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Could floating islands mitigate toxic algae blooms?

With bodies of waters suffering from toxic algae blooms, an idea struck Associate Professor of Landscape Architecture Jake Boswell to create a better type of floating wetland.

“The primary goal was to invent a floating island that could be more durable and made of material that is both cheap and non-toxic while not having adverse water effects,” Boswell said.

research team with floating islands at lake(l to r) Jake Boswell, Asst. Prof. Rachel Gabor, CEGE students Ben Luce and Simon PusateriThe islands will provide the body of water with wetland services to enhance wildlife diversity and to mitigate algae problems, which in the end will result in benefits such as improved drinking water resources, increased tourism and overall better water quality.

Toxic algae blooms thrive due to high levels of nitrogen and phosphorus. The plants in the floating islands need nitrogen and phosphorus to grow, and as they grow they will hopefully pull these excess nutrients out of the water.

“Without these nutrients in the water, we shouldn’t get the same degree of algae blooms,” Boswell said.

Boswell and his research team installed 13 small islands and will be installing a larger 6-foot version in Chadwick Lake to measure durability and public awareness.

In addition, at the Wilma H. Schiermeier Olentangy River Wetland Research Park, they installed nine islands in a mesocosms, which are smaller, more controlled environment for research. The islands in the mesocosms will allow the researchers to test water quality and monitor the plant intake of phosphorus and nitrogen. Rachel Gabor, assistant professor of watershed hydrology in the School of Environment and Natural Resources, leads the water quality testing.

The foundation of the islands are made from portland cement and two types of expanded glass. The expanded glass has air within it and strong compressive strength, which allows for a light, floatable vessel.

The plants within the vessels range from low-growing sedge and taller iris to trailing vine like water willow and upright sweet grass to allow for observations of how different plants react in certain conditions.

These species are planted in coconut coir, a nonsoil planting medium made of ground coconut husks, chosen because it is lightweight and has a neutral pH.

floating islands close-up“What we have learned so far, at least with the coconut coir, is we need to establish the plants dry before we put them in the water,” said Boswell.

Boswell and his team will watch to see how these concrete vessels weather through storms, wind and the winter months. These islands need to be durable and last in varying types of bodies of water, including those that may have ice.

One challenge for the project: geese.

“We have to figure out a way to keep the geese off the islands until the plants establish themselves,” Boswell says.

Over time, the researchers also will determine the impact of the fish and bugs that interact with the islands, added Lulu Aguiar, a graduate student in landscape architecture. Other team members include: Assistant Professors Lisa Burris, Rachel Gabor, and Nan Hu; civil engineering students Ben Luce, Simon Pusateri, Anthony Wong and Ning Cai; landscape architecture graduate students Isabel Stonehouse and Brendan Ayer; engineering graduate students Amal Jerald Joseph Maria Joseph, Shawn Sutton and Chunping Ma; and recent graduates Andrew Davis, Marty Koelsch and Megan Skibinski.

If the islands survive the winter, they will remain in place for one to two years. Having them in the water for an extended period of time allows researchers to monitor progress such as durability. The vessels become heavier as plants grow and the soil accumulates, Boswell said.

Currently, Boswell maintains a provisional patent on the vessel technology.

“The patent has made it through stage two and has been published by the U.S. Patent and Trademark Office,” Boswell said. He expects the patent will reach final approval within the next six months to two years.

“This isn’t my usual type of work, but this has been a super fun project to work on.”

Phase three of this project includes publishing the research findings and finding an interested manufacturer. Watersheds in Ohio could begin benefitting from the islands within three to four years as long as the research goes as planned.

Boswell received a $15,000 grant from the Ohio State Sustainability Fund for this research, which also was supported by the former Sustainable and Resilient Economy Discovery Theme (since merged with the Office of Energy and Environment to form the Sustainability Institute), Knowlton School of Architecture, Technology Commercialization Office, College of Engineering and Chadwick Arboretum.

by Meredith Oglesby for the Sustainability Institute at Ohio State.