Euan Reavie presents at River Talks. Image credit: Michael Anderson

Harmful algal blooms are becoming more of a concern in the St. Louis River Estuary and Lake Superior. The reasons behind this were described during the November River Talk by Euan Reavie, senior research associate at the University of Minnesota’s Natural Resources Research Institute.

Harmful algal blooms, also known as HABs, appear as mats of bright green algae that float on the surface of the water or sometimes lay on the bottoms of large rivers or lakes. Not all algal blooms are toxic, but some are, and scientists are looking into what triggers the release of toxins in the blooms.

“Based on anecdotal and real observations, it does seem to be something that’s getting worse in Western Lake Superior,” Reavie said. “Whoever thought we’d be getting algal blooms out in the nutrient-poor waters of Lake Superior, making their way all the way up to the Apostle Islands?”

Water quality in the St. Louis River has improved over the years thanks to sanitary sewer districts coming online in Duluth and Superior in the 1970s, environmental regulations, and cleanup efforts. However, excess nutrients such as phosphorus and nitrogen are still of concern and are a focus of attention from management agencies.

Reavie’s research team came into the picture in the early 2010s when they were asked to research nutrient levels in hopes of confirming that they were decreasing. They collected sediment samples (cores) to reconstruct the history of nutrients in the estuary. The scientists analyzed the samples for different types of fossil algae, which offer signals about what types of nutrients were available in the past because different algae species prefer different levels of nutrients.

Diatoms are the most abundant type of algae in the Western Lake Superior system. Reavie showed how the assemblages of these species changed after European settlement and after water cleanup efforts in the 1970s.

Over the past several years, algae blooms have been noted along the shore of Lake Superior near Cornucopia, Wisconsin, and in the estuary at Barker’s Island and Allouez Bay. Reavie said that sediment samples from the present day in sheltered bays like Allouez Bay show diatom species that like high levels of nutrients. He said the data show a “fairly consistent” increase in phosphorus in the system. “Not good news for the bays in the estuary,” he said.

The team also found cyanopigments in the samples, which indicate recent increases in algae. “There appear to be some new problems in these nearshore areas despite the fact that we’ve reduced the flux of nutrients into the system. Something new is going on here,” Reavie said.

One culprit could be more intense storms due to climate change. Storms wash a lot of nutrients from the land into the water and then the currents carry them through the estuary and harbor, and out into Lake Superior along its South Shore.

“Just knowing that the blooms tend to follow storms is not enough. There’s probably a seasonal aspect to all this, as well,” he said. Warmth is one factor, but Reavie said there have also been algae blooms under the ice. Low dissolved oxygen levels in water could be another factor, resulting in a chemical reaction that releases stored nutrients in sediments.

His team has begun developing an early warning system to sort out what is going on. It involves incorporating weather data, water quality data and algae data from eight stations in the estuary. They hope to offer initial findings at the March 2024 St. Louis River Summit.

For more information, visit the team’s website.

The next River Talk is scheduled for March 13, 2024. Brandon Krumwide with the National Oceanic and Atmospheric Administration will present, “What Lies Below? Underwater Mapping of the Great Lakes,” at 6:30 p.m. in the Lake Superior Estuarium (3 Marina Drive, Superior, Wisconsin).

The post Understanding harmful algal blooms in the St. Louis River Estuary presents challenges first appeared on Wisconsin Sea Grant.

Original Article

Blog | Wisconsin Sea Grant

Blog | Wisconsin Sea Grant

https://www.seagrant.wisc.edu/blog/understanding-harmful-algal-blooms-in-the-st-louis-river-estuary-presents-challenges/

Marie Zhuikov

The River Talks, a series of informal science presentations, returns at 6:30 p.m. Wednesday, Oct. 11, for the season with “Duluth’s Lost Industries Along the St. Louis River,” an in-person presentation by local historian and author, Tony Dierckins. His talk will be held at the Lake Superior Estuarium (3 Marina Dr., Superior, Wis.). Refreshments will be provided.

The shores of the lower St. Louis River were once lined with ore and coal docks, grain terminals, flour and lumber mills, steel plants, shipyards and dozens of other manufacturers. From the brownstone quarries of Fond du Lac to Gary New Duluth’s giant Minnesota Steel Plant, this presentation explains the rise and demise of the industries that both built the Zenith City and altered and contaminated Lake Superior’s largest tributary. 

