研究表明，在下一个十年时间里，水电产业可能让气候变化对北方生态系统的影响加剧，并让食用来自这些河口的北极海洋哺乳动物和鱼类的土著人口的健康面临风险。沿海的鱼类和海豹从各种来源得到甲基汞（MeHg）这种强效神经毒素，但是北极河流与海冰融化的淡水流的增加以及与水电开发有关的洪水，是否可能增加甲基汞（MeHg）浓度，这仍不清楚。Amina T. Schartup及其同事研究了加拿大拉布拉多地区梅尔维尔湖的亚北极地区的甲基汞（MeHg）制造和生物积累的环境驱动因素。这组作者测量了沿着从淡水区到外拉布拉多海不断增加的盐度梯度的海水、海底沉积物以及浮游动物样本的汞与甲基汞（MeHg）浓度。这些发现揭示出了生活在分层的海水——表面的盐含量低，在深处的盐含量高——中的浮游动物比在中纬度生态系统中的生物积累了更多的甲基汞（MeHg）。这些发现很可能是由于被称为海洋雪的一个有机物薄层造成的，它浓缩了微生物甲基化，而且还可能是由于在一个相对小的区域中的食草和食肉浮游动物的存在。这组作者说，这些发现提示，水电产业建立的蓄水库可能在未来十年时间里增加河口的甲基汞（MeHg）浓度达25%到200%，这超过了气候变化预计造成的影响。

　　Amina T. Schartup;Prentiss H. Balcom; Anne Soerensen; et al.

　　Elevated levels of neurotoxic methylmercury in Arctic food-webs pose health risks for indigenous populations that consume large quantities of marine mammals and fish. Estuaries provide critical hunting and fishing territory for these populations, and, until recently, benthic sediment was thought to be the main methylmercury source for coastal fish. New hydroelectric developments are being proposed in many northern ecosystems, and the ecological impacts of this industry relative to accelerating climate changes are poorly characterized. Here we evaluate the competing impacts of climate-driven changes in northern ecosystems and reservoir flooding on methylmercury production and bioaccumulation through a case study of a stratified sub-Arctic estuarine fjord in Labrador, Canada. Methylmercury bioaccumulation in zooplankton is higher than in midlatitude ecosystems. Direct measurements and modeling show that currently the largest methylmercury source is production in oxic surface seawater. Water-column methylation is highest in stratified surface waters near the river mouth because of the stimulating effects of terrestrial organic matter on methylating microbes. We attribute enhanced biomagnification in plankton to a thin layer of marine snow widely observed in stratified systems that concentrates microbial methylation and multiple trophic levels of zooplankton in a vertically restricted zone. Large freshwater inputs and the extensive Arctic Ocean continental shelf mean these processes are likely widespread and will be enhanced by future increases in water-column stratification, exacerbating high biological methylmercury concentrations. Soil flooding experiments indicate that near-term changes expected from reservoir creation will increase methylmercury inputs to the estuary by 25–200%, overwhelming climate-driven changes over the next decade.

　　（来源：PNAS, 2015, DOI:10.1073/pnas.1505541112）