A transition in aquaculture systems: Industrial systems substantially reduce CO2 and CH4 diffusion versus traditional earthen ponds.

Quantifying carbon dioxide (CO2) and methane (CH4) fluxes from aquaculture is crucial for accurately assessing carbon biogeochemical cycling in aquatic ecosystems. Nevertheless, how aquaculture industrialization affects CO2 and CH4 emissions remains poorly understood. Here, we investigated the CO2 and CH4 concentrations and diffusive fluxes across three representative aquaculture systems in China's Jianghan Plain: industrial aquaculture system (IAS), semi-intensive aquaculture system (SIAS), and extensive lake-based aquaculture system (ELAS). Results showed that CO2 and CH4 diffusion fluxes were markedly lower in IAS (49.29 ± 10.34 mg CO2 m-2 h-1; 0.43 ± 0.10 mg CH4 m-2 h-1) than in SIAS (87.26 ± 17.81 mg CO2 m-2 h-1; 1.32 ± 0.29 mg CH4 m-2 h-1). These reductions may be attributable to the optimized system design and management practices (e.g., concrete liner, continuous aeration, and controlled feeding), which suppressed methanogenesis and respiration. When normalized by per unit of protein yield, IAS demonstrated an annual emission intensity merely 6.25 % of traditional systems (1:16 ratio), highlighting its significant potential for carbon reduction. Without considering initial costs and energy consumption, our findings suggest that scaling up modernized aquaculture represents a promising approach to simultaneously satisfying global aquatic protein demand and advancing carbon neutrality objectives, without necessitating additional land use.