The discovery of invasive zebra mussels snuggled in balls of moss in a Seattle pet store followed by a second pet store in Florida has wildlife officials scrambling to contain what could be a new destructive breach in the nation’s decades old fight to control the mussels.
The freshwater mollusks first appeared in the Great Lakes in the 1990s after escaping through ballast water.
They have since spread, from Texas to New York, carving a path of destruction.
“The problem with the moss balls is it’s a vector we just weren't prepared for,” said Wesley Daniel, a fisheries biologist for the U.S. Geological Survey, who tracks invasive species as part of a national monitoring network. “Nobody had thought that this [could] potentially be a source of that new invasion.”
Zebra mussels, native to freshwater lakes in Russia and the Ukraine, have no predators in the U.S., grow rapidly, gobble up huge amounts of food in water and can quickly overwhelm native species.
“It only takes a few of them to establish a new population. And so they've spread down the Mississippi River. They're also found in the Ohio River. They’re going up the Missouri [River],” Daniel said.
They’ve also clogged pipes at power plants and other facilities, blanketed piers and coated boats and motor props.
The worry now, Daniel said, is aquarium owners oblivious to mussels hidden in moss used to decorate and filter tanks who dump water, and unwittingly spread the mussels.
“The biggest concern is people not recognizing the threat,” he said.
Daniel, who is based in Gainesville, first spotted the Seattle pet shop report in the database he manages in February. The report caught his attention because of its source — a retail outlet. No photographs were included in the online report, so he called the shop and asked for an image to confirm the species of mollusk.
Once confirmed last week, Daniel contacted invasive species coordinators at USGS and the U.S. Fish and Wildlife Service to begin coordinating efforts to contain the spread in Washington state and the northwest.
He also worried that the chain store where the moss ball was reported could already be fueling a larger spread, so he visited his local store in Gainesville.
“The very first ball that I picked up had a zebra mussel on it,” Daniel said.
The mussels have since been confirmed in moss balls in 21 states. The agencies are working with the U.S. Department of Agriculture, state wildlife agencies and the pet industry to pull the moss balls, which are also sold on Amazon and are widely available online.
If people have recently purchased the moss balls, Daniel said they should freeze or boil the balls to kill the mussels before throwing them away.
“Please don't throw them outside just for the off chance that they might wash in a rainstorm into a local water body,” he said.
Although the U.S. has been battling the mussels for more than three decades, Daniel said scientists are still searching for effective ways to control them.
“There are ways to smother or to hand collect them. But there’s only been a handful of opportunities where we’ve been super successful in actually eradicating these mussels from a new water body,” he said. “So the prevention part is very important. Once they’re there, they’re very difficult to get rid of.”
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