物受到工业污染以及支流中的汞输送而被指定为关注区域。先前使用蝙蝠作为哨兵物种的研究发现，当地蝙蝠毛皮中的总汞 (THg) 浓度升高，以及小棕蝠 ( Myotis lucifugus ) 和大棕蝠 ( Eptesicus fuscus )之间的物种特异性差异。在这里，我们通过测试以下假设来研究这两个物种的汞暴露途径：饮食变化，特别是对水生昆虫而非陆生昆虫的依赖，是当地蝙蝠汞浓度的决定因素。我们分析了小棕色蝙蝠和大棕色蝙蝠的皮毛以及水生和陆生昆虫的 THg 浓度和 δ ¹⁵ N 和 δ ¹³ C稳定同位素比率。与小棕色蝙蝠相比，大棕色蝙蝠，尤其是雄性，其皮毛中积累的 THg 浓度明显更高。然而，这种差异与饮食无关，因为大棕色蝙蝠吃陆生昆虫，而这些昆虫的汞含量低于小棕色蝙蝠的主要猎物水生昆虫。我们还通过量化整体 DNA 甲基化和线粒体 DNA 丰度的组织变化，评估毛皮 THg 浓度是否转化为与（甲基）汞毒性相关的组织分子变化。没有观察到与毛皮 THg 浓度相关的 DNA 分子标记的显着变化，这表明当地蝙蝠接触汞不会影响 DNA 水平的分子水平变化。蝙蝠体内较高的汞含量与该研究区域的当地水生污染或遗传毒性无关。