A group of marine scientists at Thailand’s Department of Marine and Coastal Resources (DMCR) reviewed the results of ocean acidification monitoring in 160 sites across the Gulf of Thailand and Andaman Sea, during a workshop on Monitoring Ocean Acidification and Coral Reef Biodiversity in Thailand, organized by the Department and the Intergovernmental Oceanographic Commission Sub-Commission for the Western Pacific (WESTPAC), and held at the Phuket Marine Biological Center from November 25-27, 2020. The Department has been involved in IOC-WESTPAC’s Ocean Acidification programme since the programme began in 2015.

Ocean acidification encompasses those chemical reactions that occur when seawater absorbs carbon dioxide (CO₂ ), reducing seawater pH (i.e., increasing seawater acidity),  carbonate ion concentration, and saturation states of biologically important calcium carbonate minerals. This impacts on the ability of calcifying species – e.g. oysters, clams, sea urchins, corals, and calcareous plankton – to grow and build their skeletons and shells from calcium carbonate minerals.

Coming from all seven of the Department’s research centers and responsible for ocean acidification monitoring of Thailand’s waters, the workshop’s 16 participants presented data related to carbonate chemistry – pH, total alkalinity, dissolved inorganic carbon, CO₂  – from their monitoring sites. Averaged monitoring data from a short period of two to three years has shown declining pH levels in some of the sites.

Is this cause for worry for Thailand?

“Data on pH levels from 2017 to 2020 for some of the monitoring sites are in, but we need more data over a longer period of time before we could conclude anything definitively,” Somkiat Khokiattiwong, primary lecturer at the training and the principal investigator of the IOC-WESTPAC Ocean Acidification programme, said. “This monitoring of ocean acidification only began in 2017, and there’s a lot more work to be done to measure these parameters.”

To look into the impact of OA on reef ecosystems, another set of parameters is the status of biodiversity in coral reefs. Recently, the Department’s marine scientists retrieved the Autonomous Reef Monitoring Structure (ARMS) – a stack of 10 dark grey, opaque PVC plates where marine organisms had settled over the past three years – submerged five to ten meters in the western and eastern coasts of Kho Raya Yai – one of southern Thailand’s tourism-famous islands – in the Andaman Sea. The plates would clue them in on the diversity of marine species that were living on the ARMS unit, and by extension, the diversity of life on that particular coral reef. ARMS is used by marine scientists studying marine life so that they would not have to pluck up living coral reefs for studies. Retrieval of two other ARMS units deployed in the Gulf of Thailand is likely to happen next year.

Knowing the species composition and abundance, therefore, the level of biodiversity, of a coral reef, as well as the carbonate chemistry of seawater, is only the first step in the long process of understanding the impacts of increasing acidification of the ocean to marine life and ecosystems – a still poorly understood area the world over, including in the Western Pacific.

The workshop is conducted within the frame of IOC-WESTPAC’s Ocean Acidification programme, which aims to build national capacities of Member States for ocean acidification monitoring and reporting, including for the United Nations Sustainable Development Goal 14.3 (Minimize and address the impacts of ocean acidification, including through enhanced scientific cooperation at all levels), in order to support global efforts to address the impacts of ocean acidification.

“We need to conduct long-term monitoring, as well as to make sure that Thailand has a capable human resource pool to conduct this long-term observation. The country’s policy and future actions depend upon the results of this long-term monitoring work,” Khokiattiwong said.

Because of its effect on seawater’s carbonate system, ocean acidification is seen to have an adverse impact on the complex and productive food web, beginning in those calcifying organisms – reef building corals, oysters, clams, and calcareous plankton – and culminating in humans high up in the food chain. Currently happening at rates not seen for at least 50 million years, ocean acidification poses a great threat to ocean-based food security.

For more information, please contact Wenxi Zhu, Head, IOC Regional Office for the Western Pacific (WESTPAC) at w.zhu@unesco.org