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Fire coral bleached by warm water

Vulnerable: Some fire coral in Bermuda's reefs has bleached due to warm ocean temperatures

Coral bleaching caused by record high water temperatures is being watched closely by the Department of Conservation Services.A spokeswoman for the Department said the whitened coral was not dead, and should regain its colour with the onset of cooler water.However, she added: “This assumes that warm water stress diminishes soon.“Studies in the Caribbean in the 1990s and early 2000s did record coral mortality when temperature stress exceeded two to three months.”The Island’s last significant episode of bleaching was in 2003.Bleaching has been most pronounced in brain coral and fire coral, especially in inshore waters, as the corals expel the microscopic algae that gives them their distinctive colours.Water temperatures rose to 30C (85F) last month — the highest since 2010 — and the spokeswoman said temperatures from July to mid-August were the highest since 2007.The warmth is the result of low wind speeds in recent weeks.“Most interesting was a very rapid drop in temperature in the first week of August and then another warming phase,” the spokeswoman added. “These rapid fluctuations are additional stress to corals and may have triggered the start of the bleaching.“In most years, the passage of hurricanes and tropical storms in August and September has caused mixing of the waters around Bermuda which brings up cooler deep water. This reduces the temperature stress on corals and prevents bleaching from occurring.”Corals should recover in September and October.The spokeswoman said reef scientists believe the bleaching is an adaptive response that allows the corals to acquire different strains of the algae, known as zooxanthellae, to cope better with environmental stress.