Throughout his professional life, U.S. Forest Service researcher Wendell Hague has been studying freshwater mussels in biodiversity hotspots. His 30+ year career is hidden in a single question. Why do bivalves in this area disappear?
Freshwater mussels are one of the most endangered groups of animals in the world. There are currently over 300 native species in North America. Many have colorful colloquial names such as fuzzy pigtoes, purple grassy bags, grooved elephant ears, orange-footed pongre bags, pink heel splitters, and monkey faces. Some southeastern basins have seen a third to half loss of mussels over the past half century. Another 21 southeastern species are thought to be extinct, with dozens remaining only in fragments of the previous range.
Threats to mussels come from many quarters, including contaminated spills, waterway dumming, temperature temperatures, pathogenic viruses and invasive competitors, but explanations of the extent of America’s most widespread death, which began decades ago in the southeast, remained out of reach.
Recent discoveries have helped biologists develop techniques to grow mussel species, the most threatened in the lab.
“We’re working at USDA’s Southern Institute in Frankfort, Kentucky,” said Haag, who works for USDA’s Southern Institute. “These are devastating events and we don’t know what is causing them.”
Die Off receives little attention outside of science circles. This is a fact that does not surprise Art Bogan, a mollusk research curator at the North Carolina Museum of Natural History. “They aren’t charismatic like pandas, gorillas, or even fish,” he said. “Some people call them pet rocks.
For a long time, little has been known about freshwater mussels and their unique life cycle. Include the fact that mussels must parasitize certain species of fish to complete the reproductive cycle. This recent discovery has helped biologists develop techniques to grow the most threatened mussel species in the lab, and to prevent them from blinking.
“All we can do is capture these animals, put them in the stream and hope for the best,” Haag said. “It’s kind of gambling because we don’t know what causes these drops to begin with. We don’t know if they’re still playing or whatever those factors are. [have] Please come and go. ”
Researcher Wendell Haag is walking to Duncard Creek, Pennsylvania, for his research into freshwater mussels.
Michael Swenssen
When the female mussels ingest sperm, and then the males drain them into the water, the larva they produce are called Grotidia and hatch the gills, but require further development outside the mother. Female mussels in the eastern US have evolved with lure-like appendages. When you investigate what fish look like minnows, mussels drain baby clouds moving from the fish’s mouth into the gills. (Other mussels will be released) Grochdia chunks It looks like a fish like a net of food that fish swims with or larvae. ) Young mussels develop gills for 2-5 weeks until they fall into river beds and mature enough to begin their own life.
Native mussels probably don’t move much after the establishment of 50-75 yards. Some species can live for more than 100 years, but more commonly, they live for 10-50 years. Native mussels vary widely – from pinky’s nail size to the other side of their feet – and provide a variety of ecosystem services. It is also sometimes called the liver or kidney of a river. “They remove all sorts of things from the water,” said Christopher Ease, a biologist at North Carolina State University. “Silt, algae, bacteria, fungi, fine organic matter. Each mussel can filter from 5 to 20 gallons a day. Multiply it by thousands of mussels and many river miles, they’re doing great service for us.”
Experts are worried that the newly arrived golden mussels could spread to North American waterways like other non-natives.
Not only does mussels have clean water, but they also stabilize river habitats, transfer particulate matter to the riverbed, and create biodiversity hotspots by increasing the abundance and diversity of surrounding insects. Mussels also provide food to birds, fish and other wildlife. Experts say their presence is a good indicator of river health.
Over the past 30 years, US scientists have spent much of their time and effort studying native mussels, including building laboratories and hatch sites that grow and reintroduce dangerous species. Still, it could be a lost battle. Last year, Texas listed six species as at risk, and a comprehensive survey published in 2022 found only 17 of the 36 species of mussels once found in South Dakota. The U.S. Fish and Wildlife Service proposes designating key habitats across 17 states to protect four endangered mussel species.
The situation is not global. Seven of the 16 European mussels are listed as threatened. (There was a bit of good news when researchers discovered that the DNA of three mussel species was thought to be near extinction during the 2024 Olympics in Paris.) The number of Asian species is comparable to the US, but not so many are known. Pressure on mussels in South America is similar to that in North America. In Argentina, scientists discovered 35 species in 1990, of which 17 have not been seen since.
The mussels in Plain Pocket Book showcase fish-like lure-like appendages on the Potomac River in West Virginia.
