Coral Reef Glue May Not Stick Under Climate Change

Tag : liquid carbon dioxide
The cement that buttresses coral reefs, giving them thestrength to withstand crashing waves and other onslaughts, may stopforming as oceans acidify under increased carbon dioxide in theatmosphere.
Researchers have already predicted that a more acidic ocean willmake it more difficult for corals to build their calcium carbonate skeletons . The new finding suggests that the reef's broader structure mayalso suffer because a lower pH reduces the formation of the reef'scement binder. The binder is made from calcium carbonate thatprecipitates out of ocean water when it rushes through the pores ofcoral skeletons.
"Until now, we've mostly addressed acidification in terms of whatit does to the living organism," said study author Joan Kleypas ofthe National Center for Atmospheric Research in Boulder, Colo.
"Here we're finding that the reef structure itself can certainlyfeel the effect of ocean acidification , even if the biology somehow finds a way to cope withacidification. This is mainly an inorganic process, so we'relooking at something that will happen regardless of what thebiology does."
The researchers made their findings by comparing places around theworld where CO2 levels in the ocean vary naturally.
The eastern tropical Pacific Ocean, near the Galapagos Islands, hasparticularly high CO2 concentrations because it is an upwellingspot where deeper waters, enriched in CO2 by microbial degradationof organic matter down below, rise to the surface.
"The eastern Pacific is in essence a natural laboratory to studyhow coral reef ecosystems are structured and function under these acidic conditions," saidstudy author Derek Manzello of the University of Miami.
The researchers made measurements of the seawater and the amount ofcoral cement present in reefs near the Galapagos, and comparedthose with levels found near the Pacific coast of Panamá,and with those in the Bahamas.
Reefs in the Galapagos had the highest levels of carbon dioxide,which corresponded to water less saturated with carbon dioxide -- and only trace amounts of cement on the reefs.