25 July 2013

Triple Terumbus for Giant Clams

This morning, I joined Mei Lin and her team of Clam Hunters to visit three submerged reefs! Our first stop, the beautiful submerged reef of Terumbu Raya, which lies just across from Pulau Semakau.
We found Giant clams! And also encountered sharks! Saw a sea turtle and sea snake too.

Rene first spotted the Fluted giant clam (Tridacna squamosa) on the left and gave Mei Lin the GPS coordinates. Kareen found it almost immediately. As we wandered back to the boat, Bokai found another one! Mei Lin is intrigued by these two clams. They are about the same size so are they same age? We didn't spot them until recently, did we just miss them? Or did they just recently 'appear'? If so, where have they been 'hiding' previously?
Here we are admiring the clam that Bokai found.
I was delighted to see a Tiger cowrie (Cypraea tigris) at Terumbu Raya!
Other interesting animals seen included one Knobbly sea stars (Protoreaster nodosus), a Fire anemone (Actinodendron sp.), a Durian sea cucumber (Stichopus horrens), a pair of octopuses.
I took the opportunity to check the small area of the reef that we visited for coral bleaching. Only a few colonies were bleaching, of various different species. I only saw a few small leathery soft corals (Family Alcyoniidae), but they all looked healthy.
I saw a few colonies of Crinkled sandpaper coral (Psammocora sp.) and Cauliflower coral (Pocillopora sp.). None of them were bleaching. These kinds of corals were among the first to bleach during the 2010 global mass bleaching event.
There is quite a good variety of hard corals on Terumbu Raya. Most of they looked alright or just a little pale: Lettuce coral (Pavona sp.), Carnation coral (Pectinia sp.), Brain corals (Family Mussidae).
Here's more corals seen:  Montipora corals (Montipora sp.), Ridged plate coral (Merulina sp.), Galaxy coral (Galaxea sp.).
Some of the colonies were large (more than 50cm in diameter), most of these were Pore hard corals (Porites sp.). There were also many Favid corals (Family Faviidae).Those I saw seemed alright without any signs of bleaching.

There were scattered clusters of Spoon seagrasses (Halophila ovalis) and Tape seagrass (Enhalus acoroides). Some of the Tape seagrasses were of moderate length. But all the seagrasses were heavily covered in epiphytes.
In some places, the seagrasses were also thickly coated with some kind of growth.
Elsewhere on the reef, the Tape seagrasses were cropped short and sticking upright.
We have seen fishermen laying nets and traps on this submerged reef. Today we didn't see any and only came across this flattened trap.
The situation on Terumbu Raya doesn't seem very different from the last time I checked out the same stretch a year ago in July 2012.

After searching a very small portion of the huge Terumbu Raya, we then hopped over to Terumbu Bemban to look for another Giant clam that Rene also found there earlier.
Sadly, though we searched all around the GPS coordinates, we couldn't find the clam or any other clams.
There were a few patches of pale leathery soft corals (Family Alcyoniidae) (as in the above photo). But most of the leathery corals I saw seemed alright with only a few colonies that were yellowish or pale.
There were a few small colonies of Acropora corals (Acropora sp.) and Montipora corals (Montipora sp.). They were not bleaching.
 I saw a few colonies of Crinkled sandpaper coral (Psammocora sp.) and Cauliflower coral (Pocillopora sp.). None of them were bleaching. These kinds of corals were among the first to bleach during the 2010 global mass bleaching event.
 There were also different kinds of corals and most of them seemed alright or just a little pale. Anemone corals (Goniopora sp.), Disk corals (Turbinaria sp.),  Brain corals (Family Mussidae), Pebble coral (Astreopora sp.).
There were many Pore hard corals (Porites sp.) and Favid corals (Family Faviidae). Those I saw seemed alright without any signs of bleaching.
 There were only a few colonies that showed small patches of bleaching or were rather pale or pink.
There were scattered clusters of Spoon seagrasses (Halophila ovalis) and Tape seagrass (Enhalus acoroides). Some of the Tape seagrasses were of moderate length. But all the seagrasses were heavily covered in epiphytes.
I did see a few clumps of longer Tape seagrasses.
We arrived at Terumbu Bemban late so the tide turned soon. Bringing in many sharks! We also spotted a sea turtle briefly, and terns swooping down into the shallow water to catch fishes. Bokai also spotted a Yellow-lipped sea krait (Laticauda colubrina). My last trip to Terumbu Bemban was in Mar 2013.

On the way home, we stopped by at Pulau Jong to try to have a look at the clam there. The tide was high and rising but the little sand bar was still exposed.
So we all made a quick landing. But alas, we failed to find the clam.
I last saw the clam in  Apr 2013. Hopefully, it's still alright and we just 'lost' it in the deep water and heavy growths of Bryopsis seaweed.
Next to Pulau Jong, there were many large ships and working vessels, probably involved in the ongoing work to replace the SBM pipeline there.
Shell briefed me and other interested groups about this plan in Sep 2012. Basically, Shell plans to remove and replace a 2km portion of the SBM pipeline (in red) that leads from the SBM off Pulau Sebarok to Pulau Bukom. As dredging is involved to prepare the ground for the pipeline, sediment plumes may form. More about what is sedimentation and why does it matter.
Click on image for larger view.
The bleaching at Terumbu Raya and Terumbu Bemban did not seem as bad as the bleaching we saw at Terumbu Hantu on 28 Jun 2013. Although according to NOAA’s Coral Reef Watch which gives predictions of global coral bleaching, the global situation seems to have worsened in July compared to June. More about the possibility of mass coral bleaching in 2013 on the Bleach Watch Singapore blog.
Situation on 22 July 2013
Situation on 27 Jun 2013
Thanks to Mei Lin and her team for letting me come along to see our submerged reefs are doing. And to share in the many interesting encounters on this very busy trip! I joked that we treated Alex's boat more like a shuttle bus today, making so many stops.

Tomorrow, field trips continue and I'm heading back to our Northern shores.

Mei Lin blogs her thoughts about the Giant clams we've been seeing: "What is mostly intriguing for me is the large number of clams of ~14-16cm shell length found on our shores! Questions swirling in my head - How old are they? Where could they come from? Who are their 'parents'? What is their distribution on the maps? How many recruitment events have taken place? Oh my! This opens a new can of worms and I can't wait to start work on them!"

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