Saturday, March 24, 2012
Global warming may be helping these creatures out, a new study finds. "To date, it is the changes in temperature that are having the dominant impact on coral growth," says Timothy Cooper, a marine biologist at the Australian Institute of Marine Science in Crawley.
Cooper and his colleagues collected samples of Porites coral at six spots off Australia in the southeastern Indian Ocean. Porites build skeletons with layers that, like tree rings, can measure growth.
None of the creatures had slowed their growth in the last 110 years, the team reports in the Feb. 3 Science. Those at the southernmost sites have even been building reefs faster as surface waters there have warmed markedly.
On the Great Barrier Reef, the same type of coral is stressed, previous work has shown. Porites grew 14 percent slower in 2005 than in 1990, a slowdown blamed on both warming waters and ocean acidification linked to rising carbon dioxide. About a third of all atmospheric carbon dioxide emissions are soaked up by the oceans, where the gas reacts to make carbonic acid. That lowers the water's pH and levels of dissolved carbonate, the raw material corals use to build skeletons.
Ocean acidification is expected to have a greater effect at some of the higher latitudes surveyed in the new study, where dissolved carbonate is less plentiful to begin with. But Cooper and colleagues found no sign that changing pH bothered the corals they sampled. Acidification may still be a problem in the long run, but for now temperature seems to be the bigger factor. Warmth seems to make the reef builders more productive.
"It is good to see some corals doing well in the warming," says marine biologist Charles Sheppard of the University of Warwick in Coventry, England. But he cautions that Australia's west coast may ultimately be heading for a downturn as well. Patches of coral in other parts of Western Australia have already been spotted bleaching--spitting out the symbiotic algae that keeps them alive--when struck by surges of warm water.
Powell, Devin. "Warmer waters aid some corals: Western Australian reefs faring better than eastern." Science News 10 Mar. 2012: 15. General Science Collection. Web. 24 Mar. 2012.
Gale Document Number: GALE|A283156727