Fertilizer runoff most likely caused algae blooms
Think of your plants. What does it take to make them grow? Sun, water, fertilizer — all components that make seeds sprout and buds blossom.
Then think of anabaena. It's just like a plant, requiring the right amount of sunlight and nutrients to grow.
Humans can't control how much the sun shines, but they can control how much fertilizer reaches a plant.
And excess fertilizer is probably to blame for making the anabaena algae bloom at Marion Reservoir, according to Kansas scientists.
At Kansas State University in Manhattan, Dr. Walter Dodds is a biology professor specializing in aquatic ecology and algae, among other areas.
According to Dodds, anabaena is a cyanobacteria. It's an ancient bacteria; some of the oldest known fossils to man resemble its structure.
Cause of blooms Like a plant, anabaena grows through photosynthesis — meaning it needs sunlight to live. It thrives in high-nutrient environments, places with lots of nitrogen and phosphorous. When those nutrients hit the anabaena, that causes the bacteria to "bloom" — bacteria that was already there in the first place.
"It's everywhere — the conditions need to be right," he said.
The nutrients cause the amount of algae to "explode," said Dr. Max Terman, biology professor at Tabor College. Since it's been in competition with other algae, the explosion of growth allow it to take over. Normally the anabaena is dormant until the favorable conditions — sunlight, nutrients, calm water — arrive. Then it's alive again. Since anabaena is already in the water, it's simply trying to gain dominance over the other algae. When the wind is calm it will float to the top and take over, Dodds said.
There are two main sources of the nutrients that cause anabaena to bloom. First, and most common, is the "runoff" from nutrients, or fertilizer, applied to cropland.
When farmers add fertilizer to their crops and it rains, the nutrients slide down the watershed and into the body of water. The fertilizer then effectively "fertilizes" the anabaena, causing it to grow.
"They act just like a plant," Dodds said.
Another possible source is runoff from a sewage plant, he said. Phosphorous and nitrogen are both used in sewage processes.
Watershed is source
In any scenario, the source of the nutrients is always located within the watershed that drains into the body of water.
The nutrients travel to the lake on soil that originated within its watershed, Terman said. Nitrates and phosphates can travel to the water from miles away, just as long as they're within that watershed.
"The ultimate solution is to protect the watershed," he said.
The watershed that drains into Marion Reservoir covers a 200-square-mile area northwest of the lake, according to Gary Schuler, director of the Marion County Conservation District.
Ninety percent of that watershed is located within Marion County, he said. It blankets the City of Durham.
The other ten percent of the watershed is in McPherson County.
One of the conservation district's tasks is to aid county farmers in limiting the nutrient runoff from their lands.
Any phosphorous that reaches the lake travels with soil, Schuler said. The conservation district works with area farmers to help stop that soil erosion.
When the soil washes off a farmer's field, it has to go somewhere, he said. Different methods such as terracing the land, seeding grass, constructing waterways, or using no-till methods can slow down that erosion.
Possible solutions
How do you rid a lake of anabaena? The options are limited.
In the past, copper has been used to try to eliminate the threat. But the copper is quite expensive and eventually loses its effectiveness, Dodds said.
Put in too much copper and the lake becomes contaminated with heavy metals, which can force the Environmental Protection Agency to come in and close the lake.
Besides the copper method, there aren't really any other good methods, he said. The best method is eliminating the cause of the blooms: the excess nutrients.
"If they don't add the fertilizers then (the algae) don't grow," Dodds said. Eventually the algae would go away on its own.
Terman agrees. The real solution, he said, is to prevent the nitrates and phosphates from getting into the watershed in the first place.
Meanwhile, county personnel are considering methods that would kill the algae in the lake.
The U.S. Army Corps of Engineers is looking into an "algicide," or chemical that would eliminate the algae. One of those algicides is called "cutrine," and it's a copper compound, according to Terry Holt of the Army Corps. Another alternative Holt looked into was a non-copper chemical called "hydrothol 191." This solution is manufactured by Cerexagri, a Pennsylvania company that produces agriculture chemicals.
Holt talked to a vendor that sells hydrothol 191. He learned that the chemical will kill algae as well as other plant life, but it's more environmentally friendly than copper and doesn't leave behind metals after the treatment. If Corps engineers used hydrothol to treat the lake, the body of water couldn't be used for seven days, Holt said. Though a swimmer who might accidentally go into the water "wouldn't be a problem," the algae would release their toxins as they died.
On the treatment end of the water plant, an activated carbon filter can be installed to filter out any organic matter, including algae, Dodds said. But it would have to be changed quite often.
