Jellyfish plague in the Mediterranean Sea

Thousands of jellyfish are currently washing ashore along the coast north of Barcelona, Spain. There are more of them, and they are arriving earlier than in previous years. According to experts, the jellyfish are benefiting from climate change. In the warmed sea, they can reproduce twice a year.

Last week was exceptionally warm on the Costa Brava with 29.4 degrees Celsius.

However, beachgoers seeking relief on the shores were confronted with unpleasant company: thousands of moon jellyfish (Pelagia noctiluca), forming a wide band on the beach and drifting in the sea. Another species of polyp (Velella velella), resembling a jellyfish, was also frequently observed.

The presence of these jellyfish is normal in spring on the east coast of Spain. But this year, the creatures are appearing earlier than usual. According to experts, this trend will continue, with jellyfish becoming increasingly abundant in the Mediterranean Sea. Due to the higher water temperature, which has risen and continues to rise due to climate change, they can reproduce multiple times a year.

Another reason for the increased number of jellyfish is related to the drought, which has persisted on the east coast of Spain for over three years. With less rainfall, less freshwater flows into the sea via rivers, and coastal water no longer forms a natural barrier to saltwater creatures.

The moon jellyfish is well-known in Catalonia, being the most common jellyfish there. Previously, it appeared only in May or June, but now the jellyfish species is showing up a month earlier. Moon jellyfish live in swarms several kilometers from the coast, at depths of 100 to 200 meters. At night, the jellyfish move to the water surface to feed and can be blown to the coast by the wind.

The Pelagia noctiluca, which can glow in the dark, is known for its stinging ability. The jellyfish injects a toxic venom. This can be dangerous, especially upon repeated contact, potentially causing anaphylactic shock in some people. A carefully applied layer of sunscreen can keep the jellyfish away from the bay.

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Daan van Dijken

Ten years ago, I started setting up a freshwater aquarium. Since then, I always have been fascinated by the underwater world. Together with my wife, we have been fortunate to discover this on many beautiful journeys and explored the magnificent underwater world through diving. In 2023, we have started a 60-liter saltwater aquarium. Soon, we realized that we wanted to further expand our saltwater aquarium hobby, so we switched to a Red Sea Peninsula 650. It's a fantastic aquarium that brings daily joy to me, my wife, and our daughter. I enjoy keeping up with the latest developments in the saltwater world and love exploring how to make my tank even smarter and easier to maintain. As a newcome, I would like to share all my experiences in setting up a saltwater aquarium with you!

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Stefan van Beek

Salt has always run in my blood. From birth, aquariums surrounded me, first at my grandfather's and later at my parents’ place. Now, at the age of 30, I've been able to set up my dream tank, a 160x70x70 peninsula. Corals hold the second spot for me; fish and the entire ecosystem are the reasons I have an aquarium. Nearly a decade ago, I started with my first aquarium, making plenty of mistakes and learning a great deal from them. Since 2021, I've been working at Ocean&Lake in the Netherlands, where I am now fully responsible for the saltwater department.

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