Saturday, August 24, 2013

Amazing reef at Pulau Semakau's northern shore

Pulau Semakau, the island where many people know it as a landfill island being filled up by ash of incinerated rubbish disposed by us on Mainland Singapore. Not many people are aware of the flora and fauna beauty of Semakau. On the western side of this landfill island is an intertidal beauty consisting of mangrove trees, seagrass and coral reef along the reef edge.
Map of Semakau Lanfill and nearby submerged reefs.
[Google map by Ria Tan]
The shoreline is pretty long. You can probably walk the whole shore within the intertidal period if you only focus on the walking aspect, do nothing but walk.
We covered the northwestern part of the shore for today's trip, just opposite Terumbu Raya.

The tangled sponge (Callyspongia samarensis) is in abundance and widely spread around on this part of the reef. They look like bunches of green chewy licorice.
Tangled sponge
It has been quite some time since I last seen this little fellow moving about on a reef (or maybe it had been sometime since I took notice of it). This is a marine spider (Desis martensi). It is commonly seen on many of our shores, hides in air pockets among crevices during high tide and comes out to hunt at low tide.
Marine spider
As I was walking around on the reef, a reef octopus came out of a crevice under a sponge for a short while but it quickly returned into the hole as I approached.
Glimpse of the reef octopus
While staying on the spot waiting for the octopus and hoping that it will come out again, I spotted a blue-lined flatworm moving among the seaweeds.
Blue-lined flatworm
On this northern part of Semakau Landfill, the tape seagrass (Enhalus acoroides) are rather sparsely dispersed and looked cropped with broken leaf tips.
Tage seagrass
Another plant that is dispersed in clumps over the shore is the lacy red seaweed (Martensia elengas). They looked like sea mash of interesting lattice work encrusted with algae. When looked closely at the seaweed, one might think that it is fragments of disintegrated mash or some kind of fishing net.
Lacy rea seaweed
I also came across a few giant carpet anemone (Stichodactyla gigantea) but none of them had signs to show presence of the false clown anemonefish (Amphiprion ocellaris).
Giant carpet anemone
This ovum cowrie (Cypraea ovum) looks like the animal just died recently. Its shell is still clean and shiny. 
Overview of cowrie shell
Underside of ovum cowrie
However this tiger cowrie (Cypraea tigris) is very much alive and is a fast moving cowrie. It was Chay Hoon who spotted the tiger cowrie and alerted me.

Shell and mantle
This is an interesting small crab which I regret not giving it more attention when I saw it on the shore. After looking at this photo more carefully, I suspect that this could be the semaphore crab (Ilyoplax sp.). It was difficult to get the crab to move into a better position as it will move into hiding. After few attempts of fail crab coaxing, the crab when into a burrow.
Semaphore crab?
There were a few wiggly reef star anemone seen on the sandy reef and it is one shy anemone. Most of them that I came across retracts itself into the sand as I approach the anemone closer. This was the only anemone which I was able to take picture of.
Wiggly reef star anemone
The orange-spotted gymnodoris nudibranch (Gymnodoris rubropapulosa) seems to be in season today. I saw about 4 of them on this trip.
Orange-spotted gymnodoris nudibranch
Feathery gills
Other sea slugs seen on this trip includes two black phyllid nudibranch (Phyllidiella nigra) and a black-margined nudibranch (Glossodoris atromarginata)
Black phyllid nudibranch
Black-margined nudibranch
While checking out this reefy part of Semakau, I also looked at the beautiful corals closer to the reef edge. We were also on the look out for coral bleaching, as coral bleaching sightings have been noted on some corals at the nearby reef at Pulau Hantu. Here are some of the corals I saw on this trip.
Galaxy coral (Galaxea sp.)?
Favid coral
Torch anchor coral (Euphyllia glabrescens)?
Grooved brain coral?
Jigsaw maze favid coral
Branching montipora coral (Montipora sp.)
Grooved brain coral
Circular mushroom coral (Fungia sp.)
This marks the end of the morning intertidal trips as the tide takes a turn and the low tides transits to evenings. Also, tides in the fourth quarter of the year are not as low as we get during the pre-dawn trips, but that does not mean that we stop checking our shores.

We would probably be taking a slightly longer break before we resume our evening trips. So stay tuned!

Posts by others on this trip:
Kok Sheng - Reefy splendor of Northern Semakau
Ria - Pulau Semakau's reefy northern shore

Wednesday, August 21, 2013

Huge sea star and orange flatworm at Chek Jawa

Exactly one month ago,  a small team of us visited Chek Jawa for an intertidal survey trip. During that trip, we covered the Eastern and Northeastern part of Chek Jawa. You can read about my sightings from my earlier post about that trip.

