Chek Jawa with Dr Dan

After about one year of absence from the intertidal shores of Chek Jawa, I had the honour to be back here again this time with Dr Dan and his students!

Every year, Dr Dan leads a group of students from the Duke University's Nicholas School of the Environment on an Urban Tropical Ecology in Singapore trip and will never fail to share Chek Jawa to his students.

Since Dr Dan and I have not been down to the shores for a year, we could very quickly figure how much the shore has changed! Other than the ever-shifting sand bar, we noticed something delightful... the Carpet anemones (Stichodactyla haddoni) seem to be coming back slowly but surely.

Here is an assortment of the different carpet anemones with different colours. They used to be so common and abundant before the mass death in 2007 such that they look like landmines on the sandbar.

Some of these carpet anemones have settled well among the lush seagrasses of Chek Jawa.

We saw many juvenile carpet anemones on the sand bar and this is a good sign!

One Common sea star (Archaster typicus) was found during the trip. I did not really have the opportunity to look for the colony of them on the sand bar as the tide was not very low.

Buried or semi-buried on the sand bar are sea cucumbers and sea stars such as this Smooth sea cucumber and the Plain Sand star (Astropecten indicus).

We stumbled across this dead plain sea star with lots of snails feasting on it. This of course is not a result of any physical stress such as drop of salinity but a natural occurence of feeding / scavenging on dead animals.

I got the sense from this trip that the number of Cake sand dollars (Arachnoides placenta) on the sand bar has dropped. It could be because that the tide was not that low. We noticed many pecked sand dollars with the star-shaped jaw exposed. These sand dollars were recently predated on by shorebirds.

We tried to look for the Button snails (Umbonium vestiarum) and after a while, Ria shared with everyone that she has found live ones on the sand bar! The density of these snails are not high but these snails seem to be bigger than usual. We also found one Lined moon snail (Natica lineata) which is actually a predator of the button snails.

Dr Dan found a rare snail! This is the Naked moon snail (Sinum sp.) which I think has not been sighted at Chek Jawa before.

The mantle of this snail is such that it cannot fully retract back into its flat thin shell. It sure can stretch itself and elongate quite a fair bit!

The empty shell of a Tun snail (Family Tonnidae) was spotted! Are living ones lurking somewhere out there?

Cindy found this large shell of a Bonnet snail (Phalium glaucum) that is occupied by a hermit crab. The living version of this snail is actually rare and not commonly sighted.

This is an interesting view of the cerianthid which is also known as peacock anemone. The cerianthid actually lives within a tube which is visible in this photo from top down position.

We came across this washed up Common sea pen (Pteroides sp.) with a porcelain crab living within. It was found quite high up near the mangroves.

Surprise surprise! It was great to spot the dugong feeding trails again!

Here's Dr Dan with his students having a closer look at the trails. The trail seem to suggest that two dugongs were feeding on the seagrass together!

Before we left, we had an aerial view of the shore from the tall Jejawi Tower. 

It was indeed wonderful to be back at Chek Jawa to see how it is recovering since the mass death. As for now, I do really hope to be back on a super low spring tide to check out the coral rubble. My previous check up on this fragile but rich habitat was in 2009. 

Checking Chek Jawa (April 2011)

It has been a really long time since I last stepped on the shores of Chek Jawa! The previous time was during January in 2010 which was more than a year ago. How has Chek Jawa been? I had a quick look at the shore while the Teamseagrass volunteers were busy surveying seagrasses.

The Carpet anemones (Stichodactyla haddoni) are one of the first organisms that I had a look to see how they are doing on the shore. These anemones are still not as abundant at the southern sand bar when compared to the northern sand bar. This photo shows the anemones at the north of Chek Jawa.

Many of the juvenile carpet anemones that I have seen back during my survey days a couple of years ago have grown bigger along the northern sand bar. This is indeed heartening.

Somehow these anemones are able to tolerate the presence of sand on their tentacle surfaces. With hope, it is possible that the northern sand bar will be home to even more of these anemones. This may probably help Chek Jawa return to its former glory where there are so many of these carpet anemones on the sand bar.

Other than those found on the sand bar, there are also many carpet anemones living within the lush seagrass meadow.

Many of these carpet anemones among seagrasses and seaweeds look healthy based on their coloration. We are glad to know that these creatures survived some extreme weather conditions, especially in January this year when there were heavy rainfall.

I only saw a small number of Peacock anemones (Order Ceriantharia) during this trip. I think it is because of the really hot weather that day.

Not sure if it is because the tide was not so low or that the seagrass meadow has shifted, there wasn't much of the southern sand bar exposed further away from the boardwalk. As such, I did not encounter many Cake sand dollars (Arachnoides placenta) in the south than in the north.

