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

大约一半的碳从陆地转移到溪流、河流和湖泊中，以二氧化碳的形式进入大气。来自陆地的碳主要通过微生物呼吸和阳光照射转化为CO2。这两个过程都发生在阳光照射的表面沃茨，但人们对它们如何相互作用产生二氧化碳知之甚少。 例如，以前的研究表明，阳光照射可以增加或减少微生物呼吸。此外，关于微生物群落的组成如何影响微生物呼吸作用，人们知之甚少。 了解微生物和阳光如何相互作用在北极地区尤为重要，因为融化的永久冻土将从陆地向水中释放大量的碳。推进我们对这种碳损失到大气中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的最新进展，以提高对北极淡水碳循环的理解。这项研究也将使高中教师和学生参与科学发现和应用。PI还计划通过该项目为本科生提供研究机会。确定溶解有机碳（DOC）到CO2的耦合光生物转化的控制对于了解北极内陆沃茨CO2通量到大气的驱动因素至关重要。为了获得这种理解，本项目将通过实验来回答三个问题：（Q1）微生物代谢如何受DOC化学控制？ 这个问题将回答孵化的微生物群落与DOC从表层土壤和深层永冻土从两个主要的北极景观沥滤。 DOC转化为CO2的微生物途径将通过测量微生物基因丰度和这些基因的表达，以及通过质谱鉴定的培养期间消耗和产生的DOC分子式来鉴定;（Q2）DOC暴露于阳光如何改变微生物将DOC转化为CO2的方式？ 这个问题将通过将沥滤的土壤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CO2的速率？ 这个问题将通过测量培养过程中的微生物丰度、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是至关重要的，因为永久冻土土壤碳转化为CO2有可能对大气CO2水平产生积极和加速的反馈，并导致环境变化。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。

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.