Friday, May 01, 2009

Semakau Walk on May Day

Today was different.

Instead of departing from the usual Marina South Pier, I departed from Pasir Panjang Ferry Terminal. Nope, the other guides were not with me - I was the only guide.

Today, I was involved with a guided walk for NEA and MediaCorp staff organised by NEA! :)

The weather was sunny with a little breeze - certainly much better than the thunder storm I experienced yesterday, and that was certainly a good start for the trip. And indeed our luck was good.

Dolphin
While we were on boat reaching Semakau, I saw a dolphin pod! Unfortunately, they turned swam towards Pulau Hantu and thus only a few of the visitors saw them. But they swam back again while during the introductory presentation by NEA, and stayed at the jetty area even after the presentation, and thus some of the other visitors managed to see them. I have put up a separate entry on the Dolphins at Semakau Jetty earlier.

Presentation
And here's the presentation which NEA officers gave an introduction on Semakau Landfill and waste management in Singapore to the visitors. After the presentation, the visitors were given a landfill tour, before proceeding to the intertidal area.

Secondary forest
The visitors had to walk through a secondary forest to reach the intertidal area.

Obstacles in the forest
There were a few obstacles along the way...

Happy faces
But everyone was still cheerful and enthusiastic! :)

Synaptid Sea Cucumber (Family Synaptidae)
We soon reach the intertidal area, and at the edge of the seagrass meadow, we saw a Synaptid Sea Cucumber (Family Synaptidae). This is probably the longest species of sea cucumbers in Singapore. The longest that I have seen is about 2m long! It feed on tiny organic particles by lashing its tentacles around to pick up the particles.

Group photo
As usual, we took a group photo while crossing the seagrass meadow.

Group photo
Here's a slightly wackier one.

Spider Conch (Lambis lambis)
Immediately after we crossed the seagrass meadow, we saw a very pretty Spider Conch (Lambis lambis). The above shows its underside. The long sickle-shaped structure at the shell's opening was its trapdoor, which it used like a pole vaulter to hop around.

Giant Carpet Anemone (Stichodactyla gigantea)
There were several Giant Carpet Anemone (Stichodactyla gigantea) in the seagrass meadow, and here's one of them. While it looked somewhat like a huge flower, it's actually an animal with lots of sticky tentacles, which it used to sting and capture motile animals to feed on. Its mouth is located in the middle.

Sand-sifting Sea Stars (Archaster typicus)
At the sandy shore beyond the seagrass meadow, there were lots of Sand-sifting Sea Stars (Archaster typicus), and many of them were in the pseudocopulation position. Why "pseudo"? That's because their reproductive organs do not meet. They would pair up with the male on top up to 2 months before they release the eggs and sperm into the surrounding water.

Noble Volutes (Cymbiola nobilis)
At the sandy shore, we also saw a few Noble Volutes (Cymbiola nobilis), including the juvenile above with a very pretty shell. These snails feed on other smaller snails or clams by wrapping their foot around the prey to suffocate it. When the prey opens its shell to breathe, the volute will feed on it.

Fluted Giant Clam (Tridacna squamosa)
Our hunter-seekers managed to find us the juvenile Fluted Giant Clam (Tridacna squamosa) at the coral rubble area - an area with lots of dead corals. While it was still quite small, it could eventually grow up to about 40cm wide. Living in giant clams are symbiotic algae which can photosynthesize, and the clams obtain a huge proportion of their required nutrient from the algae. The clam will obtain the remaining nutrient by filtering for plankton and tiny organic particles from the surrounding water.

Branching Coral (Montipora sp.)
As we headed further out, we began to see more and more corals. The Branching Coral (Montipora sp.) is commonly encountered in Singapore. It is a colony, and the one above may have hundreds to thousands of polyps (i.e. the coral animals) living in it. The hard structure is actually the polyps' skeleton, which they built with calcium carbonate! It's like our HDB flats, but the corals are such great builders that unlike us, they don't need any machinery to help them to build their "house"! Like the giant clam, they have symbiotic algae (called zooxanthellae) living in their body tissue too.

