Potentially Harmful Algal Bloom Recorded on Local Reefs

The St. Maarten Nature Foundation and members of the local diving community have been noticing an alarming amount of algae on the reefs within the Man of War Shoal Marine Protected Area. A sample of the algae was taken by the Nature Foundation and was analyzed in order to determine the species and further cause of the algae.  

The results indicated that the alga was the result of a Cyanobacterial Bloom. The bloom is a naturally occurring, thread-like, marine alga that occurs naturally in coastal waters growing attached to seagrass, corals and other shallow bottom areas. On occasions it can grow rapidly to form an algal bloom which has been experienced in the Marine Park over the last several weeks.

The Algae usually grows attached to seagrass, seaweed (macroalgae), coral and sediment in clumps or mats of fine, dark, cotton wool-like strands. Lyngbya is common in seagrass and coral reef habitats in tropical and subtropical waters worldwide. Dense blooms have occurred in various locations around the world and in coastal areas blooms have been recorded in both urban and more pristine areas.

These types of blooms can impact the environment and people’s health. While contact with is generally rare it can cause skin irritation and redness and can smother seagrass, coral and other benthic habitats. Keeping this in mind the Nature Foundation and Dive Operators will be on the reef continuously in order to clean the algae.

Over recent decades blooms have increased in tropical and subtropical regions around the world. The key environmental conditions for algal growth appear to be the presence of bio-available nutrients phosphorus, nitrogen and iron; dissolved organic matter; and favorable light, salinity and temperature conditions in the environment. Recent heavy rains and land run-off is likely the cause of the current bloom.

The Nature Foundation recommends that divers only collect the algae using gloves and to contact the Foundation to dispose of correctly.