Cyanobacteria expert: Certain measures will help “clean the green” from Tainter Lake
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By LeAnn R. Ralph
MENOMONIE — A UW-Stout professor who is an expert in the toxicology of cyanobacteria says several measures can be taken by the Tainter Lake Rehabilitation District to “clean the green” from Tainter Lake.
Calling the green that occurs every summer in Tainter Lake “algae” is not accurate, because the green is actually the result of photosynthetic bacteria or cyanobacteria, said Dr. Scott McGovern, a biology professor at UW-Stout, as part of his presentation to the Tainter Lake Rehabilitation District Board of Commissioners at the January 18 meeting.
Also known as “blue-green algae,” cyanobacteria can produce toxins that can make animals and people ill.
Cyanobacteria is fueled by phosphate and nitrate, and there is plenty of both in Tainter Lake, Dr. McGovern said.
The cyanobacteria needs sunshine for photosynthesis, so when the water temperature rises into the 60-degree Fahrenheit range, then the colonies of cyanobacteria start growing, he said.
Lake balancing, also known as trophic cascade or biomanipulation, was first described by Joseph Shapiro in 1975, but existed before 1975, Dr. McGovern said, noting that Stephen Carpenter described it as trophic cascade.
The method, which encourages organisms to flourish that consume cyanobacteria, has been used for about 60 years “with plenty of good successes,” he said.
Water fleas, which are microscopic crustaceans, also known as zooplankton, feed on cyanobacteria and keep it in check, Dr. McGovern said.
There are other zooplankton in addition to water fleas that feed on cyanobacteria, he said.
The problem with cyanobacteria getting out of hand is when there are millions of fish hatchlings — minnows — in the spring that eat the zooplankton so that the cyanobacteria has an opportunity to get out of hand, Dr. McGovern said.
When the crustaceans are depleted and are not consuming cyanobacteria, “the green multiples,” he said.
Predation
Reducing the minnows that feed on the zooplankton will help reduce the green in the lake, Dr. McGovern said.
Larger fish eat minnows, so promoting predator fish, such as musky, walleyed pike, northern pike, small mouth bass and large mouth bass, will help control the minnows produced by rough fish, he said.
Rough fish include common carp, white suckers, redhorse suckers and dog fish, Dr. McGovern noted.
Reducing the minnows of rough fish will reduce predation on the zooplankton which will in turn reduce the cyanobacteria that causes the lake to turn green in the summer, he said.
Increasing desirable plants in the lake will give the zooplankton somewhere to hide, as well, to get away from the minnows that prey on them. Refuges for zooplankton can also be built, using things like Christmas trees that have been wrapped in screen so the crustaceans/zooplankton can have somewhere to hide, Dr. McGovern said.
Daphnia, copepods, seed shrimp and native mussels (clams) help make the water clearer, he said.
Some people raise those organisms that eat cyanobacteria and then release them in an area that is particularly prone to cyanobacteria blooms in the summer, which increases the amount of zooplankton available to clean up the water, Dr. McGovern said.
Removing rough fish
There have been projects to remove rough fish from Tainter Lake in the past, but the last large effort was in 1986 to remove carp, redhorse and white suckers, Dr. McGovern said.
A chart that was used as part of the presentation showed that in 1952, a total of 110,000 pounds of common carp were removed from Tainter Lake — that is 55 tons of carp — or the equivalent of nearly 75 three-quarter ton pickup loads of carp.
In 1986, a total of 7,910 pounds of carp were removed Tainter Lake, while in 1981, there were 16,592 pounds of carp removed, and in 1980, there were 17,000 pounds of carp removed.
Other rough fish were removed from the lake as well although in much smaller quantities.
The rough fish that were removed from Tainter Lake were seine netted, Dr. McGovern noted.
The Tainter Lake Rehabilitation District Board of Commissioners could have a commercial fishing operation come in to seine for rough fish, he said.
The Board of Commissioners could also hold a fishing contest and offer prizes to those who catch the largest amount of rough fish, Dr. McGovern said.