Tony Dierckins has written over two dozen books, many of which celebrate historic Duluth, Minnesota. He is a three-time recipient of the Northeast Minnesota Book Award, a past recipient of the Duluth Depot Foundation’s Historic Preservation and Interpretation Award, and the publisher of Zenith City Press. 

Other River Talks will be held Nov. 8, 2023, and Jan. 10, Feb. 7, March 13, April 10 and May 18, 2024. For more information, visit the River Talks page: go.wisc.edu/4uz720.

The River Talks are sponsored by the Lake Superior National Estuarine Research Reserve and the Wisconsin Sea Grant Program.

 

The post River Talks resume with “Duluth’s Lost Industries” first appeared on Wisconsin Sea Grant.

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Marie Zhuikov

David Grandmaison, Wisconsin Dept. of Natural Resources, poles through a wild rice bed in the St. Louis River. Image credit: Marie Zhuikov, Wisconsin Sea Grant

A co-worker and I were invited to attend a day of Manoomin (Wild Rice) Camp on the St. Louis River in Duluth, Minnesota. The camp flier said, “Join us in a guided paddle to the wild rice restoration sites and welcome manoomin back to Gichi Gami Ziibi (the St. Louis River). Try your hand at harvesting and experience each step in the finishing process (drying, parching, jigging and winnowing).”

That sounded good to us, so with wild rice harvesting permits in hand, we met in the Fond du Lac neighborhood of Duluth near the Wisconsin border. The event was hosted by the 1854 Treaty Authority, the Wisconsin Department of Natural Resources (WDNR), the Lake Superior National Estuarine Research Reserve and The Nature Conservancy in an area that had been seeded with wild rice three or four years previously.

We were met by Marne Kaeske, cultural preservation specialist with the 1854 Treaty Authority, Martha Minchak and David Grandmaison, St. Louis River wild rice and habitat restoration coordinator with the WDNR. After a sage smudging ceremony and a chance to offer tobacco to the river as the Ojibwe do, they gave us a brief orientation to where the rice bed was located and how to harvest it.

“The rice needs us and we need the rice,” said Minchak, a retired Minnesota Department of Natural Resources wildlife manager. “In places where it’s not harvested anymore, it’s disappeared. Kind of like sweet grass, it needs to be pulled up and picked. Rice needs to be harvested to reseed itself. We’re here to celebrate that today.”

The St. Louis River. Image credit: Marie Zhuikov, Wisconsin Sea Grant

Under a blue sky and calm winds, my co-worker (who shall remain nameless for reasons that will become clear soon) and I clambered into our canoe with our life jackets, a pair of rice knocking sticks and long pole. We paddled toward the wild rice bed where Grandmaison was stationed in a motorboat and kayak to aid us ricers. We spotted a gleaming white pair of trumpeter swans and we watched as a small kettle of hawks circled overhead.

We must have not done our opening ceremonies correctly, because things did not go as planned. I was in the bow of the canoe and my job was to use the rice knockers to coax the rice seeds off the plants. My co-worker was in the stern to pole us through the rice bed. That all went fine, for a while.

Marie uses rice knockers to harvest wild rice in the St. Louis River. Image credit: Sharon Moen, Wisconsin Sea Grant

The soft swishing sounds of the aluminum canoe pushing through the thick rice stand combined with the gentle patter of rice seeds falling into it as I gently bent the rice with one knocker and used the other to tap the plants was soothing. The rice stand had already been visited by other groups earlier in the week. That, combined with a heavy rain the day before, made for a sparse harvest. Still, oblong seeds with long grassy tails slowly filled the bottom of our canoe. Some of the seeds were purple, others were tan. A small sora rail flushed several times as we passed. This secretive water bird needs marshes and rice beds as nesting habitat.

My co-worker began poling us through the shallow rice bed sitting down at first. Then she stood for the task, which is how it is traditionally done. As the manoomin continued accumulating in our canoe, the push pole got stuck in the soft muck and she lost her balance.

Into the chilly river we went, rice and all!

