How can such a wide–spread effect, like acidification associated with global climate change, be adequately addressed? Approximately half of the carbon dioxide (CO2) produced by human activity in the last 200 years has been taken up by the oceans. CO2 in the atmosphere is a chemically unreactive gas, but when it is dissolved in seawater, chemical changes occur. One overall effect is the formation of carbonic acid (H2O + CO2 = H2CO). This weak acid releases hydrogen ions into the seawater, which causes the acidity to increase (lowering the pH). The increase in ocean acidity has consequences for marine organisms that produce calcium carbonate (CaCO3). Marine life such as corals, molluscs, phytoplankton and zooplankton could be severely impacted, causing a ripple effect through the entire marine food chain.