Irukandji are almost impossible to detect in water because they are not only tiny but also transparent. But these jellyfish can have a dangerous, and potentially fatal, sting leaving some patients in need of life support after an encounter. Each year 50-100 hospitalisations due to irukandji are reported in Austrailia.
Australian scientists have used sting data obtained from hospital records and wind data for the Great Barrier Reef area to form a hypothesize . The team found that most Irukandji stings occurred during the summer when south-easterly trade winds along the shore were less persistent. They also found that the timing of the stings tended to happen a day after a drop in these winds to near zero leaving only an onshore breeze. They hypothesize that this drop in south-easterly trade winds, and the movement of water they cause, is likely to be a contributing factor to the increase in stings.
While south-easterly trade winds are strong they cause turbulence in the ocean surface leading to a down-welling, sinking flow. Jellyfish in the water column would be carried away from the shore and swept northwards. When the south-easterly trade winds are weaker and there is less turbulence, the deep water that was previously pulled downwards and out to sea, can move onshore carrying jellyfish with it. In addition, the scientists hypothesize that the onshore sea breeze might enhance the effect thereby increasing onshore transport of water and jellyfish to the beaches.
The researchers say the connection between stings and wind conditions could indicate that interventions based on wind monitoring might be an effective strategy for reducing stings. Currently beach closures and other warnings are based on confirmed Irukandji stings or sightings; though effective at reducing stings this strategy is costly for the tourism industry (and relies on some people being stung). The team say their study could help develop a new system to give advanced warning of the presence of Irukajdji.