Sam Wells believes we may have been too quick to jump to conclusions about the proliferation of jellyfish blooms
We’ve all been there. Someone reassures us, ‘There’s plenty more fish in the sea,’ and we pluck up the courage to strike out again. But when we go looking for these promising creatures, we find a displeasing array in the pool of candidates: flabby dullards, aimless drifters, all lacking heart or brain.
These disheartening hauls are now being suffered not only by unwitting singletons but increasingly by fishers (regardless of their relationship status). From the Adriatic to the South China Sea, from the Caribbean to the Bay of Bengal, fishing vessels are dragging up tonnes of jellyfish from once-productive fishing grounds, in unwanted harvests so massive that they burst the nets or even sink the boats.
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So, is our world really becoming overrun with heartless imbeciles? It’s a common complaint.
‘Jellyfish blooms’ – biblical swarms of gently pulsating jellies, appearing as if from nowhere – occur naturally, but reported encounters have been on the rise. Inundated beaches are turning away tourists, leading to morbid assessments and fretful prognoses of lost earnings. A 2022 survey found that blooms of stinging jellyfish in St Ives would reduce the number of tourists in the town by nearly half – an exchange of one brainless visitor for another that even the most fed-up Cornish local would probably consider a downgrade.
More dangerously, jellyfish blooms have even been shutting down nuclear power plants. Around half the world’s nuclear plants are positioned on coastlines in order to access the millions of litres of water needed to cool their reactors daily. If a bloom occurs nearby, the jellyfish are sucked into the cooling circuit and the gelatinous mass clogs the filters, impeding flow and causing the reactors to overheat.
Blooms have shut down major plants in Scotland, Japan, South Africa, Sweden, India, Australia, the USA and elsewhere, as well as various state-of-the-art nuclear-powered warships and submarines. Once again, we find ourselves asking how a swathe of gormless, spineless simpletons have ambled into positions that hold sway over billions of pounds’ worth of infrastructure and the safety of sovereign citizens.
So, what is it about our system that rewards dimwittedness and snuffs out the wise and profound? In the case of jellyfish, their simplicity makes for a low-maintenance lifestyle that may better tolerate the changes being inflicted on the ocean.
When fertilisers and sewage are washed into coastal seas, algae grow at augmented rates and use up the oxygen in the water. Crustaceans and fish, with their demanding biological systems and fine-tuned breathing apparatuses, suffocate if they can’t relocate. Jellyfish, with their more primitive forms and modest metabolic demands, can endure.
Jellyfish are also less fussy about the intrusion of infrastructure. While most marine species require niche habitats and food sources for raising offspring, young jellyfish polyps can settle on just about any stable surface, impassively drawing nutrients from the open water. Piers, docks, breakwaters and oil rigs do the job. And while bottom trawling is apocalyptic for most nearby creatures, jellyfish polyps can set up shop along the trails of rocky rubble carved through the seabed.
Perhaps most advantageously, jellyfish aren’t particularly tasty. Having tender, flaky flesh that is subtle and savoury on the human tongue is a perilous characteristic for a sea creature to have evolved. And while we avoid jellyfish, we extract their dietary competitors, such as sardines and anchovies, as well as their predators, such as tuna, swordfish and – mostly by accident – turtles. The bland and rubbery are coming out on top.
The reactions to blooms have been predictable, seemingly filled with fear and rage, from walling off swimming areas with catch-all nets to unleashing jellyfish-shredding drones into fishing grounds. In September, when several hundred tonnes of jellyfish shut down eastern China’s largest coal-fired power plant for ten days, it revived interest in a patent filed in 2019 – for a technique to identify polyp hotspots then scrub all hard surfaces clean of any form of life.
There is little resistance to these enterprises. After all, the media frequently declares a ‘jellyfish plague’, a ‘jellyfish apocalypse’, an ‘ocean of slime’. And as we have seen, numerous industries are decrying excessive blooming events. But perhaps we should pause.
Is that evidence enough of an ecological problem?
