Forecasting the rain ratio

Abstract

Marine algae known as coccolithophores produce much of the ocean's calcium carbonate. A large survey reveals how these organisms' calcification processes and species distribution change in response to carbon dioxide levels. See Letter p.80 The nature of the response of calcifying organisms, such as coccolithophores, to ocean acidification as a result of increasing atmospheric carbon dioxide is key to predictions of the future carbon cycle and its feedback on anthropogenic change. Laboratory experiments shed little light on the matter as they usually follow the response of a selected strain to just a few changed parameters. By analysing both contemporary surface water samples and fossil sediment cores, Beaufort et al. show that an increase in dissolved CO2 causes a decrease in calcification rates, and that the abundance of heavily calcified coccolithophore morphotypes is dependent on carbonate chemistry. The surprising discovery of heavily calcified Emiliania huxleyi in modern waters with low pH, however, indicates the complexity of the marine response to increasing CO2.