Science

Coral Reefs and Carbon Dioxide
Increasing ocean acidity threatens coral reefs worldwide

Coral reefs are one of the most biologically diverse ecosystems present on earth. Within the hard reefframework of limestone, built by coral animals and their symbiotic zooxanthellae plants, are habitats for at least 25 percent of all marine species. In addition to their intrinsic natural value, coralreefs provide important benefits to society from tourism, fisheries and coastline protection during storms. Recent estimates suggest that the net economic benefit of the world's coral reefs isapproximately $30 billion annually.



Rising levels of carbon dioxide in the atmosphere are causing the acidity of the world's oceans to increase and threatening the future of our coral reef ecosystems.Over the last few decades, at least 10% of tropical and subtropical coral reefs have been lost, and those that remain show signs of moderate to severe deterioration. The degradation of the world'scoral reefs has been caused by a host of human-related (anthropogenic) factors, including urban coastline development and habitat modification, pollution, nutrient and sediment overloading, directdestruction, and over-fishing. These environmental pressures, along with natural phenomena, such as El Niño events, increase the susceptibility of corals to disease and bleaching, when corals lose theirzooxanthellae partners.
The long-term sustainability of these valuable coral reefs is also threatened by global climate change induced by the release of carbon dioxide into the atmosphere from humanactivities. Rising ocean temperatures have been implicated in coral disease and mass coral bleaching, and worldwide research efforts have been targeted at understanding the interactions and impacts oncoral reef ecosystems from global warming, rising sea levels and anthropogenic factors. But a hidden danger to the long-term sustainability of the world's coral reefs has recently emerged: the...