It was not exactly the way Neil Agius hoped he would raise awareness about the dramatic changes taking place in our oceans and seas.

But when a bloom of jellyfish forced the Olympian out of the water between Mallorca and Ibiza and away from the record books, he did exactly that.

The environmental activist was stung an estimated 60 times as he attempted the longest unassisted open-water swim to raise awareness about the problem of pollution and pollutants.

While jellyfish are not uncommon in the Mediterranean Sea, Agius’s experience emphasised a growing problem.

According to marine biologist, researcher and university professor Alan Deidun, overfishing, pollution and global warming have caused jellyfish populations to rapidly increase since the start of the millennium.

Agius in Mallorca before setting off. Photo: Neil Agius/Facebook

Spanish waters – the site of the swimmer’s latest challenge as he attempted to swim 160km from Mallorca to Ibiza – have been particularly affected, Deidun said.

“The Spanish have been working on the issue for a while now... for them, jellyfish have been a problem for a long time,” he said.

The Pelagia noctiluca jellyfish, better known as the mauve stinger, is the likely culprit for Agius’s recent experience, Deidun said.

While common to the Atlantic Ocean and Western Mediterranean Sea, he said their numbers have exploded over the last 20 years.

Why so many jellyfish?

Recalling a warning by Italian jellyfish expert Ferdinando Boero at a conference some years ago that the Mediterranean was facing a “paradigm shift” away from a fish-dominated to a jellyfish-dominated sea, Deidun explained there were multiple factors contributing to the rise of the species.

“Over-fishing, firstly, is a significant problem as younger fish compete with jellyfish for the same sources of food,” he said.

Another factor attributed to the steep rise in jellyfish numbers is the large volume of nutrients being deposited by human activity, Deidun explained.

“Pollution from treated sewage, land fertilisers and food used in fish farming food all play a part,” he noted, with higher nutrients in the water increasing plankton populations, a source of food for jellyfish.

The construction of jetties, wharfs, oil rigs and breakwaters has also supported increasing populations, he said. Their structures create ideal environments for jellyfish larvae to latch onto.

The problem is that jellyfish are actually favoured by human impacts

Rising sea temperatures could also be a factor, he added, with jellyfish enjoying shorter reproductive cycles in warmer waters.

NASA has highlighted the rise in sea temperatures, noting that 90 per cent of global warming is occurring in the ocean, causing the water’s internal heat to increase since modern record keeping began in 1955.

Deidun is keen to emphasise that rising jellyfish numbers are the result of multiple contributing factors, however. 

“The sea is under multiple stressors and the problem is that jellyfish are actually favoured by human impacts... they’re a species very suited to the changes we’re seeing,” he said.

How can the problem be solved?

Despite the concerns raised, rising jellyfish numbers could nonetheless prove to yield unexpected economic opportunities.

Scientists are collaborating with Michelin-star chefs to turn jellyfish into a delicacy as an effective way to control the species.

The EU, through its Blue Growth Strategy, is also addressing the problem, funding research into the benefits of jellyfish to humans in a bid to exploit the increasingly abundant resource for use in industrial applications and food and cosmetic products.

For now, however, swimmers like Agius could continue to face challenging conditions in their bid to push the limits of what is humanly possible.

And while Agius may not have returned to Malta holding a new world record on this occasion, he undoubtedly succeeded in his quest to raise awareness of the challenges posed to the planet’s seas.

“The 100-mile swim is not just about setting a world record,” he had said shortly before wading into the sea.

“More importantly, it is about highlighting the problems of pollution and pollutants in our sea and ocean.”