Nuclear power plants, fishing corporations and tourist boards may report more blooms, but the rise in nuclear reactors, industrial fishing expeditions and seaside resorts is a trend that has been far more reliably observed. Conduct more bloom- sensitive operations and blooms will cause more problems.
And if human activity does facilitate blooms locally, the sites of this activity will obviously observe a disproportionate number. There is now simply a greater overlap between humans and jellyfish.
We have probably all spent a morning browsing social media and concluded that the world is becoming overrun by morons without compass or conscience, only to go out to the shops and be struck by the pleasantness of the first person we happen to encounter. If you spend your time where the brainless congregate, whether in Facebook comment sections or in desolated fishing grounds, you are likely to develop a distorted perception of their abundance.
So, we need data. What does the science say?
Well, numerous scientific papers state that blooms are increasing and that human activity is the cause. But let us pause again. Scientists are not immune from groupthink here – so intuitive, now, is the notion of our degraded oceans giving way to toxic, near-lifeless organisms, often likened to plastic bags. The scientific literature has suffered from a ‘citation cascade’, creating an illusion of widespread, impervious consensus. Initially, a handful of studies tentatively suggested correlations between human activity and jellyfish blooms, and found preliminary evidence through experiments. But they made no pretence of having proved causality, much less that the blooms would be healthy and reproductively successful.
Yet dozens of other papers have cited them and overstated their modest conclusions. These overzealous interpretations were subsequently cited themselves and exaggerated further. Soon, the media is reporting a global crisis.
In this way, the reliability of the peer review system carries the possibility of self-harm: any inaccuracies that squeeze through the net may be considered sufficiently well evaluated to be cited as evidence in future research. It’s like a nightclub being so confident in its doormen that it refuses to acknowledge a skirmish breaking out on the dance floor.
Most importantly, the primary studies only made claims about a very small number of jellyfish species with very particular characteristics. Even the unverified reports of increasing blooms are limited to a dozen or so. Yet there are hundreds of jellyfish species (and thousands more species that tend to be lumped in with them).
Humans have gone gung-ho into population controls innumerable times. In the 1970s, the sea urchin population exploded in Japan, largely because predators such as wrasse and lobster were being overfished. Inconveniently, the over-abundant urchins began eating their way through kelp forests – a food source and habitat for commercially valuable fishes. But decades later, countless costly culls have had negligible impact. Kelp is still hampered by polluted, warming waters. And with their predators still being overfished, urchins bounce back with improved health and reproductive success.
These fluctuations only cause algal blooms, with grievous effects on wildlife.
But even campaigners sceptical of jellyfish culls are now being charmed by whispers of a silver bullet. If we could convince people to start eating jellyfish, the logic goes, we could clear up the blooms, lighten the pressure on fish stocks and turn a profit all at once.
Setting our sights on jellyfish, however, could be a fatal misstep. With our preferred fishes depleted, jellyfish are filling gaps in disrupted food chains. Many predators will have adapted their diets. Targeting a resilient link between photosynthetic microorganisms and large, endangered predators, with no certainty that regular fish stocks will recover, could be catastrophic.
Going after survivors is a perverse way of trying to balance the books.
Whole ecosystems must be allowed to recover – and jellyfish will have their part to play in that. Some jellyfish are actually home – or temporary shelter – to several species of fish. In the open ocean, small fish are defenceless against larger, faster predators, and a mesh of stinging tentacles makes the perfect hiding place. Many juvenile fish will not leave the safety of the reef if there are no jellyfish swarms to hitch a ride in. They are floating ecosystems.
If you find yourself bemoaning a general intellectual malaise, try to remember the last time you spoke to someone for half an hour, in person, and came away thinking they were empty-headed. It’s quite rare. Jellyfish, too, reveal complexity when we pay attention.
At the aquarium, ignore the screams of ‘Nemo!’, walk past the fervent gaggle at the shark tank and join the cluster of children standing in enchanted silence under the slow blue scintillations of the jellyfish tank. Invariably, the bizarre beauty of these creatures at the edge of animal life awakens a sense of awe. Let us reawaken it.
