Question - Explain how increasing concentrations of atmospheric carbon dioxide threatens coral reefs.

Explain how increasing concentrations of atmospheric carbon dioxide threatens coral reefs.

Answer: 

Increased concentrations of dissolved carbon dioxide lowers ocean pH (more carbonic acid = more acidity).

More hydrogen ions also means there are less free carbonate ions for calcification (shell formation).

Hence, an increase in water acidity correlates with significant thinning of calcium exoskeletons.

Low pH conditions are also detrimental to polyp survival, leading to coral bleaching.