Responses of Calcifying Algae to Ocean Acidification

In the open oceans, the most ecologically important calcifying phytoplankton are coccolithophores. There is considerable evidence that future high atmospheric CO₂ will affect calcification by marine calcifying algae, but the prediction on ecological destiny of calcifying algae in future high CO₂ oceans is still largely uncertain. From a chemical point of view, ocean acidification (OA) will decrease the saturation of biologically important CaCO₃ skeletons of calcifying algae. The growth conditions of planktonic and benthic calcifying algae depend on the carbonate chemistry. Calcifying algae may be facing even worse effects of OA under a background of varying dissolved inorganic carbon. But it is still unclear whether the results of these studies could be used to predict the ecological destinies of the calcifying algae growing in a complex and changing environment. The major direct effects of OA on photosynthesis are that the CO₂ could be used as a substrate of Rubisco, the key enzyme of carbon assimilation.