Ocean acidification
Changes in ocean carbonate chemistry driven by increasing anthropogenic carbon dioxide emissions promotes ocean acidification. Increasing the ocean carbon dioxide uptake results in increases in pCO2 (the partial pressure of carbon dioxide in the ocean) as well as lower pH levels and a lower carbonate saturation in the seawater. These affect the calcification process. Organisms like rhodoliths accrete carbonate as part of their physical structure, since precipitating CaCO3 would be less efficient. Ocean acidification presents a threat by potentially affecting their growth and reproduction. Coralline algae are particularly sensitive to ocean acidification because they precipitate high magnesium-calcite carbonate skeletons, the most soluble form of CaCO3.