The Wyoming Game and Fish Department has found invasive zebra mussels in marimo balls in several pet stores across the state.
Marimo balls are balls of filamentous algae that are often used for aquarium decoration and to aerate the water. They can be wild-harvested or raised in a closed aquarium or tank system. Officials suspect that the mussels are in the marimo balls that are wild-harvested from Ukraine or southern Russia, where zebra mussels are native.
"If they have viable zebra mussels in there, you might not be able to see them if it's a veliger, which is the initial life stage of the zebra mussels, they're very microscopic, small," said Alan Osterland, the WGFD chief of the fisheries department. "And then of course, they develop into a mussel, and they have the shell and everything and generally about the size of your pinky fingernail."
They haven't been detected in Wyoming yet, but zebra mussels can outcompete native mussels for food, lower the amount of oxygen in the water available to fish, and cause expensive damage when the sheer number of them clog pipes.
"Zebra mussels are extremely tough in all life stages. They can survive extreme heat and cold, and chemicals," said Osterland.
Typically, zebra mussels spread to new water systems on boats that have been trailered between bodies of water, but 30 states have reported finding zebra mussels in marimo balls so far.
"On Wednesday, we received notification that they had found a suspected zebra mussel in a marimo ball. That was at a pet store in Washington state. So that prompted us to look around and our pet store statewide to see what we could find," said Osterland. "Because, obviously, we spent about $1.3 million a year to prevent invasive species coming into the state and one of the big ones is zebra mussels that we've identified as being potentially high impact to our aquatic ecosystems and water delivery systems in the state."
WGFD recommends that if you've purchased a marimo ball in the last couple of months that you properly dispose of it and any other plants in the tank immediately. Do not dispose of it or any aquarium water down a drain or in a watershed. Detailed instructions can be found on the WGFD website.
If you're looking to purchase marimo balls in the future, Osterland recommends purchasing them from a vendor that grows them in a closed water aquarium system to lower the risk of zebra mussel stowaways.
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