07 April 2016

Guiding at Pulau Semakau with lots of sea stars!

Yesterday, I had a great time guiding at Pulau Semakau! This is the first time I'm guiding since I started the guiding programme on the island in 2005!
We had such a great time with enthusiastic and friendly visitors who spot all kinds of interesting marine life. We know we shouldn't take the sea stars out of the water, so we take our group photo with them this way!

We saw 10 of these large colourful Knobbly sea stars! They are indeed the highlight a trip to the shores of natural Pulau Semakau.
Chua Sek Chuan kicks off the walk with a safety briefing and introduction to the guides: Karen Chen, Ivan Kwan and Heng Pei Yan! Most of the team are also volunteer guides at the Sisters Islands Marine Park. While Ivan and Pei Yan and I also guide with the Naked Hermit Crabs, and we three are part of a small team of volunteers who regularly survey Singapore shores: 100 days a year covering 40 seashore locations, for about a decade.
The visitors in my group are very keen-eyed. Among the first sightings was this pair of snapping shrimps! We also learned to spot the many Hairy crabs that wander the shore like little teddybears.
Today, there were many many Common sea stars in 'mating' position. Sea stars of the genus Archaster have a unique mating behaviour. The male, which is usually smaller, seeks out a female during the breeding season. He then moves on top of her, his arms alternating with hers. Their reproductive organs do not actually meet. Sperm is merely released by the male when the female releases her eggs, for external fertilisation. This behaviour is believed to increase the chances of external fertilisation. So much so that the males do not need to be large and are thus usually smaller than the females.
We also saw this skeleton of a Heart urchin which is related to sea stars -- you can see the 'star' on its skeleton! Heart urchins usually live burrowed into the sand, so we seldom see a living one above ground.
We saw one Garlic bread sea cucumber and several Durian sea cucumbers.
We also came across this yellow ribbon of eggs, probably laid by a nudibranch or snail.
This large odd-looking creature is a Cauliflower nudibranch! I don't come across it very often.
Another special sighting by the visitors, egg capsules of some kind of squid, laid among the green sponge-seaweed.
Sek Chuan has spotted an Upside down jellyfish! The jellyfish harbours microscopic, single-celled algae (called zooxanthellae) inside its body. The algae undergo photosynthesis to produce food from sunlight. The food produced is shared with the jellyfish, which in return provides the algae with shelter and minerals. It is the algae which gives the jellyfish its colours. This is why the animal prefers to be 'upside down', with its bell facing the sea floor and oral arms facing upwards toward the light. When one is turned the 'right' way up, it will slowly turn itself upside down again.
We saw one Giant carpet anemone. But no shrimps or clown anemonefish.
We manage to walk to the reef edge before the tide turns! Here, the corals are much bigger!
It has been very hot lately, which makes us worry about coral bleaching. So I always check for this during our trips. What is coral bleaching and why this is of concern on the Bleach Watch Singapore blog. I saw a few hard corals that were pale or yellow. These included very yellow or whitish Disk corals, a pale Pebble coral and some pale Small Goniopora corals.
There were many Anemone corals and all of them seemed alright.
These hard corals were the first to bleach in the past. Those I saw on the trip seemed alright, although some were rather pale. Many of the Cauliflower corals I saw were pale at the tips. All the Sandpaper corals I saw were mostly still dark brown. The Torch anchor corals were a little pale. The Brain corals I saw were alright.
I saw a few Asparagus flowery soft corals that were oddly coloured, but most of the Leathery soft corals I saw were alright.
Sea anemones are also affected by bleaching. Sadly, we saw one Haddon's carpet anemone that was bleaching. It did not have shrimps in it.
The visitors are very mindful of impact and we all walk in single file to minimise our footprint.
It's a very sunny day, but quite breezy so it wasn't too hot. We walk past the mangrove tree that has died.
In the past, we used this tree as a marker for the exit during surveys such as for TeamSeagrass monitoring.
TeamSeagrass monitoring in 2010.
Oh dear! The seagrasses have almost disappeared!
There used to be so much seagrass here that we have designated one path for everyone to cross the seagrass lagoon, so that we do not damage the seagrasses there.

Photo at the crossing path by Loh Kok Sheng in 2010.
Kok Sheng was a regular guide at the Semakau walks.
But the corals are still where the seagrass used to be.
This shore of natural Pulau Semakau lies close to the petrochemical plants on Pulau Bukom.
Here's more about booking an intertidal walk at Pulau Semakau on the NEA website.

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. The eastern shore of Pulau Semakau is right next to the seawall of the Semakau Landfill, opposite the petrochemical plants on Pulau Bukom.
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.
As the existing half of the Landfill was used up, the Phase 2 of the Landfill was just recently 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.

On the drive from the NEA Jetty to the start point of the walk, we pass by Terumbu Semakau (a submerged reef) and the Eastern shore of Pulau Semakau. Although I no longer guide at Pulau Semakau, we regularly survey Pulau Semakau and the terumbus around it, by landing amphibiously in a dinghy.
It was a rather hazy day yesterday. The heat is hard not only on people but also our marine life. Let's hope they make it through!
Thanks to Subaraj Rajathurai for inviting us to guide at this walk! It was quite nostalgic to guide at Pulau Semakau so many years after starting the guiding system there in 2005 with the Raffles Museum now called the Lee Kong Chian Natural History Museum which still conducts these walks. I also remember it was Keith Hillier who got NEA to include me when it was decided to open the Landfill and Pulau Semakau for recreational activities. Keith sadly has passed away and I miss him so much.

Other work I've done at Semakau include organising the first survey of Semakau's mangroves led by Zeehan Jaafar and Loh Tse-Lynn. As well as setting up TeamSeagrass who monitor seagrasses at Semakau as well as Chek Jawa and Cyrene Reef. Also helping Marcus Ng who wrote the awesome books about Semakau's amazing marine life published by NEA.

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