Environmental scientists and teenage campers recently found an encouraging sign for the health of the Delaware River during a survey near the Pennypack Creek in Northeast Philly. At low tide, they spotted and collected about 120 freshwater mussels, which have become much less common in the region's rivers and streams.
Freshwater mussels are bivalve mollusks, like oysters and clams, that hang out along riverbeds to sift and feed on bacteria, algae and pollutants in the water. They're an important indicator of water quality and support the wider food web by sustaining habitats for fish and other aquatic species.
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The survey was conducted as part of a wider initiative to monitor and restore freshwater mussel populations in the Delaware River watershed. More than a dozen species are native to the Delaware Estuary, but they've become rarer due to polluted water, toxic spills and the loss of forests along rivers and streams, along with other factors that affect their numbers.
“These filter feeders are great for the ecosystem so finding them near Pennypack Creek in the Delaware River was a treat," said Bria Wimberly, a public program coordinator for the Discovery Center in East Fairmount Park.
The survey in Northeast Philly covered only a small area and yielded freshwater mussels from at least three different species, organizers said.
The Aquatic Research and Restoration Center, Audubon Mid-Atlantic and Riverfront North Partnership also participated in the survey, which was joined by campers from the Pennypack Environmental Center.
All of these groups are part of a wider coalition working to boost the status of freshwater mussels in the region, where efforts are underway to breed them by the thousands. The Partnership for the Delaware Estuary is in the process of scaling up its existing hatchery in a new facility at Bartram's Garden in Southwest Philly. The organization plans to produce up to 500,000 freshwater mussels each year. They will be seeded in local streams, ponds and stormwater basins to help with water filtration.
Adult mussels can each filter up to 10 gallons of water per day. They can live for up to 100 years, generally remaining sedentary where they bury themselves into stream beds. To reproduce, the females release larvae that attach to various fish before releasing from them when they reach maturity. Polluted water, overfishing and dam construction all upset the natural cycle of mussel production, but stricter regulations from the Clean Water Act of 1972 have gradually helped create a more hospitable environment for restoring mussel beds.
More than a decade ago, mussel researchers found multiple species — including some thought to be extinct — in parts of the Delaware River where they had gone mostly undetected for years. They've been studied in years past in the Brandywine and Ridley creeks as well, but not in significant numbers.
Much of the United States and Canada, home to nearly 300 native species of freshwater mussels, have seen declines in freshwater mollusk populations as many become endangered or threatened, according to the Forest Service of the U.S. Department of Agriculture.
The hatchery at Bartram's Garden will rely, in part, on hybrid striped bass to spread mussels into local waterways. The bass species can be easily reproduced to generate larger numbers of mussels. There also will be an educational component that gives young people opportunities to get involved in the restoration. The Partnership for the Delaware Estuary has described the project as the first of its kind in the world, and it has received public and private funding from a range of sources.
Nathan McWilliams, stewardship manager for Riverfront North Partnership, said the discovery near Pennypack Creek is another important step in pinpointing viable locations for mussels.
"We don’t often think of the Delaware River in Philadelphia as a healthy, natural resource, and now we have tangible evidence that it is tracking in the right direction," he said.