• Toulouse researchers in mountain ecology have studied the chemical composition of the supposedly pure waters of eight high-altitude lakes in the Pyrenees.

  • They found there an astonishing “toxic cocktail” based on pesticides.

  • And in particular, sometimes, worrying concentrations of two molecules found in insecticides and which could threaten these paradise-like ecosystems.

After the microplastics found on the virgin peaks of the Pyrenees, here is the “toxic cocktail” in the waters that we thought were pure and clear from the high altitude lakes.

Dirk Schmeller and Adeline Loyau, two researchers from the Functional Ecology and Environment Laboratory in Toulouse*, are almost “sorry” to say it, but it is sometimes more prudent to take your water bottle on a hike than to rely on natural resources.

The study they have just published debunks a lot of heavenly clichés.

Their team surveyed the summits to place in eight lakes in the Pyrenees – in Ariège, Haute-Garonne or even in Béarn – “small silicone sheets” as a support to capture chemical molecules.

Raised twice, in the spring and in the summer, they delivered their worrying verdict.

“We looked for 460 molecules and we found 141, a massive chemical diversity,” says Dirk Schmeller.

There are herbicides in particular, probably carried by the winds from lower altitude crops.

If most of the concentrations are low, the two scientists warn of the presence of two “very toxic” molecules: diazinon and permethrin,

Two deadly molecules for microorganisms

Concerning this duo of chemical molecules, deadly for water spiders for example, the levels found in certain lakes, such as the Ayès pond in the Ariège Couserans, far exceed the "chronic toxicity" allowed.

Moreover, the team noted that the more the presence of the two chemical molecules increases, the more that of the microscopic crustaceans decreases.

“However, these micro-organisms are an essential link in the ecosystem of these lakes.

Their disappearance, in addition to the effects of global warming, can lead to really very significant cascading effects such as the proliferation of toxic algae”, warns Adeline Loyau.

The two researchers think that the two insecticide molecules are disseminated by the cattle in the summer pastures, over the baths of the cattle in hot weather and the gulps taken by the ewes, their feet in the water.

They wrote to a pastoral association to share the results of the study.

And already suggest “to space out the treatment of the animals and the date of going up to the mountain pastures more far apart”.

“That would already be a good thing”, considers Dirk Schmeller.

* A laboratory under the supervision of INP/Paul-Sabatier University/CNRS

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  • Occitania

  • Pyrenees

  • Pollution

  • Planet

  • Toulouse

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