EFFECTS OF CO_2 ON DEEP-SEA FLOOR MICROBIAL COMMUNITIES

摘要

It has been widely recognized that a substantial rise CO_2 concentration in the atmosphere causes global climate change. In an effort to reduce the future atmospheric CO_2 increase, some technological mitigation strategies have been proposed. On the basis of detailed investigations to date, it has been recognized that the CO_2 sequestration in the ocean is one of the promising options from the points of view of its capacity, economy and effectiveness. However, to decide the mitigation scenario of CO_2 emission, we have to evaluate not only the technical feasibility of ocean sequestration of CO_2, but also environmental impacts. We conducted benthic chamber experiment to investigate the impact of CO_2 injection on deep-sea microbial ecosystem. In this experiment, the impact of CO_2 and CO_2 -induced pH change on deep-sea floor microbial communities were investigated to determine the ecological effects by CO_2 ocean sequestration. Microbial communities were characterized by using cultivation-independent molecular techniques, PCR-based denaturing gradient gel electrophoresis (DGGE). A shift in community composition caused by CO_2 enrichment was observed in sea-floor surface. In order to determine relationships between the community fingerprints, similarities (Pearson product-moment coefficient) were calculated and UPGMA was used to create a dendrogram describing pattern similarities. The control sea floor surface sample clustered away from the other sample. Bacteria were identified by sequencing of DNA in DGGE bands that were observed commonly and only in control surface. Commonly observed band comprised a member of phylogenetic clusters within the Green non-sulfur bacteria. The ε-Proteobacteria was observed only in control surface.