The role of littoral zones as source of methane in lakes: Dynamics, distribution patterns, and emissions

沿岸带作为湖泊甲烷来源的作用：动态、分布模式和排放

• 批准号: 184075001
• 负责人: Dr. Hilmar Hofmann
• 金额: --
• 依托单位: Alfred-Wegener-Institut (AWI) Helmholtz-Zentrum für Polar- und Meeresforschung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2014-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/184075001?language=en
• 关键词: role; littoral; zones; source; methane

Small lakes (<1 km2) have been identified as a significant source of methane in the global methane budget. These lakes dominate in area the global extent of natural, inland water bodies and have higher methane fluxes per unit area than large lakes. However, the estimation of lake-wide methane emissions underlies large uncertainties, because measurements that account for the temporal and spatial variability of methane in and between lakes are rare. The aim of the project is to investigate methane dynamics and distribution patterns in and methane emissions from small lakes on a regional and inter-regional scale. Thereby, the focus will be on the identification of systematic patterns and proxies for the dissolved methane concentration and methane emissions that allow the generalization and spatial up-scaling of the results obtained from a selected number of lakes. The main hypothesis are that (1) the dissolved methane concentration and methane emissions differ substantially between lakes due to their different lake properties; (2) lake and catchment properties as well as abiotic parameters may serve as proxies for the dissolved methane concentration and methane emissions on a regional or even larger spatial scale; (3) the formation and extent of an anoxic hypolimnion in combination with mixing dynamics during overturn periods (i.e., in autumn and after ice break-up) determine the annual, diffusive methane emissions from small lakes; (4) apart from lake characteristics and abiotic conditions, differences in the composition of the microbial community (methane producing and oxidizing bacteria) between lakes may explain differences in the lake-wide methane emissions from lakes. These hypotheses will be tested by intensive field experiments measuring the internal dynamics, spatial heterogeneity, lake-wide distribution, and seasonal variability of dissolved methane and methane emissions together with abiotic conditions in and between small Swabian and Bavarian lakes. State of the art in-situ measuring techniques (e.g., an eddy-covariance system, single- and multi-beam echosounders, methane probes, automated diffusive flux chambers and funnels, oxygen- and carbon dioxide-optodes, CTD, and thermistors), will be combined with intensive water sampling and water sample analysis (dissolved methane, methane isotopic composition, composition of the microbial community, and other water constituents) to meet the requirements of sufficient temporal resolution and reliable absolute data on all abiotic parameters and in specific on the dissolved methane concentration.

小型湖泊(1平方公里)已被确定为全球甲烷收支中的一个重要甲烷来源。这些湖泊在全球范围内的天然内陆水体中占据主导地位，单位面积上的甲烷通量高于大型湖泊。然而，对整个湖泊甲烷排放量的估计存在很大的不确定性，因为考虑到湖泊内和湖泊之间甲烷的时间和空间变异性的测量很少。该项目的目的是在区域和区域间尺度上调查甲烷在小湖泊中的动态和分布模式以及小湖泊的甲烷排放情况。因此，重点将放在确定溶解甲烷浓度和甲烷排放量的系统模式和替代指标，以便推广从选定的若干湖泊获得的结果并在空间上扩大规模。主要假设是：(1)由于湖泊性质的不同，不同湖泊的溶解甲烷浓度和甲烷排放量有很大差异；(2)湖泊和集水区的性质以及非生物参数可以作为区域甚至更大空间尺度上溶解甲烷浓度和甲烷排放的替代指标；(3)低氧低离子的形成和程度与倾覆期(即秋季和解冰后)的混合动力学相结合，决定了小湖泊每年的扩散甲烷排放；(4)除湖泊特征和非生物条件外，湖泊间微生物群落(产甲烷细菌和氧化细菌)组成的差异可能是湖泊甲烷排放差异的原因。这些假设将通过密集的现场实验得到验证，这些实验测量了溶解甲烷和甲烷排放的内部动力学、空间异质性、全湖分布和季节变化，以及小斯瓦边和巴伐利亚湖泊及其之间的非生物条件。最先进的现场测量技术(例如涡流协方差系统、单波束和多波束探测仪、甲烷探头、自动扩散通量室和漏斗、氧和二氧化碳光电二极管、CTD和热敏电阻)将与密集的水样和水样分析(溶解甲烷、甲烷同位素组成、微生物群落组成和其他水成分)相结合，以满足关于所有非生物参数，特别是溶解甲烷浓度的足够的时间分辨率和可靠的绝对数据的要求。