Water temperatures in the northwestern Mediterranean are increasing much faster than global averages, threatening the survival of several species, French researchers said.
Weekly water temperature readings by researchers at the Villefranche-sur-Mer oceanography laboratory have shown that Mediterranean surface water temperatures have increased by 0.7 degree between 2007 and 2015.
The researchers, who believe their findings apply to an area that includes Spain, France and Italy, also said in a note summarizing their study that the water's acidity has increased by nearly 7 percent.
"The acidification and warming up of the water are due to carbon dioxide emissions from human activities," French CNRS researcher Jean-Pierre Gattuso told Reuters.
He added that about a quarter of mankind's carbon dioxide emissions are absorbed by the oceans, making the water more acidic.
Gattuso said that plankton tend to migrate north in order to maintain an optimum temperature, but that is not possible in the Mediterranean, which is connected to the Atlantic Ocean only via the narrow Strait of Gibraltar.
"It's a dead-end here, so species could disappear," Gattuso said, noting a particular threat to the posidonia oceanica seagrass, known locally as Mediterranean tapeweed, which produces oxygen and forms an important fish habitat.
He said that at the same time, more grouper and barracuda had been seen in the Mediterranean, as it becomes more like a subtropical sea.
Gattuso said the acidification would become a problem in a few decades for marine organisms that have a skeleton or a calcium shell, such as oysters, mollusks, snails and corals.
Mediterranean mussels, popular in restaurants, could disappear in 2100, he said.