Abstract
In polar and alpine regions, global warming and landform changes are draining lakes, transforming them into permafrost with altered microbial communities and element cycling. In this study, we investigated bacterial and archaeal (prokaryotic) community changes in the newly exposed sediment of Zonag Lake (Tibetan Plateau), focusing on prokaryotic diversity, community structure, and genes involved in carbon fixation and nitrogen cycling across lateral (up to 800 m) and vertical (up to 80 cm) horizons. The results showed that prokaryotic richness decreased across the lateral horizons, coinciding with reductions in carbon concentrations. Dramatic changes in community structure were also observed, primarily influenced by the distance from the lake and then by sediment depth, with environmental filtering and dispersal limitations shaping the lateral and vertical distributions, respectively. Based on PICRUSt2 results, the relative abundance of genes related to carbon fixation increased along the lateral horizon, suggesting that microbial carbon fixers are counteracting the carbon loss during permafrost formation. In contrast, the genes related to denitrification also increased, which may lead to nitrogen loss and contribute to global warming by releasing nitric oxide gas. This study highlights the resilience of prokaryotic communities in drained lake basins and their ecological implications under global warming.