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Attack: A
zebra mussel feeds by sucking in water. The
mussel strains out tiny plants and animals as the water passes from its
body. Zebra mussels are such good strainers, they've actually made waters
around them much cleaner. Sounds good, right? Wrong! The tiny bits of food
feasted on by zebra mussels are the first link in many freshwater food chains.
So, the aliens are stealing food from native animals like clams. The natives
end up starving. And, because the water is cleaner, light can travel deeper
below the surface. As a result, certain plants now grow in places that used
to be too dark for them. This may cause problems for plants and animals
already living in these areas. Zebra mussels are also good at making more
zebra mussels: in some places, 70,000 of these critters can be found crammed
into a space about as big as your bed! With so many of them around, native
animals are gobbling them up. But this has biologists worried. The mussels'
bodies store unusually high amounts of toxins. These toxins can harm animals
that eat them. The scaup is one duck that eats zebra mussels. Scaup numbers
are falling, and biologists wonder if the mussels might be to blame. Zebra
mussels cause their share of trouble for people, too. They clog pipes that
pull water from lakes and rivers for human use. The mussels must be scraped
off the pipes, as well as boats, docks and other structures. This costs
millions of dollars each year. |