Ryan Hagerty / USFWS
The list of known threats to mussels is long. “I’m basically human,” Bogan said. In the United States, the number of mussels began to decline with the advent of colonial agriculture. Colonial agriculture abandoned sediments in rivers and buried many mussel species. The mussel population took a different kind of hit in the mid-1800s. The clothing manufacturer began making mother buttons using the inside of mussel shells known as naakars. Freshwater mussels also produced pearls, discovering gem discoveries in the east, south and midwest. The pearl, discovered in New Jersey in 1857, reportedly won $1,500 at the time.
In the 1980s, invasive mussel species such as Quagga and Zebramuls, native to Eastern Europe, began to threaten mussels in the US. These species are far more aggressive feeders, said Caryn Vaughn, a researcher at the University of Oklahoma. They have a much higher reproductive rate, can be attached to the shells of native mussels, and can kill them completely. In Europe, invasive mussels have been found to create unfavourable conditions for the Indigenous people and expel them from their habitat.
Late last year, biologists discovered that golden mussels, a new invader from Asia, had arrived at Stockton Port, California, and had been introduced by ballast water from ships travelling from international ports. Experts are worried that they could spread to North American waterways like other non-natives. Through the hull of a recreational boat, bait buckets, bilge water, and waterfowl movements. “If native mussel populations invade areas where habitat degradation, contamination and other stressors have already been highlighted, Vaughn said.
By slowing the flow of the river, the dam causes suspended sediments to fall to the bottom of the river, filling the beds of mussels.
And in many places, climate change is at the expense of temperatures rising. The severely extended drought on the Southern Plains has caused the deaths of many mussels, Vaughn said, “Not only due to dehydration, but also lowering water levels in the summer, the water temperatures increase, and mussels basically get hotter and die from stress.”
Experts say the extensive construction of dams in the 20th century was likely the most severe blow to freshwater mussels. By slowing the river flow, the dam caused suspended sediments to fall to the river bottom, filling the beds of mussels. Also, as a barrier to fish migration, dams can effectively block the breeding and migration of mussels. (In streams nationwide, dam removal helped restore mussel populations.)
As a filter feeder, mussels are susceptible to waterborne contaminants such as pesticides, heavy metals, pharmaceuticals and other chemicals. Road salt is associated with some depletion. On the Allegheny River, mussels were found with increased radium levels and were allowed to drain water from oil and gas operations.
An endangered species of freshwater mussel found on the Allegheny River in Pennsylvania.
Ryan Hagerty / USFWS
Fragmentation of river systems is also a serious and growing threat. “where [mussels] Eads said: “Weevils will ring out because weeping cannot reduce deposition and material diversity, and therefore evolutionary fitness, Musselmann, whether Musselmann can’t lay Musselmann, Musselmann can’t lay Musselmann, Musselmann can’t lay Musselmann, Musselmann can’t lay Musselmann, Musselmann can’t lay Musselmann, Musselmann can’t lay Musselmann, Mussel become Mussel’s beds. It’s pretty bad for some species.”
Despite everything known about the myriad threats to freshwater mussels, the cause of the devastating Southeastern deaths that begin in the 1970s and continue in small to medium-sized streams to this day remain a mystery. Haag published paper This decline in 2019 still studies death, studying whether it is studying recovery in unaffected areas in the southeast, or even conserving mussel beds. “These streams are still pretty much escaped,” he said. This causes ecological ripples across freshwater ecosystems, from dirtier waters to reduced biodiversity. “They are keystone animals on which many other ecological functions depend.”
Researchers hope that freshwater mussels may not be charismatic, but they are considered to be deserved of protection.
Haag hypothesizes that the decline of mussels in the southeast is related to past colonization by invasive Asian Asian ajams. Asian clam populations are falling apart in the southeast, but their legacy continues to live on: [native] The mussels were unable to recover,” The Hague said. “Or it’s going to take a long time.”
Many mussel species populations have declined so low that wildlife agencies are currently cultivating them at hatch sites to be released in local streams. Some Native American tribes run hatch sites for environmental and cultural reasons. Mussels are “first food” or traditionally important food for members of the Umatira tribe, said Alexa Maine leads biologists from allied tribes. Umatira A research and restoration project on freshwater mussels from an Indian reservation in southeastern Washington. They are also ornaments, Regalia gems and tools, she said. “Every tribe in the Columbia Basin has an extensive history with mussels.”
Throughout the United States, mussel researchers hope that freshwater mussels may not be charismatic, but are deemed to be deemed to be protected by federal and state agencies. This protects the entire river ecosystem. “They are beautiful animals and have value in their own right,” Ease said. “When we lose them, the world is losing something special.”
