wild shores of singapore: Portent of death on Chek Jawa?

29 March 2010

Portent of death on Chek Jawa?

I was out with TeamSeagrass for the Field Orientation, and was distressed to see many bleaching and yellowing carpet anemones.

From the Boardwalk to the Northern sand bar. Both those in water and those out on the sand bar. Big ones and small ones.

What does bleaching mean?

Carpet anemones (Stichodactyla haddoni) harbour symbiotic single-celled algae. The algae undergo photosynthesis to produce food from sunlight. The food produced is shared with the sea anemone, which in return provides the algae with shelter and minerals. These algae are believed to give the anemones their brown or greenish tinge. When an anemone is stressed, it may lose its algae and thus its colour, making it appear bleached.

Although there were also many anemones with normal coloration.

There were some that was only partly bleached.

There were also several stressed sea cucumbers in pools of water.

Here's another sea cucumber, I'm not too sure what kind it is. But it seems to be a Smooth sea cucumber that usually lies buried in the sand.

I also saw out on the sand, several Ball sea cucumbers (Phyllophorus sp.) which are usually buried. They too looked rather stressed.

I had seen bleached anemones, especially before the mass deaths of 2007 following massive flooding. Kok Sheng studied this event, read more about it on his project blog. I'm not sure if the same thing is happening again. Or perhaps it has just been too hot lately?

I did see similar situations in the past (see these flickr sets), a rather severe one in 2004, and less severe in 2005 and 2006. Let's hope this situation will pass and that the sea anemones and other marine life will recover.

Alas at the Northern shore, I saw almost all the large oysters (Family Ostreidae) on the rocky shore had been pried open. I'm not sure if the birds did it or if this was a result of some itchy fingered humans.

And here's another mystery. We saw several Cake sand dollars (Arachnoides placenta) that had their undersides broken up. From the many footprints around the over-turned sand dollar, it seems to be the handiwork of a small shore bird.

What is mysterious is that nearby, there were also several overturned sand dollars that were not mutilated. Could it be that the shore bird only pecked at sand dollars with something nice to eat inside? Perhaps eggs?

We also noticed tiny star-shaped bits near the pecked sand dollars. Possibly a part of the sand dollar's mouth?

Well, all is not death and gloom on Chek Jawa. The starfruit tree (Averrhoa carambola) was blossoming and fruiting!

And the Durian tree (Durio zibethinus) is starting to bloom!

And Alvin spotted a Spitting cobra as we did a quick run around the Mangrove boardwalk at the end of our monitoring session! Wow! I had a closer encounter with this snake when we explored the mangroves at Ubin on another trip. You can read more about the Equatorial spitting cobra (Naja sumatrana) on Nick Baker's excellent fact sheets on snakes.