Significant response of microbial community to increased salinity across wetland ecosystems

Soil salinity can affect microbial activities and community structure, with broader implications for carbon storage and mineralization. However, a consensus on how soil microbial communities respond to elevated salinity has yet to be reached. With the increasing salinization of coastal lowlands, a comprehensive assessment of salinity-driven microbial community shifts is crucial for understanding and predicting shifts of biogeochemical processes in response to soil salinization. Here, we conducted a meta-analysis of 21 studies to investigate the changes in soil microbial communities along salinity gradients. We found a significant reduction of prokaryotic alpha-diversity indices with increasing salinity. Prokaryotic beta-diversity was altered by elevated salinity, but significant differences were only found between samples at < 1 and > 10 ppt salinity. Compared to non-saline conditions, high salt concentrations increased the relative abundance of Bacteroidetes and Proteobacteria by 17–19%, especially that of Alphaproteobacteria and Gammaproteobacteria, but generally inhibited the rest of the dominant phyla and classes. For fungi, Ascomycota was 1.3-fold more abundant in saline environments than in non-saline environments, but Basidiomycota was 21% less. This meta-analysis reveals significant changes of microbial community composition responding to environmental salinization. With strong biodiversity reduction under saline conditions, these dominant microbial groups with high-salinity niche preference will play a stronger role in regulating nutrient and energy flow, and constraining SOC dynamics.