50
The Radiocarbon Method to Estimate Primary Production
H,m
0
~o
60
Cpd
o· 5· 10' 15'
to
I
~
I
Ks ) ,
,
I
I
Fig. 2.10. Comparison of Cpd and Ks curves, determined experimentally in the salmon
lake Dalnee (Kamchatka) at the end of August; the Cpd values were measured in
samples taken and incubated at depth, where the illumination (I) corresponded to
100% (0.2m), 50% (3m), 15% (13m), 5% (22m), and 2% of PARS (30m); K, values
were calculated by multiplication Kr x K, factors estimated for the same depths (see
text); this example demonstrates a distortion of the real photosynthesis rate curve when
sampling in dependence on the fixed illumination parameters
2.3.3.1 The Cpd Method
Estimation of the photosynthesis rate in the water column by the Cpd method
can be carried out in two ways. One is the incubation of the sets of light and
dark experimental bottles, filled with water sampled at different depths within
the euphotic zone, at the depth of their sampling (in situ). These incubations
usually continue through during the whole light day to account for the diurnal
course of illumination in the water column. Some researchers use also half
light-day incubations. This so-called in situ method is used mostly for primary
production measurements in freshwater basins or in coastal marine waters
with a shallow euphotic zone, where the procedure of immersion and exposure of numerous bottles is technically more simple than in a rough open sea,
for example. Another problem of its use in the deep sea is the high cost of the
ship's time spent for the long-term in situ exposures which are needed for this
method at each station where the primary production is being estimated. An
optimal procedure for suspension bottles in the water column as well as the
most practical way of performance for such experiments in situ are described
below (estimation of K, coefficients, see Sect. 2.3.3.2). At the end of the exposure, all the bottles are extracted from the basin. Their contents is filtered and
the radioactivity of the filters is estimated as described above (Sect. 2.3.2.6).
Then the absolute rate of photosynthesis (Cpd, mg Cm- 3 day-I) is calculated for
each of the incubation depths as described above for Cps (see Sect. 2.3.2.5).
Having thus determined Cpd values for depth intervals within the euphotic
The Radiocarbon Method to Estimate Primary Production
H,m
0
~o
60
Cpd
o· 5· 10' 15'
to
I
~
I
Ks ) ,
,
I
I
Fig. 2.10. Comparison of Cpd and Ks curves, determined experimentally in the salmon
lake Dalnee (Kamchatka) at the end of August; the Cpd values were measured in
samples taken and incubated at depth, where the illumination (I) corresponded to
100% (0.2m), 50% (3m), 15% (13m), 5% (22m), and 2% of PARS (30m); K, values
were calculated by multiplication Kr x K, factors estimated for the same depths (see
text); this example demonstrates a distortion of the real photosynthesis rate curve when
sampling in dependence on the fixed illumination parameters
2.3.3.1 The Cpd Method
Estimation of the photosynthesis rate in the water column by the Cpd method
can be carried out in two ways. One is the incubation of the sets of light and
dark experimental bottles, filled with water sampled at different depths within
the euphotic zone, at the depth of their sampling (in situ). These incubations
usually continue through during the whole light day to account for the diurnal
course of illumination in the water column. Some researchers use also half
light-day incubations. This so-called in situ method is used mostly for primary
production measurements in freshwater basins or in coastal marine waters
with a shallow euphotic zone, where the procedure of immersion and exposure of numerous bottles is technically more simple than in a rough open sea,
for example. Another problem of its use in the deep sea is the high cost of the
ship's time spent for the long-term in situ exposures which are needed for this
method at each station where the primary production is being estimated. An
optimal procedure for suspension bottles in the water column as well as the
most practical way of performance for such experiments in situ are described
below (estimation of K, coefficients, see Sect. 2.3.3.2). At the end of the exposure, all the bottles are extracted from the basin. Their contents is filtered and
the radioactivity of the filters is estimated as described above (Sect. 2.3.2.6).
Then the absolute rate of photosynthesis (Cpd, mg Cm- 3 day-I) is calculated for
each of the incubation depths as described above for Cps (see Sect. 2.3.2.5).
Having thus determined Cpd values for depth intervals within the euphotic