Microbial succession within a pro-glacial zone: The Middle Fork Toklat Glacier, Denali National Park & Preserve, Alaska, USA

The pro-glacial zone of the Middle Fork Toklat Glacier (MTG) in Denali National Park and Preserve in Alaska is a debris covered glacier supraglacial debris covers the glacial terminus for several kilometers. As the glacier retreats, it leaves behind a prominent moraine of heterogeneous rocks and silt. This study constitutes the first ever investigation of microbial succession in this type of ecosystem. Functional biogeochemistry is altered by microorganisms prior to plant colonization. Soil mineral content appears to contribute to trends in microbial biomass and nitrogen-fixation rates. Total nutrients and nitrogen-fixation rates indicate that the MTG pro-glacial zone may be dominated by autotrophic microorganisms early in the chronosequence. In addition, trends in total nutrients and microbial biomass are different in the plant free area nearest the current terminus than in the region of plant colonization. And within the supraglacial debris above the terminus, there is evidence of substantial microbial activity.