22
The Radiocarbon Method to Estimate Primary Production
communities. For benthic biotopes, to measure photosynthetic production
in associations of macrophites, periphytonic overgrowths, or symbiotic animals
(sponges, corals), the oxygen method, with some improvements, has remained
preferable until now (Wetzel 1965; Wanders 1976). However, also for benthic
plants and symbionts, the radiocarbon method was gradually adapted and
employed by many researchers (Wetzel 1964a,b; Westlake 1963; Larkum 1983;
Sorokin 1993). All of these methods, either oxygen or radiocarbon, have
commOn restrictions when used in the bottle their versions, as well as having
their specific difficulties and faults. The problem of their adequacy, of the
correspondence of primary production thus measured in bottles with its rates
in water bodies in situ was many times thoroughly tackled and carefully discussed (Steeman-Nielsen 1958; Strickland 1960; Winberg 1960; Vollenweider
1974; Finenko 1978; Peterson 1978; Harris 1980; Eppley 1981; Sorokin 1987).
Numerous publications in the 1960s and 1970s on various faults in bottle
methods On their application to estimate in situ rates of metabolic processes
in aquatic communities, and On specific deficiencies in the oxygen, and especially in the radiocarbon methods of measuring the photosynthesis rate in
them, caused some hesitation; but a more careful approach to the problem later
changed this situation. Soon it became clear that most of these restrictions
and faults resulted from deficiencies in experimental techniques. Further
improvement in the method and strategy of sampling, quality, and capacity
of bottles, filtration procedures, kinds of filters used, etc., have finally made both
methods quite safe and adequate for measurement of gross photosynthetic
production in various kinds of water bodies and their biotopes. Basic attention
will be paid below to the radiocarbon method, but some recommendations
will also be given for the practical use of the oxygen method, because the latter
serves as reference for control of the validity of 14C estimations.
2.2 Historical Proceedings
The radiocarbon method was first used for measuring primary production in
oceanic waters in 1948-1950 by E. Steemann in Nielsen during the expedition
on the R/V Galathea (Steemann Nielsen 1951, 1952). This method appeared
at an appropriate time, when the discussion on global primary photosynthetic
production and the share of the oceans was beginning. At this time, it was also
known that large areas of the World Ocean are occupied by blue tropical
waters, which are extremely poor in phytoplankton. Nevertheless, estimations
in the 1940s and 1950s carried out by the oxygen bottle method had recorded
rather high rates of photosynthesis even in the most oligotrophic area of the
World Ocean - the Sargasso Sea (Riley 1944; Riley et al. 1949). These data
were used for global evaluations of primary production, which resulted in the
conclusion that the organic productivity of the ocean is comparable with that
of dry land; but soon this conclusion was challenged by data obtained by the
The Radiocarbon Method to Estimate Primary Production
communities. For benthic biotopes, to measure photosynthetic production
in associations of macrophites, periphytonic overgrowths, or symbiotic animals
(sponges, corals), the oxygen method, with some improvements, has remained
preferable until now (Wetzel 1965; Wanders 1976). However, also for benthic
plants and symbionts, the radiocarbon method was gradually adapted and
employed by many researchers (Wetzel 1964a,b; Westlake 1963; Larkum 1983;
Sorokin 1993). All of these methods, either oxygen or radiocarbon, have
commOn restrictions when used in the bottle their versions, as well as having
their specific difficulties and faults. The problem of their adequacy, of the
correspondence of primary production thus measured in bottles with its rates
in water bodies in situ was many times thoroughly tackled and carefully discussed (Steeman-Nielsen 1958; Strickland 1960; Winberg 1960; Vollenweider
1974; Finenko 1978; Peterson 1978; Harris 1980; Eppley 1981; Sorokin 1987).
Numerous publications in the 1960s and 1970s on various faults in bottle
methods On their application to estimate in situ rates of metabolic processes
in aquatic communities, and On specific deficiencies in the oxygen, and especially in the radiocarbon methods of measuring the photosynthesis rate in
them, caused some hesitation; but a more careful approach to the problem later
changed this situation. Soon it became clear that most of these restrictions
and faults resulted from deficiencies in experimental techniques. Further
improvement in the method and strategy of sampling, quality, and capacity
of bottles, filtration procedures, kinds of filters used, etc., have finally made both
methods quite safe and adequate for measurement of gross photosynthetic
production in various kinds of water bodies and their biotopes. Basic attention
will be paid below to the radiocarbon method, but some recommendations
will also be given for the practical use of the oxygen method, because the latter
serves as reference for control of the validity of 14C estimations.
2.2 Historical Proceedings
The radiocarbon method was first used for measuring primary production in
oceanic waters in 1948-1950 by E. Steemann in Nielsen during the expedition
on the R/V Galathea (Steemann Nielsen 1951, 1952). This method appeared
at an appropriate time, when the discussion on global primary photosynthetic
production and the share of the oceans was beginning. At this time, it was also
known that large areas of the World Ocean are occupied by blue tropical
waters, which are extremely poor in phytoplankton. Nevertheless, estimations
in the 1940s and 1950s carried out by the oxygen bottle method had recorded
rather high rates of photosynthesis even in the most oligotrophic area of the
World Ocean - the Sargasso Sea (Riley 1944; Riley et al. 1949). These data
were used for global evaluations of primary production, which resulted in the
conclusion that the organic productivity of the ocean is comparable with that
of dry land; but soon this conclusion was challenged by data obtained by the