2017 ESA Annual Meeting (August 6 -- 11)

OOS 24-5 - Soil redox conditions are a strong determinant of microbial community composition and the fate of carbon following permafrost thaw

Wednesday, August 9, 2017: 9:20 AM
Portland Blrm 258, Oregon Convention Center
James C. Stegen1, Eric Bottos2, Janet K. Jansson3, Lisa M Bramer4, Young-Mo Kim2, Sarah Fansler4, Carrie D Nicora4, Erika M. Zink5, Rosalie Chu6, Malak M. Tfaily7 and Tom Metz2, (1)Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA, (2)Pacific Northwest National Laboratory, (3)Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA, (4)Pacific Northwest National Laboratory, Richland, WA, (5)Biological Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, (6)Environmental Molecular Sciences Laboratory, Richland, WA, (7)Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA
Background/Question/Methods

Permafrost-affected soils contain enormous stocks of carbon, which are becoming increasingly available to microbial transformation as permafrost regions warm; however, how this warming will influence the permafrost microbiome and the transformation of soil carbon remains unclear. We hypothesize that the redox conditions that arise following permafrost thaw will dictate the structure and function of the microbial community, and strongly influence the nature of carbon transformations. To examine this, permafrost-affected soils from Caribou Poker Creek Research Watershed, Alaska were incubated at 4 °C under aerobic and anaerobic conditions for periods of 9 and 94 days. Over the incubation period, rates of CO2 and CH4 production were measured by gas chromatography, shifts in microbial community structure were characterized by 16S rRNA gene sequencing, and changes in metabolite and organic matter composition were analyzed by GC-MS and ESI-FTICR MS, respectively.

Results/Conclusions

CO2 production rates were significantly higher in aerobic treatments in 9-day and 94-day incubations, by 3-times and 12-times, respectively. Rates of CH4 production were not significantly different between treatments in 9-day incubations, but were 1.6-times higher in anaerobic treatments in 94-day incubations. The community composition remained largely unchanged in the incubated samples, with the exception of the 94-day aerobic incubations, which shifted strongly to become dominated by a single OTU, Rhodoferax ferrireducens. Metabolite profiles also shifted most strongly in the 94-day aerobic incubations, with the abundance of phosphorylated carbon compounds overrepresented in these samples. This work suggests that the redox conditions that arise following permafrost thaw will be a strong determinant of community composition and will govern the ultimate fate of carbon stocks in permafrost-affected soils. Our results are currently being integrated with numerical models aimed at predicting the coupled microbiome-ecosystem response to thaw.