Jul 19, 2008

Sentosa with TeamSeagrass

5am and I'm out on Sentosa early to catch the outgoing tide before the TeamSeagrass monitoring starts at 6am. And the high shore is teeming with land hermit crabs (Coenobita cavipes). At first I thought the rustling among the leaves were rats! These large hermit crabs forage at night among leaf litter and other debris deposited by the tide on the high water mark. They are now rarely seen on the mainland, possibly because cleaners assiduously remove all trash from our public beaches. This marvellous animal is listed among our threatened animals.
Another creature active in the dark on the high shore is this crab with red eyes, possibly (Eriphia sp.). There were lots of them busily foraging this early morning. Later, after sunrise, I didn't see these crabs or the land hermit crabs out on the shore anymore!It was a delight to see not one but TWO of these Mosaic crabs (Lophozozymus pictor). They are highly toxic and shouldn't be eaten. This crab is listed among our threatened animals.A special surprise was this swimming crab with banded legs, spotted by Sam. I've seen it once on Sentosa a long time ago, and only a few times at Labrador. So it's nice to see it again. I don't really know what it is.Among the coral rubble were several of these large flatworms (Acanthazoon sp.). But alas, I failed to spot any nudibranchs or other slugs.Another common worm on this shore is Eunice. The Giant reefworm (Eunice aphroditois) can grow to 1m long! It slithers out quietly to snatch a bite of seaweed before slipping back into its hiding place among the rubble.I've been seeing cowries regularly on Sentosa too. This snail covers its shell with a part of its body, so it is sometimes mistaken for a slug. Most people only recognise it when they see the underside. Dead cowrie shells are more familiar than living ones.Among the larger fishes encountered was this small Brown sweetlips (Plectorhinchus gibbosus). It looks just like a dead leaf!

Of course Sentosa we love for its living corals. Hard and soft corals are colonies of tiny animals called polyps.In leathery soft corals, the polyps have branched tentacles and live in a shared leathery tissue. Some look like flat omelettes. Here's another kind of leathery soft coral that look like discarded surgical gloves, with fat fingers.

In hard corals, the polyps have smooth tentacles and create a hard skeleton. The entire colony is made up of the joined up skeletons of countless polyps.
Here's possibly a Favid coral (Family Faviidae). The polyps create a maze-like pattern that reminds me jig-saw puzzles.Porites corals (Porites sp.) have tiny tiny polyps that form a boulder-shaped colony.This is another kind of hard coral that also forms boulder-shaped colonies. It is Goniopora sp. and there are tiny brown acoel flatworms on the green polyps. So we can't really tell the hard corals apart simply by the colony shape.This is Psammocora sp. which forms short branches and the polyp tentacles are tiny.Turbinaria sp. often forms plates, sometimes in 'ruffles'. The polyps are a little larger.Not all hard corals are attached to the ground. This mushroom coral (Polyphyllia sp.) is a free-living hard coral. It has long tentacles with white tips. And for the first time, I noticed that the tentacle tips may be branched! Wow.
There is also a beautiful specimen of the Staghorn coral (Acropora sp.)! This kind of coral is rarely seen on our shores.Here's a closer look at the polyps. This kind of coral is distinguished by a big cylindrical polyp at the branch tip. It is among our fast growing corals.The nice thing about seeing corals at night is that many of them have their polyps expanded.They are quite beautiful if you take a closer look at them.Alas, I came across one colony that was bleaching. Many hard corals harbour symbiotic algae in their bodies (called zooxanthalae). The algae makes food from sunlight (which is why hard corals need clear water) and shares the food with the coral host. In return the corals provide a place to stay and other substances the algae needs. It is the algae that gives hard corals their colours.When a hard coral bleaches, it has lost its symbiotic algae and thus turns white or colourless. The polyps are still alive, as can be seen from the closer look above. Hard corals bleach when they are stressed: too hot, pollution, water too murky. Without their symbiotic algae, bleached hard corals eventually may die.

During the TeamSeagrass monitoring today, the Team also noticed that the seagrasses are doing poorly compared to previous visits.

Just off Sentosa, major reclamation work on the Pasir Panjang port extension is on going. These look like the barges involved in that project. Around the corner, reclamation on Sentosa for the IR has also started.This large barge looked like it was moving out of the IR site. On the way out I paid closer attention to the sign that Sentosa had placed at this beach.It's nice that they had posted a 'final reminder' about not removing marine life from this beautiful natural shore.

It was really nice to have some of the Reel Revolution participants join us for this trip! I hope they found the trip interesting and meaningful.

1 comment:

Zeitgeist said...

hi, i'm trying to contact you guys, is there a number i can call u all at? - email me at weizen.t@gmail.com?