The construction of US highway 41 (Tamiami Trail) to connect the east and west coasts of Florida resulted in a significant ecological and hydrologic barrier between the northern and southern Everglades, separating the modern day Water Conservation Areas (WCAs) from Everglades National Park (ENP). Recently the Tamiami Trail bridge was constructed to allow additional water deliveries to ENP to restore ecological balance especially by restoring “historic” flows. One concern with increased flows is the potential to increase the phosphorus load to the Northeast Shark River Slough (NESS). Concerns are based on the ecological effects of increased nutrients, especially P, have had in other parts of the system. Previous work has shown that areas around culverts entering into ENP had P-enriched soils, increased the biomass of woody vegetation, and other signs of “more eutrophied” conditions. This research study evaluates the effect of nutrient availability changes on ecological indicators such as soil, flocculent layer, periphyton etc. and specifically on the functioning of the soil microbial population across different gradients. Soil, periphyton, and flocculent detrital organic matter (floc) samples were collected with distance downstream (e.g. 10, 100, 200, 250, 750 m) from inflows near areas directly affected by the bridge and other near canal sites not currently in the bridge flow. Those samples were analyzed for total P, TC, TN and other physiochemical parameters using standard methods. Microbial analysis such as enzymatic activity (phosphatase and glucosidase) and CO2 emission were also analyzed for those collected soil samples.
Results/Conclusions:
Results showed that soil TP concentrations ranged widely from 30-2600 µg g-1 and specifically highest concentrations were found downstream of the historic flow paths i.e. culvert discharges, canal effluents. Organic matter content ranged from 30-80% across all sites and seasons. Periphyton was abundant and widely distributed throughout the bridge and census sites of NESS region. However, at near canal sites, where soils are more P-enriched, very little periphyton was found. So average TP concentrations in soil, floc, and periphyton samples were significantly higher in halo or culvert sites as compared to transect sites indicating the legacies of recently constructed Tamiami bridge to restore the ecological balance in Southern Everglades. It was also found out that the respiration of organic matter by the microbial population at most of the NESS sites are not P-limited but may be limited by the availability of labile C.