Our shouts of surprise and splashes as we struggled to stand in the deep muck alerted Grandmaison to our plight. He paddled over in his kayak and tied a rope onto our swamped canoe. My co-worker and I waded through the waist-deep water, holding onto the canoe through the wild rice beds until we reached shore, which was about 100 yards away.

The swamped ricing canoe. Image credit: David Grandmaison, Wisconsin Department of Natural Resources

There, we were able to tip the canoe over and empty most of the water (and any wild rice that remained). We took it all in good stride, however, laughing at our plight and commenting about what a good story this would make. I thought up the title of this blog post on the spot. There’s nothing like a real-life experience to provide creative inspiration!

Our misadventure was also probably good for the rice bed. Wild rice is an annual plant and as Minchak mentioned, it needs to be seeded every year to prosper. We just dumped a whole lot of seeds back into the river for next year. Maybe that’s what the wild rice gods wanted us to do?

We were worried about our cell phones and other electronic devices that spent a short time in the water. But our phones, at least, seemed functional.

Cold and wet, my co-worker and I decided we’d had enough ricing for the day. We paddled back to the landing and emptied the remaining water from the canoe, pulling it on land and turning it over.

From the time we overturned in the rice bed to the time we reached the landing we’d been wet for two hours. We headed home for warm, dry clothes. We would miss the rice processing demonstration and a wild rice-themed meal. We were disappointed to cut the experience short.

However, I happened to have a special lunch awaiting me at home: wild rice soup. I swear, I did not plan that. I just worked out that way.

My co-worker and I certainly got “immersed” in the process of harvesting wild rice. The experience was memorable and was not one we could have had only a few years ago, before efforts to restore rice took off in the estuary.

But if we ever do it again, I’m going to volunteer to be the poler.

Marie’s clothes drying out at home. Image credit: Marie Zhuikov, Wisconsin Sea Grant

The post Wild ricing in the St. Louis River Estuary: An immersive experience first appeared on Wisconsin Sea Grant.

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Marie Zhuikov

Molly Wick. Submitted photo.

The River Talks will be held at 7 p.m. Wednesday, Nov. 9, at the Lake Superior Estuarium (3 Marina Dr., Superior, Wis.), with “Tell us What you Love About the River,” an in-person presentation by Molly Wick, Lake Superior Reserve Margaret A. Davidson Fellow, who will describe a study she designed to help environmental managers understand how the community benefits from local lakes, rivers and streams and how this work could help make those benefits more accessible to everyone. Wick will invite everyone to take the waterway benefit survey, found here: z.umn.edu/waterwaybenefits. A youth panel will round out the discussion with their stories about why the St. Louis River is important to them. Refreshments will be provided.

Other River Talks will be held Jan. 11, Feb. 8, March 8, April 12 and May 10, 2023. The March talk will be held in conjunction with the St. Louis River Summit. For more information, visit the River Talks page: go.wisc.edu/4uz720.

The River Talks are sponsored by the Lake Superior National Estuarine Research Reserve and the Wisconsin Sea Grant Program.

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Marie Zhuikov

Mural #2 in the Superior Public Library by Carl Gawboy. It shows the area where the Ojibwe settled on Wisconsin and Minnesota points on Lake Superior and how the points were separated by a giant otter. Image taken with permission by Marie Zhuikov, Wisconsin Sea Grant.

During the latest St. Louis River Summit, I had the chance to attend a field trip to the library in Superior, Wisconsin. What’s in a library that could relate to the summit? A series of 35 murals line its walls, showing the history of the area. Many feature the St. Louis River, Duluth-Superior Harbor and Lake Superior.

The murals were painted over 10 years by artist Carl Gawboy, an Elder enrolled in the Bois Fort Band of Chippewa. The murals begin with the Ojibwe creation story and continue through the 20th century, reflecting how people have interacted with the landscape through time.

Local historian and retired librarian Teddie Meronek led the tour. “I like to say I was here at the birth of the murals, but that started long before any paint went on canvas,” Meronek said. She described how Paul Gaboriault, the library director who commissioned the murals, was a former co-worker of Gawboy’s. Gawboy was born in Cloquet, Minnesota, and grew up on a family farm outside of Ely. He eventually taught at Ely High School, which is where he met Gaboriault. The friends both ended up back in the Twin Ports.

