Sarah Vorsanger

Israel is taking on the Jellies

September 8, 2019

Every summer, jellyfish appear in the coastal waters of Israel, deterring beachgoers, thus, damaging the tourism industry. Now, Israeli scientists developed an app that helps to track these sea creatures in order to make one’s beach experience more enjoyable

Dr. Dor Edelist and Prof. Dror Angel, marine ecologists from the University of Haifa who specialize in jellyfish (meduzot in Hebrew), developed a web-application as well as a website ( to help locate meduzot.

“There is no map of jellyfish in the sea that informs people if they can go in the water safely. This prompted the start of this web-app,” says Edelist

“We have more than 500 new species that have come to the Mediterranean through to the Suez Canal and have established themselves in the Mediterranean. This includes the Nomad jellyfish (Rhopilema nomadica), which makes up about 90% of the jellyfish found in the eastern Mediterranean basin. Therefore, we worry about them the most,” says Edelist. These species are part of the Lessepsian migration, which is the largest biogeographic invasion of animals on the planet from the waters of the Indo-Pacific to the Mediterranean Sea. First sightings of the nomad jellyfish occurred in 1976, with swarms beginning in the early 1980s. The sting of a nomad jellyfish is painful, but it is crucial to note that it is not lethal.

Recent studies have shown an increase in the number of native and invasive jellyfish species in the Mediterranean Sea. Summer swarms of these jellyfish may range from May to August, with a peak in July, and winter swarms can span from January to March. Jellyfish proliferation also occurs due to anthropogenic changes such as eutrophication from increased nutrient runoff, overfishing, and climate change.

Nomad jellyfish outbreaks were first reported in 1986 in the southeast Levantine coast, where they affected many aspects of human interaction with the sea, including a decrease in tourism from beach closures, and fewer people choosing to spend their vacations at the seashore. According to this same study, the Israel Nature and Parks Authority estimates a loss of 8.9 – 31.1 million NIS each summer. Additionally, Nomad jellyfish have impacted coastal industrial installations such as power plants and desalination facilities by blocking water-intake pipes, cooling systems, and filters.

Jellyfish also affect fisheries. The jellyfish can cause a decline in fishery resources by consuming eggs, larvae, and juvenile fish. Jellyfish also compete with the fish for the same feed, which does not allow the fish to thrive. They can get caught in fishery equipment and harm both nets and lifting gear, thus decreasing the efficiency of this industry.

Non-indigenous jellyfish species found in Israeli waters are probably carried via ballast waters of ships, as polyps attached to boats, or they drift as eggs, larvae, or adults. For example, the Australian spotted jellyfish (Phyllorhiza punctata) is an invasive species that originated from the Pacific Ocean. The Purple starry jellyfish (Marivagia stellate), which also originates from the Pacific, was also recently spotted in the Mediterranean. Lastly, invasive comb jellyfish (ctenophores) were spotted in the Mediterranean for the first time in 2009.

More than 500 new species that have come to the Mediterranean through to the Suez Canal. Photo by Katarzyna Urbanek on Unsplash

The meduzot application relies on citizens to report the location of jellyfish as well as their species, size, number of stinging incidents, and abundance. This type of science is called citizen science, which allows people of all backgrounds, not just scientists, to become active members of their community while connecting them with and gaining knowledge about nature.

Because of citizen science efforts with this web-app, patterns and new species of jellyfish found in waters of Israel have been discovered. “They don’t just come in the summer, sting us, and leave,” says Edelist. They also come to Israeli waters in the winter, he adds. The winter jellyfish found in this region include extra-large Nomad jellyfish and Mauve stingers, the former being a venomous species found in the western Mediterranean basin that is brought to Israeli offshore waters by large winter storms. Edelist commented that even though they are venomous, most people in the waters at this time are surfers who are usually protected from the venom by their wetsuits.

In July of 2019 alone, 270,000 people looked at the map on the web-app to monitor where jellyfish are located. In addition, 8,000 people subscribed to the app. Over 700 sightings were recorded, and the Facebook group associated with the app reached 5,000 members. These statistics are double that of July 2018 and allowed for the discovery of a new species that had not been seen in this part of the Mediterranean before.

Currently, there are no policies in place that would contribute to the management of the jellyfish or prevent damage to coastal equipment. Only minimal and local preventative actions, including the Israel Electric Corporation deploying and dragging nets, has taken place. Public information has also been disseminated by the Israel Oceanographic and Limnological Research, but jellyfish are still absent from marine policy in the region.

It is clear that this web-app is an important step forward with regards to educating and protecting beachgoers. “The first stage of how to not get stung is by logging into the app and looking at the map. If there are jellyfish in the water and you still want to go in, then you now have the knowledge of how to protect yourself by putting on a swim shirt or wetsuit or even anti-jellyfish sunscreen,” Edelist says.

The web-app also advises beachgoers on what action to take if they do get stung. “Jellyfish in different locations around the world have different kinds of venom. Therefore, treatment is different for each kind of sting,” says Edelist. “There is a generic treatment in every location that differs depending on the most abundant species found. For instance, while vinegar may alleviate Box jellyfish stings in Australia, we recommend washing a Nomad jellyfish sting with seawater and treating it like a burn.”

In July of 2019 alone, 270,000 people looked at the jelly map on the jellyfish web-app to monitor where jellyfish are located. Photo by Avi Werde on Unsplash

A similar citizen science initiative that involves jellyfish sightings is called Jellywatch, started by the Monterey Bay Aquarium Research Institute (MBARI) in California. This project allows people to track marine life such as jellyfish, red tides, or a lack thereof. Reports have been collected from coasts all over the world, from North America to Europe, to Australia. Jellywatch also lists other citizen science projects that are specific to different areas around the world, including the Meduzot app developed by Edelist and Angel.

Edelist predicts that as long as the Suez Canal is open, there will be more species migrating to the eastern Mediterranean Sea in summers to come. “In Israel, we need to be thankful for what we don’t have: lethal jellyfish,” he exclaims. For whatever new species show up on the shores of Israel, the meduzot web-app will be available, (next summer in English as well) for people to continue to report jellyfish sightings and improve their beach experience. “We also hope to gain a better understanding of these sea creatures and help to come up with preventative measures for desalination and power plant intake pipes. In the long run, we strive to improve both the monitoring of the sea and public education through citizen science,” says Edelist.

This ZAVIT article was also published in The Jerusalem Post on 09/08/2019.