The world's coral reefs will begin to disintegrate before the end of the century as rising carbon dioxide levels in the atmosphere make the oceans more acidic, scientists have warned. New research points to a looming transition in the health of coral ecosystems during which the ability of reefs to grow is overwhelmed by the rate at which they are dissolving. More than 9,000 coral reefs around the world are predicted to disintegrate when atmospheric carbon dioxide levels reach 560 parts per million. The amount of carbon dioxide in the atmosphere today stands at around 388ppm, but is expected to reach 560ppm by the end of this century. Coral reefs are at the heart of some of the most biodiverse marine ecosystems in the world. They are home to more than 4,000 species of fish and provide spawning, refuge and feeding areas for marine life such as crabs, starfish and sea turtles. "These ecosystems which harbour the highest diversity of marine life in the oceans may be severely reduced within less than 100 years," said Dr Jacob Silverman of the Carnegie Institution in Stanford University, California. Coral reefs grow their structural skeletons by depositing aragonite, a form of calcium carbonate, from calcium ions in sea water. As oceans absorb atmospheric carbon dioxide, they become so acidic the calcium carbonate dissolves. Silverman's team studied a coral reef in the northern Red Sea and calculated its response to increasingly acidic waters. The research showed that the ability of the coral to build new structures depended strongly on water acidity and to a lesser extent temperature. From this data the researchers created a global map of more than 9,000 coral reefs, which showed that all are threatened with disintegration when carbon dioxide levels in the atmosphere reach 560ppm.