ANOTHER LIFE: On a foggy August morning, with a slow curl to the sea, moon jellies seem to materialise at the tide's edge, as if they had been born on the sand that moment, rather than drifting ashore at the exhausted end of their lives. All over the world, as summer winds down, the glassy discs of Aurelia aurita fetch up at the tideline by the million, melt away to nothing, writes Michael Viney.
Jellyfish were some of the earliest multi-celled creatures in the sea: they could also be the last, if you heed some of the global doomsters of the Internet (for the full, disquieting flavour, try Earth Crash: Documenting the Collapse of a Dying Planet at http://eces.org/ec).
As humans empty the oceans of fish, so the story runs, the jellyfish are taking over, since they eat the same sort of food.
Scientists can be found to warn of a population explosion of Cnidaria family, with great "blooms" of the drifters as signs of disaster in progress.
Where the blooms are of species that sting people, the menace can seem all the more palpable. Last month, for example, Honolulu in Hawaii closed some of its beaches because of an invasion of box jellyfish, the cubozoa, which have a powerful sting (one species in Australian waters, the "sea wasp", Chironex fleckeri, can, indeed, kill people).
Inshore drifts of cubozoa are a regular event in Honolulu, but the numbers seem to be increasing. Along with the overfishing, scientists will no doubt weigh up the impact of man-made nutrients flowing out from Hawaii's rivers and sewers.
Box jellyfish, like most species of shallow waters, have a larval stage, attached to the sea-bed inshore: Aurelia, for example, rides out the winter as a tiny, plant-like polyp fixed to a rock, which then grows buds of new jellyfish, stacked on top of each other, and launches them one by one in spring.
Where feeding conditions are good, the polyps will thrive and all of them mature and release their young at much the same time. These drift around together, herded at times by wind and weather, or line up in thousands along the invisible confluence of currents. Big numbers of jellyfish may, indeed, be linked to overfishing and pollution, but their actual concentration owes a great deal to chance.
"Off the coast of France," reports Earth Crash, "aggregations of jellyfish have sunk 500-pound fishing nets. In Japan, jellies have clogged the water intakes of nuclear power plants. In the Gulf of Mexico, jellyfish are competing with humans for the larvae of commercially important species such as shrimp. One Gulf shrimp boat captain said that in some places, the jellies are so thick 'you can almost walk across the water on them."'
In June this year, the tidelines of some Munster beaches glistened with the tiny rainbowed floats of Velella velella, the by-the-wind-sailor: on a strand near Kilmore Quay, they numbered more than 300 to the metre. But the great mass of these small, ocean-going jellyfish, with their little flaps of sails, drifted on towards the coasts of Cornwall and Wales, where they washed up by the million. A sandy beach on Anglesey had five successive tidelines heaped with them, and the smell of their rotting was "horrendous". The bobbing armadas even went on to penetrate Scotland's Firth of Clyde for the first time on record.
Was this a real population explosion? No one knows. A scatter of Velella reach the strand at Thallabawn in most years and we shared in the last "invasion" of 1981, with its massive stranding of Velella and other oceanic drift animals in south-west Britain. But the cause, then and now, is most likely to be found in the patterns of wind.
Wind pushes Velella into drifting to the left or the right, according to which way the diagonal sail is mounted on the float: it's a mechanism for dispersal. Most arrivals at these islands are left-sailers, with the sail mounted NW-SE, and the steady succession of Atlantic depressions which ruined the early summer must have rounded them up in millions and ushered them north-west.
Unusually, many of them arrived with their deep-blue tissues virtually intact (hence the smell when they rotted), and one fished out of a bay in Dorset promptly released microscopic, free-swimming models of itself. At sea, these would sink into deeper currents and be swept away to spawn their own planktonic young, which would grow floats and rise to the surface again.
A similar reproductive mechanism may explain the mysterious stranding on Ireland's west coast, in November, 1998, of millions of the oceanic and luminous jellyfish Pelagia noctiluca. Most of them were tiny, but massed together they covered tidelines from Aran to Donegal in a slithery amber marmalade. They may have been swept north in the deep Lusitanian current, which passes the mouth of the Mediterranean and then mixes with the North Atlantic drift.
Pelagia has only a prickly sting for human skin, but all stinging species, even small ones or fragments of big ones, can have a calamitous impact on fish farmed in sea cages. Salmon may be panicked into dashing against the nets, and one sea-trout farm in Shetland lost 89,000 fish in 1998 when billions of planktonic larvae of Aurelia stung the fish as they passed through their gills.
ALONG with the Velella of early summer, Cornish observers have reported phenomenal numbers - hundreds, if not thousands, say local fishermen - of the big "root-mouth" jellyfish, Rhizostoma octopus, which clusters its four pairs of very large arms centrally beneath a thick dome of a bell. It feeds on microscopic plankton and its stinging cells do not frighten the small fish that sometimes swim in its company. Still less do they discourage the leatherback turtles - transatlantic migrants - that feed on the jellyfish itself, and the first of these has already been seen close inshore in Cornwall. Stella Turk, long-time recorder of the duchy's marine phenomena, notes that two other years of "root-mouth" abundance, 1988 and 1990, also brought the biggest number of leatherback sightings and strandings - a remarkable 17 for each year.
Rhizostoma is like the moon-jelly, Aurelia, in having young that spend time as polyps on the sea bed. But some of the adults are believed to overwinter in deep water - and these are the big ones that may be ushered in on early summer tides.
Jellyfish may, indeed, be on the increase in our much-abused oceans, but each event of exceptional numbers may have a special explanation of its own.
We have seen a pine marten in our garden, could it eat strawberries? An animal has been moving the jam jars off the plants and eating the fruit.
Pamela Osbourne, Thomastown, Co Kilkenny
The pine marten is the only one of the small mustelids that includes fruit and nuts in its diet. It is also a very enterprising little animal.
I watched two starlings fly down to the patio and peck at ants. They then appeared to preen their feathers. Was this a routine for keeping the feathers clean, or a way of killing ants?
Stephen O'Dowd, Limerick
The starlings were "anting", allowing ants to clear mites in their plumage. Several birds use ants for this purpose; they often find an ants' nest, disturb it, then crouch over it to let the ants into their feathers.
Here in suburban Foxrock, we have three or four peregrine falcons living around the houses, and we have seen them take a bird in mid-air. There is a constant "mewing" from them and all the other birds around here, even the magpies, are keeping a very low profile.
Declan Service, Foxrock, Co Dublin
I went to remove an old griselinia root from the back garden and found a colony of bumble bees underneath. I left the root undisturbed in case they were an endangered species. How long will they remain there and can I remove the root in winter?
Tom Murray, Raheny, Dublin 5
They will have left the nest by late September and you can remove the root any time from then.
Edited by Michael Viney, who welcomes observations sent to him at Thallabawn, Carrowniskey PO, Westport, Co Mayo. E-mail: viney@anu.ie
Observations sent by e-mail should be accompanied by postal address.