08 November 2009

Clams and 'nems on Pulau Hantu

Finally I feel somewhat useful and found the Burrowing giant clam (Tridacna crocea) that lives on Pulau Hantu!
Mei Lin is back with us on the shore for her Giant clam survey. I first saw this clam in 2006!

Here's what it looks like when it's submerged in water. Isn't it pretty. I'm so glad it's still there!
Burrowing giant clam (Tridacna crocea)
Another surprise find were lots and lots of these tiny sea anemones. They look like the wriggly star anemone but have different markings. And while the wriggly star anemones are found in deeper water among coral rubble and living corals, the ones we saw last night were on higher shores in sand.
Could this be the Edwardsia hantuensis that Dr Daphne was looking for? This sea anemone was first described by England in 1987 from specimens taken at Pulau Hantu. Wow! A sea anemone named after our very own Pulau Hantu!

We only saw this sea anemone and many other creatures on the high shores of Pulau Hantu because the tide was once again non-compliant. But it was a great excuse to look more closely at the high shores that we so often skip as we head straight out for the reefs. As we waited, the sun set and more animals came out as it got dark.

Besides the strange new anemones, there was also a little anemone on a living snail.
And many large Shy glass peacock anemones. These have transparent tentacles that shrivel up and retract quickly when a torch or camera flash is detected.
I also noticed this delicate fan worm that doesn't look like those I've seen before.
There were lots of other sand dwellers too. Like this large snapping shrimp (Family Alpheidae).
While the pools on the flat sandy areas were teeming with gobies (Family Gobiidae). This one has a bright blue mark on the dorsal fin. I have no idea what it is.
While there were many of these speckled gobies. Yet another mystery to me.
Here and there were Gold-spotted mudskippers (Periophthalmus chrysospilos). This one is particularly handsome with bright orange spots.
Also, very small flatheads (Family Platycephalidae). Most of the sand-dwelling fishes are well camouflaged. So it's important to look closely. They are also more active at night, staying well hidden the day.
There were lots and lots of Common sea stars (Archaster typicus) all over the shores. In all kinds of patterns and sizes. I had earlier thought that the smaller sea stars were juveniles. But it looks like they might be mature males. Males usually lock arms on top of females to prepare for simultaneous release of eggs and sperm. This much smaller male could hardly get his arms around the much bigger female. Poor thing.
And what a tantalizing find! The skeleton of a Laganum sand dollar (Laganum depressum) which is quite rarely seen! Alas, I couldn't find any living ones, of any kind of sand dollar.
Finally, the tide started to turn, and I snuck out to the reef edge. Along the way, I had a look at the Tape seagrasses (Enhalus acoroides) that grow in the lagoon. There were lots and lots of these tiny, nearly transparent slugs!
These might be some sort of sea hare (Order Anaspidea)! Because it has two pairs of tentacles on the head, one pair in front (called oral tentacles), and another pair (rhinophores) on the head, behind the two tiny black dots (possibly some sort of eyes?). See Dr Bill Rudman's fact sheets here and here and here.

The rest of the team also found lots of strange creatures on the seagrasses, including a basket star! See their blogs for more photos and stories (links below).

As I got to the reef flats, it was nice to see that the corals were still doing well. Here's a nice cauliflower coral (Pocillopora sp.) with many banded fan worms.
And a nice colony of Acropora hard corals with a mushroom coral behind it in the fast flowing water.
In fact, the mushroom corals (Family Fungiidae) in this spot seem to have grown bigger.
There were also lots of flowery soft corals and leathery soft corals.
It was also nice to see that the Magnificent sea anemone (Heteractis magnifica) is doing well. Alas, it didn't seem to have any animals resident at the time. But the rest of the team saw a Giant carpet anemone (Stichodactyla gigantea) with anemonefishes in it. That's good to know!And I saw these strange anemones all over the coral rubble. Somewhat similar to the ones we saw at Pulau Semakau the day before.
The reef flat was covered with a floating carpet of Sargassum seaweeds (Sargassum sp.). It's important to avoid such areas and step only on bare sand. I saw this Blue-spotted fantail ray (Taeniura lymma) slip out from under the seaweed before disappearing with the flowing water.
This is why it's important to be careful out on the shore. Fortunately, there were no mishaps yesterday and everyone had a great time without damaging themselves or the shores.

Pulau Hantu lies just next to Pulau Bukom, the location of Shell's largest refinery in the world (from the Shell website). A major extension to Shell's installations, built by burying the reefs of Terumbu Bayan, is slated to launch next year. I took this photo sometime ago. I was too excited by the shores to take one yesterday.
Pulau Bukom lies just off the rich reefs of Pulau Hantu
Dredging also seems to be going on all the time off the western side of Pulau Hantu.
Despite this, the reefs of Pulau Hantu remains very much alive. Both on the intertidal as well and underwater. Volunteers of the Hantu Bloggers conduct regular dives at the reefs of Hantu. Check out their blog for the latest photos and upcoming dive dates.

More about Pulau Hantu on the wildsingapore website.

Other posts about this trip

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