TACLOBAN CITY – Residents of the island municipality of Maripipi in Biliran may have been used to seeing the seawater turn reddish during occurrences of red tide, but not when it is green and sparkling.

The residents noticed the green particles on the coastal waters and shorelines of Maripipi on March 4, and municipal officials immediately asked the Philippine Coast Guard Sub-Station on the island to collect samples for laboratory testing at the Bureau of Fisheries and Aquatic Resources (BFAR) regional office.

Tests show the coloration was caused by a bloom of a dinoflagellate called Noctiluca scintillans, commonly called “sea sparkle” because it produces light when disturbed by waves or any movement in the water.

The local government unit, through its information office, immediately issued a public advisory warning residents that it “may pose risks to public health and marine life.”

The LGU discouraged swimming in affected areas and temporarily disallowed fishing activities. It also advised those who eat fish to wash them thoroughly with running water and remove the intestines, and told residents to refrain from eating shellfish for the meantime.

Professor Leni Yap, a marine scientist at the University of the Philippines Tacloban, however, said the bloom of dinoflagellate Noctiluca scintillans is a natural phenomenon and that the algae do not produce toxins.

Yap said that while it can be harmless when ingested, its bloom can cause oxygen depletion in the water, which may lead to the death of marine life.

Meanwhile, BFAR-8 issued a statement clarifying that it “is not harmful or fatal to humans, as it does not contain toxins that are dangerous to people,” but its rapid increase in number is harmful to other marine organisms such as shellfish and fish.

“When a bloom occurs and later dies off, it can lead to a decrease in dissolved oxygen in the water because it competes with other marine organisms for oxygen. This may result in fish mortality, especially for fish in fish cages and shellfish that cannot move away from waters affected by the bloom,” BFAR 8 stated.

BFAR said the bloom of the algae could be due to an increase in nutrient levels in the water, along with the effects of weather conditions.