Bioavailability of Organic Phosphorus in a Submerged Aquatic Vegetation–Dominated Treatment Wetland

Abstract

Enzymatic hydrolysis and mineralization of organic phosphorus (P) were determined in surface water samples collected from inflow and outflow of a submerged aquatic vegetation (SAV)-dominated treatment wetland of the Florida Everglades. Water samples were fractionated into three size fractions (> 0.4 micron, < 0.4 to > 0.05 micron, and < 0.05 micron) with a sequential flow filtration technique. The fractionated water samples were incubated to hydrolyze with alkaline phosphatase (APase) and phosphodiesterase (PDEase), and to mineralize at different redox and pH. Unlike APase, which hydrolyzed < or = 10% of organic P, PDEase hydrolyzed > or = 71% of organic P in unfiltered water from both inflow and outflow waters, suggesting the domination of bioavailable diester P in the water. Phosphodiesterase completely hydrolyzed organic P in the < 0.4- to > 0.05-micron and < 0.05-micron fractions, as compared with < or = 35% in the > 0.4-micron fraction. However, the P mineralization in inflow and outflow waters at different redox and pH showed that P associated with particulate > 0.4 micron had been mineralized the most. Phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy showed that surficial sediments from the inflow region contained a high proportion of polynucleotides, nucleoside monophosphates, and previously unreported glycerophosphoethanolamine and phosphoenolpyruvates. However, at the outflow, the relative proportion of polynucleotides and nucleoside monophosphates was reduced substantially. This suggests that the SAV wetland may sequester P via accretion of organic matter.

A preliminary study on estimating extra-cellular nitrate reductase activities in estuarine systems

“…Nitrate reductase (9029-27-0; obtained from MP Biomedicals Inc., Solon, OH, USA) was evaluated for its capacity to denitrification of NO 3 -in the surface waters and available NO 3 -in sediments by batch incubation at 37 °C as described for phosphatases by (Juma and Tabatabai, 1977;Pant and Warman, 2000;Pant et al, 2002). Unless otherwise stated, all the buffer solutions were prepared from tris-HCl.…”

“…The nitrate reductase solution contained 0.5 unit enzyme activity·mL -1 . To inhibit microbial activities during the incubation, 50 µL of 5.2% sodium azide (NaN 3 ) solution was added (Pant et al, 2002) to the 15 mL triplicate samples (surface waters and sediment extracts) to yield a final concentration. Thereafter, 0.4 mL nitrate reductase solution was added to each vial, and incubated for 6 h at 37 °C.…”

“…Enzymes mediate a wide variety of biogeochemical chemical reactions, and have been linked to nutrients cycling in soils/sediments (Burns, 1986;Pant and Warman, 2000;Furlan and Pant, 2006) and aquatic systems (Pant et al, 2002). The stability of enzymes can be increased by immobilization on a suitable solid support (Warman and Isnor, 1990;Pant and Warman, 2000).…”

“…Enzyme catalyzed reactions are no exceptions to the Arrhenius theory. Mineralization and immobilization of nutrients such as N and P in waters and soils/sediments are strongly influenced by temperature (Pant et al, 2002). As the mineralization of detrital material proceeds, associated nutrients including N and P may release and transport to the water column.…”

“…Several studies on decompositions of organic matter in sediments reported that aerobic decomposition could be faster (Lee, 1992) or slower (Sun et al, 1993). Soil/sediment microorganisms mineralize organic P through the secretion of various phosphatases (Juma and Tabatabai, 1977;Pant et al, 2002). Similarly, plants can utilize organic P fractions in soils by means of phosphatase activity (Pant et al, 1994a(Pant et al, , 1994bFurlan and Pant, 2006).…”