I am very much hoping, Micaela, that you are learning to understand "newpaper-ese". That is a form of headline writing intended to capture your interest and which, at the same time, is often a number of degrees twisted away from reality. With some media you would be lucky if this topic even glances upon either molluscs, waterways or even the UK. Fortunately, my integrity does not permit such distortions (though I still hope to capture your interest).
The quagga mussel (Dreissena rostriformis bugensis) (pictured above) is a small freshwater bivalve mollusc. They are indigenous to the Dneiper River drainage of Ukraine and Ponto-Caspian Sea, and were named in 1897 by Andrusov after discovery in 1890 within the Bug River. The quagga was first sighted in the North American Great Lakes in September 1989 but was at first thought to be a zebra mussel (Dreissena polymorpha). In August 1991 it was differentiated as a distinct species, and was named after an extinct African relative of the zebra. Introduction into the Great Lakes is thought to have been as a result of ballast water discharge from transoceanic ships. Since introduction, the quagga has spread rapidly throughout the Great Lakes & North American rivers (it cannot tolerate salt-water greater than 5ppt, nor temperatures greater than 32°C), and is still spreading (a reservoir in New Mexico tested positive in 2011).
So why is it dangerous?
There are 2 + 1 reasons:-
So, Quagga and zebra mussels have now spread to 29 states in the USA, and engineers there have found that there is no effective eradication method once they have been established in a reservoir. In just one example, quagga have been flourishing in Lake Mead, Nevada (formed by the Hoover dam), since 2007 and there are now trillions of them. Engineers are working to stop them colonising the dam’s turbines and blocking the pipes which supply water to Las Vegas.
Now, as the comedy genius Mel Brooks pointed out via his 2,000 year old man, the definitions of Comedy & Tragedy are:-
...so we now need to report that the Wildfowl and Wetland Trust (WWT) has said that quagga mussels have been discovered at Wraysbury reservoir, which is near Heathrow Airport. The WWT is concerned that the London Wetland Centre (below), which is downstream from Wraysbury, could be ‘devastated’ by the mussel.
--------- Alex Kemp