Recent sightings of Rhopilema Nomadica jellyfish were reported along Israel's shores, notable not only for their appearance after a season lacking any jellyfish presence, but for their extraordinary size, with some exceeding a weight of 30 kilos (66 lbs.)
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"Winter swarms of Nomad Jellyfish have become routine in recent years, but this year the size of the jellyfish is definitely exceptional," Dr. Dor Adelist from the department of Maritime Civilizations at Haifa University said. "After a summer without jellyfish, and the immense size of the jellyfish in the winter swarms, we expect that the upcoming summer will be abundant with jellyfish."
Adelist noted that a few theories could shed light on the emergence of these oversized jellyfish, with one leading hypothesis pointing to the significant rainfall this season, which has washed a bounty of nutrients into the marine environment.
This nutrient surge has likely spurred an upsurge in algae, which in turn supports larger populations of zooplankton. These zooplankton, a food source for the jellyfish, are contributing to the larger-than-usual jellyfish population.
"The last time we had such a phenomenon, of a summer without jellyfish followed by developed winter swarms, was in 2016-7 and afterwards we experienced intensive summer swarms in the summer of 2017, so we are also predicting a significant bloom in the months of June and July this summer," Adelist said.