22 January 2011

How is coral bleaching at Pulau Hantu?

It's always a delight to see 'Nemo' or the clown anemonefishes on our shores!
And at Pulau Hantu, we have a pretty good chance of seeing them even at low tide. The False clown anemonefishes (Amphiprion ocellaris) on our shores live in the Giant carpet anemones (Stichodactyla gigantea).

The anemones usually have more than one clownfish! Today, the water was quite high. Which is not very good for looking at other marinelife, but this means the clown anemonefishes were in water and out and about, playing among the tentacles of the anemone, instead of hiding away from view.
Here's a rather bad video clip I took of the anemonefishes.

One of the purposes of this trip was to check on the mangroves that grew naturally on the seawall. The other was to check on the coral bleaching situation. Coral bleaching has been happening throughout the globe since last year. Mainly due to higher sea surface temperatures. Just a few days ago, Thailand shut down 18 major dive sites due to coral bleaching.

On Pulau Hantu today, it was a relief to see many large hard corals that were not bleached.
There were also many small hard corals looking well. This cluster is growing in the middle of the 'bald' patch of a larger hard coral. Compared to our most recent trip in July last year, I didn't see any bleaching corals. My sense during this trip, though, is that there are fewer corals than usual. Suggesting that perhaps not all the Hantu corals survived the bleaching. But the tide wasn't very low and much of the reefs were covered in a thick growth of Sargassum seaweed (Sargassum sp.) so we couldn't explore much of the reef.
There were many brightly coloured and healthy Favid corals (Family Faviidae) both large and small.
I saw a few small unbleached colonies of Anemone coral (Goniopora sp.), one small colony of Disk coral (Turbinaria sp.), many Pore corals (Porites sp.) branching and boulder, and something that might be a Brain coral (Family Mussidae). I saw one Sunflower mushroom coral (Heliofungia actiniformis) but didn't see any Circular mushroom corals (Family Fungidae).
There were quite a few healthy and happy Galaxy corals (Galaxea sp.). There seems to be different kinds of Galaxy corals on Pulau Hantu. Kok Sheng checked out the 'meadow' of Galaxy corals that we used to see before the bleaching incident and he says they seem alright.
While I saw several branching Montipora coral (Montipora sp.), I didn't see any living Acropora coral (Acropora sp.). I also didn't see any dead or living Cauliflower corals (Pocillopora sp.), Sandpaper coral (Psammocora sp.) or Anchor corals (Family Euphyllidae). But Kok Sheng saw some of these and more.
Branching corals are homes to many different animals, among them the very cute Machine gun shrimps (Coralliocaris graminea). This healthy branching Montipora coral had at least three of them! But they are very hard to photograph. Like the snapping shrimps (Family Alpheidae), the pincer of the Machine gun shrimp has an enlarged tooth and a special catch. When the catch is released, the tooth makes a loud snapping sound. Unlike the snapping shrimp which only has one such 'snapping' pincer, the Machine gun shrimp has two such pincers, hence its common name.
The only crabs I came across were Flower crabs (Portunus pelagicus) small and large, as well as other kinds of Swimming crabs (Family Portunidae). But the rest of the team saw many different kinds of crabs.
On the narrow shore facing Pulau Bukom, the large leathery soft corals (Family Alcyoniidae) there seem alright. Although they appear much smaller than usual.
There were also several (but not very many) leathery soft corals and flowery soft corals. I didn't see any Asparagus flowery soft corals (Family Nephtheidae) though.
Not too many snail sightings on the reefs, although there were lots of snails on the seawall. A well camouflaged Spotted top shell snail (Trochus maculatus) grazing on seagrass, and a pair of Cat's ear pyramid snails (Otopleura auriscati) which seem to be mating? Kok Sheng checked on and found the Burrowing giant clam (Tridacna crocea) to be alive and well. Hurray!
The only nudibranch I saw today was a very large Discodoris boholiensis. But the rest of the team saw some other slugs too.
Pulau Hantu has a good population of Common sea stars (Archaster typicus). And here's some sea stars working on maintaining that population, entwined in mating position. I noticed several individuals that were smaller than usual, and saw small ones on top of big ones, as well as small ones on top of small ones.
On the reefs, I saw two very large White-rumped sea cucumbers (Actinopyga lecanora). Kok Sheng spotted some feather stars!
There were many large living healthy sponges, although some of the Yellow prickly branching sponges (Pseudoceratina purpurea) had bluish tips. There was a large thick pink sponge (Callyspongia diffusa), lots of bright Orange sprawling sponges (Clathria reinwardti), some dotted with hairy olive sponges and many clusters of bright green tangled sponge.
These odd slits embedded in different kinds of sponges I think are some kind of clam. I'll have to read up about this. There's always MORE to learn about our shores!
There were all kinds of fanworms (Family Sabellidae) on the shore too. The rest of the team saw some flatworms too.
Alas, there are signs on irresponsible fishing on the shore.
An abandoned crab trap near the big mangrove trees on the high shore.
There was an abandoned driftnet but it was so old that is now encrusted with marine life and has become a part of the ecosystem. So we left it there.
We also bumped into some bio students doing fieldwork on Pulau Hantu. It's good to know that our shores are being studied as there's so much to learn and do for them.

Earlier on, I had a quick look at the mangroves growing on the seawalls at Pulau Hantu.

More about coral bleaching on Bleach Watch Singapore.

Other posts about this trip
  • Andy with a video clip of an octopus on the run and MORE video clips
  • Kok Sheng with corals, crabs, nudis and more!
  • James with corals, tiny flatworms, slugs and more!
  • Russel lots of landscape photos, colourful corals and horseshoe crab!
  • Rene on facebook with seahorse!
  • Nicole with wriggly star anemone.

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