Hurricane Helene churning past the Florida Keys last week brought colder water to the surface around coral reefs recovering from a 2023 mass mortality caused by an extreme marine heat wave, federal scientists said Monday.
Florida Keys National Marine Sanctuary scientists said water temperature “dropped significantly” as Helene approached the Keys, giving a reprieve to corals that are continuing to bleach but at slower rates than in 2023.
Monitoring data shows surface water temperatures in the Florida Keys dropped to about 84 degrees Fahrenheit around the most shallow reefs, down 7 degrees from mid-September when temperatures hovered around 91 degrees. A similar cooling occurred after Hurricane Debby in early August and lasted for about a week.
NOAA says reefs are best suited to live in ocean water between 73.4 and 84.2 F. Last summer saw 100-degree water settle in for weeks.
