Frances and Jeanne remove much of the algae from South Florida reefs.

If there is a silver lining to back-to-back hurricanes, it may that the angry seas scrubbed the carpet of harmful algae and cyanobacteria (blue-green algae) plaguing South Florida coral reefs.

Marine scientists at Harbor Branch Oceanographic Institution have documented the cleansing during their study of 84 coral reef sites between North Miami and Fort Pierce, but warn that the reduction in algae may be temporary. A seaweed-like plant called Caulerpa brachypus, discovered three years ago off Palm Beach County, is especially troubling because it can smother reefs and life forms that reef fish eat. Divers have reported that much of the reef tract resembled a “golf course.”