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Bay Blog: zebra mussels


Photo of the Week: Invasive mussels pose growing threat

Dr. Bill Harman, Director of the State University of New York (SUNY) at Oneonta Biological Field Station in Cooperstown, New York, holds a flip-flop recovered from Otsego Lake and covered with invasive zebra mussels.

Zebra mussels (Dreissena polymorpha) are freshwater bivalves found in lakes, rivers, streams and reservoirs. Native to Europe, zebra mussels were found in the Great Lakes region in 1988 and later discovered in the upper Susquehanna River in 2002. Since then, the invasive mussel has spread further into the Chesapeake region’s rivers and streams. In 2011, the mussel was spotted for the first time in the Eastern Shore’s Sassafras River. And in 2015, two watermen found zebra mussels colonizing on their fishing gear in the Susquehanna Flats.

Efficient filter-feeders, zebra mussels can remove a lot of plankton—an important food source for other critters—from the water. They also attach themselves to native mussels and to manmade structures, clogging intake pipes and encrusting boat hulls and buoys. Scraping, power-washing and chemical treatments can be used to control zebra mussels, but once a population has been established, it can be almost impossible to eradicate.

To prevent the spread of zebra mussels and other invasive species, make sure boat hulls, trailers and other equipment are thoroughly cleaned before moving them to a new body of water.

Image by Will Parson

Stephanie Smith's avatar
About Stephanie Smith - Stephanie is the Web Content Manager at the Chesapeake Bay Program. A native of the Midwest, she received her Bachelor’s in Professional Writing from Purdue University and Master of Science degree from the University of Michigan. Stephanie’s lifelong love of nature motivates her to explore solutions to environmental problems and teach others what they can do to help.


Invasive zebra mussel found for first time in Maryland’s Sassafras River

The invasive zebra mussel has been found for the first time in the Sassafras River, a tributary of the upper Chesapeake Bay on Maryland’s Eastern Shore.

Zebra mussel (image courtesy John Tolva/Flickr)

A citizen found a single adult zebra mussel attached to a dock and reported it to the Maryland Department of Natural Resources (DNR). The mussel was discovered in the lower Sassafras River near Turner Creek.

Although the discovery does not necessarily mean that zebra mussels have established themselves in the Sassafras River, it is very unlikely that this single mussel is the only one in the river, according to DNR biologist Ron Klauda.

Biologists believe that unusually low salinity levels in the upper Bay this summer may have allowed zebra mussels to expand beyond the Susquehanna River, which is the only other river in Maryland where the species has been discovered. This means that zebra mussels could have spread to other rivers in the region, such as the Bohemia, Elk or Northeast rivers.

Tiny zebra mussels have caused significant ecological and economic damage in North America. They are extremely efficient filter feeders that significantly reduce the amount of plankton available to native aquatic life. Massive clumps of zebra mussels can also encrust boat hulls, damage power plant intakes and disrupt municipal water systems. Since they were introduced in the Great Lakes in the 1980s, zebra mussels have caused more than $5 billion in damages and losses in North America.

Zebra mussels spread mainly by attaching themselves to boats, boat trailers and other watercraft. Recreational boaters can unknowingly carry zebra mussels and larvae in bilges, bait buckets, coolers or on aquatic vegetation clinging to boat props and trailers.

If you think you’ve found a zebra mussel in a Maryland waterway, you should report the discovery to DNR by calling (410) 260-8615. For more information about the discovery, visit DNR’s website.

Image courtesy John Tolva/Flickr


Question of the Week: What do invasive species do to the Bay?

Welcome to this week’s installment of the BayBlog Question of the Week! Each week we'll take a question submitted through the Chesapeake Bay Program website and answer it here for all to read.

This week’s question came from Elizabeth: “What kind of effect does the zebra mussel have on fish like the striped bass?”

This is a great question, and one that can be applied more broadly by addressing how invasive species affect native species in the Chesapeake Bay.

The important thing to remember is that every species that is native to an ecosystem plays an integral role in the food web for that particular ecosystem. So in the Chesapeake Bay, everything from plankton to blue crabs and striped bass are important to the health of the Bay.

When an invasive species is introduced into an ecosystem, it puts additional stressors on the native species that live there. In the Chesapeake, not only do native species have to deal with pollution, they also have to worry about invasive species depleting their food sources.

For example, the zebra mussel is an invasive species in the Chesapeake Bay. It is also a filter feeder. While this could be seen as a good thing – improving the clarity of the water – it is really an issue to contend with when the zebra mussel consumes the plankton that is vital to the survival of many primary consumers in our ecosystem, like Atlantic menhaden and other small fish. These smaller fish are then prey for larger fish such as striped bass.

If there is not enough plankton to feed the menhaden, in turn there will not be enough menhaden to feed the striped bass, and so on. In the food web, every species fluctuation results in a domino effect in the rest of the ecosystem.

Invasive species can take a toll on an ecosystem. Not only do zebra mussels significantly reduce the plankton available to native filter feeders, they also hinder boat navigation and cause damage to the power industry by clogging vital pipes.

While eradication of invasive species is typically very difficult and extremely expensive, there are things you can do to help the problem. Boaters are encouraged to check their hulls, trailers and recreational equipment for zebra mussels before moving them to a new water body. You can also do your part to reduce pollution to the Bay, which will help the Bay watershed's native plants and animals.

Do you have a question about the Chesapeake Bay? Ask us and your question might be chosen at the next Question of the Week!


Invasive Zebra Mussels Found in Susquehanna River

Zebra mussels have been found for the first time in the Maryland portion of the Susquehanna River, according to the Maryland Department of Natural Resources (DNR).

Zebra mussels are small, invasive freshwater mussels native to the Caspian Sea. As zebra mussels grow, they encrust boat bottoms and clog municipal drinking water systems and power plant intakes. A study by New York Sea Grant showed that zebra mussels cost the power industry $3.1 billion from 1993-1999.

In addition to economic losses, zebra mussels cause ecological damage by killing native mussels and filtering too much plankton from the water. The presence of zebra mussels has also been linked to declining duck populations.

While zebra mussels spread rapidly with natural river currents, they are most often transferred between water bodies by humans. According to DNR, recreational boaters can unknowingly carry zebra mussel larvae in their bilge, minnow buckets or on trailers.

Boaters can help stop zebra mussels from spreading to other rivers and lakes by:

  • Washing down boat hulls.
  • Cleaning bilges.
  • Removing aquatic vegetation from props and trailers.
  • Limiting transfer of boats from one water body to another, particularly from the Susquehanna River to other areas.

Read more from DNR about zebra mussels in the lower Susquehanna River.

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