Between the Tides – Semakau Intertidal Walk

September 27, 2009 at 11:00 am | Posted in itchy backside | Leave a comment
Tags: Animals, Education, Environment, Nature, Uniquely Singapore

Itchyfingers had been waiting so long for this chance. Although I was invited by friend from RMBR for their trip to Pulau Semakau before, I never really have a chance to join them, mostly due to bad timing. So when Itchyfingers knew of the public walk to Semakau in September, we quickly signed up with some friends from our volunteering group. Access to the island is restricted and the public can only visit by joining activities conducted by designated interested groups and organisation. The intertidal walk conducted by RMBR is such a popular activity that openings are often taken up very quickly once they released the date. So we had to quickly grab our seats (in June!) before they were gone, therefore it was a long three month wait. 😮

But the wait proved to be worthy. The day started very cloudy. Then it poured heavily and continued to drizzle after lunch. I was so worried that the trip might have to be cancelled due to bad weather, or if we were to go ahead, would we be able to see much interesting stuff or be able to take any photos on a wet day. When we finally reached Marina South Pier, there was still a light drizzle…Worries continued… 😮

Itchyfingers were surprised to see our friends from RMBR there as nowadays they are less involved in guiding. More surprise followed as the guide for our group turned out to be another friend! 😀

The boat to Semakau took about an hour or so. It was still drizzling but the cool weather and good company made my worry go away soon. Instead, we spent the time chit chatting and taking photos at the deck.

Pulau Jong 炯岛 as seen from our boat. My RMBR friend said it has the
shape of a bun…Ooo…maybe during their many boat trips they must had been
quite hungry to associate the island with a bun… hahah…so this was called
the 包岛 (Bun Island) by me…hahah…Apparently this little bun size island
had some interesting marine lives too as seen from this site

Once we reached Pulau Semakau, we were ferried in mini vans for the Semakau Landfill tour, before heading for a short slide presentation. Certainly informative especially for first timers but it would be a bit dry for repeat visitors I guess. But I found out later that, not only was the tour and presentation important to educate the public about the importance of reducing wastes and encourage recycling, it was also to buy time for the other guides to recce the shore for interesting marine lives before the start of our intertidal walk in the late afternoon. By now the sky had miraculously cleared and the temperature was cool, perfect for an excursion!

We were warned of the many mozzies ambushing in the forest waiting for their next warm meal before trekking through the muddy forest ground. True enough, there were so many mozzies that all of us had to hasten our pace, absolutely no mood for any pictures!

Starting of the short forest trek…I didn’t apply the repellent made of natural
ingredients offered by our guide as I hate the oily feeling on my palms. Didn’t
want to use my own repellent to spray on the legs as we would be treading in
the water and the chemicals might not be very safe for the marine lives

It proved to be a wrong decision, cos the mozzies there were seriously out for a feast! Even when we were out of the forest, they were still chasing after us and it was disgusting to have at least 8 or 10 blood suckers on the same calf or arm at the same time! Eeeek!

The forest was darker and more humid with mozzies chasing us, and imagine
reaching the end of the forest patch and saw this open land! The feeling was like
reaching paradise…hahah… 😀 The mozzies followed us until we were further
out in the open…

You would think this tree was the only one surviving on the shore but look
under your feet and you would realise lives were everywhere!

The mangrove tree, Bakau Pasir (Rhizophora stylosa) that Tisu Boy said
looked like the Nature Society’s logo, or the Sungei Buloh’s logo… 😀 Bakau
are used as firewood and also made to charcoal…

Oysters! Hee…I dun eat shelled fish, so wasn’t drooling… 😀

The bright orange flags were laid by the guides who went scouting for
interesting animals earlier on. They called them the ‘hunter seekers’ :p
So we were led from one discovery station to another

Can see Pulau Bukom from here

During the van ride, we were briefed on the dos and don’ts when doing our intertidal walk. To minimise damage to the environment, we had to follow the guide’s trail closely. We shouldn’t be touching the animals as many might give a nasty sting. Obviously, touching would cause stress to the animals so do not be an itchy finger unless the guide says its okay to do so!

My first encounter with a life Horseshoe Crab! All these while I’d been seeing
only the dead ones in the wild…The Mangrove Horseshoe Crab
(Carcinoscorpius rotundicauda) is the smaller species found in Singapore
and the cross-section of the tail is round. They are related to spiders and
scorpions. They swim upside down and their tails are used as a rudder when
moving underwater and as a level to right themselves if they were overturned

This tiny Hairy Crab (Pilumnu vespertilio) is supposed to have silky
hair covering the body, but when I put it on my palm, it felt very prickly…
hahah…maybe due to the sediment trapped between…hahah..

