Unusually high number of jellyfish arrive in UK seas
3 Min Read
A sharp rise in jellyfish blooms across UK waters is linked to record sea surface temperatures and climate change, with new species arriving and sightings up 32% in 2024.
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Moon jellyfish are shown, on July 30, 2011, off the shores of Pompano Beach, Florida. (AP Photo/Wilfredo Lee)
An unusually high number of jellyfish have appeared in UK waters this summer, with marine experts linking the increase to warm sea surface temperatures and climate change. Jellyfish follow warm ocean currents toward the coast as part of their reproductive cycle, and prolonged periods of elevated temperatures create ideal conditions for blooms.
According to marine scientists, global heating is contributing to more frequent and longer-lasting jellyfish populations during the summer months. These conditions are also likely to attract new jellyfish species that prefer warmer seas.
Sightings of jellyfish in British waters have risen significantly. The Marine Conservation Society recorded 1,432 reports in 2024, a 32% increase compared with the previous year.
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Abigail McQuatters-Gollop, a marine conservation expert at the University of Plymouth, noted that warmer seas linked to climate change are "more likely to result in more jellyfish blooms."
Among the most commonly spotted species this summer is the barrel jellyfish, known for its large size, reaching up to a metre in diameter, and its relatively mild sting. Despite its intimidating appearance, the barrel jellyfish is harmless to most humans and is even consumed in parts of Asia.
Other species reported this season include the compass jellyfish, identifiable by its dark radial markings and painful sting, as well as moon jellyfish, lion’s mane, blue, and the mauve stinger. These jellyfish play a key role in the marine food web. "Compass jellyfish are a particular favourite source of food for turtles," McQuatters-Gollop explained.
Climate Change driving marine shifts
The rise in jellyfish numbers is closely tied to climate-related changes in the marine environment. Record sea surface temperatures were recorded by the Met Office in April and May this year, setting the stage for widespread jellyfish activity.
Jellyfish have short life spans, with many born and dying in the same summer. Some follow the currents back out to sea, while others die off due to exhaustion, storms, or lack of food.
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"They are composed of 90% water and can break apart easily," said McQuatters-Gollop, noting that extreme weather events, intensified by climate breakdown, often damage their fragile bodies.
Despite their reputation, jellyfish are vital to ocean ecosystems and often misunderstood. McQuatters-Gollop encouraged people to observe them safely and appreciate their beauty.
"Jellyfish have beautiful colours, long tentacles streaming behind them, and look like something that belongs in outer space," she said. "I wanted to encourage people to safely observe jellyfish and fall in love with them, because they are amazing and I feel so lucky when I dive and swim alongside them."
