Co-occurrence patterns in aquatic bacterial communities acrosschanging permafrost landscapes

[摘要] Permafrost thaw ponds and lakes are widespread across the northern landscapeand may play a central role in global biogeochemical cycles, yet knowledgeabout their microbial ecology is limited. We sampled a set of thaw ponds andlakes as well as shallow rock-basin lakes that are located in distinctvalleys along a north–south permafrost degradation gradient. We appliedhigh-throughput sequencing of the 16S rRNA gene to determine co-occurrencepatterns among bacterial taxa (operational taxonomic units, OTUs), and thenanalyzed these results relative to environmental variables to identifyvariables controlling bacterial community structure. Network analysis wasapplied to identify possible ecological linkages among the bacterial taxaand with abiotic and biotic variables. The results showed an overall highlevel of shared taxa among bacterial communities within each valley; however,the bacterial co-occurrence patterns were non-random, with evidence ofhabitat preferences. There were taxonomic differences in bacterialassemblages among the different valleys that were statistically related todissolved organic carbon concentration, conductivity and phytoplanktonbiomass. Co-occurrence networks revealed complex interdependencies withinthe bacterioplankton communities and showed contrasting linkages toenvironmental conditions among the main bacterial phyla. The thaw pondnetworks were composed of a limited number of highly connected taxa. This“small world network” property would render the communities more robust toenvironmental change but vulnerable to the loss of microbial “keystonespecies”. These highly connected nodes (OTUs) in the network were not merelythe numerically dominant taxa, and their loss would alter theorganization of microbial consortia and ultimately the food web structureand functioning of these aquatic ecosystems.

[学科分类] 地球化学与岩石