Irritating bacteria found in Kona tidal areas

  • A rash caused by Lyngbya. (Courtesy photo/Richard Bennett)

  • Lyngbya majuscula, which resembles a moss, is actually a skin- and eye-irritating cyanobacteria that forms long filaments. (Courtesy photo/Richard Bennett)

The “Red Sea Moss” Lyngbya came to the Kona Coast this month, and it is best avoided.

It was the first noted in Keauhou Bay by Na Maka o Ke Kai Waterkeepers Dennis Mihalka. This so-called moss or algae is neither. It is cyanobacteria, Lyngbya majuscula. The bacterial cells string together to make long filaments. The filaments give rise to the appearance of an algae. This bacteria is found in the tropical Pacific waters from time to time. It is unique as it can fix nitrogen from the atmosphere and needs a phosphorus source to thrive, unlike typical marine algae or phytoplankton.


Blooms of lyngbya occur on the Kona Coast. A lyngbya bloom in the late summer of 2015 occurred at Kohanaiki. Some children playing in the shallows developed a skin rash. Some parents were concerned when children developed skin lesions under the waistband of the swimming suits. Before entering the swallow waters, scan the rocks for a brown-red fine grass like growth and avoid it. When the filaments break off and lodge under swimwear, modest toxins from the lyngbya can cause pronounced skin irritations.

Treatments include washing the skin well and adding soothing ointments like calamine and cortisone creams. If lyngbya exposure is to the eyes, rinse well with drinking water, and seek medical assistance. Wash and dry the swimsuits to avoid re-exposure. The best treatment is prevention. Learn to recognize lyngbya and avoid the tidal area where the red seagrass is present.


Seasonal episodic blooms of Lyngbya are known in Hawaii and elsewhere. The bacteria respond to warmer water temperature and the presence of nutrients, especially phosphates. Phosphates are known to contaminate groundwater that flows into the sea. Control over excessive phosphate in groundwater and the sea will come as sewage leaks and cesspool usage are resolved.

This is yet another sign of untoward human influence of the near coastal waters. Help support the mission of the Kona Coast Waterkeepers at