17/07/2026
🪼 Are there more jellyfish this year? 🪼
With a surge of sightings around the UK, could the ongoing marine heatwave be behind a bloom, or are there just more people enjoying the sunshine and visiting the beach?
NOC Oceanographer Dr Zoe Jacobs asked University of Southampton Marine Biologist Prof Cathy Lucas to find out.
❔Is what we're seeing now unusual? ❔
A: Jellyfish numbers vary every year. It might be the warmer weather, or more people visiting the coast reporting sightings. The only non-native species spotted is the mauve stinger, common in Mediterranean waters.
❔Is the marine heatwave causing blooms?❔
A: It's really the temperatures and conditions in spring (Feb-Apr) that are more important for most UK species; good conditions can lead to large populations. Winds and sea conditions could also be causing more jellies to be spotted inshore and wash up on beaches.
❔Do UK jellyfish like warmer conditions❔
A: We lack evidence to suggest they 'like' it, but species like the compass, moon, and mauve stinger jellyfish are tolerant of a wider range of temperatures. Baby jellies (polyps) tend to prefer cooler springtime conditions.
❔What should I do if I see a jellyfish❔
A: Most UK species aren't too dangerous, but it's best to avoid touching them (alive, washed up, or even loose tentacles).
Get familiar with the species that could cause the most harm, and follow NHS advice for stings.
Join in on citizen science efforts, and report your sighting to the Marine Conservation Society.
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Blue jellyfish image credit:©️ Vsevolod Rudyi CC BY 4.0 iNaturalist.org