To research the murals, Meronek studied Gaboriault’s and Gawboy’s correspondence. She said the library used to be a Super One grocery store. “If you really look at this building it was just a big warehouse. It wasn’t built for a library. Dr. Gaboriault knew, in his way, that it needed something, and the first thing he thought of were murals.”

The second mural in the series shows the story of how the Superior Harbor opening was created through Wisconsin Point. A giant otter digs as a Native man approaches.

“The great otter represents the Ojibwe religion,” Meronek said. “He is breaking an entryway from Lake Superior into the harbor. The human figure is Nanabozho. He is bringing arts and fire to the land. That was Carl’s interpretation of the legend. The otter is pictured as being so large because it’s representing power.”

According to Gawboy, Lake Superior ties all the murals together, Meronek said. “You can’t always see it in every mural but it’s there. It influences what is going on, which is very true. I’ve lived three blocks from the bay of Lake Superior every day of my life and I can tell you there’s not a day that goes by that the lake doesn’t influence you in some way.”

The location of the horizon line also links the paintings. Meronek said it’s in the same place in each image. As she walked past the murals, she described each one, sharing her impressive knowledge of local history along with personal observations. Other murals include notable buildings and personages, as well as historic events.

Meronek ended the tour on a somber note at a mural of the Edmund Fitzgerald. She often listens to Gordon Lightfoot’s song about the ill-fated ship. “There’s one line in it that always makes me cry: ‘Does anyone know where the love of God goes when the waves turn the minutes to hours.’ Always beware of Lake Superior, right? I can’t even put my foot in it, it’s too cold! What a beautiful thing though, isn’t it? It’s the greatest of the Great Lakes, right? An inland ocean.”

If you’re ever in Superior, stop in the library and take a look. Of course, if you’re not a Superior resident, you can’t check out a book, but you can check out the murals, so to speak. Not planning a visit soon? You can also see the murals online.

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Marie Zhuikov

Owners of steel structures on inland lakes and a river in northern Minnesota are reporting the same kind of corrosion as seen in the Duluth-Superior Harbor and other harbors along Lake Superior. A structural engineering firm reported it has designed and overseen replacement of gates on dams along the St. Louis River, far removed from Lake Superior water, because of the corrosion.

Along with partners, Gene Clark, retired Wisconsin Sea Grant coastal engineer, devoted considerable energy into ferreting out the causes of and ways to mitigate this corrosion, which can lead to costly harbor infrastructure replacement.

The accelerated corrosion of steel pilings in the Duluth-Superior Harbor was first noticed in 1998. Researchers funded in part by the Wisconsin and Minnesota Sea Grant programs eventually identified microbes as the culprit combined with a complicated interaction between water and the steel. Bacteria form small lumps, or tubercles, on the steel. The lumps limit oxygen and allow small amounts of copper in the water to interact with and dissolve the steel, which results in pockmarks and holes that compromise steel structures.

A steel research “coupon” removed from the Duluth Superior Harbor in 2007 shows freshwater biocorrosion tubercles. Image credit: Wisconsin Sea Grant

Experts brought together to investigate the issue blamed water chemistry specific to Lake Superior. However, those still tracking the issue have discovered this microbially influenced corrosion problem is more widespread.

Chad Scott, principal at AMI Consulting Engineers, initially alerted harbor industries about the corrosion issue in 1998 when he was a diver inspecting structures in the Duluth-Superior Harbor. Scott said during the past few years his company has worked with the U.S. Army Corps of Engineers to place steel samples (or coupons) in the St. Louis River at the Thompson Dam, Scanlon, Cloquet and near Cotton.

“At every single location along the river, the steel had the same tubercles on them,” Scott said. “So, what that tells me is, what’s coming to the harbor is coming down naturally from inland in Minnesota.”

Scott said his firm designed and oversaw replacement of gates on the Fond du Lac Dam and the Sappi Dam in Cloquet.

“They were all heavily pitted. It looked just like harbor corrosion,” Scott said. He’s also had friends report biocorrosion on their docks on Fish Lake, Island Lake and Grand Lake. He’s seen firsthand the dock posts covered by corrosive tubercles on those lakes.

