How's Chek Jawa so far?

It has been more than 2.5 years since the mass dieoff that occured due to an exceptional heavy rainfall in Dec 2006 and Jan 2007. Though my project has officially ended, recovery never ceases. I took the opportunity of today's Teamseagrass monitoring trip to take a short look at this special shore.


Time was short and I quickly made down to the coral rubble to catch the lowest tide. And it was heartening to see a pinkish Knobbly sea star (Protoreaster nodosus) just near the Chek Jawa beacon. I remember that they were not sighted for eight months after the mass death event. Many had died due to the extremely low salinity which were recorded to reach below 10ppt. Click here to see a photo of a dying Knobbly sea star shot by Ron during Jan 2007.


Aren't we glad that there are now back? Today, not only did I see one or two...


But actually three of them! I will later send these photos to Chee Kong for his Star Tracker monitoring.


More stars that can be found at the coral rubble include the various sizes of the Biscuit seastars (Goniodiscaster scaber).


But another sweet find at the coral rubble is this large adult-sized Cake sea star (Anthenea aspera). It was very much bigger than my palm!


The carpet anemones Haddon's carpet anemones (Stichodactyla haddoni) near the coral rubble facing Sekudu are doing very well.


There are many of them and it was difficult to avoid stepping on any of these large anemones.


Though much of the corals seem to be affected after the mass flooding of rainwater, two colonies of the Pore corals (Porites sp.) were found. I hope there are more of these huge corals at the deeper waters, which I didn't get to check because the tide was not exactly super low.


Zoanthids were also scarce and I only spotted two small patches of them.


That goes the same for the sponges. Chek Jawa used to be home to lots of colourful and good growths of different types of sponges. It was not too easy to find them today.

But all these does not mean that the coral rubble is not doing well. As said, the tide today was not low enough and it is possible for the more delicate animals to be found more abundantly at the deeper waters.


I went to check out the pillars of the boardwalk and was quite glad to find more sponges of different colours encrusted onto them.


More sponges and ascidians attached on the pillars.

Weirdly, I didn't spot any of the Pink flowery soft coral (Family Nephtheidea) that were previous seen at the rubble and the pillars of the boardwalk. I did see one colony of Sea fans (Order Gorgonacea) though.


I quickly went over to the seagrass lagoon and main sandbars to check out the animals there. The carpet anemones are still there as usual as well as the large numbers of the Cake sand dollars (Arachnoides placenta) that crowded many parts of the sandy shore.


These sand dollars leave imprints on the sand that are circular in shape. I didn't find any of the rarer keyhole sand dollar though.


It was day time and most of the abundant sand stars (Astropecten sp.) had burrowed into the sand since they are norturnal in nature.


I was on the lookout for the Common sea stars (Archaster typicus) by the five-arm marks on the sand but instead stumbled upon a brittlestar.


Good thing was that Adelle later showed me one of the common sea star. I heard from her that many of them have been spotted during the guided walks. This is good news.


I guess at the sand bar, the most drastic change in terms of population will be the Garlic bread sea cucumber (Holothuria scabra)! They are very common today considering many others are buried under the sand. Who knows how many is now at Chek Jawa. We do not need another mass death to suddenly see tons of these poor cucumbers die and surface on the sand.


How about peacock anemones (Order Ceriantharia).? At some parts of the seagrass lagoon, they seem to be doing well!


There's no sign of discoloration or poor growth of some sort.


I quickly walked to the north to search for the Button snails (Umbonium vestiarum) that have been missing in action for a long time.

However I couldn't find any living button snails.


There were dead shells though. A sign that they are still around somewhere, I think subtidally. They do migrate to and fro different zonations so I am not too worried.


Sunrise over Chek Jawa signifies new birth after the mass mortality event. A birth of a human being takes many years to mature, not to say an ecosystem.

Let's hope Chek Jawa has many good years more to go to recover back into its former glory, slowly but definitely surely.

Article at Nature Watch is out!

Ria passed me the latest copy of Nature Watch this morning showing me that the article I've written for the magazine has been (finally) published! I remember doing this writeup end of last year.


It is a six-pages article. Feel free to purchase this latest copy from Nature's Niche if you are interested.

Would like to take this opportunity to thank Dr. Peter Todd for encouraging me to do this writing and be there to guide me along. Ria, Ron and Siva for the photos. Liana, Mei Lin and other friends whom have vetted the draft. Last but not least, the editors of Nature Watch for their great work in getting this article published.

Chek Jawa in May 2009

It's been some time since I have updated this project blog. Finally got a chance to check out Chek Jawa after the Teamseagrass field session just last Saturday.

How are the animals doing?


