EAGER: Discovering how geologic and fossil methane sources support a contemporary river ecosystem

碳是生命的基本组成部分。对于溪流和湖泊中的大多数动物(昆虫、鱼、浮游生物)来说，碳最初以二氧化碳的形式存在，然后被藻类和植物捕获。然后，这些碳传递给浮游生物、昆虫和鱼类。最近的研究表明，河流中可能存在其他碳源，如支持水生植物和藻类的甲烷。然而，人们对这种甲烷的来源以及它如何融入河流、溪流和湖泊中的生命知之甚少。甲烷可能会被释放到地质或地热活动较高地区的地下水和溪流中。这个热切的奖项将进行第一次研究，探索地质和化石甲烷作为一种替代碳源在支持河流泛滥平原生命方面的作用。该奖项还将支持对学生和博士学者的研究培训，让鱼类孵化场管理人员参与公民科学研究，并向公众提供河流系统如何发挥作用的知识。地球上大多数生态系统的基本假设是，现代二氧化碳的固定推动了生产力和生物多样性，几乎没有认识到或研究其他潜在的碳途径(例如甲烷)是生产力和生物多样性的驱动力。尽管化石和地质甲烷可能对淡水系统做出贡献，甲烷有可能从生态上转化为危害较小的形式，但影响这一温室气体来源的淡水生物过程鲜为人知。这个急切的奖项将调查非生物、产热和化石产甲烷补贴在支持淡水泛滥平原生态系统方面的作用，方法是为碳有限的浅层含水层食物网(深层地下含水层带)提供碳源。该奖项的目的是量化各种甲烷来源的碳对含水层食物网的贡献。将使用创新的稳定同位素方法来评估碳源并通过泛滥平原食物网进行追踪，然后开发新的方法来发现甲烷来源对淡水生态系统的贡献。这项研究可能会改变目前以二氧化碳为基础的推动生产力和生物多样性的范式，因为它证明了河流泛滥平原下面的浅含水层食物网是由地质和化石甲烷衍生的碳驱动的。因此，这些泛滥平原含水层将是第一个展示概念和生态上类似于海洋热液喷口生态系统的范例。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Carbon is a fundamental building block of life. For most animals (insects, fish, plankton) in streams and lakes the carbon starts out as carbon dioxide and then is captured by algae and plants. This carbon then passes on to plankton, insects, and fish. Recent studies suggest there might be other sources of carbon in rivers such as methane that are supporting aquatic plants and algae. However, little is known about the sources of this methane and how it gets incorporated into the life in rivers, streams, and lakes. Methane may be released to groundwater and streams in areas with high geologic or geothermal activity. This EAGER award will conduct the first study to explore the role of geologic and fossil methane as an alternative carbon source in supporting life in river floodplains. The award will also support research training of students and doctoral scholars, engage fish hatchery managers in citizen science research, and provide knowledge of how river systems function to the public. The underlying assumption for most ecosystems on Earth is that the fixation of modern carbon dioxide drives productivity and biodiversity, with little recognition or study of other potential carbon pathways (e.g., methane) as drivers of productivity and biodiversity. Despite the likely contribution of fossil and geologic methane to freshwater systems and the potential for methane to be transformed ecologically into less harmful forms, the freshwater biotic processes affecting this greenhouse gas source are poorly known. This EAGER award will investigate the role of abiotic, thermogenic, and fossil methanogenic methane subsidies in supporting freshwater floodplain ecosystems by providing a carbon source to the carbon-limited shallow aquifer food web (deep hyporheic zone). The objective of this award is to quantify contributions of carbon from various methane sources to the aquifer food web. Innovative stable isotope methods will be used to assess the carbon sources and trace them through the floodplain foodweb, then develop new approaches for discovering methane source contributions to freshwater ecosystems. This research could potentially shift the current carbon dioxide-based paradigm of driving productivity and biodiversity by demonstrating that shallow aquifer food webs below river floodplains are driven by geologic and fossil methane-derived carbon. Therefore, these floodplain aquifers would be the first to demonstrate a conceptually and ecologically analogous paradigm to oceanic hydrothermal vent ecosystems.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.