Microbial metacommunity of salt marshes rebuilds along an elevational gradient after initial disturbance.

Salt marshes are ecologically important ecosystems with dynamic nutrient exchange between land and sea. Their zonation along an elevation gradient supports specific communities exhibiting successional patterns. Previous studies have mainly focused on individual domains, with limited attempts to explore interdependencies of community assemblies across domains. Here, we investigated the co-occurrence of prokaryotes and microeukaryotes in natural salt marsh sediments and experimental islands placed in the adjacent tidal flat. The islands contained originally bare and transplanted plots at three different elevations, corresponding to the typical salt marsh zonation. After initial disturbance by the artificial setting, microbial metacommunities re-assembled along the elevation gradient, showing distinct community compositions comparable to those of the natural salt marsh zones. Interkingdom co-occurrence network analysis revealed sub-communities linked to the natural and artificial settings, with Woeseiaceae, Flavobacteriaceae, and Rhodobacteraceae playing important roles as keystone species. The community assembly was primarily driven by habitat filtering. In conclusion, this study provides insights into the assembly, co-occurrence patterns and recovery of microbial communities in salt marsh sediments. The research highlights the importance of elevation in shaping microbial communities. Understanding these ecological mechanisms is crucial for effective salt marsh protection and conservation facing potential threats like strong disturbances by enhanced storm surges.