finance & economy

Posidonia: Tunisian-Italian project bodes well for restoration of endemic Mediterranean ecosystem

June 23, 2022

TAP)-They are often carried by the current in all directions forming in the shallow Mediterranean underwater clusters of green leafy waves, that look very pretty.

They are called Posidonia meadows (Posidoniaoceanica) after Poseidon, the Greek god of the sea, and are flowering plants that characterise the underwater Mediterranean just as the olive tree is the symbol of the continental Mediterranean.

They are also the founding species of one of the most important ecosystems of the Mediterranean Sea, confirming it as a biodiversity hotspot.

However, these endemic underwater forests of the Mediterranean, which provide food and shelter for other species, stabilise the seabed and help counteract marine erosion, are now endangered because of their sensitivity to human excesses (pollution, overfishing, etc.), biological invasions and climate change.

Their growth requires a lot of time and their destruction leaves a scar in the marine ecosystem which recovers in several years.

For this reason, it is now necessary to protect these 'natural allies' of man and make the most of their multiple ecological and economic services.

For the first time, a Posidonia re-planting project in Tunisia

To save these endangered marine ecosystems in Tunisia, six Tunisian and Italian partners from the scientific, research and teaching communities are collaborating to restore Posidonia seagrass beds under a two-year partnership project called Innovative Methodologies and Reinforcement Actions to Protect the Mediterranean Environment 'MIAREM,' launched in October 2021.

The initiative consists in re-planting through a system made of a biodegradable plastic material to ensure the rooting process of the cuttings, one hectare plots of posidonia in pre-identified areas between Bizerte and Monastir.

'Once the area is selected and restored, it will be monitored for a year using innovative techniques developed by Italian partners,' Dr. Fatma Trabelsi from the Mjez El Bab Higher School of Engineering explained.

The project, conducted under the ENI Cross-Border Cooperation Programme Italy-Tunisia 2014-2020 which is co-funded by the European Union (EU), also seeks to save Posidonia meadows as endemic ecosystems of the Mediterranean and major atmospheric carbon sinks in the short and longer term.

For the Coastal Protection and Development Agency (APAL), Tunisia should move from the watching and monitoring stage to restoration solutions for possible generalisation to all the Tunisian coasts.

'So far, we have merely monitored the decline of Posidonia meadows on the Tunisian coast, but through this project we will move on to solutions,' senior engineer and director of coastal development and rehabilitation at APAL Mehdi Ben Haj pointed out to TAP.

'This is the first time that a Posidonia meadow repopulation project will be conducted in Tunisia after a model experiment in Italy. I consider it revolutionary and it will benefit the entire Mediterranean submarine ecosystem,' he added enthusiastically.

It is also a first for APAL, which usually intervenes to protect the coastline and the public maritime domain against encroachment and illegal occupation, and carries out other actions without touching the underwater ecosystems, underlined Ben Haj during a meeting to present the 'MIAREM' project, organised at the Tunis City of Sciences.

Natural allies in combating climate change

Although they only cover between 25,000 and 50,000 km2 of the Mediterranean coastal areas, corresponding to 25% of the sea bottom according to medwet.org, Posidonia meadows play a vital role in storing carbon.

Thanks to the mat formed by the intertwining of rhizomes and roots compacted by sediments, they capture carbon at a time when humanity is waging an almost desperate battle to reduce CO2 emissions and keep global warming below 2°C.

The Mediterranean population of Posidonia produces 14 to 20 litres of oxygen per square metre every day, according to a study by the Mediterranean Institute for Advanced Research (IMEDEA) and the BBVA Foundation, a Madrid-based organisation working to preserve biodiversity.

It also plays a crucial role in combating erosion by stabilising the seabed, damping swell and waves and depositing sediments that form wave breakers along the shoreline.

In addition to its role as the green lung of the Mediterranean, these seagrass beds contain between 20 and 25% of fauna and flora species.

Some fish, such as the saupe, eat almost exclusively posidonia and on the matte lives a great diversity of invertebrates and even the dead leaves of posidonia on the edges of the beaches serve as a habitat for a specific fauna.

Furthermore, according to an international study published in the journal Nature Geosciences: https://www.nature.com/articles/s41598-017-03006-2.pdf, seagrass beds are necessary to reduce global warming, as they capture three times more carbon than a temperate or tropical forest.

No laws to protect Posidonia meadows in Tunisia!

In Tunisia, as elsewhere in the Mediterranean, Posidonia meadows, called in Tunisian dialect 'Dhrii,' have suffered a major decline in recent years due mainly to illegal fishing (trawling on the meadows), competition with introduced species, coastal aquaculture and the pressure of chemical pollution.

According to APAL, this decline is particularly noticeable on the various coasts, especially in the Gulf of Gabes, which is known for its tiger grass beds.

However, to date, no specific protection law has targeted these underwater ecosystems, which are present on almost all Tunisian coasts (Sousse, Kelibia, Hammamet, Gulf of Gabes, Monastir, Bizerte), whereas in other countries, including France, they have been protected as 'remarkable or specific landscapes of the natural and cultural heritage of the coastline' since September 1989 (decree).

However, the Barcelona Convention commits the contracting parties, including Tunisia, to 'take all the appropriate measures to protect the populations of Posidonia oceanica and all other marine phanerogams (marine plants with flowers and seeds), which are the essential flora of the Mediterranean coastal system.

It also stipulates the control and regulation of trawling and other activities leading to the destruction of Posidonia and all other marine phanerogams.

The 'MIAREM' project bodes well for the restoration of these ecosystems.

The project is initiated by the Regional Environmental Protection of Sicily (ARPA Sicily) and six partners, including three Tunisians: Tunis Faculty of Sciences (FST), Higher Institute of Biotechnology (ISBST) and the Mdjez Elbab Higher School of Engineering, and three Italian: The University of Catania (UNI CT), Mediterraneaneo Consulting srl (MED CONS) and FLAG Golfi di Castellammare e Carini.

Other partners are also involved, notably the APAL, the 'Association Notre Grand Bleu' (NGB) and the 'Association de Développement et de préservation de l'Environnement et du Patrimoine ' (ADEP).

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