Elevated CO2 effects on morphology and survival rate in intertidal benthic foraminifera

Oceans are absorbing about one-third of the anthropogenic CO2 from the atmosphere, and the excess CO2 leads to reduce the seawater pH, carbonate ion concentrations and saturation states of biologically important calcium carbonate minerals. The ocean acidification affects many calcifying organisms such as foraminifera. The present study assessed experimentally modified ocean pH impacts on survival rate and shell morphology variation in three species of intertidal benthic foraminifera. Foraminifera was collected from Parangipettai coastal waters, Tamilnadu, India. Foraminiferal specimens were cultured for a period of five weeks at three different pH treatments that replicated future scenarios of a high CO2 and low pH. The experimental results revealed that reduction of seawater pH significantly affected foraminiferal survival and morphology. Scanning Electron Microscopic observations revealed significant changes in foraminiferal morphology with clear evidence of dissolution and cracking processes on the test surface, and reduction in teeth structure in treatments with decreasing pH. Hence, altering the seawater chemistry might have extensive impacts on benthic foraminifera.