The pleasure sandhoppers get from the weed

The brown-fronded kelps of deep water make their spring growth cautiously, at the top of the stem, pushing up last year's fronds to be torn off and snatched away by the waves. Thus, last week, a bracing summer gale with a nice touch of north in it brought a whole raft of weed to the tideline below my hill. Scattered through the tangle were the sponge-like holdfasts of Sacchoriza polyschides, the frilly-stemmed, sweet-sapped species called charmingly, "furbelows" in English, and, in Irish, claimh∅, or "swords", from its deeply divided leaves. This annual seaweed can grow more than two metres in two months.

Between the mowings of summer winds and the wrenching storms of winter, a huge biomass of seaweed, rich in sugars and minerals, is cast ashore. Lawrence Hills, a great guru of the organic movement, once described dried seaweed as "the only genuinely complete organic fertiliser, in the sense that it holds a full set of plant nutrients and trace elements". What, then, becomes of it along our beaches (for nature is not given to waste)? In its steady disappearance, some kind of recycling obviously goes on, even on a bleak and wave-pounded stretch of sand or pebbles.

In the final dissolution of a bank of rotting seaweed, the sulphur-and-iodine reek speaks pungently of bacterial action, returning essential molecules to air and sea. But the process of disposal is substantially helped along by a multitude of minute animals that act as tideline scavengers. Their behaviour has sometimes moved observers to a somewhat exalted impression of their mood.

The sandhoppers (which Americans call "beach fleas") often feast by the million on the decaying weed, leaping about so densely that their jumping bodies seem to rise like a cloud at the edge of the sea. Watching this, William Paley, the English archdeacon who helped to shape Victorian views of nature's moral phenomena, was in no doubt of the amphipods' job satisfaction.

"If any motion of a mute animal could express delight, it was this," he wrote in his best-selling Natural Theology of 1802. "Suppose, then, what I have no doubt of, each individual of this number to be in a state of positive enjoyment, what a sum, collectively, of gratification and pleasure we have here before our view."

A century later, on the shores of Mweenish Island, it was the sheer industry of the tonachβn trβ that so impressed Seamas Mac an Iomaire, delightful folk-observer of marine life along the shores of Connemara. "He is always working at ebbing tide," he noted, "making small holes under the sand . . . He raises his hard, pointy little head from time to time to look around and see how the labour is going . . . Usually there are a huge crowd of them together, helping each other loyally and stoutly . . ."

Behind such fables of amphipod joy and togetherness there are facts no less affecting. In one of her brilliant books on marine life, Rachel Carson saw the sandhoppers as poised midway in an evolutionary leap from sea to land. They are bound, as yet, to the edge of the waves and the salt in the sand, yet they have forgotten how to swim and can still drown.

When a low tide coincides with night, they roam far out across the wet sand, gnawing at bits of seaweed or crab-leg ("their small bodies swaying with the vigour of their chewing", in Carson's evocative detail). Then, in retreat to the tideline, each begins to dig the burrow that will hide it from seabirds and keep out the rising water.

Working furiously with five pairs of legs, and kicking the sand out behind it (the same motion that propels it into the air), the sand-hopper takes about 10 minutes to excavate a tunnel, complete with terminal chamber and rammed-sand door - an effort equivalent to a man using his hands to dig a hole about 60 feet deep.

For both the main species of sand-hopper on Irish shores - Orchestia gammarellus on the shingly upper reaches; Talitrus saltator the burrower at the tideline - a furl of rotting seaweed provides not only food but essential humidity and dark cover for daylight feeding. To some local authorities, on the other hand, an untidy, perhaps somewhat whiffy tideline may be seen as an offence to the holiday trade.

In the early 1990s, the North Cornwall Council, seeking a Clean Beach certificate from the Tidy Britain group, began using a tractor and cultivator to rake its most popular tidelines. Warned that this devastation would bring swift extinction to T. saltator, nature's own scavenger, the council was undeterred.

Within two years (the normal life-cycle of the species), the sandhoppers had, indeed, disappeared, and the Tidy Britain group decided that local naturalists should, after all, be consulted about these things. Members of the Cornwall Wildlife Trust, inviting councillors to an "uncleaned" beach, were able to convince them about the value of sandhoppers, not only as scavengers but also as stabilisers of the tideline on strands backed by sand-dunes. Mechanical cleaning on such strands was promptly stopped, and sandhoppers reintroduced to carry on their search for food.

Thus, the old, anthropomorphic, even moral, admiration for this amphipod's ecstatic diligence has been succeeded by more objective, scientific reasons for approving. But Cilian Roden (himself a scientist), who introduces the new English translation of Seamus Mac an Iomaire's The Shores of Connemara, compares his warmth and passion of perception with "the model of the feelingless universe" presented in the journals of marine biology.

"In the last analysis," writes Roden, "Mac an Iomaire is not telling us about sand-hoppers, he is telling us about himself." A frank wonder and benevolence towards our fellow species, even at the risk of pushing human values where they do not belong, is nothing of which to be ashamed.