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Appl. Environ. Microbiol., Feb 1996, 486-493, Vol 62, No. 2
HL Drake, NG Aumen, C Kuhner, C Wagner, A Griesshammer and M Schmittroth
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(sup3)- to 10(sup4)-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(inf2)-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.
Copyright © 1996, American Society for Microbiology
Anaerobic Microflora of Everglades Sediments: Effects of Nutrients on Population Profiles and Activities
Lehrstuhl fur Okologische Mikrobiologie, BITOK, Universitat Bayreuth, 95440 Bayreuth, Germany, and Okeechobee Systems Research Division, South Florida Water Management District, West Palm Beach, Florida 33416-4680
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