A steel dock post on Wilson Lake near Cotton, shows the same biocorrosion tubercles as those found in the Duluth Superior Harbor. Image credit: Marie Zhuikov, Wisconsin Sea Grant

Randall Hicks, professor emeritus at the University of Minnesota Duluth, has worked for years to understand the microbiology behind the corrosion. He said he has seen the tubercles on his own dock on Barrs Lake near Two Harbors. He has also identified them in photos from a dock on Wilson Lake near Cotton.

“I don’t think it’s just a regional problem,” Hicks said. “I think it’s been happening all along for a long time in places where conditions are right.” Those conditions include the presence of sulfate-reducing bacteria and iron-oxidizing bacteria, a source of dissolved sulfate and iron, and low-oxygen conditions such as those sometimes found in spring water.

Hicks described how the process begins when a clean sheet of steel is placed in water. “Different bacteria will attach to the surface and form a biofilm first.” Dental plaque is a common example of a biofilm. Microorganisms multiply and create a thin but tight layer on teeth. In this case, the biofilm layer is on steel.

“As that biofilm grows, we see a lot of iron-oxidizing bacteria – they’re aerobic microorganisms,” Hicks said. He explained that as the iron-oxidizing bacteria next to the steel surface use up oxygen, sulfate-reducing bacteria, bacteria that can live without oxygen, become common. “It’s really their activities in combination with activities of the iron-oxidizers in the biofilm that accelerate the loss of steel from the surface of the metal.”

Jim Sharrow, retired director of planning and resiliency with the Duluth Seaway Port Authority, said the corrosion bacteria are not an invasive species. “They’re indigenous to this area. They’re all over.”

The Canadian Northern dock in the Duluth Superior Harbor shows damage caused by freshwater microbial corrosion in 2007. Image credit: Wisconsin Sea Grant

Previous research identified coatings that can be used to protect steel. Hicks is now working on ways to fool the bacteria in the first place. Hicks and Mikael Elias, associate professor from the University of Minnesota Twin Cities, have found that adding a lactonase enzyme into a steel coating can reduce the biofilm produced, change the biofilm community and reduce the amount of corrosion. The lactonase enzyme works by destroying signaling molecules that the bacteria on steel produce to sense each other – in essence, fooling the bacteria into thinking they are alone, so “they don’t turn on genes to produce a biofilm,” Hicks said.

The nontoxic coating enzymes only last a month or two before degrading or diffusing out of the coating but Hicks said that, compared to untreated steel, the enzymes have reduced corrosion by 50% for at least two years, which was the length of their study.

“Hopefully, these enzymes can have an impact even farther out. If you’re in the shipping business and you expect a steel structure to last 100 years, then all of a sudden you have to replace it every 50 years because of the corrosion, that’s a big economic impact – and that’s just with doubling the corrosion rate. If we can reduce the rate, we don’t need to have a big impact to really extend the lifetime of structures quite a ways down the road,” Hicks said.

The University of Minnesota has applied for a patent for the lactonase enzyme coating. Hicks and Elias have also conducted tests in Lake Minnetonka and the Mississippi River to see if the same mechanism in the enzymes that inhibits biofilms from forming on steel inhibits larger invasive and nuisance organisms like zebra mussels and barnacles from attaching to underwater structures.

Elias said their experiments, funded by the Minnesota Environment and Natural Resources Trust Fund*, were successful. More recently, they added sites in sea water. Their pilot experiments in Florida show promise.

Until the lactonase enzyme coating becomes commercially available, what should cabin dock owners do to protect their steel from biocorrosion? Sharrow said, “Basically, what we found is, all you need to do is keep paint on your dock. You need to keep the water from touching the steel. You can use epoxy, but if you take your dock out every fall, you could probably use Rustoleum or something like that.”

Beyond docks, enzyme technology might also work on farm crops and in people. Elias said he is testing whether a lactonase enzyme spray can protect corn from a common bacterial infection (Gross’s wilt). Cystic fibrosis patients are prone to bacterial pneumonia, which forms in a biofilm.

