Photo: Mark Wilson, Wikimedia

By Amy Lupica, ODP Contributing Writer

While humans face COVID-19, freshwater mussels could be facing a pandemic of their own. Researchers have found a novel densovirus, dubbed “Mussel-bola,” that may be responsible for killing 80,000 mussels in a 650 foot stretch of the Clinch River in Virginia over only 2 years. Mass mortalities of mussels are a grave threat to the ecosystems they live in; the “living rocks” filter and oxygenate water and are a food source for other wildlife. While experts are still investigating the novel densovirus, they hypothesize that the mass mortalities are also a result of ecological stressors like increasing water temperatures due to climate change.

Why This Matters: Mussels serve as a proverbial canary in the coalmine for freshwater ecosystems. A diverse abundance of mussels in a body of water indicates good water quality, and that the water is safe to both wildlife and humans. Mussels are already threatened by dams, pollution, and invasive species. The United States is home to 78 known species of freshwater mussels, more than half of which are endangered or threatened. 70% of North American mussel species are endangered, a very high percentage. Experts say losing freshwater mussels will have devastating ripple effects throughout freshwater ecosystems. Researchers worry that this novel densovirus, along with rising water temperatures and drought, could increase mass mortalities among these already threatened species.

Mussel Mass Mortalities

Figuring out just what has been causing these mass mortalities has been a years-long process for researchers. Jordan Richard, a biologist with the U.S. Fish and Wildlife Service and the University of Wisconsin, and his team found the novel densovirus among 17 different viruses in the mussel population. This one, however, was 11 times more likely to be found in sick mussels. While researchers have not conclusively shown that this virus is the cause of the mass mortalities, Traci DuBose, an ecologist at Virginia Tech, believes that the virus, climate change, and other threats, may be a perfect storm of deadly conditions, “It all goes hand in hand.”

While densoviruses are known to cause epidemics in species like “shrimp, cockroaches, crickets, moths, crayfish, and sea stars” researchers face a challenge researching their effects on mussels. There is no established model for observing the effects of disease on mussels in a laboratory setting. Tony Goldberg, a veterinary epidemiologist at the University of Wisconsin explains, “Mussels are the dark matter of wildlife disease. We know they exist, we know they’re important, but we don’t know what they’re made up of. We’re really starting from scratch.” Eric Leis, a Fish and Wildlife Service biologist agrees, “it’s almost like trying to find a unicorn.”

Despite facing challenges, researchers are excited to have the public’s attention. They credit the COVID-19 pandemic for sharply raising awareness of viruses. “People now are in tune with viruses as societal and natural disrupters. They’re taking them more seriously all around. It is good timing,” said Dr. Goldberg. His colleague, Mr. Richard, agrees, “It’s a great time to be talking about viruses and obscure animals.”