[Seasonal dynamics and driving factors of soil CH4 production potential and emission fluxes in aquaculture ponds of the Minjiang River Estuary].

Coastal aquaculture ponds are sources of methane (CH4), which are non-negligible in regional greenhouse gas budgets. However, the seasonal dynamics of CH4 production and emission in these systems, as well as the driving factors, remain poorly understood. We explored the seasonal variations of soil CH4 production potential, water gas interface CH4 emission flux, and related environmental factors in the cultivation pond formed by natural salt marsh wetland reclamation at the mouth of the Minjiang River, by combining in situ field observations and laboratory cultivation experiments. Results showed that soil CH4 production potential ranged from 8.78 to 60.44 ng·g-1·d-1 and water-air interface CH4 emission flux ranged from 18.58 to 194.74 μmol·m-2·h-1, with seasonal coefficients of variation of 65.8% and 79.9%, respectively. Both variables exhibited seasonal dynamics, following the consistent order of summer>autumn>spring>winter. Soil CH4 emission peaked in summer and autumn. Soil CH4 production potential was positively correlated with water-air interface CH4 emission flux in the aquaculture ponds, indicating that methanogenesis in soils was a key factor regulating CH4 emission across the water-air interface. Random forest analysis identified soil temperature, dissolved organic carbon, microbial biomass carbon, SO42-, and the gene abundances of methanogens and methanotrophs as the primary drivers controlling the seasonal dynamics of CH4 production and emission. Overall, CH4 emissions from coastal aquaculture ponds were dominated by a warm-season peak, with substrate supply as the primary driver. Given that feed input is the main source of organic matter and nutrients in aquaculture ponds, it directly determines the available supply of substrates. In the future, emission reduction should focus on optimizing feed utilization efficiency in summer and autumn, achieving a synergistic improvement of CH4 emission reduction and aquaculture benefits.