Monitoring ocean acidification is important because changes in the ocean's carbonate chemistry can have a major impact on the plant and animal life present in the ocean. For organisms with external calcium carbonate skeletons, such as corals and pteropods, the consequences can be very negative if the oceans become undersaturated (corrosive) with respect to aragonite, a form of calcium carbonate. It has been demonstrated that pteropods, a planktonic mollusk, may not be able to maintain their shells in undersaturated waters. In some studies, live pteropods were subjected to waters that are undersaturated with respect to aragonite and their shells begin to dissolve within 48 hours (Feely et al., 2004; Orr et al 2005 ). Image of Ocean Acidification Color Bar This dataset has both historic and forecasted model-based changes in the ocean's carbonate chemistry due to increasing CO2 levels, as well as the presence of coral reefs depicted. The coral reefs are represented by black X's for shallow water species and magenta X's for deep water species. The ocean acidification levels are based on the median model output of the 13 international ocean carbon models based on the OCMIP-2 Project (Orr et al. 2005). The model outputs are represented on the global map in 5-yr increments from 1765 thru 2100. The future changes in CO2 chemistry were determined based on atmospheric CO2 scenarios presented in The Intergovernmental Panel on Climate Change (IPCC) IS92a 'continually increasing' CO2 <b>...</b>