Semakau Walk on 27 Nov 2008

It's a low spring tide day again! This time round, we were bringing about 60 secondary school students who were also volunteers for Project Semakau. This trip would give them a good overview of some of the interesting marine life that could be found on the island, and how to identify them. With me was a group of students from Dunman High, and our group name was Octopus.


This was one of the mangrove trees at the exit of the secondary forest, probably a bakau minyak (Rhizophora apiculata). It has red stipules, and interestingly, I notice that the seedling had a red collar. Read from one of the online mangrove guide that mature propagules of Rhizophora apiculata has a red collar. This was something that I had not noticed before.


The students found this brittle star, which I have not seen before. Brittle stars can usually be identified by the presence of a circular central disc with 5 long arms attached to the disc. They move by swinging their arms, instead of sliding across the substrate with the tube feet found on the underside of their sea star cousins.


At the edge of the seagrass meadow, we found a population of sand sifting sea star (Archaster typicus). These sea stars are able to burrow into the sand to seek food (they feed on tiny organic particles) and also to escape from predators. Like other sea stars, they move with their tube feed on their underside, sliding over the surface of the substrate.


Another sandy shore dweller was this sandfish sea cucumber (Holothuria scabra). It too can burrow, feeding on the detritus (tiny organic particles) in the substrate. This sea cucumber is usually brownish in colour, sometimes with darker stripes on the top surface, making them look like "garlic breads", which gave it is other common name - garlic bread sea cucumber.


As we headed towards the coral rubble area, we were pleasantly surprised to see this unidentified sea star again, which looked like a combination of both the knobbly sea star and cushion star.


Among the coral rubble were lots of hairy crabs (Pilumnus vespertilio). The tiny hair on its exoskeleton traps sand and mud, allowing it to blend nicely into its surrounding.


We had been seeing several noble volutes (Cymbiola nobilis) lately, and it was no exception for this trip. This juvenile noble volute's shell was still very smooth and pretty, without any algae growing over the surface. It has a very pretty body with lots of bright orange spots on a black background.


In one of the tidal pools, we found this sea cucumber, which so far we have been identifying it as a dragonfish sea cucumber (Stichopus horrens). It is usually yellowish brown in colour, with a thorny appearance. Will probably need to find an expert to confirm its identity.


The spider conch (Lambis lambis) was regularly sighted in the coral rubble area, and has several protruding spines curving in the same way. Conches have two little eyes on a stalk each, allowing them to keep a lookout for any threats in the surrounding before they exposed their body to feed or move around.


In one of the tidal pools nearer to the reef crest, we found a sunflower mushroom coral (Heliofungia actiniformis). With its long tentacles, this coral is often mistaken to be a sea anemone. The long tentacles have a white tip each, and the hard skeleton of the coral is round-shaped and not attached to the substrate.


We saw 2 knobbly sea stars (Protoreaster nodosus). The one above looked like one of those juvenile knobblies which we saw during the Project Semakau launch.


This is one of the adult knobblies which we regularly see during our walks.


The table coral (Acropora sp.) is very common in the region in areas with clear water, as this coral requires lots of sunlight to do well. Acropora corals in Semakau's intertidal area are usually small colonies, and both branching and tabular forms have been seen.


Two long synaptid sea cucumbers were spotted today - one in the seagrass meadow, and the other in the coral rubble area near the reef crest. This is a very long sea cucumber, and we have seen those growing up to 2m long.


The funeral nudibranch (Jorunna funebris) is one of the most common nudibranch on Semakau. the term "nudibranch" means "naked gills", refering to the exposed gills found on the back of most species.


This is probably the stonefish sea cucumber (Actinopyga lecanora). We have seen many variations of coloration for this species, ranging from completely brown, light brown with dark brown patches, light brown with dark brown spots etc. The area around its back end is usually lighter in colour, and has 5 anal teeth.


There were lots of flatworms in the coral rubble area, though most of them were this Acanthozoon sp. Flatworms are very, very flat, and are usually ovoid in shape. They also have a pair of pseudotentacles at their front ends. Some of the bigger species are able to swim by flapping the sides of their bodies.


As we were heading back towards the secondary forest, I found this hell's fire sea anemone (probably Actinodendron sp.) in a small tidal pool. It has lots of branch-like tentacles which can give a nasty sting.


Here's a shot of the students in my group, crossing the seagrass meadow.


Sunset at Semakau is always so pretty...

I certainly hope that Project Semakau will be a success, and we can eventually turn this into a protected marine park! :)