If someone had asked me to tell them about freshwater mussels before I started my AmeriCorps position with the U.S. Fish and Wildlife Service, I would have been at a loss. Despite studying biology and ecology, I never gave much thought to freshwater mussels. Sadly, I think this is true for most people. Freshwater mussels are an underappreciated group of organisms that most people know little, if anything, about. Our lack of knowledge is understandable, however; freshwater mussels are not cute, cuddly, or charismatic like dolphins, eagles, pandas, or tigers. Instead they are cryptic organisms that live in the sediment at the bottom of lakes, rivers, and streams and often resemble rocks.
Despite the lack of attention paid to them, freshwater mussels play a vital role in our freshwater ecosystems. Mussels are one of the few animals that improve water quality. As filter feeders, freshwater mussels remove things such as plankton, fungi, algae, and bacteria from the water column. Additionally, waste excreted back into the water by freshwater mussels is in a form that provides readily available nutrients for plants and algae, and waste deposited into the sediment by freshwater mussels provides food for some bottom dwelling invertebrates and fish. The mussels themselves are an important food source for muskrats, river otters, and some fish, and the mussel shells provide habitat for algae and some insects. Furthermore, freshwater mussels are an important indicator of water quality. Since mussels are relatively sedentary organisms, they cannot escape changes to their ecosystem. The loss of mussels from an ecosystem provides us with a critical warning sign of pollution or other environmental problems.
Unfortunately, we are seeing this warning sign increasingly often. Today, more than 70 percent of North America’s approximately 300 freshwater mussel species are in decline. In West Virginia alone, there are eight species of freshwater mussels that are listed as endangered under the Endangered Species Act. Like many other species, the decline in freshwater mussels is largely driven by human activities. Some of the main threats include the use of pollutants that make their way into our freshwater ecosystems, sedimentation of our waterways resulting from by activities such as construction and deforestation, the construction of dams and other impoundments that alter the natural flow of streams and rivers, the introduction of exotic species such as zebra mussels, the decline of some fish species that freshwater mussels use as a hosts for their larval stage, and the direct poaching or harvesting of freshwater mussels.