A point in Changi

With Dr. James Reimer and his entourage from the Raffles Museum of Biodiversity Research, we went to a lesser known shore early this morning. This stretch of Changi below the boardwalk near the sailing club is new to me and offers a quite different habitat from the Southern Islands and their reef-lined shores.

Here, a narrow strip of coarse sand and gravel separates the coastal vegetation from the water but rapidly succumbs to a muck of soft silt and scattered rocks. On such days, when the tide retreats with unusual strength, the creatures that carve trophic niches for themselves on the outcrops lie exposed in visible layers of life. Barnacles and periwinkles cluster near the top of piles and boulders, just below a near invisible line that receives the sea spray but is never, if ever, submerged. Drills, limpets and mussels cluster in the middle zone, the latter's shells glistening with shiny blue and green where the surface has not been overtaken by barnacles and other filter feeders. Hanging via byssal threads that secure their base to the vertical pillars, the mussels form aggregations so thick that some seem barely able to open their shells to feed and breathe. 

A little below, limp branches of hydroids and stiff protrusions of sponges sprout from precious footholds amidst the mud, adding a dash of colour that warns of the risk of brushing bare skin on these sessile colonies. Spicules of silica or calcite confer to sponges structural rigidity as well as the tactile properties of fine, sharp glass. On the frilly twigs that dangle with apparent helplessless, each regularly-spaced bud forms a tentacled polyp with countless nematocysts ready to harpoon and hurt careless hands and naked heels.

But even the most potent stings meet their match in the endless pool of creations that the sea has had time to conjure and concoct. With ample layers of protective slime and ferocious mouthparts, nudibranchs claim a degree of dominion over the cnidarians and porifera. Even the feared men-of-war that drift with impunity on sails of purple have their nemesis in a genus of pelagic slugs that harvest their stinging cells for their own arsenal. Hydroids and sponges face their own array of radulan foes, such as this absurdly dotted Hypselodoris infucata, who pay the price of conquering difficult prey with such morphological and behavioural specialisations that they can consume little else and starve in marine tanks when confined by stupid aquarists.

In the dim, cavern-like space beneath a tall jetty, the ground is littered with the halves of cockles and clams, the remains of creatures who forage and feed in the mud with the ease of a muscled foot. Further out on the flat, there must be countless numbers of these shellfish, competing with each other and other burrowers for prime spots that allow ready access to plankton-rich water as well as unblocked passage for escape from shovelling rays and marauding crabs. Those who failed to dig in hard and fast enough now lie strewn beneath our feet, while their probable killers lurk under stones to avoid their own predators.

On the slippery stones that dot the substrate, there are slimey coats of zooanthids, tiny anemone-like polyps that seem to grow on sites shunned by other settlers, as well as pioneering colonies of Oulastrea hard corals that struggle to defy the shore's murky depths. Small stars, urchins and thorny sea cucumbers also cling to crevices on the rockface with the sticky security of tube feet. And just at the land's edge, there was a large feather star with an attendant ophiuroid. Bristling with arms of deep green tipped with smart white, each feathery ray unfurled and coiled in turn to trap the living dust that floats in its world of waves, little bothered by our unsought attention and the ceaseless sound of a million sightless beings squirming and scrambling in the sediment on which it stands.

Comments

[eric]

Another wonderful post, and these images are wonderful. I never tire of your marine invert photos!

[budak]

Thanks!