Britain’s seas are becoming populated with large groups of unusual jellyfish owing to climate breakdown, a survey by the Marine Conservation Society (MCS) has found.
In its first marine sightings report, which builds on 20 years of citizen science, the society has found an increased abundance of jellyfish types, including those normally found in warmer climes. Thousands of volunteers take part in the MCS report, telling the conservation group which species of jellyfish and turtles they have seen.
Between 1 October 2021 and 30 September 2022, there were a total of 1,315 jellyfish sightings reported to the MCS. Eight jellyfish species are normally seen around the UK and Ireland but this year 11 were spotted, with more uncommon visitors now visiting these waters
Bioluminescent crystal jellyfish made up 3% of total sightings: these animals are nearly completely transparent, but give off an amazing green-blue light under certain circumstances because of the fluorescent protein produced by their bodies. They are usually found in the Pacific Ocean and rarely visit UK waters. One per cent of the sightings were sea gooseberries. Both were the highest percentages reported to date. The new arrivals suggests that warmer temperatures may be affecting jellyfish diversity in the UK.
Last year, there was an increase in sightings of the notorious portuguese man o’war, a jellyfish-like creature that can deliver a sting powerful enough to kill a human. Those were up by 2% from the previous year. The charity reported an increase in “other” species seen, up from 5% to 9% this year.
It is thought that the rises in the number of jellyfish species and their abundance could continue owing to climate breakdown.
Amy Pilsbury, the citizen science project lead at the MCS, said: “Changes in jellyfish abundance can be affected by lots of different climate change factors, like sea surface temperature, salinity, pH, oxygen availability and habitat changes. Future climates will change marine dynamics even further and continue to influence planktonic communities.”
Unlike many other marine creatures, jellyfish are very suited to living in difficult environment conditions.
Pilsbury added: “Jellyfish are highly resilient and adaptable to changes in environmental conditions. This sometimes results in large jellyfish blooms of hundreds, or even thousands, of individuals. These can disrupt marine ecosystems and be extremely damaging to human activities.
“The Marine Conservation Society’s almost 20-year-long data set, collected by citizen scientists, can be used alongside climate data to investigate how changes in our ocean are impacting our ocean visitors.”
Pilsbury explained: “The data shows an increasing trend in some species being spotted on our shores over the last 20 years, like portuguese man o’war, for example. Preferring to drift in open water, they are at risk of being washed ashore by strong winds and storm events, which are becoming more frequent in the UK. Other reports show a slight decreasing trend over time, eg moon and lion’s mane jellyfish, which could indicate shifts in plankton communities as sea temperatures rise.”
Marine turtles sometimes benefit from a boom in jellyfish numbers. The reptiles visit UK waters in the summer months to feed on them. Last year, MCS volunteers reported 11 turtles, six of which were live leatherback turtles, spotted on the coast of Scotland.
