“Just when you thought it was safe to go back in the water…”
Jaws’ famous tagline makes most people think of sharks, but numbers of the apex predator have plummeted and one of their prey species, jellyfish, are swarming.
Globally, fewer than five people are killed by sharks each year, while around 100 died from jellyfish contact.
Their ability to cause painful stings is why swimmers were banished from Israel’s warm Mediterranean waters when hoards of jellyfish invaded last week.
Climate change, fertiliser runoff and over-fishing have been linked to the plagues of jellyfish. Their numbers have been growing since the 1980s, costing the country over $14 million a year in lost tourism revenue, and clogging fishing nets.
With rising seawater temperatures affecting Australia could the country soon be inflicted with a similar ecological and financial disaster?
Pre-pandemic figures suggested tourism was worth $122 billion a year to Australia. We spoke to two top marine experts to understand whether jellyfish pose a threat.
The bad news about jellyfish in Victoria
The density of lion’s mane jellyfish is already on the rise across parts of Victoria’s Port Phillip Bay.
Sea Life Aquarium’s lead aquarist Patrick Noble told Yahoo News Australia the seasonal occurrence is triggered by changing weather systems.
“When we hit summer, the water temperature starts to increase and then that's a biological indicator for the jellyfish to start to spawn. And we get those blooms of jellyfish coming through into the bay,” he said.
Lion’s mane jellyfish frequently inflict painful stings which can cause allergic reactions in some people, however unlike the Irukandji or box jellyfish, which are found in Queensland waters, contact with their tentacles is unlikely to send you to hospital.
The good news about the Great Barrier Reef
Great Barrier Reef Marine Park Authority (GBRMPA) chief scientist Dr David Wachenfeld said there isn’t any evidence of a long-term trend in jellyfish numbers increasing, but direct monitoring is not underway.
"(For that to change) it would need the community, or the tourism industry to say: Hang on, this doesn't seem right," he said.
"But no, we don't seem to have a problem."
Dr Wachenfeld believes the reef's water quality would have to significantly worsen for jellyfish numbers to spike, but with human populations in the area relatively low, and efforts to tackle agricultural runoff underway, this is unlikely.
The bad news about the Great Barrier Reef
While jellyfish numbers aren't a concern within the reef, Dr Wachenfeld is worried about the impact of climate change.
“We're seeing marine heat waves being more severe, more frequently,” he said.
“That causes a problem on the Great Barrier Reef primarily through coral bleaching events, which is a coral response to elevated temperatures.
“The concern is that we haven't stabilised the temperature, and we're still increasing, we're still emitting greenhouse gas emissions, and the temperatures are still going up.”
Is the Great Barrier Reef just about tourism?
The GBRMPA is guided by science released by the Intergovernmental Panel on Climate Change (IPCC) which has warned the world will reach 1.5 degrees of warming over pre-industrial levels early next decade.
“That is a decade earlier than they had ever said that would happen before, that's deeply concerning,” Dr Wachenfeld said.
While Deloitte found the Reef is worth $6.4 billion dollars a year in revenue to Australia, Dr Wachenfeld argues it’s ultimately impossible to put a monetary value on its significance.
He notes the marine park is "part of Australia’s national identity” and over 70 First Nations traditional custodian groups tie the region to their spiritual and cultural identities.
“It’s one of the seven natural wonders of the world, it was recognised as a World Heritage Area in 1981. You can't put a dollar value on that either,” he said.
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