DETERMINING MICROBIAL COMMUNITY SHIFTS WITH ALTITUDE FROM THE ACTIVE LAYER OF PERMAFROST REGIONS IN ALASKA

Permafrost regions play a major role in the carbon cycling process on the Earth, since there are large stores of carbon in those areas. As such, permafrost soils are becoming increasingly important to study as the region is exposed to increasing temperatures. However, there is a lack of understanding of how permafrost and the microbial communities that dominate these soils will be affected by future climate change. In this study, our objective was to determine different driving factors in the microbial community of the seasonally-thawed active layer in the Alaskan tundra. The goal of this project is to determine differences in bacteria and fungi communities with depth and location to establish a baseline for how these communities might change with increasing permafrost melting. Soil cores selected for this study were collected in July 2016 and come from Upper Sagwon (N69º25.454', W148º41.653') and Lower Sagwon (N69º28.757', W148º33.58') Alaska. The Upper Sagwon core was sub-sectioned into 6 samples, 29 cm deep, and the Lower Sagwon core was sub-sectioned into 7 samples, 32 cm deep.

To analyze the microbial composition of the soils, phospholipid fatty acids (PLFA) were extracted. PLFAs were chosen because of the uniqueness of these biomarkers to bacteria and fungi. PLFAs degrade rapidly, allowing a view of the communities in the soils at the time of collection. The relationships between PLFA concentration with depth, elevation, and soil characteristics were analyzed. Our data showed that at the Lower Sagwon site PLFA concentration decreased with depth, however, at the Upper Sagwon site, PLFA concentration remained relatively stable with depth. Our results also suggest that in permafrost regions, as total organic carbon (TOC) and total organic nitrogen (TON) decreases, the fungi:bacteria ratio increases, suggesting that the fungi:bacteria ratio dominate the TOC and TON of these soils.