RAPID: Quantifying the response of oxic methane production to biogeochemical changes in aquatic ecosystems: record Sierra Nevada snowmelt as a natural experiment

甲烷是一种令人着迷的气体，可以在电器和火箭中燃烧，但它也是大气中的一种强大的温室气体。广泛的生物和地质过程会产生甲烷，这使得弄清楚甲烷如何在陆地、水、生物和大气之间移动变得具有挑战性。其中一些过程已被人类活动改变，导致大气中甲烷浓度增加，从而导致气候变化。然而，最近的发现使事情变得更加复杂，因为甲烷意外地在湖泊和海洋的表层水中产生。这种现象发生的方式和原因尚不完全清楚，但它可能与水生生态系统的营养和碳供应有关。该研究项目利用加州内华达山脉创纪录的积雪提供的自然实验，解决了营养物质和碳在甲烷生产中的作用。当雪融化并最终进入高海拔淡水湖时，它会带来营养物质和碳。研究人员将确定这些营养物质和碳的流入是否会导致生活在这些湖泊中的微生物产生氧化甲烷。研究人员定期对分布在加利福尼亚州约塞米蒂国家公园高海拔地区的五个湖泊进行采样。这些湖泊的甲烷浓度和产量通常在夏末或初秋达到峰值，据推测，随着积雪和融雪的增加，这些峰值会特别高。研究人员将确定产生甲烷的机制和有机体，以及它们如何受到营养物质和碳的影响，方法是将生物地球化学测量和分子生物学技术结合起来，应用于在湖泊中收集的样本和实验室实验。这项研究将确定(1)氧化甲烷的产生是否受到营养物和碳的影响，(2)哪些过程产生甲烷，以及(3)这些过程如何因营养物和碳通量的自然或人为变化而发生变化。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Methane is a fascinating gas that can be burned in appliances and rockets, yet also acts as a powerful greenhouse gas in the atmosphere. A wide range of biological and geological processes produce methane, making it challenging to figure out how methane moves between land, water, organisms, and the atmosphere. Some of these processes have been altered by human activity, leading to increasing methane concentrations in the atmosphere that contribute to climate change. However, recent discoveries have made things even more complicated by showing that methane is produced unexpectedly in surface waters of lakes and the ocean. How and why this occurs is still not fully understood, but it may be linked to the supply of nutrients and carbon to aquatic ecosystems. This research project addresses the role of nutrients and carbon in methane production by using a natural experiment provided by record snowpack in California’s Sierra Nevada mountains. As snow melts and eventually enters high elevation freshwater lakes, it can bring nutrients and carbon with it. Researchers will determine whether this influx of nutrients and carbon leads to oxic methane production by tiny organisms living in these lakes.The researchers are regularly sampling five lakes spread across the higher elevations of Yosemite National Park in California. These lakes typically show a peak in methane concentrations and production in late summer or early fall, and these peaks are hypothesized to be particularly high following increased snowpack and snow melt. The researchers will determine which mechanisms and organisms produce methane, and how they are affected by nutrients and carbon, through a combination of biogeochemical measurements and techniques from molecular biology applied to samples collected in the lakes and lab-based experiments. The research will determine (1) whether oxic methane production is affected by nutrients and carbon, (2) which processes produce methane, and (3) how processes may change due to natural or human-caused changes in nutrient and carbon fluxes.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.