A new book by Robert Calcagno, director of Monaco’s Oceanographic Institute, helps explain the growing problem of jellyfish infestation along the Mediterranean.
“The best friend of the jellyfish is Man,” the subtitle of the book “Jellyfish and their Conquest of the Oceans,” highlights how human abuse of agricultural fertilisers and plastic waste has helped jellyfish proliferate to the point that many summertime beaches are almost no-go zones.
In the 70s and 80s jellyfish would appear for a few years and then disappear for six or seven years, whilst today they are an annual occurrence. “Global warming is a facilitating factor,” Calgano writes. The Mediterranean is not only warmer than it was, but plastic waste provides a floating home for the jellyfish polyps, the stage that precedes the mature form of the creature. “The polyps like to settle on (discarded food trays and polystyrene) and the currents bring this nursery to the coast,” Calgano writes.
A further factor promoting the plague of jellyfish is the declining number of sea turtles and tuna, which are the creatures’ natural predators.
In an appeal to reason, Calgano says: “If humans can not reconcile themselves with the ocean and have a more rational attitude, we can be sure that they will continue to proliferate, and only by letting the ocean regenerate ‘will it allow a balanced food chain where the presence of predators contains the presence of jellyfish.”