After a while, we gave up counting, for the slugs littered the flat with small green bodies that swayed in the wake of our steps, their mantle flaps askew and aflutter as they charted a tenuous path through a carpet of dubious nerites and Batillaria shells, some in midcreep and others in post-mortem tow to nervous little hermit crabs. Elysia ornata lives in thrall to finely branched chlorophytes that erupt every now and then, taking turns, as it were, with unpalatable sargassum to swamp local shores. But Padina was the dominant seaweed on the sandy bottom of Tanah Merah last Friday, so the sapsuckers probably arrived under duress, the victims perhaps of recent storms that pummelled the waters beyond the seawall and swept loose residents of the reef beyond into the shallow trench on the inner flank of a porous crest.
Other denizens of this artificial coastline probably crept in without compulsion, sensing in their chemoreceptors the stirrings of young colonies or seeking the protection of sheltered waters. There are few chances such as this to observe the creatures of deeper slopes at close quarters, even if they remain ill at ease with the harsh illumination of their lairs. Damselfish, cardinalfish, groupers, butterflyfish, scorpionfish and squirrelfish cower by the rocks, displaying little inclination to explore the sandy expanse on which lurk moon crabs, blue portunids, pale gobies and wayward slugs. Decorated hippolytids and velcro crabs lurk between the boulders, as do anomurans that usually inhabit the outer sides of reefs. Dardanus, a genus of robust diogenids that usually shun the intertidal zone, is represented here by megistos, a striking animal covered with black-ringed ocelli. Prominent bristles cover the limbs and chelipeds, forming dense tufts on the distal segments, while maroon eyestalks render the corneas indistinct against a carapace of orange-brown to thick red hues. Crustacea have less trouble synthesising astaxanthin, a red pigment derived from dietary carotenoids, than melanin, so the brilliance of these crabs is probably the result of selective forces that operate in the shadows of Indo-Pacific seas, where the animals forage after dark, picking on slower things such as starfish and sea cucumbers, which they dismember with sturdy claws and spineless appetites.
The small population of Archaster typicus on the upper reaches of this shore appears to have eluded the attention of predatory paguroids, though a few individuals sport more or less than the typical array of spine-lined arms. Most lie under a radial cloak of silt during low tide, for exposed asteroids may fall prey to ghost crabs, which emerge at dusk to overwhelm stranded bodies and claim dibs on fresh carcasses. Happy to dip no more than their toes in wet grains, Ocypode's hunt for decaying fragments brings the crabs to the lower terraces of the breakwater as well as the top of the inner bund, where they seem poised to invade the forest of casuarinas and acacias that shield this beach from casual explorers.
A few patches of seagrass have established themselves in this ditch, where they flourish on sunlight and the runoff of an invasive wood. Small carpet anemones puncture the meadows, serving as ersatz blooms for halophytes with miniscule inflorescences. Other clearings are occupied by pairs of inch-long alpheid shrimp, which maintain burrows under wedges of rubble and wage a futile war against sediment and sinkage. Chunky gravel is ferried out between stiff dactyli, while furious sweeps by synchronised pleopods send finer grains out of the tunnels. Each couple seems to perform their fair share of housekeeping duties, though it is likely that males, with their vastly larger armature, take the lead in snapping at unwelcome visitors. Filaments that have settled on the roof of their abode provide handy pickings, but one female, seeking richer fare, ventured a little distance away to grab an undersized snail, which she dragged home for breaking in before the tide returns to flood these caridean outposts and fill their chambers with fresh debris from a straits of turbulent labours.