mussells
Biologists measure, number and tag freshwater mussels from Deer Creek at Rocks State Park to reintroduce the species to the Patapsco River. (Credit: Maryland DNR)
Bringing back natural water filters in Maryland and beyond
The Maryland Department of Natural Resources has planted freshwater mussels into the river in hopes of restoring a population of molluscs that once lived in the waters. And the Maryland project is just one of many in the country attempting to save nature's water filters.
Freshwater mussel species, unlike those that dwell in salt water, are not eaten. But they do serve a large purpose for the ecosystem. They filter water. A lot of water.
In healthy mussel beds along the Delaware River Basin, there are about 200,000 to 300,000 mussels per every 2.5 acres. Those mussels can filter about 10 million gallons of water per day. Each year they filter about 10 tons of suspended matter—such as dirt, algae and pollutants— out of the water, Danielle Kreeger, senior science director at the Partnership for the Delaware Estuary, told EHN.
"Those are pretty big numbers. And by losing those mussel beds in our rivers and streams across the United States, we've lost nature's ability to help keep the water clean itself," she said.
Mussels are a good indication of water quality. If mussels are dying due to contamination that they are filtering in the water, it's a good indicator that the water is unsafe for human consumption, Monte McGregor, a mussel biologist and director of the Center for Mollusk Conservation in Kentucky, told EHN.
"They are basically canaries in the coal mines, so to speak. They are the species that are the best indicators of water quality and pollution in our rivers and streams across our country," McGregor said.
The need for restoration
Credit: Monte A. McGregor
To bring back mussels to the Patapsco, members of the Department of Natural Resources translocated mussels from rivers in Harford County. Next year, the mussels will be joined by ones currently being cultivated in Charles County, Maryland.
The mussels currently planted into the river bottom are low risk, Matt Ashton, a natural resource biologist with the DNR, told EHN. It's a demonstration project to see how the mussels do. If they do well, the Department of Natural Resources might try restoring a mussel facing extinction.
Freshwater mussels are native to Maryland's Patapsco River, but they haven't been in the river for decades, according to the MAryland DNR.
One reason was due to dams along the river, Ashton said. But some of the dams have come down and another is currently being torn down. A remaining dam has a fish ladder in place, which allows fish and eels to swim through the dam.
And Maryland isn't alone — due to human interference and climate change, mussels around the world have died off. McGregor said there are about 297 species of mussels in North America --- approximately 88 of them are threatened or endangered.
"They're declining at a rate higher than any other group [of species in Kentucky]. And why's that? We're not sure, but we think it's related to water pollution and change in habitat in the river and streams," he said.
Adding in mussels that are under special consideration, approximately 75 percent of the mussel species need help, Brian Watson, statewide mussel biologist for Virginia's Department of Game and Inland Fisheries, told EHN.
Pollution might come from industrial dumping or even personal use of pesticides and herbicides. Dams can also cause mussels to die off due to change in habitat and less access to fish, Watson said. Climate change leading to more rain is also causing a problem, Kreeger said.
With more rain, there is more flooding. It can also lead to more stormwater runoff, which along with flooding, can disrupt the river bottoms, displacing and possibly killing the mussels, Kreeger said. Climate change is also leading to sea level rise, which brings saltwater into the freshwater, and the mussels cannot survive in the brackish water, Kreeger added.
The mussel and the fish
Credit: Maryland DNR
Without fish or eels, many mussel species, including the ones found in the central Maryland river, cannot repopulate.
Mussel larvae are born as hitchhikers, and they attach to an eel or fish because they can move upstream. Once the larvae matures to a juvenile mussel and finds a nice place to call home, they drop off the fish and plant themselves. They'll remain in that area for the remainder of their lives.
Which can be a long time, as many mussel species live 50 to 70 years, with some living as long as 100, Kreeger said. And freshwater mussels aren't rooted in the same spot forever, she said. They can crawl, just not very far, which is why fish are needed to allow mussels to move their population up the river.
With the dams in Maryland coming down, there's hope the fish will be able to help mussels increase their populations in the Patapsco. But that might take five years, Ashton said.
Right now, the 300 mussels in the Patapsco are adults that were planted like seeds into the river. They were planted near Sykesville, Maryland, which is about 15 miles north of Ellicott City, where they will be safe from possible flooding and the dam removal, Ashton said.
Maryland residents won't likely see the mussels in the river because they bury themselves.
"They're out of sight and out of mind," Ashton said.
