UNDERSTANDING AND PREDICTING THE IMPACT OF AGRICULTURE ON THE ENVIRONMENTAL INTEGRITY OF MANAGED WATERSHEDS
Location: Water Quality and Ecology Research
Title: Microbial and vegetative changes associated with development of a constructed wetland
Submitted to: Journal of Ecological Indicators
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 3, 2011
Publication Date: September 24, 2011
Citation: Weaver, M.A., Zablotowicz, R.M., Krutz, L.J., Locke, M.A., Bryson, C.T. 2012. Microbial and vegetative changes associated with development of a constructed wetland. Ecological Indicators. 13:37-45.
Interpretive Summary: Constructed wetlands in agricultural drainage waterways can serve as a best management practice (BMP) for removal of nutrients and pesticides. A vegetated waterway in Sunflower County, Mississippi that carried runoff water into an oxbow lake was converted into a two stage constructed wetland consisting of a non-excavated and an excavated cell. Wetland plant species colonized the constructed wetland, including the same species that are found in an adjacent, natural wetland. The soil microbial community was examined before wetland construction and for more than two years after construction. The microbial community quickly adapted to the altered hydrology and took on many of the characteristics of the reference wetland. Overall, the soil microbial community in the constructed wetland had higher overall metabolic activity than either the reference wetland or the upland area. This constructed wetland is providing several of the ecosystem services of natural wetland.
Wetlands may be constructed to provide several ecosystem functions. A constructed wetland receiving agricultural runoff water was observed prior to, and for more than two years after, establishment. The excavated portion of this wetland was compared to an undisturbed, upland area and to an adjacent, natural reference wetland. After construction the excavated cell was rapidly colonized by wetland plant species, including some exotic invasive weeds. Flourescein diacetate and triphenyl tetrazolium chloride enzyme assays indicated that the soil microbial community was more active in the excavated wetland cell than either of the two reference areas. The soil microbial community of the constructed wetland rapidly decreased in the abundance of fungi and gram-negative bacteria and increased in gram-positive bacteria and overall bacteria, as measured by fatty acid methyl esters. These shifts in the microbial community were consistent with the differences noted between the communities of the upland system and the reference wetland. Measurements of soil nitrogen and carbon did not indicate sequestration of C or N in the constructed wetland.