Distinct Phototrophic Community Structure on a Central Asian Glacier: Predominance of Filamentous Cyanobacteria and Absence of Glacier Algae (Ancylonema spp.)

Abstract. Cold-adapted algae and cyanobacteria are key drivers of snow and ice albedo reduction, yet their dynamics on dust-rich Central Asian glaciers remain poorly understood compared to the well-documented algal blooms in the Arctic. This study investigated the spatio-temporal distribution of phototrophic communities on Urumqi Glacier No.1, eastern Tien Shan, during a two-month melt season. Our findings reveal a distinct seasonal succession where snow-covered surfaces were dominated by snow algae Chloromonadinia species (Chlorophyceae), while the exposure of bare ice led to a sharp increase in biomass dominated by filamentous cyanobacteria (Oscillatoriaceae). Notably, glacier algae such as Ancylonema spp., which drive darkening on Arctic ice, were entirely absent, suggesting a fundamental ecological divergence. Statistical analyses indicated that cyanobacterial proliferation is closely linked to environmental factors, showing significant positive correlations with mineral-derived ions and negative correlations with inorganic nitrogen. These results, supported by recent evidence that specialized cyanobacterial taxa drive the initiation and structural development of cryoconite granules, suggest that high mineral dust deposition from surrounding arid regions facilitates a stable, nutrient-limited niche for cyanobacteria. This "cyanobacteria-mineral synergy" creates a more persistent biological darkening effect than the ephemeral algal blooms observed in polar regions. Our study highlights the necessity of integrating region-specific microbial dynamics, which is characterized by the absence of glacier algae and the dominance of mineral-buffered cyanobacterial communities, into glacier mass balance models to improve the accuracy of future projections for Central Asian water resources.