Sunday, July 18, 2010

Semakau Walk on 17 July 2010

It was pouring when we were on our way to Marina South Pier. The rain was so heavy, that the cab driver had to drive much slower than usual as visibility was really bad. And most unfortunately, when we turned into the Ayer Rajah Expressway, it was flooded, and we had to make a detour!

Fortunately, we still managed to reach the pier, and while it was still raining cats and dogs, we could see that it was less heavy. When we took the boat to Pulau Semakau, the rain had fortunately become a drizzle, and we managed to proceed with the guided walk.

I had a group of students from Raffles Girls' School, and our group name was "Hermit Crab". The students had to brave the rain walking for about half an hour to reach the entrance to the intertidal area. Some of the them decided not to use any rain gear as the rain was really light then.

However, it got heavier again when we were crossing the seagrass meadow, but that did not dampen our mood! :)

We saw quite a number of things despite the rain, but as the rain got heavy every now and then, I only managed to get a few decent photos.

Found this Moon Snail (Polinices mammilla) moving just beneath the surface of the sand. This snail is a fierce predator of smaller snails and clams. It has a huge foot with a wide mantle that it uses to wrap around its prey to suffocate them. If that doesn't work, it can also secrete an acid to soften the prey's shell, and use its radula (a tongue-like structure) to poke a hole through to feed on the meat inside.

Despite the rain, we saw lots of Sand-sifting Sea Stars (Archaster typicus). This sea star can burrow into the sand to escape from the rain or predators. It feeds on tiny decaying matter (called detritus) among the sand. To feed, it will push its stomach out of its mouth, which is in the middle of its underside. The stomach will "mopped" up its food and digestion will be done externally.

This Sandfish Sea Cucumber (Holothuria scabra) is another burrower. While this sea cucumber is edible, it must be properly processed to remove the toxins in it before it can be consumed. Interestingly, sea cucumbers breath through their anuses. Connected to the anus is a respiratory tree which is used for breathing.

We saw several octopuses (Octopus sp.) during this trip too! The octopus is one of the smartest invertebrates around, and is known to be able to get out of mazes and open jars to obtain food! This animal is made famous again recently due to the octopus, Paul, in Germany, which accurately predicted 8 World Cup games, including the finals!

This is a Funeral Nudibranch (Jorunna funebris). The name "nudibranch" refers to the flower-like gills on the back of most species. This little sea slug is poisonous, and it gets the poison from the sponges that it feeds on.

We also saw an Acanthazoon Flatworm (Acanthazoon sp.). This worm is so flat that it can easily slip into fine cracks among rocks to escape from predators or to seek for small animals to feed on.

Our hunter-seekers found us 2 Spider Conches (Lambis lambis). These huge snails are collected in some places for food. The top of the shell is usually covered with sediment which camouflages it, but turning it over will reveal the pretty colours on its underside.

Once again, we saw the resident juvenile Cushion Star (Culcita novaeguineae). It got its comon name from the fact that it's rather fat and looked like a little star-shaped cushion. This sea star feed on corals.

And talking about corals, we saw that there were still quite a number of bleached corals. Coral bleaching occurs when the algae living inside the corals leave their hosts or were expelled by the hosts. A healthy coral will usually be brownish in colour, as the algae living inside is a golden brown algae. The algae can photosynthesize and pass on some food to the coral in return for shelter and nutrients (waste matter from the corals). Bleached corals thus will lose a major source of nutrients, and may even die.

A little Noble Volute (Cymbiola nobilis) was also spotted. This snail feeds on smaller snails and clams.

Everyone was rather excited to see 3 Knobbly Sea Stars (Protoreaster nodosus). Semakau is one of the few places in Singapore where this huge sea star (can grow to about 35cm wide) can still be found in huge numbers.

And as usual, we had a group photo with the stars of the trip.

While the rain persisted throughout the trip, we were still very glad that it was not heavy (we actually did not have to use the rain gear sometimes), and most importantly, there was no lightning, or we would have to cancel the walk.

Certainly hope that the students enjoyed the trip :)

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