DAVENPORT -- The ancient city of Babylon had its hanging gardens; now Davenport has some that float at Eastern Avenue Park.

Thursday, a group coordinated by

launched five "floating islands" into the park's lagoon. Each of the mattress-sized platforms was covered with dozens of young plants and drifts of brown potting mixture.

The plants, all natives that thrive in wet conditions, are there to absorb excess nitrogen and phosphorous, said Laura Morris, program manager at River Action.

"The real goal is to get rid of blue-green algae," Ms. Morris said Thursday as people bustled around her before the launch, tucking plants into holes in the islands' surfaces and layering the potting soil over the top.

Blue-green algae appears naturally in anecosystem, but if too much nitrogen and phosphorous is present, there is a risk of the algae growing beyond the environment's ability to support it in that area.

Such an unbalanced arrangement can use upoxygen in the water and lead totoxic conditions that can cause illnesses in people and kill animals.

Critics blame Mississippi River pollution caused by nitrogen and phosphorous, which are used in agriculture production, for a "dead zone" in the Gulf of Mexico -- an oxygen-depleted area where little or no animal life can survive.

Ms. Morris said the lagoon has a history of problems with algae, and testing is planned to see how the islands affect water quality.

Other islands were scheduled to be placed in Credit Island lagoon later Thursday, and more installations were planned Friday at Nahant Marsh's Carp Lake.

The islands, made of recycled plastic, have a life span of up to 10 years, Ms. Morris said. As the plants grow, their roots will extend into the water below the island, and the plants will spread along the island's surface, filling in the spaces between planting holes.

The plants are perennials and will stay in place during the winter, Ms. Morris said. The islands will have to be monitored on occasion to replace plants that did not survive, and to remove invasive plant species.

The plants being used consist of grasses in the center of each island, and flowering plants along the edges, she said.

They will provide habitat and food for animals -- fish, insects and birds, she said. Until the plants are fully established, however, the islands will be netted to temporarily prevent birds from making use of them.

The islands are made by

, she said. They are a fairly new method of dealing with algae, but they have been used in other areas. They have been used at least once before in the Quad-Cities, and there are some in Bettendorf.

The project cost is about $60,000, and it is being funded by a Scott County Regional Authority grant, Ms. Morris said. Other entities that are taking part include Nahant and Davenport.

Ms. Morris said the islands also will serve as a tool for teaching people about pollution.

"It really opens the door for conversations in our area," she said.

More about Floating Island can be found atfloatingislandinternational.com.River Action's website is riveraction.org.

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Floating island will battle algae in Davenport park - Quad-Cities Online