AUTHOR=Lin Yongxin , Liu Deyan , Yuan Junji , Ye Guiping , Ding Weixin 

TITLE=Methanogenic Community Was Stable in Two Contrasting Freshwater Marshes Exposed to Elevated Atmospheric CO2

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.00932

DOI=10.3389/fmicb.2017.00932

ISSN=1664-302X

ABSTRACT=<p>The effects of elevated atmospheric CO<sub>2</sub> concentration on soil microbial communities have been previously recorded. However, limited information is available regarding the response of methanogenic communities to elevated CO<sub>2</sub> in freshwater marshes. Using high-throughput sequencing and real-time quantitative PCR, we compared the abundance and community structure of methanogens in different compartments (bulk soil, rhizosphere soil, and roots) of <italic>Calamagrostis angustifolia</italic> and <italic>Carex lasiocarpa</italic> growing marshes under ambient (380 ppm) and elevated CO<sub>2</sub> (700 ppm) atmospheres. <italic>C. lasiocarpa</italic> rhizosphere was a hotspot for potential methane production, based on the 10-fold higher abundance of the <italic>mcr</italic>A genes per dry weight. The two marshes and their compartments were occupied by different methanogenic communities. In the <italic>C. lasiocarpa</italic> marsh, archaeal family <italic>Methanobacteriaceae</italic>, Rice Cluster II, and <italic>Methanosaetaceae</italic> co-dominated in the bulk soil, while <italic>Methanobacteriaceae</italic> was the exclusively dominant methanogen in the rhizosphere soil and roots. Families <italic>Methanosarcinaceae</italic> and <italic>Methanocellaceae</italic> dominated in the bulk soil of <italic>C. angustifolia</italic> marsh. Conversely, <italic>Methanosarcinaceae</italic> and <italic>Methanocellaceae</italic> together with <italic>Methanobacteriaceae</italic> dominated in the rhizosphere soil and roots, respectively, in the <italic>C. angustifolia</italic> marsh. Elevated atmospheric CO<sub>2</sub> increased plant photosynthesis and belowground biomass of <italic>C. lasiocarpa</italic> and <italic>C. angustifolia</italic> marshes. However, it did not significantly change the abundance (based on <italic>mcr</italic>A qPCR), diversity, or community structure (based on high-throughput sequencing) of methanogens in any of the compartments, irrespective of plant type. Our findings suggest that the population and species of the dominant methanogens had weak responses to elevated atmospheric CO<sub>2</sub>. However, minor changes in specific methanogenic taxa occurred under elevated atmospheric CO<sub>2</sub>. Despite minor changes, methanogenic communities in different compartments of two contrasting freshwater marshes were rather stable under elevated atmospheric CO<sub>2</sub>.</p>