Repopulation
The Red Cedar River and the Hay River, which both flow into Tainter Lake, will repopulate the lake with rough fish, Dr. McGovern said.
There are probably a few readers who remember going fishing in the river for suckers in the spring — or maybe even still do that kind of fishing as adults. While suckers do have a lot of bones, they make good pickled fish.
A river barrier, which uses a compressor and a pipe across the river channels to create a wall of bubbles, will keep fish in the river rather than the rough fish crossing into the lake, Dr. McGovern said.
During a a certain time of year, rough fish will migrate with the river, he said.
Plants
Plants will compete with cyanobacteria for nutrients, Dr. McGovern said.
The professor showed a photo of an experiment he had done with a turbidity curtain and certain plants, such as water lilies and cattails, growing inside the enclosure.
The water inside the enclosure was cleaner and clearer than the water outside of the enclosure that was filled with the blue-green of cyanobacteria.
The plants help stabilize the sediment, use nutrients that fuel the cyanobacteria, provide a habitat for zooplankton and also produce a chemical that inhibits the growth of cyanobacteria, Dr. McGovern said.
Many years ago, the reporter for the Colfax Messenger and the Tribune Press Reporter rented a house on Whitewater Lake in southern Wisconsin.
Whitewater Lake suffered from persistent blooms of cyanobacteria in the summer that created such a stench, the windows had to remain closed for a certain part of the summer.
The Messenger-Tribune reporter at the time worked as the Whitewater correspondent for the Janesville Gazette, and one of her assignments was to interview a UW-Whitewater biology professor about the blue-green cyanobacteria.
The professor said more plants in the lake would help clear up the water.
A year or two later, Whitewater Lake was filled with invasive eurasian milfoil — and miraculously, the lake turned crystal clear with no more cyanobacteria blooms.
Equipment to harvest the milfoil was then used to reduce the amount of milfoil in the lake, and while invasive milfoil is not a desirable solution by any means, the plants did illustrate Dr. McGovern’s point about plants helping to clear up the water.
As an added benefit, bass returned to the end of the lake where the Messenger-Tribune reporter lived, as did Great Blue Herons, and otters who liked to slide down the bank and swim in the lake.
Alum
Alum (aluminum potassium sulfate) — which is used in the process of making pickles to keep them crispy — attaches to the phosphate and precipitates it to the bottom of the lake, Dr. McGovern said.
There also is phosphate on the cyanobacteria, so alum binds to it and also precipitates the cyanobacteria, he said.
When the alum has sunk to the bottom of the lake, it creates a protective layer on the bottom that prevents the phosphate from the sediment entering into the water column, Dr. McGovern said.
Alum can be used in combination with lake balancing (encouraging sport fish and discouraging rough fish so the zooplankton can control the cyanobacteria), he said, noting that alum has been used in lakes for a while and is not harmful.
Dyes
Dyes can also be used to control the blue-green cyanobacteria, Dr. McGovern said.
Even with dye in the water, the lake could used for swimming and fishing, he said.
The dye blocks out the sunlight so the cyanobacteria cannot grow, Dr. McGovern explained.
The dye method costs $150 to $300 per acre, he noted.
Tainter Lake is 1,692 acres, so treating the entire lake with dye would cost $250,000 to $500,000.
The Board of Commissioners could start out with a small experiment to treat areas that are particularly bad for developing cyanobacteria blooms to see how well the dye works, Dr. McGovern said.
Flowages
Grant Peissig, a member of the Board of Commissioners, asked if other lakes that had successfully used lake balancing and other methods were flowages, like Tainter Lake.
Yes, lake balancing is very effective for flowages, Dr. McGovern said.
One lake in Sweden is 2,700 acres and has five rivers feeding into it and one river exiting the lake, and lake balancing has worked well, he said.
Silver Lake in Minnesota, and a 13,000 acre lake in St. Marys, Ohio, also have benefitted from lake balancing, Dr. McGovern said.
Lake balancing is a “cheap” method for helping to prevent cyanobacteria, he said.
