Biogeochemical evolution of cryoconite holes on Canada Glacier, Taylor Valley, Antarctica

Abstract

[1] The cryoconite holes of the McMurdo Dry Valleys are simple, closed biogeochemical systems involving water, ice, mineral and organic debris, which serve as ecosystems for consortia of microorganisms. This study is the first to document the seasonal and annual chemical evolution of solutes in cryoconite holes. Samples of glacier ice, frozen cryoconite holes and those containing water were collected during the austral summer of [2005][2006]. The isolation age was calculated from the excess Cl À in the holes, and varied from 0 to 5 years (a), consistent with the last hot summer when the cryoconite holes were open to the atmosphere. The holes progressively deepen with isolation age. Variations in DIC, DOC, K + and SO 4 2À suggest that dissolution of primary minerals in the cryoconite debris, cyclical precipitation and dissolution of secondary carbonates, net photosynthesis over summer and net respiration during the autumnal freeze are the principal reactions which perturb the seasonal and annual solute concentrations in the holes. DOC is generated in the holes at a rate of 7.5 mg C cm À2 a À1 , and non-sea-salt K + accumulates in frozen holes at a rate of 0.073 meq cm À2 a À1 . We infer that C cycling is complex even in these otherwise simple systems.

Processes controlling carbon cycling in Antarctic glacier surface ecosystems

“…These results demonstrate that glacier surface ecosystems such as cryolakes and cryoconite holes can exist in a state of net production. Processes of carbon cycling have long been documented in cryoconite holes Bagshaw et al, 2007;Foreman et al, 2007;Stibal and Tranter, 2007), but the extent of the dependence of photosynthetic organisms concentrated at the surface of the sediment layer on heterotrophic processes deeper in the sediment has not been fully discussed in the literature to date. This inter-dependence may also help explain the link between sediment depth and P:R balance previously observed in short term (6-24 hr) cryoconite incubations .…”

Microbial community changes along the Ecology Glacier ablation zone (King George Island, Antarctica)

“…The more diverse bacterial phylogenetic structure from one cryoconite hole to another compared to surface ice and the higher metabolic activity given as a spectrum of assimilated carbon sources implies a rapid development of a more complex trophic food web and a more diverse nutrient resource since the melthole formation. An evolution on a chemical level throughout the summer season in cryoconite holes was observed by Bagshaw et al (2007) on McMurdo Dry Valley Glaciers.…”

The spatial structure of Antarctic biodiversity

“…These represent a different endpoint of the nutrient gradient (Table 3). Their microbe-dominated communities exert a major influence on biogeochemical cycling of nutrients on glaciers (Bagshaw et al 2007, Hodson et al 2008. In regions where surface snow melts in summer, snow algae communities can also develop .…”

“…The ice of Antarctica is also not devoid of life. Considerable biomass is associated with snow and ice algal communities that develop in summer, especially in coastal regions, although these have received relatively little research attention (Bagshaw et al 2007, Stibal et al 2012see Hodson et al 2008 for discussion of Arctic parallels). The existence of subglacial microbial communities, increasingly recognized in alpine regions, is now being examined in Antarctica (Tranter et al 2005, Lanoil et al 2009), while much attention is focused on the potentially exceptional biota to be found in the many lakes now known to lie beneath the continent's ice sheets or in its permafrost (Skidmore 2011).…”