Balancing water use efficiency and carbon neutrality in mariculture: A multi-objective model for optimizing mariculture structure in China’s coastal provinces

Climate change poses a serious challenge to global food security and ecosystem stability. Past research has focused on optimizing the structure of agricultural farming systems, while mariculture, as an important player in food production and carbon cycle, urgently needs environmentally friendly and efficient management practices. This study proposes a multi-objective optimization model for sustainable mariculture system management, leveraging the water-energy-food-carbon nexus framework, aiming to optimize the configuration of mariculture structures under conditions of minimizing water footprint, maximizing food production and minimizing net carbon emissions. Firstly, the water and carbon footprints of each stage were evaluated based on life cycle assessment. Secondly, the carbon sequestration by shellfish and algae was calculated from biomass carbon and organic carbon deposition. Finally, an empirical study was conducted in China’s coastal areas. The high-dimensional adaptive whale optimization algorithm was applied to solve the complex model, and the optimal resource allocation strategy was determined using a membership function. The results indicate that shellfish and algae warrant a larger proportion of mariculture production. The mariculture structure in the best trade-off scheme effectively reduces the water footprint by 10.37 % and the carbon footprint by 2.17 %, while prioritizing increased grain production in regions with a comparative advantage in mariculture, such as Fujian, Liaoning, and Guangdong. In other optimization scenarios, the water footprint of the water-saving scheme decreased by 16.22 %, the grain yield of the high-yield scheme increased by 8.94 %, and the net carbon emissions of the low-carbon scheme were reduced by 2.86 %. The study also revealed significant differences in the carbon sink functions of various species. Oysters contributed 0.23 million tons of carbon sequestration, accounting for 31.2 % of the total. Additionally, Porphyra spp. exhibited the highest carbon sink intensity, reaching 1.57 kg CO 2 eq/kg. The research findings provide new pathways and practical references for optimizing resource management in mariculture systems and exploring low-carbon emission solutions to address challenges such as global climate change and resource shortages. • Proposed a systematic optimization model for mariculture species structure based on the Water-Energy-Food-Carbon Nexus. • Advanced dynamic evaluation of water footprints, carbon emissions and carbon sequestration via Life Cycle Assessment. • Developed an innovative algorithmic tool for global optimization challenges in large-scale resource-environmental systems. • The footprint structure differences across 10 coastal regions are significant. • The cultivation ratio of shellfish and algae can be further expanded.