Scientists like to use a variety of methods to keep the green out of lakes. The Tainter Lake Rehabilitation District could hire some of it done and could do some of the work themselves, Dr. McGovern said.
Why?
Jim Zons, Dunn County Board supervisor from Colfax, and the county board’s representative on the Board of Commissioners, asked if Dr. McGovern knew why the harvesting of rough fish from Tainter Lake had stopped 40 years ago in 1986.
There appeared to be a misunderstanding or a disagreement between the company harvesting the fish and those paying for it, Dr. McGovern said, adding that in 1986, he did not live in this area and could only go by what he had been told by others.
The people harvesting the fish were being paid for it, but they also sold the fish for a market purpose, he said.
Zons said he had been told that the people paying for the harvesting of rough fish instead wanted to be paid for the rough fish, and the people harvesting the rough fish said they would go to other lakes “where they will be happy to have us.”
The state has a list of rough fish in Wisconsin Act 180 [2011], the professor said.
Act 180 lists rough fish as suckers, carp, asian carp, goldfish, freshwater drum, burbot, bowfin [also known as dogfish], garfish, sea lamprey, alewife, gizzard shad, rainbow smelt and mooneye.
There is no bag limit on rough fish, and there is no closed season. Rough fish can be fished by line, seine net, bow and arrow and crossbow, Dr. McGovern said.
Goal
Peissig asked what would be a good goal for removing rough fish from Tainter Lake.
A goal of 50,000 pounds would be a great start, Dr. McGovern said.
A fish population study to know what kind of rough fish are in Tainter Lake and how many would be the way to start to target rough fish, he said.
Using a bubble barrier to keep rough fish out of the lake would require electricity to the site as well as a compressor and an enclosure for the compressor, Dr. McGovern said.
Walleyed pike spawn in the Russian Slough, so a bubble barrier would have to be placed beyond where the walleyes spawn so they are not disturbed, he said.
Stocking the lake with predator fish (musky, walleye, bass and northerns), removing rough fish, and adding zooplankton and habitat for zooplankton will all help to clean the water and reduce the green, Dr. McGovern said.
One member of the Board of Commissioners noted that the Lake District has four ad hoc committees now and wondered where would be a good place to start.
Trying to solve problems, such as sedimentation of the lake, can come later. Reducing the green should be the first priority because it is a health concern, Dr. McGovern said.
Millions
Pete Heimdahl, a member of the Board of Commissioners, asked for more information on the zooplankton that eat the cyanobacteria and the hatchlings that eat the zooplankton.
Rough fish multiply fast, Dr. McGovern said.
A 10-pound carp can lay a half million eggs, and 50 to 90 percent of those eggs hatch, In two weeks, they can deplete the zooplankton in the lake, he said.
Considering the 110,000 pounds of carp harvested from Tainter Lake in 1952, if half of them were 10-pound females, that would be 5,500 carp spawning, resulting in about 2.8 billion eggs, and if half of them hatched out and started munching on zooplankton, that would be 1.4 billion carp hatchlings looking for food.
If the hatchlings are eating the zooplankton, what is the best time of the year to stock the lake with zooplankton? Heimdahl asked.
Removing the rough fish and stocking with zooplankton would help to reduce the green, Dr. McGovern said.
The zooplankton could be stocked early in the spring, giving them more time to consume the cyanobacteria, he said, noting that adding plants to the lake would help, too.
Heimdahl asked about commercial sources for zooplankton.
The Tainter Lake Rehabilitation District could raise the zooplankton themselves. Commercial sources are available for laboratories, so the lake district could buy a small amount of zooplankton and raise them in 55 gallon drums. Zooplankton multiply quickly, so a 55 gallon drum would supply a large amount of zooplankton, Dr. McGovern said.
Along with stocking zooplankton, the lake district could provide artificial habitat for the zooplankton and create a refuge to help them stay away from the hatchlings, he said.
The lake district could also provide some incentives for people to capture the hatchlings to use or to sell as bait, Dr. McGovern said.
