Climate change is making the Mediterranean Sea warmer, and this is changing life under the water. Scientists say the sea heats up quickly. This is because it is nearly surrounded by land, and it cannot cool down like the open ocean. Its waters may become 2 to 6 degrees Celsius warmer by 2100.

The warmer water has become a comfortable home for new invasive fish. About 1,000 such species have been found, and 800 of them are already established. The lionfish, first seen in 2012, has spread quickly. Some are dangerous to people: the pufferfish is poisonous and can be deadly if eaten.

These changes are hurting both sea life and the people who depend on it. In some eastern areas, 93% of the small shellfish have disappeared. Along the Adriatic coast, most mussels have died because the water sometimes rose above 30 degrees Celsius. Fishers now catch fewer of the local fish that their customers love.

Scientists say the spread cannot be reversed, but the damage can still be reduced. Some invasive fish can be sold as food, while others are caught and destroyed. New species often travel inside ships, so cleaning these boats before they arrive can stop the problem. Even so, experts warn that many of these changes will not go away.