Helping Freshwater Mussels Clean Up the Delaware River

These mussels help to filter the water by removing sediment, algae and pollutants.

These mussels help to filter the Delaware River by removing sediment, algae and pollutants.

by Steve Donohue

During a recent survey on the Delaware River, I helped collect for scientific research, a freshwater mussel that was likely in the river below me when I was a kid in the 60s driving over a nearby bridge in the backseat of our family’s station wagon. While some species can live to 100 or more, the one I’m holding – and after examining, returned to the water – is probably 50-60 years old and has been silently filtering water all that time.

These freshwater bivalves, like their saltwater relatives, oysters, provide valuable “ecosystems services” by filtering water and removing sediment, algae, and pollutants, while also stabilizing the bottom substrate. According to the Partnership for the Delaware Estuary (PDE), a National Estuary Program  partner, one adult mussel can filter 20 or more gallons of water a day so this one mussel has probably treated several hundred thousand gallons of water over its lifetime.  Multiply that by hundreds or thousands of mussels in a healthy population and the numbers add up quickly.

Not long ago it was believed some species of freshwater mussels were extinct in the Delaware River due to pollution and spills from the River’s industrial past, over-harvesting for bait, loss of forests along streams, loss of fish hosts needed for reproduction, and dams that block fish passage.

In 2007, the PDE launched the Freshwater Mussel Recovery Program (FMRP) to help the comeback of the one dozen native species classified as reduced, threatened, or locally extinct.

EPA’s Scientific Dive Unit is collaborating with PDE, the Academy of Natural Sciences of Drexel University and the Philadelphia Water Department in restoration efforts.  One goal is to determine where freshwater mussels are located, and how many are present.  This will help quantify the current benefit they provide to water quality in the Delaware and the potential benefit a larger, healthy population would provide for future generations.


About the author: Steve Donohue has been an environmental scientist at EPA for over 25 years.  He is the Unit Dive Officer on the EPA Mid-Atlantic Scientific Dive Unit and works to address climate change issues and improve the efficiency and sustainability of public and private sector facilities.

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