Recovery, I must say, is slow but steady. There are not many carpet anemones on the sandbar as compared to the past, but they are slowly coming back. This photo was taken at the southern sand bar.


The northern sandbar also has many of carpet anemones, especially at the water edge. It's a good sign.


Some of them look bright...


While the most look rather pale, which I thought it's quite usual for these carpet anemones.


I do suspect that the strong solar radiation in the recent afternoons has bleached out some of the carpet anemones like this one.


And this carpet anemone too. Good thing is, these are the only two bleaching carpet anemone out of the close to fifty carpet anemones I encountered during that day.


The southern sandbar just beyond the floating platform is still littered with tubeworms!


And among the tubeworms, I spotted this geographical seahare.


How about the button snails? Are they back yet? They have been missing exactly since one year ago. At least intertidally. I saw many of these white skeletons of the button snail shells at the northern sandbar.

Did they just died recently?


I also found some of the intact button snail shells with hermit crabs. Which proves that the button snails persisted during this one year. Just that they have probably migrated to the subtidal area.


As usual, the sand dollars are just so abundant! And many of them are really big. Alas, no keyhole sand dollars could be found. They are rare as usual to be found.


I went back to the same patch where common sea stars were last found and the stars are still there!


In fact I spotted two pairs pseudo-corpulating! Good... go procreate more!

That's all for the key animals that I was monitoring for. There are also some other creatures that I stumbled upon during the survey.



Like this smooth sea cucumber...


This aggressive elbow crab...


And this yellowish bristleworm.


Beneath the floating pontoon are a huge growth of the green mussels.


The hard substrate, together with many of these mussels, created crevices where many of the thunder crabs can be found.

That's all for the update this time! :-)

A 2009 good start for Chek Jawa

How is Chek Jawa two years after the massive freshwater flooding event in 2007?


There are many tubeworms that have colonized most part of the northern sand bar. Alas, button snails were missing. Could it be that both tubeworms and the button snails cannot co-exist or that the button snails have migrated to the subtidal area?


How about the southern sand bar? There are parts where you can find balls of sand left over by sand bubbler crabs.


What is most heartening is the return of juvenile and mid-sized carpet anemones on the sandbar, this time in more numbers.


Let's hope that their return will continue and we look forward to them crowding the sand bar like land mines though that might take many years though.


Today I couldn't find any peacock anemones that are showing much of their tentacles. Could it mean anything?


As usual, there are many sand stars out on the shore.


And we are all very happy to see the common sea stars back, we counted eight today in one tide pool.


These are adults that most probably escaped the flooding death toll by burrowing very deep or going deep into the subtidal area.


The biggest surprise is this rare six-armed sea star (Luidia penangensis). Read more about this special sea star and other fantastic finds on my God's Wonderful Creation blog.

Looks like Chek Jawa has a good start for 2009! Let's hope that there will be no massive rainfall event or flood for this month.

A quick check at the coral rubble

It has been more than two months since I've checked Chek Jawa out. This time, I was fortunate to have Dr Dan, Siva and Airani joining to have a good look at how Chek Jawa is recovering.


Here is Chee Kong with Dr Dan and Airani. Apparently, Chee Kong and Sijie were being filmed for some programme.


It was surreal to be back at this wonderful place at a good weather. Soon, we were on a mission to check out the identification of the plentiful tubeworms at the northern sandbar, which was a success!

Quickly, I did a followup survey on the peacock anemones and there were a few more new additions in the survey plots to my previous count during January 2008. This is great.


The team seagrassers were also there to monitor the lush seagrass. Some of them alerted me and they have found a juvenile kite butterflyfish.


Time and tide waits for no man and I headed to the coral rubble area (the prominent icon of this area being the beacon) for my last agenda of the day since the tide was low enough to check this fragile and rich spot of Chek Jawa.


There were a number of these fanworms which has tentacles that swirl gracefully in the waters.


Soon, the Star trackers found a juvenile knobbly sea star which was exciting. They proceeded with the measurement. Am looking forward to their analysis of the knobblies in Chek Jawa since recently we see many juvenile ones.


The carpet anemones were doing well.


Stuck at the sandy substrate are many of these fan shells.


However, sponge recovery was not that fast, many of them were still sparsely distributed which small sizes. But it is good to see from this photo that there are quite a number of different species represented.


More sponges....


And more sponges. Be patient and I hope they will comeback in bigger numbers and sizes.

Below are many more of the marine organisms found at the coral rubble.


I was venturing deeper into the coral rubble carefully, to avoid stonefish and careless trampling. And I saw this thorny sea cucumber and a swimming crab.


There were also many of these anemones that we usually see at Pulau Sekudu.


Hydroids are man's enemies if we didn't wear longs.


