November 9th, 2015
Every coral reef in the world will probably die off by the end of this century unless the production of carbon dioxide is curtailed severely, researchers from the Carnegie Institution for Science report. Accelerated carbon dioxide production is making the oceans more acidic, thus preventing the basic skeletons of coral reefs from being made.
Ken Caldeira (pictured, right) and Katharine Ricke reported in the July 3 Environmental Research Letters that, according to several computer models they created to predict the effects of a more acid ocean, coral reefs will be unable to sustain themselves unless emissions are curtailed soon and carbon dioxide is somehow captured from air. All the other models, which ranged from business as usual (no changes in carbon production) to some curtailment by late century, predicted an end to coral reefs.
Acidification affects the mineral aragonite, a form of calcium carbonate that corals use to make their skeletons. When carbon dioxide comes into contact and is absorbed by the ocean, carbonic acid is formed. This decreases the ocean’s pH, and this acidity makes the creation of aragonite much harder to do.
Caldeira and Ricke used models that include ocean conditions that occur under their three different scenarios. Specifically, they measured dissolved inorganic carbon, alkalinity (the opposite condition from acidity), sea surface temperature, and salt content. They then applied these models to water surround 6,000 coral reefs on the planet. They noted that before the industrialization of the world (see in the top image, left), nearly all reefs were located in areas with plenty of aragonite; already, scientists are reporting deadly bleaching of coral reefs (seen in the second image from top, left).
“If we continue on our current emissions path, by the end of the century there will be no water left in the ocean with the chemical properties that have supported coral reef growth in the past,” said Caldeira. “The decisions we make in the next years and decades are likely to determine whether or not coral reefs survive the rest of this century.”
Caldeira and his colleagues are now collecting data at several reef sites worldwide to see if their computer models indeed match with actual tests of ocean water chemicals.
Source: EurekAlert.com, Carnegie Institution
Photo, image: Ken Caldeira and Katharine Ricke
Ricke, K.L., Orr, J.C., Schneider, K., and Caldeira, K. (2013). Risks to coral reefs from ocean carbonate chemistry changes in recent earth system model projections Environmental Research Letters, 8
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