A Rainy Semakau Walk on 4 April 2010

The sky was overcast when I left home around 5.20am on 4 April 2010. When I reached Marina South Pier, it started raining. To think that it had been bright, sunny and very hot for the past few days, we were indeed a rather unlucky that we should get bad weather when we were going to conduct a Semakau walk!

I was guiding a group of students from Raffles Institution, and my group name was "Seahorse". The students soon arrived, but the rain still had not stopped! We boarded the boat and after about an hour, we reached Semakau.

The rain had stopped then, but only to start again when we reached the entrance to the secondary forest. As a result, we had to wait for about an hour under a shelter until the rain was less heavy and eventually become a little drizzle, and I decided to bring the group to the intertidal area.

Despite the rain, I have to say we were still lucky enough to see many interesting organisms, even though most of them were hiding from the rain!


Here's my group crossing the seagrass meadow. The rain had almost stopped then.


This is a Heart Cockle (Corculum cardissa), and this is definitely one of my favourite clams on Semakau! It got its name from its heart-shaped shell. This cockle can burrow into the sand, and thus it can be rather hard to find them sometimes.


We have been regularly spotting juvenile Cushion Stars (Culcita novaeguineae) for past one year. They appeared to be moving towards the reef edge though. This sea star feeds on corals, and as it grows bigger, the arms will be less obvious and it will look more like a pentagon-shaped cushion instead, hence the common name.


The Green Ceratosoma Nudibranch (Ceratosoma sinuatum) appear to be in season, and we have been seeing them for the past few trips.


This small Black Long-spined Sea Urchin (Diadema setosum) appeared to have been trapped in a tidal pool by the receding tide. They have venomous spines, and thus should not be handled with bare hands.


As usual, the star of the trip is the Knobbly Sea Star (Protoreaster nodosus)! This huge sea star can grow to over 35cm wide, and come in shades of red, orange, brown and beige.


And here's our traditional shot with the knobbly!


At the reef edge, we visited our resident Fluted Giant Clam (Tridacna squamosa). This clam feeds on plankton and tiny organic particles in the water. At the same time, it harbours symbiotic algae in its body. The algae photosynthesizes and pass on some of the food to the clam, and in return gain shelter and protection.


We saw several nudibranchs, and here's another one - a Funeral Nudibranch (Jorunna funebris).

I guess all in all, we were still rather lucky to have seen so many interesting things despite the rain.

One the day before this, we had a survey trip on Semakau too, and we had a scorching sun instead of the rainy weather.

Just to highlight three of the special things we saw:


I found this very pretty sap-sucking slug, a Plakobranchus sp. This is the first time that we saw this on Semakau.


Another new record for the intertidal area of Semakau will be this Forskal's Sidegill Slug (Pleurobranchus forskalii). According to the Nudibranch Encyclopedia, this slug feeds on ascidians.


While we regularly see the Spotted-tail Frogfish (Lophiocharon trisignatus), it was so cute that I decided to still include it here.

It was a great weekend on the whole. Looking forward to find more new things next month... :)