Today we visited Chek Jawa again for another intertidal survey, but we started from the Southern side (in front of House No. 1) and worked our way towards the Chek Jawa front beacon.
Chek Jawa Front beacon
We started off by checking the pillars of the jetty in front of House No. 1 at Chek Jawa.
The first animals that I encounter was the striped hermit crab (Clibanarius infraspinatus). This hermit crab is very commonly seen on our shores and usually orange, but the one I saw was blue. Such colour is not commonly seen.
Striped hermit crab in blue
This looks like a the striped sand anemone. It is slightly retracted, showing only the tentacles with white bands.
Striped sand anemone?
This poor whelk has its shell surface almost fully occupied by a snail-hitching sea anemone.
Snail-hitching sea anemone on a whelk.
What kind of anemone is this? Hmm.... I am not able to identify this anemone. It has a dark coloured band that spreads across the width of the anemone.
Unknown anemone
On the pillar, there were a number of flying insects flying around and I managed to capture on that is resting on the pillar. It looks like some kind of fly.
Flying insect resting on the pillar.
Higher up the pillar, the lined nerite snail (Nerita articulata) leaves a trail of slime on the pillar surface where ever it moves. You cannot put the nerite snail back where you took from as the snail will retract into its shell when disturbed. This will cause the suction between the surface and snail to be cut off.
Line nerite snail
Can you spot the animal in this pictures?
Who and Where am I?
It is a juvenile purple climber crab (Metopograpsus sp.). Can you see it?
Purple climber crab
A poor fish swam too close to a haddon's carpet anemone (Stichodactyla haddoni) and got stung. The anemone them slowly pulls the stunned fish towards its oral disk. 
Carpet anemone caught a fish
The moving of the fish towards the anemone's oral disk was captured on video, but I had to abandon it due to the noisy and annoying mosquitoes pestering around me.

On other pillars, I spotted a blue-spotted flatworm (cf Pseudoceros indicus) on a group of ascidian looking animal. Could it be feeding on them?
Blue-spotted flatworm.
There were quite a number of sea fan or gorgonians towards the end of the jetty.
Sea fan
Candelabra sea fan (Euplexaura sp.)?
Gnarled sea fan (Echinomuricea pulchra)?
While checking out the sea fans, Mei Lin accidentally encountered a mangrove whipray (Himantura waiga) right in front of her foot and she froze on the spot for a short while. We were in about shin deep waters.
Mangrove whipray
There are plenty of biscuit sea stars (Goniodiscaster scaber) at Chek Jawa and they come in various sizes.
Biscuit sea star
Near the beacon, there are two knobbly sea stars (Protoreaster nodosus), though they looked kind of lonely together.
Knobbly sea stars
Along the way to the beacon, I came across a huge cake sea star (Anthenea aspera). This is the largest cake sea star I have seen. I have a photo of my size 8 bootie next to the sea star for size comparison.
Cake sea star
Comparison between sea star size and sponge.
Sea star size compared to my size 8 bootie
It's bigger than my hand!
Such a huge cake sea star makes photography of details a lot easier. Finally, I could get a good picture of the tiny bivalve pedicellariae on the underside of the cake sea star.
Tiny bivalve pedicellariae
Mei Lin spotted two little ruby flatworms (Phrikoceros baibaiye). It is very easy to miss this flatworm as they looked like orange melted sponge or ascidians. They are quite active and move rather fast, but not the fastest flatworm I had encounter. (*warning* The colour may be too striking for your eyes.)
Little ruby flatworm
Moving away quickly.
While heading to the Chek Jawa Front beacon, this poor smooth snapping shrimp (Alpheus sp.) was stranded on the sand.
Right side profile
Smooth snapping shrimp stranded on sand
Of course, I took the snapping shrimp and place it in a nearby shallow pool with a burrow. The shrimp was happy to be back in water and it went into the burrow quickly.
Smooth snapping shrimp in shallow pool.
I saw the red shrimp again at Chek Jawa in a vast patch of seagrass. However I did not observe the head in burrowing behaviour I saw yesterday at Pulau Sekudu.
Red shrimp hiding among seagrass and sea lettuce seaweed.
As we end the trip, a red ribbon worm emerges from its burrow and stayed stationary on the sand for what we would considered as a long period of time. It is usually very difficult to photograph this worm as they retract into their burrows at the slightest sense light or disturbance.
Red ribbon worm
My second intertidal survey trip to Chek Jawa is made possible with permission from NParks. Also not forgetting the crazy small group of us who woke up around 2 am on a working day for this trip.

Do not ask me how I did it or how manage to survive the work day because I have no clue how I manged it but somehow, I did and survived.

Posts by others on this trip:
Kok Sheng - A glimpse of the glorious beacon area at Chek Jawa
Mei Lin - Chek Jawa checkup - 21082013
Ria Tan - Alive at the Chek Jawa beacon

My past post on Chek Jawa intertidal:
My first Chek Jawa intertidal survey trip


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