A mysterious light was flickering on the shore when we approached the southern end of Pulau Semakau earlier this month for a brief survey of the flats that stretch from the mouth of an artificial creek to the topmost edge of the western reef. The beam emitted glares of suspicion as our inflatable powered down over a slope of sand and rubble, while the mothership bobbed by the cages of a sea bass farm. It was still too dim for the manipulator to be visible, and long before we set foot on the island, the torch and the body attached to it had forded the creek and scaled the seawall that embraces the future of solid waste in Singapore.
The nocturnal explorer was probably not a guard on the night shift or a wayward camper bored with the bund. For signs of an effort to bag cheap seafood were later seen, in a lengthy trap, anchored to a mangrove tree, that spanned a good portion of the shore. It was probably not the man's intention, but his net offered a quick and dirty glimpse of the beasts that usually swim out of reach in the waters beyond the landfill. The mesh had snared portunids, fantail rays, black-tipped reef sharks, tuskfish and horsecrabs en route to the beach, and the first wave of victims had already drawn fresher catches, while unwanted bodies had been tossed on the silt near the line.
There was no value, in the market or as meals, it seems, in the sharks. But plenty of other creatures would beg to differ, or just shut up and make short of the carcasses. In a day or two, muscle, cartilage, organs and jaws, the only bony parts of these fish, would have given way to the teeth, claws, mandibles, beaks, maxillipeds, rasping tongues, eversible probosces, tube feet and extruded juices of a marine waste disposal crew, who work in disconcert to tear down, break apart and rip asunder the remains of top predators laid low by the indifference of middling men.
Early mariners named this bend Tanjong Penyelai, but the original headland is now blunted by a plot of atonement, a wedge of mud lined with rock and littered with saplings. The replanted mangroves follow the curve of the bund and face Pulau Semakau's old forests; in between runs a salty brook, half-fed by swampy channels and fully engulfed by each springing tide. Seagrasses have invaded this divide, forming submerged lawns by the roots of Rhizophora trees and anchoring the substrate with a network of rhizomes. Thus rendered shallow and stable, the creek and its miniature delta provide a habitat for other solar panels. Carpet anemones, Stichodactyla haddoni and Stichodactyla gigantea, bask in this meadow, sprawled amid the vegetation or secured to islets of rubble. Small, transparent shrimp frolic on some individuals, but only a few show signs of a fishy entourage, in the hint of a tail or folds of tentacles that erupt in unaccountable shudders.
Macroalgae have taken hold, not with roots but suckers and rhizoids that capture portions of the flat and stain the meadow with fronds of brown and filamentous green. The seaweeds maintain a seasonal presence, booming to the tune of trophic shifts before burning themselves out at the end of each fertile cycle. Occasional propagules from nearby woods also find their way here, but unless the current brings them to other swamps, are not likely to settle with success. Instead, these and other bundles of botanical goodness – leaves, buds, fruit and flowers – will feed animals with catholic appetites or serve as the extended phenotypes of spineless craftsmen. Porter crabs paddle under fallen blades, while solitary tube worms strengthen the walls of their home with assorted debris, terrestrial or tidal.
A dead leaf, probably one from a sea hibiscus, also provided the means by which a masked burrowing crab was prevented from digging its way out of trouble. This crustacean is a decidedly curious thing: the carapace is oval and elongated, rather than broad and with clearly define antero- and posterolateral margins, as is typical of its infraorder. The antennular flagella are unusually long, with rows of fine setae that form an interlocking 'tube'. In Corystes, another member of the family, the tips of the antennae are the only visible parts of the buried animal, which uses a respiratory flow counter to that of most other crabs; water reaches the gills via openings by the side of the mouth and leaves via holes at the leg bases, causing the surrounding sand to 'bubble' in the process. Built to burrow, the crab engages its flattened limbs the moment it is placed on soft sediment, sinking out of sight in moments. Dropped on a consolidated surface, the legs swivel in vain and the crab, ill-equipped for jaunts over brief plains, soon pipes down and gives up.
This was the first recent sighting of a corystid at this locality, which seems to abound with rarities. Another serendipitous find was a sand star first seen off Changi East and later at Cyrene Reef, a monster with an underbelly of fruity shades. Larger, faster and meaner, with multiple rows of stiff, sharp marginal spines, including two upward-facing spikes between its arm bases, than the Astropecten that abound on northern beaches, this astropectinid is probably, like its smaller kin, a rampaging devourer of small shelly fauna, which are swallowed whole and reduced to indigestible fragments.
Another echinoderm seldom seen elsewhere is Stellaster equestris, an oddball of an asteroid with a broad disc and tapering arms. The aboral side is covered by granules of low contrast, which surround the papulae and render the animal indistinct from the contours of grainy flats, but the oral surface is marked by patches of rich pigment. Save its preference for ungainly lunges over legato runs, little else is known about this goniasterid – what it eats, where it hangs out, the way it defies predators and how the hell did these obscure little stars command a range stretching from Eastern Africa to south Japan and northern Australia.
A different star lies embedded in the test of Jacksonaster (=Laganum) depressum, a sand dollar with prominent divisions in the form of ambulacral 'petals'. Tube feet emerge from the grooves of this petaloid, not to move the animal but to permit gas exchange as the urchin glides over fine silt using its coat of minute spines. As befits a species distributed from the Red Sea and Zanzibar to New Caledonia and Tonga, this aberrant echinoid exhibits considerable diversity in thickness, shape and colour. Specimens from Singapore have been noted to have "unusually long spines" which impart a conspicious fringe to the margin and confer a soft texture to the underside. The most abundant sand dollar on local bars is a purplish disc that creeps just under the surface to little avail. Jacksonaster, however, seems to favour softer bottoms, such as the muddy slopes of Pulau Semakau, where it trundles through the sediment to mop up organic blooms and subject them to a toothy grind.
Pulau Semakau is also a refugia for Protoreaster nodosus, which lost nearly all its mainland haunts following extensive programmes to reclaim Singapore's southeastern coastline for housing estates and a littered park. Closely associated with seagrass beds adjacent to healthy reefs, these massive oreasterids still occur in reasonable numbers by the landfill, with scores congregating near the seaward edge of the reef flat and scattered individuals in the meadow proper. At the island's southern tip, as the sun rose from a horizon of casuarinas and clouds that dispel its power, we found at least half-a-dozen, including one pup, amid the rubble where the grass meets fledgling colonies of corals: Porites, Turbinaria, faviids, fungiids, Goniopora and alcyoniids that struggle to hit critical mass in hostile depths and withstand the onslaught of cold reactions to warmer seas.