The Thau pond (illustration) -

N. Bonzom / Maxele Presse

  • According to a study, the ecosystems of eight out of ten Mediterranean lagoons are threatened by a high concentration of pesticides.

  • The pond of Gold is the most threatened lagoon, in front of the Ayrolle and the Méjean.

  • In each lagoon, between 15 and 39 pesticides were found, including glyphosate.

    A fatal cocktail for the animals and plants of the lagoons.

On the Mediterranean rim, pesticides threaten the balance of the lagoons.

According to a study by the Rhône Méditerranée Corse water agency, Ifremer in Sète, which specializes in maritime scientific research, and the University of Bordeaux, 8 out of 10 ponds face an alarming concentration of chemical substances.

And if, for the past thirty years, metal or hydrocarbon pollution and the proliferation of algae have fallen, significantly improving the condition of Mediterranean ponds, this new threat is particularly worrying, according to the researchers.

The Gold Pond is the most threatened

But not all ponds are threatened in the same way.

As part of the study, samplers, able to detect pesticides present in the water, were immersed between 2017 and 2019 for three weeks, at three times of the year, in 10 lagoons: in the pond of Canet (Pyrénées-Orientales), those of Bages-Sigean, Ayrolle, and Palme (Aude), those of Thau, Vic, Méjean, and l'Or (Hérault), that of Berre (Bouches -du-Rhône), and that of Biguglia (Corsica).

Only Palme and Biguglia present a low risk linked to exposure to pesticides.

The pond of Gold is, on the other hand, the most threatened lagoon, in front of the Ayrolle and the Méjean.

In each lagoon, between 15 and 39 pesticides were found, including two herbicides, S-metolachlor and glyphosate.

A fatal cocktail for the animals and plants of the lagoons.

"Pesticides can see their effects add up and harm the functioning of these lagoon ecosystems and the organisms that live there: their reproduction, their development or their immunity", explains Dominique Munaron, researcher in environmental chemistry at the 'Ifremer.

For example, "diuron, a herbicide, modifies the structure of the oyster's DNA and even harms its offspring," notes Wilfried Sanchez, deputy scientific director at Ifremer.

The development of this mollusc is also disturbed by copper, which acts on some of its genes.

"

#ParoleDeScientifique 🎙️ |

Following the revelations of the #Obslag report, Theo is back with 3 questions to the Deputy Scientific Director of Ifremer.

Its objective: to understand the effects of #Pesticides on the marine environment @SauvonsLeau @univbordeaux


🔗 https://t.co/Xsx5E46UDz pic.twitter.com/YPux2gKrHZ

- Ifremer (@Ifremer_fr) November 4, 2020

Soon on other maritime facades

And even if we managed to lower the concentration of each substance to its threshold value, "the effect of cumulative pesticides would still entail a chronic risk for 84% of the samples taken as part of this study", explain the researchers.

It is new to apprehend this dangerous “accumulation” of numerous pesticides in lagoons.

"Before this study, the chemical state of these lagoons was considered" good "since none of the 22 priority pesticides monitored exceeded its threshold value, indicates Karine Bonacina, the regional director of the Rhône Méditerranée Corse water agency. .

This study changes our perspective.

It highlights the urgency of taking into account cocktails of pesticides and their effects on these natural environments.

"

This type of study will soon be carried out on the 10 Mediterranean lagoons, and could soon be launched on the other French seafronts.

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