Soft corals at the deeper parts of the coral rubble.


From the small colony of Porites coral.


to a bigger colony that I couldn't get a clear photo since it was deep in the water. Surprisingly, I didn't notice the colourful fish beside it until I was back!


Thundercrabs were also common foraging when the tide went out.

I also encountered a number of sea stars at the coral rubble.


Several biscuit sea stars.


The bigger Astropecten sand star, possibly Astropecten vappa.


Adult cake sea star. This photo shows a shrimp that I didn't notice till I was processing the photos. Indeed there's much life that awaits our discovery only if we decide to look closely and intently.


I found a rare find of this sand star with six arms just very near the cake sea star as well.

Towards the end of the check, I suddenly realized I was all alone in the shore while the rest has retreated back. So I quickly hurried my steps to head back.


Suddenly, this knobbly sea star caught my attention and I went to take a closer look. It has one of its arm chomped off.


Last but not least, I had a pleasant encounter with this charming Gold-spotted mudskipper (Periophthalmus chrysospilos) just beneath the boardwalk.

It was a good trip, and I believe that the coral rubble is slowly but surely recovering.

Recovery of Chek Jawa thus far

5am, one small team of us left Changi jetty, volunteering selflessly to do a health check at Chek Jawa. Though all of my regular gang were busy to make it, I am very grateful that Ginny, Pamela, Tze Hwee and Han Sheng could come and help put and also experience Chek Jawa for their first time.


It has been one year since I've arrived at Chek Jawa so early. But we get to enjoy the spectacular sunrise over the horizon of Pulau Tekong.

This stretch of Chek Jawa to the west of the coral rubble, near the House No. 1 jetty has very good growths and large numbers of adult carpet anemones (Stichodactyla haddoni).


It is postulated that this part of Chek Jawa seemed to have minimal freshwater impacts due to headlands that diverted the river effect from Johor River. Therefore, numerous carpet anemones are still thriving here and that this location also acts as a seeding site for recovery to the other parts of Chek Jawa.


The way they are found on the seagrass area of this part of Chek Jawa can come in random, clusters,


and interestingly, linear fashion, where five of them forms a straight line. I guess this is just purely coincidental.


But it is also possible that the carpet anemones here could be migrated from the other parts of Chek Jawa that were badly affected by the Jan 2007 mass death.


This is because they can uproot themselves in stressful situations and drift with the currents to a less stressful area.


However, I couldn't find the colourful variety of sponges at the coral rubble that I've seen before during December 07. Only many of these long branched purple sponges, as also observed by Ria earlier on, can be found.


According to our regular trips observation from northern shores, these long branched purple sponges are very common because they are quite tough and can be found even in inconducive conditions. What happen to the other "more sensitive" sponges? Was the tide not low enough to reveal the other sponges?


Ginny and I were doing checks at the coral rubble, one of which is to find the adult knobbly sea stars (Protoreaster nodosus). I think the tide wasn't super low enough (though 0.0m) to find the adults. But Ginny found this juvenile knobbly sea star that was enough to make me excited.


This means new blood of the knobbly stars for Chek Jawa! Can't wait for them to grow up.


Other sea stars spotted included a couple of the cake sea stars (Anthenea aspera).


This is the other cake sea star found at the coral rubble area.


As usual, there are many biscuit sea stars (Goniodiscaster scaber) that we commonly find at the northern shores nowadays.


I've also found a patch of zebra coral (Oulastrea sp.) growing in the interior of an abandon tyre.

Also spotted are zoanthids and flowery soft corals that I couldn't take a photo of due to the murky waters from the returning tides.

Next, we checked the sand bar and the seagrass lagoon area.


Several groundscape photographs were taken for monitoring over time and also to compare with the state of Chek Jawa before the mass death.

Tze Hwee, alone, was posted to search for the Button Shells (Umbonium vestiarum) at a far far northern sandbar. She couldn't find them though, even at the usual spots where I once recorded GPS points.


While everyone was hard at work, Pamela and Han Sheng were searching for the mussel beds within the seagrass lagoon.


To my surprise, we could not find any mussel bed today! This was in line with the missing mussel beds from Changi and also later on I realized those at the Ubin jetty were gone too. What was left behind were the mounds of mud that I believed were once trapped by the byssus threads of the once-existent mussels. Could their absence now be due to a seasonal reason or that the predators of these Asian mussels (Musculista senhousia) have completely wiped them out?

