EARLY results from a rare and historic long-term ocean acidification study in Marine Ecology Research Centre, Gaya Island, started in February 2023, found “a healthy and diverse macro invertebrate community… with no visible signs of shell thinning or reduced calcified biomass” but cautioned that these are only short term indications.
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Prof Dr Aileen Tan, a top award winning Malaysian marine biologist, Director of the Centre for Marine and Coastal Studies (Cemacs), Universiti Sains Malaysia, is waging a battle to help people grasp the triple threats from his ongoing menace ::
Oceans getting Hotter, Sour, Breathless
“The oceans are getting Hotter, Sour and Breathless !” she keeps explaining the complex phenomenon in simple words to widen public understanding and recognise this is a major threat to marine ecosystem and biodiversity held to have far reaching consequences on ocean health and all life that inhabit it.
Keen to discover how Ocean Acidification may have threatened Sabah waters too, in early February 2023, Prof Aileen Tan led Cemacs under her into a joint agreement with Marine Ecology Research Centre (MERC) to set up the first ever ocean acidification monitoring station in the South China Sea, at Gayana Marine Resort, enjoying close rapport with aquatic biologist Alvin Wong, MERC’s Project Director, and Gillian Tan, owner representative of Echo Resorts which owns Gayana Marine Resort.
CAUs (Calcification Accretion Units) deployed under natural underwater conditions at Merc, Gaya Island. They measure calcium accretion in especially coral reefs, assess impacts of environmental changes, like ocean acidification – a key subject of this study in Sabah.
By 28 Feb 2023, key standard research tools such as a sensor that continuously monitor sea water temperature and acidity, Autonomous Reef Monitoring Structures or stacked PVC plates for marine organisms to colonise designed to monitor biodiversity and thirdly, CAUs (Calsification Accretion Units) deployed to measure calcium carbonate accretion which helps to assess impacts of environmental changes, were fully installed and commissioned.
Tools such as Autonomous Reef Monitoring Structures (ARMS) and Calcification Accretion Units (CAUs) are increasingly important in this regard.
On 17 July 2025, ie two months and five months later, two sets of CAUs and two sets of ARMS each were successfully retrieved and brought back to Cemacs for preliminary analysis, according to Prof Aileen Tan.
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“Early ARMS data from Pulau Gaya, Sabah, indicate a healthy and diverse macro-invertebrate community, including sensitive calcifying taxa such as Chama, crinoids, and brittle stars.
No visible signs of shell thinning or reduced calcified biomass have been detected, suggesting that OA stress may not yet have reached ecologically significant thresholds in this area.
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However, ocean acidification is a cumulative stressor and may interact with warming seas and nutrient inputs to undermine coral and invertebrate resilience over time.
While visible reef health in Sabah may still appear stable, structural changes in coral skeletons and shell-forming species may already be underway.
A long-term coral core study in the northern South China Sea has shown a decline in Porites skeletal density and calcification rates over the past four decades, despite stable vertical growth – an early sign of OA’s silent but lasting impact (Yue et al., 2021).
This underscores the need for proactive monitoring.
Building an early warning system
By combining ARMS, CAUs, and environmental DNA (eDNA) analysis, researchers are building an early-warning system capable of detecting ecological shifts before they become visibly apparent, helping safeguard Sabah’s reefs against the advancing effects of ocean acidification.
From CAU plates:
There is clear evidence of calcifying organism settlement, including small corals, tube worms, bivalves & patches of coralline algae.
Some plates show relatively dense colonization, particularly by encrusting taxa, while others exhibit patchier @ more selective settlement patterns.
The presence of early coral recruits is a positive indication of larval availability & settlement potential in the area.
The overall diversity appears moderate, with both hard & soft encrustations visible,” Prof Aileen Tan concluded.
However, she reminded these are just “short term biological responses”.
“Ocean acidification (OA) is occurring in the South China Sea but a moderate and regionally variable rate.”
“In many cases, its effects remain subtle or masked by complex local environmental conditions, making it difficult to detect clear short term biological responses without long term fine-scale monitoring.”
Daily Express, 27 July 2025. Full article.
