Carbon Sources to Microbes and Cryoconite on Alaskan Alpine Glacier Surfaces

• Main Author: McCrimmon, Drake
• Format: Text
• Language: English
• Published: Scholar Commons 2017
• Subjects: Cryoconite; Alaskan Alpine; Physical Sciences and Mathematics; Earth Sciences; Geology; glacier; glaciers; Alaska
• Online Access: https://scholarcommons.sc.edu/etd/4276; https://scholarcommons.sc.edu/context/etd/article/5283/viewcontent/McCrimmon_sc_0202M_15156.pdf

Cryoconite are depressions in the ice surface filled with diverse microorganisms and dark debris, which are reducing albedo and increasing glacier melt. In order to understand cryoconite carbon composition and carbon sources to microorganisms living on glacier surfaces, bulk organic carbon and microbial lipids from supraglacial cryoconite sediment within the ablation zones of Spencer, Matanuska, and Mendenhall glaciers in southern Alaska have been coupled with radiocarbon (14C) analyses. The microbial lipids analyzed in these studies, phospholipid fatty acids (PLFA), are components of microbial membranes, quickly degrade after cell death, and give a snapshot of the viable microbial community. PLFA structure distributions indicated autotrophic and heterotrophic microorganisms in the supraglacial environment, in an abundance similar to surrounding Alaskan soils. The 14C content of PLFA indicated that microbes were incorporating carbon that was recently in equilibrium with the atmosphere, which suggests autotrophic predominance or the use of modern carbon by heterotrophs. The 14C content of bulk cryoconite organic carbon on Matanuska and Spencer glaciers was depleted relative to the modern atmosphere, where it was modern and in some cases enriched on Mendenhall glacier. This difference was hypothesized to originate from surrounding geology. These results reveal two distinct carbon pools: a highly abundant microbial community, which uses young carbon as a carbon source, living within and minimally interacting with a larger, sometimes old carbon pool. Ultimately, this study highlights the carbon isotopic heterogeneity of cryoconite material.