These invasive mussel species have caused millions of dollars in damage and untold ecological damage, the researchers point out. When the veligers eventually settle out of the water column, they often attach in large numbers to all sorts of human structures, including water intakes which they quickly clog as well as boats, buoys, motors, and engine cooling systems.
They also attach to, and weigh down, native freshwater clams and mussels, crayfish and even large aquatic insects like larval dragonflies. When they attach to native clams and mussels, the researchers say, these invaded compete directly for food.
These mussels are extraordinarily prolific, Whitter said. A female zebra mussel may produce a million eggs a year, and when they establish a colony, they are hard to get rid of. They also filter huge volumes of water, and by consuming phytoplankton, they can dramatically change the aquatic food web of the lake, reservoir or river.
The research team which also includes Paul Ringold, an ecologist with the U.S. Environmental Protection Agency, and Sue Pierson, a geographer with Indus Corp. in Corvallis, Ore. used calcium concentration data from more than 3,000 river and stream sites across the contiguous U.S. for its study. Most of the reported occurrences of zebra and quagga mussels are in regions the researchers had classified as high-risk based on calcium levels.
Some sightings have occurred in low-risk areas, but these usually were in rivers that drain high-calcium regions. Ancient seabeds are high in calcium, the researchers say, while basaltic rock, like that found along much of the West Coast, has low calcium levels.
If there isnt enough calcium in the water it probably wont kill the mussels outright, Herlihy said, but they dont seem to grow well. And once theyre established, theyre horribly difficult to eradicate
|Contact: Thom Whittier|
Oregon State University