Saturday 17 March 2018

Jellyfish explosion is sea's 'message in a bottle'

Sting: Jellyfish numbers are increasing Photo: Patricia Byrne/PA Wire
Sting: Jellyfish numbers are increasing Photo: Patricia Byrne/PA Wire

Joe Kennedy

Jellyfish are not universally loved, especially by most of us Northern Europeans confronted with them at a certain time of the year, such as now.

There's a certain hyperbole, of course, caused by their annual invasion of beaches in ever-increasing numbers, not to mention painful encounters. A pinch of salt won't allay fears, though pasting of top-notch sun-blocker is the recommended protection.

But these wobbly creatures have other uses. Fancy some Lion's Mane or Mauve Stinger for supper? I didn't think so. Folks from the Far East feel otherwise. Chinese, Koreans and Vietnamese love them, and have been including them in recipes for thousands of years. Jellyfish are a €20m export business.

Swordfish and tuna gorge on them and the wonderful leatherback turtle will follow them across oceans, often to its peril, as it ingests drifting plastic by mistake.

Jellyfish may be simple marine creatures drifting aimlessly along in the plankton, but thousands of bathers have unhappy encounters with them. More than 150,000 people are treated for stings along Mediterranean beaches each year.

Some species of jellyfish are nastier than others. The most unpleasant is the Mauve Stinger (pelagia noctiluca), about two inches in diameter, and which becomes luminescent when agitated. It is mushroom-shaped, with a purple and red-brown speckled bell with tentacles round the edge and large mouths in the middle. Its sting is severe. The large Lion's Mane (cyanea capillata) has been noticed inshore and washed up on beaches here. There can be identity confusion with the smaller Compass jelly (chryssaora hysoscella) - the lion is about 40 inches across and can give a painful sting, but the compass is relatively harmless.

But the most common jelly found in Irish waters is the Moon (Aurelia aurita), of a bluish tinge with four pale violet organs on top of the transparent bell. Tentacles round the edge can stun small creatures - but not you.

The explosion in jellyfish numbers is a worldwide phenomenon because of global warming and the filling of the ecosystem vacuum left by over-fishing. Josep Maria Gill of the Institute of Marine Sciences in Barcelona is profound: "The jellyfish we see on the beach is really the sea sending us a message in a bottle saying, 'look what is happening to me.'" Prof Stefana Piraino of Salenti University in Italy has a practical warning: "The socio-economic impact on (Europe's) tourist areas is huge. We are losing millions." Some resorts are using deep nets to fence off zones for safe bathing.

Two sea rovers, the Portuguese Man O' War and the By-the-Wind Sailor, are technically not jellies but free-floating colonial hydrozoans, polyps called siphonophores, which sail the oceans under gas-filled balloons.

The Portuguese "E perigoso" has a mass of blue tentacles dangling tens of metres beneath, with batteries of powerful nematocysts to kill prey. They are extremely dangerous to humans. The Sailor is a flat, bluish oval with an erect triangular sail, travelling the North Atlantic as far as the Faroes at this time of year.

Then there is the recently discovered "immortal" jelly, off the Italian coast, which can transform itself back to a polyp and start all over again! We might not want to know any more, but science wonders what benefits it might bring to mankind.

Sunday Independent

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