Impact of Long‐Term Freshwater Replenishment on Soil Core Bacteria in Degraded Coastal Wetlands

The replenishment of freshwater stands as a critical method for restoring wetlands within the Yellow River Delta. Despite its significance, limited knowledge exists regarding the impact of freshwater replenishment on the structure of soil core microbial communities and the potential mechanisms governing microbial community composition in coastal wetland ecosystems. To bridge this gap, we conducted an analysis of the impact on soil core bacterial communities in both upper (0–10 cm) and deep (10–20 cm) soils following 3, 7, and 20 years of freshwater replenishment, comparing them with natural wetlands. The results revealed that the bacterial diversity and soil nutrients after 20 years of freshwater replenishment were significantly higher than those in plots with only 3 years of replenishment but notably lower than those in natural wetlands. This restoration approach contributed to the soil biodiversity and functional stability. Among the core bacteria, Pseudomonadota shows high abundance. With the increase in freshwater replenishment time, the community structure became more stable, and core bacteria are key. Prolonged freshwater replenishment significantly changed the topological properties of soil bacterial networks; bacterial networks with longer freshwater replenishment times were more complex. 16S rRNA sequencing predicted that the abundance of genes related to “nitrogen metabolism” and “anaerobic respiration” transformation increased after the replenishment of freshwater, as critical functions. Further annotation identified that the key functions were performed by specific bacterial taxa, including Methylophaga and Desulfuromonas. Further analysis showed that the regulation of core bacteria communities in the soil during the restoration process was predominantly governed by deterministic factors. The soil electrical conductivity value emerged as a key environmental factor influencing the soil core bacterial community during freshwater replenishment. Nutrient factors, including total carbon, available phosphorus, alkaline phosphatase, and sucrase, were significantly impacted. These results significantly contribute to our understanding of how soil core bacterial communities respond to freshwater replenishment, highlighting microbial aspects as key considerations for developing successful wetland restoration frameworks.