Microbial growth under humic-free conditions in a supraglacial stream system on the Cotton Glacier, Antarctica

• Published in: Environmental Research Letters
• Main Authors: Christine M Foreman, Rose M Cory, Cindy E Morris, Michael D SanClements, Heidi J Smith, John T Lisle, Penney L Miller, Yu-Ping Chin, Diane M McKnight
• Format: Article in Journal/Newspaper
• Language: English
• Published: IOP Publishing 2013
• Subjects: dissolved organic matter (DOM); extracellular emission matrices (EEMs); ice nucleation activity; fluorescence; Environmental technology. Sanitary engineering; TD1-1066; Environmental sciences; GE1-350; Science; Q; Physics; QC1-999; Austral; Cotton Glacier; Antarc*; Antarctica
• Online Access: https://doi.org/10.1088/1748-9326/8/3/035022; https://doaj.org/article/29340164ef524f8f85ff6f7fcd705e8b

During the austral summers of 2004 and 2009, we sampled a supraglacial stream on the Cotton Glacier, Antarctica. The stream dissolved organic matter (DOM) was low (44–48 μM C) and lacked detectable humic fluorescence signatures. Analysis of the excitation emissions matrices (EEMs) indicated that amino-acid fluorophores dominated, consistent with DOM of microbial origin, with little humic-like fluorescence. In most aquatic ecosystems, humic DOM attenuates harmful UV radiation and its absence may represent an additional stressor influencing the microbial community. Nonetheless, the stream contained an active microbial assemblage with bacterial cell abundances from 2.94 × 10 ^4 to 4.97 × 10 ^5 cells ml ^−1 , and bacterial production ranging from 58.8 to 293.2 ng C l ^−1 d ^−1 . Chlorophyll- a concentrations ranged from 0.3 to 0.53 μg l ^−1 indicating that algal phototrophs were the probable source of the DOM. Microbial isolates produced a rainbow of pigment colors, suggesting adaptation to stress, and were similar to those from other cryogenic systems ( Proteobacteria and Bacteroidetes lineages). Supraglacial streams provide an example of contemporary microbial processes on the glacier surface and a natural laboratory for studying microbial adaptation to the absence of humics.