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The Radiocarbon Method to Estimate Primary Production
2.4 Faults in the Radiocarbon Method and Problems
in its Calibration
Above, it was also mentioned that a voluminous literature exists on various
"faults" of the radiocarbon method to determine pelagic primary production
(Lean and Burnison 1979). Acquaintance with this literature and navigating
through it can leave some feeling of frustration in an inexperienced researcher.
Therefore, in conclusion to this part, it seems reasonable to present a short
review and interpretation of this literature.
The faults of the radiocarbon method can be separated into two groups:
1. those connected with the bottle effect - with the confinement of natural
assemblages of microplankton within an isolated space of experimental
bottles, and
2. special deficiencies of the radiocarbon method itself.
Before referring to the discussion, it should be mentioned that in appropriate
publications, the matter of faults in radiocarbon methodology for primary production estimation is often somewhat exaggerated, possibly because proving
its deficiency was the main goal of the publication. A typical example is a sensational publication by Gieskes et a1. (1979) about a gross (1 order of values)
underestimation of phytoplankton primary production in tropical waters with
the standard 14C-method. A little later the same authors demonstrated that the
14C_ and OTmethods measure about the same (Gieskes and Kraay 1984). Secondly, the objects of study - the phytoplankton communities and the environments in which they exist and function - happen vary greatly in various
kinds of water basins. Therefore precise versions of 14C-methodology developed and approved for one basin can be invalid for another (Gieskes and
Kraay 1984). This holds true for all basic operations of the 14C-technique, such
as filtration procedure, duration of incubation, fixation, avoiding of 14C carbonate remains from filters, etc. For example, a firm lake phytoplankton, dominated by large diatoms and coenobial blue-green algae, sustains half-day
exposures, a weak Lugol fixation, a weak acid rinsing of filters, and small (-150ml) bottles, while these treatments could be detrimental for gentle oceanic
phytoplankton even in a temperate zone, to say nothing of tropical waters.
Therefore, I strongly advise researchers to test for themselves the feasibility
of the recommended operations. For example, on hearing warnings about the
poor quality of a working solution of radioisotopes supplied commercially -
test them by measuring zero time or the background of fixed samples. On
learning about a possible toxic effect of water bottles - test it by comparison
with a sample taken with a glass jar, for example, etc. Likewise, the researcher
may himself test the retention quality of the filters he is using, to select experimentally the optimal volume of bottles and their quality. For example, in productive waters, 150-250-ml polycarbonate commercial mineral water bottles
The Radiocarbon Method to Estimate Primary Production
2.4 Faults in the Radiocarbon Method and Problems
in its Calibration
Above, it was also mentioned that a voluminous literature exists on various
"faults" of the radiocarbon method to determine pelagic primary production
(Lean and Burnison 1979). Acquaintance with this literature and navigating
through it can leave some feeling of frustration in an inexperienced researcher.
Therefore, in conclusion to this part, it seems reasonable to present a short
review and interpretation of this literature.
The faults of the radiocarbon method can be separated into two groups:
1. those connected with the bottle effect - with the confinement of natural
assemblages of microplankton within an isolated space of experimental
bottles, and
2. special deficiencies of the radiocarbon method itself.
Before referring to the discussion, it should be mentioned that in appropriate
publications, the matter of faults in radiocarbon methodology for primary production estimation is often somewhat exaggerated, possibly because proving
its deficiency was the main goal of the publication. A typical example is a sensational publication by Gieskes et a1. (1979) about a gross (1 order of values)
underestimation of phytoplankton primary production in tropical waters with
the standard 14C-method. A little later the same authors demonstrated that the
14C_ and OTmethods measure about the same (Gieskes and Kraay 1984). Secondly, the objects of study - the phytoplankton communities and the environments in which they exist and function - happen vary greatly in various
kinds of water basins. Therefore precise versions of 14C-methodology developed and approved for one basin can be invalid for another (Gieskes and
Kraay 1984). This holds true for all basic operations of the 14C-technique, such
as filtration procedure, duration of incubation, fixation, avoiding of 14C carbonate remains from filters, etc. For example, a firm lake phytoplankton, dominated by large diatoms and coenobial blue-green algae, sustains half-day
exposures, a weak Lugol fixation, a weak acid rinsing of filters, and small (-150ml) bottles, while these treatments could be detrimental for gentle oceanic
phytoplankton even in a temperate zone, to say nothing of tropical waters.
Therefore, I strongly advise researchers to test for themselves the feasibility
of the recommended operations. For example, on hearing warnings about the
poor quality of a working solution of radioisotopes supplied commercially -
test them by measuring zero time or the background of fixed samples. On
learning about a possible toxic effect of water bottles - test it by comparison
with a sample taken with a glass jar, for example, etc. Likewise, the researcher
may himself test the retention quality of the filters he is using, to select experimentally the optimal volume of bottles and their quality. For example, in productive waters, 150-250-ml polycarbonate commercial mineral water bottles