Florida Keys coral takes lethal hit from cold

From an article on UnderwaterTimes.com:

SUMMERLAND KEY, Florida -- Sustained cold water temperatures in South Florida and the Florida Keys triggered severe coral bleaching and even coral death, alerting resource managers and prompting a coordinated assessment response from the science community. Temperatures in some nearshore areas of the Florida Keys National Marine Sanctuary dropped to 52 degrees Fahrenheit for several days - well below average for this time of year — with fatal results for some corals.

A cold-water bleaching and die-off hasn't occurred in Florida since the late 1970s.

"The Keys have not seen a cold-water bleaching event like this since the winter of 1977-78, when acres of staghorn coral perished," said Dr. Billy Causey, southeast regional director of NOAA's Office of National Marine Sanctuaries. "But today we are better prepared to document and assess the impacts of stress thanks to numerous partners." Causey has lived and worked in the Keys since 1971.

Over the next two weeks, teams of science divers from federal and state agencies and non-governmental and academic organizations will be surveying sites from the Dry Tortugas through Martin County to assess and monitor mortality and changes in coral health. The site locations and survey protocol were developed by The Nature Conservancy and other members of the Florida Reef Resilience Program for monitoring impacts to corals following a major disturbance, such as a mass-bleaching event.

Coral bleaching occurs when a coral animal undergoes stress and loses its symbiotic algae (called zoxanthellae). Prolonged stress can result in coral death. Coral bleaching is most frequently associated with elevated water temperatures, but stress also occurs when water temperatures dip below the preferred 60-degree threshold.

"If there is any ‘good news' it's that reef managers and scientists are able to quickly respond to this event and are in a good position to learn more about how reefs will rebound following such a rare occurrence," said Chris Bergh, director of The Nature Conservancy's Coastal and Marine Resilience Program.