INVESTIGATING THE LINKAGE BETWEEN METHANOGENESIS AND NITROGEN FIXATION IN FRESHWATER TEMPERATE WETLANDS

Freshwater wetlands play an influential role in the carbon cycle by sequestering and storing carbon, while also being the largest source of natural methane. The carbon cycle can be linked to the nitrogen cycle as some methanogens harbor nifH, a key gene for nitrogen fixation. Limited research, however, has examined the performance of nitrogen fixation by methanogens. This study aims to investigate the linkage between methanogenesis and nitrogen fixation activities by correlation analysis and nifH amplicon sequencing in different geochemical conditions. Sediments were collected from four wetlands with varying characteristics of high iron, sulfate, organic carbon, and low phosphorus levels. Microcosm experiments were conducted to evaluate methane production and nitrogen activities with wetland sediments as a function of different substrates: a mixture of hydrogen and carbon dioxide (4:1), acetate, trimethylamine, or cellulose at 25℃. Wetland sediments supplemented with trimethylamine showed greater nitrogen activities. For the organic-rich carbon sediment supplemented with cellulose, a significant correlation (correlation coefficient = 0.99; p-value < 0.05) between methane production and nitrogen fixation was observed. Currently, we are characterizing nif-harboring microbial communities to identify nitrogen-fixing methanogens enriched during the incubation. Ultimately, this study will improve our understanding of how methanogens may be interconnected with the nitrogen cycle through nitrogen fixation, and how this process may be linked to methane flux in freshwater wetlands. 

Primary Presenter: Lien Tran, Natural Resources Research Institute (Tran1390@d.umn.edu)

Authors:

Lien Tran, University of Minnesota Duluth - Natural Resources Research Institute  (tran1390@d.umn.edu)

Satoshi Ishii, University of Minnesota Department of Soil, Water, and Climate, and University of Minnesota BioTechnology Institute  (ishi0040@umn.edu)

Chan Lan Chun, University of Minnesota Duluth - Natural Resources Research Institute and University of Minnesota Duluth Civil Engineering Department  (chun0157@d.umn.edu)