Cold water coral bleaching in the Florida Keys

According to a report from the Nature Conservancy, the coral reefs are suffering this winter in the Florida Keys following a cold snap:

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.

On Coral List, Lew Gramer from the NOAA Atlantic Oceanographic and Meteorological Laboratory suggests that the cold snap might have lasting impacts:

Recent reports have surfaced among scientists, resource managers, and the media of large-scale, multi-species fish kills that have been primarily limited to shallow-water environments in Florida and Biscayne Bay.

Coral mortality has been reported from south Florida when water temperatures previously declined to 14 degrees Celsius, or below. While temperatures on offshore reef environments have been > 17-18 deg C (likely due to oceanic influence from the Florida Current), shallow-water and nearshore environments have fallen well below 14 deg C (e.g., 10-11 deg C near Long Key). It is expected that there will be some cold-water bleaching and potential for mortality in shallow-water corals and other reef organisms.

Tom Opishinski from Interactive Oceanographics posted a followup:

Our station at the Smithsonian Marine Lab in Ft. Pierce recorded a low of ~9.25 deg C in the IRL on 1/11.  A bit away from the corals but the record nicely shows the cooling trend corresponding to a 10 deg C drop occurring over a 2 week period.  Data can be accessed/viewed at – the plot will default to show water temperature then select “2 weeks” for the time period.

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