Report by Samuel Mwenda
Coastal wetlands are crucial to natural and human systems due to the unique ecosystem services they provide. Wetland losses due to development remove natural buffers that sequestered pollutants before contamination of surface and ground water. As municipalities become more urbanized, storm-water runoff is discharged into estuarine systems, increasing the amount of nutrients, suspended sediments, and artificial substances contained within. Constructed wetlands have proven to be effective environmental management tools designed to improve water quality through biotic uptake, nutrient absorption, chemical decomposition, volatilization and sedimentation. Parameters measured include Total Kjeldahl Nitrogen (TKN), Nitrate, Phosphate, and Total Suspended Solids (TSS). Environmental education is an important component in addressing environmental problems. The three main objectives are 1) to determine the efficiency of a constructed wetland in lowering nutrient and suspended solids loads, and 2) to understand the current status of the residents’ awareness on storm-water related issues and 3) to summarize and assess restoration efforts to further enhance coastal storm-water management for urban areas.
Summary of Research
Coastal wetlands are crucial to natural and human systems due to the unique ecosystem services they provide. As transitional areas or ecotones between waterbodies and land, functions coastal wetlands typically provide, include stable habitats for numerous organisms, erosion reduction, environmental buffering, water quality remediation, and nutrient cycling. Currently, attempts at enhancing coastal resilience in the Halifax River watershed do not include programs determining a baseline of knowledge regarding water pollution issues and environmental awareness. Challenges to improving coastal resilience include habits and attitudes that reinforce existing paradigms regarding water pollution issues (Tal, 2004). Research focused on evaluation of public knowledge regarding water pollution sources is paramount to improving coastal resilience. The research gap is the relationship between utilizing a constructed wetland to reduce nutrients and environmental awareness of water pollution by the general public.
Constructed wetlands have proven to be effective environmental management tools designed to improve water quality through biotic uptake, nutrient absorption, chemical decomposition, volatilization and sedimentation (Chen, 2011). Additionally, they enhance current ecosystem services and functions of the area (Reed & Bastian, 1985). Despite not defined as a wetland by the United States Army Corps of Engineers (USACE), constructed wetlands contribute toward restoration of natural areas in the state of Florida (Santamaria et al., 2012).
Evaluating public knowledge of storm-water management techniques is vital as it enhances awareness of storm-water pollution, local ordinances, and how they impact the estuarine system. Insufficient knowledge of environmental conditions can exacerbate pollution as residents typically fertilize their lawns improperly. Residents that are cognizant of ecological factors contributing to pollution are more apt to change behavior such as discontinuation of enriched fertilizers as well as utilization of native vegetation (Noorhosseini et al., 2017).
The three main objectives are 1) to determine the efficiency of a constructed wetland in lowering nutrient and suspended solids loads, and 2) to understand the current status of the residents’ awareness on storm-water related issues and 3) to summarize and assess restoration efforts to further enhance coastal storm-water management for urban areas. A constructed wetland, using native vegetation to sequester nutrients prior to runoff reaching the Halifax River is the primary component of research examining resilience (Kadlec & Hey, 1994; Kurzbaum et al, 2012).
The study site is located within the Halifax River watershed. The Halifax River is an estuarine lagoon system with headwaters originating from Tomoka Bay, Volusia County, FL with an area of 842.2 km2 (208,122 acres) (Adamus et al., 1997). There are two main sub-watersheds that impact the water quality of the study site, the Reed and Port Orange canal watersheds (Fig. 1).
Both are small watersheds at the hydrologic unit code (HUC) 14, which is designated at a local scale. The Nova canal system which runs from the city of Port Orange north to the city of Ormond Beach, is around 17.7 km. The LPGA, Reed, and Halifax canals are part of the Nova canal system where each conveyance connects to the Halifax River draining untreated storm-water runoff into the already impaired river (Fig. 2).
With an area of 12.2 km2 (4841 acres), Reed canal was originally designed in the 1930s for mosquito control, to drain farmland, and carry waste back to the Halifax River (Marshall, Provost, & Associates, 1995). Situated within the larger Halifax River watershed and the Reed Canal system, Rinker’s Pond (Fig. 3) is a constructed wet detention pond intended to reduce the amount of nutrient and total suspended solids (TSS) from directly flowing into the Halifax River.
Surface water sampling occurred monthly in three locations at Rinker’s Pond: near the infall where water from Reed canal flows in, on the bank around the central area of the pond, and towards the outfall (Fig. 4).
At each location, triplicate samples were procured in order to reduce sampling error and outliers (Table 4).
Results and Conclusions
Trapping efficiency for TKN was 38% at the infall, and 18% overall. Trapping efficiency was very effective for phosphate with positive reduction rates occurring 93.3% of the sampling period. Trapping efficiency for phosphate was 30% at the infall, 22% at the outfall, and 26% overall.
Comparing monthly concentration levels to historical water quality data. The total nitrogen threshold criterion value for the Halifax River was .72 mg/L. While TKN only measures the organic forms of nitrogen, the criterion was exceeded seven times during the sampling period. They were as follows: February (.95 mg/L), March (.73 mg/L), April (.96 mg/L), May (.87 mg/L), June (.85 mg/L), July (.95 mg/L), and August (.74 mg/L). While short term trapping efficiency for phosphate was positive, the average percentage was still lower at ~ 30% compared to previous studies that reduced phosphate loads by 70% (Cooper & Knight, 1989).
Preparing for possible eventualities is necessary for environmental planners and managers in order to circumvent as well as navigate current and future conditions. Constructed wetlands are a feature or tool that planners employ to curb degradation on the front-end and slightly restore integrity to the system on the back-end. There are several aspects dealing with constructed wetlands that are important to monitor in the coming years. Future research concerning the study should examine indicators at varying scales within the full socio-ecological framework. Future research in FWS constructed wetlands or specifically for this project could look at ecological function based on seasonal aspects and variation. The current study examined variation on a monthly basis during a one-year period. To fully understand the hydrodynamics of the site it would be prudent to examine seasonal variation over a number of years. Continual monitoring and assessment of nutrient parameters at the site aids in this endeavor.
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