Floating Wetlands for Cost Effective Water Quality and Habitat Restoration

A variety of floating wetlands have been used to improve water quality in estuaries and various types of freshwater bodies. These systems also increase fish and wildlife habitat, and benefit aesthetic and recreational values. The primary mechanism for water quality improvement is the uptake of dissolved nutrients by biofilm growth on wetland plant roots, which reduces nutrient availability for floating or attached algae growth in the water body. Advanced floating wetland designs provide aeration and circulation of water through the root system to increase nutrient uptake by the biofilm, and also reduce internal nutrient inputs caused by low dissolved oxygen and high pH in the water and underlying sediments of stagnant water bodies. In addition, artificial root systems can be added to floating wetlands to greatly increase the surface area for biofilm growth. For example, floating wetlands have reduced total phosphorus concentrations by 40 - 90 percent in eutrophic lakes and ponds. Wetland designs may include a diverse structure of native marine or freshwater plants, bird nesting habitat or temporary bird exclusion netting, forage fish or salmon rearing habitat among the root system, and underwater netting for predatory fish exclusion. Wetland structures consisting of HDPE tubing attached by stainless steel shackles, and a plant matrix consisting coir fibers within nylon netting provides systems that are resistant to waves, corrosion, and decay. Floating wetland shapes and sizes vary to fit site constraints, and are particularly suitable for areas with hardened shorelines where construction of shoreline wetlands on adjacent property is costly or infeasible. At a cost of $30/square foot, floating wetlands provide a cost effective alternative to shoreline wetland construction for water quality and habitat restoration in Puget Sound and its freshwater bodies