Unlike large dams which favor methylation of Hg in flooded soils over long periods, run-of-river dams are designed to flood a limited area of soils and are therefore not expected to significantly affect mercury (Hg) cycling or carbon processing. We studied the Hg and carbon cycles within food webs from several sectors along the Saint-Maurice River, Quebec, Canada, that differ in how they are influenced by two run-of-river dams and other watershed disturbances. We observed peak Hg concentrations in fish five-year postimpoundment, but these levels were reduced three years after this peak. Methylmercury concentrations in low trophic level fish and invertebrates were related to their carbon source (δ¹³C) rather than their trophic positions (δ¹⁵N). Biomagnification, measured by trophic magnification slopes, was driven mainly by methylmercury concentrations in low-trophic level organisms and environmental factors related to organic matter degradation and Hg-methylation. River sectors, δ¹³C and δ¹⁵N, predicted up to 80% of the variability in food web methylmercury concentrations. The installation of run-of-river dams and the related pondages, in association with other watershed disturbances, altered carbon processing, promoted Hg-methylation and its accumulation at the base of the food web, and led to a temporary increase in Hg levels in fish.

中文翻译：

---

通过最近的河流溃坝影响的河流，通过营养转移和碳处理了解食物网中的汞累积

与大型水坝长期倾向于在淹没土壤中使甲基化的甲基汞不同，河道水坝设计用于淹没有限区域的土壤，因此预计不会显着影响汞（Hg）循环或碳加工。我们研究了加拿大魁北克省圣莫里斯河沿岸多个地区食物网中的汞和碳循环，它们在受到两个河道大坝和其他流域干扰的影响方式上有所不同。我们在蓄水五年后观察到鱼类中汞的峰值浓度，但是在峰值之后三年，这些汞含量降低了。在低营养水平鱼类和无脊椎动物甲基汞的浓度与他们的碳源（δ ¹³（C），而不是它们的营养位置δ ¹⁵N）。通过营养放大率斜率测量的生物放大率主要由低营养水平生物体中甲基汞的浓度以及与有机物降解和Hg甲基化有关的环境因素驱动。河扇区，δ ¹³ C和δ ¹⁵ N，预测到在食物网甲基汞浓度的变异性的80％。河流上游水坝的安装和相关池塘，与其他流域干扰相关，改变了碳的加工过程，促进了汞甲基化及其在食物网底部的积累，并导致了汞水平的暂时升高。鱼。