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 mu g g(-1) and from 4.6 to 13.8 mu g 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 delta C-13 of the n-alkanes in cryoconites were within the range of C-3 plants, demonstrating that the n-alkanes in cryoconites were only derived from vascular plants. However, the delta D-mean were more negative than that of C-3 plants, which could be caused by dry and humid conditions of glaciers. Unlike n-alkanes, n-alkenes ranged from C-17:1 to C-30:1 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 C-17:1 to C-22:1 with C-max at C-19:1, and the even-over-odd carbon number preference from C-23:1 to C-30:1 with C-max at C-28:1. This demonstrated that the n-alkenes of cryoconites may be mainly derived from in situ production in glaciers.

The global cryosphere, Earth's frozen water, is in precipitous decline. The ongoing and predicted impacts of cryosphere loss are diverse, ranging from disappearance of entire biomes to crises of water availability. Covering approximately one-fifth of the planet, mass loss from the terrestrial cryosphere is driven primarily by a warming atmosphere but reductions in albedo (the proportion of reflected light) also contribute by increasing absorption of solar radiation. In addition to dust and other abiotic impurities, biological communities substantially reduce albedo worldwide. In this review, we provide a global synthesis of biological albedo reduction (BAR) in terrestrial snow and ice ecosystems. We first focus on known drivers-algal blooms and cryoconite (granular sediment on the ice that includes both mineral and biological material)-as they account for much of the biological albedo variability in snow and ice habitats. We then consider an array of potential drivers of BAR whose impacts may be overlooked, such as arthropod deposition, resident organisms (e.g., dark-bodied glacier ice worms), and larger vertebrates, including humans, that transiently visit the cryosphere. We consider both primary (e.g., BAR due to the presence of pigmented algal cells) and indirect (e.g., nutrient addition from arthropod deposition) effects, as well as interactions among biological groups (e.g., birds feeding on ice worms). Collectively, we highlight that in many cases, overlooked drivers and interactions among factors have considerable potential to alter BAR, perhaps rivaling the direct effects of algal blooms and cryoconite. We conclude by highlighting knowledge gaps for the field with an emphasis on the underrepresentation of genomic tools, understudied areas (particularly high-elevation glaciers at tropical latitudes), and a dearth of temporal sampling in current efforts. We detail a global framework for long-term BAR monitoring that, if implemented, would yield a tremendous amount of insight for BAR and would be particularly valuable in light of the rapid ecological and physical changes occurring in the contemporary cryosphere.

Cryoconite granules are dark-colored spherical aggregates and an important sink for organic matter accumulated in supraglacial environments. However, the variations in dissolved organic matter (DOM) concurrent with the leaching process during cryoconite evolution are poorly understood. This study characterized the evolution of DOM from cryoconite leaching throughout a 30 day in situ experiment in the dark on a mountain glacier of the Tibetan Plateau. The results show that the concentration of dissolved organic carbon (DOC) leached from cryoconite decreased initially from 13.41 +/- 2.71 to 7.10 +/- 2.86 mg C L-1 from day 0 to day 3 but then gradually increased to 53.96 +/- 4.31 mg C L-1 by day 30 with an average DOC leaching rate of 20.32 +/- 0.27% in one ablation season. The DOM absorbance (a(254) and a(365)) at each time point (not including day 0) was highly correlated with the DOC concentration (n = 4, r = 0.98), suggesting an enrichment of chromophoric DOM during the leaching process. The molecular composition of DOM analyzed through Fourier transform ion cyclotron resonance mass spectrometry determined that the initial cryoconite DOM from day 0 was enriched in aliphatic (26%) and peptide-like compounds (20%), suggesting high biolability. Between days 0 and 3, extensive loss of peptide-like and aliphatic compounds was exhibited. Then, from day 3 to 30, 43% of leachate DOM was primarily composed of unique unsaturated, polyphenolic, and condensed aromatic compounds, which were newly produced or leached from cryoconite. Finally, the leaching flux of DOC from cryoconite on the Tibetan Plateau in one ablation season and its potential radiative forcing are evaluated.

Cryoconite granules are dark-colored spherical aggregates and an important sink for organic matter accumulated in supraglacial environments. However, the variations in dissolved organic matter (DOM) concurrent with the leaching process during cryoconite evolution are poorly understood. This study characterized the evolution of DOM from cryoconite leaching throughout a 30 day in situ experiment in the dark on a mountain glacier of the Tibetan Plateau. The results show that the concentration of dissolved organic carbon (DOC) leached from cryoconite decreased initially from 13.41 +/- 2.71 to 7.10 +/- 2.86 mg C L-1 from day 0 to day 3 but then gradually increased to 53.96 +/- 4.31 mg C L-1 by day 30 with an average DOC leaching rate of 20.32 +/- 0.27% in one ablation season. The DOM absorbance (a(254) and a(365)) at each time point (not including day 0) was highly correlated with the DOC concentration (n = 4, r = 0.98), suggesting an enrichment of chromophoric DOM during the leaching process. The molecular composition of DOM analyzed through Fourier transform ion cyclotron resonance mass spectrometry determined that the initial cryoconite DOM from day 0 was enriched in aliphatic (26%) and peptide-like compounds (20%), suggesting high biolability. Between days 0 and 3, extensive loss of peptide-like and aliphatic compounds was exhibited. Then, from day 3 to 30, 43% of leachate DOM was primarily composed of unique unsaturated, polyphenolic, and condensed aromatic compounds, which were newly produced or leached from cryoconite. Finally, the leaching flux of DOC from cryoconite on the Tibetan Plateau in one ablation season and its potential radiative forcing are evaluated.

Microorganisms in cold ecosystems play a key ecological role in their natural habitats. Since these ecosystems are especially sensitive to climate changes, as indicated by the worldwide retreat of glaciers and ice sheets as well as permafrost thawing, an understanding of the role and potential of microbial life in these habitats has become crucial. Emerging technologies have added significantly to our knowledge of abundance, functional activity, and lifestyles of microbial communities in cold environments. The current knowledge of microbial ecology in glacial habitats and permafrost, the most studied habitats of the cryosphere, is reported in this review.