But as usual, at locations where these sand dollars are found, these echinoderms aggregate in large numbers.

Also due to the hot weather, I could only find a few of these Plain Sand stars (Astropecten indicus) which can be found in great numbers especially below dawn or after dusk.

A couple of the Common sea stars (Archaster typicus) were found near the southern sand bar. However, I did not see more of them elsewhere. Will they be able to procreate more individuals successfully to recolonize the sand bar as like before the mass flood? Only time will tell.

The sea cucumbers were well represented during the trip. There are about 7-8 different species found in this photo collage. The presence of these soft bodied invertebrates indicate that the salinity is within tolerable range.

Near the floating pontoon, I came across mats of what looks like that belonging to the Asian date mussels (Musculista senhousia). But after checking it out, I realize there were no bivalves inside the mat. I wonder what this is.

With the help of volunteers, Nparks has consistently been giving guided walks to the public to share the natural wonders of Chek Jawa with everyone. Kudos to their hardwork in raising awareness of the shore which we all love and would want to preserve.

I do agree that the ecosystems in Chek Jawa are indeed dynamic. Especially in the shifting in zonations of the sand bar and seagrass meadow. The button snails have gone MIA again. I believe it is probably a seasonal thing as they will migrate into deeper waters at certain stages of their life cycle.

Let us just continue to keep a good watch at this precious living shore.

More of what I've seen during this trip in my God's Wonderful Creation blog.

3 years after the mass mortality event

It's January 16th of 2010 and almost exactly three years after the gruelsome mass mortality event that occured in Chek Jawa. Joining Teamseagrass on the shore, I went to have a quick short look at how is the shore doing for now and whether is Chek Jawa hit by the impact of the 'Dead fish zone' at Pulau Ubin.


The relative positions of the sandbar and the seagrass always seem to be rather dynamic and whenever I visit Chek Jawa after many months (my last visit was Aug 2009), it seems to have changed a bit.


This time, there were many of the Noble volutes (Cymbiola nobilis) laying eggs. But I thought I should look out for the soft bodied animals to see if low salinity has impacted them. A week ago, my friend Pamela mentioned that the salinity at Pasir Ris was 16 ppt.


The only sea star species I came across is the sand star (Astropecten indicus). Did not sight the common sea stars (Archaster typicus) but they are still around as they have been seen during CJ guided walks.

Instead, I saw a wide variety of sea cucumbers! Here's the list of them...


This is the Pink warty sea cucumber (Cercodemas anceps).


Thorny sea cucumber (Colochirus quadrangularis).


This is the Smooth sea cucumber that is usually only found buried in the sand.


There were quite a number of the large Garlic bread sea cucumbers (Holothuria scabra) that seem to be settling well for some time already.


Last but not least, this Purple sea cucumber (Family Cucumariidae) that we usually see on northern shores.

Glad that the sea cucumbers are fine! That's a good sign.


As usual, the sand dollars are teeming certain parts of the sand bars, especiall the north. They are usually covered with a thin layer of sand.


And here's a closer look at this Cake sand dollar (Arachnoides placenta).


One of my task is to find the return of the Button snails (Umbonium vestiarum). They have been missing for 1.5 years! And I'm so happy to find them back in big patches on the north. Yay!


How about the Carpet anemones (Stichodactyla haddoni)? Almost all of them look fine with no signs of bleaching. Some of them settled well among the seagrasses.


A pleasant surprise will be the north shore where many of the carpet anemones have colonized the sandy area. Can you find all five of them together in this photo?


Here's one of the prettier carpet anemone.


My impression of the number of Peacock anemones (Order Ceriantharia) remains the same though. I didn't really see an increase though it was just a general feel.

That's about all for the animals that I usually look out for to monitor. But of course, Chek Jawa is alive and there's other creatures that I found along the way.


Like this bunch of cuttlefish eggs in black.


I found these weird orange blobs on the seagrass blades. Are they ascidians or egg masses of some animals?


It was interesting to once again come across another of the giant-sized Mud crab (Scylla sp.) on the shore. I didn't dare to get too close as it was too big and scary looking.


An interesting find will be this moon snail that I don't think I have ever seen before alive. It has a brownish shell.


And here's the underside. Hope someone can provide the id.


Whereas James found a solefish that I can't really tell its exact identification too.


I was thrilled to find this featherstar clinging on the knobbly sea fans on the pillar of the floating pontoon. Have not seen featherstars at Chek Jawa for a long time!


The legs of the CJ boardwalk is teeming with sponges and ascidians.


And below some of them, once again, are many egg-laying noble volutes. Haha. Can you spot the cowrie at the pillar leg too?

That's all for a short one-hour check out. Glad to know Chek Jawa is recovering well, with no signs of being impacted by the dead fish zone or low salinity. :-)