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Spotlight - Floating Wetlands Installed At Mt. Pisgah State Park
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Visitors to Mt. Pisgah State Park with a keen eye for lake scenery may have noticed a subtle change in lakeside topography—two mini-land masses sprouting virtually, and literally, overnight. On May 11, two floating wetland islands were installed in the Bradford County park’s S.F. Foster Lake. Measuring 15 by 12 feet, the artificial islands are designed as a best management practice to reduce nutrients in the lake, which receives inputs from Mill Creek, an 11-square-mile, mainly agricultural watershed.
The 75-acre lake has been on the Department of Environmental Protection’s List of Impaired Waters since 1996, and over the past 13 years, about $1.5M of watershed BMPs were installed to mitigate nutrient and sediment runoff. Projects included stream-bank stabilization, manure storage, barnyard runoff, exclusion fencing and native riparian plantings.
To further reduce availability of nutrients that drive algal blooms, the lake now is the focus of in-lake BMPs that include on-going aquatic plant harvesting, an alum treatment and, most recently, installation of the two wetland islands.
“We are using the Mt. Pisgah State Park lake as a pilot for artificial floating islands as a way to reduce excessive nutrients in a lake,” said Matt Azeles, chief of the Bureau of State Park’s Resource Management section. “S.F. Foster Lake is an example of lakes receiving excessive nutrient loads from streams emptying into them and providing a ready source of growth for blue-green algae.”
Excellent candidates for the artificial islands are lakes receiving excessive phosphorus loads which lead to excessive blue-green algal blooms, Azeles said.
“Excessive blue-green algae blooms are not good for lake productivity and can lead to large anoxic zones in the deeper sections of a lake, particularly during the summer months,” said Azeles. “These conditions are not good for supporting a healthy lake ecosystem and fishery. A 250-square-foot artificial island has the ability to filter about the same amount of nutrients as one acre of natural wetlands.”
The wetland islands are a unique and innovative water-quality stewardship tool distributed by Floating Island Southeast in North Carolina.
BioHaven islands, comprised of a recycled plastic matrix, float on top of the water. Planted with beautiful native wetland plants, including iris, sedges, rushes, pickerelweed, and arrow arum, they provide habitat for birds and animals.
Meanwhile, under the surface, a dynamic process takes place: as the plants grow, their roots extend through the matrix and into the water. They, and the microbes that develop around them, effectively remove nutrients from the water.
The water quality consultant in this project, Princeton Hydro, calculates one 250-square-foot, fully grown island is equivalent to one wetland acre in terms of nutrient uptake.
“By the end of the summer, it is our hope that the plants placed on the two S.F. Foster Lake floating artificial islands would grow, mature and spread across the island,” Azeles said. “To the visitor, what should be seen by summer’s end would appear to be a vegetated, natural, small island in the lake, complete with wildlife using it as habitat.”
Because lake water nutrients are taken up in the plant material over the growing season, the bureau plans to harvest the plant growth over the winter when sufficient ice forms on the lake, allowing for a small mower or trimmer to cut the vegetation. It would then be raked and removed from the island, ensuring additional nutrients are not added to the lake ecosystem.
For this project, two 180 square-foot islands were installed at a cost of $12,890 for both island frames, plus $1,000 for plants. DCNR, DEP, and Bradford County Conservation District employees spent about 1.5 hours planting the frames before they were launched into the lake and anchored out of the main current in deeper water.
“Right now, we are considering artificial islands as one of the management practices to improve the water quality of Shawnee Lake,” Azeles said. “We are in the process of evaluating a report from Princeton Hydro, the water quality consultant hired by DCNR, which has analyzed water samples taken by DCNR State Parks and DEP and made recommendations for implementing best management practices to improve water quality at Shawnee Lake. Artificial wetlands are one of the BMPs recommended, and it is our hope to acquire funding to place artificial islands at Shawnee Lake to reduce the phosphorus load.”
Because this is a new initiative for state parks, the bureau will evaluate effectiveness at S. F. Foster Lake during this growing season before deploying them at Shawnee Lake, Azeles said.
“We are very excited to see how artificial floating islands work in a state park lake setting and hope they are viable and cost effective way of eliminating excessive nutrients when needed,” Azeles said.
Quickly, noted those who helped in their planting and anchoring, the new lake islands were well received by some—a beaver came over to investigate them before the tow boat made it back to shore.
In the future, park officials note, they will benefit an even larger lakeside community, including the visitors to Mt. Pisgah State Park.
(Reprinted from the May 25 DCNR Resource newsletter)
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5/30/2011 |
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