For the assessment of the long-term consequences of the carbon dioxide ocean sequestration, the CO₂ injection into the middle depth parts of the Pacific Ocean was simulated. The model consists of the essential processes, such as the ocean circulation developed by us, the solubility pump (CO₂ exchange flux across the atmosphere-ocean interface), the biological pump. The present major modifications from our previous model include the inclusion of the biological pump. This improvement enabled us to simulate the future CO₂ fate in the long-term using the more realistic model. Using this model, the CO₂ injection into the middle part of the ocean was simulated assuming the amount of CO₂ sequestered. Following results were obtained: (1) the present study could reveal the effectiveness of the direct ocean CO₂ sequestration, in relation to both selecting appropriate dumping depth, and evaluating the effect of CO₂ concentration to marine animals. (2) According to our model with a coarse grid mesh (2°× 2°), there would be less influence to the marine fish such as Pagrus major and Sillago japonica.