Freshwater Mussels: The Silent Keepers of America’s Rivers

February 28, 2005—The Nature Conservancy is striving to protect South Carolina’s freshwater ecosystems by working with numerous partners to restore and maintain clean river systems throughout the state. One way to do this is by promoting healthy mussel populations in our waterways.

Similar to the canary in the coal mine, freshwater mussels are an indicator species. Their health is a barometer for the overall wellbeing of a river system. As filter feeders, mussels absorb disturbances such as alterations to river flow, chemical pollution and increased sedimentation.

Eric Krueger, aquatic ecologist with The Nature Conservancy in South Carolina, is leading a study of freshwater mussels in the Pee Dee River system. In a joint effort with scientists from the South Carolina Department of Natural Resources, Progress Energy, South Carolina Aquarium and the U.S. Fish and Wildlife Service, Krueger and his colleagues are digging by hand in shallow water and scuba diving in deep water for species such as the Carolina heelsplitter, the yellow lamp mussel and the tidewater mucket. Their efforts will help determine what mussel species exist in the river system and what reaches of the river support these species.

“Once we find the locations of mussel populations, we hope to work with private landowners, public agencies, and other stakeholders to protect this important steward of clean water in South Carolina,” Krueger said.

To date, scientists have identified 304 mussel species in the United States, of which 72 percent are listed as either rare, endangered or of special concern. With 90 percent of the country’s known mussel populations found in the Southeast, the mussels in South Carolina’s waterways are still very much a mystery. Currently, scientists are aware of approximately 40 species of freshwater mussels in South Carolina, with several new species known to be present, but not yet formally described or named.

“Only several species in South Carolina can be considered common at this time,” Krueger said. “There are excellent populations in some South Carolina rivers and streams, but others have had their mussel fauna completely eliminated by agricultural and urban sedimentation, chemical pollution, and other factors.”

To demonstrate the essential service mussels provide to rivers and streams, the photos below show the species’ filtering process. The tanks in the photos contain water from a South Carolina river that is turbid with suspended soil. After as little as 15 minutes, the majority of the material is cleaned from the water column. The mussels literally filter the water column as a means of obtaining food. In the process, they take in a lot of non-food items, leaving clean water behind.

“In healthy rivers, freshwater mussels are the dominant living thing by weight, so try to imagine the filtering process you see in these photos multiplied many thousands of times over in a healthy mussel population,” Krueger said.

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