10 January 2009

Chek Jawa with TeamSeagrass

Spent a glorious breezy afternoon on the seagrass meadows of Chek Jawa.

It was reassuring to see the meadows flourishing well, especially the pretty Fern seagrasses (Halophila spinulosa). There were all kinds of animals in the meadows. Chay Hoon found a really tiny sea anemone attached to a blade of seagrass! Here's her photo of this wee little nem.
How wonderful to see many Carpet anemones (Stichodactyla haddoni), in the seagrass meadows and on the Northern sand bar. These large anemones were severely reduced after the massive flooding in early 2007, which was followed by mass deaths on Chek Jawa. Kok Sheng's CJ project blog documents his efforts to monitor the recovery following this event.After the seagrass monitoring was done, Kok Sheng had a quick look to check out the situation. There's still large patches of tubeworms on the Northern sand bar. I noticed lots of bird footprints around the tubes. Perhaps the shorebirds are also checking out the tubeworms, for dinner!Cake sand dollars (Arachnoides placenta) were everywhere on Chek Jawa, and in some places were found in large numbers. Alas, Kok Sheng and I couldn't find any Button shell snails (Umbonium vestiarum) that used to be found in countless numbers on the Northern sand bar.I was very glad to see several of these large Garlic bread sea cucumbers (Holothuria scabra). But I didn't see any Ball sea cucumbers (Phyllophorus sp.). Both kinds of sea cucumbers were among the animals found dead in large numbers following the flooding in 2007. Both sea cucumbers are listed as Vulnerable in the Singapore Red List, mainly due to habitat loss. I also didn't see any Thorny sea cucumbers (Colochirus quadrangularis).But I did see, buried in the sand bars, lots of Smooth sea cucumbers. There were also several encounters with this flatfish. It is Commerson's sole (Synaptura commersoniana) which is regularly sighted at Chek Jawa and Changi but not so commonly seen elsewhere.Flatfishes undergo an amazing change as they grow up. When it first hatches, a flatfish larva looks like the larva of other ‘normal’ fish. As the larva matures, it starts to swim on one side of its body. One eye moves to what becomes the upperside, also called the eyed side. The mouth and one pectoral fin also becomes asymmetrically distorted. There are also changes in the skeleton and digestive system. The change may be completed within five days. Here is a fascinating photo of flounder larva and of flatfish hatching. And a post about fossil findings that suggest how flatfishes came to be.It was very nice to see a few Common sea stars (Archaster typicus) on a small area of Chek Jawa. Common sea stars were wiped out after the 2007 flood and it was nearly a year before we saw signs of them again. It's been two years since, and they have not yet recovered fully. In the past, these sea stars were abundant on Chek Jawa. The smaller Sand stars (Astropecten sp.) were not as badly affected by the flood and are still abundant today. But the 'Star' find of the day was Kok Sheng's spotting of this Luidia penangensis. According to Dr David Lane's "A Guide to Sea Stars and Echinoderms of Singapore", this sea star usually has 6 arms. Kok Sheng spotted it by examining more closely what at first glance appeared to be a Common sea star!On the underside, the sea star has bright orange pointed tube feet! Read more about this sea star on Kok Sheng's blog post.Chay Hoon also spots this large Mud crab (Scylla sp.) half hidden in the silty sand. Andy took a great video of the crab and the clip is on his blog.Today there was also a public walk at Chek Jawa, so lots of special animals were gathered on the Southern sand bar by the volunteer guides for the visitors.This was a collection of egg capsules. The big white ones on the right are of the Noble volute (Cymbiola nobilis) while the curved row of capsules on the left is by the Spiral melongena (Pugilina cochlidium). The orange blob is probably an ascidian.There was also a brittlestar!As well as this upper portion of a bristleworm, probably the Solitary tubeworm (Diopatra sp.).

Chek Jawa is a very special shore and there are lots of ways an ordinary person can make a difference for it. You can visit the shore, even at high tide. And you can join TeamSeagrass to help monitor this and our other seagrass meadows.

More links
More blog posts about this trip

1 comment:

  1. Wonderful finds! Wish I had the time to join you guys.

    If the colour of the pincers is an accurate indicator, the mud crab here might be Scylla tranquebarica. There's a Scylla olivacea in the mangroves close to the boardwalk, so we now know that at least 2 mud crab species inhabit Chek Jawa.



Related Posts with Thumbnails