Just when you thought it was safe to go back in the water, it may soon be time to bale. Pun intended.
With this week’s oppressive heat wave cranking up water temperatures across the state, the annual battle between pond and lake managers and the scourge of blue-green algae is right on our doorstep.
After seeing an earlier-than-normal outbreak of blue-green algae in April at Lake Shawnee, three Shawnee County waterways are now taking part in an experimental pilot program attempting to allay the threat of future blue-green algae outbreaks this summer.
The county in May placed bales of barley straw at Lake Shawnee, Central Park Pond and the Doran Rock Garden Pond as part of a Kansas Department of Health and Environment study.
According to research from Rutgers University’s New Jersey Agriculture Experiment Station, barley straw has shown to help prevent blue-green algae blooms, although it does not kill existing algae.
“KDHE told us at the beginning of last year that the conditions, hot weather and lots of rain creating shallow areas around the edge of the lake (and our other ponds) was going to make it a banner year for blue-green algae,” said Mike McLaughlin, communications and public information supervisor for Shawnee County Parks and Recreation.
Thankfully, the KDHE warning announced in April has since lifted, at least for now.
“Blue-green algae is always present in a body of water, as are other types of algae,” McLaughlin said. “What causes blue-green algae to bloom and rise to the surface is an infusion of nutrients — primarily nitrogen and phosphorous. Substances that contain these nutrients include fertilizer, goose droppings and other animal droppings. Runoff from a neighborhood across from Lake Shawnee drains into the lake and would have introduced fertilizer into the lake this spring.
“The type of blue-green algae we had was an earlier blooming variety than what we normally see during hot weather.”
Use of herbicide
A theoretical cause of blue-green algae blooms that has been noted in other bodies of water is the use of herbicides, such as Roundup, to control aquatic vegetation, combined with runoff from lawns and farms, contributing to higher nutrient counts in the water.
Steve Quinn, who now resides in central Minnesota, worked as a fisheries biologist in Georgia for five years and has served as an editor for In-Fisherman Magazine for more than 30 years. During his time with the Georgia DNR, Quinn said he was was actively involved in plant assessment and advising landowners on the management of their ponds, including vegetation.
“When herbicides are applied and then the macrophytes knocked back, it frees so much phosphorus in the system, and it’s usually done in a time when warming water and sunlight foster really fast growth of some kind of aquatic plant organism,” Quinn said. “What often takes hold is green or blue-green algae — sometimes both — that form really rapidly.”
Quinn said the green algae typically goes away as the waters heat up, while blue-green algae seems to thrive in the higher temperatures and in eutrophic situations — where septic systems and farming practices can continually feed the algae.
He said herbicides are often used by lake managers to control aquatic vegetation, even before that sort of regulation becomes necessary.
“In a lot of the waterways, to my way of thinking, it doesn’t get to what you would call a real nuisance level until aerial coverage of the natural lake or impoundment exceeds 30 percent,” Quinn said. “Relatively few waters that aren’t highly eutrophic, swampy things anyway have that predominance of shallow water. It usually grows in water that’s under 12 feet deep, often less if it’s a little bit turbid.”
He said in many cases, work done to reduce vegetation on a lake may not yet be needed, but is done for aesthetic reasons.
“Some people love to get a pristine lake, the anglers are on the opposite end of the spectrum,” Quinn said. “And reservoir managers are sometimes caught in between or sometimes they foster removal of it just for tradition.
“The companies that sell the herbicides, of course, are very aggressive in their marketing campaigns and go to lake associations, community recreation groups and so on saying your lake is dirty or polluted if it has a lot of vegetation in it, which of course isn’t true.”
Lake Shawnee’s cause
One such waterway that chemically treats for aquatic vegetation is Lake Shawnee, which was treated in March with Sonar Genesis, a brand of fluridone-based aquatic herbicide used to help control Eurasian watermilfoil, an invasive species.
Despite the tendency of some herbicides to introduce algae-feeding nutrients like phosphorus into waterways, however, McLaughlin said that was quickly ruled out as a major factor in the lake’s early algae bloom. He noted a lack of phosphorus in the herbicide’s chemical makeup.
“We worked with KDHE and KDWPT to try and determine a cause for the early bloom this year,” McLaughlin said. “The Eurasian watermilfoil treatment was one of the first things that was ruled out. While an exact cause was not pinpointed, the most plausible theory was that water levels were so high with all of the rain we had last year, the water around Lake Shawnee rose up into areas that normally serve as riparian borders — tall grass that catches and traps the nutrients so they don't enter the lake. If the water went up into these areas last year, it could have pulled those nutrients into the lake when it receded.”
Among the potential causes of blue-green algae, Princeton Hydro lists climate change, discharges from wastewater treatment plants, runoff from agricultural operations, excessive fertilizer use in urban/suburban areas and stormwater runoff as possible contributors to cyanobacteria.
McLaughlin said it was up to communities to consider how development and the design of drainage systems impact both water flow and water quality on a larger scale.
“As the Shunganunga Creek had a washout that undermined the Shunga Trail at Crestview Park, we talked about how development to the west has affected that creek and Indian Creek, which runs through Shawnee North Community Park,” McLaughlin said. “Property owners upstream from the park have had issues during heavy rains. More development means more roads, more parking lots and more sidewalks, all of which create more runoff into waterways.
“High water volumes during spring rains erode creek banks. As communities, we don’t tend to think about this unless we happen to own property alongside a creek or use a trail that gets undermined.”
Both McLaughling and Quinn agreed that finding and limiting the excess nutrients being introduced into the water at their source was key to controlling the algal blooms.
“Try to define where its food is coming from, and then try to gradually reduce and cut that way back,” Quinn said.