High microbial activity on glaciers: importance to the global carbon cycle

Abstract

Cryoconite holes, which can cover 0.1-10% of the surface area of glaciers, are small, water-filled depressions (typically o1 m in diameter and usually o0.5 m deep) that form on the surface of glaciers when solar-heated inorganic and organic debris melts into the ice. Recent studies show that cryoconites are colonized by a diverse range of microorganisms, including viruses, bacteria and algae. Whether microbial communities on the surface of glaciers are actively influencing biogeochemical cycles or are just present in a dormant state has been a matter of debate for long time. Here, we report primary production and community respiration of cryoconite holes upon glaciers in Svalbard, Greenland and the European Alps. Microbial activity in cryoconite holes is high despite maximum temperatures seldom exceeding 0.1 1C. In situ primary production and respiration in cryoconites during the summer is often comparable with that found in soils in warmer and nutrient richer regions. Considering only glacier areas outside Antarctica and a conservative average cryoconite distribution on glacial surfaces, we found that on a global basis cryoconite holes have the potential to fix as much as 64 Gg of carbon per year (i.e. 98 Gg of photosynthesis minus 34 Gg of community respiration). Most lakes and rivers are generally considered as heterotrophic systems, but our results suggest that glaciers, which contain 75% of the freshwater of the planet, are largely autotrophic systems.

Possible interactions between bacterial diversity, microbial activity and supraglacial hydrology of cryoconite holes in Svalbard

“…Thus, cryoconite holes on different glaciers also show significant differences in their biogeochemical and metabolic activity, with AB differing from both ML and VB in a manner similar to the variation observed in T-RFLP profiles, and consistent with the findings of Anesio et al (2009) regarding primary production and respiration.…”

“…On the basis of measurement of photosynthesis and respiration rates of cryoconite holes on glaciers in Svalbard, Greenland and the Alps, Anesio et al (2009) have estimated that the net primary production of cryoconite habitats may be as much as 64 000 Tyr À1 of carbon, challenging previous assumptions that glacial ecosystems are heterotrophic and dependent on an Aeolian flux of allochthonous organic matter (Stibal et al, 2008).…”

“…The impact of pCO 2 can be interpreted in the context of the highly autotrophic nature of cryoconite communities (Anesio et al, 2009). Thus, low pCO 2 would correlate with active cryoconite phototrophs, and, as observed, high primary production.…”

Biocryomorphology: Integrating Microbial Processes with Ice Surface Hydrology, Topography, and Roughness

“…The contribution of these microbes to supraglacial carbon fluxes has been estimated over various spatial scales (Hodson et al, 2007;Cook et al, 2012;Chandler et al, 2015). To date, spatial variability in the relative abundances of the various cryoconite microbes (Stibal et al, 2012b(Stibal et al, , 2015Vonnahme et al, 2015) and their carbon cycling potential (Anesio et al, 2009) have only been examined at macroscales. Moreover, cryoconite hole studies have almost exclusively been based on assumptions of steadystate equilibrium-independent of time-focussed on cylindrical holes and thereby decouple cryoconite ecology from changes in cryoconite hole shape and size.…”

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

“…However, Kohshima (1984) identified a simple glacier-associated food web. Hodson et al (2008) and Anesio et al (2009) then radically changed old beliefs by focusing on the importance of high microbial activity on glaciers in the global carbon cycle. Microbes, which have adapted to living under very low temperatures, dominate such cryosphere environments, and may comprise 4 9 10 25 to 7 9 10 29 cells in glacial ice globally, and up to 1 9 10 26 bacterial cells in the uppermost 1-2 m of ablating glacier ice areas (Irvine-Fynn and Edwards 2012).…”