that ocean acidification due to increasing concentrations of CO2 in the atmosphere may affect the calcification machinery of coccolithophores. This may not only affect immediate events such as increases in population or coccolith production, but also may induce evolutionary adaptation of coccolithophore species over longer periods of time. For example, coccolithophores use H+ ion channels in to constantly pump H+ ions out of the cell during coccolith production. This allows them to avoid acidosis, as coccolith production would otherwise produce a toxic excess of H+ ions. When the function of these ion channels is disrupted, the coccolithophores stop the calcification process to avoid acidosis, thus forming a feedback loop. Low ocean alkalinity, impairs ion channel function and therefore places evolutionary selective pressure on coccolithophores and makes them (and other ocean calcifiers) vulnerable to ocean acidification. In 2008, field evidence indicating an increase in calcification of newly formed ocean sediments containing coccolithophores bolstered the first ever experimental data showing that an increase in ocean CO2 concentration results in an increase in calcification of these organisms. Decreasing coccolith mass is related to both the increasing concentrations of CO2 and decreasing concentrations of CO32– in the world's oceans. This lower calcification is assumed to put coccolithophores at ecological disadvantage. Some species like Calcidiscus leptoporus, however, are not affected in this way, while the most abundant coccolithophore species, E. huxleyi might be (study results are mixed). Also, highly calcified coccolithophorids have been found in conditions of low CaCO3 saturation contrary to predictions. Understanding the effects of increasing ocean acidification on coccolithophore species is absolutely essential to predicting the future chemical composition of the ocean, particularly its carbonate chemistry. Viable conservation and management measures will come from future research in this area. Groups like the European-based CALMARO are monitoring the responses of coccolithophore populations to varying pH's and working to determine environmentally sound measures of control. Impact on microfossil record Coccolith fossils are prominent and valuable calcareous microfossils. They are the largest global source of biogenic calcium carbonate, and significantly contribute to the global carbon cycle. They are the main constituent of chalk deposits such as the white cliffs of Dover. Of particular interest are fossils dating back to the Palaeocene-Eocene Thermal Maximum 55 million years ago. This period is thought to correspond most directly to the current levels of CO2 in the ocean. Finally, field evidence of coccolithophore fossils in rock were used to