Nutrient removal and CO₂ fixation potential of Sesuvium portulacastrum ecological floating beds: Mechanistic...

The absence of a mechanistic quantitative framework that captures plant responses to dynamic environmental conditions limits accurate prediction of the remediation performance of ecological floating beds (EFBs) in aquaculture tailwater. In this study, a Dynamic Energy Budget model coupled with salinity stress was developed for the halophyte Sesuvium portulacastrum and applied to quantify the nutrient removal and CO₂ fixation potential of S. portulacastrum EFBs, as well as the effects of salinity on plant growth, nutrient removal and CO₂ fixation. The model accurately reproduced both growth dynamics and variations in tissue organic carbon, organic nitrogen, and organic phosphorus contents (mean R² = 0.95; NRMSE = 9.26%). During a 105-day cultivation period in a seawater pond with a mean salinity of 29.98 ppt, EFBs biomass increased from 79.1 to 174.2 g dry weight m^-2, with cumulative removal of 0.602 g N m^-2 and 0.089 g P m^-2, and CO₂ fixation of 138.5 g m^-2. Model simulations identified 7.40 ppt as the optimal salinity, at which biomass, nutrient removal, and CO₂ fixation increased by 93%, 301%, and 174%, respectively, compared with the pond salinity condition. These results provide a mechanistic basis and a quantitative predictive tool for evaluating and optimizing the large-scale application of S. portulacastrum EFBs for aquaculture tailwater treatment.