19 October 2008

Chek Jawa: check up on the coral rubble area

A glorious blue sky day with TeamSeagrass at Chek Jawa was an opportunity to see how this fabulous shore is recovering from the mass deaths in early 2007.
Here's Changi point as we headed out, with Pulau Ubin in the background. Chek Jawa is right at the tip of this part of Pulau Ubin.

So how's Chek Jawa doing?

The seagrasses are doing marvellously, as the post on the TeamSeagrass blog describes. There was also large amounts of seaweeds of various kinds. On the high shore, piles of bright green Ulva sp. had accumulated. In the mid-water range on some parts of the seagrass area, Caulerpa mexicana was in full bloom. While on the coral rubble area, short reddish bunches of Gracilaria sp. was in abundance.

It was a good low tide so I headed out to the coral rubble area to do a quick check. Besides the lush seaweeds and seagrasses, there didn't seem to be much of the familiar fauna that we used to see before the mass deaths.There were a few clumps of sponges, but these were at the low water mark. The carpet anemones (Stichodactyla gigantea) were doing well though.Two Nobel volutes (Cymbiola nobilis) were seen, including this diligent mama laying an enormous egg mass!Besides the usual big bright orange hermit crabs, there were lots of these little ones (probably Diogenes sp.)And clinging to a purple sponge, this tiny unidentified hermit crab.
I saw one of this Kite butterflyfish (Parachaetodon ocellatus) but others in TeamSeagrass reported seeing lots more in the seagrass area. This fish is flattened sideways and disappears when viewed head on or from above!
Alas, I saw this poor Striped eeltail catfish (Plotosus lineatus) with its tail chomped off. It was still alive, feebly swimming about. Other little fishies seen included some perchlets (Family Chanidae) and cardinalfishes (Family Apogonidae).

Chek Jawa is famed for its echinoderms so it was nice to see the usual suspects in the coral rubble area.The Warty sea cucumber (Cercodemas anceps) on the left, and the Thorny sea cucumber (Colochirus quadrangularis) on the right.And it was heartening to encounter this sea cucumber with dark blue and orange stripes. It used to be quite common in this area. I have no idea what kind of sea cucumber it is.
The stars were out in force in the sandy lagoon near the coral rubble area. These small sand stars (Astropecten sp.) were busy foraging after sun set.This bigger sand star (Astropecten sp.) is also commonly seen on our northern shores. There were also Biscuit sea stars (Goniodiscaster scaber) and this lovely specimen of Gymnanthenea laevis.But the best find must surely be three baby Knobby sea stars (Protoreaster nodosus).
I found this one, while the Star Trackers found another, and Chay Hoon found yet another! Alas, we didn't see any adults.

Before heading out to the coral rubble area, I caught up with Dr Dan on the northern sand bar.
Dr Dan was very glad to see that the carpet anemones had returned, even on the sand bar. We also saw lots of peacock anemones (Order Ceriantharia) and sand dollars (Arachnoides placenta), as well as Garlic bread sea cucumbers (Holothuria scabra). But we couldn't find any Button shell snails (Umbonium vestiarum).

As we walked back together, Dr Dan shared that this phlegmy thing we often see are polychaete worm egg masses!He said if we look closely we can see the strings of eggs embedded in the jelly like mass. And he says, sometimes, you can even see the tiny worms wriggling about inside the mass! Wow, we should take a closer look at these icky things when we next encounter them.
Dr Dan also show the parasitic barnacles on this poor living crab. The little sacs that emerge from the host crab are the egg capsules of the barnacle. The barnacle itself is hidden inside the host and ramifies (grows like a root system) through the crab. Ewww.
And it was also nice to see a living Tiger moon snail (Natica tigrina) on the shore. I haven't seen one on Chek Jawa for a long time.

It's good to have a chance to see how Chek Jawa is doing, and wonderful to have spent time with Dr Dan, Siva and Airani, Kok Sheng and the Star Trackers and TeamSeagrass!

Kok Sheng has done a more comprehensive review of the coral rubble area on his CJ project blog.

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