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Large Jellyfish Swarm Off Haifa Coast Giving the Public the Wrong Idea, Experts Say
Swarm of jellyfish in the Mediterranean Sea, near Haifa, July 19, 2022 (Rotem Sadeh/Israel Nature and Parks Authority)

Large Jellyfish Swarm Off Haifa Coast Giving the Public the Wrong Idea, Experts Say

The gelatinous creatures create problems for Israel’s desalination plants, causing them to reduce or suspend production to cut filtering costs

Footage of a jellyfish swarm off the coast of Haifa released by the Israel Nature and Parks Authority on Wednesday has gone viral in the country.

The phenomenon has made it to the headlines in Israeli and many international media outlets, where the swarm has been presented as unusually massive and an anomaly.

However, Dr. Zafrir Kuplik, the coelenterates collection manager at the Steinhardt Museum of Natural History at Tel Aviv University’s Israel National Center for Biodiversity Studies, told The Media Line that people saying the number of jellyfish on Israel’s coasts this year is significantly higher than in other years are engaging in guesswork.

“I wouldn’t call it significantly higher, because we don’t know that,” Kuplik said.

Prof. Ido Bar-Zeev, from the Zuckerberg Institute for Water Research at Ben Gurion University, agrees.

“I can tell you that, to the best of my knowledge, there is no real quantitative justification to say that this year we have greater numbers of jellyfish on our coasts,” Bar-Zeev told The Media Line.

Israel’s Mediterranean coast regularly experiences jellyfish swarms in the summer months. This happens during what is often called the country’s “jellyfish season,” which is usually between sometime in June and late July/mid-August.

Kuplik explained that what is indeed different about this year is that more of the jellyfish are concentrated farther out, away from the shoreline.

The number of jellyfish could be the same as every year, he added, “but they’re not arriving to the shore, they’re just concentrating offshore.”

He explained that the jellyfish are plankton by definition, and plankton drift with the current.

The jellyfish that we see in the coastal waters of Israel are probably coming from the south.

“My guess is from the Nile River Delta in the southeastern tip of the Eastern Mediterranean,” said Kuplik.

Jellyfish are produced by a small creature called polyps. The polyps are tiny, and they’re attached to the bottom of the sea, to the seabed, which makes them difficult to spot, he explained.

“Even one square meter [10.76 square feet] can carry hundreds or thousands of polyps. Each polyp produces dozens of jellyfish. This miniature-size creature can produce thousands of jellyfish of millimeters in diameter,” noted Kuplik.

They are dependent on the current, he added, and probably the current was a little bit different this year.

He added that because the bulk of the jellyfish stayed offshore, some of the disturbances they usually cause will not be witnessed with the current swarm.

“Enterprises that usually are being affected by jellyfish, like tourism activities, are less affected this year. … I don’t think that the power plants will suffer this year more than every year because their cooling systems take water from the shoreline,” he added when asked about the pipes that Israeli power plants use for their cooling systems.

A worker removes jellyfish that were fished out of the cooling water supply at a power plant in the Mediterranean coastal city of Hadera, Israel, June 27, 2017. (Jack Guez/AFP via Getty Images)

Bar-Zeev said that desalination facilities will be affected by jellyfish to the same degree as usual.

“Whether the numbers are a bit higher or a bit lower than in previous years is not that significant, as the issue of jellyfish for desalination is immense in any case,” he said.

The water for most desalination facilities is drawn from about 1.5 to 2 kilometers (0.93 to 1.25 miles) offshore, through a pipe that is situated about 5 meters (16.5 feet) under the sea surface.

Once the swarms of jellyfish arrive, he said, “depending on the biomass, on how many of them come at once, in a lot of cases large numbers of them are pumped into the desalination facility.”

Bar-Zeev added that the desalination facilities have machines that look something like big washing machines, which try to filter out solid matter so that water alone passes through the process.

“The problem is that this screening drum in a lot of cases is basically slicing the jellyfish into smaller parts that go into their facility,” he said. Jellyfish are clogging the pretreatment stages and the desalination membranes, he continued.

The water goes through several purifying processes that do not allow jellyfish particles into the final product. However, Bar-Zeev noted that doing this uses much more energy than in a process carried out without jellyfish present.

Energy consumption equals money, he said. To minimize costs, desalination faculties try to stop, or decrease, production until the swarms pass.

What is different this year, noted Bar-Zeev, is that the jellyfish are much smaller, down from around 20-100 cm (8-40 inches) in diameter to 5 cm (2 inches) and less.

He added that the biomass the smaller jellyfish can produce is immense. “We think that they will occur at shorter intervals during the summer and spring months, impacting the desalination procedure,” he said.

Kuplik pointed out that “although jellyfish are being talked about a lot in the news, we know very little, we have very limited knowledge about the jellyfish’s ecology and dynamics.”

All kinds of research groups are trying to understand the different factors that bring the jellyfish here, and to model the numbers and the time that they will arrive in Israel, he explained.

“There is much more to learn than what we know,” said Kuplik.

Bar-Zeev added that a group of researchers at the Zuckerberg Institute are working on minimizing the desalination plants’ problem with innovative devices such as smart barriers.

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