The Occhio alla medusa project has recorded an exponential increase in jellyfish sightings along the Italian coastline between 2009 and 2015.
The seas and oceans across the world are emptying at an increasingly alarming rate — in the last forty-five years the quantity of fish fauna has in fact halved — and the unstoppable acidification of the waters will render the oceans unsuitable for many species. There are, however, some ancient and mysterious creatures that, unlike others, are taking advantage of the current situation and are multiplying: jellyfish.
In six years, from 2009 to 2015, jellyfish sightings in the Mediterranean increased by as much as tenfold. This is what the Occhio alla medusa study reports, conducted by the University of Salento in collaboration with the marine ecosystem conservation association Marevivo. The project drew on so-called citizen science — that is, scientific research activities to which citizens actively contribute — with members of the public sending researchers their own reports of jellyfish sightings along the Italian coastline. The number of jellyfish spotted increased exponentially, rising from three hundred reports in 2009 to three thousand in 2015.
According to the researchers, the main cause of the steady growth in jellyfish numbers is the rise in global temperatures brought about by climate change. These fascinating animals, belonging to the group of Cnidaria, are extremely adaptable and thrive in warm climates, and their expansion is not confined to the Mediterranean — they are also on the increase in south-east Asia, the Black Sea, the Gulf of Mexico and the North Sea. Another cause of the spread of jellyfish is the uncontrolled exploitation of the seas and fish populations. Reckless fishing has created dangerous imbalances in the marine food chain, reducing the number of animals that feed on jellyfish — such as tuna, sea turtles and swordfish — and that keep their numbers in check.
Experts believe that fish fauna would decline even further as a result, since jellyfish feed on zooplankton, fish eggs and larvae, and also compete with juvenile fish for food. Contact between humans and jellyfish — notoriously unpleasant — will also increase: jellyfish normally live 20–40 miles from the coast, where the water is more saline, but the rising salinity of coastal waters is said to have created an ideal habitat for these animals close to the shoreline as well.
"In all our seas there may be jellyfish, creatures that have inhabited the oceans since time immemorial, since before the evolution of all the other current inhabitants," explained Ferdinando Boero, professor of zoology at the University of Salento and associate researcher at Cnr-Ismar. "The most dangerous ones are us, the scourge of ecosystems — not jellyfish. They are warning us that we are not behaving as we should towards the ecosystems that, through their functioning, allow our survival."
We tend to regard these bizarre organisms as inanimate objects swept along by currents, yet it is likely that jellyfish — which first appeared approximately seven hundred million years ago — will inherit the oceans of the entire globe and will continue to drift gracefully through the waves long after we are gone.