Who knew that zebras multiply in the rain?
An extremely rainy late summer and fall may be playing a role in the spread of zebra mussels, an invasive species, among rivers that feed into the Chesapeake Bay from the north. The fast-reproducing Eurasian mollusks have apparently jumped from the Susquehanna River to the Sassafras River on Maryland’s Eastern Shore, and may be headed for other Chesapeake Bay waterways, the Maryland Department of Natural Resources warns.
After hitch-hiking on ships from the Black Sea to the Great Lakes in the 1980s, zebra mussels caused over $5 billion in economic damage in the Midwest by clogging up power plant intake pipes and water treatment facilities.
The mussels were first discovered in Maryland’s portion of the Susquehanna River in 2008. At first, some experts doubted the creature’s ability to spread around the Chesapeake Bay, because it lives in fresh water, and the estuary is a mixture of salty and fresh water.
But recently a zebra mussel was found in a second Maryland river, the Sassafras, according to the Maryland Department of Natural Resources (DNR). The state’s natural resources agency speculates that the large amount of rain recently created such fresh conditions in the upper Chesapeake region that the mussel was able to move from river to river, perhaps in or on a boat.
“There may be other zebra mussels that have taken advantage of the freshwater conditions in the upper Chesapeake this year to colonize new habitat, especially in the Bohemia, Northeast, and Elk Rivers,” said DNR biologist Dr. Ron Klauda.
The fingernail-sized, striped mollusks at first appear harmless, because they eat some types of algae and can make the water clearer, at first. But they can also reproduce so fast they destabilize the balance of life in rivers and lakes, depriving some fish of food and causing excessive growth of other varieties of algae.
How to combat the spread? If you’re moving your boat from one river system to another, first wash it thoroughly and flush all of the water out of all bilges and wells, DNR advises.
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By Tom Pelton
Chesapeake Bay Foundation