Lurking beneath Lake LaVerne

Feature article written for the Iowa State Daily and my in-depth reporting class. Online version can be found here.

Cyclone Aide Caroline Quinn could give campus tours in her sleep. Over the summer, she and other Cyclone Aides facilitate orientation and Destination Iowa State by giving tours, working with families of new or potential students and serving on information panels. This leaves for long and busy days in the summer, going from 7 a.m. to midnight, but Quinn doesn’t mind. She says she enjoys sharing her love for Iowa State.

Quinn, a junior in marketing, and her Cyclone Aide partner navigate families all over campus. When it’s time for lunch, they lead groups from the Memorial Union to the Union Drive Community Center. Their route of choice is to circle Lake LaVerne to show off an iconic scenic spot on Iowa State’s campus. Or at least what is supposed to be a scenic spot.

“We noticed [Lake LaVerne] really builds up with algae over the summer, it was really green and super gross,” Quinn says. “It just got worse and worse.”

Once, as Quinn led families out of the Memorial Union to Lake LaVerne, she overheard a voice saying, “Wow, that lake looks so ugly.”

With a film of green covering the lake, Lake LaVerne had seen better days. Quinn didn’t know what to say, in silent agreement with the voice.

The green algae covering the lake is not an uncommon occurrence for Lake LaVerne.

The lake’s depth, six feet at deepest, is shallow compared to other lakes. This allows sunlight to get through to the bottom of the lake, making for abundant algae growth. The algae are fed by the nutrients from animal waste, either by Lancelot and Elaine or other animals nearby, and the decaying algae itself.

This is why algae blooms are common for Lake LaVerne, especially in the summer. Algae are not usually attractive, as heard from Quinn’s tour group — they can have a strong odor and cover the water’s surface. While the filamentous (green) algae seen by Cyclone Aides and anyone on campus in the summer aren’t harmful, there are toxic types of algal blooms, such as blue-green algae (cyanobacteria) that potentially could appear.

Grace Wilkinson, assistant professor of ecology, evolution and organismal biology, said there is a possibility of blue-green algae in Lake LaVerne if nutrient levels, such as phosphorous, increase.

“Phosphorous is food for algae,” Wilkinson says. “That could result in larger, more frequent algal blooms.”

That’s why Facilities, Planning and Management (FPM) began to take proactive steps to clean up the lake.

The department has tried a variety of methods to lower the nitrogen and phosphorus levels and limit algae blooms. In the early 2000s, they developed a partnership with Iowa State’s Limnology Laboratory to improve the water quality of the lake. And so began the trials of Lake LaVerne.

At first, FPM tried dredging the lake without success. Dredging a lake involves physically removing sediments at the lake bottom either by sucking, digging or various other methods. FPM’s next step was to work with the Limnology Lab (limnology is the study of inland waters) to install aerators to keep oxygen levels high enough so sediments could go into the atmosphere and the water would have a slight current to keep the water moving.

FPM worked with John Downing, the director of the Limnology Lab at the time, who led investigations specifically looking at Lake LaVerne’s chlorophyll, nitrogen, phosphorous and secchi depth (transparency) levels.

Once analyzing all of these measurements, the limnology team was able to determine the trophic state index of the lake. A trophic state index is a classification system used to rate lakes’ amount of biomass and nutrients. The ratings range from one to 100 and are classified in one of four categories: oligotrophic, mesotrophic, eutrophic or hypereutrophic.

The trophic state index is a way of measuring how many nutrients are in a body of water, commonly a lake. The nutrients measured are usually nitrogen, phosphorus, secchi depth (transparency) and other biological nutrients.

  1. Oligotrophic: Low biological productivity, meaning low nutrient content. This means water has little algae and is very clear. 
  2. Mesotrophic: Intermediate biological productivity, meaning clear water with submerged plants.
  3. Eutrophic: High biological productivity, meaning the water supports many aquatic plants. Typically water body is dominated by plants or algae. There is a possibility of excessive algal blooms, which could result in fish death.
  4. Hypereutrophic: Very high biological productivity, usually with severe algal blooms and low transparency. Excessive algae lower the oxygen levels in water body, preventing life from functioning at lower levels. 

The limnology team came to the conclusion Lake LaVerne’s trophic state index was in the eutrophic state, meaning the lake has a high level of biological productivity. While a eutrophic state in itself isn’t inherently harmful, excessive algae can be harmful to organisms and it often leads to a less attractive environment.

Wilkinson researches nutrient inputs and outputs, algal blooms and ecosystem resilience. Her lab monitors more than 100 lakes and reservoirs in Iowa. She says a eutrophic state index indicates harmful algal blooms are likely, in addition to very low oxygen concentrations, which can cause issues for fish and other organisms. Eutrophic symptoms are typical for lakes across Iowa, Wilkinson said.

FPM came to the conclusion with the Limnology Lab that the best course of action for managing Lake LaVerne’s nutrient levels was to begin alum treatments in the lake. An alum treatment is the addition of aluminum sulfate to prevent phosphorus from leaving the sediments of the lake, essentially creating a temporary barrier just above the lake bottom. This treatment limits the amount of nutrients to help the algae to grow, decreasing the amount of algae.

From 2012 to 2015, alum treatments were conducted one or two times a year. Over the course of three years, Lake LaVerne increased its transparency by 25 percent and decreased phosphorus levels by 13 percent, according to calculations done by Downing and his team.

While the alum treatments produced good results in Lake LaVerne’s nutrient levels, it is only a temporary fix that needs to be followed up with more treatments.

“It’s a short-term solution because the lake is pretty shallow,” Downing says. “Any amount of turbulence kicks the sediments back up and allows the nutrients to come back into the water.”

Lake LaVerne has seen improvements since its lowest point a decade ago. With the alum treatments and overall monitoring of the lake, FPM and the Limnology Lab have kept Lake LaVerne’s nutrient levels consistent. At the end of the summer, when the lake is at its highest algae count, FPM initiates an alum treatment to clean up the excess nutrients.

Quinn said she remembers Lake LaVerne continuing to have more and more algae, and then one day the lake was clean, but she didn’t know what had happened.

Chris Strawhacker, one of Iowa State’s landscape architects, said FPM has made improvements in the lake’s water quality over the years and said while algae are the largest problem the lake faces, they are not too concerned with its affected water quality.

“We manage the lake primarily for the aquatic vegetation that’s in it,” Strawhacker says. “The water quality is pretty good. The issues that we deal with most are algae and other plant life in the lake.”

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