Isolation from humans helps reefs prosper
The power of coral reefs to rebound from catastrophic “bleaching” events is shown in a new study from Little Cayman, offering hope for the future of fragile marine ecosystems across the planet.
Research by the Central Caribbean Marine Institute over a 14-year period shows the island’s reefs lost 40 percent of their corals in the aftermath of the 1998 El Niño event, which warmed ocean temperatures and wreaked havoc on corals worldwide. But the study shows that corals in Little Cayman defied expectations by completely bouncing back, repopulating the isolated reef system.
The study offers scientists clues about the conditions required for coral reefs to survive the expected impact of climate change. Combined with similar results on the remote Scott’s Reef in north Western Australia, the findings suggest corals have a much better chance to regenerate and survive in remote locations, far from human impact.
Carrie Manfrino, president of CCMI and co-author of the paper, said Little Cayman was naturally free from man-made “stresses” that affected other reef systems.
“There is not as much fishing going on, there’s not much pollution going into the water. The conditions are there for coral recruitment to take place,” she said.
A “bleaching event” most commonly occurs when the ocean temperatures rise, stressing the corals and turning them bright white. Corals can recover from this, but many do not.
Global climate change, including the warming of ocean temperatures, has led scientists to predict a greater frequency of such “thermal stress events.”
Ms Manfrino said the research provided a “glimmer of hope” that global warming did not have to be a death knell for coral reefs, showing that, given the right circumstances, they could recover.
“I think this is a really important story for the entire region,” she said. “Coral reefs can recover from global stressors if the conditions are right and those conditions are not determined by the global stressor, but by what is happening locally.”
Researchers surveyed nine sites around Little Cayman over the 14-year study, noting the abundance, size and diversity of coral coverage. They found that coral coverage dipped dramatically over several years following the El Niño event. But by 2011 they had recovered almost completely.
Ms Manfrino said, “Beginning in 2009, we’ve seen a remarkable recovery of all species on just about all reefs surrounding Little Cayman. We speculate that the corals that have rebounded may provide a new, more resilient stock of corals.”
She said the similarities between the Little Cayman study and the results found in Australia challenged long-held scientific assumptions that remoteness of coral reefs was actually a hindrance to recovery capability.
“It has been previously thought that remoteness makes reefs more vulnerable to global disturbances because they are isolated from sources of coral larvae and lack the connectivity required for regeneration,” Ms Manfrino said. “However, at these two distant coral reefs, being remote also means being isolated from local anthropogenic stress. The isolation from humans appears more important than the lack of connectivity.”