Collaborative Research: Coupled biological and photochemical degradation of dissolved organic carbon in the Arctic

从陆地流向溪流、河流和湖泊的碳，大约有一半以二氧化碳的形式流失到大气中。陆地上的碳主要通过微生物呼吸和暴露在阳光下转化为二氧化碳。这两个过程都发生在阳光充足的地表水域，但人们对它们如何相互作用产生二氧化碳知之甚少。例如，先前的研究表明，阳光照射可以增加或减少微生物的呼吸。此外，微生物群落的组成如何影响微生物的呼吸作用也鲜为人知。在北极，了解微生物和阳光是如何相互作用的尤为重要，那里融化的永久冻土将把大量的碳从陆地释放到水中。推进我们对这种碳向大气中流失的理解，对于理解全球碳循环至关重要。该项目利用微生物基因组学和碳化学方面的最新进展，提高对北极淡水碳循环的了解。这项研究还将吸引高中教师和学生参与科学发现和应用。PIS还计划通过这个项目为本科生提供研究机会。确定溶解有机碳(DOC)光生物转化为二氧化碳的控制因素，对于了解从北极内陆水域向大气排放二氧化碳的驱动因素至关重要。为了获得这一理解，本项目将通过实验回答三个问题：(Q1)DOC化学如何控制微生物的代谢？这个问题将通过培养微生物群落来回答，这些微生物群落从表层土壤和来自北极两个主要地貌的更深的永久冻土中淋洗出DOC。将通过测量微生物基因丰度和这些基因的表达，以及通过质谱仪确定在培养过程中消耗和产生的DOC的分子公式来确定DOC转化为二氧化碳的微生物途径；(Q2)DOC暴露在阳光下如何改变微生物将DOC转化为二氧化碳的方式？这个问题将通过将淋溶的土壤DOC暴露在阳光下来回答；(Q3)微生物群落的长期适应如何影响DOC转化为二氧化碳的速率？这个问题将通过测量孵化期间的微生物丰度、呼吸作用、产量和群落组成(物种)来回答。对这些过程的详细了解至关重要，因为将永久冻土土壤碳转化为二氧化碳有可能对大气二氧化碳水平和由此产生的环境变化产生积极和加速的反馈。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。

About half of the carbon that moves from land to streams, rivers, and lakes is lost to the atmosphere as carbon dioxide. Carbon from land is converted to CO2 mainly by microbial respiration and exposure to sunlight. Both processes happen in sunlit surface waters, but little is known about how they interact to produce CO2. For instance, previous research has shown that sunlight exposure can either increase or decrease microbial respiration. In addition, there is little known about how composition of microbial communities may influence microbial respiration. Understanding how microbes and sunlight interact is particularly important in the Arctic where thawing permafrost soils will release large amounts of carbon from land to water. Advancing our understanding of loss of this carbon to the atmosphere is critical to understanding the global carbon cycle. This project takes advantage of recent advances in microbial genomics and carbon chemistry to improve understanding of carbon cycling in Arctic freshwaters. This research will also engage high school teachers and students in scientific discovery and application. The PIs also plan to provide undergraduates with research opportunities through this project.Determining the controls on coupled photo-bio conversion of dissolved organic carbon (DOC) to CO2 is essential for understanding the drivers of CO2 fluxes to the atmosphere from inland waters in the Arctic. To gain this understanding, this project will use experiments to answer three questions: (Q1) How is microbial metabolism controlled by DOC chemistry? This question will be answered with incubations of microbial communities with DOC leached from surface soils and deeper permafrost soils from two dominant arctic landscapes. Microbial pathways of DOC conversion to CO2 will be identified by measuring microbial gene abundance and the expression of those genes, and molecular formulas of DOC that are consumed and produced during incubations identified by mass spectrometry; (Q2) How does DOC exposure to sunlight alter how microbes convert DOC to CO2? This question will be answered by exposing leached soil DOC to sunlight; (Q3) How does the longer-term adaptation of microbial communities affect the rate of DOC conversion to CO2? This question will be answered by measuring microbial abundance, respiration, production, and community composition (species) during the incubations. A detailed understanding of these processes is critical because conversion of permafrost soil carbon to CO2 has the potential to create a positive and accelerating feedback to atmospheric CO2 levels and resulting environmental changes.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.