Mussels taking over Pulau Semakau (South)?

We survey the seagrasses and shores at Pulau Semakau South on a lovely evening low tide. 

The corals seem alright. Although Tape seagrasses have not returned and vast stretches remain bare of seagrasses, there was good seagrass growths near the landfill wall. It was worrying to see Horse mussels continue to expand on the shore.

There have never been a lot of corals on this shore. The reef edge was covered with dense sargassum growths so I could only survey the mid shore. The corals I did see seemed mostly alright and I didn't see signs of mass coral bleaching. Most of the coral colonies were small and there were the usual common kinds. 

The narrow sand bar was full of life. I saw several Eggwhite moon snails, Weasel olive snails, Strawberry cockles, Common sea stars and one very large Orange sand star! James also saw Cake sand dollars. 

As we did on our last survey in Jan 2022, there were many Fire anemones, lots of Giant carpet anemones and Frilly anemones, as well as Upsidedown jellyfish. I also saw one Very Long sea anemone. The rest of the team also saw Haddon's carpet anemones, a few Swimming anemones. None were bleaching.

Jianlin Liu found a nudibranch that we seldom see.

Jianlin headed further up north and saw lots of large Knobbly sea stars. The rest of the team also saw octopuses and squids and cuttlefishes.

Horse mussel clams seem to have spread out and covering a larger area. In Jan 2020 and Mar 2019, I saw them in small groups of less than 10, spread apart. In Oct 2020, there were a lot more and closer together. Covering an area of about 20m2. The situation was similar in Jan 2022. Today, I sense they are denser and covering a larger area.

There were growths of Spoon seagrasses everywhere, with sprinkles of other seagrass species. I didn't see any long Tape seagrass. This is similar to what we saw in Jan 2022.

Alas, no dugong feeding trails seen, even with the drone that Kelvin flew.

Singapore's largest fish farm lies opposite these shores. We had a look at the large barge used by the fish farm near the shore. As we did in Jan 2020, there were stinking piles of netting there. Fortunately, we didn't come across any fish nets today on the shore.

Kelvin also flew the drone and got some great aerial views of this shore.


More about Pulau Semakau

It is NOT true that the construction of the Landfill created the marine life found on Pulau Semakau. The marine life was there long before the Landfill was built.

Just as Changi Airport and Changi Beach are not the same even though they are near one another and share a name, Pulau Semakau is NOT the same as the Semakau Landfill. The Landfill was created by destroying all of Pulau Saking, and about half of the original Pulau Semakau by building a very long seawall. Fortunately, the landfill was constructed and is managed in such a way that the original mangroves, seagrass meadows and reefs on Pulau Semakau were allowed to remain.

As the existing half of the Landfill was used up, the Phase 2 of the Landfill was launched. This involved closing the gap of the seawall on the Semakau Landfill, forming one big pool where incinerated ash will be dumped. NEA worked to limit the damage to natural shores during the construction work for this expansion of the landfill.

What is the fate of Pulau Semakau?

These shores slated for massive reclamation outlined recently in the Long-Term Plan Review.

The Singapore Blue Plan 2018

Pulau Semakau and nearby islands and submerged reefs have been recommended by the Singapore Blue Plan 2018 for Immediate Conservation Priority.

The Blue Plan recommends the intertidal and subtidal marine areas of Pulau Semakau and adjacent Pulau Hantu, and Pulau Jong to be designated Marine Reserve.

The Blue Plan highlights that Pulau Semakau and its associated patch reefs comprise many ecosystems: coral reefs, mangrove areas, intertidal sandflats, seagrass meadows, and coral reefs. The subtidal area of Pulau Jong is larger than the terrestrial area. Pulau Hantu is a popular dive site has seen increasing interest in the past decade due to biodiversity awareness. If protection is accorded to these three islands, zonation plans for use can be implemented to manage tourism and human impacts.

DOWNLOAD the Plan, SUPPORT the Plan! More on the Singapore Blue Plan 2018 site.

Photos by others on this trip

Jianlin Liu


James Koh


Kelvin Yong


Kelvin Yong's drone shots


Che Cheng Neo


Marcus Ng


Liz Lim