Temporal variation of bacterial community and nutrients in Tibetan glacier snowpack

Abstract

Abstract. The Tibetan Plateau harbors the largest number of glaciers outside the polar regions, which are the source of several major rivers in Asia. These glaciers are also major sources of nutrients for downstream ecosystems, while there is a little amount of data available on the nutrient transformation processes on the glacier surface. Here, we monitored the carbon and nitrogen concentration changes in a snowpit following a snowfall in the Dunde Glacier of the Tibetan Plateau. The association of carbon and nitrogen changes with bacterial community dynamics was investigated in the surface and subsurface snow (depth at 0–15 and 15–30 cm, respectively) during a 9 d period. Our results revealed rapid temporal changes in nitrogen (including nitrate and ammonium) and bacterial communities in both surface and subsurface snow. Nitrate and ammonium concentrations increased from 0.44 to 1.15 mg L−1 and 0.18 to 0.24 mg L−1 in the surface snow and decreased from 3.81 to 1.04 and 0.53 to 0.25 mg L−1 in the subsurface snow over time. Therefore, we suggest that the surface snow is not nitrogen-limited, while the subsurface snow is associated with nitrogen consumption processes and is nitrogen-limited. The nitrate concentration co-varied with bacterial diversity, community structure, and the predicted nitrogen fixation and nitrogen assimilation/denitrification-related genes (narG), suggesting nitrogen could mediate bacterial community changes. The nitrogen limitation and enriched denitrification-related genes in subsurface snow suggested stronger environmental and biotic filtering than those in surface snow, which may explain the lower bacterial diversity, more pronounced community temporal changes, and stronger biotic interactions. Collectively, these findings advance our understanding of bacterial community variations and bacterial interactions after snow deposition and provide a possible biological explanation for nitrogen dynamics in snow.

A comprehensive dataset of microbial abundance, dissolved organic carbon, and nitrogen in Tibetan Plateau glaciers

“…Microorganisms in glaciers are originated from atmospheric deposition, and it has been reported that microorganisms originating from the Saharan Desert have been found thousands of kilometers away in the Caribbean and European Alps (Kellogg and Griffin, 2006). The deposited microorganisms are subjected to a range of post-depositional environmental selection processes (Chen et al, 2022), until they are buried by snow and eventually frozen in the ice core. The microbial abundance in ice cores of the seven sampled glaciers varied substantially, ranging from 63 to 1 130 080 cells mL −1 , and the mean microbial abundances were 4389, 8617, 44 318, 23 311, 15 648, 27 330, and 19 656 cells mL −1 for MSTG, LHG, GLDD, CPG, ZQP, NJKS, and ERB, respectively.…”

Bacterial community distribution and functional potentials provide key insights into their role in the ecosystem functioning of a retreating Eastern Himalayan glacier

“…The complete dissimilatory nitrate-reducing and denitrifying genes in some of the MAGs suggest their potential for an anaerobic mode of respiration to better adapt to the changing environmental conditions. Denitrification is active in many other alpine glaciers (Chen et al 2022 , Murakami et al 2022 ). However, N fixation was not detected in the MAGs, as was observed in the Canadian High Arctic permafrost and Svalbard forefield MAGs (Wu et al 2021 , Tian et al 2022 ), which might suggest the minimal contribution of the process in the nitrogen cycle.…”