13C-Tracking of Methanotrophs in a Pulsing Wetland.

Very few field - based studies have been done on the microbial ecology of the methanotrophs and how they respond to different land management systems. In particular, hydrologic pulsing of wetlands should alter methanotroph communities and their ability to oxidize methane (CH₄)_, but this is entirely uninvestigated. Microbial Phospholipid Fatty Acid (PLFA) profiling provides a culture-independent method to study microbial ecology of methanotrophs. Stable Isotope Probing (SIP) method offers the novel opportunity to track ¹³CH₄ flow through methanotrophs and into secondary microbial feeders and soil organic carbon pools. Our previous study of the rates of Potential methane Oxidation at three distinct landscape positions located at the Olentangy River Wetland Research Park, Columbus, Ohio indicated the highest Potential Methane Oxidation due to the Methanotrophs to occur in the permanently flooded (PF) sites of the constructed wetlands. Combining the PLFA analysis approach with stable isotopic  probing using ¹³C provided a means to connect methane oxidation to specific methanotrophs by exposing the soil samples to ¹³CH₄. The Type II Methanotrophs (PLFAs 18:1w9c, 18:1w7c, 18:1w8c) have a greater abundance at the intermittently flooded (IF) sites than the PF sites. Interestingly, the signature PLFA for the Type II methanotrophs, i.e., 18:1w8c was detected only in the sediment samples from 0-8 cm depth of the PF sites and seems to have a determining role in the significantly higher potential methane oxidation rates at this site. The expected outcome from this study will be useful information towards managing wetlands to optimize methanotrophic activity, and simultaneously enable research on the unexplored role of CH₄ oxidation in sequestering C in soils.