In the south of Italy, between the remains of heavy industry and the quiet waters of a forgotten coastal basin, the Mar Piccolo concentrates decades of invisible pollution. Long exploited for its marine riches, this semi-fermed body of water has become one of the most significant symbols of environmental contamination in the Mediterranean. Today, researchers are testing an unconventional method there, where the roots of certain trees could replace the excavators and relaunch an ecosystem that was believed to be irreparably lost.
The idea dates back to the 1990s, when researchers from Rutgers have shown that certain plants, such as mustard seeds, could extract heavy metals from contaminated soils, especially around Chernobyl. Since then, the method has evolved, mobilizing species such as poplars, sunflowers or even algae tolerant with salt. In the case of Mar Piccolo, researchers rely on a poplar variety capable of degrading PCBs via its root system. This clone, says Monviso, has already been successfully tested on polluted terrain in Taranto.
The team led by the geologist Vito Felice Uricchio now wants to apply this model to the first Mari Piccolo basin, the most contaminated. In 2024, after more than a year of waiting, the project finally obtained the green light from the Italian Ministry of the Environment. It remains to unlock funding. Of the 500 million euros estimated necessary for the depollution of Taranto, only 52 million are now available, as reported by the BBC.
Mar Piccolo, a threatened but resilient ecosystem
On the surface, nothing suggests the complexity of the Mar Piccolo. This semi-fermized body of water, connected to the Ionian Sea by two channels, has long been a natural nursery for taranto mussels. Water is continuously powered by underwater sources called Citri, which maintain stable temperatures between 15 and 18 ° C. Thanks to these ideal conditions, up to 60,000 tonnes of molds were produced each year in the early 2000s.
But under this apparent tranquility, the sediments betray a story of chronic contamination. A scientific study published in Nature Scientific Reports highlighted the persistent presence of heavy metals such as mercury, lead or zinc, as well as hydrocarbons and organic pollutants such as PCB. These contaminants are concentrated in the superficial layers of the seabed, seriously affecting mussels, particularly sensitive filtering organisms. In 2011, their concentrations of dioxins and PCB crossed European thresholds, resulting in a temporary ban on culture.
The survey also revealed that certain pollutants are found up to three meters deep, made mobile by the furniture and organic texture of the sediments. This is where the difficulty lies: pollution is buried but always active, likely to go up in the event of a stir or poorly controlled work.
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Traditionally, the depollution of a site implies the excavation of soiled land and then their transportation in a landfill. An expensive, energy -consuming, and destructive solution. In a place as fragile as the Mar Piccolo, this method could worsen the damage. Phytoremediation, conversely, acts gently, at the rate of plant growth. It makes it possible to stabilize the floors, to avoid flights of toxic dust, and to offer a second life to land long considered to be lost.
But this technique is not always enough alone. According to Werther Guidi Nissim, professor at the University of Milano-Bicocca, the processing times are long and the efficiency varies according to pollutants. For organic compounds, a few years may be enough. For some heavy metals, it will sometimes take decades, even centuries. The interest of phytoremediation therefore lies in its complementarity with other methods, such as targeted excavation or the installation of underground barriers.
Despite its limits, this approach embodies a new philosophy: repairing rather than eraser. Integrate nature into depollution strategies rather than opposing it to industry. She also recalls that behind each ecological strategy, there are human issues. In Taranto, the safeguarding of the Mar Piccolo, it is not only an environmental business, but a question of survival for the families of mytlicultors, deprived of their livelihood for too long.
