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Global Environment

Jelly invaders from space?

There is nothing better than a vacation in a hot and sunny climate over summer, especially one which involves the beach and tanning lotion. However, this idyllic scene can become painfully interrupted by a sharp sting from an elusive marine culprit!

The mauve stinger, Pelagia noctiluca (Photo credit: Arn@ud Ab@die)

For the past decade, Mediterranean shores have been plagued by blooms of jellyfish, specifically the mauve stinger (Pelagia noctiluca). These pelagic stinging sea creatures travel with ocean currents, where they can move from the French Riviera as far east as the coasts of Cyprus. The mauve stinger is one of the dominant jellyfish types that have been observed to boom in very large numbers in the Mediterranean for a few years. In the past, such large waves of jellyfish were only a problem every 10 years or so, making the last thirteen years an inconvenient phenomenon. While there is no clear indication as to what causes such blooms, many scientists have attributed this to climate change due to increased water temperatures, lack of top predators due to over-fishing and habitat degradation.

Jellyfish bloom in Maltese waters (Photo credit: MaltaToday)

Jellyfish blooms happen in warm waters, where they find abundant food (generally suspended organic matter). Habitat degradation and pollution leads to more suspended particles, and over-fishing during summer removes many key jellyfish predators. This results in a large jellyfish bloom that persists for longer over summer, which can be quite inconvenient for Mediterranean countries. The mauve jellyfish’s sting is painful and can be dangerous to some people who are sensitive to them, so they annual repeated presence is cause for concern.

The Maltese Islands are no exception to the presence of such a jellyfish invasion, so in 2010 a group of research launched a ‘Spot the Jellyfish’ campaign. This campaign, coordinated by Prof Aldo Drago, Dr Alan Deidun and staff of the International Ocean Institute – Malta Operational Centre (IOI-MOC), follows a citizen science approach. The campaign strongly advocates for the education of the public, by recruiting their assistance in the recording of the presence and location of different jellyfish species through the presence of information panels and leaflets at bathing sites.

Since its inception, this campaign has yielded over 600 reports of a total of 18 gelatinous plankton species (12 cnidaria, 3 ctenophora, 3 ascidiacea/thaliacea), with the findings being published in a scientific paper. This initiative was also instrumental in providing the first ever recordings for numerous species in Maltese waters, including the blue button (Porpita porpita), the crystal jellyfish (Aequorea sp.), the moon jellyfish (Aurelia aurita), Cladonema radiatum and most notably Rhopilema nomadica, for which the Maltese Islands represent the westernmost record within the Mediterranean for this invasive species.

The next time you visit Malta over summer, make sure you look out for this campaign at any bathing site on the Islands, and you too can contribute to this interesting and innovative research programme!

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