24 May 2009

Tanah Merah: more surprises

I snuck out to have a quick look at Tanah Merah this morning for the super low tide.
Though I really ought not to be up at 2am. Since there's more of Envirofest 2009 today. But I couldn't resist finding out what's out there on the rest of the vast shores at Tanah Merah. And wow, there were yet more suprises as marinelife reclaims the 'reclaimed' land.

Unlike the stretch of shore visited earlier, this one was not uniformly covered for metres in tiny Batillaria zonalis (there were just small patches of these), nor in Dubious nerite snails (Clithon oulaniensis) (I didn't see any of these).

Instead, the shallow waters that covered large stretches of the sandy silty shores were teeming with penaeid prawns (Family Penaeidae). I have no idea why.
There were lots of the Blue tailed prawns and the Banded prawns, but all were rather small (not eating size) and most were half buried in the soft sand with only their beady eyes peeping out.

Other shrimps were tiny. But these form the food chain for other larger creatures, such as the fishes that fishermen like to catch. Besides lots of glass shrimps (Palaemon sp.), there were also many of these little red shrimps.
In the single Haddon's carpet anemone (Stichodactyla haddoni) was a pair of Anemone shrimps (Periclimenes brevicarpalis). Oddly enough, I didn't see any other anemones of any kind today.

I didn't see (or hear) many snapping shrimps (Family Alpheidae).
Those I did see where really tiny. But still, industriously excavating their burrows as all snapping shrimps incessantly do.

Another animal that was abundant on this shore is the Gong gong (Strombus canarium). Like the prawns, many of them seem young with a thin (rather than thick) flared 'lip' on the shell.
As I was observing this Gong gong with its eyes-on-stalks sticking out from under its shell, it also stretched out its siphon and started to vaccum the area around it. The siphon could really extend to quite a length. Wow, so this is how the snail feeds!

A most delightful snail to encounter were the Button snails (Umbonium vestiarum).
There were some patches of these snails on the less silty areas, and the snails were rather large and more spaced apart than those we've seen on other shores. These pretty snails are listed as 'Vulnerable' due to habitat loss.

In the soft sand was this strange thing. I don't think it's a weird sea anemone, although the long column topped with frilly bits suggests it might be one.
I think it's the siphon of a buried bivalve, extended to the surface to feed and breathe. Probably it belongs to a razor clam (Family Solenidae). Bivalves, especially the slim razor clam, are not only buried quite deeply but can also dig down EVEN deeper, and very quickly. So I know it's no point trying to dig it out to have a look.

It was nice to come across a few individuals of the Fan shell clam (Family Pinnidae) and the Window-pane clam (Placuna sp.)
These clams are usually only seen on good shores, especially those with seagrasses. Other clams seen included Venus clams (Family Veneridae), and a large cockle that I often see near reefs, whose identity I have yet to find out.

There was not much seagrass on this shore. I saw a very small patch of Spoon seagrass (Halophila ovalis) which unfortunately was badly overgrown with epiphytes. I had to smear off the sediment laden epiphytes to see the leaf blades.
And a few small clumps of Tape seagrass (Enhalus acoroides), also heavily overgrown with epiphytes.

But there were lots of very 'clean' and healthy looking seaweeds of all kinds on some parts of the shores. And large parts of the shores were covered in what seems to be scum but is probably some kind of cyanobacteria. All this is yummy food for animals such as slugs!
So it wasn't a big surprise to see some of the beautiful and appropriately named Extraordinary sea hare (Aplysia extraordinaria). Although available information suggests these slugs eat seagrasses ... hmmm. Either there's seagrass somewhere I haven't gone to yet on this shore, or these slugs eat something else as well.

Sea urchins also eat seaweeds.
And I saw one, and only one, White sea urchin (Salmacis sp.). Alas, I didn't see any other echinoderms and no Common sea stars (Archaster typicus) either.

Among the seaweeds, I saw this little flatworm (Order Polycladida) that I've not seen before.
Later on, Chay Hoon found another flatworm also among seaweeds.I've also never seen any flatworm like this before. Flatworms are carnivorous and not vegetarians. So they must be eating some kind of animal that grows among the seaweeds.

Some of the rocks and even seaweeds were covered in all kinds of encrusting animals, mostly ascidians (Class Ascidiacea).
These colourful slimy layers of animals are food for our favourite sightings! Nudibranchs!
And I did spot this little Denisoni's nudibranch (Dendrodoris denisoni) among the encrusted rubble. It was quite small for its kind, but had the usual bobbles and bright blue markings.

On the seawall, hard corals were growing! Of various kinds.
And lots of fishes were sheltering among these corals and rocks.
Like the tiny cardinalfishes under this bright blue hard coral. Here's more about the fishes I saw today.

The tough and hardy Zebra coral (Oulastrea crispata) (photo on the right) is quite common here.
There were small colonies of Pore corals (Porites sp.) (photo on the left). The white marks on this small colony are similar to the bite marks of fishes (like parrotfishes) that we sometimes see on larger colonies in the southern islands.

And I nearly missed this crab near the 'reefy' part of the rocks.
It's a well camouflaged Velcro or Decorator crab (Camposcia retusa). This crab sticks bits of encrusting organisms on its hairy body that acts like velcro for a perfect disguise.

Other crabs out and about include swimming crabs and lots of hermit crabs, including a Land hermit crab (Coenobita sp.) encountered on the way home on the high shore. There were also a lot of Long-horned ghost crabs (Ocypode ceratophthalmus) out and about on the shore.

This shore has been taken over by nature on the high shores as well.
Seashore morning glory (Ipomoea pes-caprae) carpets the ground right up to the high water mark, while trees grow behind them. Infront of them, a row of regularly spaced Ghost crab burrows.There were many young Rhu trees (Casuarina equisetifolia) on the shore, as well as some bushes of Sea lettuce (Scaevola taccada) and Sea hibiscus (Hibiscus tiliceaus) as well as some young Sea almond trees (Terminalia catappa). Unfortunately, there are lots of Acacia trees (Acacia auriculiformis) as well. Acacia is not native to our shores. And after learning more about the impact of alien species, I realise that without the Acacia, there might have been more of our native plants on this shore.

Alas, marine litter floats in with each high tide, leaving a line of debris on the high water mark along the entire shore.
There were several groups of people out on the shore today, with bright lights. Some were very loud and cheerful. At sunrise, they settled down to fishing on the incoming spring tide.

The shores here look like they are gradually building up towards nice reefs and seagrass meadows that we see in our Southern Islands and at places like Chek Jawa. The marvellous sightings does make worthwhile all the sandfly and mosquito bites, the bush-whacking and other travails to get to the shore.

More sightings during this trip by Chay Hoon on her colourful clouds blog.

3 comments:

  1. Wow, woke up at 2 am to check out this place. I salute your high level of enthusiasm. I have started to learn a bit of marine lives from your posts. Thanks.

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  2. Nice, I wish we had something like that over here in the Adriatic sea. Mostly rocky and cliff coast, though.

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  3. Thanks Federick. Actually, I enjoy working at night in the cool and dark. I am in awe of how you terrestrial explorers can keep going in the heat of the day!

    Thanks for dropping by romunov all the way from the Adriatic Sea. I love rocky shores and cliffs! I'm sure yours are quite spectacular. We have so few natural rocky shores and cliffs left in Singapore.

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