Scientists seeking cause of huge freshwater mussel die-off

A pile of recently dead freshwater mussels are piled along the shore of the Clinch River near Wallen Bend, Tennessee. (AP)
Short Url
Updated 17 December 2019

Scientists seeking cause of huge freshwater mussel die-off

  • Freshwater mussels range from about the size of a large button to the size of a billfold
  • Mussels benefit the people who use their rivers as a source of drinking water

KYLES FORD, Tennessee: On a recent late fall afternoon at Kyles Ford, the white branches of sycamore trees overhung the banks of the Clinch River, leaves slowly turning yellow. Green walnuts covered the ground.

The shallow water ran fast and cold over the rocky bottom, but it was littered with the white shells of dead mussels.

Freshwater mussels range from about the size of a large button to the size of a billfold, but the work they do for ecosystems is enormous. They can filter around 8-10 gallons of river water each day, cleaning it of algae, silt and even heavy metals and making the whole river a better environment for fish, amphibians, plants and bugs. Mussels also benefit the people who use their rivers as a source of drinking water.

That’s why scientists are working quickly to discover the cause of a massive mussel die-off on the Clinch and understand whether it is related to similar die-offs on at least five US rivers and another in Spain.

The Clinch River, winding 300 miles through Appalachia, is home to 133 species of fish and is one of the most important rivers for freshwater mussels in the world, with 46 different species — more than in all of Europe.

“I always try to get people to call this area a temperate Amazon, because the biodiversity here really is off the charts,” biologist Jordan Richard, with the US Fish and Wildlife Service, said recently as he stood in waders, surveying the mussel population at Kyles Ford, a rural community of around 525 near the Virginia border.

Richard slogged through thigh-deep water in search of pheasantshell mussels, until recently one of the most abundant species on the river. He spots them easily although to the untrained eye, they aren’t so obvious. Mussels bury themselves in the riverbed, digging in with their single foot and leaving only a crescent of their shells visible.

In 2016, Richard noticed the pheasantshells were dying in large numbers — the population dropping from 94,000 in 2016 to less than 14,000 this year on a 200-meter (219-yard) stretch. He estimates hundreds of thousands, possibly millions, have died in the larger river.

Richard found reports of similar die-offs over the years in rivers around the world, but he didn’t find many answers.

Over the past century, mussel populations everywhere have declined steeply due to pollution, habitat loss and climate change, yet the current decline looks to be something different.

Richard and a team of scientists suspect an infectious disease. By comparing healthy pheasantshell mussels with dying ones, the team is narrowing down a list of suspected pathogens.

“All living things are chock-full of microorganisms, and we don’t have any sort of map for what is healthy inside a mussel,” Richard said.
University of Wisconsin epidemiologist Tony Goldberg is helping with the investigation. He specializes in wildlife diseases of unknown cause — and recently he’s been busy.

“Along with invasive species, we’re seeing invasive pathogens,” Goldberg said. “Often it’s the coup de grace for a species that is holding on by a thread.”
Disease is a big part of the global extinction crisis, he said. For example, white nose syndrome was first discovered in a single New York cave in 2007 and has since killed millions of bats, and chytrid fungus is responsible for the demise of tree frogs and about 200 other amphibian species worldwide.

But Goldberg is hopeful the freshwater mussel team, which includes scientists from the US Geological Survey and a nonprofit conservation group, will be able to find the cause of the mussel die-offs and a way to stop them.

“I see it as a race against time, not an impossible task,” Goldberg said. “We’re all motivated by the sinking realization that if we lose these mussels, the rivers we all love are never going to be the same.”

The Clinch, which is relatively pristine on its upper reaches, has seen 10 mussel species go extinct — it used to have 56. Another 20 species there are endangered, including mussels with evocative names such as fluted kidneyshell, snuffbox, birdwing pearlymussel, and shiny pigtoe.

Preliminary results indicate that whatever is killing the pheasantshell mussels on the Clinch is not the culprit in other die-offs under investigation in Wisconsin, Michigan, the Pacific Northwest and Spain.

“There’s not some mussel Ebola sweeping across the world to take out every mussel everywhere,” Goldberg said.

That also means there’s no single cure for what’s killing them.

