Microbial Biogeographic Patterns of Terrestrial Mud Volcanoes across Eurasian Continent

• Main Authors: Li-Ling Chen, 陳俐陵
• Other Authors: 林立虹
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/8jt3r4

碩士 === 國立臺灣大學 === 海洋研究所 === 105 === Terrestrial mud volcanoes represent the surface expression of conduits tapping fluid and gas reservoirs in deep subsurface environments. Whether dispersal of microbial communities could proceed in such habitat depends significantly on the connectivity of the subsurface fluid conduits along long distance. While most terrestrial mud volcanoes are hydrologically isolated from each other and strictly obligatory anaerobes inherited in mud volcanoes would be limited upon the exposure to the atmosphere, microbial dispersal would be restricted. This study hypothesized that the physiochemical factors in mud volcanoes is highly correlated with microbial community structure. With this, we analyzed microbial community structure of terrestrial mud volcanoes using samples collected from Italy, Georgia, China, Myanmar, Iran, and Taiwan. We conducted various analyses to test the validity of distance and physiochemical factors in explaining biogeographic pattern. Our analyses demonstrated that most communities varied significantly between samples or cores (with Bray-Curtis dissimilarity > 0.7). Exceptions (with Bray-Curtis dissimilarity = 0.69) occurred for core pairs from Italy but could be categorized in accordance with their geological backgrounds. Among more than 100,000 OTUs, no cosmopolitan could be found. However, five cosmopolitans belong to Proteobacteria, Bacteroidetes, and Methanosarcina in all cores. The slope parameters of positive abundance-range and distance-decay relationships were generally greater than or comparable with those for marine seafloor sediments, and cold seeps, suggesting the effects of dispersal capability on community diversity. For comparison, the nine physiochemical parameters (including methane, chloride, sulfate, total nitrogen, total sulfur, total inorganic carbon and total organic carbon) only explained 9.9% of community variance, and specific geochemical parameters were correlated with specific taxa. For example, Thiobacillus and sulfate were positivity correlated with a Pearson coefficient of 0.86. Since this genus could oxidize sulfide, thiosulfate or polythionates to produce sulfate for energy acquisition. Their high relatedness suggests a strong control of geochemical context on population distribution. Overall, our results did not support the original hypothesis we proposed. Physiochemical parameters could be correlated to limited taxa possibly due to the lack of understanding of the physiological characteristics for communities. Instead, the neutral theory can better account for the biogeographic pattern in terrestrial mud volcanoes.