Anaerobic microflora of everglades sediments: effects of nutrients on population profiles and activities

Abstract

Everglades sediments (wetland soils) near sources of agricultural runoff had low redox potentials, were blackened with sulfide, and displayed high porewater phosphorus (total) concentrations and high water column conductivities. These sediments yielded 10 3-to 10 4-fold-higher numbers of culturable anaerobes, including methanogens, sulfate reducers, and acetate producers, than did sediments from Everglades and Lake Okeechobee comparative control sites not as directly associated with agricultural runoff. These observations demonstrated that there was a general, rather than specific, enhancement of the anaerobic microflora in the sediments most likely influenced by agricultural runoff. Despite these differences in microfloral patterns, methylmercury and total mercury levels were similar among these contrasting sediments. Although available sulfate and phosphorus appeared to stimulate the productivity of sulfate reducers in Everglades sediments, the number of culturable sulfate reducers did not directly correspond to the concentration of sulfate and phosphorus in porewaters. Microcosms supplemented with sulfate, nitrate, and phosphate altered the initial capacities of the sediment microflora to produce acetate and methane from endogenous matter. For sediments nearest sources of agricultural runoff, phosphorus temporarily enhanced acetate formation and initially suppressed methane production, sulfate enhanced acetate formation but did not significantly alter the production of methane, and nitrate totally suppressed the initial production of both methane and acetate. In regards to the latter, microbes capable of dissimilating nitrate to ammonium were present in greater culturable numbers than denitrifiers. In microcosms, acetate was a major source of methane, and supplemental hydrogen was directed towards the synthesis of acetate via CO 2-dependent acetogenesis. These findings demonstrate that Everglades sediments nearest agricultural runoff have enhanced anaerobic microbial profiles and that the anaerobic microflora are poised to respond rapidly to phosphate, sulfate, and nitrate input.

Cellulolytic, fermentative, and methanogenic guilds in benthic periphyton mats from the Florida Everglades

“…1). A similar accumulation of acetate was noted in previous studies of the soils of the area (Drake et al, 1996;Chauhan & Ogram, 2006). It is likely that this accumulation of acetate resulted from the inhibition of syntrophic acetate oxidation (SAO), potentially a major pathway for acetate consumption and subsequent methanogenesis, in these samples (Chauhan & Ogram, 2006), and that this inhibition of the syntrophic consumption of acetate probably resulted from the accumulation of H 2 produced during fermentation in these microcosms.…”

Cellulolytic and fermentative guilds in eutrophic soils of the Florida Everglades

“…Similar trends have also been observed in microcosms containing rice roots (Lehmann-Richter et al, 1999). Drake and co-workers (Drake et al, 1996) reported similar results for Everglades soils, and attributed the lag to inhibition of acetotrophs by accumulation of H 2 . Acetotrophic methanogens are inhibited by H 2 ; when CO 2 was added to microcosms in their studies, H 2 was consumed with CO 2 by homacetogens to form acetate, and acetotrophic methanogenesis increased significantly.…”

Intermediary ecosystem metabolism as a main driver of methanogenesis in acidic wetland soil

“…Methanogenesis by peat from a mildly acidic bog in Germany was stimulated by supplemental H2-CO2 and inhibited by supplemental acetate and formate (Horn et al, 2003). Reductive methanogenesis from CO2 was also a predominant source of methane with Finnish wetland soils (Metje and Frenzel, 2005), while acetate was seen to be an important source of methane in Everglade wetland soils (Drake et al, 1996). Methylotrophic and formate-consuming methanogens appear to be relatively insignificant in wetland ecosystems (Horn et al, 2003;Bräuer et al, 2004); however, such speculation must be qualified in light of the very limited database.…”