Biogeochemical characteristics of the Everglades sloughs

Everglades sloughs are alkaline hardwater systems. Mean water column dissolved phosphate (5 μg/L) and TP (9 μg/L) concentrations in the sloughs are typical of oligotrophic waters. Molar ratios of dissolved inorganic N and P (DIN:DIP = 28:1) in the surface waters suggest that P may be limiting the aquatic primary productivity in the Everglades sloughs. Variations in water column TP and TN in the sloughs were inversely related to the water depth fluctuations (P <0.0001) suggesting a strong link with hydrology. Periphyton and macrophytes in the sloughs exhibited N/P ratios indicative of depletion in P relative to N. The N/P ratios in the Everglades slough communities were in the upper range of values reported for aquatic plants from other ecosystems. The N/P ratios in periphyton were higher than macrophytes suggesting that P depletion was even greater for periphyton. As a result any introduced inorganic phosphate was taken up rapidly by the periphyton reducing the water column PO4-P to near background levels. Our results suggest that C/N/P ratios of the periphyton provide a reliable measure of the P-status of the Everglades sloughs whereas the water column P concentration may not truly reflect the P-status of the system. Periphyton mat also plays an important role in oxygenating the water column of the sloughs. Experimental results show that a decline in periphyton mat cover will result in a decrease in the water column dissolved oxygen concentration and may also lead to other ecosystem changes by enhancing the PAR availability to the slough bottom.

Duke Scholars

Author Curtis J. Richardson Environmental Natural Science