Microbial co-occurrence network characteristics and functional prediction of microbial communities in coal mining subsidence wetland sediments

Coal mining subsidence wetlands are crucial to farmland ecosystems in Eastern China plains, serving as important water conservation areas and biodiversity reservoirs in agricultural regions. How to perform their ecological functions is essential to the regional farmland ecosystems. High-throughput sequencing technology and microbial co-occurrence network analysis were employed to investigate coal-mining subsidence wetlands of three different formation ages, including Quanrun (QR), Jiuli (JL) and Pan'an (PA), revealing the network characteristics and functions of abundant and rare microbial communities. The results show that the α-diversity indices (Shannon and Richness) of rare bacterial and abundant fungal taxa exhibited consistent trends, significantly increasing with wetland formation age (JL>QR>PA, P < 0.05). The Jiuli group, representing the longest-formed coal-mining subsidence wetland, exhibited the significant network connectivity and other topological properties, indicating the highest network stability and complexity. The proportion of positive relationships among network nodes exceeded 50%, suggesting a cooperative trend among microbial taxa in the wetland. In the abundant bacterial networks, Proteobacteria accounted for 48.4% to 57.3% of the composition, serving as the dominant phylum. In the abundant fungal network, Ascomycota was the dominant phylum, accounting for 42.4% to 55.9%. Functional prediction based on FAPROTAX revealed that the sediment bacteria in coal-mining subsidence wetlands exhibited strong metabolic functions, which increased with wetland age. The dominant functional groups included chemoheterotrophy (11.78% to 17.27%), aerobic chemoheterotrophy (11.74% to 16.24%), and aromatic compound degradation (10.64% to 12.27%). Using Funguild to predict the functional roles of fungi in wetland sediments, the main functional group was found to be saprotrophs, with undefined saprotrophs accounting for approximately 20% relative abundance across all three wetland age groups. The high complex microbial networks and its multifunction of coal mining subsidence wetlands can facilitate ecological function restoration and reuse of these wetlands, holding significant importance for ensuring national food security and maintaining regional ecological safety.