Jellyfish are maybe definitely going to kill us all, potentially.

In my last post I mentioned that I discovered ASMR on Despite how much I hate reddit and its userbase, I am addicted to its format. It’s honestly like a drug addiction. I hate it, and I hate myself for reading it, and yet I’m constantly going back and reading more of it. As terrible as that sounds, I recommend that any science enthusiast read reddit’s science section also known as r/science. It’s a amalgamation of links to articles, press releases and peer reviewed journals compiled by redditors who have nothing better to do than sift through all the world’s science and post links to what they think is compelling so that they might receive imaginary internet points. I wish that sentence were a misrepresentation of the truth.

Anyway, this was the front page of r/science today at around 4:30pm.

Screen Shot 2013-10-16 at 4.20.47 PM

Look at the second and third links. “Jellyfish are taking over the seas, and it might be too late to stop them” and “Jellyfish doom and gloom is over hyped; blooms are cyclical.”

Well, which one am I supposed to believe? Should I be stockpiling harpoon guns, peanut-butter, and whole wheat bread for the great human/jellyfish war of 2025?

I’m not a jellyfish expert (cnidariologist), or even a marine biologist. I’m not even a dude that like, spends a lot of time in/around the ocean. Is there anyway we can get to the bottom of this?



Data. Sweet, sweet data.

The first article, which predicts a large-scale jellyfish takeover, contains a lot of really cool facts:

  • Some 150,000 people are now treated for jellyfish stings in the Mediterranean each summer.
  • Last week, Sweden’s Oskarshamn nuclear power plant, which supplies 10% of the country’s energy, had to shut down one of its three reactors after a jellyfish invasion clogged the piping of its cooling system.
  • Japan’s now-annual bloom of Nomura jellyfish, which each grow to be the size of large refrigerator, capsized and sank a 10-ton trawler when the fishermen tried to haul up a net full of them.
  • This summer, a pileup of a million jellyfish along a 300 kilometer (186 miles) swath of Mediterranean coastline shortened swimming season for hundreds of thousands of tourists on beach holidays

These facts establish that Jellyfish blooms are a problem for humans. That’s good. I’m all for exigence, but none of this data proves that the jellyfish problem is new or getting worse. The article also includes this sentence however: “research of 45 major marine ecosystems shows that 62% saw an uptick in blooms (pdf) since 1950.” That’s great, but what if only all those ecosystems only increased by 1 jellyfish? What does the actual paper say?

  • “for most ecosystems, long time series of abundance measures for jellyfish are lacking, and the perceived widespread or global increase in jellyfish still lacks a rigorous foundation.”
  • “despite recent advances in research and understanding of jellyfish ecology at local scales, such knowledge is rarely used to evaluate possible causes or consequences of jelly-fish blooms at larger scales, or to make predictions”.
  • “Their peculiar life cycles, which can result in extremely high temporal and spatial variability in abundance, peaking in the form of ‘blooms’.”
  • “The lack of jellyfish population datasets covering large temporal and spatial scales limits the scope of inferences that can be drawn about jellyfish on a global basis.”

Oh. So basically we have no historical data about the prevalence of jellyfish. It seems audacious at best (misleading at worst) to say that Jellyfish are increasing in prevalence based solely on anecdotal evidence.

The other article is a bit more cautious with their language.

  • “The researchers found this decadal cycle throughout the entire 137-year dataset, but only detected a statistically significant pattern within the past 40 years. This could represent a real change through time, or might just reflect gaps in the available data.”
  • ” ‘It’s hard to separate out the lack of data from the lack of jellyfish,” said Haddock. “Nobody writes a paper about how there are no jellyfish out there’.”
  • “The team did detect a weak statistically significant rise in jellyfish populations within the past 40 years, though the signal was not as strong as previous studies have suggested.”

It seems this article, while less exciting to read, is getting at all the same things that Brotz paper was worried about. There are holes in the data. The article is careful to point out the strength of the trends discovered by Haddock and his team, even incorporating cautionary sentences and suggesting other causes for the data fluctuations. Their message is clear: the jury is still out on this topic, and the recent increase in jellyfish blooms might be a sign of things to come, or it might simply be part of the natural cycle of jellyfish abundance.

I’m not saying jellyfish aren’t a problem, or even that jellyfish aren’t poised to take over the world. What I’m trying to say is, I’m not stocking up on harpoon guns yet. I’m going to wait and see what the data says.



2 thoughts on “Jellyfish are maybe definitely going to kill us all, potentially.”

  1. And you will maybe, definitely get scurvy if you continue to eat nothing but peanut butter sandwiches. For the love of vitamins, throw some jam in with the rest of your end of the world stockpiles.

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