08 July 2024

Mass coral bleaching at Pulau Semakau (East)

At a not-so-low-tide before dawn, we survey Pulau Semakau next to the Semakau Landfill and near petrochemical plants on Pulau Bukom.
Mass coral bleaching 2024 check at Pulau Semakau (East), 8 Jul 2024
Despite its location, this shore has living reefs with giant soft corals, giant sea anemones and we saw 2 Giant clams! Unfortunately, it is impacted by mass coral bleaching. We estimate 50% of hard corals  and 70% of leathery soft corals were bleaching. Kelvin also flew the drone and will have valuable insights into the situation.

As usual, the team makes all the special finds. Two large Fluted giant clams were seen; these can also bleach and it seems these were still okay. Other sightings include favourites like the usual clown anemonefish, and a special huge nudibranch. Richard saw a bleaching Magnificent anemone - I have never seen this anemone bleach before.
Collage of photos by the team.
Links to their albums below.
Most of the corals on this shore are boulder shaped. I saw some well formed colonies that looked alright, some pale ones and some partially bleaching. Most of those bleaching also had patches of recently dead tissues and others had patches that looked like tissues died some time ago.
Although the tide wasn't low enough for me to reach the reef edge, I did manage to see a variety of corals. I looked at corals that in the past bleached first: Cauliflower corals - one was okay, another was bleached and I saw a few that were recently dead. There were also Brain corals, Anemone corals, Lettuce corals, some okay but most were bleaching.
As in the past, the shore is dominated by large colonies of Leathery soft corals of various kinds. Today, much of them were highly stressed. Some colonies were 'melting' forming holes and breaking up into smaller segments. Some had an unusual 'corrugated' texture in the common tissue. Many were covered in a peeling layer, even those that were not bleaching. The peels often forming large 'balls'. I saw some that had just died - the dead tissue is bluish grey and smells bad.
Other cnidarians can also bleach, so I looked out for those too. Button zoanthids dominates most of the upper shore and I only saw a few tiny patches bleaching. Some Sea mat zoanthids were 'melting' or with white patches. There were many Asparagus flowery soft corals, about half were pale or bleaching. There were many Giant carpet anemones most were fine though a few were a little yellowish. Bubble-tip anemones are often the first to bleach making them easier to spot, one had a Tomato anemonefish! The large clumps of Magnificent anemones are still there, those I saw were fine, but Richard might have spotted one bleaching. I saw a Leathery sea fan, Frilly anemonescorallimorphs - they were fine, healthy ones are usually well camouflaged so I might have missed them.
Kelvin took great drone footage of the shore at variable heights. Showing the extent of mass coral bleaching, and coming low enough to see more details of bleaching and death.

During the previous global mass coral bleaching, we saw something similar on this shore in July 2016. At that time, we estimated 70% of the hard corals and 40% of the leathery soft corals are bleaching. We estimate 5-10% of the corals have died recently. Today, our estimate is 50% of hard corals and 70% of leathery soft corals are bleaching, with some signs of recent death. The tide today was not very low, so not as much of the shore is visible in the photo.
It seems, right now, according to the NOAA prediction for the Singapore Strait, the bleaching situation for Singapore is at "Watch". But expected to swing to "Alert 1" in next 1-4 weeks, then swing back to "Warning" thereafter. Let's hope for the best!
There seems to be a bloom of cyanobacteria - clumps of fine black hairy organisms, covering a large area near the seawall. We also noticed this on our survey of Pulau Semakau (South) in Oct 2023. I hardly saw any seagrass on the shore today.
Bloom of Cyanobacteria?

More about Pulau Semakau

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. 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.

What is the fate of Pulau Semakau (East)?

Pulau Semakau (East), Terumbu Semakau and even Pulau Jong and Pulau Sebarok are 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.
Mass coral bleaching 2024 check at Pulau Semakau (East), 8 Jul 2024
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 survey
Richard Kuah

Liz Lim

Shawne Goh

Kelvin Yong Drone footage

Kelvin Yong Part 1

Kelvin Yong Part 2

Tommy Tan


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