This is The Guardian.

Late last year, biodiversity reporter Phoebe Weston took a trip to Lake Geneva.

It's a beautiful alpine lake nestled in the west of Switzerland. You can see France

just the other side of the lake with the mountains dropping straight into it. In the December

chill, she headed out with a team of ecologists. We went out to a floating research station

and it was evening, the sun was set. It was really beautiful.

Everything looked completely normal, but below the surface, a total transformation has taken place.

This team of researchers pulled out these ropes, keeping the floating research station in place, and they were absolutely

caked in quagga mussels. And it looked like costume jewellery. One of the professors I was with

described it, like if you look under the surface of the lake, it looks like a meadow of quagga

mussels. They're absolutely everywhere.

These tiny, striped brown muscles are one of the planet's most potent invasive species.

One female can produce up to a million egg cells.

They can breed all year round and spawn in temperatures as low as 5 degrees Celsius. At Lake Geneva, they've been

found at record-breaking depths of 250 metres. Now, this is a pitch-black environment where there's

almost no oxygen and nothing else can really survive other than microbes. Each muscle can filter up to two litres of water a day, feeding on phytoplankton, the basis

of the lake's food chain, with cascading impacts up the entire food web and to the fishermen

who depend on it.

But the ubiquitous presence of the quagas is causing some unexpected problems too.

The Swiss Federal Technology Institute, or EPFL in Lausanne, is a research institute which in the 70s created what was a really innovative cooling system, which involved scooping very cold water deep out of Lake Geneva and then running it round the university building.

The muscles have clogged up the pipes like cholesterol in an artery.

The buildings are now struggling to stay cool in the summer,

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