Jellyfish are swarming in massive numbers in the Mediterranean Sea, close to the port city of Haifa in northern Israel. The sea was "bedazzled with thousands of white dots," according to The Jerusalem Post, which also reported that the swarm extended below the surface to depths of several hundred meters.
Officials with Israel’s Nature and Parks Authority (NPA) captured footage of the swarming nomad jellyfish (Rhopilema nomadica) in Haifa Bay on July 20 using aerial drones, and they shared the footage on the agency's website. The NPA also advised people against swimming in the area, due to the risk of painful jellyfish stings.
This unusually high concentration of jellyfish individuals, also known as a bloom, likely stems from human activities that may include pollution and climate change , NPA representatives said in a statement (translated from Hebrew).
The explosion in jellyfish numbers this summer could have catastrophic consequences for the marine ecosystem near coastal Haifa, and could even affect industry and tourism, Ruthy Yahel, an NPA marine ecologist, said in the statement.
"We see great damage from it in many areas, such as ecological competition with the fish for food, economic damage, clogging of desalination plant pumps, cooling of power plants, damage to fishermen, and the public keeping their feet off the beaches because of the burning [from jellyfish stings]," Yahel said. (Remember: Despite the urban legend, don't treat jellyfish stings with pee, which can cause the jellyfish's stinging cells to release more venom. Instead, remove the tentacles with a tool — not your bare fingers — and splash something acidic, such as vinegar, on the wound, Live Science previously reported.)
Jellyfish are a common sight off the coast of Israel during the summer, and large blooms were reported in 2015 and 2017, The Jerusalem Post reported. The University of Haifa maintains a website that tracks jellyfish swarms using reports from open water swimmers, divers, boaters, fishers, surfers, paddlers and kayakers. Its interactive map helps both fishing boats and beachgoers avoid areas of the ocean and beaches where jellyfish swarms have been spotted.
Nomad jellyfish, currently the most common jellyfish species in waters near Haifa, are an invasive species that originated in tropical waters of the Indian and Pacific Oceans. Scientists suspect that the jellyfish invaded the Mediterranean from the Indian Ocean by using the Suez Canal — the artificial waterway in Egypt that connects the Mediterranean to the Red Sea through the Isthmus of Suez — CNN reported in 2015.
One possible cause for jellyfish blooms such as the recently-observed event, could be pollution; jellyfish may have flocked to this region in record numbers to escape sewage and dispersing solid waste that's pumped into the ocean, according to the NPA statement. Overfishing and population reduction in ocean animals that compete with jellyfish, such as sunfish, or that prey on them, such as sea turtles, could also explain why jellyfish are especially numerous this year, NPA representatives said.
Changing climate could also be playing a part in driving Haifa's jellyfish bonanza, Dror Angel, a marine ecologist in the University of Haifa’s Department of Maritime Civilizations, told The Jerusalem Post. "The past winter has been very rainy and cold at times. This may have affected the intensity of the blooms and their life cycle," Angel said. "We know for sure if there’s heavy rain, then lots of nutrients get washed into the sea. So there's more algae, plankton and more food for the jellyfish to eat."
Originally published on Live Science.
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Jamie Carter is a freelance journalist and regular Live Science contributor based in Cardiff, U.K. He is the author of A Stargazing Program For Beginners and lectures on astronomy and the natural world. Jamie regularly writes for Space.com, TechRadar.com, Forbes Science, BBC Wildlife magazine and Scientific American, and many others. He edits WhenIsTheNextEclipse.com.