Huge Swarms of Stinging Jellyfish Should Ring Alarm Bells

However, there can be too much of a good thing.

The mauve stinger, a lovely-looking jellyfish from the sub-tropical waters of the Mediterranean, suddenly turned up in the Irish Sea. The new population exploded into an infestation that covered 26 square kilometres to a depth of 10 metres.

These stinging jellyfish overwhelmed Northern Ireland's only salmon farm, killing every salmon -- big and small -- at a cost of $3 million. A week later, a similar mass, this time both mauve stingers and the indigenous compass jellyfish, threatened the Scottish coast. This might be dismissed as one of those anomalies that news agencies move on slow days under the heading "oddities" except that there was nothing odd about it.

For a decade, reports have been coming in describing increasingly nightmarish jellyfish swarms in the world's oceans. The same mauve stingers that wiped out Northern Ireland's fledgling salmon aquaculture industry in a matter of days have been playing havoc with summer vacationers on the Mediterranean coasts, threatening billions in tourism revenue.

In 2006, they washed up on the beaches from Costa Brava to the Cote d'Azure by the tens of millions and 70,000 bathers and beachcombers required medical treatment for painful stings and allergic reactions while clean-up crews struggled to dispose of tonnes of rotting invertebrates.