Elias said, “One of our goals is to potentially use this enzyme as an aerosol to prevent biofilms in the lungs. . . It appears from our experiments that everywhere microbes are creating some sort of nuisance, this enzyme, because it changes the behavior of bacteria, can be helpful. We have a lot of different investigations to do and we are trying our best to pursue some of them as hard as we can.”

“This all grew out of those initial corrosion studies funded by Sea Grant and the work we did with Gene Clark and the other people in the corrosion study group,” Hicks said. Other organizations involved include the U.S. Army Corps of Engineers and the Great Lakes Maritime Research Institute.

*Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Minnesota Aquatic Invasive Species Research Center and the Legislative-Citizen Commission on Minnesota Resources.

The post Freshwater steel corrosion occurring beyond Lake Superior harbors first appeared on Wisconsin Sea Grant.

Original Article

News Releases – Wisconsin Sea Grant

News Releases – Wisconsin Sea Grant

https://www.seagrant.wisc.edu/news/freshwater-steel-corrosion-occurring-beyond-lake-superior-harbors/

Marie Zhuikov

Owners of steel structures on inland lakes and a river in northern Minnesota are reporting the same kind of corrosion as seen in the Duluth-Superior Harbor and other harbors along Lake Superior. A structural engineering firm reported it has designed and overseen replacement of gates on dams along the St. Louis River, far removed from Lake Superior water, because of the corrosion.

Along with partners, Gene Clark, retired Wisconsin Sea Grant coastal engineer, devoted considerable energy into ferreting out the causes of and ways to mitigate this corrosion, which can lead to costly harbor infrastructure replacement.

The accelerated corrosion of steel pilings in the Duluth-Superior Harbor was first noticed in 1998. Researchers funded in part by the Wisconsin and Minnesota Sea Grant programs eventually identified microbes as the culprit combined with a complicated interaction between water and the steel. Bacteria form small lumps, or tubercles, on the steel. The lumps limit oxygen and allow small amounts of copper in the water to interact with and dissolve the steel, which results in pockmarks and holes that compromise steel structures.

A steel research “coupon” removed from the Duluth Superior Harbor in 2007 shows freshwater biocorrosion tubercles. Image credit: Wisconsin Sea Grant

Experts brought together to investigate the issue blamed water chemistry specific to Lake Superior. However, those still tracking the issue have discovered this microbially influenced corrosion problem is more widespread.

Chad Scott, principal at AMI Consulting Engineers, initially alerted harbor industries about the corrosion issue in 1998 when he was a diver inspecting structures in the Duluth-Superior Harbor. Scott said during the past few years his company has worked with the U.S. Army Corps of Engineers to place steel samples (or coupons) in the St. Louis River at the Thompson Dam, Scanlon, Cloquet and near Cotton.

“At every single location along the river, the steel had the same tubercles on them,” Scott said. “So, what that tells me is, what’s coming to the harbor is coming down naturally from inland in Minnesota.”

Scott said his firm designed and oversaw replacement of gates on the Fond du Lac Dam and the Sappi Dam in Cloquet.

“They were all heavily pitted. It looked just like harbor corrosion,” Scott said. He’s also had friends report biocorrosion on their docks on Fish Lake, Island Lake and Grand Lake. He’s seen firsthand the dock posts covered by corrosive tubercles on those lakes.

A steel dock post on Wilson Lake near Cotton, shows the same biocorrosion tubercles as those found in the Duluth Superior Harbor. Image credit: Marie Zhuikov, Wisconsin Sea Grant

Randall Hicks, professor emeritus at the University of Minnesota Duluth, has worked for years to understand the microbiology behind the corrosion. He said he has seen the tubercles on his own dock on Barrs Lake near Two Harbors. He has also identified them in photos from a dock on Wilson Lake near Cotton.

“I don’t think it’s just a regional problem,” Hicks said. “I think it’s been happening all along for a long time in places where conditions are right.” Those conditions include the presence of sulfate-reducing bacteria and iron-oxidizing bacteria, a source of dissolved sulfate and iron, and low-oxygen conditions such as those sometimes found in spring water.

Hicks described how the process begins when a clean sheet of steel is placed in water. “Different bacteria will attach to the surface and form a biofilm first.” Dental plaque is a common example of a biofilm. Microorganisms multiply and create a thin but tight layer on teeth. In this case, the biofilm layer is on steel.

