Lepak Ryan F, Hoffman Joel C, Janssen Sarah E, Tate Michael T, Shanoff Morgann B, Mahon Michael B, Rumschlag Samantha L, Yarnes Christopher T, Lenell Brian A, Krabbenhoft David P, Ogorek Jacob M, Hurley James P
U.S. EPA Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Ecology and Toxicology Division, 6201 Congdon Blvd., Duluth, Minnesota 55804, United States.
Wisconsin Water Science Center, U.S. Geological Survey, 8505 Research Way, Middleton, Wisconsin 53562, United States.
Environ Sci Technol. 2025 Jun 17;59(23):11799-11808. doi: 10.1021/acs.est.5c01359. Epub 2025 Jun 6.
Atmospheric mercury (Hg) deposition has been declining in North America but remains the dominant delivery mechanism to the Great Lakes. The Lakes are highly efficient at bioaccumulating methylmercury, making the fish excellent sentinels for tracking shifts in atmospheric Hg deposition. Invasive mussels have altered biogeochemical processes, prey populations and fish dietary strategies asynchronously and to varied extents across the lower four lakes, impacting fish Hg exposure. To test if fish are adapting to new biogeochemical conditions, we analyzed a 40 year fish archive for carbon and nitrogen isotope ratios and amino acid-specific nitrogen isotope ratios. To assess Hg sources, we measured Hg isotope ratios. We reconstructed and compared energetic pathways that impact fish Hg concentrations to Hg-source trends. We found fish-Hg concentrations are declining but not monotonically due to ecological disturbances. Fish-Hg isotope values, unimpacted by ecological disturbance, confirm that sources of bioaccumulated Hg shift contemporaneously with changes in atmospheric Hg concentrations. Across Lakes, the degree of responsiveness to changes in atmospheric Hg concentrations mirrors the proportion of atmospheric-delivered Hg we previously modeled. Changes in both fish concentrations and fish isotope values outpace paleolimnetic reconstructions suggesting declines in atmospheric Hg concentrations impact fish Hg more than sediment.
在北美，大气汞（Hg）沉降一直在下降，但仍是五大湖汞的主要输送机制。五大湖在生物累积甲基汞方面效率极高，这使得鱼类成为追踪大气汞沉降变化的绝佳指示生物。入侵贻贝已经异步且在不同程度上改变了下四个湖的生物地球化学过程、猎物数量和鱼类饮食策略，影响了鱼类汞暴露。为了测试鱼类是否正在适应新的生物地球化学条件，我们分析了一个长达40年的鱼类样本库，以获取碳和氮同位素比率以及特定氨基酸的氮同位素比率。为了评估汞源，我们测量了汞同位素比率。我们重建并比较了影响鱼类汞浓度的能量途径与汞源趋势。我们发现鱼类汞浓度正在下降，但由于生态干扰并非呈单调下降。不受生态干扰影响的鱼类汞同位素值证实，生物累积汞的来源与大气汞浓度的变化同步转移。在各个湖泊中，对大气汞浓度变化的响应程度反映了我们之前模拟的大气输送汞的比例。鱼类浓度和鱼类同位素值的变化超过了古湖沼学重建结果，这表明大气汞浓度的下降对鱼类汞的影响大于对沉积物的影响。
