Salinization impact on methane cycle

Salinization of freshwater ecosystems due to climate change poses significant challenges to microbial communities involved in crucial biogeochemical processes, such as the methane cycle. This study investigated the impact of salinity on the distribution and abundance of methanogens, methanotrophs, and sulfate-reducing bacteria (SRBs) in a freshwater lake Using 16S amplicon sequencing, q-PCR, and metagenome analysis, this research examined microbial communities in both surface sediments and sediment cores. Significant variations in the microbial diversity of methanotrophs were observed between the lake's cove and inlets, with ANME-1 becoming dominant in the regions affected by salinization. The appearance of the sulfate-methane transition zone at specific depths in the sediment cores further indicated changed dynamic competition between SRBs and methanogens in response to varying salinity conditions. Co-occurrence network analysis revealed the presence of potential syntrophic relationships between ANME-1 and SEEP-SRBs, indicating the generation of intricate microbial interactions during salinization. Moreover, the study highlighted the potential for physiological adaptability of all three functional groups to increased osmotic stress, supported by the presence of osmoregulatory genes and osmoprotectant biosynthesis. These findings provide valuable insights into the microbial adaptive responses to salinization in freshwater environments, emphasizing the importance of understanding and managing its impacts on key microbial players. Such knowledge is vital for preserving precious freshwater resources and comprehending the changes in the methane budget that arise in the face of salinization, addressing the challenges posed by climate change.