Model assessment of nutrient removal via planting Sesuvium portulacastrum in floating beds in eutrophic marine waters:the case of aquaculture areas of Dongshan Bay

摘要

Many coastal seas are severely eutrophic and required to reduce nutrient concentrations to meet a certain water quality standard.We proposed a method for nutrient removal by planting Sesuvium portulacastrum at the water surface using the floating beds in the aquaculture area of the Dongshan Bay as an example,which is an important net-cage culture base in China and where dissolved inorganic nitrogen(DIN)and dissolved inorganic phosphate(DIP)reach 0.75 mg/L and 0.097 mg/L,respectively far exceeding China’s Grade IV water quality standards.Numerical simulations were taken using the ecological model,field observations and field plantation experimental results to assess the environmental restoration effects of planting S.portulacastrum at some certain spatial scales.Our field experiments suggested that the herbs can absorb 377 g/m^2 nitrogen and 22.9 g/m^2 phosphorus in eight months with an inserting density of^60 shoot/m^2.The numerical experiments show that the greater the plantation area is,the more nutrient removal.Plantation in^12%of the study area could lower nutrients to the required Grade II standards,i.e.,0.2 mg/L