Contrasting effect of protease on the enzymatic hydrolysis of dissolved organic P in constructed wetlands

Phosphorus (P) is one of the major nutrients responsible for altering the natural trophic status of wetlands, including the Everglades ecosystem in South Florida. The runoff from surrounding agricultural areas is one of the main sources of P to the natural water bodies in the Everglades ecosystem. Constructed wetlands such as the stormwater treatment areas (STAs) have been effectively used to reduce P concentrations in the Everglades. However, a significantly higher proportion of dissolved organic P fractions in these waters make P reduction efforts very challenging. Recently several studies have explored the use of a hydrolytic P enzyme intervention approach to assessing the bioavailability of dissolved organic P. This study adds to this effort by exploring the interaction between extracellular enzymes in the ecosystem. We present the effect of proteases on the effectiveness (efficiency) of phosphomonoesterase (PME) and phosphodiesterase (PDE) activity in site water from the Everglades STA. Results suggest a contrasting effect of protease on the two phosphatase enzymes, with a positive effect on PME and a negative effect on PDE in STA site water. For example, protease addition increased the alkaline phosphatase activity in PME amended site water by 13% compared to PME alone. Likewise, protease addition decreased the Bis-P activity in PDE amended site water by 15% relative to PDE alone. Further examination of the direct effect of protease on PME and PDE on dissolved organic matter (DOM) free water revealed that the negative effect of protease on PDE was higher than on PME suggesting a higher affinity of protease to PDE. Considering the implications of these findings, where factors influencing phosphatase enzyme activity in STA site water are identified, a mechanistic examination of protease interaction with phosphatases in the presence of DOM is warranted.