Environmental Engineering Reference
In-Depth Information
FIGURE 9.6
Spread of zebra mussels
(Dreissena polymorpha)
in the United States from
1988 to 2000. Dark dots are sites where the mussels have been found. States and provinces
where they have been found are shaded. The mussels started in the Great Lakes and have
spread through the Mississippi drainage (images courtesy of the U.S. Geological Survey).
FIGURE 9.7
Zebra mussels attached to a rock. The mussels have been cleared from a por-
tion to reveal the dense sediment that accumulates at the base of the shells (photograph cour-
tesy of David Strayer).
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