Coral bleaching around Grand Cayman has become so dramatic that last week the police helicopter crew called the Department of Environment, concerned about what was going on in the water just off South Sound.
The world is in the midst of its third global bleaching event. Caused by warm waters from El Nino in the Pacific, corals are bleaching from Hawaii to Australia’s Great Barrier Reef and across the Caribbean. The U.S. National Oceanic and Atmospheric Administration predicts warm waters will impact 38 percent of the world’s corals this year.
The Cayman Islands Department of Environment is monitoring corals around the islands and watching water temperatures, hoping for stormy skies and cool water temperatures to take pressure off the reefs.
“It’s been a gradual event this year rather than a sudden thing like the 1998 event,” said Tim Austin, deputy director of the Department of Environment. With El Nino in the Pacific, Mr. Austin said, “We knew it was likely.”
Shallow corals that get a lot of sunlight are at the greatest risk, he said. “The west side is looking pretty rough,” he noted, and DOE teams have seen some bad spots off of East End.
Lois Hatcher, with Ocean Frontiers, said she saw the bleaching begin in August. But, she noted, “It’s really accelerated in the past couple of weeks.”
Ms. Hatcher, also one of the lead organizers for the Cayman Magic Reef Recovery group, said the coral recovered in the restoration project off George Town has been bleaching at about the same rate as other coral in the area.
Bleaching happens when the waters warm to over 87.5 degrees for extended periods and the algae that was living in the coral leaves. Corals depend on the algae for food; without it, the corals bleach and can die if their main food source is gone for too long. Corals can recover from bleaching, but even if they do, research shows that they are much more susceptible to other pressures, such as dredging or disease.
Scientists and environmental officials measure heat stress on corals in what are called “degree heating weeks.” For every degree above 87.5 degrees Fahrenheit for a week, that is one degree heating week, Mr. Austin explained. If the water temperature is 89.5 degrees for a week, 2 degrees above the threshold, that is two degree heating weeks. If the temperature is 88.5 degrees for three weeks, that is three degree heating weeks. The threshold is eight degree heating weeks before coral death becomes likely. Anywhere above four degree heating weeks makes bleaching likely.
According to NOAA data, the Cayman Islands are hovering right around eight degree heating weeks, but water temperatures are starting to come down.
“The coral bleaching and disease, brought on by climate change and coupled with events like the current El Nino, are the largest and most pervasive threats to coral reefs around the world,” Mark Eakin of NOAA said in a press statement last week.
Mr. Austin said bleaching issues are getting worse over time. “This will happen more and more every year,” he said.
“Corals in better health will recover better,” Mr. Austin said. He explained that reefs in protected areas and without overfishing are less likely to experience bleaching and recover better if they do.
NOAA reports that the global bleaching could reach into 2016, which could result in serious coral die-offs around the world.