Abstract
ABSTRACT Microorganisms play a significant role in changing the physical properties of the surface of the Greenland Ice Sheet. Cryoconite holes are a hotspot for this microbial activity, yet little is known about the REDOX conditions that develop within them. In this study, we used oxygen microelectrodes and microoptodes to measure for anoxic conditions at the microscale, for the first time revealing a potential niche for anaerobic microorganisms and anaerobic processes. The development of an anoxic zone 2 mm deep within a 6 mm-thick layer of cryoconite sediment was observed within an hour of disturbance, showing rapid acclimation to changing physical conditions. Long-term (half year) incubations of cryoconite material showed a peak of oxygen production and consumption after forty days and reached a low-activity, steady state by day 116, with a persisting anoxic zone beginning between 2 mm and 4 mm deep. Anaerobic microorganisms, which have received little attention to date, should therefore be considered an important component of the cryoconite ecosystem. We discuss the possible dynamics of oxygen concentrations in the supraglacial system and infer that anoxic zones are an important factor in the development of cryoconite sediment communities.
Highlights
Cryoconite holes are a distinct microbial niche within the polar biome (Anesio and LaybournParry 2012b; Hodson et al 2015b)
The shape and size of cryoconite holes seemed to be constrained by local ice-surface morphology and hydrology, in common with Cook, Edwards, and Hubbard (2015a)
The most abundant types observed on this sector of the Greenland Ice Sheet (GrIS) were very small (
Summary
Cryoconite holes are a distinct microbial niche within the polar biome (Anesio and LaybournParry 2012b; Hodson et al 2015b). They are formed when dark-colored dust particles deposited on ice surfaces melt into the surrounding ice, creating a cylindrical or quasi-cylindrical hole that is filled with water and has a sediment layer at the bottom (Bagshaw et al 2007; Porazinska et al 2004b). Cryoconite material is considered to be one of the potent albedo-reducing factors contributing to the darkening process of a large sector of the Greenland Ice Sheet (GrIS) (Benning et al 2014b; Musilova et al 2015b; Takeuchi, Kohshima, and Seko 2001b; Yallop et al 2012b). The precise contribution of biological effects to total melting requires investigation (Tedesco et al 2015b), but its importance has been recognized (Benning et al 2014b; Stibal, Šabacká, and Žárský 2012b; Tedesco et al 2015b; Uetake et al 2010b; Yallop et al 2012b)
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