Abstract
Wetlands are naturally designed to mitigate floods and treat stormwater runoff, particularly in highly developed, low-elevation areas with abundant rainfall. However, a significant limitation is the lack of groundwater monitoring and a comprehensive understanding of the interactions between surface water and groundwater (SW-GW), especially when it comes to assessing the removal efficiency of contaminants. This study focuses on two types of wetlands, estuarine and freshwater, located in subtropical Southwest Florida. Both wetlands were partly engineered to function as ecological filters for their respective upstream communities. The first site is an inland, freshwater wetland and conservation area of Florida Gulf Coast University (FGCU) within the Estero Bay watershed. The second site is an estuarine, freshwater to brackish wetland at the Naples Botanical Garden (NBG) adjacent to Naples Bay and the Gulf of Mexico. We collected and analyzed key water quality indicators (NO3-, NO2-, NH4+, TN, TP, PO43-, pH, temperature, dissolved oxygen, and salinity) from nine GW wells (4 NBG, 5 FGCU) and eight pond and marsh location (3 NBG, 4 FGCU) over the wet (June 1 – October 31) and dry season (November 1 – May 31) to map and characterize general nutrient trends through the wetlands. Results show that neither SW nor GW exceeded the established their respective criteria for TN/TP and NOx related to eutrophication risk in Florida’s flowing waters and springs. NBG displayed higher NOx concentrations in SW compared to GW. Conversely, GW had higher concentrations of other nutrients. Notably, the variability for the inorganic species was influenced primarily by location. At FGCU, the nutrient comparisons between SW and GW showed a less discernable pattern; the variability in inorganic species, except for NH4+, was influenced by season rather than location. In summary, GW levels of TN, TP, and PO43− often exceeded the SW criteria. As a result, these findings suggest that regulatory frameworks focusing on SW should also be extended to include GW considerations. This study underscores the importance of accounting for both seasonal and spatial heterogeneity when seeking to understand nutrient dynamics in subtropical wetlands.
