Plankton blooms in the Gulf of Thailand signal bad pollution, warn experts

This concern was raised at a seminar held on September 22 by Kasetsart University’s Innovation and Social Engagement Institute and Faculty of Fisheries.

At the seminar, lecturer Prof Dr Chettapong Meksamphan cited the recent plankton blooms at Chonburi’s Bang Saen beach as an example of the dangerous degradation of the sea environment.

The water at Bang Saen Beach turned green several times this year with plankton bloom killing scores of fish along the 3- to 4-kilometre-long beach, affecting tourism as nobody could swim in the foul-smelling sea.

Chettapong said plankton blooms usually happen after heavy rain, but can also take place due to wastewater.

He said plankton blooms often occur in the Gulf because wastewater from communities and factories, as well as agricultural runoffs, usually flows down the Chao Phraya River into the sea.

He explained that the wastewater and agricultural runoffs provide plenty of nutrition, and that combined with sunlight, creates just the right conditions for a plankton bloom.

He said such blooms kill a lot of fish because though plankton produces oxygen during the day, it consumes all the oxygen in the seawater at night and essentially suffocates the fish.

Speaking at the same seminar, Pinsak Suraswadi, director-general of the Pollution Control Department, put the blooms down to poor garbage management.

He said ineffective waste management results in the accumulation of organic substances on the earth surface, which is then washed into the sea during the rainy season, becoming nutrients for plankton.

He said waste substances from communities, factories, hotels and the farmlands washed into the sea cause Eutrophication, which subsequently results in a plankton bloom.

Eutrophication is the process by which a body of water becomes enriched with nutrients, particularly nitrogen and phosphorus. This can happen naturally over time, but is also accelerated by human activities such as agriculture, sewage treatment, and fertiliser runoffs.

Pinsak added that about 11 million cubic metres of wastewater from communities flows into the sea daily and 20% of it is untreated.

He said the government needs to step up enforcement of the Building Control Act to ensure all residential areas treat wastewater before releasing it to canals or rivers.

Sumana Kajonwattanakul, director of the Marine and Coastal Resources Research and Development Institute, told the seminar that the government must tighten the enforcement of the Marine and Coastal Resources Act to prevent more pollution of the sea.

Government agencies should also set up volunteer networks to monitor the quality of seawater to prevent serious pollution, she added.