Functions of wetland plant assemblages in water quality improvement

Author(s): Windham, E.; Shoemaker, C.; Ervin, G.

As wetland restoration continues, an understanding of drivers of natural wetland function becomes increasingly important for effective wetland restoration planning. Many studies have shown that wetlands act as filters for nutrient rich waters, in part due to macrophyte properties. Differences in plant characteristics such as biomass production, root oxygen release, and surface area available for microbial colonization have been suggested as possible contributors to greater nutrient removal. Thus, it is assumed that water quality parameters will vary among plant species assemblages, and that differences observed will correlate with one or more aspects of plant species biology or ecology that may prove useful in planning future restorations. Differences have been found in nitrogen removal rates among plant species in studies of monocultures grown in mesocosms mimicking wastewater treatment constructed wetlands, but almost no research has been done on assemblages in natural or restored wetlands. This study aims to identify the differences in water quality improvement among plant assemblages in natural and restored wetlands. Thirty natural and restored wetlands in the Mississippi portion of the Mississippi Alluvial Valley were sampled four times. Dissolved oxygen, temperature, pH, conductivity, turbidity, and oxidation-reduction potential were measured on-site, and water samples weretaken for analysis of nitrogen and total suspended solid content.Results showed that water quality parameters such as nitrate and phosphate concentrations, and pH were significantly correlated with plant growth form, in addition to being influenced by wetland type or by nutrient inputs on the surrounding landscape.

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