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Will venomous Irukandji jellyfish reach south-east Queensland?

For the people of northern Australia, dangerous jellyfish stings are all too common. But under changing ocean conditions, could more of these dangerous jellyfish be moving farther south along the Queensland…

An adult Irukandji jellyfish, which vary in size being from as small as your thumb to as large as your palm. Dr Jamie Seymour

For the people of northern Australia, dangerous jellyfish stings are all too common. But under changing ocean conditions, could more of these dangerous jellyfish be moving farther south along the Queensland coast?

Increasing ocean temperatures and strengthening ocean currents are causing many marine species to migrate polewards. Among the species predicted to expand their distribution is the potentially deadly Irukandji jellyfish, which are found in tropical regions around the world, including northern Queensland.

If these jellyfish do reach south-east Queensland waters, it could have a severe impact on local tourism and human health in coming generations.

Our new research, published today in Global Change Biology, looked at whether the jellyfish was more or less likely to migrate towards sub-tropical regions between now and 2100, using Queensland as our case study.

A tiny sting, then a shock to the system

With a translucent body that makes them almost invisible in the water, Irukandji jellyfish fire venom-filled stingers into their victims, which most humans barely feel at first.

But up to two hours after the sting, people stung by one of these jellyfish can start feeling multiple symptoms of the debilitating “Irukandji syndrome”.

Those symptoms can include vomiting, generalised sweating and severe pain in the back, limbs or abdomen, a sense of impending doom and a rapid heart beat. (You can read more on the symptoms and what you should do if stung here.)

Spreading south

While Queensland is a “hot spot” for Irukandji stings, these jellyfish have historically been confined to waters north of Gladstone.

But in March 2007 an adult Irukandji jellyfish was recorded for the first time as far south as Hervey Bay, just over three hours drive north of Brisbane, and there have been numerous reports of people being stung by Irukandji in this region.

The concern is that these tropical jellyfish could already be being transported south on the East Australian Current - the undersea highway made famous in Finding Nemo - towards the densely populated areas of southeast Queensland.

To establish a population outside of its normal range, a species must be able to tolerate the extremes of summer heat and winter cold in the local environment.

Our oceans are warming, with the CSIRO and others noting “striking evidence of extensive southward movements of tropical fish and plankton species in southeast Australia”. This is particularly apparent on the eastern coast of Australia, with the strengthening East Australian Current delivering warmer tropical waters farther south.

We are also seeing increasing signs of our oceans becoming more acidic.

So with all those changes underway, and expected to continue this century, we need to consider how Irukandji jellyfish could respond.

An Irukandji polyp, about 1mm big, magnified. Dr Jamie Seymour

Like many species of jellyfish, Irukandji have a complex life history. The stage we recognise as a “jellyfish” is the adult stage. The adults produce larvae that swim to the sea floor and turn into tiny polyps just 1-2 millimetres high - smaller than a match head - which can produce more polyps by budding. When conditions are favourable, these polyps change into jellyfish.

Our research, published today, undertook climate change simulation experiments to determine whether the polyps of one species of Irukandji jellyfish could tolerate the current and the future, looking at winter and summer temperature and acidification conditions predicted for south-east Queensland around 2100.

We found that polyps budded prolifically under warmer temperatures, but although they survived more acidic conditions, their budding was inhibited.

However, the relative rates at which temperature and acidity change in the future may influence whether Irukandji jellyfish are capable of moving south.

If waters continue to warm but acidification proceeds more slowly than predicted, then Irukandji could migrate farther south in the short term.

What’s stopping them moving into southern Queensland?

Our most interesting finding was that Irukandji polyps can already tolerate both the current winter and summer temperature and acidity conditions in south-east Queensland waters. So why aren’t they seen there already?

One factor that could be preventing them being a more common sight in the region is a lack of suitable habitat for the polyps of the Irukandji species. While scientists have never been able to find polyps in their natural environment, adult jellyfish have been observed spawning near coral reefs on the Great Barrier Reef, suggesting that coral reefs may be their natural habitat.

Coral reefs do exist in south-east Queensland, but their total area and diversity is small and this may prevent populations of Irukandji from becoming established south of the Great Barrier Reef.

However, even if populations of polyps do not colonise south-east Queensland, the strengthening East Australian Current may transport jellyfish produced by polyps located in Great Barrier Reef waters into south-east Queensland.

So although the jellyfish may reach south-east Queensland in the future, our research raises some hope that they may not thrive.

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8 Comments sorted by

  1. Dale Bloom


    There could be good and bad news attached to this.

    If Irukandji were to travel south in large numbers, it might possibly delay or halt the destruction of coastal areas by the tourism and real estate industry.

    However, many people such as builders who are attached to the tourism and real estate industry would be out of a job.

    These people would then travel to other areas of the state, putting local people out of work.

  2. Mike Jubow

    forestry nurseryman

    So, if the limiting factors are that they need coral reef environments to breed in and acidity is also a limitation, there seems to be no problem for SEQ. The jerks in charge of this country are going to do nothing to stop CO2 emissions and the consequences of that will be lower pH in the oceans. The lower the pH, the less chance that coral will move south there-by precluding the the chances of the Irukandji from breeding in Moreton Bay and environs. Problem solved! Thank you Tony Abbott.

    1. Dale Bloom


      In reply to Mike Jubow

      Box jellyfish may travel south, and are more venomous than Irukandji.

      In fact, they may find polluted conditions towards the south more suitable.

      “All jellyfish appear to have the capacity to exploit perturbed ecosystems, effectively taking over the role of top predator and efficiently excluding other species from re-establishing. Factors such as turbidity, hydrocarbons, eutrophication, and decreased biodiversity, seem to have little detrimental effect, instead opening up niches vacated by other species with narrower ranges of tolerance.”

      Box jellyfish may need estuary systems to breed, but the destruction of estuary systems and mangrove areas in the south may be keeping their numbers down at present.

  3. Greg North

    Retired Engineer

    " Our most interesting finding was that Irukandji polyps can already tolerate both the current winter and summer temperature and acidity conditions in south-east Queensland waters. So why aren’t they seen there already? "
    I think you might find it is all to do with the seasonal weather some in as to how consistently strong a northerly wind can be in the summer.
    People south of Gladstone have had Irukandji close beaches at times, not on a regular basis but if there has been a prevailing northerly for more than a few days.
    It is usual practice for Life Savers to do some net sampling of waters if there have been prevailing northerlies for a few days or more from Late December on.

  4. Paul Rogers


    The first confirmed Irukandji case at Noosa or even Rainbow Beach will see the Queensland Sunshine Coast tourist industry devastated, perhaps never to recover.

    Reports from west side of Fraser Island already exist.

    Let's hope the reef hypothesis is valid.

    1. Dale Bloom


      In reply to Paul Rogers

      An example of nature fighting back.

  5. Colin Samundsett

    retired BSurv

    Neither the small Irukanji nor the large Sea Wasp, but Box Jellyfish just the same: in 1958 I saw an impressive aggregation of large Box Jellyfish just north of the NSW/QLD border. They were swimming with the incoming tide between South Stradbroke Island and Southport. They had large ropy tentacles at the square corners of the box-shaped bell. Local yokels the good books say, but I would not like to mix with them, and am not keen on conditions which might favour proliferation of any breed of Cubo medusa.