Bacterial Communities Present Distinct Co-occurrence Networks in Sediment and Water of the Thermokarst Lakes in the Yellow River Source Area

Abstract

Thermokarst lakes are a ubiquitous and important landscape feature in cold regions and are changing tremendously due to the accelerated climate change. In thermokarst lakes, sediment and water are two distinct but highly interconnected habitats, harboring different bacterial communities in terms of taxonomic composition. However, the co-occurrence networks of these bacterial communities remain unclear. Here, we investigate the co-occurrence ecological networks of sediment and water bacterial communities for thermokarst lakes in the Yellow River Source Area on the Qinghai-Tibet Plateau. The results show that the bacterial communities construct distinct co-occurrence networks in sediment and water. The metacommunity network was parsed into four major modules formed by the operational taxonomic units (OTUs) enriched in sediment or water independently, and water-enriched OTUs exhibited much closer interconnections than sediment-enriched OTUs. When considering the sediment and water bacterial networks separately, different topological properties and modular patterns present: the sediment bacterial network was more clustered while the modules less responded to the environmental variables. On the contrary, the water bacterial network was more complex with the OTUs more interconnected and its modules more responded to the environmental variables. Moreover, the results of the structural equation model suggest that, by the influence of environmental variations on individual modules, the water bacterial communities would be more vulnerable under the fact of accelerating climate change. This study provides insights beyond a conventional taxonomic perspective, adding our knowledge of the potential mechanisms structuring bacterial community assembly and improving our prediction of the responses of this fast-changing ecosystem to future climate change.

Differences in bacterial diversity, composition, and community networks in lake water across three distinct regions on the Qinghai-Tibet Plateau

“…For bacterial networks, only OTUs with average of relative abundance larger than 0.01% that exist in at least 50% of all samples in each region were chosen to construct the bacterial network . Furthermore, the relationships between OTUs with Spearman's correlation coefficient r > 0.8 or r < −0.8 and Benjamini-Hochberg p < 0.01 were selected for network construction (Zhao et al, 2016;Ji et al, 2019;Ren et al, 2021b). Networks were analyzed and visualized using the "igraph" package and Gephi platform (https://gephi.org/) (Zhou et al, 2019).…”

Abundant and Rare Bacterial Taxa Structuring Differently in Sediment and Water in Thermokarst Lakes in the Yellow River Source Area, Qinghai-Tibet Plateau

“…These two habitats host different assemblages of microorganisms with tremendous diversity, which play vital roles in maintaining and driving ecosystem structure and processes ( Lozupone and Knight, 2007 ; Roeske et al, 2012 ; Ren et al, 2019 ). Moreover, the variations of bacterial communities in sediment and water are driven differently by a variety of factors ( Gasol et al, 2002 ; Simek et al, 2008 ; Ren et al, 2019 , 2021a ). For thermokarst lakes, their formation (permafrost thaw) and evolution (horizontal and vertical permafrost degradation) mechanisms suggest that sediment and water have very close relationships in thermokarst lakes.…”