Some years it's plagues of ladybirds, cloudbursts of frogs, hordes of killer bees. This year, it looks like being jellyfish. "Swarms of the poisonous Lion's Mane jellyfish are set to reach Irish shores," we were warned the other Sunday.
Another Life/Michael Viney: Even this newspaper was deluded in June into publishing a photograph of a perfectly common compass jellyfish (like a brown-rayed art deco lampshade) under the dreaded label of the lion.
As I write, just half-a-dozen Cyanea have been spotted swimming in the Irish Sea, mostly off Louth and Meath, a normal summer quota for this species of the cooler northern Atlantic. When the lion's mane gets to shore at all, it is usually in bits. But, of course, as global warming disrupts familiar patterns of wind and current, what is "normal" may not be so any more.
Interesting things have been happening to more innocent jellyfish. Early this summer, for example, millions - literally millions - of by-the-wind sailors arrived at Irish shores. These are Velella, the little blue ocean-going jellyfish with an iridescent flap mounted diagonally on the float to serve as a sail. Those that reach us are usually adults a few centimetres across, but the astonishing numbers that ribboned the sea with blue off Dingle, Co Kerry, and piled up in drifts of sapphires on strands in Co Antrim, were all very young and less then 10mm across.
Their arrival was directed by wind and the clockwise current up the west coast. In a similar way, the ordinary moon-jellies, Aurelia, can be marshalled into dense concentrations. In early June, for example, an extraordinary raft of them was seen in a calm sea off the coast of north-west Wales: thousands wedged together in a glassy mattress some eight metres square.
Jellyfish around Ireland and Wales are under close study at the moment, as the chief food of the leatherback turtle. This fascinating, two-metre-long reptile with skin like a Wellington boot is a regular summer migrant to these waters, but is now endangered by loss of breeding habitat, and entanglements in fishing nets and ropes on its journeys back and forth.
Left alone, it can live for a century.
An EU-backed INTERREG collaboration between the University of Wales at Swansea and the NUI at Cork is studying the turtle's populations and migrant origins, and its behaviour in the Irish Sea. The project's welcome for sightings of both leatherbacks and jellyfish is set out in a most attractive and informative website - www.turtle.ie - to be kept updated through the summer.
The leatherback seizes prodigious numbers of jellyfish in its horny beak, and since each is more than 90 per cent water, the nutritional value seems questionable. Hauled ashore as a marine curiosity, which is still its sad fate from time to time, it weeps briny "tears" to get rid of all the salt. Part of the new research is to establish the calorific value, or energy units, available from a whole suite of species.
Chief among them is the giant "barrel" or "root-mouth" jellyfish, Rhizostoma, which clusters four pairs of very large arms beneath the thick dome of a bell that may be half a metre across or more. It feeds on microscopic plankton and its stinging cells do not frighten the small fish that often swim beneath it. Indeed, in sheltering perhaps 50 or 60 little mackerel or whiting, the jellyfish is serving as a mobile nursery.
Scientists have been trying for more than half a century to record the distribution and abundance of Rhizostoma in British and Irish waters. There were phenomenal numbers - hundreds, if not thousands - reported from Cornwall in 2002. Last summer, using a low-flying plane, researchers counted huge numbers in the big Carmarthen and Tremadoc bays in Wales. Both bays are known hotspots for sightings of foraging leatherbacks.
No one knows for sure that the turtles migrating to our waters travel across the Atlantic, rather than from rookeries in West Africa, but in 1997 a leatherback tagged in French Guiana was found dead on a beach in Wales. A study in the eastern Pacific, using a satellite, tracked a female leatherback for 2,780 kilometres travelled in 87 days.
It is an irony, indeed, that, after all these millions of years of existence, the turtles are becoming an endangered species, just when their food supply may never have been more abundant. As humans empty the oceans of fish, the jellyfish are taking over - or so the doomsayers' scenario runs. Fishing nets are sunk by them, salmon cages poisoned by them, bathing beaches emptied by them. Is this all the local workings of chance as more people use the sea more intensively - or even the impact of climate change on the highways and byways of the ocean?