The Columbian (Clark County, Washington) summarizes the efforts and costs associated with zebra muscle clean-up:
The non-native bivalve has proliferated in the Great Lakes and Mississippi River, costing more than $1 billion to remove from clogged irrigation pipes. Scientists believe the filter-feeder has fundamentally altered the environment by devouring zooplankton that forms the bottom of the food chain.
Researchers noted that the rate of zebra mussel expansion in the Midwest has slowed considerably since the mid-1990s. While boat-inspection programs and public education may be playing a role, the scientists at Oregon State hypothesized there might be something else to it.
So they examined calcium levels in the water.
“That’s what they make their shells out of,” said Thom Whittier, a faculty research assistant at Oregon State who wrote the study with three other researchers.
Tabulating water-sampling data from 3,000 river sites across the country, the OSU scientists drew up the first broad-scale map documenting the relative risk of zebra mussel infestation nationwide. They concluded that relatively high calcium concentrations in the water correlated strongly with the presence of the Asian freshwater mussels, while rivers with relatively low concentrations had a low risk of infestation.