ISSN:
1573-5117
Keywords:
reservoir
;
bacteria
;
methane
;
sulphides
;
methanotrophs
;
green sulphur bacteria
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract This work aims at studying the microbial and physical-chemical changes occurring in an equatorial hydroelectric reservoir Petit Saut (French Guiana), over three years, from the time it first filled. Since filling in January 1994, almost the whole water column has remained anoxic, with high concentrations of reduced elements (CH4, iron sulphides, H2S) originating from degradation of the submerged primary forest. These elements deoxygenated the water drained from the dam, as they were biologically and chemically oxidized in the river. Two major physiological guilds of microorganisms occurred. They showed a characteristic stratified arrangement in the lake, below and above an oxycline. Since flooding, we observed a cyclic development of phototrophic bacteria, assumed to be sulphur-oxidizers below the oxycline. The growth of this physiological guild seems to be strongly influenced by sulphide production and by the alternation between rainy and dry seasons. At the oxycline, the population of methane-oxidizing bacteria did not vary in the same way as the green sulphur bacteria. After a lag-phase, which was probably due to inhibition by excessive illumination in the upper water column in 1994, they developed and completely stopped diffusive methane emission in February 1995. The development of both bacterial guilds is directly correlated to changes in the level of the corresponding reduced elements from the bottom and dissolved in the lake water. The decreasing production of CH4 and sulphides induces a progressive extinction of methanotrophic bacteria and phototrophic sulphur-oxidizing bacteria. Meanwhile, the water is becoming clearer and algal populations proliferate in the upper water column, constituting an autochtonous source of organic carbon. Slowly, this aquatic ecosystem is reaching a low-activity equilibrium level related to reduced element production. It is evolving from a system ruled by an anaerobic organotrophic metabolism to an ecosystem governed by phototrophy.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1003707129170
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