Between 2016 and 2019, an estimated several hundred thousand to a million mussels normally found in the freshwaters of the Clinch River that winds through the Appalachia mountains have disappeared.
This die-off follows a global trend that is concerning scientists.
Mussels are part of a delicate ecosystem that benefits from a healthy mussel population. Each mussel filters up to 10-gallons of river water each day, removing algae, silt, and heavy metals. Fish, amphibians, plants, bugs, and people all rely on mussels to keep rivers clean.
Currently, the Clinch River is just one of five U.S. rivers where these die-offs are occurring. A river in Spain has also reported a decline in the mussel population.
Scientists suggest that the source of the problem is habitat loss, pollution, and climate change. Infectious disease may be another source of the decline.
This may not be just a mussel problem, either. Declining fish populations may be making an existing problem worse.
To reproduce, mussels lure nearby fish who attempt to eat what looks like a worm. One a fish attaches itself, the mussel injects the fish with larvae. When these larvae grow large enough to survive on their own, they return to the water.
Some mussel species rely on just one type of fish species to survive. When dams and habitat loss affect the one species of fish, the mussels can’t reproduce and will die off.
The Clinch River has seen ten species already go extinct. Another 20 species are now on the endangered species list. Globally, 300 species are at risk of disappearing.
The search for a common link in die-offs is now a global effort. Many scientists agree that human activity is a primary driver, infectious disease is also likely another problem.
So far, researchers have found the major challenge in identifying any one cause is that each mussel species may have unique traits that are exclusive to that species; these traits may be wholly different than a species further down the river. So solving the problem in one species won’t necessarily provide insight into what affects another species.
Some researchers are also learning how to breed mussels in captivity. While some species of mussels are rare and finding both a male and female can be difficult, the challenge may be worthwhile. Reintroducing just 500 mussels into a river ecosystem can be beneficial.
Figuring out how to save mussel species isn’t just about the conservation of a particular animal. Mussels share a relationship with many aquatic animals. What affects one species affects all species. The biological diversity of our waters may depend on solving this issue quickly and before they disappear forever.