17 December 2008

Pasir Ris health check

Pasir Ris Beach was graded unsuitable for swimming due to high bacteria levels, in July this year. How is the marine life doing there?Pasir Ris (which means 'sandy strip' in Malay) lies opposite Pulau Ubin and has many floating fish farms nearby. Pasir Gudang Port in Malaysia, Johor lies off its western end while our Loyang shipyards are to its eastern end.

I made a solo trip to this seemingly unpromising shore for the last super low tide of the year.On the high shore, a little row of young mangroves had taken root. But there were few mature mangrove trees fringing the shore. Unlike at Changi, the shores were deserted of people. There was only one family out on the soft mud, seriously searching for clams.The shore was very soft and very silty and covered with a bloom of Sea lettuce seaweed (Ulva sp.). But there were some extensive stretches with good growths of seagrasses!As far as I could see, there were only Spoon seagrasses (Halophila ovalis). But such lovely large fresh green ones they were! Very few leaf blades were gunked up with epiphytes.

As I didn't want to trample the seagrasses growing on this very soft shore, I stayed around the edges of the meadows.Among the first signs of life was a long-eyed Sentinel crab (Macrophthalmus sp.) that had just moulted. Crabs have a hard exoskeleton (external skeleton) and need to shed their shell in order to grow bigger. Called moulting, this also allows the crab to regenerate lost limbs.You can tell that the pale upper 'crab' is actually the empty moult because the eyes are transparent. And for the long-eyed crab, it is REALLY obviously transparent!Among the seagrasses was a tiny carpet anemones, and one peacock anemone.
There was also one uprooted Common sea pen (Pteroides sp.) with an orange 'root'. This creature is a colony of individual animals. Tiny animals that look like small sea anemones with a circle of tentacles are found in the leaf-like portion of the colony. In the shallow pools among the seagrasses were small wriggly eel-tail catfishes with whisker-like barbels near the mouth. Since this has barbels that extend beyond the eyes, it's probably a Black eel-tail catfish (Plotosus canius).
In the sandier portions near the meadows were lots of Ball sea cucumbers (Phyllophorus sp.). These are usually buried with only their tentacles sticking out of the ground to gather edible bits (photo on the left). But sometimes, at low tide, some are exposed above the ground (photo on the right). While I saw one purple sea cucumber, I didn't see the Thorny sea cucumbers (Colochirus quadrangularis) or Pink warty sea cucumbers (Cercodemas anceps) that are commonly seen on Changi and Pulau Ubin.There were also several sand collars, which are the egg mass of moon snails. The only moon snails I saw were Tiger moon snails (Natica tigrina) and I saw several of them.As the sun set, the stars came out. Sand stars (Astropecten sp.) that is. But these were not as abundant as I had seen them on previous trips.The soft silty shore is a great place for sea anemones. And I saw a small mangrove sea anemone, with a ring of 'petals' around its mouth. The striped blob next to it is perhaps one that is closed up.There were also several cowries. This is the Ovum cowrie (Cypraea ovum). This cowrie has a pear-shaped shell and its 'teeth' are tinged yellow or orange. It has no spots at the front end of the shell. Here's more on how to tell it apart from another similar cowrie.
It was a real delight was to encounter an Onyx cowrie (Cypraea onyx) too!

Here and there were patches of rocky areas among the seagrasses.Here strange sponges were seen. Most were low and encrusting, but some had grown long projections from the encrusting base. The stones also provided homes for lots of striped bead anemones and banded bead anemones.
Stones are a great place for laying eggs. This ribbon of eggs embedded in a jelly-like substance was probably laid by a nudibranch. So there must be nudis on this shore right?What a delight it was to encounter this Beaded nudibranch (Hoplodoris nodulosa). We've seen this in numbers on Pulau Sekudu but not commonly elsewhere. This nudibranch has spots on the underside.And in a little pool of water on a rock was this large slug-like creature. I gently touched it and it has a hard shell under that fleshy mantle, so it's probably a Hoof-shield limpet (Scutus sp.). I've not seen such a handsome one in a long while.

As the tide turned, I spent a really long time at a small pool on the high shore. It was teeming with tiny life!

While Pasir Ris is certainly not as spectacular as some other Northern shores, it is very much alive.

Alas, like many of our shores, Pasir Ris has a severe problem with litter.
Much of it seems to come from those who use the beach facilities. There were lots of food wrappers, drink bottles and beer bottles on the shore. There seemed to be less trampling of the shore compared to Changi. Possibly because it is very soft. But in some areas, almost every rock had been turned over and not replaced.

I didn't see this advisory at the beach.But according to the NEA website, "Currently, only Pasir Ris Beach is unsuitable for primary contact activities. Advisory signs (see above) have been erected along Pasir Ris Beach advising the public to refrain from swimming at the beach. NEA and PUB will continue to regularly monitor the water quality at the six recreational beaches and designated reservoirs respectively. Data collected will be used in the yearly review of the status of these sites."

Well, we too should regularly monitor our shores to see how they are doing.

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