A study was done by Kushner and Hovel (2006) to the response of native predators (gastropod Pteropurpura festiva) to an invasive marine bivalve, the Asian mussel Musculista senhousia (Mollusca: Bivalvia: Mytilidae). The results of the study suggested that in overall, "intertidal or subtidal areas with high seagrass cover and high predator abundance may be resistant to invasion by Asian mussels, but the likelihood that a population of M. senhousia will become established will depend on the relative densities of predator and prey, M. senhousia settlement and growth rates, and the spatial and temporal scale being considered."

The study by Kushner and Hovel (2006) also stated that "native predators may be able to confer invasion resistance to local communities, but are unlikely to be able to control large, established M. senhousia populations"


Similar to the native gastropod Pteropurpura festiva from Kushner and Hovel (2006), many of the drills (Thais sp.) were once found on top of the mussel beds.


And the eggs of the drills were also present on the surface of the mussel beds.

It is possible that the predation of the drills on the mussels could have slowly but surely led to the elimination of the mussels from the mussel bed. Though Kushner and Hovel (2006) stated that it is difficult to control large populations, the seemingly shrinking of the mussel beds observed in May could be a factor that aided the predation of the Asian mussels which led to control and thus elimination.

Nevertheless, the real reason behind such an elimination is difficult to account for. A better knowledge of the relative densities of predator and prey, M. senhousia settlement and growth rates, and their spatial and temporal scale will be needed to give a scientific explanation.


There are many sand dollars towards the northern sandbar that are teeming on the sand.


Some of the tubes from the tubeworms were also photographed. This one is the bigger one.


And there is another type of tubeworms that are much smaller.


There were about less than ten carpet anemones starting to be found growing at the sandbar. Before the mass death, the sandbar was filled with these carpet anemones like landmines.

Hopefully with time, more of these carpet anemones will return to the sand bars.


The seagrass lagoon has yet another surprise for us, another juvenile knobbly sea star! Ria has also found two of them in July as well. This is heartening.


Underside of the juvenile knobbly sea star.

And for the finale....

Common sea stars (Archaster typicus) are still around!

However, they seem to be only found at a specific spot that I always return to search for them through GPS. I hope there are more elsewhere that we have no chance to stumble across because Chek Jawa is too large to properly do a search.

All too soon, the tide still had to return and we left the shore promptly.

My friends couldn't resist climbing the Jejawi viewing tower and it was a good opportunity to take a group photo of them. Thank you all for your help today!

A more light hearted post with other sightings during the trip: http://wondercreation.blogspot.com/2008/08/chek-jawa-check-with-friends.html

Reference:

Kushner, R.B. and Hovel, K.A. (2006) Effects of native predators and eelgrass habitat structure on the introduced Asian mussel Musculista senhousia (Benson in Cantor) in southern California. Journal of Experimental Marine Biology and Ecology 332(2): 166-177.

Talk on "Life and Death at Chek Jawa" at IYOR launch

Lauded for its high biodiversity with six distinct ecosystems, Chek Jawa received a ten year deferment from land reclamation in 2001 and has subsequently become a popular attraction among Singaporeans. However, a mass death of several marine animals occurred in January 2007. A study was later done to understand what contributed to the mass mortality event and evaluate the recovery of marine animals. It is true that a better understanding is essential to protect this fascinating shore. In this talk, Kok Sheng will share with the audience how is Chek Jawa faring and also his experiences and discoveries from the study.

About the speaker: Kok Sheng is currently an undergraduate in NUS, majoring in Life Sciences with specialization in Biology. In July 2007, he received the MOE Teaching Award. Kok Sheng has great interests in ecological work and did an UROPS (Undergraduate Research Opportunities Programme in Science) project under the supervision of N. Sivasothi, Peter Todd and Dan Rittschof. His project aimed to study the mass mortality and recruitment of macrofauna at Chek Jawa in Pulau Ubin. Since the project has application value in understanding and conserving the Singapore macrofauna at Chek Jawa, Kok Sheng's project has been featured in Protecting nature's beauty in The Straits Times (September 10, 2007), Embracing Passion Going Places, the NUS Advertorial in The Straits Times (March 25, 2008) and Tuesday Report: Children Of The Earth on Channel 8, Mediacorp TV (July 8, 2008). Kok Sheng is also a volunteer with TeamSeagrass, Naked Hermit Crabs and Raffles Museum of Biodiversity Research. He also runs the Chek Jawa Mortality and Recruitment Project blog and God's Wonderful Creation blog.

Date: 9 Aug- National Day (Sat)

Time: 10.30am

Venue: Function Hall, Botany Centre, Singapore Botanic Gardens (above Taman Serasi foodcourt), more about getting there.

Contact: iyor08singapore@gmail.com



More talks, events and fun during the International Year of the Reef (IYOR) launch here: http://iyor08singapore.blogspot.com/2008/07/9-aug-sat-reef-celebrations-launch-of.html