The h Department of Health is urging residents and visitors to avoid areas of Henderson Lake in St. Martin Parish where a blue-green algae bloom has been observed.
The bloom was confirmed through satellite imagery, according to the department. While some algae are harmless, certain types of cyanobacteria, commonly known as blue-green algae, can produce toxins harmful to people and animals. Testing is needed to determine whether toxins are present.
Because algae blooms can move and change quickly, health officials recommend avoiding areas where a bloom is visible or suspected. It is not possible to determine by sight whether a bloom is producing toxins.
“If you see or smell an algal bloom, stay out of the affected water and keep children and pets away,” LDH Secretary Bruce Greenstein said. “When you’re unsure, please avoid all contact with the water.”
Algae blooms are rapid growths of algae on the surface of the water. They may appear blue, bright green, brown or red and can produce a strong odor similar to rotting plants. Foam or scum may also form on the surface.
Cyanobacteria are a common cause of harmful algae blooms in freshwater lakes and rivers. Blue-green algae thrive in warm, calm and sunny conditions, particularly when water temperatures are above 75 degrees. Blooms are more common during the summer and fall but can occur at any time of year.
Residents who see or smell an algal bloom should avoid swimming, wading, boating or other recreational activities in affected areas and should keep pets away from the water.
People and pets that come into contact with affected water should be washed promptly with soap and clean water. Water from areas experiencing an algae bloom should not be used for drinking, cooking or preparing food.
Exposure to harmful algal toxins can cause rashes, stomach cramps, coughing, nausea, diarrhea and vomiting. High levels of exposure can affect the liver and nervous system, according to LDH.
Residents who develop symptoms after exposure should contact a health care provider. For health questions or concerns, LDH's Section of Environmental Epidemiology and Toxicology can be reached at 888-293-7020.