By Greg Barnes
In the 1980s, the water in Lake Michigan was a cloudy blue-green soup of algae and other living microorganisms.
Fast forward to today. The lake is so clear that bathers standing at the bottom of the neck can easily see their feet on the bottom.
And that’s not a good thing.
Invasive zebra mussels, first detected in Michigan’s Lake St. Clair in 1988, have multiplied by the billions in the Great Lakes, profoundly altering its ecosystem. While mussels have mastered the filtering of algae and water pollutants, they threaten the Great Lakes fishing industry, clog municipal drinking water intakes, and have spread far inland into the rivers, streams and other lakes.
Researchers now fear the zebra mussels are coming to North Carolina.
At the end of March, the NC Environmental Quality Department issued a statement saying that the small zebra mussels – scientifically known as Dreissena polymorpha – had been found in moss balls at pet stores in North Carolina and 20 other states. Moss balls, which are sponges of spongy green algae, are commonly imported from Ukraine and used here by aquarium enthusiasts.
Since the discovery of the zebra mussels in the moss balls, wildlife researchers have scrambled to determine how long they have been entering this country. They are also trying to educate people on the best practices for destroying moss balls, said Todd Ewing, an aquatic wildlife diversity program supervisor at the NC Wildlife Resources Commission.
“The best thing to do is not to let the genie out of the bottle and the best – the only – way to do that is to educate the public about the risk and use best practices when it comes to disposal. water the aquarium and cleaning your boats, ”Ewing said.
Small mussels, huge risks
Zebra mussels are believed to have entered the Great Lakes from ballast water discharged by large ships from Russia and other European countries. It didn’t take long for the mussels to take root and spread.
According to Michigan State University, cleaning up zebra mussels in the United States cost between $ 1 billion and $ 1.5 billion between 1989 and 2004, with some reports putting the damage as high as $ 5 billion.
“The ability of zebra mussels to attach themselves to a variety of surfaces means that they are able to cover large areas of the lake bottom and also disrupt water intake and drains in factories, power plants. electrical, irrigation systems and boats by inhabiting and possibly restricting it, ”MSU Extension / Michigan Sea Grant said in a three-part report in 2015.
There is also a human health factor. Ewing said zebra mussels love to devour algae – but not the blue-green algae called Microcystis aeruginosa, which can produce a family of toxins called microcystins.
Algal blooms containing microcystins have become almost common in some North Carolina
Zebra mussels “do not tend to filter out small blue-green algae as much, which leads to higher concentrations of these blue-green algae, because they then do not have competition with some of the other algae”, Ewing mentioned. “So these blue-green algae are becoming more abundant.”
He said zebra mussels attach themselves to anything that has a hard surface, including boats, docks, piers, and even other mollusks and snails. Another health hazard is that people get cut by the sharp edges of zebra mussels, Ewing said.
Greg Cope, Distinguished Professor in the Agromedicine Program at NC State University, has studied zebra mussels – and native bivalves – for 30 years. In large areas of the Great Lakes, Cope said, the zebra mussel has essentially eliminated clams and other native molluscs by attaching themselves to them and preventing native mussels from opening their shells to feed, filter and breathe. The State Wildlife Commission lists 25 species of shellfish in North Carolina that are already endangered.
Zebra mussels thrive on phytoplankton, microscopic marine organisms that are found at the bottom of the food chain. In the Great Lakes, phytoplankton are swallowed up by zooplankton, which is eaten by alewife and other small fish, which are eaten by the larger fish up to the top of the range – chinook salmon.
In 2018, the Chicago Tribune reported on US Fish and Wildlife Service research that found Great Lakes chinook harvests fell by about 10 million pounds between the mid to late 1980s to about 3 million pounds. The zebra mussel was largely to blame.
Bodies of Water in North Carolina
The good news is that few North Carolina lakes, rivers, and streams seem to be suitable for large zebra mussel infestations.
In 1997, North Carolina state researcher Barbara Doll conducted a study to determine which of North Carolina’s waterways would be most susceptible to mussels.
Doll’s research examined 338 of the state’s surface waters. She based her study on five parameters: calcium, pH, salinity, temperature and dissolved oxygen. Zebra mussels need high levels of calcium to grow and build their shell. They are freshwater mussels that dislike salinity and need high levels of dissolved oxygen and pH to thrive. At the time of her report, Doll said, zebra mussels had not invaded warmer climates, such as Louisiana and Texas, so more studies are needed on the temperature issue.
Doll said that if any of the parameters were not met, it would almost certainly rule out the ability of zebra mussels to invade on a large scale.
“They wouldn’t have the kind of water chemistry to, you know, really thrive,” she says. “They might appear, but their persistence might be a bit hampered because the conditions are not optimal.”
Doll’s report showed a map with about 44 waterways in the state meeting – or most of the time – all settings. The map did not show the waterways. But Doll said most of the water bodies in the western part of the state have low acidity and those in the far eastern part have high salinity, so the chances of zebra mussels invading those areas. are negligible.
“In some ways it was a bit of a relief that a lot of our waters weren’t too much in the kind of perfect match for zebra mussels,” Doll said.
But the threat remains for North Carolina’s lakes and rivers that match well. Zebra mussels have invaded some waterways in neighboring Tennessee and Virginia, Cope said.
“We were a little worried about the possibility of this happening and to our knowledge it is not, so I think by whatever means we have been very lucky,” he said. -he declares. “Vigilance, I think, is part of it.
Respond to the threat
One need only look at the response from the US Geological Survey to understand just how much of a threat zebra mussels pose to the country.
On February 25, an employee at a pet store in Seattle, Washington, filed a report in the Geological Survey database saying he recognized a zebra mussel in a moss ball.
After obtaining confirmatory information, including a photograph, USGS Fisheries Biologist Wesley Daniel immediately notified the Washington State Aquatic Invasive Species Coordinator and contacted the invasive species managers of the ‘USGS and the US Fish and Wildlife Service.
According to a statement on the USGS website, Daniel then visited a store in Gainesville, Fla., And found a zebra mussel in a moss ball there.
“At the moment.” the statement said, “Federal experts on non-native species have realized the problem is vast.”
U.S. officials have teamed up with the Pet Industry Joint Advisory Council, state wildlife agencies and regional aquatic invasive species management groups in an effort to further investigate the threat, educate the masses and control the situation.
“I think it was a great test of the rapid response network we’ve built,” Daniel said in the release. “Within two days, we had a coordinated response from states, federal government and industry.”
In North Carolina, Ewing said, officers from the NC Wildlife Resources Commission have deployed to visit nearly every pet store in the state.
“Most of the pet stores that had foam balls voluntarily took them off the shelves and agreed to get rid of them and get rid of them,” Ewing said.
He said officers found contaminated foam balls in the agency’s nine North Carolina districts.
To date, no zebra mussels from mossballs have inhabited the waterways of the United States.
“I want to reiterate that education is the most effective thing we can do by far, because once they’re in the water there’s not much you can do, du less on a large scale, ”Ewing said.
Cope said he spent the start of his career in Wisconsin trying to find effective ways to eradicate zebra mussels. He said he had strayed from this area of research, but others have taken up the torch.
As new methods continue to be tried, Cope said, no one has yet found a way to eliminate or reduce the mussel population without harming native species.