Knobbly Sea Stars (Protoreaster nodosus)
The highlight of any Semakau trip is always the charismatic Knobbly Sea Stars (Protoreaster nodosus). This one was still still a juvenile though, and is only about 15cm wide. The adults can reach to about 30cm wide. This sea star has a calcium carbonate armour and many knobs on its upperside to deter predators.

Upsidedown Jellyfish (Cassiopea sp.)
Right next to the sea star was a little Upsidedown Jellyfish (Cassiopea sp.) which appeared to be in season, as I saw quite a few of them today. This is another animal with symbiotic algae, and that's why most of the time it is found in the upside-down position lying on the seabed so that the algae can photosynthesize better. This one appeared to be rather active though. After I turned it over (as shown in the photo above), it decided to stay that way instead of flipping over.

Tigertail Seahorse (Hippocampus comes)
Our hunter-seekers managed to find us a male Tigertail Seahorse (Hippocampus comes) too! And why do I know that it's a male? From its big belly, which told me that it's pregnant! Yes, male seahorse carry the eggs and hatch them instead of the females. It has a pouch, which the female will lay the eggs inside.

Radula Scallop (Comptopallium radula)
If you have seen a Chinese opera and seen the clam fairy inside, you would be familiar with the way scallops such as this Radula Scallop (Comptopallium radula, previously thought to be Chlamys sp.) swim by flapping their valves. Semakau has many wild scallops too, and in the region, they are often collected for eating.

Sunflower Mushroom Coral (Heliofungia actiniformis)
Apart from the colonial corals like the earlier branching coral, we also have solitary corals like the Sunflower Mushroom Coral (Heliofungia actiniformis). This coral is free-living when they are mature, but when it is still a juvenile, it's attached to the substrate with a stalk, resembling a mushroom, and thus the common name.

Black Phyllid Nudibranch (Phyllidiella nigra)
Due to the hot weather, I had not expect to see many nudibranchs (a type of sea slug), but fortunately our hunter-seekers still managed to find us one. This is a Black Phyllid Nudibranch (Phyllidiella nigra), which is able to release toxic chemicals to the surrounding water when stressed - certainly an excellent way to deter predators!

Ocellated Sea Cucumber (Stichopus ocellatus)
Our hunter-seekers later found us a second sea cucumber - the Ocellated Sea Cucumber (Stichopus ocellatus). It has lots of 'eyespots' on its top side, which are believed to have some sensory functions or help the sea cucumber move around and hold to surrounding hard surfaces.

Fanworm (probably Sabellastarte indica)
Fanworms (probably Sabellastarte indica) were a common sight in many of the tidal pools. They lived in tubes which they made from sand and mucus. The feather-like tentacles grow on the worms' head, and they are used to filter for small food particles in the water.

Juvenile Cushion Star (Culcita novaeguineae)
As the tide was rising and we were heading back to the higher shore, LK shouted to me saying that she found another sea star. It was a juvenile Cushion Star (Culcita novaeguineae)! So far we have only seen the adult ones. Can't wait to see how this particular one would look like when it's bigger.

Noble Volute (Cymbiola nobilis)
On the way back, we also found another Noble Volute, and this one had just finished laying its eggs.

Moon Snail (Polinices mammatus)
We also saw a Moon Snail (Polinices mammatus), a hunter of smaller snails and clams. Like the Noble Volute, it will wrap its foot around its prey to try to suffocate it. But on top of that, it can also secrete an enzyme to soften the shell of its prey, and uses its radula (something like a tongue) to slowly scrape a hole through so that it can feed on the prey in the shell!

Back
Soon, time's up and we crossed the seagrass meadow to return to the main road to wash up and return to the jetty.

While it was a very hot day, it was still a surprisingly good day with many great finds! :)

2 comments:

maximus said...

Very cool, do you see many giant clams on these walks?

tHE tiDE cHAsER said...

We do not really see many of them actually. Just one or two.