Our Friends, the Freshwater Mussels

Freshwater mussels found the Brandywine River

Freshwater mussels found in the Brandywine River

by Andrea Bennett

No, we can’t eat them, but they are kind of cute – as far as mussels go. And these little bivalves do something that we could only do if we spent millions of dollars constructing a filtration plant: they filter out pollution from our drinking water sources. In fact, one adult mussel can filter up to 15 gallons of water per day; a 6-mile stretch of mussel beds can filter out over 25 tons of particulates per year!

Mussels are sometimes referred to as “biosentinels” – a living indicator of the presence of chemical contaminants or microbial pathogens. Because the presence of freshwater mussels means that a watershed is healthy, they provide a low-cost way to monitor water quality.

I was lucky enough to go on a mussel monitoring outreach event in the Brandywine River with The Partnership for the Delaware Estuary. We visited a land-locked pond near the Brandywine, where we found adult eastern floater mussels, which can live to over 70 years old! We also found younger mussels – about 8 years old – but no “babies.” We then went to the Brandywine River, where we found eastern elliptio, but unfortunately, no young mussels. At both places, we found corroded and disintegrating shells.

Back in the early 1900s, there were about 14 species of native freshwater mussels in the Delaware River Basin. Now, it’s difficult to find anything but eastern elliptio in the Delaware watershed. Most importantly, you can’t find juveniles. Mussels reproduce by releasing larvae, called glochidia, which attach to the gills or fins of fish (the fish don’t know they are there). In about 3 weeks, the glochidia fall off the fish to grow into juvenile mussels. Research shows that mussels are still releasing the glochidia, but the juveniles are not surviving.

Scientists from the Partnership for the Delaware Estuary, with support from EPA and other agencies, are looking into what’s making it difficult for freshwater mussels to reproduce and survive. In 2013, EPA published new recommendations for how much ammonia can be in surface water. These recommendations will help states work with dischargers and sources of non-point source pollution to better protect aquatic life, especially freshwater mussels.

You can get involved too! The Partnership for the Delaware Estuary has freshwater mussel volunteer monitoring activities. If you’re in southwestern Virginia, you might be interested in projects in the Clinch River, which has more freshwater mussel species than any other river in North America.

Protecting these small, barely noticeable aquatic animals – so they can live, reproduce, and filter the water – also protects us, by improving the quality of our waterways.


About the author: Andrea Bennett is a biologist with EPA. Andrea enjoys birding, kayaking and playing the mandolin and she is a member of her local watershed protection team.


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