Marine ecosystems threatened by soaring temperatures in the Mediterranean Sea

Rising temperatures in the Mediterranean Sea are attracting new species of fish.

Since the start of summer 2022, sea temperatures in the region have risen 5°C above average for this time of year. The successive heat waves that rage in France reinforce this phenomenon.

Holidaymakers and divers in Hyères, southern France, enjoy 27C waters and unusual sightings of tropical species such as barracudas, wrasse, triggerfish and turtles – commonly found in the Red Sea in Egypt.

According to diving instructor Mickael Youssouf, he has never seen more fish in this region in his 20-year career.

“For us, as professionals, it’s great for all of our customers, but in the long run I think it will have environmental consequences,” he says.

How will rising sea temperatures affect marine life?

Although divers appreciate new visitors, the rising temperatures are not good news. The spectacle risks having a devastating effect on the marine ecosystem.

Experts fear the arrival of invasive alien species, which could threaten food supplies and attack native marine life. invasive algaemeanwhile, could suffocate the locals corals and reduce water oxygenation.

“These species could be insatiable herbivores, or carnivores too, that will devour a lot of fish. It could also be invasive algae that will completely change our ecosystem,” explains Sandrine Ruitton, teacher and researcher at the Mediterranean Institute of Oceanography.

Species that can emigrate are likely to move to cooler habitatswhile those left behind may struggle to survive.

How do invasive species reach the Mediterranean Sea?

Non-native fish species are introduced to new environments in a variety of ways, but the main culprit is human activity.

In some cases, small organisms attach themselves to commercial or trading vessels. Many invasive fish species enter the Mediterranean Sea through the Suez Canal, a man-made waterway that connects to the Red Sea.

Until 2015, an area with high salinity served as a natural barrier between the two seas. When the channel was widened and deepened, this barrier was removed, allowing invasive species to pass through.

This, combined with rising sea temperatures, has led to an increase in non-native species in the Mediterranean Sea.