Will Spain see more jellyfish this summer?

As the summer approaches, experts have hinted that there could be an increase in jellyfish populations along Spain’s beaches.

According to Josep-Maria Gili, a professor at the CSIC Sea’s Department of Marine Biology and Oceanography, ‘It is a bit early to predict the presence of jellyfish in 2024 on the Spanish coasts this summer, although we are on an increasing trend.’

Impact of climate on jellyfish numbers

The life cycle of jellyfish typically kicks into gear in late spring and extends throughout the summer. Rising sea temperatures—a direct effect of climate change—encourage these marine creatures to begin earlier, thus extending their reproduction cycle.

‘If the water temperature rises more and that water temperature is more persistent, the polyps will give rise to the jellyfish sooner. And they will appear a month earlier,’ Gili explains. This shift means not only more jellyfish each year but potentially two generations in a single summer.

Human activity and geography

The dwindling number of predators, due to overfishing and a decline in biodiversity, leaves fewer natural controls on the jellyfish population.

Geographical factors also play a role. Jellyfish swarms are often pushed towards the coast by sea winds and surface currents, increasing their presence on the beaches.

Drought and the changing coastline

Normally, cooler freshwaters from rain and rivers delay the arrival of jellyfish swarms until deep into the summer.

However, Gili points out that drought and the reduced flow from rivers are altering this pattern: ‘The continental contributions from rains and rivers act as a natural barrier and keep these large swarms of jellyfish away from the coast, which is why so many of them reach the coast and the large schools arrived well into the summer.’

Despite the increasing presence of jellyfish, it’s unlikely that any Spanish beach will experience more than 20 days of jellyfish disturbance over the summer, with occurrences not lasting more than three consecutive days at any given beach.

As the Mediterranean coasts brace for a typical jellyfish season in July, August, and September, tourists and locals alike are advised to stay informed but not alarmed.