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Wild Things

The weird and wonderful in the natural world
Sarah Zielinski
Wild Things

Winds predict deadly jellyfish blooms

Signs near a beach north of Cairns, Australia, warn of the potential for being stung by jellyfish. A jug of vinegar is provided to treat stings.

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Last year, Gory Details blogger Erika Engelhaupt and I got into an argument over which country is most deadly. (Got a nomination? Tell us in the comments below.) Erika chose Ecuador. I argued for Australia. After all, the continent is home to an array of deadly creatures — including crocodiles, snakes and spiders — as well as vast areas of wilderness into which people still disappear. Offshore is especially unsafe, since that’s where you’ll find sharks (though they’re not nearly as deadly as you might assume) and, in northern Australia, box jellyfish.

I find the jellyfish to be particularly scary because there’s no way to avoid them if they happen to be in the water with you. Box jellyfish are tiny, translucent creatures that trail long, difficult-to-see tentacles. The first sting is reportedly not too bad, but hours later victims begin to suffer much worse — what’s known as Irukandji syndrome. Symptoms include vomiting, rapid heart rate, headache and an increase in blood pressure to levels that can be life-threatening.

Because it’s impossible to avoid the jellyfish once a person is in the water, the best strategy for avoidance is to stay out of the ocean altogether when the jellyfish are around. But it’s not practical to keep everyone dry during “jellyfish season,” which lasts for several tourist-heavy months of the summer. But in Australia near the Great Barrier Reef, locals know that you’re more likely to get stung when the winds come from the northeast.

And they’re right. Lisa-ann Gershwin and colleagues from CSIRO Wealth from Oceans Flagship in Hobart, Australia, report May 14 in the Journal of the Royal Society Interface that a change in the wind does indicate that a jellyfish bloom is likely.

The researchers matched up hospital and ambulance records from the coast off the northern Great Barrier Reef with records of winds from January 1985 to August 2012. Most of the time, winds in this region come from the southeast. But when these trade winds weaken, it heralds an increase in jellyfish stings.

What’s going on? The scientists aren’t completely sure — the life cycle of box jellyfish is still largely unknown — but they’ve got a hypothesis: The typical southeasterly trade winds cause turbulence in the water at the surface that keeps the jellyfish deeper in the water and offshore. But when those winds relax, the turbulence disappears and deeper cold water is brought up toward the shore, bringing the jellyfish to where people can get stung.

The details of the study pertain only to this one region of Australia, but they may also provide clues to other box jellyfish blooms in tropical waters. And they may lead to the development of technologies that would provide jellyfish forecasts. So one day, you may be able to download an app for your phone that would tell you when it was safe to dive on the Great Barrier Reef.

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