'Mediterranean lungs' in danger

Tunisian marine biologist Yassine Ramzi Sghaier inspects seagrass: he says plant protection is crucial for a country in advance

Tunisian marine biologist Yassine Ramzi Sghaier inspects seagrass: he says plant protection is crucial for a country already plagued by a severe economic crisis.

Below the Mediterranean off Tunisia, gently undulating green beach meadows provide vital marine habitats for the fishing fleets and an erosion buffer for the beaches on which the tourism industry depends.

More importantly, seagrass is such an important stockpile of carbon and a producer of oxygen – crucial to curbing the devastating effects of climate change – that the Mediterranean Wetlands Initiative (MedWet) calls it “the lungs of the sea”.

But just as human actions elsewhere destroy forests of trees on land, scientists warn that human activity drives the grass under the sea to destruction with speed – with terrible environmental and Financial consequences.

Seagrass, named Posidonia oceanica after the Greek sea god Poseidon, spans the Mediterranean seabed from Cyprus to Spain, absorbing carbon and dampening the acidity of the water.

“Posidonia oceanica … is one of the main sources of oxygen supplied to coastal waters“says MedWet, a 27-member regional intergovernmental network.

Tunisia on the North African coastline “has the largest meadows” of all – spread over 10,000 square kilometers (3,900 square kilometers), said marine ecologist Rym Zakhama-Sraieb, pointing to its central carbon capture role.

The underwater flowering plants absorb three times more blue carbon – the term used to describe the removal of carbon dioxide from the atmosphere of the ocean and coastal ecosystems – than a forest, and they can store it for thousands of years, she said.

A Tunisian fisherman calls at the port of Ghar el-Melh;  fisheries make up 13 percent of Tunisia's GDP, and almost 40 percent of it is d.

A Tunisian fisherman calls at the port of Ghar el-Melh; fisheries make up 13 percent of Tunisia’s GDP, and almost 40 percent of it takes place around salt marshes.

“We need Posidonia to capture a maximum of carbon,” Zakhama-Sraieb said.

But a dangerous cocktail of violent pollution, illegal fishing by using the bottom trawl that tears up the seagrass and a lack of understanding of its life-giving meaning is tantamount to its death.

‘The sea has been destroyed’

Seagrass grows to a depth of up to 50 meters (165 feet), providing shelter for fish and slowing down erosion of shorelines by breaking wave tumors that would otherwise damage sandy beaches which tourists like.

Tunisian marine biologist Yassine Ramzi Sghaier said the grass is crucial to a country already gripped by a severe economic crisis.

“All of Tunisia’s economic activity depends on Posidonia,” Sghaier said.

“It is the largest provider of jobs,” he claimed, noting that at least 150,000 people are directly involved in fishing and tens of thousands in The tourism industry.

Seagrass grows to a depth of up to 50 meters (165 feet) and provides critical shelter for fish

Seagrass grows to a depth of up to 50 meters (165 feet) and provides critical shelter for fish.

The destruction has been rapid and the replacement is slow. That aquatic plantalso known as Neptune grass, grows less than five inches a year.

Areas of salt marshes have been cut by more than half in the Gulf of Gabes, a large area on the east coast of Tunisia, Sghaier said, with a 2010 study blaming excessive fishing and pollution.

Posidonia and a host of marine species once thrived there, but since the 1970s, phosphate factories have dumped chemicals into the ocean, causing more damage to the ecosystem.

Seagrass serves as an important shelter for fish to breed, feed and shelter.

Fishing accounts for 13 percent of Tunisia’s GDP, and almost 40 percent of it takes place around salt marshes – and fishermen describe stocks that plunge.

“The sea has been destroyed,” said Mazen Magdiche, throwing his nets out of the port of Monastir. “Chemicals are being dumped everywhere.”

Tunisia

Map of Tunisia.

Magdiche calculates that his catch is three times less than 25 years ago, but said he had little alternative income.

“There are fewer and fewer fish,” he said.

“You are not looking out for the interests of the sea, but to feed your children,” he added.

‘Disaster’

Nearly 70 percent of the Tunisian population lives on 1,400 kilometers (almost 900 miles) of coastline, and for many, Posidonia is considered pure waste.

When seagrass is washed up on land, it mixes with sand and forms large banks that protect the coastline from swells and waves, experts say.

But sometimes bulldozers are used to “clean” the beaches, contributing to the acceleration of coastal erosion, with about 44 percent of the beaches already at risk of being washed away.

“We are helping to make beaches disappear by removing the (seagrass) banks,” said Ahmed Ben Hmida, of Tunisia’s Coastal Protection and Development Agency.

  • Marine ecologist Rym Zakhama-Sraieb (left) emphasizes the critical carbon capture role that the marine facility has for the heated planet

    Marine ecologist Rym Zakhama-Sraieb (left) emphasizes the critical carbon capture role that the marine facility has for the heated planet.

  • Beaches are a key asset for tourism, which gave Tunisia a record 14 percent of GDP in 2019 - and seagrass provides

    Beaches are a key asset for tourism, which gave Tunisia a record 14 percent of GDP in 2019 – and seagrass provides an important erosion buffer for them.

Beaches are a key asset for tourism, which provided Tunisia with a record 14 percent of GDP in 2019 and livelihoods for up to two million people – one-sixth of the population.

The aquatic plant also improves water quality, making the beaches more attractive to tourists, Zakhama-Sraieb said.

Ben Hmida said the creation of four protected sea zones could help Posidonia, but that action was needed on a much broader scale.

“If nothing is done to protect the entire Tunisian Posidonia, it will be a disaster,” he said.


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© 2022 AFP

Citation: ‘Mediterranean lungs’ in danger (2022, 2 May) retrieved 18 July 2022 from https://phys.org/news/2022-05-lungs-mediterranean.html

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