The Linkage between Copper Speciation and Nitrogen Cycling in Stratified Lakes

稀有金属可以通过限制关键浮游生物物种或群落的生长或功能，对生物地球化学循环产生不成比例的影响。众所周知，铁限制了世界海洋中高硝酸盐、低叶绿素区域的初级生产力，这可能对全球碳循环产生重要影响。淡水环境中微量元素金属的限制问题在很大程度上尚未得到探讨。本研究旨在初步探讨分层湖泊中溶解铜的形态（及其反应性和生物利用度）对细菌反硝化作用的影响。我们建议研究这个具体的例子作为一个起点，以探索微量金属对主要水生生物地球化学循环的影响这一更广泛的一般性问题。该系统的目标是：(1)对Cu的形态及其在一些淡水中的低生物利用度进行了充分的研究，(2)Cu对影响反硝化的细菌酶的基本性质，(3)分层湖作为自然大规模间歇式反应器实验的效用，以及(4)现有的间接证据表明Cu可以限制实验室培养物中的反硝化作用，并且反硝化中间体（特别是N2O）在许多分层湖中积聚。虽然这样的系统是一个合乎逻辑的起点，但这项研究的结果可能对包括湖泊、河流和地下水在内的淡水中微量营养素限制的主题具有更广泛的影响。更广泛的影响拟议的研究将在三个不同的方面产生更广泛的影响。(1)促进教学、培训和学习：湖泊特别适合作为讲授地球科学原理的例子，因为湖泊是人们熟悉的系统，其中的化学和物理过程被清楚而简单地表达出来。耶鲁大学环境学院拥有大约220名硕士研究生，他们通常会从事环境政策和管理方面的职业，而不是科学方面的职业，但他们渴望了解环境科学的基本原理。本研究为该群体的教学和培训提供了一个理想的机会。结果将纳入生物地球化学与污染、野外环境分析方法、水生生态学三门课程的课程。此外，两名获得学院研究助理奖学金的硕士生将直接参与研究。(2)扩大弱势群体的参与：本项目支持的两位最有可能的博士生候选人都是女性。如果被选中，其中任何一个都将在研究中发挥重要作用。(3)社会效益：本研究解决了对公共福利相当重要的两个环境化学问题：微量金属和氮循环之间可能存在的联系。金属通常引起人们的兴趣，因为它们可能对湖泊和溪流产生有害影响。在这里，我们考虑它们是否也可以作为限制微量营养素。氮循环涉及许多社会关注的问题，包括富营养化（来自过量的NO3-）、作为温室气体的N2O、酸沉积（HNO3）和人为干预引起的扰动（据估计，全球50%的氮固定来自工业）。

0337201BenoitScarce metals can have a disproportionate influence on biogeochemical cycles by limiting growth or function of key planktonic species or assemblages. It is already known that Fe limits primary productivity in high-nitrate, low-chlorophyll regions of the world's oceans, with potentially important consequences for global carbon cycling. Largely unexplored is the question of limitation in fresh water environments by micronutrient metals. This proposal is for preliminary research to investigate the influence of dissolved Cu speciation (and consequent reactivity and bioavailability) on denitrification by bacteria in stratified lakes. We propose to study this specific example as a starting point to explore the much broader general question of the influence of trace metals on major aquatic biogeochemical cycles. This system is targeted because of: (1) the well-studied speciation of Cu and its low bioavailability in some fresh waters, (2) the essential nature of Cu for bacterial enzymes that effect denitrification, (3) the utility of stratified lakes as natural, large-scale batch reactor experiments, and (4) existing circumstantial evidence that Cu can limit denitrification in lab cultures, and that denitrification intermediaries (esp. N2O) build-up in many stratified lakes. While such systems represent a logical starting point, the results of this research could have much broader implications on the topic of micronutrient limitation in fresh waters, including lakes, rivers, and ground waters.Broader Impacts The proposed research will have broader impacts in three separate ways. (1) Promoting Teaching, Training and Learning: Lakes are especially well-suited as examples for teaching principles of geosciences, because they are familiar systems in which chemical and physical processes are clearly and simply expressed. Yale's Environment School is home to about 220 masters students who are often going on to careers in environmental policy and management, rather than science, but are eager to obtain an understanding of the fundamental principles of environmental science. The proposed research provides an ideal opportunity for teaching and training this group. Results will be incorporated into the curriculum of three courses: Biogeochemistry and Pollution, Methods of Field Environmental Analysis, and Aquatic Ecology. In addition, two master's students receiving Research Assistantships from the School will be directly involved in the research. (2) Broadening Participation of Underrepresented Groups: The two most likely candidates for the PhD student supported by this project are both women. Either would play a major role in the research if selected. (3) Benefits to Society: This research addresses the possible linkage of two environmental chemical issues of considerable importance to public welfare: trace metals and the nitrogen cycle. Metals have generally been of interest because of possible harmful effects in lakes and streams. Here we consider whether they may also function as limiting micronutrients. The nitrogen cycle involves a number of issues of societal concern, including eutrophication (from excess NO3-), N2O as a greenhouse gas, acid deposition (HNO3), and perturbations caused by human intervention (50% of global N fixation is estimated to be industrial).