29 May 2009

Lush seagrass meadows of Paris Ris

It's still low spring tide but not so early anymore. I thought I'd check out another part of the Pasir Ris shore.
In the first light of day, the receding tide reveals seagrass! Mostly very large and lush Spoon seagrasses (Halophila ovalis).

There's also lots of Sea lettuce seaweed (Ulva sp.) on the shores. Which is not necessarily a bad sign.Seaweeds are a source of food for all kinds of animals. And they also shelter small animals. Such as the tiny octopus in the photo above. Can you see it? This is why it's important not to step on seaweeds.
Here's what it looked like when it slithered out onto the soft mud. It looks like the kind of octopus we often see on Changi.

Seagrasses too provide shelter for all kinds of animals. And we really shouldn't step on seagrasses as they grow from underground stems. Just like our land grasses. If they are trampled they take a long time to recover.
This little fish was half hidden in the seagrass. I have no idea what it might be. When I tried to take a closer look, it slipped away into the soft silty mud. It might be the Brown-stripe wrasse (Halichores bicolor).

Teeming with life, the seagrass meadows are good hunting grounds for predators like the Spearer mantis shrimp (Harpiosquilla sp.).
This mantis shrimp was quite small, but very energetic. There were of course, lots of hermit crabs large and little all over the shores.

There were LOTS of large Olive whelks (Nassarius olivaceus) roaming the shores today.
Many in groups. Even following one another like these ones above. I've not seen this before. They don't seem to be gathering to feed. Perhaps to mate?

Other whelks were also out and about.
These Common whelks (Nassarius livescens) each has a tiny sea anemone hitching a ride on their shells!

Some parts of the shores without seagrasses had clusters of Zoned horned shell snails (Batillaria zonalis). But not in the huge numbers that we saw at Tanah Merah.
The bare soft silty sand were dotted with tiny Plain sand stars (Astropecten sp.). These nocturnal animals were starting to bury themselves for the day.
And I saw some Ball sea cucumbers (Phyllophorus sp.) as well as a rather sad purple sea cucumber.

The shores here are very VERY soft! After I had to crawl out twice on my knees, I stayed on firmer ground and didn't explore the full extent of the meadows. But soft shores are a great place for burrowing animals.This strange animal is a Spotted fanworm (Family Sabellidae)! You can clearly see the segmented body of this worm, which has a feathery fan on its head. The fan is collapsed when the worm is out of water. Submerged, the fan spreads out to filter edible bits from the water. The worm lives in a tube and is usually found on our Northern soft shores like Changi and Chek Jawa.

Burrowing cnidarians are also plentiful on this shore. There were lots of peacock anemones with their accompanying Phoronid worms. As well as burrowing sea anemones.
And here's a rather shy Mangrove sea anemone about to retract into the ground. So far, I've only seen these sea anemones at Sungei Buloh, Kranji and Pasir Ris.

Is there a mangrove nearby?
Yes there was! It's a delightful mangrove, though with very soft ground.

Soft ground doesn't bother tiny snails like the Red berry snails (Sphaerassiminea miniata). There were countless numbers of these snails covering the mudflats.
Nearer the trees were these Chut-chut snails (Cerithidea obtusa), another snail typical of our mangroves. One Malay name for this snail is 'Mata merah' which means 'red eyes'. The living snail does indeed have red eyes! And some have red bodies too.
Next to it were some small snails. I have no idea what they are and didn't really notice them until I processed the photo.

Futher in under the mangrove trees where its cool and dark were these special Cat's ear mangrove helmet snail (Cassidula aurisfelis). These air breathing snails are found in the back mangroves and not on the open sea shores.
The snail with the black mouth had a much thinner shell 'lip'. Could it be a juvenile, or it is another species? Hmmm.

But the best finds in these mangroves were Bruguiera hainesii and Kandelia candel! Here's more about them.

I was so excited about the mangrove tree I didn't bother to take photos of some of the special crabs that I saw there too. Well, another time.

On the sea shore, I met a happy guy with a HUGE fish.
He had just removed it from the super long drift net placed right across the mouth of the stream leading out of the mangrove. He is looking forward to eating it with his family.
He said he doesn't place the net often as it's a lot of hard work. He laments the catch is not as good at it was before. In addition to this fish, he also caught a large catfish. I asked and he said, yes, a lot of crabs too.

Alas, drift nets can cause massive death to marinelife. Especially if they are abandoned. Siva just wrote about how he spent five hours removing 300 horseshoe crabs from a driftnet at Mandai. Even if not abandoned, driftnets indiscriminately catch all kinds of marinelife, most of which are not wanted by the fisherman.

As I headed home, the tide was really low and the full expanse of the vast seagrass meadows were stretched out in a curve all along Pasir Ris.
What a fabulous shore it is!

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