DISSERTATION RESEARCH: Mercury Bioavailability and its Environmental Controls in a River Network

汞是一种全球性污染物，通过食用鱼类和间接对野生动物产生不利影响而影响人类。汞的有机形式甲基汞是生物体最容易获得的形式，这使得甲基汞的产生成为决定水生生态系统中汞生物积累的最关键因素。然而，人们对溪流和河流中甲基汞产生的生态系统控制知之甚少。该研究将探讨丝状藻类介导甲基汞产生的速率和潜在机制，丝状藻类可能作为“热点”发挥作用。河流中汞的快速转化。具体而言，本研究将研究甲基汞的产生是否与河流生态系统中丝状藻类的生长阶段有关，在河流生态系统中，水文、食物网关系和生态系统过程从先前的研究中得到了很好的表征。本研究将通过原位汞甲基化率的测量以及微生物和光合作用的调控，阐明丝状藻类在天然河流中汞转化的关键生态因子。该项目整合了不同的科学学科，以了解一个高度复杂的环境问题-汞污染的生态系统调解。拟议的工作将提供关于汞在溪流和河流生态系统中的循环的基本知识。这一新知识可能使我们能够预测由于诸如森林砍伐和养分富集等土地利用改变的影响，水生食物网中汞供应的变化。此外，拟议的工作将通过实地样本收集和分析为研究生和本科生研究人员提供教育和研究机会。最后，这项拟议研究的结果将通过在科学会议上的演讲和在同行评议的期刊上发表来广泛传播。

Mercury is a global contaminant that affects humans through fish consumption and indirectly through adverse effects on wildlife species. The organic form of mercury, methylmercury, is the most readily available form to the organisms making the production of methylmercury the most critical factor determining mercury bioaccumulation in aquatic ecosystems. The ecosystem controls of methylmercury production in streams and rivers are poorly understood, however. The proposed research will investigate the rates and potential mechanisms mediating methylmercury production via filamentous algae, which may be functioning as ?hotspots? of rapid mercury transformations in rivers. Specifically, this research will examine whether the production of methylmercury is related to the growth stages of filamentous algae in a river ecosystem where hydrology, food web relationships and ecosystem processes are well characterized from previous studies. By measuring in-situ mercury methylation rates and manipulating both microbial and photosynthetic activities, this research will elucidate key ecological factors that mediate the role of filamentous algae in mercury transformations in natural rivers. The project integrates different scientific disciplines toward understanding a highly complex environmental issue - ecosystem mediation of mercury contamination. The proposed work will provide fundamental knowledge regarding the cycling of mercury in stream and river ecosystems. The new knowledge may allow the prediction of changes in availability of mercury to aquatic food webs in response to effects of altered land use such as forest clearing and nutrient enrichment. In addition, the proposed work will provide educational and research opportunities for a graduate student and undergraduate researchers through field sample collection and analyses. Lastly, the results from this proposed study will be widely disseminated through presentations in scientific meetings and publication in peer-reviewed journals.