Why is sea water a basic?

Seawater is considered slightly basic due to the presence of dissolved salts, particularly bicarbonate and carbonate ions, which can increase its pH. The average pH of seawater typically ranges from 7.5 to 8.5, making it alkaline compared to pure water, which has a neutral pH of 7. Additionally, the photosynthesis of marine plants consumes carbon dioxide, reducing its concentration in the water and contributing to the basicity.