In Tunisia, Posidonia seaweed is facing extinction

Posted on Monday, 02 May 2022 at 08:14

In Tunisia, there is a risk of disappearance of Posidonia, a seaweed on which fishing and tourism depend, and an important sector of the country’s economy, due to ignorance of its role, illegal fishing and pollution, which worries scientists.

“Tunisia has the largest seagrass swamp in the Mediterranean,” said Reem Zakhama Serib, a marine environment researcher in Tunisia, more than one million hectares.

These underwater forests, up to 50 meters deep, provide shelter for many species of fish.

The leaves of ‘posidonia oceanica’ also contribute to breaking up the waves and thus keeping the coast from drifting.

“The existence of all Tunisian economic activities depends on Posidonia, which is the largest provider of jobs in the country,” warns marine biologist Yassine Ramzy Sghir, citing in particular the fishing sectors (150,000 direct jobs) and tourism (in tens of thousands).

A bundle of leaves, rhizomes and rhizomes – creeping stems generally buried in the ground – Posidonia grows very slowly, less than five centimeters per year.

Grâce aux rhizomes, les herbiers stockent le carbone et produisent de l’oxygène, ce qui vaut à la posidonie d’être appelée “carbone bleu”, explique Mme Zakhama-Sraieb, soulignant qu’elle oxy produit 14 d à 20 litères Square meters.

– ‘Carbon cap’ –

According to the researcher, seagrass, which absorbs three times more carbon than the forest, can fix significant amounts over thousands of years.

“In the context of climate change, we need posidonia to capture as much carbon as possible,” agrees Yassin Ramzy Sghir, an expert in marine biology.

Due to a lack of resources, researchers cannot quantify the amount of weed destruction in Tunisia in recent years.

But they point to multiple causes in a country where nearly 70% of the population lives on 1,400 km of coastline: human activities, coastal development, illegal fishing, aquaculture farms built on seaweed…

Due to the ignorance of the general public and decision-makers, Posidonia “benches” washed on beaches, for example, are often considered waste.

Sometimes bulldozers are used to clear them, removing a lot of sand and speeding up erosion, according to researchers who say they fear nearly half of Tunisia’s beaches will disappear.

Even after stranded on the beach, Posidonia’s “benches” protect the coasts from swells. It also improves water quality and transparency, making swimming more attractive to tourists, recalls Dr. Reem.

In Tunisia, beaches are an important component of tourism, a sector that accounts for up to 14% of GDP by year. However, 44% of the country’s beaches are at risk of erosion due to sea level rise.

“We are helping the beaches disappear by removing the benches,” warns Ahmed bin Hamida, director of marine and coastal areas at the government authority for the protection and development of the coast (APAL).

– ‘A sea of ​​ruins’ –

According to scientists, nearly 40% of fishing activity also takes place in seagrass beds. A sector that represents 13% of Tunisia’s GDP.

A 2010 study reported a significant decline in seagrass beds in the Gulf of Gabes (southeast) due to illegal fishing (bottom trawling) and pollution.

Since the 1970s, chemical phosphate processing plants have dumped phosphate gypsum there. The result: less than 40% of the Posidonia meadows remain in this area, unfortunately Yassin Al-Saghir.

Even if he fishes to the north in Monastir (central east), Mazen Majdish is fishing three times as much as 25 years ago: “There are fewer and fewer in the shallow waters where there are posidonia.”

This atmospheric man has been made aware of the importance of posidonia but understands his colleagues, especially the “little fishermen by sarcasm”: “You do not seek the interests of the sea but to feed your children and your family.”

“The sea is destroyed,” says the fisherman today. “The chemicals are lying everywhere. Our sea has changed.”

But Ahmed bin Hamida of Abal wants to “preserve the hope of saving this treasure”, notably through “the forthcoming establishment of four marine and coastal protected areas: Galit Islands (North), Zimbra (Northeast), Quriyat (Northeast) and Kneis (East )”.

But he warns: “If nothing is done to protect all of Posidonia, we are headed toward a real catastrophe.”

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