Hl. Drake et al., ANAEROBIC MICROFLORA OF EVERGLADES SEDIMENTS - EFFECTS OF NUTRIENTS ON POPULATION PROFILES AND ACTIVITIES, Applied and environmental microbiology, 62(2), 1996, pp. 486-493
Everglades sediments (wetland soils) near sources of agricultural runo
ff had low redox potentials, were blackened with sulfide, and displaye
d high porewater phosphorus (total) concentrations and high water colu
mn conductivities, These sediments yielded 10(3)- to 10(4)-fold-higher
numbers of culturable anaerobes, including methanogens, sulfate reduc
ers, and acetate producers, than did sediments from Everglades and Lak
e 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 microflor
a in the sediments most likely influenced by agricultural runoff, Desp
ite these differences in microfloral patterns, methylmercury and total
mercury levels were similar among these contrasting sediments, Althou
gh available sulfate and phosphorus appeared to stimulate the producti
vity of sulfate reducers in Everglades sediments, the number of cultur
able 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 ma
tter. For sediments nearest sources of agricultural runoff, phosphorus
temporarily enhanced acetate formation and initially suppressed metha
ne production, sulfate enhanced acetate formation but did not signific
antly 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 pre
sent in greater culturable numbers than denitrifiers. In microcosms, a
cetate was a major source of methane, and supplemental hydrogen was di
rected towards the synthesis of acetate via CO2-dependent acetogenesis
. These findings demonstrate that Everglades sediments nearest agricul
tural runoff have enhanced anaerobic microbial profiles and that the a
naerobic microflora are poised to respond rapidly to phosphate, sulfat
e, and nitrate input.