27 June 2010

Bleaching at Pulau Hantu

Bleaching leathery soft corals are very obvious on the living reefs of Pulau Hantu that lie just opposite the industrial installations on Pulau Bukom.
It was disconcerting to see for the first time, bleaching in some kinds of animals that we have not seen before.

For the first time since we started checking for bleaching in late May, we saw bleaching colonial anemones or zoanthids (Order Zoanthidea)! Here's a patch (bluish blobs) that are bleaching, near hard corals that are alright.
Some of the Button zoanthids (Zoanthus sp.) were bleaching, and also the Broad zoanthids (Palythoa mutuki). In fact, the zoanthids on the shore seemed to be much less numerous than on our previous trips. Perhaps some have already died?
Most of the Sea mat zoanthids (Palythoa tuberculosa) that I saw were bleached or bleaching.
Another first, the corallimorphs (Order Corallimorpharia) were bleaching! I saw bleaching in all the varieties commonly seen on Pulau Hantu: frilled corallimorphs, carpet corallimorphs, ridged corallimorphs. About 50% of the corallimorphs I saw had some signs of bleaching. Those with signs of bleaching seemed more sparse, perhaps some of the individuals had already died?
Yet another curious sighting. I saw this bleaching Favid coral with odd bulbous polyps here and there. I'm not sure what is happening. I tried to read up about 'polyp bailout' where polyps literally leave their colony when things get bad. But it seems it is not a widely accepted that this phenomenon occurs.
Also a new development, more bleached sea anemones are seen today. Almost all the Frilly sea anemones (Phymanthus sp.) I saw were bleached, and about half the large Giant carpet anemones (Stichodactyla gigantea) were not looking good. I saw a Pizza anemone (Cryptodendrum adhaesivum) but only because it was bleached. The Magnificent sea anemone (Heteractis magnifica) seemed alright.
Giant carpet anemone are homes to animals such as the adorable False clown anemonefish (Amphiprion ocellaris). I saw only one anemone with fish. The bleached anemones did not seem to have any fish.
It was only because the flowery soft coral was bleached, that I noticed the tiny little filefish that was hiding among the 'branches'. Bleaching probably makes such animals more visible to predators.
Aside from the above special sightings, the bleaching on Pulau Hantu seems similar to those we have seen recently on other shores. Many of the leathery soft corals (Family Alcyoniidae) were bleaching. While many hard corals were bleached or starting to bleach too.
Surprisingly, the humungous leathery soft corals at the mid water mark have not turned completely white.
But there are lots of yellowish streaks on these usually brownish beige animals.
The hard corals of all kinds were bleaching. Here's various corals showing bleached and unbleached colonies next to one another.
There is a large patch of galaxy corals (Galaxea sp.) here. The colonies in the patch seemed a little off colour and a few of the polyps were bleaching.Unfortunately, many of the Circular mushroom corals (Family Fungiidae) were bleached completely white. Here's some among the patch of Galaxy coral.
While many of the Circular mushroom corals were pinkish or completely white, some with parts that are already dead and covered with scum or seaweeds, there were still many that were alright.
I saw one bleaching Mole mushroom coral (Polyphyllia talpina), one bleaching and half dead Bracket mushroom coral. But the Sunflower mushroom corals (Heliofungia actiniformis) seemed alright.
Fortunately most of the other kinds of mushroom corals seem to be still alright. Here are two blue Tongue mushroom corals (Herpolitha sp.) and one large long mushroom coral.
Not all hard and soft corals were bleached. We estimate about 60-70% were bleached. Even among the species that suffered the most bleaching, I saw some unbleached colonies: such as one Cauliflower coral (Pocillopora sp.) colony, several Sandpaper corals (Psammocora sp.) and one Disk coral (Turbinaria sp.).
Near the mouth of the lagoon, I saw some unbleached soft corals!
As we have seen elsewhere recently, this branching Montipora coral (Montipora sp.) that grows on the high shore and is often exposed does not seem to be bleached.
Many of the Pore hard corals (Porites sp.) seemed alright. Even very large colonies.
As we have seen elsewhere, the Blue corals (Heliopora coerulea) seem alright. And we checked our Burrowing giant clam (Tridacna crocea) and it's still alright too.
This shore has many fishes. Some I saw include the Carpet eel-blenny (Congrogadus subducens), Fan-bellied filefish (Monacanthus chinensis) and a little dark fish that might be a cardinalfish and the Orbicular cardinalfish (Sphaeramia orbicularis). There were also lots of gobies in shallow waters. While throughout the trip, in deeper water there was a great deal of splashing around.
I saw many Spoon-pincer crabs (Leptodius sp.) including this mis-matched pair that seem to be in mating position. And a Mosaic reef crab (Lophozozymus pictor). There were lots of swimming crabs (Family Portunidae) of all kinds too. But as Ivan noted, we didn't see any Egg crabs (Atergatis sp.) today.
I only saw two small octopuses. But these masters of disguise are hard to spot! So maybe there were more and I overlooked them.
The sponges are still present in their usual bright colours.
We didn't notice any flaring at Pulau Bukom's petrochemical plant as we arrived before dawn. But as we were walking to the shore, we heard the signature 'jet-engine' sound of flaring. So we were very surprised to see that the flare was burning blue and clear without producing much smoke. Somewhat like an acetylene torch used for welding. This is very different from our last night trip to Pulau Hantu. It's good if they do a more complete burn with less smoke and unburnt chemicals released into the sky and waters.
Today, the Hantu Bloggers are also diving Pulau Hantu. So we shall soon hear from them about the bleaching situation deeper on this marvellous reef.

Chay Hoon and her team from Blue Water Volunteers' ReefFriends also conducted a reef check of Hantu and has a depressing report on her blog.

Let's hope for the best for this marvellous reef that is so loved by divers and non-divers alike. More about bleaching on Bleach Watch Singapore.

More photos of Pulau Hantu's intertidal marinelife.

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