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Blue-Green Algal Blooms in Coastal Florida—1999, 2000, and 2002

A foul-smelling, brown-colored blue-green alga, Lyngbya majuscula, was reported in the Tampa Bay area in June 1999, May 2000, and April 2002.

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A brown-colored algal bloom in Tampa Bay was reported to the Florida Marine Research Institute (FMRI) in St. Petersburg on May 30, 1999. By the end of June, similar, but more isolated and less extensive, blooms were reported in Charlotte Harbor, Cedar Key, and Sebastian Inlet. The following year, a similar bloom was reported on Florida’s west coast. It was first reported to FMRI on May 5, 2000, and by May 15, blooms were reported in Sarasota Bay, Tampa Bay, Terra Ceia Bay, Palma Sola, and at the mouth of the Manatee River. Two years later, on April 22, 2002, the Manatee County Ecosystem Management Program and the Florida Department of Environmental Protection reported a bloom in northwest Bradenton.

The cause of these blooms was Lyngbya majuscula, a species of blue-green algae that is found worldwide. Lyngbya majuscula blooms are common, annual events in many areas of Florida. Lyngbya majuscula can form large, floating mats. It is brownish in color and slimy to the touch, and it emits a foul odor. A variety of this species has been associated with contact dermatitis, known as "swimmer's itch," in Hawaii, Japan, and Australia, but there is no evidence that the blooms in Florida are capable of inducing skin irritation or other human health effects.

Scientists also do not believe there is a connection between Lyngbya majuscula blooms and acute, point-source nutrient inputs, such as sewage releases. As with any algal bloom, low dissolved oxygen levels may occur and could cause localized fish kills. To date, no adverse effects on seagrass, fish, or other marine organisms have been reported from Lyngbya majuscula blooms in Tampa Bay.

It is important to distinguish between the blue-green alga Lyngbya and a similarly named marine slime mold, Labyrinthula. Labyrinthula, which is not visible without a microscope, commonly occurs on seagrasses throughout Florida. Researchers are currently investigating the potential role of Labyrinthula in seagrass decline in Florida Bay and elsewhere. There is no evidence linking Lyngbya to seagrass loss.

Please contact aquatichealth@myfwc.com to report areas where the algae are blooming or for more information.

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Prior to July 1, 2004, the Fish and Wildlife Research Institute was known as the Florida Marine Research Institute. The institute name has not been changed in historical articles and articles that directly reference work done by the Florida Marine Research Institute.