Predicting deadly jellyfish movement now possible
WE MAY SOON have a warning system to predict upto a week in advance when there’s a high risk of being stung by the tiny and almost invisible irukandji jellyfish.
One of the world’s most venomous family of creatures, irukandji jellyfish are a concern across northern Australia where they periodically appear off beaches during summer.
The stings of these tropical visitors have been known to cause fatal brain haemorrhagesm typically sending between 50-100 people into hospital each year.
Until now the movements of irukandji have been difficult to predict, other than a general time of year – summer – when they’re more prevalent.
The family of jellies sport bells upto three centimetres long, but it’s stings from their sometimes metre-long wispy tentacles (typically used to incapacitate prey) that can cause serious reactions and sometimes fatalities.
*Thirty minutes after a mild sting, irukandji syndrome symptoms can include severe lower back pain; excruciating muscle cramps in limbs, abdomen and chest; and sweating, anxiety, restlessness, nausea, vomiting, headache, palpitations, life-threatening hypertension, pulmonary oedema and toxic global heart dilatation.
Predicting Australian jellyfish movement
“The current way that we manage irukandjis is that pretty much the whole tropics is equally at risk November to May,” says Dr Lisa-ann Gershwin from the CSIRO and the paper’s lead researcher. Now, she says, we could give them window of time during these months that are low risk. “We’re getting closer and closer to giving the beaches back to people to enjoy on the days that aren’t high-risk,” says Lisa-ann.
The key finding of the jellyfish modelling is that irukandji jellyfish most often show up when there’s a drop off of south-easterly trade winds near the shore.
The link with winds may be about water turbulence, Lisa-ann says. When water is stirred up, irukandji typically stop swimming and sink to the bottom, and may be moved away from the shore by water movement. While currents caused by a drop-off of south-easterly winds may then carry these relatively weak swimmers closer into beaches.
Predicting jellyfish a tourism boon
Swimmers who stay out of the water on ‘high-risk days’, based on this new modelling, would reduce their chances of being stung by 90 per cent, says Lisa-ann, who authored Stung!: on jellyfish blooms and the future of the ocean. Athough it would mean swimmers could enter the water protection free for just over one-third of the high-risk season, that’s still a huge improvement on not being able to enter at all says Lisa.
Aside from freeing up beaches over summer, forecasting irukandji could lighten the burden for Australia’s tourism operators. In 2002 there were estimated losses to the tourism industry were in excess of $US65 million the Great Barrier Reef after two irukandji-linked fatalities.
Currently the theory has only been tested around Palm Cove, just north of Cairns in far north Queensland.
“We haven’t tested it for the Great Barrier Reef and its reefs and islands, for Broome, Exmouth, and overseas in places like Thailand and Malaysia with irukandji problems,” says Lisa-ann. “We think it will work in these other areas, but we haven’t tested it and done the tweaking yet, so that’s the next phase.”
The research is reported in the Journal of the Royal Society Interface.