[USA] As summer wears on, some lakes, ponds and coves will become a green, goopy mess as microscopic algae blooms go into overdrive.
Algal blooms are not only ugly, but the overabundance of plants soon dies. As they decay, they use up the oxygen in the water, causing fish and other wildlife kills.
These eyesores are caused in part because of excess lawn fertilizer that rainwater carries into waterways. Fertilizer, including goose and dog poop, is a culprit because it nourishes the algae to grow very fast.
Now, neighborhoods and residents, tired of ponds turning a sickly green in summer, can fight back.
Whether called floating treatment wetlands, floating wetland islands or just floating islands, these manmade island rafts help combat pollution, such as fertilizer runoff, the way natural wetlands do.
The floating structures can be made with any buoyant material, such as PVC pipe. For example, the pipe would support a planting base, perhaps coconut fiber over chicken wire that would hold the plants in place. Once the base is planted with wetland plants, the raft is anchored in the water. Then the plant roots grow down into the water and begin absorbing pollution as natural wetlands might do.
Commercial floating island manufacturers, as well as different do-it-yourself plans for the islands, can be found on the Internet, along with lots of photos and information.
A few groups in Hampton Roads have been experimenting with these islands. Laurie Fox, horticulture associate at Virginia Tech’s Hampton Roads Agricultural Research and Extension Center on Diamond Springs Road in Virginia Beach, has been overseeing research on two floating islands in the center’s pond.
Jody Ullmann is Pearl School/education coordinator at Lynnhaven River Now in Virginia Beach. She has been overseeing a Lynnhaven River Now program called Growing Wetlands in the Classroom in which elementary students grow wetlands plants for use in river restoration projects.
This spring, Ullmann has used some of the wetlands plants in floating island projects that she has helped facilitate at some local high schools. A group of bioengineering students at Landstown High School have not only studied floating wetlands, but they also have designed, built, planted and launched some islands.
Floating wetlands might be appropriate tools to use in neighborhood ponds or large backyard ponds or coves around the area that are susceptible to algal blooms, Ullmann said.
“Water holes on golf courses,” she added, “and almost every condo has a stormwater management pond.”
The islands can be almost any size or shape, from around 2-by-2-feet to 6-by-6-feet or more. They can be planted with just about any plant that likes water, such as rushes and other small grasses and bloomers, such as pickerelweed and blue flag iris, “the kinds of plants that would be good in a rain garden, minus woody shrubs and trees,” noted Fox.
Islands are often fenced in at first to keep geese from dining on the tender young plants. As time goes on, the fencing can come down, and the islands turn into a pretty green floating mass, sometimes with flowers. Some islands are built to stay out year-round. Others are pulled in for the winter, replanted and anchored out again in spring.
Fish begin to use the plant roots for cover, noted Ullmann. Other animals, such as turtles, frogs, ducks, herons and egrets, have shown up at the research center islands, said Fox, “animals that you would expect to see in a healthy ecosystem.”
The research station islands have been doing their part to keep the station’s stormwater/irrigation ponds clean for three years now, Fox said. You can visit the pond at the research station any time during daylight hours. Follow the Buffer Garden signs to the pond. Fox said the islands work best in conjunction with other stormwater management tools, such as buffers and rain gardens that can help to capture runoff, too.
You also can visit some of the ponds that Virginia Beach students have worked on with Ullmann’s help. The Landstown bioengineering students’ islands can be seen in the school’s retention pond on Concert Drive.
Students at Bayside High School planted and launched two manufactured islands, called BioHaven mats, at the Hampton Roads Sanitation District Chesapeake/Elizabeth plant on Shore Drive. Students from five elementary schools grew the soft rush grasses that were planted in the islands.
All eyes will be on the islands for several years to see how well they work over time. Does the construction method affect the way the islands hold up? Has the water quality improved? Are the plants healthy?
And, did that pesky algae bloom again?
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