Distribution and Stability of Sulfate-Reducing Prokaryotic and Hydrogenotrophic Methanogenic Assemblages in Nutrient-Impacted Regions of the Florida Everglades

Abstract

Although the influence of phosphorus loading on the Everglades ecosystem has received a great deal of attention, most research has targeted macro indicators, such as those based on vegetation or fauna, or chemical and physical parameters involved in biogeochemical cycles. Fewer studies have addressed the role of microorganisms, and these have mainly targeted gross informative parameters such as microbial biomass, enzymatic activities, and microbial enumerations. The objectives of this study were to characterize the dynamics of sulfate-reducing and methanogenic assemblages using terminal restriction fragment length polymorphism (T-RFLP) targeting the dissimilatory sulfite reductase (dsrA) and methyl coenzyme M reductase (mcrA) genes, respectively, and assess the impact of nutrient enrichment on microbial assemblages in the northern Everglades. T-RFLP combined with principal component analysis was a powerful technique to discriminate between soils from sites with eutrophic, transitional, and oligotrophic nutrient concentrations. dsrA T-RFLP provided a higher level of discrimination between the three sites. mcrA was a relatively weaker system to distinguish between sites, since it could not categorically discriminate between eutrophic and transition soil samples, but may be useful as an early indicator of phosphorus loading which is altering hydrogenotrophic methanogenic community in the transition zones, making them more similar to eutrophic zones. Clearly, targeting a combination of different microbial communities provides greater insight into the functioning of this ecosystem and provides useful information for understanding the relationship between eutrophication effects and microbial assemblages.

Distribution, Activities, and Interactions of Methanogens and Sulfate-Reducing Prokaryotes in the Florida Everglades

“…The soil P concentrations in the samples used for this study were 1.28 g · kg Ϫ1 in site F1, the northernmost site; 0.59 g · kg Ϫ1 in site F4; and 0.25 g · kg Ϫ1 in site U3, the southernmost site (Table 1). These values are in good agreement with previously reported results (42,51). In contrast to the soil P concentration gradient, a sharp gradient in SO 4 2Ϫ concentrations was not observed in surface waters (176 to 200 M) or soil pore waters (39 to 56 M) (52).…”

“…A very large body of work has been published on changes that the P additions have brought to the greater WCA-2A ecosystem, ranging from the distribution of endangered vertebrates to changes in biogeochemical cycling (49,58). The present study builds on previous studies on the distribution and function of methanogenic and sulfidogenic guilds (10,42,51) and investigates controls on methanogenic pathways as a function of position along the nutrient gradient.…”

Fatty Acid-Oxidizing Consortia along a Nutrient Gradient in the Florida Everglades

“…Sulfate-reducing guilds in U3 are dominated by incomplete acetate oxidizers (4,6), such that SRP may be limited in their ability to metabolize acetate in these soils. In addition, low sulfate concentrations in these microcosms likely prevented enrichment of SRP in U3 microcosms, possibly resulting in increased acetate accumulation.…”

“…in sloughs to dense stands of cattail (Typha domingensis Pers.). Significantly greater primary productivity in eutrophic regions resulted in greater carbon input to the soils, leading to greater peat accumulation (2,27,37) and higher rates of methanogenesis and anaerobic respiration (4)(5)(6)(7). Concomitant with larger amounts of available carbon in eutrophic regions are changes in the composition and increases in the sizes of specific microbial groups responsible for carbon cycling, such as methanogens, fermenters, and sulfate-reducing prokaryotes (SRP) (4-7, 14, 37; I. Uz and A. Ogram, submitted for publication).…”

Structure and Function of Methanogens along a Short-Term Restoration Chronosequence in the Florida Everglades

“…The methanogen-specific mcrA has been used as a molecular marker to study the distribution of methanogens in many terrestrial environments, including nutrient-impacted regions of the Florida Everglades (4,5).…”