WORTHINGTON — Students in Jeff Roger’s Introduction to Soils class at Minnesota West Community and Technical College were supposed to launch four new floating islands on the E.O. Olson regional stormwater pond on the Worthington campus Tuesday morning, but Mother Nature was spitting snowflakes and raindrops, keeping the students inside the greenhouse.
The new islands will be added to four floating islands placed on the pond a year ago as an experiment of the Okabena-Ocheda Watershed District (OOWD). Made of recycled pop bottles and milk jugs, the plastic mesh islands were developed by Minnesota-based Midwest Floating Island LLC. Each 8-inch-thick, 50-square-foot Biohaven is a base for grasses, sedges and flowers that feed off of nutrients in the water.
When the watershed district ordered the four new islands, it wasn’t yet sure how the one-year-old islands fared during the winter months.
“We didn’t know how the plants were going to overwinter,” said OOWD Administrator Dan Livdahl, who led Tuesday’s classroom project. “From a distance, they appeared to green up really well.”
While the goal of the islands is to ultimately improve water quality, the manufacturer recommends 10 percent coverage to see noticeable improvement. The eight floating islands on the E.O. Olson pond will account for just 1 percent coverage.
Still, Livdahl said the plant-covered islands are removing nutrients even at 1 percent coverage. One square foot of the Biohaven material is, if well maintained, the equivalent of 18 square feet of natural wetland.
Brenton Richters, an ag production major from Luverne, said having the floating islands on the stormwater pond to soak up the nutrients will hopefully lead to a reduction in algal growth.
“We need healthy water for the plants and the animals that live with it,” he said.
“As the plants grow, the roots are going to go through the pad and that creates a film,” explained Christine Kazemba, a general studies student considering a major in either agriculture or art.
“The film is kind of used for fish food,” added Amanda Cook, who is considering a major in agri-science.
The same plants that produce root systems to provide habitat and a food source for fish create above-water seeds and flowers to attract insects and birds.
The students spent their class time Tuesday filling each of the holes in the Biohaven with rockwool, a horticultural product used to wick up water and promote plant growth. Then, peat moss was scattered over the islands along with a variety of locally grown grass and flower seeds. Coconut fiber erosion control mats were placed on top and wrapped around the sides of the Biohavens to prevent degradation of the floating islands.
Native flowers and grasses, currently growing in 2-inch pots, will be placed in each hole prior to the islands being launched.
Livdahl said his greatest concern with the islands is the long-term survival of the plants. Last year’s islands needed to be weighted down with rocks to sink them far enough into the water to reach the plants.
“As we put in these new islands, we don’t know if one plant is doing better than the next,” he said.
Watching the islands last summer, however, Livdahl said it appeared the swamp milkweed, black-eyed susans and four different types of sedges did well. He’s ordered those same plants for the new floating islands.
All of the grasses and forbs planted on the islands are locally grown perennials that do well in wet conditions, he added.
The cost of the four islands was divided between the OOWD and the Lake Okabena Improvement Association.
Daily Globe Reporter Julie Buntjer may be reached at 376-7330.