Carbon dioxide inhibiting growth calcium-carbonate based animals

You’ve heard,
carbon dioxide is a polluting agent.
carbon dioxide causes global warming.
carbon dioxide is the gas that we breathe out.

but did you know that increase concentrations of CO₂ harm near-surface marine creatures that exoskeletons’ are carbonate based?

Examples are:
Marine animals with shells like crabs, lobsters and clamps. Not forgetting coral reefs.

Basically high concentrations of CO₂ will diffuse into the ocean and of which, this diffusion will alter the chemical equilibrium in the ocean, changing the pH value of current 8.7 to slightly acidic which is unfavourable to a variety of marine creatures which inhibits their growth, typically impacting carbonate based marine creatures.

Firstly, we need to know how shells are being formed:
Calcium + Carbonate –> Calcium carbonate (shell)
Ca⁺ + CO₃^- –> CaCO₃

 

Secondly,
Carbon dioxide + Water –> Carbonic acid
CO₂ + H₂O –> H₂CO₃

and since carbonic acid is a weak acid, it partially ionises in water (the ocean) to dissociate the hydrogen ions: H₂CO₃ <–> HCO₃^- + H⁺

as more carbon dioxide is diffused, the concentration of hydrogen ions (H⁺) increase resulting to a decrease in pH value to slightly acidic. As more hydrogen ions increase, more hydrogen ions will react with carbonate to form bicarbonate.

 

CO₃^- + H⁺ <–> HCO₃ (bicarbonate)

as more hydrogen ions react with carbonate, the concentration of carbonate (CO₃^-) decrease.

This result to the difficulty of marine creatures forming their exoskeletons’ due to decrease concentration of CO₃^-

Calcium + Carbonate –> Calcium carbonate (shell)
Ca⁺ + CO₃^- –> CaCO₃

lastly, as pH value decrease, the dissolution of CaCO₃ increase. That means….

 

 

Okay! enough of revision for tomorrow’s applied chemistry understanding test.