Oceans are one of the major sequesters of natural as well as anthropogenic carbon dioxide. It is estimated that about one third of the carbon dioxide released in the atmosphere through human activity has been absorbed by the oceans. Recent studies indicate that in the past 250 years, anthropogenic carbon dioxide influence has changed the seawater carbonate chemistry that resulted into decrease of ocean pH (‘Ocean Acidification’). Model as well as instrumental measures predicted that, by end of this century concentrations of atmospheric carbon dioxide will rise from 400 μatm to over 750 μatm which will intensify changes in the ocean carbonate chemistry and lower the pH of the oceans. This increase in ocean acidification will affect the eco-physiology of marine ecosystems particularly calcifying organisms such as corals, foraminifera and coccolithophores which play a major role in the marine carbon cycle. In the other hand, an increase in atmospheric (subsequently oceanic) temperature will impact phytoplankton physiology, productivity and growth rates. Indirect effects such as enhanced thermal stratification will constrain nutrient availability and ultimately limit primary productivity in the sunlit ocean surface layer. Assessing coccolithophores’ key role in marine ecosystem studies on coccolithophores ecology and biogeography were carried out in the Southern Ocean between 2004 and 2017. Our studies document rapid shifting of biogeographic boundaries of coccolithophores with rapid frontal movements and adaptation of coccolithophores to lowering pH conditions south of the polar front. Based on our studies, we hypothesize that in the future, coccolithophores may show diverse responses to change in carbonate chemistry and ocean acidification. The coccolithophores will show variations in calcification and probably will replace calcium by magnesium to cope with the changing pH conditions. Tropical-subtropical phytoplankton communities will be dominated by lower photic zone coccolithophores which would possibly emerge as a different kind of ecosystem in these regions. Such changes could therefore have their own repercussions and could alter the marine carbon cycle and affect carbon sequestration in the near future.