Heterogeneity of bacterial enzymes as nutrient enrichment signature in tropical wetlands: A sustainable environmental management tool

Abstract

High bacterial activities of urease, L-asparaginase, nitrite and nitrate reductase in some severely ecologically stressed ponds (P2, P4, P6 and P10) with DO (2.65–4.5 mg/L), COD (226.4–322.5 mg/L) and nitrogen enrichment (NH4N:0.109–0.817 mg/L; NO2N: 0.005–0.079 mg/L; NO3N: 0.306–1.511 mg/L) condition indicated nutrient induced enhanced bacterial metabolic pathways. Similarly, high acid phosphatase enzyme activity (0.2865–0.749 U/ml) reflected phosphorus enrichment (0.281–0.949 mg/L) stress in all ponds maximum for agricultural waste received ponds when compared with standards (0.084 mg/L). Various bacterial isolates of ammonifying bacteria (AB), heterotrophic bacteria (HB), phosphate solubilizing bacteria (PSB), nitrifying bacteria (NB), denitrifying bacteria (DNB) groups showed higher activities of urease (AB1P10, HB1-P4, P6), L-asparaginase (HB1P2, NB1P2), acid phosphatase (PSB1-P2, P4, P10), nitrate reductase (NB2P4, NB1P6 and AB1P2) and nitrite reductase (DNB1P2, DNB1P4, AB2P2 and NB1P7). The changed degraded microbial pathways expressed through heterogeneous response of bacterial enzymes has reflected the nutrient enrichment induced altered nutrient cycle in different selected ponds. Thus, this heterogeneity can be used as stress signature assessment of the restoring capacity of the disturbed ecosystem back to ecological resilience.The extent of deviation of water quality parameters (DO 54–126%; COD 1030–1135%; PO4-P 390–1029%) from the standards in relation with the heterogeneity of bacterial enzyme activities were used to categorize the different stress status i.e., severely stress, moderately stress and poorly stress of the studied wetlands as a tool to achieve sustainability.

Keywords

• Wetland ecosystem stress
• Nutrient cycling bacterial enzymes
• Sustainability signature