Sunday, August 17, 2008

Semakau Inter-Tidal Walk on 17 Aug 2008

Seventy Third Discovery Posting

Semakau Land-fill Island. An off shore island located south of 'mainland' Singapore where our incinerated rubbish and ones which cannot be incinerated (like: bricks, mostly construction waste) goes to.

But where exactly in Singapore is this island? Look at the map below and look out for the red circle to find it (picture below).
Picture above is from

Contrary to popular belief that Semakau Landfill would be another dirty and smelly landfill, the care put into the design and operational work at the landfill have ensured that the site is clean, free of smell and scenic. During construction, silt screens were installed to ensure that the corals were not affected during the reclamation works (from wikipedia).

Therefore, one can find corals and many other marine life at the inter-tidal area of Semakau. And this morning, together with a group of octopus-es (the group's name of the day) and E (co-guide for the morning), we 'swam' along the area to feed, ah-hem, I mean see the many marine life one can see there.

Anyway, our first 'discovery' of the morning was this dragon fish sea cucumber (picture below).
Discovery Note:
1. Sea cucumbers, like the sea star belong to a group of animals which have spiny skin, so when you feel them, it is most likely that you find that the touch is rough.
2. Also like sea stars, sea cucumbers use sea water to circulate their bodies. We (humans) use blood. Therefore, it is inadvisable to remove them from water for too long, as it might stress them.
3. And when sea cucumbers are stressed, they might either 'eject' sea water, white threads or even their internal organs.

The second 'discovery' of the day is a sunflower mushroom coral (picture below).
Discovery Note:
Most mushroom corals do not form colonies like most other corals and most mushroom coral is usually a single polyp.
Unlike most corals, most mushroom corals are attached to the reef only when they are small.
As larger individuals, they will detach themselves from the reef (if they had attached themselves to the reef) and live loose on the seafloor.

As the tide was the lowest level at the point of time when we just reach the inter-tidal area, we moved quickly towards the reef edge. And we saw the third 'discovery', a giant calm (picture below).
Discovery Note:
They are the largest living bivalve mollusc and also known as the bear's paw clam
They can weigh more than 227 kilograms and measure as much as 1.2 metres across, and have an average lifespan in the wild of 100 years or more.
An interesting symbiosis occurs between a unicellular green alga (Zooanthella ) and the clam. The algae live in the tissues of the clam's siphon and mantle; they are able to obtain the sunlight needed for photosynthesis because the clam lies with its valves opening upward and part of the thick, purple mantle extruding over the shell.
In addition, there are crystalloid vesicles on the mantle surface that let in sunlight, thus allowing the algae to live deep within the tissues. The clam uses the algae as a supplementary or perhaps even a major source of food.

Almost forgot to mention that along the way, octopus-es had a few close encounters with ourselves, the octopus. =P

All right, fourth 'discovery' is a great find by our hunter seekers, a cushion star (picture below)
Discovery Note:
1. This is more commonly seen at deeper waters at the sea bed, say around 10+ meters.
2. So the chance of one seeing a cushion star during diving is high compared to a inter-tidal walk.

Our hunter seekers, H and LK also managed to find us the star of the walk, the knobbly sea star, fifth 'discovery' (picture below)!
Discovery Note:
They get their name from the knobs they have.
Although most of them are mostly red or orange in colour, beige or brown coloured knobbly sea stars have been spotted before also.
Can you believe that a knobbly seastar might be larger than your face? It’s about 30cm across! (look at the pictures below to get an idea)

Traditional Group photos with the star (pictures below)!And nearby, I managed to spot another knobbly (picture below)!It was also quite a slug day. I don't mean a bad day but rather a day where we saw a number of different sea slugs.

Nudibranchs are the sixth 'discovery'!

Discodoris boholiensis (picture below)

Jorunna funebris (picture below)

A Chromodoris nudibranch (picture below). Discovery Note:
'Nudibranch' means 'naked gills'. The name comes from the flower-like gills found on the back of many nudibranchs. These nudibranchs use the gills to breathe.
Nudibranchs are related to snails. Little baby nudibranchs are born with shells, but they lose them when they become adults.
It doesn't mean that they are without defense. To protect themselves, some produce distasteful substances, toxins and even acids. They advertise this with bright warning colours. Others are camouflaged to match their surroundings.
4. By being small and flat, they can also easily hide in narrow places.
5. Most nudibranchs are carnivores, they eat immobile or small, slow-moving prey. Examples are sponges, ascidians, hard/soft corals, sea anemones, etc.
6. Read more about nudibranchs on the online Chek Jawa Guidebook by clicking here.

We saw many other things, like a juvenile coastal horseshoe crab and flatworms, it's just that I didn't grab photos or good photos of them, or you could say I'm just lazy to blog about them... haha.

Anyway, thanks to all Octopus-es, you were a great group! =)

a) Check out Manta's experience for the things his group saw on this trip.
b) Check out my co-guide of the day (E's blog) for more photos too.

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