Effects of Hydrologic Flow on Enzyme Activity in Constructed Wetland Soils.

In constructed wetlands like the Everglades Stormwater Treatment Areas (STAs), microbial processes play a key role in nutrient removal. Specifically, extracellular enzyme production regulates organic decomposition, nutrient mineralization, and indicate overall nutrient limitation. Hydrologic flow and its management directly effects nutrient distribution and loading, which likely alters microbial functions such as enzymatic activity; however, there are few studies that assess the effect of flow on enzyme activities. In this study, enzymes for P (phosphomonoesterase, APA and phosphodiesterase, BisP), C (β-glucosidase, BG), and N (Leucine aminopeptidase, LAP and β-N-acetylglucosaminidase, NAG) were analyzed at inflow, midflow, and outflow stations of STA 2 Cell 3 during stagnant and flowing conditions. Our results indicate that enzyme activity generally followed the nutrient gradient of the STA-2 Cell 3, with enzyme activity increasing from inflow to outflow under stagnant and flowing conditions. Under flowing conditions, overall enzyme activity was stimulated, especially at the outflow. In general, hydrologic flow enhanced enzyme activity without consistent changes in nutrient concentration. Seasonally and under flowing conditions, Fall had the highest enzyme activity at midflow and outflow. Future research will focus on the different rates (designated low, moderate, and high hydraulic loading rate) of flow and/or the enzyme activities on a microbial biomass carbon basis in response to nutrient availability and stoichiometry in the water column.