Ocean acidication The Great Barrier Reef has lost half its coral cover in the past thirty years

Most of that loss is due to storms, crown-of-thorns starsh, and bleaching due to extended periods of increased summer sea temperature. However other factors are also contributing to the ability of the Reef to respond to and recover from these impacts. Ocean acidity has the potential to slow growth of coral and is likely to have a larger impact in the coming decades. About half of the extra carbon dioxide (CO2) that humankind is injecting into the atmosphere is being absorbed by the oceans. This anthropogenic CO2 is increasing the acidity of the oceans. What aect is this having today? What will be the impact on the Reef in coming decades? And how does it aect the Reef’s capacity for repair? Coral growth is slowing on the Reef and around the world We know this from studies of long coral core records. Coral growth can be measured by coral calcication—the speed at which their calcium carbonate skeleton is deposited. Sustained calcication is essential for coral recovery, and for repair to the Reef after physical erosion (such as from storms) and biological erosion. The decline in coral calcication between 1990 and 2005 is unprecedented in at least the past 400 years. The recent slowing of coral growth rates has also been reported for several other reef locations around the world. The observed decline in calcication is likely to be warming seas. Laboratory experiments indicate that future declines in calcication will be driven by both ocean warming and acidication