Oregon State University scientists say it's unclear what kind of damage could be done by the many species that rode floating debris across the Pacific Ocean from Japan.
"Ecologists have a terrible track record of predicting what introduced species will survive and where," Oregon State marine invasive species expert John Chapman told The Oregonian. "But once things are here, they are a threat.
Scientists hadn't expected so many organisms would survive the ride, let alone that they would thrive, he said.
Experience with other invasive species has shown they may be around for years, even decades, causing no problems until they suddenly spread and threaten native species, he said.
"They could explode at any time. It's just like roulette. Each time something lands here, we pull the trigger. We're getting more and more every year," Chapman said.