With waters at 32C, Mediterranean tropicalization shifts into high gear

When Murat Draman made a scuba diving off the coasts of the South Turkish province of Antalya and saw the temperature in the depths pushed 30 ° C, this did not surprise him.

“We were at a depth of 30 meters (100 feet) this morning and the water was 29 ° C,” said Draman, a diving instructor in an area that knows with the rapid “tropicalization” of the Mediterranean Sea.

Encouraged by increasingly hot waters, hundreds of species from the Red Sea have moved through the Suez Canal and the eastern Mediterranean, disturbing ecosystems, according to scientists.

The threat is faced with the whole of the Mediterranean, one of the fastest seas, which this year saw its hottest June and July, figures from the Mercator Ocean International Research Center Show.

Draman, who remembers when the water temperatures were 25 ° C in August in the early 2000s, said he saw dozens of Red Sea species colonizing the clear waters of Antalya, where surface temperatures have reached almost 32 ° C this week.

The striking but very poisonous (pteroic miles) lion fish with its long spotted fins which measure approximately 26 centimeters (10 inches), is now comfortable in such warm temperatures and ravages in the local ecosystem.

“About ten years ago, we saw one or two. We are now talking about 15 or 20 per dive, even more than when we go to the Red Sea,” Draman told AFP.

“These are great predators. Small fish like gobbles suffer a lot, we barely see them.

‘A warning’

These invasive species disrupt ecosystems through the eastern Mediterranean, the hottest area of the sea and the most quickly warmed area, explained Professor Gil Rilov, a researcher at the Oceanographic and Limnological Research Institute (IOLR), which also gives lessons to Haifa University.

“The invasion started almost immediately after the Suez Canal opened in 1869,” he said.

“But now it warms up, and also (in 2015), the canals have become deeper and wider, so more and more new species are moving each year,” the marine biologist told AFP, admitting that newcomers could also be beneficial in waters that become too hot for native species.

And many of these species – which have become ubiquitous off the coast of Turkey, Lebanon and Israel – now moved further to the west, he said, pointing to Rabbitfish (Siganus Rivulatus) which recently colonized the waters of Malta, more than 1,700 kilometers (more than 1,000 miles) of the Canale Suez.

What is happening in the eastern Mediterranean, where many native species have already disappeared, “is a warning,” added Rilov, pointing to two possible causes for their disappearance: excessively hot waters and fierce competition with these invasive species.

“What is happening here will occur in five, 10 or 20 years in the north and west of the Mediterranean,” he predicted.

Last week, Mercator figures showed that the sea had recorded its warmest in July with an average surface temperature of 26.68 ° C – a figure which is disturbing experts.

“ No predators’

This “tropicalization” could also occur in the coming years by the Strait of Gibraltar at the end of the Mediterranean basin, according to a study published in the Proceedings of the National Academy of Sciences in April 2024.

In this document, the authors have warned that even in an intermediate climate scenario, warming of the Atlantic Ocean could see certain species migrate southern coasts of West Africa to the Western Mediterranean by 2050.

A more pessimistic scenario could even see the Mediterranean “completely tropicalized” by 2100, they warned.

Faced with such a threat, Draman said that invasive species should be kept as much as possible from protected sea zones “in order to preserve biodiversity”.

“It is clear that with the absence of Mediterranean predators, species such as lion fish are very comfortable here and their population increases from year to year,” he said.

“In the Red Sea, the lion fish has predators. There are sharks and barracudas. Here we have none of this.”

© 2025 AFP