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

甲烷是一种迷人的气体，可以在电器和火箭中燃烧，但也是大气中强大的温室气体。一系列生物和地质过程产生甲烷，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非常具有挑战性。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，导致气候变化。然而，最近的发现使事情变得更加复杂，因为它表明甲烷是在湖泊和海洋的表面沃茨中意外产生的。这种情况是如何发生的，为什么会发生，目前还不完全清楚，但它可能与水生生态系统的营养物质和碳供应有关。该研究项目通过使用加州的Sierra内华达州山脉创纪录的积雪提供的自然实验来解决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的淡水湖泊时，它会带来营养物质和碳。研究人员将确定这种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。这些湖泊通常在夏末或初秋显示出甲烷浓度和产量的峰值，并且这些峰值被假设为在积雪和积雪融化增加后特别高。研究人员将确定哪些机制和生物产生甲烷，以及它们如何受到营养物质和碳的影响，通过将生物地球化学测量和分子生物学技术应用于湖泊和实验室实验中收集的样本。该研究将确定（1）好氧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）由于自然或人为引起的营养物和碳通量的变化，过程可能如何变化。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.