Quick Look at Sisters Island on 26 Oct 2011

I was back on Big Sisters Island today for a picnic organised by a friend. As the main focus wasn't on the shore life, I only managed to sneak out to check out the shore for like an hour or so. Tide wasn't that low by then, but fortunately I still managed to find a number of stuff :)


I was most excited to find this Fluted Giant Clam (Tridacna squamosa) in the lagoon - had not been able to find it for my past few trips here! The metal stick on the right probably indicated that Mei Ling, who worked on giant clams, was studying it. This one is about 30cm wide.


Most of the people on the island were more excited about the Long-tailed Macaques (Macaca fascicularis) though. There were more than 10 of them and they were really rather daring. We were kept busy for quite a while keeping them away from the food.


The smaller lagoon, as usual, had many Sand-sifting Sea Stars (Archaster typicus). These sea stars sift among the sand for tiny decaying matter (detritus) to feed on.


There were quite a few moon snail trails. I dug one out and it was a Pear-shaped Moon Snail (Polinices mammilla).


At the mouth of the small lagoon, there were a few Haddon's Carpet Anemone (Stichodactyla haddoni), and I found some Anemone Shrimps (Periclimenes brevicarpalis) on them! These shrimps had a layer of mucus on their body to prevent the anemone from stinging them, while being protected from predators by the stinging tentacles.


I found a few tiny Ocellaris Clownfish (Amphiprion ocellaris) in some of the Giant Carpet Anemones (Stichodactyla gigantea) near the mouth of the lagoon too!


Branched Sea Anemones (Phymanthus sp.) were as abundant as ever. They looked like little flowers of the sea...


Leaf Slugs (Elysia ornata) were in season, and I saw many of them among the seaweed. These sea slugs sucked the sap of the seaweed and retained the chloroplast in their body for photosynthesis. And so they were somewhat "solar-powered", like plants!


At the rocky areas, I saw many Black Sea Cucumbers (Holothuria leucospilota) among the rocks and coral rubble.


There were many snails on the sea wall, but the limpets caught my eye, as I suddenly remembered a friend who was studying them for her honours project.


I only saw one nudibranch, a Discodoris boholiensis. "Nudibranch" means "naked gills", refering to the flower-like gills on the back of most species.


Fanworms (Sabellastarte sp.) were also rather common at the coral rubble area.


The Red Maiden's Fan (Oceanapia sagittaria) is probably my favourite sea sponge - the bulk of the sponge is actually hidden in the ground.


Sisters Island has a very nice and dense intertidal coral reef. All the brown boulders above were hard corals! They are mostly brown due to this golden-brown algae (called zooxanthellae) that live inside them. The algae photosynthesize and provide nutrients for the corals, while getting shelter in return.


Some corals, such as the Turban Coral (Turbinaria peltata) above, have their own colour pigments that act as sun block, and hence they may appear greenish, bluish or even purplish.


Coral reefs can get rather colourful sometimes - the above shows some corallimorphs among some sponges.


Algae, like the red algae above, can be brightly coloured too!


So are the colonial ascidians.


Some of the areas had lots of Zoanthids (Palythoa mutuki), which looked like little flowers carpeting the area.


Even smaller are the tiny polyps of the Toadstool Leather Coral (Sarcophyton sp.).


The tide came back rather quickly, and I had to stop my exploration. As we were leaving the island, I noticed that the trash bin were really not very monkey-proof... Hopefully Sentosa will do something about this, since they are managing the island!