Coral reefs are most affected by acid rain, which can lower the pH of ocean water and harm coral structures.

Coral reefs are particularly vulnerable to acid rain, as the acidification of the ocean water due to increased atmospheric CO2 can negatively impact the ability of corals to build their calcium carbonate skeletons. Acid rain, which is caused by the emission of sulfur dioxide and nitrogen oxides, leads to an increase in the acidity of both rainwater and ocean water, further exacerbating coral bleaching and weakening reef structures. While wetlands, salt marshes, and mangrove forests can also be impacted by environmental changes, coral reefs are especially susceptible to the effects of ocean acidification caused by acid rain.