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

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