by Erin Hathaway
Human civilization depends on Earth’s natural ecosystems. In addition to tangible things such as raw materials including lumber and natural gas, ecosystems provide services and functions such as protection, filtration, retention, pollination, and regeneration. Ecosystem services are so fundamental to life that they are easy to take for granted and so large in scale that it’s hard for us to imagine that human activities could destroy them.
Once valued only as a source for food and fisheries, oysters are now often labeled as “ecosystem engineers” because we now recognize their ability to filter water, provide structured habitat for other species, and protect shorelines from erosion by stabilizing sediments and providing wave attenuation. As oysters grow, they form beds, which provide a substrate for fish and other marine organisms to live and feed on. Their reefs provide our shorelines with buffering capacity acting like natural speed bumps. And, they have an amazing ability to filter water – an adult oyster can filter up to an estimated 50 gallons per day.
Oyster restoration is gaining momentum as public awareness about the importance of their roles in our waterways, specifically coastal waterways, has increased. In the New York-New Jersey Harbor Estuary system there are a number of new efforts to restore oyster and mussels habitats such as oyster gardening and pilot oyster reefs. This can be contributed to more awareness of our coastal vulnerability in general with unprecedented storms like Katrina and Sandy.
Since moving away from the East Coast to a land locked state, my perspective shifted from coastal lover to freshwater enthusiast with a new interest in freshwater mussels. Can we put as much energy and enthusiasm towards freshwater mussel restoration as we do oysters? Like their cousin, the oyster, freshwater mussels are bivalves and filter feeders. They filter bacteria, algae, and other small particles, improving water quality. Additionally, they serve as food for fish, reptiles, birds, and mammal populations. Freshwater mussels are found in rivers and streams worldwide, but North America is a diverse hotspot for these creatures and home to 304 species of the 1,000 species worldwide. The majority of these species are found in the southeastern watersheds of the Ohio, Tennessee, Cumberland, and Mobile Rivers.
However, unlike oysters, the reproductive phase of freshwater mussels presents a new challenge to their population growth and restoration. Not only do mussels require a fish host to reproduce, but the host fish also has to be a particular species – bass, darters, and minnows. Dams and exotic fish species threaten this reproduction system, as dams prevent genetic diversification and exotic fish species threaten native host fish.
To combat the declining mussel populations, the Virginia Department of Game and Inland Fisheries initiated a program to restore mussels. The Aquatic Wildlife Conservation Center (AWCC) was created to propagate mussels in housed tanks, which mimic streambeds and contain a variety of host fish. These propagated mussels can be released back into natural waterways in hopes of restoring a self-sustaining population.
Similarly to oysters, freshwater mussels should be a part of the restoration conversation. Their incredible filtering capabilities in addition to their structural beds help stabilize benthic sediment, improve water quality, and provide habitat for aquatic life. They will become food for predators, supporting a larger food web. Many of our freshwater streams and rivers are the sources of our drinking water. The Ohio River is a source of drinking water for more than three million people. These rivers and streams also serve as food and recreational resources, drawing tourism revenue and creating a sense of place. Mussel restoration is not going to transform the systems like the Ohio River into a pristine habitat overnight but they serve as a small part to the larger ecosystem.
Virgina Department of Game and Inland Fisheries – Freshwater Mussels
Bunje, Paul. The Bivalvia. University of California Museum of Palentology