, H₂CO₃, HCO_{At a pH of between 8.2–8.4, is the predominant component (approximately 90%), and free CO2 contributes less than 1%. a, most of which is characterized by high carbonate alkalinity (CA) concentrations. Since high CA isa major stressor for living organisms, most of these saline-alkali water areas have little evidence of life. To take advantage of this unexploited resource,researchers have trialed the use aquatic plants to reduce the concentration in saline-alkali waters. The seaweed Zhang et Xia is characterized by rapid growth and easy cultivation. The objective of this study was to investigate the effects of high HCOconcentrations on the growth, physiology, and biochemistry of to provide basic information for the development of saline-alkali water using macroalga. were grown for 10 d in a 250 mL Erlenmeyer flask containing 200 mL culture medium with ^{among the different treatment groups. The water temperature(25), salinity (20), initial pH (8.2-8.4), light intensity (5 000 lx), light-dark cycle (12D12h), and algae density (5 g/L) were the same for all groups. The specific growth rates (SGR) of concentration groups were significantly higher than in the control after 10 d exposure (. The effect may have been mediated by an increase in the available carbon (e.g., CO2) in the water. The increase in} the SGR and superoxide dismutase (SOD) and peroxidase (POD) activity increased in increased from 1.8 to 24 mmol/L, then decreased in the range between 24 to 48 mmol/L. content was significantly correlated with the content of chlorophyll a (<0.01), phycoerythrobilin, carotenoids, and . <0.05), but not with the content of photosynthetic pigments, suggesting that the concentrations appear to be beneficial by increasing the availability of inorganic carbon for the photosynthesis. However, the tradeoff is the production of , reduces the synthesis of photosynthetic pigments, and causes damage to the membrane system. The antioxidant defense system appeared to protect concentrations of <24 mmol/L. However, antioxidant activity (e.g., SOD and POD) was significantly impaired mmol/L, suggested the defense system was damaged. As a result, the SGR of mmol/L appear to be detrimental}