What is the use of solubility of oxygen and carbon dioxide in water ?

Solubility of O₂, and CO₂ in water is important for the following reasons:

1. Marine life like fish use the oxygen of the air dissolved in water for respiration and thus aquatic life is sustained. 1 dm³ (1 litre) of water contains 40 cm³ of dissolved oxygen.
2. Aquatic plants make use of dissolved carbon dioxide for photosynthesis, i.e., to prepare their food.
   6CO₂ + 12H₂O $\xrightarrow[\text{sunlight}]{\text{Chlorophyll}}$ C₆H₁₂O₆ + 6O₂ + 6H₂O
3. Carbon dioxide dissolved in water reacts with limestone to form calcium bicarbonate.
   CaCO₃ + CO₂ + H₂O ⟶ Ca(HCO₃)₂
   Marine organisms such as snails, oysters, etc., extract calcium carbonate from calcium bicarbonate to build their shells.