Dissertation Research: The effects of precipitation change on microbial drivers of salt marsh greenhouse gas emissions

论文研究：降水变化对盐沼温室气体排放微生物驱动因素的影响

• 批准号: 1501721
• 负责人: Robinson Fulweiler
• 金额: $ 2.02万
• 依托单位: Trustees of Boston University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1501721&HistoricalAwards=false
• 关键词: Dissertation; Research; effects; precipitation; change

It is predicted that, in the next several decades, Eastern North America will experience an overall increase in annual precipitation, as well as an increase in the intensity of precipitation events. Rainfall will be concentrated into fewer, larger storms punctuating longer periods of drought. The effects of this intensification may be especially important in ecosystems like salt marshes, that are already under water stress. Salt marshes provide critical ecosystem services including nursery habitat for fish and birds, and nutrient filtration. They also store vast amounts of organic carbon. Changes in precipitation may alter their ecology, and disrupt their nutrient filtration and carbon storage activities, much of which is mediated by salt marsh microorganisms. The objective of this research is to quantify the effects of precipitation intensification on on microbial processes in a New England salt marsh. This doctoral dissertation improvement grant research will also examine mechanisms behind patterns of greenhouse gas (CH4 and N2O) emissions and uptake by salt marsh microbes by studying microbial gene expression patterns in the environment. Precipitation changes, especially the intensification of precipitation events (e.g. longer droughtsand stronger storms) are an important aspect of anthropogenic global climate change. The impact of precipitation intensification may be especially great in ecosystems that are chronically water stressed, either from extremely dry conditions, or from extremely wet conditions that lead to anoxia in the sediment. As tidal wetlands, salt marshes are subject to a variety of stressors including high salinity and anoxia, making them potentially very sensitive to changes in rain and other freshwater inputs. Over the past year an experiment has been performed to test the effects of precipitation change onsalt marsh biogeochemistry. Rainout shelters have been used to intercept incoming rain, and deliver it to one of four precipitation treatments: ambient rainfall, doubled ambient rainfall, prolonged drought, or simulated intense drought with strong storms. Monthly measurements were made of greenhouse gases, the overall productivity and shoot:shoot allocation of marsh grasses, and the cycling of silica and other nutrients through plants, sediment, and porewater. Funding from this award will support the addition of a molecular component. The primary objectives will be to determine 1) whether climate-induced changes in precipitation (prolonged drought, doubled growing season totals, or alteration between the two) will alter salt marsh microbial community structure and species richness, and 2) to what degree changes in the expression of key functional genes by the microbial community can be linked to measured net rates of trace greenhouse gas flux. This research will test two hypotheses: (1) Prolonged drought and doubled precipitation rates will both lead to decreases in microbial species richness, but when drought and increased precipitation are combined this intensified precipitation regime will lead to an increase in microbial species richness, and (2) trace greenhouse gas fluxes (CH4 and N2O) are positively correlated with functional gene transcript copies for production and negatively correlated with those for consumption of each gas. Hypothesis 1 will be tested by determining microbial community composition and species richness with next-generation sequencing of genomic DNA in sediments at an ongoing field experiment. Hypothesis 2 will be tested by pairing high-sensitivity gas flux measurements with quantification of transcript copies of 6 functional genes (mcrA, pmoA, mxaF, nosZ, norB, and norZ) governing microbial production and consumption of CH4 and N2O. The proposed research will be integrated with new outreach activities. A Ph.D. student will work with the BU Upward Bound Math and Science program, which prepares low-income and first generation college bound students for a successful higher education experience. She will lead a one-day workshop with Upward Bound high school students on the importance of salt marshes, and the linkages between microbial communities and greenhouse gases. She will also host a summer Upward Bound high school student intern to work on this project. Second, the Ph.D. student will coordinate in a Citizen Science Outreach Program that leverages the experiment's high-visibility location in a frequently-visited area of a National Park to involve interested parties in the monitoring of the experimental treatments.

据预测，在今后几十年中，北美东部的年降水量将全面增加，降水事件的强度也将增加。降雨将集中在更少，更大的风暴中，打断更长时间的干旱。这种强化的影响可能在已经处于水压力下的盐沼等生态系统中特别重要。 盐沼提供关键的生态系统服务，包括鱼类和鸟类的苗圃栖息地以及营养过滤。它们还储存了大量的有机碳。 降水量的变化可能会改变其生态，破坏其营养过滤和碳储存活动，其中大部分是由盐沼微生物介导的。 本研究的目的是量化降水强化对新英格兰盐沼微生物过程的影响。 这篇博士论文改进补助金研究还将通过研究环境中微生物的基因表达模式，研究温室气体（CH4和N2O）排放模式和盐沼微生物吸收模式背后的机制。降水量的变化，特别是降水事件的加剧（如更长的干旱和更强的风暴）是人为全球气候变化的一个重要方面。在长期缺水的生态系统中，降水加剧的影响可能特别大，无论是极端干旱的条件，还是导致沉积物缺氧的极端潮湿的条件。作为潮汐湿地，盐沼受到各种压力，包括高盐度和缺氧，使它们对降雨和其他淡水输入的变化非常敏感。在过去的一年中，我们进行了一项试验，以测试降水变化对盐沼土壤地球化学的影响。防雨棚被用来拦截雨水，并将其输送到四种降水处理中的一种：环境降雨，加倍的环境降雨，长期干旱或模拟强风暴的强烈干旱。每月测量温室气体，整体生产力和拍摄：拍摄分配沼泽草，二氧化硅和其他营养物质通过植物，沉积物和孔隙水的循环。该奖项的资金将支持添加分子组件。主要目标是确定1）是否气候引起的降水变化（长期干旱，生长季节总数增加一倍，或两者之间的变化）将改变盐沼微生物群落结构和物种丰富度，以及2）微生物群落关键功能基因表达的变化在多大程度上可以与测量的痕量温室气体通量的净速率相关联。本研究将检验两个假设：（1）长期干旱和加倍的降水率都将导致微生物物种丰富度的下降，但当干旱和降水增加相结合时，这种强化的降水制度将导致微生物物种丰富度的增加，痕量温室气体通量（CH4和N2O）与生产的功能基因转录本拷贝呈正相关，与每种气体的消耗量呈负相关。假设1将通过在正在进行的实地实验中对沉积物中的基因组DNA进行下一代测序来确定微生物群落组成和物种丰富度。假设2将通过将高灵敏度气体通量测量与控制微生物产生和消耗CH4和N2O的6个功能基因（mcrA、pmoA、mxaF、nosZ、norB和norZ）的转录本拷贝的定量配对来检验。拟议的研究将与新的外联活动相结合。博士学位学生将与BU向上绑定数学和科学计划，它准备低收入和第一代大学的学生一个成功的高等教育经验。她将领导一个为期一天的研讨会与向上约束高中学生对盐沼的重要性，以及微生物群落和温室气体之间的联系。她还将主持一个夏季向上约束高中学生实习这个项目的工作。第二，博士。学生将在公民科学推广计划中进行协调，该计划利用实验在国家公园经常访问的区域的高可见度位置，让感兴趣的各方参与监测实验治疗。