Marine heatwaves: Jellyfish thrive in the UK

Jellyfish sightings in the UK have soared 32% in the last year, due to our warming waters.

From October 2022 to September 2023, jellyfish sightings have soared 32% along UK coasts. The bulk of these sightings have been on the UK's Atlantic west coast, particularly around Cornwall and Wales.

Species such as barrel jellyfish, Lion's mane, Portuguese man o' war, moon and compass jellyfish have all been spotted, including crystal jellyfish, which are more commonly known to warmer waters.

The hot weather in recent months, particularly in June, created marine conditions for the species to thrive in the UK.

We're all familiar with the idea of a heatwave, but a marine heatwave is much less visible yet equally concerning. Marine heatwaves are periods of unusually warm ocean temperatures that can last anywhere from days to months.

Warmer waters due to marine heatwaves can severely impact marine ecosystems, creating nutrient-deficient "ocean deserts" that make it challenging for marine life to survive.

These temperature spikes are linked to a range of disruptions, from coral bleaching and altered fish migration patterns to the degradation of vital kelp forests along the coast.

That being said, it has led to a positive influx of new jellyfish species to UK coasts, though this could have knock-on implications on the marine ecosystem.

Scientists are unsure if the new species are a short-term result of the marine heatwaves, or a longer-term shift in their northward range as waters warm on average.