Coral disease outbreaks have struck the healthiest sections of Australia’s Great Barrier Reef, where for the first time researchers have conclusively linked disease severity and ocean temperature. Close living quarters among coral may make it easy for infection to spread, researchers have found.

“With this study, speculation about the impacts of global warming on the spread of infectious diseases among susceptible marine species has been brought to an end,” said Don Rice, director of the National Science Foundation (NSF) Chemical Oceanography Program, which funded the research through the joint NSF-National Institutes of Health Ecology of Infectious Diseases Program.

For 6 years, the international research team, led by University of North Carolina (UNC)-Chapel Hill, tracked an infection called white syndrome in 48 reefs along more than 900 miles (1,500 kilometers) of Australia’s coastline.

The colorful coral colonies that attract visitors to the Great Barrier Reef live atop a limestone scaffolding built from the calcium carbonate secretions of each tiny coral, or polyp. While polyps provide the framework, coral’s vivid hues come from symbiotic single-celled algae that live in the polyps. The algae supply much of the food coral need to survive.

When disease or stressful environmental conditions strike a coral colony, the polyps expel their algae. This algae loss makes the coral appear pale.

“We’re left with a big question. Can corals and other marine species successfully adapt or evolve, when faced with such change?” Rice said.

Understanding the causes of disease outbreaks will help ecologists protect reef-building corals, which support commercial marine species and buffer low-lying coastal areas.

“More diseases are infecting more coral species every year, leading to the global loss of reef-building corals and the decline of other important species dependent on reefs,” said lead study author John Bruno at UNC. “We’ve long suspected climate change is driving disease outbreaks. Our results suggest that warmer temperatures are increasing the severity of disease in the ocean.”

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