25 December 2010

A merry reef on Sisters Island

Have the reefs at Sisters Island survived coral bleaching? A small team headed out on Christmas Eve for a very short low tide. We were delighted to see a lively reef with many healthy corals!
I almost missed this squadron of squids (Family Loliginidae)! They stayed so still and looked just like seaweeds at first glance.



But suddenly, they all zoomed away. Leaving behind coagulated ink blobs that look very much like squid! In this way, predators can be distracted. Apparently, the ink also contains substances that deadens the predators senses so they can't 'smell' where the squids went. Wow. Here's a very bad clip of the squids inking, as they caught me by surprise too! (The sound is from the very strong wind blowing at the time).

The shores are crawling with Reef octopuses of all sizes! They are superbly camouflaged and hard to spot until they move. The rest of the team came across a pair of mating octopuses!
The only slug I saw was this Ornate leaf slug (Elysia ornata). None of us saw any nudibranchs. And only James saw flatworms. Oh dear.
On the sandy area I came across a Large cockle with its 'tentacles' sticking out between the valves, and a living Gong-gong snail (Strombus turturella).
I had hoped to find the Fluted giant clam (Tridacna squamosa) that I had seen many years ago. I failed to find it, and instead, saw the shell of a dead large one (about 30cm long). None of us also saw the small one that was seen in the lagoon in past trips.
Always a delight to encounter, the gorgeous Saron shrimp (Family Hippolytidae)! This one wasn't as shy as they usually are and allowed both me and Kok Sheng to take photos of it. There were also many swimming crabs (Family Portunidae) of all kinds out on the shore, as well as Floral egg crabs (Atergatis floridus) and Red egg crabs (Atergatis integerrimus).
Many ghost crabs (Ocypode cerathophthalmus) were skittering about on the shore. This one stayed quite still as it was having dinner. On another crab!
Here's a clip of the Ghost crab delicately picking away at its meal. Yumm.
I saw a pair of Spider conch shells near one another, and both turned out to be occupied by Very hairy hermit crab. These have been kindly identified by liwaliw as Dardanus lagopodes.

Now that I managed to get a closer look at it, the hermit crab is actually quite colourful!
On the high shore and even on the grassy areas, there were lots of Land hermit crabs (Coenobita sp.)! These animals shelter and feed on the debris washed up on the high shore. They are rare on our mainland shores because our recreational beaches are so thoroughly cleaned every day.
I saw a gianormous Common sea stars (Archaster typicus) in the sandy lagoon. I also saw several Black long sea cucumbers (Holothuria leucospilota), while the rest of the team saw some other intriguing sea cucumbers. There were also many brittlestars on the sandy areas, but they all retracted their arms rapidly when my torchlight falls on them.

It was a relief to see that the corals are doing quite well. There were many large and small healthy corals, in some parts jammed very close to one another. Kok Sheng has lovely photos of these. There are only a few corals that are still bleached or showing some signs of disease or producing slime.
As usual, the most abundant hard coral species were Favid corals (Family Faviidae) and Pore hard corals (Porites sp.).
I saw healthy individual colonies of less common hard corals such as Brain corals (Family Mussidae), Carnation corals (Pectinia sp.), Ridged plate coral (Merulina sp.), a nice large Disk coral (Turbinaria sp.), there were many Circular mushroom corals (Family Fungiidae large and small, and Anemone coral (Goniopora sp.).
It was particularly good to see living specimens of hard corals that were badly affected by coral bleaching: such as Cauliflower corals (Pocillopora sp. and Sandpaper coral (Psammocora sp.). Kok Sheng found lots of little animals hiding in Sandpaper coral that he saw.
There were also several healthy branching Montipora corals (Montipora sp.). Unlike at my last trip in September, I didn't come across any Acropora corals (Acropora sp.). I did see one small colony of Galaxy corals (Galaxea sp.). Rene saw a nice big colony of healthy Anchor corals (Family Euphyllidae).
I saw a few small coral colonies that were still pale or bleaching, and a few that were producing slime. Some of the large Pore corals (Porities sp.) also had bluish or discoloured patches suggesting disease, but no longer as extensive as what I saw in July.
I also saw many healthy corallimorphs (Order Corallimorpharia), which are usually abundant on this shore. I also saw a large colony of unbleached Button zoanthids (Zoanthus sp.).
The upper shore seems less sandy than usual to me. As if the sand had 'moved' leaving behind a larger area of rubble. But there are still sandy silty stretches and here I found one Haddon's carpet anemone (Stichodactyla haddoni) with a pair of anemone shrimps.
Frilly anemones (Phymanthus sp.) were abundant and none I saw were bleached. Peachia anemones (Peachia sp.) were also still present on the sandy area.
I also saw several healthy leathery soft corals (Family Alcyoniidae).
There were also lots of fishes on the reefs! They are in a separate post.

We ended this special holiday trip with a treat of Christmas mince pies from Tang Ling and Wee Hock and curry puffs from Andy! Thank you!
It's a relief to see the reefs of Sisters Island doing well. Particularly after a desolate trip the day before to Sentosa's natural shores. We need to check up on all the shores next year to see how they are recovering from coral bleaching.

More about this trip on blog posts by:
  • Kok Sheng with lovely photos of colourful corals and more
  • James with lots of great photos of really tiny creatures
  • Rene on facebook with some interesting coral sightings
  • Marcus on facebook with octopus mating and on his blog
  • Nicole on facebook and on her blog
  • Andy with video clip of gianormous decorator crab

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