Cryosphere

Microbes on the edge

Biogeosciences 9, 2431–2442 (2012)

Credit: © STOCKTREK IMAGES/THINKSTOCK

Microbial communities reside on the surface of the ice sheet that covers most of Greenland, but the contribution of these communities to regional biogeochemical cycling is unclear. Measurements of nitrogen chemistry in natural surface holes indicate that microbes at the edge of the ice sheet fix nitrogen — they capture atmospheric nitrogen and convert it into a form that can be readily used by other organisms.

In the summer of 2010, Jon Telling of the University of Bristol and colleagues examined nitrogen dynamics in a series of small holes in the surface of the Greenland ice sheet along a 79-km-long transect, running from the terminus of the Leverett Glacier into the ice sheet interior. They identified acetylene reduction, a measure of nitrogen fixation, in debris-rich ice sampled from the glacier terminus, as well as in sediment and water collected from the edge of the ice sheet. The capacity for nitrogen fixation disappeared, however, around 7.5 km from the ice sheet's edge.

Nitrogen fixation by microbes could provide a source of bioavailable nitrogen to the periphery of the Greenland Ice Sheet, potentially aiding the colonization of ice sheet sediments by other microorganisms and plants.

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Armstrong, A. Microbes on the edge. Nature Geosci 5, 520 (2012). https://doi.org/10.1038/ngeo1544

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