Summit County Citizens Voice

A drawing from an 1851 survey of Florida's coral reefs. Click on the image to see NOAA's online library of historical drawings.

Cold-water bleaching in the Keys the first since late 1970s

By Bob Berwyn

SUMMIT COUNTY — The planet may be heating up, but parts of Florida experienced the coldest December on record, chilling the waters around the Keys to the point that it killed coral reefs.

During the first two weeks of January, water temperatures dropped below 50 degrees, to some of the coldest readings ever recorded, leading to coral bleaching and deaths in the Florida National Marine Sanctuary. Coral reefs generally can’t survive at water temperatures below 60 degrees. The cold snap also killed manatees and untold numbers of fish.

The hardest-hit areas include the inshore and mid-channel reefs from Biscayne Bay in southeast Florida to Summerland Key, according to a press release from the National Oceanic and Atmospheric Administration. Click here to visit NOAA’s coral reef website.

Coral bleaching occurs when corals, stressed by changes in conditions such as temperature, light, or nutrients, expel the symbiotic algae living in their tissues. NOAA scientists and partners from 12 research organizations are surveyed 78 sites in the region to determine the severity of the damage.

The scientists said their early results show the bleaching was spotty, with some hard-hit reefs immediately adjacent to other areas that appear unscathed. It was the first cold-water bleaching event in Florida since the late 1970s.

Some offshore reefs frequented by divers and sportfishers were buffered by warmer waters of the Florida Current and spared severe impact.

Researchers are still exploring whether this cold-stress event will make corals more susceptible to disease. Following warm-water stress events, the bacterial makeup of corals changes, increasing the prevalence of coral disease. This winter’s event allows scientists to collect data to compare and contrast coral health following both cold- and warm-water events.

Florida Keys National Marine Sanctuary, the manager of most Florida Keys coral reef resources, is working with the science community and limiting certain consumptive activities in the hardest hit areas until stressful conditions subside. The Sanctuary is also asking SCUBA divers to enjoy the many reefs not affected by January’s cold weather.

Filed under: climate and weather, coral reefs, Environment, global warming, La Niña Tagged: | Biscayne Bay, climate, Coral bleaching, coral reefs, Environment, Florida, Florida Current, Florida Keys, Florida Keys National marine sanctuary, global warming, National Oceanic and Atmospheric Administration, Summerland Key, Summit County News