“As that biofilm grows, we see a lot of iron-oxidizing bacteria – they’re aerobic microorganisms,” Hicks said. He explained that as the iron-oxidizing bacteria next to the steel surface use up oxygen, sulfate-reducing bacteria, bacteria that can live without oxygen, become common. “It’s really their activities in combination with activities of the iron-oxidizers in the biofilm that accelerate the loss of steel from the surface of the metal.”

Jim Sharrow, retired director of planning and resiliency with the Duluth Seaway Port Authority, said the corrosion bacteria are not an invasive species. “They’re indigenous to this area. They’re all over.”

The Canadian Northern dock in the Duluth Superior Harbor shows damage caused by freshwater microbial corrosion in 2007. Image credit: Wisconsin Sea Grant

Previous research identified coatings that can be used to protect steel. Hicks is now working on ways to fool the bacteria in the first place. Hicks and Mikael Elias, associate professor from the University of Minnesota Twin Cities, have found that adding a lactonase enzyme into a steel coating can reduce the biofilm produced, change the biofilm community and reduce the amount of corrosion. The lactonase enzyme works by destroying signaling molecules that the bacteria on steel produce to sense each other – in essence, fooling the bacteria into thinking they are alone, so “they don’t turn on genes to produce a biofilm,” Hicks said.

The nontoxic coating enzymes only last a month or two before degrading or diffusing out of the coating but Hicks said that, compared to untreated steel, the enzymes have reduced corrosion by 50% for at least two years, which was the length of their study.

“Hopefully, these enzymes can have an impact even farther out. If you’re in the shipping business and you expect a steel structure to last 100 years, then all of a sudden you have to replace it every 50 years because of the corrosion, that’s a big economic impact – and that’s just with doubling the corrosion rate. If we can reduce the rate, we don’t need to have a big impact to really extend the lifetime of structures quite a ways down the road,” Hicks said.

The University of Minnesota has applied for a patent for the lactonase enzyme coating. Hicks and Elias have also conducted tests in Lake Minnetonka and the Mississippi River to see if the same mechanism in the enzymes that inhibits biofilms from forming on steel inhibits larger invasive and nuisance organisms like zebra mussels and barnacles from attaching to underwater structures.

Elias said their experiments, funded by the Minnesota Environment and Natural Resources Trust Fund*, were successful. More recently, they added sites in sea water. Their pilot experiments in Florida show promise.

Until the lactonase enzyme coating becomes commercially available, what should cabin dock owners do to protect their steel from biocorrosion? Sharrow said, “Basically, what we found is, all you need to do is keep paint on your dock. You need to keep the water from touching the steel. You can use epoxy, but if you take your dock out every fall, you could probably use Rustoleum or something like that.”

Beyond docks, enzyme technology might also work on farm crops and in people. Elias said he is testing whether a lactonase enzyme spray can protect corn from a common bacterial infection (Gross’s wilt). Cystic fibrosis patients are prone to bacterial pneumonia, which forms in a biofilm.

Elias said, “One of our goals is to potentially use this enzyme as an aerosol to prevent biofilms in the lungs. . . It appears from our experiments that everywhere microbes are creating some sort of nuisance, this enzyme, because it changes the behavior of bacteria, can be helpful. We have a lot of different investigations to do and we are trying our best to pursue some of them as hard as we can.”

“This all grew out of those initial corrosion studies funded by Sea Grant and the work we did with Gene Clark and the other people in the corrosion study group,” Hicks said. Other organizations involved include the U.S. Army Corps of Engineers and the Great Lakes Maritime Research Institute.

*Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Minnesota Aquatic Invasive Species Research Center and the Legislative-Citizen Commission on Minnesota Resources.

The post Freshwater steel corrosion occurring beyond Lake Superior harbors first appeared on Wisconsin Sea Grant.

Original Article

News Releases – Wisconsin Sea Grant

News Releases – Wisconsin Sea Grant

https://www.seagrant.wisc.edu/news/freshwater-steel-corrosion-occurring-beyond-lake-superior-harbors/

Marie Zhuikov