ILIAD experts from Haifa University forecast jellyfish free summer

11th July 2023

A team of researchers from the University of Haifa which is partner in the EU-funded ILIAD Project, forecast that it is a high likelihood that this summer Israel’s shores will be almost free of jellyfish.

“If you look at the past years with similar patterns, mostly 2016 and 2018, this is definitely the reasonable estimate as of this moment,” the experts noted. So far, deep into the bathing season it seems that their forecast is accurate. In previous years, at this time of the year huge swarms of the wandering, water-logged Rhopilema nomadica, which is the commonest jellyfish species in the region, already reached Israel’s beaches. But today aside from scattered reports we are almost completely free of them – so it’s possible that this situation will be maintained throughout the summer. “Based on previous years when the jellyfish arrived late and we had only small swarms this late, it is possible that we will see a similar phenomenon this year as well,” said Dr. Dor Edelist, a marine ecologist and lecturer at the university’s maritime civilizations department. In recent years, at the beginning of July, a large swarm of jellyfish has filled the beaches–clogging power plants’ filters and making bathers’ nervous because they feared being stung. The scientists turned the jellyfish observations into a “Digital Twin of the Ocean”, represented online and streamlined with other datasets coming from multiple sensors to create a holistic Digital Twin. Additionally, the University of Haifa researchers enhanced crowdsourcing effort to properly standardize and map swarms. Partnering with 14 other similar initiatives working on jellyfish sightings across the Mediterranean, they look for the “big picture” of jellyfish blooms and their relations to global and reginal climate change.

Dr. Edelist and his department colleague Prof. Dror Angel, who founded the website “Jellyfish Inc” (Meduzot Ba’am) at to report the encounters with the creatures, said that currently, most participants are pleased by the lack of jellyfish. “In previous years, by we would receive many reports from yachtsmen and trawlers from way offshore that jellyfish are on their way to us and by bathers and surfers getting stung profusely. Not this year”.

What explains their absence?

One possibility is a change in ocean currents, which did not sweep the jellyfish to Israel’s beaches, but researchers didn’t find reports of swarms in other countries as well, where they could have reached due to a change in the currents. Other more plausible options are that a late warming of the waters caused a disturbance in one of the complex life stages of jellyfish (the polyp stage). Another option is the lack of nutrients and small oceanic mixing from a relatively dry winter almost devoid of storms. The researchers agree that climate change cannot be ruled out, and may have caused the seawater to warm more slowly this year, so the temperature for the jellyfish polyps ideally to “ripen” was delayed by about two-three weeks. In light of this, their initial assessment was that the jellyfish would also be late for a similar amount of time, and as time passed, the jellyfish refused to come. “It’s possible that when they did mature, another factor came into the picture, for example an animal that preys on the jellyfish when they are still small. Of course, other things may have happened, because the sea is a complex and complicated system,” Angel added. “There is no doubt that a summer without jellyfish is great news for bathers, but if anyone thinks that this is the end of them, they are wrong. What happened this year does not say anything about the population of jellyfish that sit on the seabed when they are still in the polyp stage. Most likely, the polyp colonies still exist and waiting for the right conditions to hatch and release mature jellyfish into the sea. This year is just a slight blow for them,” Angel concluded.

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