Tranter, M., Fountain, A.G., Fritsen, C.H., Lyons, W.B., Priscu, J.C., Statham, P.J. and Welch, K.A.
Extreme hydrochemical conditions in natural microcosms entombed within Antarctic ice
Hydrological Processes, 18, (2), . (doi:10.1002/hyp.5217).
Full text not available from this repository.
Cryoconite holes are near-vertical tubes that form in the surface of glaciers
when solar-heated debris melts into the ice. Those that form in the McMurdo
Dry Valleys of Antarctica are distinctive, in that they have ice lids and are
closed to the atmosphere for periods of years to decades. Photoautotrophs
and heterotrophs grow within this closed environment, perturbing the poorly
buffered water chemistry, yet maintaining the potential for photosynthesis.
Microbial excretion and decomposition of organic matter produces dissolved
organic carbon (DOC): dissolved inorganic carbon ratios of ?1 : 2. Much of
the dissolved nitrogen pool (80–100%) exists as dissolved organic nitrogen
(DON). The DON:DOC ratio is ?1 : 11 (mol/mol), typical of organic particulate
material at the Earth’s surface. The combination of photoautotrophy,
heterotrophy and weak chemical buffering within these microcosms promotes
values of pH, pCO2, O2 saturation and percentage total dissolved nitrogen as
DON that reach 10·99, 10?7·6 atm, 160% and 100% respectively, which are
a unique combination among the surface waters on Earth. These ice-sealed
cryoconite holes could be important analogues of refugia on Snowball Earth
and other icy planets.
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