At the various discovery stations, animals were placed in container so
we didn’t have to touch them, which might stress them. Swimming
Anemones (Boloceroides mcmurrichi) are fragile and the sticky tentacles
will tear off in the hands, so do not pick them up!

The Fan Worm lives in a long tube made of sand and mucus. These feathery
stalks located at one end of the worm are the modified tentacles. The rest of
the worm remains in the tube. There are eyespots on the tentacles which can
detect light intensity changes and movement, and the Fan Worm will retreat
immediately into the safety of the tube

Earlier I was wondering why the other group’s guide had a pair of wooden
chopsticks in his hand. Then we saw our guide also took out a pair of metal
chopsticks, which they used to point or pick out small animals in case they
are venomous. Here, our guide used the chopstick to gently touch the Fan
Worm and immediately it disappeared into the tube

Tape Seagrass (Enhalus acoroides) meadow. These are the longest
seagrass found on our shore, at 30 – 150 cm long and is one of the main
food of Dugongs. We had to be careful not to trample the meadow and sticked
with the trail already cleared by earlier groups to reduce the impact. I guess
that’s always the pros and cons with organising trips to nature areas. While
educating the public is important for the conservation of these wild lives, a
balance has to be struck so as not to compromise the survival of these
fragile lives

These floating whitish bits that resembled styrofoam are actually the
male flowers of the Tape Seagrass

The Round Sea grapes (Caulerpa lentillifera) are not seagrass. They are
seaweeds, which are large algae. Like plants, algae have chlorophyll and
carry out photosynthesis. To find out more difference between seagrass
and seaweed, see this site

The Noble Volute (Cymbiola nobilis) is a large shell that can grow up to
20cm and is threatened by over-collection as food and for its beautiful shells.
These predatory snails hunt and feed underneath the sand. The tube on the right
is called the siphon, and the animal uses it to seek out buried bivalves (like
clams). The black fleshy part with bright orange spots underneath the shell
is actually its large foot! After finding the bivalves, it wraps it with its large foot
and then waits patiently until its exhausted prey opens its shell to breathe.
The Noble Volute then seizes the opportunity to stick its proboscis to feed!

Spider Conch (Lambis lambis) got tis name from the six spider-like spines
on the flared lip. Can you see the pair of large eyes on stalks peeping out? 8)
No wonder I found this familiar, as it was on the cover of RMBR’s earlier
publication, Private Lives: An Exposé of Singapore’s Shore

A Marine Spider (Desis martensi) with body about 1cm. Normally I wouldn’t
want to touch a spider, but I got it transferred to the back of my hand and
its furry legs didn’t feel that itchy…hahah… 😀

Sponges are actually simple animals with no mouth, guts or other organs!

Sponges come in various shapes and colours!

Sponges have lots of little holes and a few large ones. They are filter feeders
(or suspension feeders) that collect bacteria, plankton and organic particles
from the water

Each hard coral is a colony of tiny animal called polyps that produce a
hard skeleton from calcium carbonate

One of the highlights of our walk was seeing the many beautiful starfishes. Though often referred as starfishes, they are actually not fish, so a better name should be sea star. :p There was a patch of shore with many sea stars, some of them buried in the sand but they often leave obvious star-shapes on the surface, so we were all very careful not to step onto them! Pity itchyfingers somehow din take photos of these nice patterns. I think our eyes must be full of stars! Hahaha….felt like singing, “Twinkle, Twinkle, Little stars..” 8)

Sea stars are echinoderms, that is, they are symmetrical along five axes,
have spiny skin and tube feet. Other examples of echinoderms are the Sand
Dollars and Sea Urchins. This is the Common Sea Star (Archaster typicus)

The underside of the Common Sea Star. The greenish stomach can be pushed
out from its mouth at the centre to ‘mop’ up detritus from the sand…When
our guide picked this guy up, he was in the middle of his meal but quickly
retracted its stomach…eeee…

A closeup of the tube feet that emerge from the grooves along the five arms.
Tube feet may be used to cling on surfaces, gather food, excrete waste and
breathe. Itchyfingers held one up and the sea star felt stiff…The spines help
the sea star to burrow into the sand

