A researcher has poured water on “emotive” claims that warming seas have spawned an abundance of jellyfish, and instead pointed the finger at a correlation with sunspot activity.
- Researcher says solar cycles correlate with jellyfish numbers
- Warming waters play a part in stimulating growth
- Expert says no definitive proof that tropical stingers are moving south
- Relocated jellyfish could be from ballast water
Stings by the deadly Irukandji jellyfish have more than doubled the 10-year average in Queensland, while tens of thousands of bluebottle stings have been reported from Queensland to New South Wales since December.
Marine science professor Kylie Pitt from Griffith University is seeking to publish a research paper connecting jellyfish numbers to the 22-year cycle of solar sunspot activity and subsequent changes in magnetic fields.
Pulling together worldwide datasets of jellyfish that go back decades, she said her team found the creatures would increase in abundance for 10 years, then decrease, then start again in what was found to be a 22-year cycle.
“We were a bit stumped for a while, but we’ve actually discovered that jellyfish populations at a global level seem to be tightly correlated to sun cycles,” Professor Pitt said.
“Sunspot activity occurs on an 11-year cycle, but at the end of every 11th year the polarity of the sun changes, so the magnetic field changes.”
Sunspots affecting ocean productivity
Some scientists believe there is a worldwide increase in jellyfish numbers due to warming waters and pollution and that tropical stingers could be pushing further south.
“There’s been a lot of emotive commentary about jellyfish for a long time, even in the scientific community, with people making claims that jellies under anthropogenic stress are going to take over the oceans and all that sort of stuff,” Professor Pitt said.
But her team believed jellyfish numbers increased because solar cycles could affect wind changes, which “turned over nutrients and stimulated the growth of phytoplankton” and subsequently ocean food productivity.
She said there was other biological phenomena correlated to sunspot cycles, such as whale beachings.
“By modelling the data we’ve made some predictions for what we think the global jellyfish populations are going to do over the next few years.
“We need to wait and see if that data starts rolling in and our predictions are supported.
“I think we’re at the start of another rising phase, so we might see some more jellyfish.”
Professor Pitt’s study found a “really small signal” that there was an overall increase in jellyfish numbers irrespective of the 22-year cycle but not one that was “statistically significant”.
“It’s absolutely not a given that warmer water causes more jellyfish and there’s nowhere near enough data to say that,” she said.
“Some of my colleagues are quite sure that it’s happening but the data for it isn’t very strong.”
Warming waters ‘rev up’ jellyfish
Dr Lisa-ann Gershwin, director of Australian Marine Stinger Advisory Services, said all the research she had seen pointed to jellyfish being stimulated by warming water.
“Warming water actually revs up their metabolism so they grow faster and they eat more,” she said.
“They reproduce more and faster and they live longer so they keep doing more of it.”
Dr Gershwin said jellyfish were further advantaged because warmer water held less dissolved oxygen and, unlike crustaceans and fish, they could survive without breathing because they stored oxygen in their jelly.
She suggested that under climate change scenarios, predators and competitors could die off as water warmed.
This would leave “more food for jellyfish and less opportunities to be someone else’s food”, and that they would be “stimulated by the warming water to grow into super-abundances”.
“We are heading towards a more gelatinous future,” she said.
No proof of warm water migration
But Dr Gershwin said there was no evidence that Irukandji numbers had increased or that tropical stingers were moving further south.