Bringing back the filters
Credit: Monte A. McGregor
Despite the various efforts to restore mussels, McGregor didn't think any mussel species had been removed from the endangered or threatened list.
"It took some 30 years for the bald eagle, so I expect it'll take that long for the mussel," he said.
His Center for Mollusk Conservation takes in mussels from outside of Kentucky, including Pennsylvania. The organization brought in 20,000 mussels from the Allegheny River and translocated them to the Licking River in Kentucky.
It also worked to release a mussel species known as purple cat's paw into rivers in Ohio, West Virginia and Tennessee, as well as Kentucky.
One of the reasons other states come to the Kentucky group is their ability to raise mussels via petri dish instead of fish. They have had success with about 70 species of mussels, McGregor said.
In Delaware, efforts to revamp mussel populations have been hampered by lack of funding, Kreeger said. The group has had success in about 1 percent of the river basin, but the organization needs more resources to be able to address the many rivers in the Delaware River watershed, she said.
Efforts are also underway in Virginia. There are two fish hatcheries, one in the eastern part of the state and one in the southwestern part, where mussels are produced and released. Between the two facilities, more than 15 million mussels have been produced, with more than 300,000 released, Watson said.
There is a significant discrepancy between the numbers because it may take years before a mussel is at a size where it can best survive in the river, Watson said. And because the facilities are working with various species, some more threatened than others, some of the mussels produced don't survive.
Mussel conservation and restoration is also worked on by the U.S. Fish and Wildlife Services, who have multiple projects, where fish biologist Tyler Hern works. Unlike the state efforts, the fishery Hern works out of usually assists other groups with smaller project.
And while Hern told EHN that it will be sometime before the mussels are restored to historic populations, he thinks that progress has been made.
"With the work the Fish and Wildlife service is doing with its partners I think in the last two decades we've moved the needle a tremendous amount on a number of species," Hern said. "And as we go we're identifying better ways to give these species the best chance they're going to have."
Help the mussels
Interested in ways to help the mussels? Here are a few ways, mussel biologists suggested people can get involved.
- Be aware of what might go into rivers. "When you're dumping things on the ground, it's going to go somewhere. It's going to go downstream," McGregor said.
- Help educate others about the mussels, especially those who may be able to make decisions about large projects that could disrupt mussel habitat.
- Participate in a mussel gardening project. Some organizations will give baby mussels to people for them to grow in ponds in their yards. This helps the mussels grow to adults.
- Reduce the amount of fertilizer, pesticide and herbicide used on lawns and gardens.
Miguel Llanos
Mussels don't stick around in acidic ocean water
PENN COVE, Wash. – Cookie tray in hand and lifejacket around chest, Laura Newcomb looks more like a confused baker than a marine biologist. But the University of Washington researcher is dressed for work.
Her job: Testing how mussels in this idyllic bay, home to the nation's largest harvester of mussels, are affected by changing ocean conditions, especially warmer and more acidic waters. It's a question critical to the future of mussel farmers in the region. More important, it's key to understanding whether climate change threatens mussels around the world, as well as to the food chains mussels support and protect in the wild.
"Along the West Coast, mussels are well-known ecosystem engineers," said Bruce Menge, an Oregon State University researcher who studies how climate impacts coastal ecosystems. "They provide habitat for dozens of species, they provide food for many predators and occupy a large amount of space, so are truly a 'dominant' species."
Breaking with 20 million years of tradition
Miguel Llanos
Carbon from greenhouse gas emissions has steadily turned seawater more acidic, disrupting organisms accustomed to slightly alkaline waters of the past 20 million years.
In the case of mussels, an earlier University of Washington lab study found that increased carbon dioxide weakens the sticky fibers, called byssus, that mussels use to survive by clinging to objects like shorelines or the ropes used by commercial harvesters.
"If byssal thread weakening does eventually become important," Menge added, "the consequences would be major if not catastrophic."
Newcomb's goal now is to apply in the real world what was learned in the lab. "Instead of spending a lot of time tightly controlling the temperature and pH conditions mussels grow in, I use the natural seasonal variation to try to answer the same questions," Newcomb said.
Newcomb's field office is the rear deck of a harvesting boat -- right between the toilet and the microwave. The quarters are cramped, but the view is grand: The blue waters of Penn Cove on Washington state's Whidbey Island are set against rolling bluffs and snow-capped mountains.
The University of Washington marine biologist is there courtesy of Penn Cove Shellfish, which is also the oldest and best known mussel operation in the United States. If you're a mussel fan, you've probably had a few – they're sold at Costco as well as upscale restaurants across the country.
