Mass coral bleaching at St John's Island, almost no oil spill impact

Just minutes from the Central Business District, lies one of Singapore's last natural cliffs at St John's Island. The rocky shore and reef edge has corals and seagrasses. A small team visit early this morning to check up for oil spill impact and mass coral bleaching.

Good news: we didn't see any oil spill impact the natural shores, and very little impact in the swimming lagoon. But mass coral bleaching is ongoing here. We estimate about 10% of hard corals were outright bleaching white, with another 20% showing stress (pale). About 5% of soft corals were outright bleaching, and about 10% showing slight stress (pale or very yellow patches). The team saw snake, sharks, 'Nemo' and other fascinating marine life!

The shores were very much alive! We did not see any dead animals. We saw the usual animals we commonly see on our surveys, going about their usual business. Sharks were still busy hunting at the reef edge. Kelvin got a video clip of one.

We also saw a Yellow-lipped sea krait - who quickly went into hiding but Kelvin found it in a tiny crevice. Marcus spotted a 'Nemo' and the rest of the team saw the usual colourful and lively fishes we usually encounter here.

Collage of photos by the team.
Links to their albums at the end of this post.

There were also lots of the usual large snails found on reefs. Plus squishy animals like slugs, sea cucumbers and worms. As well as delicate animals like feather stars. They all seemed alright.

Collage of photos by the team.
Links to their albums at the end of this post.

Crabs of all kinds remain abundant. In the water, on the rocks, even on the sandy swimming lagoon impacted by the oil - fiddler crabs still there. Also still there: hermit crabs large and tiny, shrimps snapping or hanging out in sea anemones. And sea spiders too.

Collage of photos by the team.
Links to their albums at the end of this post.

We did not come across huge impact from the 400tonne Pasir Panjang oil spill on 14 Jun 2024. Although there are signs of booms and clean up operation in the northern most swimming lagoon, there was only the faintest smell and signs of oil on the low shore. With a few tiny swirls of oil, some scum. There was no oil seeping out of the sand in our footprints. This suggests oil was removed soon enough that large quantities did not seep into the sand.

On the natural rocky shore on the northern most tip of the island, we didn't smell or see any oil residues on the rocks or cliffs. There was also almost no litter washed up on the high shore.

I was particularly worried about the grandmother Nyireh laut tree and her daughters who grow on the western shore of St John's Island, which overlooks the Sisters and is part of the Sisters' Islands Marine Park. What a relief to see they are still doing well: no smell or stains of oil on their trunks, leaves still fresh and green. Though some lower leaves had brown tips - maybe dipping into oil floating at high tide? Among the huge boulders that they grow on, I did smell faint whiffs of oil, perhaps tiny bits of oil trapped deep in the crevices among them. There was a large pallet stuck near a daughter tree. The pallet had no oil, but large litter like this can batter the trunk. Nyireh laut is Critically Endangered in Singapore and we probably have only about 7 trees on our shores. There are another 3 of these trees on Sentosa Tg Rimau, which was also affected by the Pasir Panjang oil spill.

Unfortunately, our shores are currently also being impacted by mass coral bleaching. Most of the hard corals on this shore are boulder shaped. Some of the large colonies on the higher shore were bleaching white, while others were merely paler than normal. I sense about 10% were outright bleaching white, with another 20% showing stress (pale). 

I looked at corals that in the past bleached first: Cauliflower corals (I saw only one and it was bleached), Sandpaper corals (I saw a few, most were okay only one was bleached). Most of the Flowery disk corals were stressed (odd coloured), but other plate-forming corals were mostly okay. There was a small cluster of Anemone corals, all okay except for a tiny clump.

This shore has always had a wide variety of small to medium-sized colonies of leathery soft corals. Those I saw today were mostly alright, only about 5% were outright bleaching white, and about 10% showing slight stress (pale or very yellow patches). . There was colony of Leathery sea fan that was pale at the tips. On the way home, I noticed all the Flowery soft corals on the pontoon pillars were bleaching.

Other cnidarians can also bleach, so I looked out for those too. Many large colonies of Sea mat zoanthids were very pale, I only saw a few all brown ones. Most other zoanthids were okay. I saw many Giant carpet anemone and none were outright bleaching. I saw one Magnificent anemone and it seemed fine.

The situation today is not as bad as what we saw here in Jul 2016 during the last Global Mass Coral Bleaching event, when 80% of the hard corals and 50% of the leathery soft corals are bleaching. It seems Singapore is currently at peak bleaching threat (Alert 2). The NOAA prediction for the Singapore Strait suggest that the situation will ease in the weeks ahead. Down to Alert 1 and then furthern down to Warning. Let's hope for the best! 

Seagrasses here seem fine! Outside the seawall, I saw about 20 clumps of Tape seagrass with long leaves (30-50cm) as well as many patches of Spoon seagrass - as I have in the past. They all looked fresh and green and healthy. St John's Island is one of the few shores left that still has long Tape seagrass.

Inside the swimming lagoons, there are large patches of dense Spoon seagrass with small leaves. They looked fine. As usual, there were lots of Bazillion snails among them.

There were clumps of fresh seaweeds of all kinds too, growing on the rocks in the natural area.

There are still plenty of signs of life on the sandy shores. There were some Common sea stars, some burrowing Moon snails, a Gong gong snail, and other signs of burrowing crabs and worms. On the high shore, there were active burrows of Ghost crabs.

Although oil can have long-term effects, let's hope for the best. We will try to check the shore again soon. High res photos of all photos taken today on wildsingapore flickr.

St John's Island in the Singapore Blue Plan

The Singapore Blue Plan 2018 highlights the importance of St John's Island to our marine biodiversity. The cluster of Kusu, Lazarus and St. John's Islands has been recommended by the Singapore Blue Plan 2018 for elevated protection status.

The Blue Plan highlights that Lazarus, St. John’s, and Kusu Islands are established sites for coral nurseries as their shoreline offers ideal sheltered areas for growth of corals. Designating these islands as No-fishing Areas can bolster their rehabilitation. Protecting a larger cluster of islands means 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

Tommy Tan


Marcus Ng


Kelvin Yong
Part 1

Part 2



Richard Kuah


Che Cheng Neo