The settlement agreement letter allotted $50,000 of the NRDA funds to mussel restoration projects. Honors Thesis research by Esra Demirhan ’18 and Eurnett Christopher ’25 builds upon our pre-dam removal monitoring efforts by evaluating the potential impacts of dam removal on freshwater mussels currently in the system and introducing native freshwater mussels to portions of the stream that have been restored.
Esra Demirhan ’18 uses a bucket with a glass bottom to search for bivalves along a transect in Bushkill Creek.
Freshwater mussels are often considered keystone species in freshwater ecosystems because of their ability to affect the organization of the community to a far greater degree than would be predicted considering their abundance. For example, mussels function as habitat generators by creating habitats for other organisms, stabilizing streambeds, and providing nutrients that stimulate primary production. Freshwater mussels also improve water quality through removal of suspended particles by filter-feeding. Yet, freshwater mussels are sensitive to environmental change, and they are recognized as one of the most imperiled groups of organisms. In North America, 10% of species went extinct in the last century, and only half of the remaining species are projected to survive the next century. Although the dramatic decline in mussels has involved a variety of threats, the single most important threat is habitat loss as a result of dam construction, channelization, siltation, and contaminants. Freshwater mussels also have a unique fish-dependent life cycle, which means that their distribution is restricted when fish movement is restricted by dams.
Emily Ramirez ’18 and Emily Lynch ’18 snorkeling in Bushkill Creek to scan sediments for freshwater mussels.
Pre-removal assessment included field surveys to quantify freshwater mussel abundance and distribution in Bushkill Creek and toxicity assays to assess the possible effects of heavy metals in released legacy sediments on survival and growth of mussels. Now that dam removal has commenced, we will be working with the Delaware River Basin Commission to restore actual mussel beds in the newly free-flowing portions of the creek.
LAB FAM members who have contributed to this project: Esra Demirhan ’18, Donna Hanna ’22, Eurnett Christopher ’25, and Jamie Bryan ’25.
After significant summer storms made the creek extra turbid, this day was a much better day for fun photos than for mussel surveys!
So far, our results indicate that:
- freshwater mussels are absent in Bushkill Creek directly upstream and downstream of the dams but are present in Jacobsburg State Park ~5 km upstream of all dams and downstream of dam 1 in Delaware River at a catch per unit effort (CPUE) of 148.2.
- adverse effects to freshwater mussels downstream of dam 1 due to burial by fine-grained sediments or exposure to metals would be insignificant.
- reestablishment of the natural flow regime, improvements to water quality, and elimination of impediments to host fish migration will improve the likelihood of restoring freshwater mussel communities in lower Bushkill Creek.
Austin Best ’22 and Donna Hanna ’22 get ready to survey for mussels in Delaware River just downstream of the first dam in Easton.