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Climate crisis brings increasing numbers of unusual jellyfish to UK seas | marine life

UK seas are becoming increasingly populated with large groups of unusual jellyfish due to a worsening climate, a survey by the Marine Conservation Society (MCS) has found.

In its first report of marine sightings, which is based on 20 years of citizen science, the company found an increased abundance of types of jellyfish, including those normally found in warmer climates. Thousands of volunteers participate in the MCS report, telling the conservation group what species of jellyfish and turtles they have seen.

Between October 1, 2021 and September 30, 2022, a total of 1,315 jellyfish sightings were reported to MCS. Eight species of jellyfish are normally seen in the UK and Ireland, but this year 11 have been spotted, with rarer visitors now visiting these waters.

Bioluminescent crystalline jellyfish accounted for 3% of the total number of sightings: these animals are almost completely transparent, but emit an astonishing green-blue light under certain circumstances due to the fluorescent protein produced by their bodies. They are usually found in the Pacific Ocean and rarely visit UK waters. One percent of sightings were gooseberries. Both were the highest percentages reported to date. The new arrivals suggest warmer temperatures could affect jellyfish diversity in the UK.

Last year there has been an increase in sightings of the famous Portuguese man o’war, a jellyfish-like creature that can deliver a sting powerful enough to kill a human. These increased by 2% compared to the previous year. The charity reported an increase in ‘other’ species seen from 5% to 9% this year.

It is believed that the increase in the number of jellyfish species and their abundance may continue due to the degradation of the climate.

Amy Pilsbury, Citizen Science Project Manager at MCS, said: “Changes in jellyfish abundance can be affected by many factors of climate change, such as sea surface temperature, salinity, pH , oxygen availability and habitat changes. Future climates will further alter marine dynamics and continue to influence plankton communities.

Unlike many other sea creatures, jellyfish are highly adapted to life in harsh environmental conditions.

Pilsbury added: “Jellyfish are very resilient and adaptable to changing environmental conditions. This sometimes results in large jellyfish blooms of hundreds or even thousands of individuals. These can disrupt marine ecosystems and be extremely detrimental to human activities.

“The Marine Conservation Society’s nearly 20-year-old dataset, collected by citizen scientists, can be used alongside climate data to study the impact of changes in our ocean on our visitors.”

Pilsbury explained: “The data shows an upward trend in some species spotted on our shores over the past 20 years, such as the Portuguese Man-of-War, for example. Preferring to drift in open water, they are at risk of being swept away by high winds and storms, which are becoming more and more frequent in the UK. Other reports show a slight decreasing trend over time, for example moon and lion’s mane jellyfish, which could indicate changes in plankton communities as sea temperature increases.

Sea turtles sometimes benefit from a boom in jellyfish numbers. The reptiles visit British waters during the summer months to feed on them. Last year, MCS volunteers reported 11 turtles, six of which were live leatherbacks, spotted on the Scottish coast.

theguardian Gt

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