This decrease occurred despite a slight, generalized increase in sea temperature, as explained by César Bordehore, Professor of Ecology and coordinator of the Marine Laboratory at the University of Alicante (UA). Bordehore highlighted that approximately 90 percent of sightings are concentrated along the Mediterranean coast, and this year, specimens of Cotylorhiza tuberculata, popularly known as the 'fried egg' jellyfish, which is non-stinging, are predominant.
MedusApp has established itself as a key citizen science tool, allowing users to report sightings and stings in real-time, while also providing updated information to swimmers to help them anticipate the presence of these animals.
Bordehore recalled that water temperature does not have a direct and exclusive relationship with the number of jellyfish; it can only slightly influence their growth rate. The arrival of specimens to the coast depends on a chain of natural factors, including reproductive success in spring, survival against predators, reaching a visible size, and appropriate marine currents.
The expert emphasizes that the greater perception of jellyfish in summer is mainly due to the coincidence of more people on the beaches, rather than the temperature itself. 'Temperature has nothing to do with jellyfish. They are seen more in summer because there are more people on the beach,' he stated.
Another common species, Pelagia noctiluca, one of the most stinging jellyfish, can appear suddenly, coinciding with episodes of deep cold water upwelling caused by strong winds. This jellyfish, which normally inhabits great depths, is suddenly displaced towards areas near beaches, surprising swimmers. When this phenomenon occurs, warnings on apps like MedusApp typically surge within hours.
Finally, Bordehore insisted on the natural fluctuation of jellyfish populations, which rise and fall annually without apparent cause, influenced by predation and, secondarily, by temperature. Continuous monitoring through applications like MedusApp helps in better interpreting these variations and assists local administrations in planning information and beach signage more effectively.
