Nutrient removal and CO2 fixation potential of Sesuvium portulacastrum ecological floating beds: Mechanistic model-based assessment.

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.