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W. Mediterranean hit by ‘exceptional’ heatwave: experts

Oceanographers say static marine life, such as plants and coral, will be hardest hit by ocean heatwaves

Oceanographers say static marine life, such as plants and coral, will be hardest hit by ocean heat waves.

An “exceptional” heat wave at sea is gripping the western Mediterranean with surface temperatures up to five degrees Celsius (41 degrees Fahrenheit) hotter than average, according to experts contacted AFP.

While the record-breaking heat wave that has devastated northern Europe and Britain this month has eased, experts said continued hotter-than-normal temperatures in the Mediterranean were threatening the entire marine ecosystem.

“This massive offshore heatwave started in May in the Ligurian Sea” between Corsica and Italy, says Karina von Schuckmann, oceanographer at the nonprofit research group Mercator Ocean International.

It then spread to the Gulf of Taranto in the Ionian Sea, she said.

By July, the heat wave had engulfed the Balearic Islands, Sardinia and the Tyrrhenian Sea.

“The surface temperature anomaly map shows higher than normal values, on the order of +4 to +5C from eastern Balearic Islands to eastern Corsica,” Mercator said in a statement.

While people may find the warmer water temperatures enjoyable in the tourist hot spots of the western Mediterranean, the group warned that “ocean warming is affecting the entire ecosystem.”

“It is important to be aware of the potential impacts on the local fauna and flora, as well as the occurrence of extreme weather events that could lead to natural disasters,” it said.

Von Schuckmann said unusually warm temperatures could cause irreversible migration for some species and “mass die-offs” for others.

She noted knock-on effects for industries such as tourism and fishing, which depend on favorable water conditions.

According to the UN climate science body, the frequency of marine heat waves has already doubled worldwide since 1980.

Die-off, invasive species

Although the Mediterranean Sea accounts for only one percent of the Earth’s ocean surface, it contains nearly 20 percent of all known marine species.

A study published this month in the journal Global Change Biology found that the Mediterranean had experienced five consecutive years of mass deaths between 2015-2019.

The French CNRS research center has noted that the marine heatwaves in 1999, 2003 and 2006 caused mass die-offs for some species, most notably the posidonia, a genus of flowering plants.

“We can predict that the biggest impact will be on solid organisms such as plants or corals,” said Charles-Francois Boudouresque, a marine ecologist at the University of Aix-Marseille.

However, some species of fish, such as the barracuda, may become more abundant in the warming northern waters of the Mediterranean.

Boudouresque said some species coming through the Suez Canal from the Red Sea could become problematic “within five to 10 years.”

These include the rhopilema – a herbivorous jellyfish – and the rabbit fish, which Boudouresque described as “extremely greedy”.

Its appearance in western waters, already abundant in the eastern Mediterranean, is said to threaten the algal forests that serve as nurseries for numerous fish species.

Rhopilema can also sting swimmers with enough severity to require hospital treatment.

Because there is little government can do once a heat wave hits the sea, Von Schuckmann said the best course of action is to reduce greenhouse gas emissions that contribute to warming.

“Even if we stopped emitting today, the oceans, which contain 90 percent of the Earth’s heat, will continue to warm,” she said.

“Since at least 2003 (marine heat waves) they have become more common and in the future they will last longer, cover more seas and be more intense and severe,” said von Schuckmann.

Mass deaths related to heatwaves at sea could become the new norm in the Mediterranean

© 2022 AFP

Quote: W. Mediterranean hit by ‘exceptional’ heatwave: experts (2022, July 28) retrieved July 28, 2022 from https://phys.org/news/2022-07-mediterranean-exceptional-heatwave-experts.html

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