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Menacing Mussels: Invasive Quagga Threaten UK

Oct 13, 2014 11:27 AM EDT

At the start of October, officials in the United Kingdom stumbled upon quagga mussels in southeast rivers, to their utter horror. This adds just one more invasive species to a growing, and spreading, list of creatures that threaten UK waters.

The discovery was made by Environment Agency teams carrying out routine water quality testing on River Wraysbury. The worrying mussel has subsequently been found in the nearby Wraysbury reservoir too.

And while the tiny shellfish seems unassuming, officials are no strangers to the troubles it can cause, proving just as bad or worse than previous invasions of zebra mussels - an invasion that is also playing out in the United States.

"The quagga mussel is a highly invasive non-native species, affecting water quality and clogging up pipes," Sarah Chare, deputy director of fisheries and biodiversity at the Environment Agency, said in a statement. "We are monitoring the extent of its spread and working closely with partners to ensure they are aware of it."

She added that invasive species like the mussel cost the UK economy more than an estimated £1.8 billion ($2.9 billion) every year.

Without any natural predators in these vulnerable waters, the mussels can take full advantage of their incredible reproductive properties, creating up to one million eggs per mussel per year.

The quagga is also smaller than most freshwater mussels found on UK riverbeds, meaning that it can literally piggyback these slower-breeding relatives. It steals not only nutrients from these other species but shade too, aggressively filtering out blue-green algae and clearing waters so that more sunlight reaches the riverbed's more vulnerable inhabitants.

David Aldridge, an expert at the University of Cambridge and the co-author of a new study of the UK's invasive species, says that the quagga is the invader the United Kingdom should fear most because it actually supports other invaders, like predatory omnivorous shrimp. (Scroll to read on...)

His study, recently published in the Journal of Applied Ecology, details how a good number of Britain's invasive species, including the quagga mussel, are from the Ponto-Caspian region around Turkey and Ukraine.

The work shows how these species literally relocate their entire food chain after invading a new region, feeding off one another's waste and physically changing environments - like how the quagga clears murky waters.

"In some parts of Britain the freshwater community already looks more like the Caspian Sea," Aldridge explained in a Cambridge release. "The Norfolk Broads, for example, typically viewed as a wildlife haven, is actually dominated by Ponto-Caspian zebra mussels and killer shrimps in many places."

Through an in-depth analysis of all reported field and experimental interactions between the 23 most high-risk invasive Ponto-Caspian species, Aldridge and his colleagues were able to identify 157 different effects. A whopping 71 of those effects enabled positive reinforcement between invasive species.

"I suspect the arrival of the quagga, and its potential impacts and facilitation [for further invaders], shows we're at the start of a very slippery slope," the researcher told The Guardian. "The most cost-effective solution is to stop these things getting here, and that requires some policy changes."

Mark Owen, head of freshwater at the Angling Trust adds that practice of the "Check, Clean, Dry" approach is key to prevent further spreading, in which the larvae of quagga mussels are not visible to the naked eye, making drying a critical step in applying good biosecurity.

"It's vitally important that all water users, including anglers, take every possible precaution to stop this species spreading throughout the UK," he said. "Quagga mussels could do untold damage to freshwater and estuarine environments if they are allowed to spread which could have a significant impact on marine and freshwater fish stocks."

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