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ENVIRONMENT

Minnows blamed for algae-filled French and Spanish lakes

Perched 1,800 metres (about 6,000 feet) near France's border with Spain lies the emerald Areau lake - whose colour experts blame on minnows used by anglers as live bait.

Minnows
Experts blame the green colour of some French and Spanish lakes on minnows used by anglers as live bait. Pictured are small fish used as fresh bait. Photo by Clay Banks on Unsplash

“When one sees these fish in the mountain lakes, we see a disturbed ecosystem,” said Adeline Loyau, a biologist and researcher at the National Polytechnic Institute (INP) in the southern French city of Toulouse.

These tiny fish, less than 10 centimetres long, are used as live bait.

But some managed to escape the hooks and have thrived, devouring amphibians, insects and zooplankton – “microscopic crustaceans whose role is to devour algae and keep the water crystal clear and very pure”, Loyau told AFP.

When the lake became green “it meant the algae won”, said Dirk Schmeller, a professor specialising in mountain ecology at the INP.

But the abundance of algae in the once clear waters is not only due to this, and several other issues are being examined.

‘Cocktail of factors’

“There are a cocktail of factors,” said Didier Galop, head of research at the National Scientific Research Centre (CNRS) who specialises in the history and geography of the environment.

The growing concentration of herds of cattle around these lakes means an increase of manure spewing nutrients into the water and make it a breeding ground for algae.

Others say higher temperatures due to global warming is exacerbating the problem.

But some say the greening of the lakes is not necessarily alarming.

“There are also lakes that are very blue but have zero biodiversity,” Galop said.

Schmeller and Loyau however said green lakes were becoming more and more common in the region.

“We even have hikers who sometimes come 30 years later” and notice this, Loyau said.

Diverse laws

On the other side of the Pyrenees in Spain, green lakes have been observed since 2011 by Spanish researchers and a programme was launched three years later to get rid of the minnows with nets and electrical techniques.

In 2018, France’s National Pyrenees Park copied the Spanish initiative but they found that the fish had been reintroduced by anglers.

Some highlight the need to educate fishermen.

Sebastien Delmas, the head of an association grouping anglers’ groups from the French Pyrenees, said local laws needed to be harmonised to outlaw live bait.

But he emphasised that other species like trout had their place in the lakes.

“The fish, they too are biodiversity. If they have been here for centuries, it’s because they fit in,” he said.

Delmas said tourism was also partly to blame, saying swimmers smeared with sunblock and mosquito repellents were also affecting the ecosystem.

“On a summer’s day, there may be three or four anglers around a lake but 300 swimmers. But one always blames the anglers,” he said.

Schmeller said there was a real need to eliminate pollutants around lakes, adding sardonically: “After that, there’s just climate change that needs to be tackled”.

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ENVIRONMENT

Mystery sonic boom rattles French Mediterranean island of Corsica

An unidentified sonic boom heard on the French island of Corsica and in Italy may have been a meteorite, experts have said.

Mystery sonic boom rattles French Mediterranean island of Corsica

Media in Corsica reported that the event occurred at around 4.30pm on Thursday.

It was also felt on the Italian island of Elba. The town of Campo nell’Elba said on its Facebook page that a nearby tracking station had, “captured a seismic, acoustic event felt by everyone” at that time. 

Tuscany regional government president Eugenio Giani initially said it was an earthquake, then backtracked after Italy’s National Institute of Geophysics and Volcanology (INGV) ruled one out.

The Italian Air Force told Giani it had nothing to do with the sonic boom.

“The type of event which caused the tremor, felt by many as an earthquake over the entire coast of Tuscany and in some inland areas, is currently unconfirmed,” Giani wrote on social media.

The region’s Geophysics Institute and the University of Florence said in a joint statement that whatever caused the boom was travelling at 400 miles per second.

“A meteorite entering the atmosphere seems the most likely and in line with the data registered”.

The Corriere della Sera daily quoted an unnamed person from Italy’s civil protection agency saying, “the impact would have been registered by seismographs. The most likely hypothesis is still an aeroplane”.

It is not the first time mysterious sonic booms have been registered on Elba, the Corriere della Sera said. Similar events in 2012, 2016 and 2023 have yet to be explained, it said.

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