The Ohio State University at Mansfield

Research from The Ohio State University at Mansfield will help make water safer for Ohioans

October 7, 2020

How safe the water some Ohioans drink or swim in may depend in the future, at least in part, on some unusual objects floating on the Milliron Research Wetlands of The Ohio State University at Mansfield.

The quiet setting behind Riedl Hall is where graduate student Zhaozhe Chen conducts the key research he needs as he works to add a master’s degree in earth science to his master’s in biochemistry. As Chen has learned, fundamental elements of research include the ability to be flexible and to expect unexpected things, and sometimes the unexpected happens before you even get started.

When concerns arising from the COVID-19 pandemic forced the Columbus resident to rethink his original plan to use Mirror Lake and Chadwick Arboretum on the Ohio State Columbus campus, Chen was grateful that Norman Jones, dean and director of Ohio State Mansfield, approved his use of the campus’ wetlands. The availability of the Milliron Research Wetlands at Ohio State Mansfield during the summer growing season became paramount for Chen’s research.

“It was very important,” said Ozeas S. Costa, Jr., associate professor of earth sciences and Chen’s thesis advisor. “If the dean did not allow us to use the wetland there, Chen would have lost a year, since the research can only be conducted during the growing season (from about April to September). That was one of the things we were afraid of, that he would not have a place to run his experiment, collect data and defend his thesis in the spring of 2021.”

The experiment, which uses three cells that each contain six artificial floating islands (AFIs), assesses the nutrient removal efficiency of these floating structures. Chen’s goal is to eventually implement the floating wetlands as a low-cost, environmentally friendly and effective remediation/prevention treatment for nutrient pollution in lakes, wetlands and streams in Ohio and elsewhere. Nutrient pollution in bodies of water is one of the most widespread and costly environmental problems in the United States and worldwide.

Funded by grants from the Ohio State Sustainability Institute and the School of Earth Sciences’ Friends of Orton Hall, the experiment set-up consists of three cells each containing six individual floating wetlands made of PVC tubing and anchored by rope and weights to the wetland bottom. In each cell, four of the six AFIs contain aquatic plant species (two of Carex comosa – the bristly sedge – and two of Eleocharis palustris – the common spike-rush). The remaining two AFIs in each cell contain no plants and serve as experimental controls. Plant shoots grow above the water while the plant roots are underwater.

Within weeks a bacterial film developed around plant roots and on the AFI structure. The tiny bacteria in this biofilm play an essential role in removing nutrients from the wetland. These bacteria use a number of chemical transformation processes to change the nutrients available in the water into a form that is easier to be removed. Essentially, the bacteria and the aquatic plant work together to clean the water and remove the harmful nutrient excess.

In conjunction with this natural experiment on the wetland, the researchers are running an outdoor experimental system containing small artificial floating islands in controlled conditions to determine how much of the nutrient-removal is being done specifically by the artificial floating islands.

The research uses a concept that is about 40 years old and popular in Asia and adapts it to the conditions and species found in Ohio’s wetlands, Costa said.

“Chen noticed that a lot of the work in the scientific literature is based on plants that are not common in North America,” Costa said. “His idea was, what if we could modify those ideas and adapt them to plants that are native to Ohio and see if they do well.”

Carex comosa and Eleocharis palustris are both sedges (grasslike plants growing in wet conditions) common to Ohio and the Midwest, Costa added.

The research includes weekly sampling of plant biomass in the controlled tanks and in the wetland. The plan is to continue the experiment through the fall to account for changing temperatures and other environmental conditions.

Costa said because Ohio State’s labs had been closed until recently, he can only speculate on the experiment’s results, but the visual observation is promising.

“Again, it is just speculation and we have to look and see if the data is going to back it up, but just from my experience doing this for almost 20 years now it seems to me those floating wetlands are doing an extremely good job, he said.

Chen expressed hope that his findings will help create a healthier world for everyone, especially for using Lake Erie.

“Lake Erie is one of the most nutrient-rich lakes in the world,” he said, referring also to Maumee and Sandusky bays,” Chen said. “The public swims and fish in those water systems and that is not good for them, so dealing with this nutrient pollution problem should be a very important, very valuable thing to do, especially if we can find both an efficient and environmentally friendly way to do that.”

Costa and Chen welcome undergraduate students who would like to assist. Students can receive college credits or financial compensation by helping with the research.

“I need to spend more than 12 hours every Wednesday or Thursday to do the sampling,” said Chen, who drives from Columbus once a week to conduct his research. “I would be glad to have a student’s help doing the work.”

Costa asked that those interested email him at

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