222
Use of Radioisotopes to Study Biogeochemical Cycling of Elements
specialized group of methanotrophic bacteria (Malashenko et al. 1978). These
bacteria produce a considerable amount of microbial biomass during its oxidation, which is an important source of food for the water fauna (Sorokin
1959c). This source of food happens to be especially important in the spreading areas on the deep oceanic floor, in the redox layers in water columns, in
the near-bottom water layers and in the upper layer of bottom sediments. In
lakes and reservoirs the microbial biomass produced during methane oxidation is especially important in winter under ice, where it actually forms the
only source of fresh, particulated food, thus allowing the successful wintering
of the stock of filtering zooplankton (Sorokin 1955a). Methane gas is the main
energy-rich end product of anaerobic decomposition of organic matter in
bottom sediments. When migrating from the bottom up to the water column,
it contributes largely to the pelagic productivity, being at the same time a
significant factor controlling the oxygen regime in water bodies. In the deep
layers of oceans and especially in the sediments of deep cold seas, large
reserves of methane exists as crystal-hydrates in their jelly crystal form. From
this reserve, methane gas gradually evolves into the water column and the
energy which it contains via the production of methanotrophic bacteria is
included within the energy balance of marine ecosystems. The same happens
with methane, which enters water bodies from the juvenile sources in areas of
volcanic activity and gas seeps. Methanotrophic microflora supports the existence of specific symbiotic communities of hydrobionts and provides additional particulated food for the pelagic and benthic fauna during the
production of its biomass in such areas (Kuznetsov 1952, 1970; Sorokin
1955a,b, 1957, 1965, 1972b; Sorokin et al. 1992a, 1994; Rudd and Hamilton
1978; Malashenko et al. 1978; Nesterov and Ivanov 1983; Kuznetsov et al.
1985).
The above considerations make it clear that the estimation of the activity
and localization of methane-oxidizing microflora, as well as the evaluation of
the in situ rates of methane oxidation, coupled with the production of biomass,
are among the most important parameters needed for characterization of the
structure and functioning of aquatic ecosystems, and especially those having
redox zones and anoxic layers in their water column. The radioisotopic techniques could be used for solving problems concerning both the ecology and
the functional activity of methane-oxidizing microflora in water basins.
Because of the specific nature of methanotrophic microflora, which oxidizes methane and uses it as a sole energy source, the very presence of their
active popUlation is a very sensitive and sure indication of the presence and
permanent flow of methane in a given aquatic habitat or water layer. This
feature of methane-oxidizing microflora was used in practice for the location
of the oil deposits of hydrocarbon gas seeps and hydrothermal exhalations
(Nesterov and Ivanov 1983).
The study of methane oxidation in a water body includes following steps:
(1) chemical analysis of the ambiental content of methane in water columns
and bottom sediments, (2) estimation of the distribution of active popUlations
Use of Radioisotopes to Study Biogeochemical Cycling of Elements
specialized group of methanotrophic bacteria (Malashenko et al. 1978). These
bacteria produce a considerable amount of microbial biomass during its oxidation, which is an important source of food for the water fauna (Sorokin
1959c). This source of food happens to be especially important in the spreading areas on the deep oceanic floor, in the redox layers in water columns, in
the near-bottom water layers and in the upper layer of bottom sediments. In
lakes and reservoirs the microbial biomass produced during methane oxidation is especially important in winter under ice, where it actually forms the
only source of fresh, particulated food, thus allowing the successful wintering
of the stock of filtering zooplankton (Sorokin 1955a). Methane gas is the main
energy-rich end product of anaerobic decomposition of organic matter in
bottom sediments. When migrating from the bottom up to the water column,
it contributes largely to the pelagic productivity, being at the same time a
significant factor controlling the oxygen regime in water bodies. In the deep
layers of oceans and especially in the sediments of deep cold seas, large
reserves of methane exists as crystal-hydrates in their jelly crystal form. From
this reserve, methane gas gradually evolves into the water column and the
energy which it contains via the production of methanotrophic bacteria is
included within the energy balance of marine ecosystems. The same happens
with methane, which enters water bodies from the juvenile sources in areas of
volcanic activity and gas seeps. Methanotrophic microflora supports the existence of specific symbiotic communities of hydrobionts and provides additional particulated food for the pelagic and benthic fauna during the
production of its biomass in such areas (Kuznetsov 1952, 1970; Sorokin
1955a,b, 1957, 1965, 1972b; Sorokin et al. 1992a, 1994; Rudd and Hamilton
1978; Malashenko et al. 1978; Nesterov and Ivanov 1983; Kuznetsov et al.
1985).
The above considerations make it clear that the estimation of the activity
and localization of methane-oxidizing microflora, as well as the evaluation of
the in situ rates of methane oxidation, coupled with the production of biomass,
are among the most important parameters needed for characterization of the
structure and functioning of aquatic ecosystems, and especially those having
redox zones and anoxic layers in their water column. The radioisotopic techniques could be used for solving problems concerning both the ecology and
the functional activity of methane-oxidizing microflora in water basins.
Because of the specific nature of methanotrophic microflora, which oxidizes methane and uses it as a sole energy source, the very presence of their
active popUlation is a very sensitive and sure indication of the presence and
permanent flow of methane in a given aquatic habitat or water layer. This
feature of methane-oxidizing microflora was used in practice for the location
of the oil deposits of hydrocarbon gas seeps and hydrothermal exhalations
(Nesterov and Ivanov 1983).
The study of methane oxidation in a water body includes following steps:
(1) chemical analysis of the ambiental content of methane in water columns
and bottom sediments, (2) estimation of the distribution of active popUlations