Deep in the waters of the Delaware River, nestled among the rocks and mud, is a major player in improving water quality and increasing stream bottom stability and biodiversity within our local aquatic ecosystems: freshwater mussels. Yet, mussels are one of the most imperiled fauna globally — around 300 species of mussels are found in North America and the vast majority are threatened or endangered.
In order to assess and promote the health of our rivers and watersheds, Academy scientists and their partners set out to better understand their hidden lifecycles and then find a way to propagate and reintroduce these important mussels back into the wild. They formed the Aquatic Research and Restoration Center (ARRC), a regional collaboration of organizations who have a shared interest in conservation, restoration and enhancement of key aquatic natural resources.
As members of several families of bivalve mollusks, mussels can live in a range of freshwater and tidal habitats. Their shells are dark, and many are elongated and asymmetrical, compared with the clams we eat steamed or on the half shell. Unlike saltwater clams or oysters, most freshwater mussels are obligatory breeders — they need a fish host to complete their reproductive cycle. Initially, their eggs develop into a larval stage within their gills and, when released into the water column and taken in by fish, temporarily parasitizes the fish, by attaching themselves to the fish’s fins or gills, where they are constantly flushed with oxygen-rich water. Eventually, they develop, let go and drift in the currents until they find a place to call home on the stream or river bottom.
Mussels provide many “ecosystem services” or in other words, for something so small and hidden, they play key roles in affecting the overall health and biodiversity of our regional waterways. Mussels filter the waters of suspended particulates and excess nutrients that may be attached but need relatively unpolluted waters and healthy fish populations to thrive. Large mussel beds provide necessary habitat for other macroinvertebrates and fish to live within and reproduce, as well as help to decrease erosion during floods. Ultimately, because of their capabilities, the numbers and diversity of these unexpecting mollusks are a crucial indicator of the state of many of our streams and rivers.
Since 2012, Academy scientists and their partners participated in several surveys across local rivers in the urban corridor of the Philadelphia region to better understand mussel distribution and densities. The results were surprising — they found that there was a large enough population of diverse mussel species between Trenton and Philadelphia that they could consider transplantation and potential restoration initiatives within smaller streams in Southeastern Pennsylvania.
Several projects blossomed afterward: transplant studies using electronic detectors on the mussels; the creation of a demonstration hatchery at the Fairmount Water Works (FWW) led by Lance Butler of the Philadelphia Water Department and the Partnership for the Delaware Estuary; in vitro propagation at the Academy’s Patrick Center; and finally, the testing of several grow-out techniques at Green Lane Reservoir in northern Montgomery County.
The Green Lane mussel grow-out efforts have been expanded to include several new species propagated at the FWW, with aims to increase numbers and diversity of mussels being propagated, as well as expand scientific and educational outreach about the importance of mussels in our local waterways, and of course, to provide new stocks of freshwater mussels for future generations to find and explore.
“Freshwater mussels are a keystone aquatic species, not only capable of filtering around 10 gallons of water each day, but also act as the “Canary in the Coal Mine,” accumulating a range of pollutants in their tissues that researchers can use to evaluate water quality in any stream or river,” says Roger Thomas, scientist in the Academy’s Patrick Center for Environmental Research. Since the beginning, he and fellow scientist Danielle Kreeger have been an integral part of this work, attempting to understand their lifecycles and distribution within the Delaware River with the eventual goal of restoring mussels throughout the watershed.
This work has also provided a launching pad to many budding scientists. Malcolm Newman, Operations Manager for the Department of Biodiversity, Earth and Environmental Science at Drexel, got his scientific start working with Thomas.
“The main project I began working on was his freshwater mussel grow-out initiative at Green Lane Reservoir. I didn’t know anything about mussels when I started — nothing about their ecology, their evolution, or their conservation status,” Newman says. “But the more I participated in this project, growing our mussels and planning reintroduction efforts, I realized that it is exactly the kind of conservation work I wanted to do. Mussels are an incredibly important animal, and the broader impacts of conservation and restoration have made me indescribably proud to contribute to this project.”
Thanks to Thomas, Kreeger, Newman, their many local partners and other scientists at the Academy, many organizations realize the importance of these conservation efforts and have joined in to encourage more research on freshwater mussels and the critical role they play in our Delaware River Watershed.
And as with any long-term restoration program, the ultimate goal is to restore the numbers and diversity of this keystone organism for future generations.
Thanks again to our partners in the ARRC: Partnership for the Delaware Estuary, Philadelphia Water Department, Dept. of Parks and Rec., City of Philadelphia, John Bartram’s Association, Independence Seaport Museum and Audubon Mid-Atlantic.
You can support the Academy’s research efforts to understand the natural world and inspire everyone to care for it by becoming a member or donating to our scientific collections.
Tú también puedes apoyar los proyectos de investigación de la Academia, y así ayudar a entender y proteger la riqueza natural convirtiéndote en miembro o haciendo una donación a nuestras colecciones científicas.