14 January 2013

Quiet at East Coast Park

Teeming with sand dollars and countless Button snails, Wai and I check out a stretch of sandy shore at East Coast Park this evening.
But it was disturbing that we didn't see some common animals.

This stretch of sandy shore at the northern end of East Coast Park is quite large even at a not-so-low tide day like today.
Large areas of the sand bar is chock full of Button snails (Umbonium vestiarum). They leave tiny tell-tale depressions on the sand. And when we gently scrape away at the surface, we can immediately see countless snails. In some places, even footprints on the sand reveals the tiny snails just beneath the surface.
These Button snails are preyed upon by many other snails. It's easy to spot burrowing predators. Panicky Button snails leave trails on the sand as they literally leap to get away from them.
By gently digging in, we can find out what these predators are. Most of them I found were Ball moon snails (Polinices didyma). There were also lots of Spiral melongena (Pugilina cochlidium) and a few Drills (Family Muricidae) too! I only found one Olive snail (Family Olividae) today.
Another common snail on the shore today were these tiny Lined whelks (Nassarius teretiusculus?). These are probably scavengers and not predators. There were also many Tidal hermit crabs (Diogenes sp.) and some small Striped hermit crabs (Clibanarius infraspinatus). As well as lots of small to tiny Cake sand dollars (Arachnoides placenta).
Wai notices a bunch of tiny tubeworm tubes festooned with debris. It was hard to photograph the animals living in the tubes as they sporadically peeked out now and then.
The sand bar may appear empty and lifeless, but most of the animals are burrowed in the sand. I saw a few Peachia anemones (Peachia sp.) and Wai pointed out some Acorn worms (Class Enteropneusta). There were also a few signs of Sand bubbler crabs (Scopimera sp.).
On the rocks, I saw lots of seaweeds as well as some patches of a few kinds of sponges and some large oysters (Family Ostreidae). But the rocks were disconcertingly devoid of snails, sea slaters, limpets and crabs. We could hardly find any of these. Oh dear. I wonder why? The shore was not as lively as on our last trip here in Aug 2012.
But we did enjoy a dry cool evening and a lovely sunset.
It was nice spending time with Wai and we hope she will be back soon in Singapore again. Not too many low tides this time of the year so we get a break for a while until our next field trips.

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