Wish You Were Here? Mediterranean Jellyfish Pose Problem
By Robin Pomeroy
FREGENE, Italy — Just when you thought it was safe to go back into the water …
In the 1975 blockbuster film “Jaws” it was a great white shark which kept holidaymakers off the beach. It is a less lethal but perhaps equally worrying menace that has closed stretches of the Mediterranean to swimmers this summer: jellyfish and seaweed.
Thousands of holidaymakers in parts of Italy and Spain have been told not to enter the water due to the threat of stings and poisoning from unusually large outbreaks of algae and jellyfish, which ecologists say are yet another symptom of global warming.
The seaweed, a toxic algae called ostreopsis ovata, has forced the closure of usually bustling beaches in Italy and caused considerable discomfort for those who entered the water.
Rosario Vizzini rushed his seven-year-old grandson Samuele to hospital when bright red welts appeared on his arms and legs after a day on the beach in northern Sicily. “The first thing they asked me was if he had been swimming, and in fact he had.”
The algae can cause skin irritations and respiratory problems and an outbreak caused a large stretch of beach near Rome to be closed for several days.
Just like in “Jaws,” local officials have been reluctant to accept the closure of beaches. In Fregene, a beach close to Rome, the mayor ignored the swimming ban and a possible 75-euro ($96) fine by taking to the water in an “I love Fregene” T-shirt, as a way to convince tourists his town was safe.
After the algae cleared, the coast was infested with jellyfish — a problem that has also plagued some of the most popular beaches in Spain this August.
Many scientists see the jellyfish and algae outbreaks as signs the Mediterranean is under stress, and even that it is becoming “tropicalized” — its ecology changing due to warmer temperatures and invasive species from hotter climes.
“We already knew that the Mediterranean has started to be invaded with tropical species and its biodiversity has changed,” said biologist Isabella Barone, from the University of Palermo.
“Most are not dangerous but this seaweed is as it releases toxins.”
Not a native species of the Mediterranean, the algae originates in the South Pacific, experts say, but it has been in the sea between Africa and Europe for decades, probably flushed out of the tanks of freight ships.
Raul Garcia, a fisheries expert at environmental group WWF, said the algal bloom — a concentration of the algae on the surface — has only become a problem in the last few years, possibly due to hotter summers.
Surface temperatures in the Mediterranean hit 29 degrees Celsius (84F) during August, according to the British Meteorological Office, compared to a long-term average of 24 to 27 Celsius (75 to 80F).
While the heat promotes jellyfish breeding and may change the blooming process of the algae, other factors have contributed.
Algal blooms are boosted by nitrate- and phosphate-rich pollution from farming and human waste, while jellyfish are enjoying a reduction in the number of their natural predators like loggerhead turtles and the bluefin tuna which have been devastated by over-fishing, Garcia said.
Reduced river flows during hotter summers might also lead to increased numbers of jellyfish near the shore as they are no longer kept out at sea by freshwater currents.
Research by the Mediterranean Science Commission found there are 500 species of fish, crustaceans and molluscs living in the Mediterranean which are not native.
It is not new for tropical species to enter the Mediterranean through the Suez Canal, the Straits of Gibraltar or via freight ships, but warmer water and weaker indigenous species mean they now colonise the sea, rather than dying off, Garcia said.
“When these organisms arrived in the Mediterranean they didn’t find a healthy ecosystem,” said Garcia. “They found they didn’t have enemies or competition.”
Changes to the ecology will increase over the coming decades if temperatures continue to increase as predicted by climate scientists who say global warming could increase the average global temperature by 1.4 to 5.8 degrees Celsius by 2100.
A report by British and Dutch climate researchers released last month estimated that by 2080 Mediterranean beaches will be too hot for tourists to bear and by then they will be holidaying in places like Ireland and Scandinavia.
Until then, holidaymakers who continue to brave the Mediterranean might want to bear in mind a little known fact about the sea: it is home to several species of shark, including the great white, the star of “Jaws.”