North Florida Ecological Services Office
Southeast Region

Threatened and Endangered Species: Blue-green Algea Blooms

Federal biologists say no direct health effects on manatees have been confirmed related to the blue-green algae bloom occurring in and around the St. Lucie River and estuary in Martin County

Blue agreen algae bloom along Duval County, FL beach front.

Blue green algae along Florida beach in Duval County..
Photo Courtesy: Florida Department of Health - Duval

According to U.S. Fish and Wildlife Service biologists, blue-green algae (cyanobacteria) blooms, while unsightly, are not known to directly affect manatees.

  • As herbivores, manatees eat plants and incidentally ingest algae and other materials while feeding. Freshwater blue-green algae (commonly seen to form a green scum on the surface of the water) could be ingested. So far, it is not known to cause health problems in manatees nor is it known to affect their ability to breed.
  • Blue-green algae blooms can, if present for extended periods of time, shade out aquatic grassbeds where manatees feed and can cause grassbeds to die. The temporary loss of these feeding sites will cause manatees to feed elsewhere until the grassbeds return. Manatees routinely feed at multiple sites, including sites many miles apart.

Government agencies are monitoring algal blooms and manatees in the vicinity of the blooms. The Service is coordinating closely with Florida Fish and Wildlife Commission biologists and researchers. Because manatees are not known to be affected by the blooms, there are no plans to relocate them to other areas.

Florida Department of Environmental Protection Algal Bloom Information Leaving site icon

Florida Department of Health - Duval Blue Green Algae Safety Tips Leaving site icon

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Last updated: February 7, 2018