Coral Reefs and Restoration in Singapore’s Turbid Waters

Sam Shu Qin is a marine biologist and lecturer at NUS College, where she teaches modules that bring students into close engagement with coastal communities in the region, exploring how people protect, manage, and live with marine environments. She is also the co-founder of Our Singapore Reefs (OSR), a community platform started in 2017, through which she organises dive clean-ups, public education, and outreach activities that bring people closer to Singapore’s marine life. Alongside this community work, Sam is also involved in coral restoration through her work with the NUS Tropical Marine Science Institute (TMSI).

OSR began from a direct encounter with the fragility of local reefs. During reef surveys, Sam saw how much trash had ended up in the sea and on coral reefs. Some of this waste may have been dumped directly, while other debris may have drifted with currents before settling on the reefs. In both cases, it places severe pressure on corals by covering, damaging, and sometimes crushing them. It was a striking reminder that damage to reefs often happens out of sight. Through dive clean-ups, public education, and community engagement, OSR works to make Singapore’s underwater environments more visible, and to encourage more people to care for them. During these efforts, Sam has seen mattresses and even complete barbecue sets discarded in the sea. She once also came across a washing machine that had crushed part of a coral reef, as shown in the clip below.

In Singapore, reefs are mostly found around the Southern Islands, with smaller coral communities also occurring off East Coast Park and Pasir Ris. Although many people think Singapore’s waters are too murky or polluted for corals to survive, Sam explains that this is not the case. Singapore has recorded more than 250 species of hard corals, even though its waters are highly turbid and sedimented.

This turbidity is closely linked to decades of coastal development, dredging, reclamation, and shipping activity, which have increased sedimentation and placed constant pressure on Singapore’s reefs. Other threats, such as oil spills from passing ships, marine debris, and climate change, add further stress and can make corals more vulnerable to bleaching.

From her professor, Prof Chou Loke Ming, and older members of Singapore’s diving and reef communities, Sam learned that underwater visibility used to be much clearer, reaching up to 15 metres in the past. Today, however, visibility is usually between two to five metres. In these conditions of Singapore’s murky waters, the corals that thrive are often those best adapted to low light and sediment. Of these, Sam points to Turbinaria, a plating coral that resembles cabbage and can capture more light with its wide plates; Platygyra, often called brain coral because of its maze-like patterns; and Porites, a massive coral with a smooth, boulder-like shape that helps prevent sediment from settling on its surface. Others have struggled, such as Acropora, a branching coral common in clearer waters elsewhere in the region, but one that does not do as well here. Then there is Stylophora, which is now critically endangered due to coastal urbanization, while Seriatopora hystrix has even become locally extinct.

Protection is therefore crucial. Sam points to Sisters’ Islands Marine Park, Singapore’s first, as an important milestone, and notes that another marine park around Lazarus-Kusu has been announced.

In Singapore, restoration projects are mainly led by NParks and NUS TMSI, with OSR supporting these efforts. Importantly, restoration methods have to respond to local conditions. For example, Acropora is usually not used in local restoration, because these branching corals need clearer water to thrive and are less common in Singapore’s sedimented waters, which are generally more suitable for plating and massive corals. Coral spider structures are also not always ideal because Singapore’s seabed is often sloping and unstable, and these structures largely support branching corals rather than the plating and massive corals that are more dominant here. Instead, coral nurseries act as an intermediate space where small fragments, including ‘’corals of opportunity’’ that have broken off naturally or by accident, are given time to heal and grow. Once they reach about palm size, they can be attached to stable rocks or restoration structures. These projects also use green fiberglass structures that resemble flowerpots, as well as heavy concrete blocks that help stabilize corals in Singapore’s wavy waters.

One of the most ambitious projects that Sam describes is the installation of eight 10-metre-tall high-relief reef structures at Sisters’ Islands, developed by NParks and JTC with input from scientists from NUS TMSI. Sam calls this one of the coolest projects they have worked on, because the structures are unlike ordinary coral blocks placed on the seabed. Each one is about the height of a three-storey terrace house and extends through much of the water column, creating different levels of habitat for corals, fish, and other marine life. Their concrete and fiberglass surfaces are made more complex with recycled rocks, giving coral larvae and other organisms places to settle. Together, the structures add around 500 square metres of reef area to the Marine Park, turning a mostly bare sandy seabed into a new habitat for reef life.