In Spain, biologist Rafael Araujo is working with Goldberg to figure out what is killing the last of the endangered Spengler’s freshwater mussels in the Imperial Canal on the Ebro River.

“We know that the problem is environmental (dams, water pollution, excess fertilizers, pesticides, exotic species, lack of water, etc.), but we also think that there could be a pathogen (bacteria and/or virus) that is making things worse,” Araujo wrote in an email.

In Oregon and Washington, Emilie Blevins is studying the die-off of western pearlshell mussels in her role as a biologist with the Xeres Society for Invertebrate Conservation.

Blevins likens mussel beds to coral reefs in terms of their diversity and contributions to other aquatic life. But she acknowledges, “They just don’t get the spotlight of some other big, beautiful species. A big part of all of our work is ... spotlighting how important they are because if we don’t value them, they’re not going to be around.”


Thai protesters challenge monarchy as huge protests escalate

Updated 13 min 29 sec ago

Thai protesters challenge monarchy as huge protests escalate

  • Protesters have grown ever bolder during two months of demonstrations against Thailand’s palace and military-dominated establishment

BANGKOK: Openly challenging the monarchy of Thai King Maha Vajiralongkorn, thousands of protesters marched in Bangkok on Sunday to present demands that include a call for reforms to curb his powers.
Protesters have grown ever bolder during two months of demonstrations against Thailand’s palace and military-dominated establishment, breaking a longstanding taboo on criticizing the monarchy — which is illegal under lese majeste laws.
The Royal Palace was not immediately available for comment. The king, who spends much of his time in Europe, is not in Thailand now.
The marchers were blocked by hundreds of unarmed police manning crowd control barriers.
Protest leaders declared victory after handing police a letter detailing their demands. Phakphong Phongphetra, head of the Metropolitan Police Bureau, said on a video broadcast from the scene that the letter would be handed to police headquarters to decide how to proceed.
“Our greatest victory in the two days is showing that ordinary people like us can send a letter to royals,” Parit “Penguin” Chiwarak, told the crowd before it dispersed.
At the biggest demonstration in years, tens of thousands of protesters on Saturday cheered calls for reform of the monarchy as well as for the removal of Prime Minister Prayuth Chan-ocha, a former junta leader, and a new constitution and elections.
Shortly after sunrise on Sunday, protesters cemented a plaque near the Grand Palace in Bangkok in the area known as Sanam Luang, or Royal Field.
It reads, “At this place the people have expressed their will: that this country belongs to the people and is not the property of the monarch as they have deceived us.”
Government spokesman Anucha Burapachaisri said police would not use violence against protesters and it was up to the police to determine and prosecute any illegal speech.
Bangkok authorities would need to determine whether the plaque is illegal and if it is it would need to be removed, Bangkok’s deputy police chief Piya Tawichai told reporters.
Far from all Thais support the new plaque, which resembles one that had commemorated the end of absolute monarchy in 1932 and which was removed from outside a royal palace in 2017, after Vajiralongkorn took the throne.
Prominent right-wing politician Warong Dechgitvigrom said the actions of the protesters were inappropriate and that the king was above politics.
“It didn’t achieve anything,” he said. “These actions are symbolically against the king, but the king is not an opponent.”
Thai authorities have said criticizing the monarchy is unacceptable in a country where the king is constitutionally “enthroned in a position of revered worship.”
Protests that began on university campuses have drawn increasing numbers of older people. That includes red shirt followers of ousted populist prime minister Thaksin Shinawatra who had clashed for years with pro-establishment yellow shirts before Prayuth seized power in 2014.
“The new generation is achieving what their parents and grandparents didn’t dare. I’m very proud of that,” said Somporn Outsa, 50, a red shirt veteran. “We still respect the monarchy, but it should be under the constitution.”
Protesters say the constitution gives the king too much power and that it was engineered to allow Prayuth to keep power after elections last year. He says that vote was fair.
The next protest is scheduled for Thursday. Protest leaders called on Thais to take Oct. 14 off work to show their support for change.
“Radical change is hard in Thailand, but the movement has at least kept the momentum going,” said Titipol Phakdeewanich, dean of political science at Ubon Ratchathani University.