02 May 2010

The other side of Terumbu Raya

Dawn sees us once again, out at sea. We're heading for Terumbu Raya, a submerged reef off Pulau Semaku, towing the trusty dinghy behind us for our amphibious landing.

Terumbu Raya is has a good reefy portion facing Pulau Semakau (the forested area in the photo are the mangroves on Semakau). While the rest of the team explore this part and to find the fabled Giant clams, I head off to do the other side of the reef.
One of the first things I saw was this awesome slug. It was huge (about 15cm long)! It is Forskal's sidegill slug (Pleurobranchus forskalii) which has also been sighted at Cyrene, Tanah Merah and elsewhere. Although it is not known what this species eats, other species of Pleurobranchus are reported to feed on ascidians. An interesting fact is that chitinous plates identified as the jaw plates of this sea slug had been found in the stomach of a sea turtle.
As usual, I gently take a photo of the underside for identification. Just that brief handling resulted in some kind of icky slime on my fingers that felt a little acidic. The slime was really hard to get rid off. I'm sure this slime keeps most molesters away from the slug, except for hungry sea turtles.
Aside from this, the only other slug I saw was a Jorunna funebris. Chay Hoon, the Mollusc Mistress of course saw a lot more.

The tide was still a little high when we arrive and it's important to watch where we step. Besides the dreaded Mr Stonefish, there are also lots of Blue-spotted stingrays (Taenura lymma)! With their blue spots on a brown body, they are actually hard to see on sand under ripply water. And the rest of the team said they saw some buried in the sand as well. Wow. It's a good thing no one got hurt today.
There were lots of other fishes zooming about in the water, too fast to photograph. But I did manage photos of these: A little electric blue fishie which might be a juvenile Three-spot damselfish (Pomacentrus tripunctatus), a small Copperband butterflyfish (Chelmon rostratus) and there were many many Carpet eel-blennies (Congrogadus subducens).
In the end, I managed to walk the edge of the reef to meet up with the rest of the team. Alas, the rest of Terumbu Raya isn't as fabulously thick with life as the stretch facing Pulau Semakau.
While there are hard and soft corals here, they are rather sparsely distributed. Nevertheless, I came across more Mushroom corals (Family Fungiidae) here than I usually do at Pulau Semakau.
In fact, today I saw most of the common kinds of mushroom corals: Circular mushroom corals and Smooth mushroom corals. Although I didn't see any Sunflower mushroom corals (Heliofungia actiniformis) which are common Pulau Semakau.
As well as the long mushroom corals: Mole mushroom coral (Polyphyllia talpina), a very long Tongue mushroom coral (Herpolitha sp.) - it must have been about 40cm long!, and several Long mushroom corals.
I saw many of the commonly encountered hard corals: Many brain corals (Family Mussidae), some crinkly sandpaper coral (Psammocora sp.), Cauliflower coral (Pocillopora sp.), many Anemone corals (Goniopora sp.), Galaxy coral (Galaxea sp.), many encrusting disk coral (Turbinaria sp.) and flowery disk corals (Turbinaria sp.) and many different kinds of Favid corals (Family Faviidae) as well as many Pore corals (Porites sp.).
As well as some special hard corals too: Acropora coral (Acropora sp.), Pebble coral (Astreopora sp.), Lettuce coral (Pavona sp.), a large colony of Trumpet coral (Caulastrea sp.), possibly the Torch anchor coral (Euphyllia ancora), and Carnation coral (Pectinia sp.).
There were also these special corals: The cup-shaped bracket mushroom coral and the rare Ringed plate coral (Pachyseris sp.)
I was also delighted to see these seaweeds: the Green sea sausage seaweed (Bornatella sp.) is sometimes reddish. While I saw these fat finger-like seaweeds with bumps (Chrondophycus sp.).
Strangely, I didn't come across any other anemones aside from several Wriggly star anemones, and some Frilly sea anemones (Phymanthus sp.).
The rest of the team had lots of marvellous findings! Kok Sheng pratically went diving to take underwater photos of the reef. They found a Tiger cowrie, both the Burrowing giant clam (Tridacna crocea) and Fluted giant clam (Tridacna squamosa) as well as a recently dead Hippopus hippopus, a giant clam thought to be extinct in Singapore. And many other hard corals, anemones and more! See links to their blog posts below.

Seagrasses are very patchy on Terumbu Raya, without large meadows like those found on Semakau. Today, I noticed lots of Tape seagrass (Enhalus acoroides), Serrated ribbon seagrass (Cymodocea serrulata), some Spoon seagrass (Halophila ovalis) and Needle seagrass (Halodule sp.)
Alas, I also came across some large fish traps laid out on the reef. The rest of the team also saw some of these traps on the portion of the shore that they checked out. But fortunately, no drift nets.
Sadly, there were also these plastic tubing and rolls of chicken wire on the reef edge. I'm not sure what this is about.
As we were getting ready to go home, I noticed this Grey heron feeding on the reef edge. Behind it, the seawalls of Pulau Hantu and the petrochemical plants on Pulau Bukom. The area off Terumbu Raya is also a designated mooring site for some kinds of ships. We have seen barges parked here too. And on the way to the reef, we went through a diesel spill.
Terumbu Raya means 'Great Submerged Reef'. Indeed it is great. I hope it remains well as we probably won't be visiting it for some time. There are too many other reefs to explore and too few low spring tides to do them as often as we would like to!

Other posts about this trip

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