The arms may be stiff but they can become quite flexible. Instead of a hard
skeleton, the body is made up of a tissue that can change rapidly from rock
hard to almost liquid like. This allows the sea stars not only to bend its arm
to embrace its mate during mating as seen here with the smaller male on top,
but also enable them to deliberately drop off an arm if caught between the
jaws of predators. Sea stars can regenerate lost arms, but the process can
take as long as a year! During mating, their sexual organs do not meet
and fertilisation takes place externally where the eggs and sperms are
released simultaneously

We were lucky to see this six-armed Knobbly Sea Star (Protoreaster nodosus).
The other was an unidentified sea star

It has pink or purple tube feet. Unfortunately this one was so alarmed when
our guide ‘molested’ it that it kept almost all the tube feet in immediately…
amazing how the grooves closed so neatly almost like a zipper!

Underside of the unidentified sea star. Sea stars use sea water to support
its body and move its tube feet. Thus it is stressful for a sea star to be left
out of the water

The more common five-armed Knobbly Sea Stars. Notice the colours can
vary too

These sea stars do not look like the normal ones with long arms. They are
the juvenile Cushion Stars (Culcita novaeguineae). My friends said they
look like malay cakes! 😀

This elegant animal is a Marine Flatworm. But they way they mate is
quite vicious! As flatworms are hermaphrodites, that is, having both the male
and female reproductive organs, they engage in a sort of ‘penis fencing’,
where the needle-like organ is pierced anywhere in the body of the partner

See how they mate!

“The loser bears the burden of motherhood”…. 😮

We all said this trip we learnt a lot about biology….hahah.. 8)

Another interesting find by the hunter seekers – the Sandfish Cucumber
(Holothuria scabra). These are the edible ones found in Chinese restaurants…
eeeee…But they must be probably treated to remove the toxin. Some sites say it
looks like garlic bread…hahah…Why was the last one contorted like that…? :p

Cos the moment our guide picked it up and it started to squirt some liquid
as if peeing…! Hahah…Under stress, they will squirt water from both ends.
I took picture of that but thought it looked a bit obscene to show here…hahahah…
It was interesting cos when I first held on the sea cucumber, it was still
quite solid, but gradually turned flaccid while waiting for this picture
to be taken… 😀 Quite heavy though :p

Under extreme stress, some sea cucumbers are capable of expelling their innards. The stomach will eventually be regenerated but the sea cucumbers will not be able to feed until the regrowth. Like sea stars, sea cucumbers are echinoderms and they feed with their tube feets. Similarly, instead of a hard skeleton, the bodies are mostly made of tissue capable of changing from hard to soft, thus aiding movement etc. According to the WildSingapore site, “a unique feature of some sea cucumbers is an internal breathing system of branching tubes along the length of their bodies. Called respiratory trees, most large sea cucumbers have a pair of these, each connected to the opening on the backside. To breathe, the sea cucumber pumps water in through its backside and up through the respiratory trees. The water is then flushed out through the backside again. With this constant flow of water, some tiny creatures find the backside of a sea cumber a cosy and safe place to be! Small or thin-walled sea cucumbers, however, simply breathe through their skins.”

I am glad I do not eat sea cucumbers cos always think they look quite gross…hahaha… 😀

Another sea cucumber, the Ocellated Sea Cucumber(Stichopus ocellatus).
We were not allowed to handle this one cos it is said that under too much stress,
it may become limp and disintegrate. The many white “eyespots” on its back were
believed to possess some sensory functions to help the animal move around
or hold to the substrate. By now the tide was starting to come in…

With the sun setting soon and the tide coming, it was also towards the end
of the walk. Time to head back. Everyone was treading slowly to avoid stepping
onto animals

This cute little cuttlefish topped my list of favourite animals of the trip! At
barely 4cm, it already has the ability to change colour! Sweet!

Last animal of the day. The Onch Slug breathes air with simple lungs
and has thickened skin to prevent themselves from desiccation when the tide
goes down. They leave a trail of faecal material whenever they go! Eeee…. :p

Time flew and the sun was setting fast

And then near the forest entrance, I managed to see this dead jellyfish 😦

It was a great trip with good guide and good company. There are so much more we have yet to learn about the many amazing creatures on our own shores! Itchyfingers certainly hope to be back again!

Also see related posts:
> The Raffles Museum of Biodiversity Research
> Private Lives: An Exposé of Singapore’s Mangroves