Heterotrophic Microbial Activity in Northern Everglades Wetland Soils

摘要

Phosphorus loading to the northern Florida Everglades has been implicated in causing changes in vegetation, peat accretion rates, and other soil physical-chemical properties. Our study focused on determining the influence of P loading on aerobic and anaerobic heterotrophic microbial activities (measured as CO₂ and CH₄ production) in detritus and soil collected from the Water Conservation Area 2a (WCA-2a) of the Everglades. Heterotrophic microbial activities measured under both field and laboratory conditions were higher in areas impacted by P loading as compared to the unimpacted interior marsh. Microbial heterotrophic activities were higher in detritus and surface soils and decreased with depth. In field studies, CO₂ production rates in anaerobic soils were approximately 64% of those observed in aerobic soils. Additions of substrates containing C, N, and P generally enhanced heterotrophic microbial activity. In laboratory studies involving addition of various inorganic electron acceptors, increased microbial activities in the order of O-₂ > NO-₃ = SO2-₄ > HCO-₃ were observed. Microbial CO₂ production rates under denitrifying and sulfate reducing conditions ranged from 30–42% and 29–44%, respectively, of aerobic rates. Methane production rates were only up to 9% of aerobic CO₂ production rates. Both CO₂ and CH₄ production rates were significantly correlated with soil P parameters and microbial biomass. Enhanced heterotrophic microbial activities resulting from P loading has the potential to increase turnover of organic matter which may lead to increased supply of bioavailable nutrients to emergent macrophytes and periphyton and higher nutrient concentrations in the water column.