The Western Mediterranean to hold a wave of heat in the sea

Of those temperatures on the water 4 to 5°C higher than average endangers the biodiversity. The east coast of Corsica is one of the epicenters of an event that worries scientists. The frequency of these heat strokes at MEDITERRANEAN has doubled since the 1980s.

“A massive marine heat wave”, affected the western Mediterranean since the end of May, with temperatures “amazing” higher than “4 to 5 degrees” to normal, threatening the marine ecosystem, according to experts on climate change in this sea.

READ ALSO: The Mediterranean victim of pollution and climate change

“This great marine heat wave started at the end of May in the Ligurian Sea” lies between Italy and northern Corsica, then continues “in June in the Gulf of Taranto”, in the south-east of Italy, lined up Karina Von Schuckmann, German oceanographer at Mercator Ocean International. This non-profit organization based in Toulouse brings together the main institutions specializing in oceanography from France, Italy, Spain, Great Britain and Norway and pilots the European ocean monitoring service, the Copernicus Marine Service (CMEMS). .

In July, “from the Balearic Sea to Sardinia, as well as to the east of Corsica and throughout the Tyrrhenian Sea (between Sicily and Corsica), we have observed above (…) appreciated exceptional temperatures between 28 and 30 degrees Celsius “ that is “higher than normal, in the range of + 4 to + 5 ° C”, added to the organization.

If for those who bathe, there are many around this sea that is one of the main tourist destinations in the world, these temperatures seem wonderful, they are concerned with scientists and environmentalists.

This marine heat wave can really change the fauna and flora, leading to “migration of species” towards cooler water, possibly “mass mortality of species” yes “decreasing” in some and “the face of the news”, said Karina Von Schuckmann who is also one of the authors of the reports of the UN Group of Experts on climate. With increasing socio-economic effects, especially in fishing, he underlined.

Mass mortality of the species

“In the Mediterranean, after episodes of ocean heat waves in 1999, 2003 and 2006, many cases of mass mortality of species, such as gorgonians, were observed. (sometimes called bark corals, editor’s note) or posidonia”, says a report by the National Center for Scientific Research published in October 2020.

For Charles-François Boudouresque, professor of marine ecology at Aix-Marseille University, and member of the scientific council of the Scandola and Bouches de Bonifacio nature reserves, its effects “hot sea wave” the “under study” and “we can predict a primary effect on fixed organisms such as gorgonians and red coral” with mortality “total or partial”.

READ ALSO: Mediterranean water temperature above average, 30°C recorded in Corsica

The fish like the color very much “The peacock wrasse or barracuda, which started moving north from the southern Mediterranean, is likely to be more abundant” in the western Mediterranean, says the scientist. “Species from the Red Sea entering the Eastern Mediterranean through the Suez Canal” also approaching the French shores, two cases that can be “will be a problem in five to ten years” : the rabbitfish and the giant Rhopilema jellyfish.

The first is “a rare herbivore” WHO “Danger of bypassing normal food chains”. Already outside of Lebanon, its proliferation in the western Mediterranean could threaten the algal forests that serve as nurseries for other fish.

The giant jellyfish causes severe stings that require hospitalization and the closure of beaches if they exist, lines Charles-François Boudouresque.

More regular and intense episodes

To fight against these ocean heat waves, “We must reduce greenhouse gas emissions” and “Even if we stop emissions now, the oceans, which store 90% of the Earth’s system heat, will continue to warm”explained Karina Von Schuckmann.

READ ALSO: Cruise ships: soon a low atmospheric emission zone in the Mediterranean?

These marine heat waves are here “doubled in frequency since the 1980s”, according to the IPCC report published in August 2021.

Between 2015 and 2019, “The Mediterranean has experienced (…) five consecutive years of mass species deaths” due to these ocean heat waves, also outlined in an article in a scientific journal Biology of Climate Change published on July 18.

“At least since 2003, they have become more regular and they will in the future have a longer duration, take more space in the sea and become more and more intense”, weakening a precious sea in terms of biodiversity, warns Karina Von Schuckmann.

Although the Mediterranean Sea covers less than 1% of the planet’s ocean surface, it is home to “18% of all known marine species”, initiated a report of the network of Mediterranean experts on climate change and has already presented “the highest proportion of threatened marine habitats in Europe”.

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