Carbon flow from volcanic CO2 into soil microbial communities of a wetland mofette

Abstract

Effects of extremely high carbon dioxide (CO 2 ) concentrations on soil microbial communities and associated processes are largely unknown. We studied a wetland area affected by spots of subcrustal CO 2 degassing (mofettes) with focus on anaerobic autotrophic methanogenesis and acetogenesis because the pore gas phase was largely hypoxic. Compared with a reference soil, the mofette was more acidic (DpH B0.8), strongly enriched in organic carbon (up to 10 times), and exhibited lower prokaryotic diversity. It was dominated by methanogens and subdivision 1 Acidobacteria, which likely thrived under stable hypoxia and acidic pH. Anoxic incubations revealed enhanced formation of acetate and methane (CH 4 ) from hydrogen (H 2 ) and CO 2 consistent with elevated CH 4 and acetate levels in the mofette soil. 13 CO 2 mofette soil incubations showed high label incorporations with B512 ng 13 C g (dry weight (dw)) soil À 1 d À 1 into the bulk soil and up to 10.7 ng 13 C g (dw) soil À 1 d À 1 into almost all analyzed bacterial lipids. Incorporation of CO 2 -derived carbon into archaeal lipids was much lower and restricted to the first 10 cm of the soil. DNA-SIP analysis revealed that acidophilic methanogens affiliated with Methanoregulaceae and hitherto unknown acetogens appeared to be involved in the chemolithoautotrophic utilization of 13 CO 2 . Subdivision 1 Acidobacteriaceae assimilated 13 CO 2 likely via anaplerotic reactions because Acidobacteriaceae are not known to harbor enzymatic pathways for autotrophic CO 2 assimilation. We conclude that CO 2 -induced geochemical changes promoted anaerobic and acidophilic organisms and altered carbon turnover in affected soils.

Long-term CO2injection and its impact on near-surface soil microbiology

“…Both bacterial and archaeal 16S rDNA gene copy numbers ranged from 10 7 to 10 10 gdw -1 of soil (Figure 3a and 3b) without significant CO 2 -induced differences between CO 2 -exposed and reference samples (ANOVA, P > 0.05; Supplementary Table 6a). Similar results were detected for the CO 2 injection site PISCO 2 as well as for some natural CO 2 vents (Beaubien et al 2008;Frerichs et al 2013;Beulig et al 2015;Fernández-Montiel et al 2015). In contrast, decreasing microbial gene copy numbers by up to two orders of magnitude with increasing CO 2 at natural CO 2 vents were previously detected (Oppermann et al 2010;.…”

“…Similar CH 4 production rates have been detected in previous studies at natural CO 2 vents with values between 0.001 and 0.1 µmol d -1 gdw -1 (Oppermann et al 2010;Beulig et al 2015). However, distinct increasing CH 4 production rates with increasing CO 2 concentration as described at natural sites could not be detected at the ASGARD site.…”

“…Within CO 2 vents, thaumarchaeotal I.1b soil group members were dominating in contrast to the predominant euryarchaeotal Methanomicrobia members at the reference sites (Frerichs et al 2013;Šibanc et al 2014). In contrast to these findings, in another study Beulig et al (2015) detected Nitrososphaerales of the Thaumarchaeota only within the reference samples of the investigated mofette field in the Cheb Basin (Czech Republic). Here, the CO 2 vent samples were dominated by the euryarchaeotal classes Methanosarcinales and Methanomicrobiales (50-90%).…”

“…In addition, analyses of soil samples from the Stavesinci CO 2 vent area (Slovenia) showed increasing numbers of Firmicutes sequences with increasing CO 2 (Šibanc et al 2014). So far, analyses of soil samples from natural CO 2 vents suggest that high CO 2 concentrations might result in increasing numbers of Acidobacteria, Chloroflexi and anaerobic acetogens (Sáenz de Miera et al 2014;Šibanc et al 2014;Beulig et al 2015). However, the microbial interactions and metabolic activity of soil Bacteria under high CO 2 concentrations remains unclear and need further research.…”

Burning coal spoil heaps as a new habitat for the extremophilic red alga Galdieria sulphuraria

“…An area of approximately 100 x 80 m of the Soos Nature Reserve is occupied by mofettes, where gas originates from active magma around 30 kilometres under the earth's surface and bubbles through the mud pools. The recent study of mofettes done by Beulig et al (2015) in the neighbouring area of Soos Nature Reserve showed that they could actually promote the soil colonization by acidophilic microorganisms as mofette soil tends to be more acidic than the adjacent ones. Unfortunately, it is very hard to make any conclusions about the actual colonization of Soos Nature Reserve by G. phlegrea, but strains belonging to CaM Group A could possibly exhibit a higher tolerance and adaptability for travelling longer distances.…”