Crystal Jelly Swarms Signal Warming Seas in UK’s Cornwall Coast


The Aequorea victoria jellyfish, also known as the ‘crystal jelly,’ has been observed in an unusually large number off the coast of Cornwall. This bookish jellyfish is generally seen in the warmer waters of the Mediterranean, making its sighting in the United Kingdom a rare occurrence.

Known for its stunning clarity in the water, the species has recently been seen in substantial numbers at Cadgwith, situated on the scenic Lizard Peninsula in the western part of Cornwall. Sightings of the crystal jelly have also been reported in August at Alderney and Guernsey.

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Marine experts interpret these sightings as a possible indicator of warming seas. The noted increase of the crystal jellies in these waters is potentially resulting from shifts in climate and subsequent changes in sea temperatures.

While the crystal jelly possesses stinging cells, these are not potent enough to cause harm to humans, assures Matt Slater from the Cornwall Wildlife Trust. He recalled the influx of these luminescent creatures during his dive off the Lizard, where the jellyfish accumulated in the bays, forming an otherworldly ceiling above the divers.

In Slater’s words, the presence of crystal jellies can often be a case of “boom or bust”. Their lifecycle involves rapid reproduction, generating thousands of tiny larvae. While in some years, all of the larvae perish, in others, changing conditions may allow for the survival of the entire brood, leading to a sudden surge in their population.

Known to feed primarily on plankton, including marine plants and animal plankton, the dietary habits of the Aequorea victoria are being studied by Cornwall Wildlife Trust. However, due to the existence of multiple species within the Aequorea family, the scientists from Plymouth’s Marine Biological Association are undertaking DNA analysis to identify the exact species observed in the recent sightings. This exercise forms part of the ‘Darwin Tree of Life Project,’ aiming to provide accurate species identification for better understanding and conservation efforts.