Effects of anthropogenic activities on soil microbial communities and greenhouse gas fluxes in coastal wetlands of the Yellow River Delta, China.

Coastal wetlands are key emitters of greenhouse gases (GHGs). Anthropogenic activities can alter the carbon and nitrogen cycle patterns in wetlands, thereby greatly affecting GHG fluxes. Previous studies have focused only on the effects of a single anthropogenic activity, thus, the effects of multiple anthropogenic activities on GHG fluxes and the underlying microbiological mechanisms remain unknown. Compared to natural reed areas (NA), our study investigated the four typical anthropogenic activities (Yellow River farmland (YA), sewage outfalls (SA), mariculture (MA), and oil extraction areas (OA)) in the coastal wetlands of the Yellow River Delta, showing that the anthropogenic activities enhanced nitrification (51.33 times NA), denitrification (25.77 times NA), methanogenesis (1.02 times NA), methane oxidation (7.87 times NA), and carbon sequestration (3.36 times NA) functional potentials. These activities significantly increased the nitrous oxide (0.07-1.14 mg/(m2·hr)) and carbon dioxide fluxes (198.1-6240.10 mg/(m2·hr)), and significantly decreased the methane fluxes (-41.84 to 36.28 mg/(m2·hr)), resulting in an increase in the carbon dioxide (CO2)-dominant global warming potential (GWP) (0.22-4.81 kg CO2/year). The higher GWP risks were observed in YA and OA. Stochastic processes dominated the microbial community assembly. Niche breadth was narrowed, resulting in the evolution of numerous idiosyncratic species, enhancing the intricacy and stability of microbial networks. Crucially, our findings highlight actionable pathways for climate mitigation: prioritizing emission controls in agriculture and oil sectors and optimizing coastal zoning policies. These insights bridge mechanistic understanding with scalable solutions for coastal wetland sustainability and climate governance.