In the current study, cryoconite samples were collected from six glaciers on the Tibetan Plateau to analyze n-alkanes and n-alkenes. The findings revealed that the concentrations of n-alkanes and n-alkenes varied from 40.1 to 496.1 μg g−1 and from 4.6 to 13.8 μg g−1, respectively. The carbon preference index of the long-chain n-alkanes ranged from 3.3 to 8.4, and the average chain length ranged from 28.7 to 29.3. Moreover, the δ13C of the n-alkanes in cryoconites were within the range of C3 plants, demonstrating that the n-alkanes in cryoconites were only derived from vascular plants. However, the δDmean were more negative than that of C3 plants, which could be caused by dry and humid conditions of glaciers. Unlike n-alkanes, n-alkenes ranged from C17:1 to C30:1 and showed a weak even-over-odd carbon number preference in the Dongkemadi, Yuzhufeng, Laohugou and Tianshan glacier, but a weak odd carbon preference in the Qiyi glacier. The n-alkenes in the YL Snow Mountains showed an obvious odd-over-even carbon number predominance from C17:1 to C22:1 with Cmax at C19:1, and the even-over-odd carbon number preference from C23:1 to C30:1 with Cmax at C28:1. This demonstrated that the n-alkenes of cryoconites may be mainly derived from in situ production in glaciers.

Glacier phototroph blooms on the surfaces of ice sheets and glaciers cause albedo reduction, leading to increased melting rates. We observed seasonal changes in the abundance of phototrophs on the Qaanaaq Ice Cap in northwestern Greenland from June to August 2014, and reproduced these changes using numerical and empirical models. The phototroph community on the ice surface mainly consisted of the glacier alga Ancylonema nordenskioldii and the cyanobacterium Phormidesmis priestleyi. The glacier alga appeared on the ice surface in late June, after which its abundance increased exponentially throughout the melting period. A logistic growth model designed for snow algal growth reproduced the measured exponential increases, suggesting that growth could be explained using the model as a function of the ice melting duration. Cyanobacteria appeared and their abundance increased in late July but did not change exponentially thereafter. The abundance of cyanobacteria was explained with an empirical model expressed as a function of the amount of mineral dust on the bare ice surface. Our numerical and empirical models for reproducing glacier algae and cyanobacteria could be useful for quantifying the albedo reduction caused by their growth and the melt rates of the Greenland ice sheet and glaciers in the future.

Cryoconite is a dark-coloured granular sediment that contains biological and mineralogical components, and it plays a pivotal role in geochemistry, carbon cycling and glacier mass balance. In this work, we collected cryoconite samples from Laohugou Glacier No. 12 (LHG) on the north-eastern Tibetan Plateau during the summer of 2015 and measured the spectral albedo. To explore the impacts of this sediment on surface ablation, the ice melting differences between the cryoconite-free (removed) ice and the intact layers were compared. The results showed that the mean concentrations of black carbon (BC), organic carbon (OC) and total iron (Fe) in the LHG cryoconite were 1.28, 11.18 and 39.94 mg g−1, respectively. BC was found to play a stronger role in solar light adsorption than OC and free Fe. In addition, ice covered by cryoconite exhibited the lowest mean reflectance (i.e., <0.1). Compared with the cryoconite-free ice surface, cryoconite effectively absorbed solar energy and enhanced glacial melting at a rate of 2.27–3.28 cm d−1, and free Fe, BC and OC were estimated to contribute 1.01, 0.99 and 0.76 cm d−1, respectively. This study provides important insights for understanding the role of cryoconite in the glacier mass balance of the northern Tibetan Plateau.

A fem, Elaphoglossum hybridum (Bory) Brack., has been cultured from mineral sediment in cryoconite holes in the ice cap of Signy Island, South Orkney Islands. Its provenance, mode of transport to its Maritime Antarctic destination and the significance of viable exotic propagules as potential colonists are discussed.

Meltwater habitats in the Darwin Glacier region, Victoria Land (80°S), were sampled in December 2007 and January 2009 to characterize their microbial and metazoan ecology, nutrient status and geochemistry. Targeted areas included terrestrial ponds of the Grant Valley, Lake Wellman, Tentacle Ridge and Diamond Hill, and supraglacial ponds and cryoconite holes of the lower Darwin Glacier. Geochemistry ranged from Na-Cl dominated terrestrial ponds to Na-HCO3 dominated, dilute supraglacial ponds and cryoconites. All showed the nitrate enrichment typical of inland ponds of Victoria Land (up to 13 g.l-1 NO3-N), with some precipitating nitratine (NaNO3) salt. Elevated pH indicated ongoing photosynthetic processes. Benthic microbial mats were thin and poorly developed, dominated by oscillatoriacean cyanobacteria. Nitrogen-fixing genera were generally absent and diatoms were rare. A large (20 μm long) Cyanothece species was the most abundant cyanobacterium in the water and in sediments of the cryoconites. DNA finger-printing identified distinct differences in cyanobacterial and bacterial community structure between the cryoconites, terrestrial ponds and ponds on glacial margins. Eleven metazoan species were identified, with rotifers being the most abundant. Pond substrate (terrestrial rock, ice-cored moraine or supraglacial ice) proved to be a more significant influence on biogeochemistry than other aspects of geography or climatic conditions.