In this study, six bacterial community structures were analyzed from the Dunde ice core (9.5-m-long) using 16S rRNA gene cloning library technology. Compared to the Muztagata mountain ice core (37-m-long), the Dunde ice core has different dominant community structures, with five genus-related groups Blastococcus sp./Propionibacterium, Cryobacterium-related., Flavobacterium sp., Pedobacter sp., and Polaromas sp. that are frequently found in the six tested ice layers from 1990 to 2000. Live and total microbial density patterns were examined and related to the dynamics of physical-chemical parameters, mineral particle concentrations, and stable isotopic ratios in the precipitations collected from both Muztagata and Dunde ice cores. The Muztagata ice core revealed seasonal response patterns for both live and total cell density, with high cell density occurring in the warming spring and summer months indicated by the proxy value of the stable isotopic ratios. Seasonal analysis of live cell density for the Dunde ice core was not successful due to the limitations of sampling resolution. Both ice cores showed that the cell density peaks were frequently associated with high concentrations of particles. A comparison of microbial communities in the Dunde and Muztagata glaciers showed that similar taxonomic members exist in the related ice cores, but the composition of the prevalent genus-related groups is largely different between the two geographically different glaciers. This indicates that the micro-biogeography associated with geographic differences was mainly influenced by a few dominant taxonomic groups.

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Abstract. Microorganisms are continuously blown onto the glacier snow, and thus the glacial depth 10 profiles provide excellent geographic archives of the microbial communities. However, it is uncertain 11 about how the microbial communities respond to the climatic and environmental changes over the glacier 12 ice. In the present study, the live microbial density, stable isotopic ratios, 18 O/ 16 O in the precipitation, and 13 mineral particle concentrations along the glacial depth profiles were collected from ice cores from the 14 Muztagata glacier and the Dunde ice cap. Six bacterial 16S rRNA gene clone libraries were established 15 from the Dunde ice core. The Muztagata ice core presented seasonal response patterns for both live and 16 total cell density with high cell density occurring in the warming spring and summer. Both ice core data 17 showed a frequent association of dust and microorganisms in the ice. Genera Polaromas sp., Pedobacter 18 sp, Flavobacterium sp., Cryobacteriium sp., and Propionibacterium/Blastococcus sp. frequently appeared 19 at the six tested ice layers, and constituted the dominant species endemic to the Dunde ice cap, whereas 20 some genera such as Rhodoferax sp., Variovorax sp., Sphingobacterium. sp., Cyanobacterium sp., 21Knoellia sp., and Luteolibacter sp. rarely presented in the ice. In conclusion, data present a discrete 22 increase of microbial cell density in the warming seasons and biogeography of the microbial communities 23 associated with the predominance of a few endemic groups in the local glacial regions. This reinforces our 24 hypothesis of dust-borne and post-deposition being the main agents interactively controlling microbial 25 load in the glacier ice. 26

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