Measurement of Radioactivity
19
dynamics, the biogeochemical metabolism of carbon, sulfur, phosphorus, iron,
cobalt. Radioisotopes are applied as labels to trace the passing of the most
important biogenic elements such as carbon, sulfur, and phosphorus through
aquatic food webs and to reveal the chemical and biological mechanisms of
their transformation and dynamics. They are used also to measure the in situ
rates of such key processes in aquatic ecosystems as the production of organic
matter by algae and bacteria and its decomposition by the components of food
webs.
An important field of employment of radioisotopes in aquatic studies is
microbial ecology, where radioisotopic methods are used to investigate the
mechanisms and measure the in situ rates of many important processes which
proceed in aquatic environments with the participation of microbial communities (Ivanov 1956b; Sorokin 1959c, 1972b, 1975b; Karl 1986; Larson and
Hagstrom 1982). Without the radioisotopic methods, it is virtually impossible
to solve a key problem in modern hydro biology - the delineation of anthropogenic transformation of aquatic ecosystems based on the investigation of
the trophical structure and functioning at the level of energy balance and modeling. Indeed, the study of the trophical structure of aquatic biological communities is impossible without data on feeding spectra, food preferences, food
rations, and the assimilability of ingested food. The only way to obtain really
quantitative information in this field is to apply radioisotopic methods based
on the use of 14C and 3H. The inputs of external energy into the ecosystems
can not really be quantified without the use of radioisotopic methods to estimate primary plant and microbial production of organic matter.
The resolution of another basic problem of hydrobiology - nutrient availability, cycling, and retention, is now unimaginable without the use of 32p_
labeled phosphorus compounds. Most often, phosphorus is the basic limiting nutrient in aquatic ecosystems, and its availability and turnover rate
control structure, functional parameters, and redox conditions. The redox
conditions themselves represent one of the most important factors directly
controlling the basic parameters of aquatic ecosystems, especially in anthropologically stressed environments. The main process influencing redox conditions is bacterial sulfate reduction. Its quantification can be only done with the
use of 35S-labeled sulfate (Jorgensen 1977; Lein et al. 1992). These considerations make it clear that modern hydro biological investigations, if their goal
is to describe and to understand how the aquatic ecosystems are structured
and how they work, have to be based on the use of radioisotopic methods
(Smith and Horner 1981). Nevertheless, until present, very often the use of
radioisotopes has largely remained a matter of individual initiative by enthusiasts rather than the general policy of the chiefs who often prefer to avoid
the problems of state regulations for the use of nuclear products. It is also the
case that the staff of laboratories oppose the use of radioactive materials as
being hazardous for health. Such obstacles to a wider official use of radioisotopes in hydro biological studies are usually the result of ignorance and misunderstanding. Fearsome terms like radionuclides or radioisotopes scare the
19
dynamics, the biogeochemical metabolism of carbon, sulfur, phosphorus, iron,
cobalt. Radioisotopes are applied as labels to trace the passing of the most
important biogenic elements such as carbon, sulfur, and phosphorus through
aquatic food webs and to reveal the chemical and biological mechanisms of
their transformation and dynamics. They are used also to measure the in situ
rates of such key processes in aquatic ecosystems as the production of organic
matter by algae and bacteria and its decomposition by the components of food
webs.
An important field of employment of radioisotopes in aquatic studies is
microbial ecology, where radioisotopic methods are used to investigate the
mechanisms and measure the in situ rates of many important processes which
proceed in aquatic environments with the participation of microbial communities (Ivanov 1956b; Sorokin 1959c, 1972b, 1975b; Karl 1986; Larson and
Hagstrom 1982). Without the radioisotopic methods, it is virtually impossible
to solve a key problem in modern hydro biology - the delineation of anthropogenic transformation of aquatic ecosystems based on the investigation of
the trophical structure and functioning at the level of energy balance and modeling. Indeed, the study of the trophical structure of aquatic biological communities is impossible without data on feeding spectra, food preferences, food
rations, and the assimilability of ingested food. The only way to obtain really
quantitative information in this field is to apply radioisotopic methods based
on the use of 14C and 3H. The inputs of external energy into the ecosystems
can not really be quantified without the use of radioisotopic methods to estimate primary plant and microbial production of organic matter.
The resolution of another basic problem of hydrobiology - nutrient availability, cycling, and retention, is now unimaginable without the use of 32p_
labeled phosphorus compounds. Most often, phosphorus is the basic limiting nutrient in aquatic ecosystems, and its availability and turnover rate
control structure, functional parameters, and redox conditions. The redox
conditions themselves represent one of the most important factors directly
controlling the basic parameters of aquatic ecosystems, especially in anthropologically stressed environments. The main process influencing redox conditions is bacterial sulfate reduction. Its quantification can be only done with the
use of 35S-labeled sulfate (Jorgensen 1977; Lein et al. 1992). These considerations make it clear that modern hydro biological investigations, if their goal
is to describe and to understand how the aquatic ecosystems are structured
and how they work, have to be based on the use of radioisotopic methods
(Smith and Horner 1981). Nevertheless, until present, very often the use of
radioisotopes has largely remained a matter of individual initiative by enthusiasts rather than the general policy of the chiefs who often prefer to avoid
the problems of state regulations for the use of nuclear products. It is also the
case that the staff of laboratories oppose the use of radioactive materials as
being hazardous for health. Such obstacles to a wider official use of radioisotopes in hydro biological studies are usually the result of ignorance and misunderstanding. Fearsome terms like radionuclides or radioisotopes scare the