Placing just-harvested mussels on her tray, Newcomb samples for size, thickness and strength. The mussels are grown on 21-foot-long ropes hanging from several dozen rafts in the bay, and Newcomb takes samples from two depths: Three feet and 21 feet. She also samples water temperature and pH levels at those depths.
Trouble in acidic waters
Miguel Llanos
Prior to the Industrial Revolution and the explosion of manmade CO2, ocean pH averaged 8.2. Today it's 8.1, a 30 percent increase in acidity on the logarithmic scale. Computer models peg ocean acidity at 7.8 to 7.7 by the end of the century at the current rate of greenhouse gas emissions.
Washington state is a bit ahead of that curve because ancient carbon stores in the deep ocean are periodically churned up by local currents.
The surprising lab discovery was that mussel byssus weakened by 40 percent when exposed to a pH of 7.5.
At Penn Cove, low pH levels are not uncommon – Newcomb has even seen 7.4 in the year that she's been sampling.
"We're worried they're going to see it more frequently," said Emily Carrington, Newcomb's graduate adviser and leader of the University of Washington team that published the earlier lab results.
The Penn Cove work follows well-publicized research that show oyster larvae in hatcheries along Washington's coast are having trouble forming shells because of the acidic waters.
"Mussels are the new oysters," Carrington said. But there's a twist: Mussels confirm that ocean acidification's impact extends in mollusks beyond an inability to form a shell.
The lab finding is "part of a growing body of evidence that ocean acidification alone and combined with other stressors will have effects beyond shell mineralization," said Terrie Klinger, a University of Washington marine sciences professor studying the impacts of acidification.
Other research, she said, shows more acidic seas spurs "changes in fish behavior and toxin production in harmful algae."
Miguel Llanos
Penn Cove Shellfish and the UW researchers joined forces after company harvesters saw empty patches on some cultivation ropes that should have had mussels. Was that due to weakened byssus?
"We had a significant amount two years ago, and little bit less last year," said Ian Jefferds, general manager at Penn Cove Shellfish. "The question arose, 'Was there something related to that?'"
The concern about what the industry calls "slough-off" goes well beyond Penn Cove.
"We know that mussel slough-off has periodically been an issue but we don't know why," said Margaret Barrette, director of the Pacific Coast Shellfish Growers Association.
It's a global issue. Among major shellfish producers, New Zealand is creating an acidification monitoring network while researchers in Spain are planning a study similar to that in Penn Cove.
And across the Mediterranean, mussel farmers have reported problems. "A great majority of producers experienced important difficulties in past years as a consequence of summer heat waves," said Luis Rodrigues, a researcher with a European Commission panel studying acidification.
Those issues include slough-off in Italy and Montenegro, as well as thinning of shells and even die-offs in waters that topped 82.4 degrees F.
A related lab study showed "total mortality" of mussels when exposed to waters above 82.4 degrees, said researcher Frederic Gazeau.
That team also "observed a very clear impact of acidification on the capacity of mussels to produce their byssal thread," noted Gazeau. "At low pH, it was very easy to pick up mussels individually; they could not attach themselves anymore."
Miguel Llanos
Of course, it's not just loss on the farms that worry scientists. In the wild, mussels form vast beds along coastlines, and some areas have seen slough-off as well.
"It's quite common in California in recent years," said Herb Waite, a University of California, Santa Barbara, biochemist who studies mussels. "A favorite collecting spot will suddenly disappear."
Any widespread slough-off in the wild could have other repercussions as well. It hasn't happened yet, but researchers are worried.
Mussel beds in sandy areas "stabilize shores against erosion," Waite noted, and any loss there could expose beaches to the erosive power of waves.
Carrington thinks her team's research could lead to an "early warning system" for a global mussel farming sector valued at $1.5 billion a year. Establishing pH thresholds, farmers could better monitor areas and, if needed, seek out safe havens in less acidic and cooler waters.
"It does matter where in the water mussels are," Newcomb added, noting that even preliminary results suggest growing them closer to the surface tends to mean less acidity. However, a trade-off there can be warmer temperatures.
The research will need two more years of data gathering before any definitive conclusions, but Carrington said the earlier lab tests underscore the need for field data.
"Would you be worried about being weakened by 40 percent?" she asked. "I would be."
Miguel Llanos is a freelance reporter based in the Pacific Northwest.
ORIGINAL REPORTING
MOST POPULAR
CLIMATE
