Abstract

Global warming accelerates glacier melt, releasing stored carbon and nitrogen, which fertilize downstream ecosystems. Diverse and active microbial communities mediate biogeochemical cycles in snow and are vital to the glacial ecosystem. However, little is known about their temporal changing pattern and the environmental and biotic determinants in snowpacks. Here, we investigated the bacterial community in the surface and subsurface snow (depth at 0–15 and 15–30 cm, respectively) during a nine-day period in the Dunde Glacier of the Tibetan Plateau, based on Illumina MiSeq of 16S rRNA gene sequences. Our results revealed dynamic bacterial communities in both surface and surface snow, and nitrogen is the key determinant of bacterial diversity, composition, community structure, and biotic interactions. Nitrate and ammonium concentration increased and decreased in the surface and subsurface snow over time, therefore indicating accumulation and consumption processes, respectively. This is also evidenced by the dominance of organisms predicted to carry nitrogen fixation and denitrification genes in the surface and subsurface layers, respectively. The nitrogen limitation and the apparent dominance of the denitrification in the subsurface snow suggest stronger environmental and biotic filtering than those in the surface snow. This was associated with lower bacterial diversity, more pronounced community temporal changes, and stronger biotic interactions than in the surface snow. Collectively, these findings significantly advanced our understanding of microbial community variations and bacterial interactions after snow deposition, and revealed the dynamics of nitrogen metabolism in Tibetan snow.

Highlights

  • Global warming accelerates glacier melting across the globe, and the nutrients stored in glaciers are released into downstream ecosystems in melt waters (Hodson et al, 2005; Wadham et al, 2019)

  • Our results revealed dynamic bacterial communities in both surface and surface snow, and nitrogen is the key determinant of bacterial diversity, composition, community structure, and biotic interactions

  • Our results demonstrated the key roles of nitrogen in shaping the bacterial community in Tibetan glacial snow

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Summary

Introduction

Global warming accelerates glacier melting across the globe, and the nutrients stored in glaciers are released into downstream ecosystems in melt waters (Hodson et al, 2005; Wadham et al, 2019). Been reported in snow environments including Bacteroidetes, Actinobacteria, Firmicutes, and Alphaproteobacteria (Miteva, 2008; Maccario et al, 2019; Carey et al, 2016; Lazzaro et al, 2015; Michaud et al, 2014). These microorganisms perform key ecological functions in biogeochemical cycles such as carbon and nitrogen fixation, which are vital to nutrient-limited 35 glacial ecosystems. Changes in their community composition and activities are expected to influence the dynamics of glacial nutrient-storage and release. It is crucial to understand how the microbial community in glacial snow changes across time and to determine whether those changes are associated with the temporal nutrient differences in snow, to fully estimate the ecological consequences of global glacier melting

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