Determinants of microbial community structure in supraglacial pools of the Tibetan Plateau

Authors: FAIR, HEATHER - University Of Minnesota; HAMILTON, TRINITY - University Of Minnesota; Smiley, Peter - Rocky; QIAO, LIU - Chinese Academy Of Sciences

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Supraglacial pools are aquatic habitats found on debris-covered glaciers worldwide. Information on microbes that inhabit these ephemeral aquatic habitats and their habitat relationships is not available. We measured physical and chemical variables and sampled microbes and invertebrates from supraglacial pools on a debris-covered glacier in southeastern Tibet over two summers. Microbes were also sampled from glacial stream pools. We documented that supraglacial pools contained microbes that are not common in cryoconite holes of clean glaciers. Microbial diversity and the abundance of selected types of microbes were correlated with the abundance of larval midges, conductivity, and turbidity. Additionally, the relative abundance of different microbes did not differ between supraglacial pools and glacial stream pools. These results also represent the first documentation of the relative abundance of different microbes and their habitat relationships in supraglacial pools on debris covered glaciers in China that will be of much interest to scientists working on glaciers worldwide. Our novel results will be of much interest to those involved with conservation of aquatic biodiversity in Asia because they provide information that can be used to predict changes in water quality and quantity that will impact microbial biodiversity within glacier aquatic habitats in the region. Our results combined with information from other studies from extreme habitat types (headwater streams, ephemeral wetlands) that experience cycles of drying and freezing will be of interest to state agencies, federal agencies, private consulting companies, and non-profits involved with the management of agricultural watersheds in the United States because they confirm the importance of a combination of biotic and water chemistry variables as determinants of microbial biodiversity within disturbance prone aquatic habitats.

Technical Abstract: Supraglacial pools are prevalent on debris-covered mountain glaciers yet less is known about the microbial communities within these meltwater habitats. Our research questions were: 1) what microbes occur in supraglacial pools of monsoonal Tibet?; 2) which abiotic and biotic habitat variables have the most influence on the microbial community structure?; and 3) does microbial taxa composition of supraglacial pools differ from that of glacial-melt stream pools? We collected microbial samples for 16S rRNA sequencing, invertebrates, and measured 22 abiotic and biotic environmental predictor variables from 46 supraglacial pools and nine glacial-melt stream pools in 2018 and 2019. Generalized linear model analyses, small sample Akaike information criterion, and variable importance scores were used to identify the best predictor variables of microbial community structure. Multi-response Permutation Procedure was used to compare taxa composition between supraglacial pools and stream pools. The most abundance phyla in supraglacial pools were Proteobacteria, Actinobacteria, Bacteroidota, and Cyanobacteria. Hill species richness, Hill Shannon diversity index, Hill Simpson diversity index, Bacteroidia relative abundance, and Chloroflexi relative abundance were best predicted by Chironomidae larvae. The relative abundance of Gammaproteobacteria, Cyanobacteriia, and Nanoarchaea were best predicted by either turbidity or conductivity. Taxa composition did not differ between supraglacial and stream pools. Our results indicate that Chironomidae larvae may play a greater role in shaping the biodiversity and abundance of bacterial communities of pools than anticipated and more research is needed evaluating the relationships among environmental factors, eukaryotes, bacteria, and fungi within supraglacial pools on debris-covered glaciers.