The combined effect of pH and dissolved inorganic carbon concentrations on the physiology of plastidic ciliate Mesodinium rubrum and its cryptophyte prey.

Ocean acidification is caused by rising atmospheric partial pressure of CO (pCO) and involves a lowering of pH combined with increased concentrations of CO and dissolved in organic carbon in ocean waters. Many studies investigated the consequences of these combined changes on marine phytoplankton, yet only few attempted to separate the effects of decreased pH and increased pCO. Moreover, studies typically target photoautotrophic phytoplankton, while little is known of plastidic protists that depend on the ingestion of plastids from their prey.