CAREER: Quantifying the Extent and Biogeochemical Impact of Modern Ferruginous Lakes

许多小而深的湖泊是在一万年前覆盖北方大部分地区的大陆冰盖融化时形成的。氧气很难混入又小又深的湖泊中，这使它们成为“微生物世界”，因为大多数水生动物没有氧气就无法生存。该项目将测试这些缺氧的小湖泊是否也含有丰富的铁，以及铁是否来自周围的冰川沉积物。在没有氧气和丰富的铁的情况下，湖泊微生物可以从下沉的藻类或植物材料中产生甲烷。在湖泊附近使用路盐也可能导致湖泊停止混合，使产生甲烷的微生物的条件更好。这项工作将更好地了解湖泊形状，微生物和水化学如何促进湖泊甲烷排放，这是一个重要但尚未得到充分理解的天然温室气体排放到大气中的贡献者。这些湖泊的化学成分也与5亿年前的海洋相似，在动物出现之前，所以我们可以用它们来帮助了解过去海洋是否产生甲烷。本科生和研究生将收集来自明尼苏达州（MN）农村和城市地区湖泊的实地数据，作为课堂和研究考察的一部分。实地方法、调查结果和数据将通过传统（出版物和会议）和非传统（YouTube视频、维基百科页面）渠道共享。明尼苏达州明尼阿波利斯的研讨会将吸引不同的青年，包括毗邻城市研究湖的历史上的非裔美国人社区的居民。研讨会在伊塔斯卡州立公园，明尼苏达州，网站的农村湖泊，将从事参观公众和居民的周边县和附近的美洲原住民population centers.There只有22 ferruginous meromictic湖世界各地确定的文献，但做更多的存在？大多数公认的含铁部分分解湖泊都是冰后期的，地下水或泥炭地是假设但未经证实的铁来源。在明尼苏达州（MN）的两个领域领域的十几个冰后期湖泊将进行评估的meromixis和铁质条件，让深入了解土地利用的变化如何提高meromixis。将为两个湖泊构建详细的铁预算，以确定和量化铁源。许多含铁的裂殖湖泊有一个地下叶绿素的铁-氧氧化还原跃层的最大层，这一层的初级生产力和氧气生产的贡献将在两个湖泊量化。此外，产甲烷率，甲烷通量，甲烷对有机碳降解的贡献将在两个湖泊中进行量化，以更好地约束含铁条件下的碳通量。这些活动的结果将更好地描述：1）部分混合含铁湖泊的范围，2）地表和地下水库之间的水和元素通量，3）含铁条件下的碳循环，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准。

Many small, deep lakes formed during the melting of continental ice sheets that covered much of the northern hemisphere before 10,000 years ago. It is hard for oxygen to mix into small, deep lakes, which makes them “microbial worlds”, as most aquatic animals can’t live without oxygen. This project will test whether such small lakes that lack oxygen also contain abundant iron, and whether that iron is supplied from the surrounding glacial deposits. With no oxygen, and abundant iron, lake microbes can produce methane out of sinking algal or plant material. Road salt applications near lakes might also cause lakes that did mix to stop mixing, making conditions better for methane-producing microbes. This work will give a better idea how lake shape, microbes, and water chemistry contribute to lake emissions of methane, which is an important but not well-understood contributor to natural greenhouse gas emissions to the atmosphere. The chemistry of these lakes is also similar to the oceans before 500 million years ago, before animals appeared, and so we can use them to help understand if oceans were producing methane in the past. Undergraduate and graduate students will collect field data from lakes in a rural and urban area in Minnesota (MN) as part of class and research expeditions. The field methods, findings, and data will be shared through traditional (publications and conferences) and non-traditional (YouTube videos, Wikipedia pages) outlets. Workshops in Minneapolis, MN will engage diverse youth, including residents of a historically African American neighborhood adjacent to an urban study lake. Workshops in Itasca State Park, MN, the site of the rural lakes, will engage the visiting public and residents of surrounding counties and nearby Native American population centers.There are only 22 ferruginous meromictic lakes worldwide identified in the literature, but do more exist? Most of the recognized ferruginous meromictic lakes are postglacial, with groundwater or peatlands a hypothesized, but unverified source of iron. More than a dozen postglacial lakes in two field areas in Minnesota (MN) will be evaluated for meromixis and ferruginous conditions, giving insight into how land use changes enhance meromixis. Detailed iron budgets will be constructed for two lakes to identify and quantify iron sources. Many ferruginous meromictic lakes have a subsurface chlorophyll a maximum layer at the iron-oxygen redoxcline, and the contribution of this layer to primary productivity and oxygen production will be quantified in two lakes. Furthermore, rates of methanogenesis, methane fluxes, and the contribution of methane to the organic carbon degradation will be quantified in two lakes to better constrain carbon fluxes under ferruginous conditions. The results of these activities will better delineate 1) the extent of meromictic ferruginous lakes, 2) fluxes of water and elements between surface and groundwater reservoirs, 3) and carbon cycling under ferruginous conditions, which predominated in Earth's past oceans and influenced the oxidation of Earth's surface.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.