Study of the Dynamics of Phosphorus
265
5.7.2.2 Estimation of the Total P04-P Uptake by Microplankton
Experimental incubations are carried out in bottles of the BOD type of not
less than 200 ml capacity to escape the bottle effects. These bottles are prepared as described above (Sect. 2.3.2.3). One such bottle is filled for each
sampled depth and one killed control bottle is filled fur all the series of
samples, taken on the vertical profile or at a cross-section. The samples
are charged with equal aliquots of working isotope solution with a 33P04_P
radioactivity of about 2-4 10 5 cpm per sample. The control sample is instantly
fixed with Lugol solution to attain a pale yellow color. The experimental
samples are incubated at simulated in situ conditions for the period of time
preselected with the aid of the time-course curve. After the incubation time
ends, the samples are instantly subjected to filtration without previous fixation,
because the killed cells of microplankton rapidly release consumed labeled
phosphate from the disintegrating ATP and polyphosphate pools. From each
sample, two to three equal 50-100-ml subsamples are filtered to have a mean,
because the filtration procedure itself causes deviations during parallel estimations. The procedure of filtration and subsequent rinsing of filters is as
described above (Sect. 5.7.2.2). The means of radioactivity found at the filters
are corrected for the killed controls and calculated per whole volume of the
sample in the bottle (Ri). The rate of P04-P uptake by microplankton (At) is
calculated as follows: A = RxP i )lgPI-Ih- l , where Pi is the absolute content
t
R t xt
of P04-P in water accounting for the carrier P04-P injected into it together
with the working solution of radioisotope, )lg PI-I, R t the radioactivity of the
aliquot of working isotope solution, which was injected into the experimental
bottles (see above); and t the incubation time, h.
To evaluate the uptake rate per day, it is necessary to measure the At
values in the light and dark bottles. Then the corresponding At values are multiplied: the one found in the light bottles per duration of daylight, and that in
the dark bottle per duration of the darkness in hours. Their sum gives the At
value per day. Then the turnover time (T) of the stock of inorganic phosphate
in natural waters also can be calculated: T = Pi, where Pi is the content of
At
P0 4 -P in water, )lgPl- 1 , and At the uptake rate of P04-P, )lgPl-1day-l.
5.7.3 Estimation of the Share of Bacterioplankton in Total P04-P
Consumption by Microplankton
The total P04-P uptake by microplankton is the sum of its uptake by
phytoplankton (Ap) and bacterioplankton (Ab): At = Ap + A b • Its uptake by
bacterioplankton can be estimated as the difference At - Ap- It is possible to
265
5.7.2.2 Estimation of the Total P04-P Uptake by Microplankton
Experimental incubations are carried out in bottles of the BOD type of not
less than 200 ml capacity to escape the bottle effects. These bottles are prepared as described above (Sect. 2.3.2.3). One such bottle is filled for each
sampled depth and one killed control bottle is filled fur all the series of
samples, taken on the vertical profile or at a cross-section. The samples
are charged with equal aliquots of working isotope solution with a 33P04_P
radioactivity of about 2-4 10 5 cpm per sample. The control sample is instantly
fixed with Lugol solution to attain a pale yellow color. The experimental
samples are incubated at simulated in situ conditions for the period of time
preselected with the aid of the time-course curve. After the incubation time
ends, the samples are instantly subjected to filtration without previous fixation,
because the killed cells of microplankton rapidly release consumed labeled
phosphate from the disintegrating ATP and polyphosphate pools. From each
sample, two to three equal 50-100-ml subsamples are filtered to have a mean,
because the filtration procedure itself causes deviations during parallel estimations. The procedure of filtration and subsequent rinsing of filters is as
described above (Sect. 5.7.2.2). The means of radioactivity found at the filters
are corrected for the killed controls and calculated per whole volume of the
sample in the bottle (Ri). The rate of P04-P uptake by microplankton (At) is
calculated as follows: A = RxP i )lgPI-Ih- l , where Pi is the absolute content
t
R t xt
of P04-P in water accounting for the carrier P04-P injected into it together
with the working solution of radioisotope, )lg PI-I, R t the radioactivity of the
aliquot of working isotope solution, which was injected into the experimental
bottles (see above); and t the incubation time, h.
To evaluate the uptake rate per day, it is necessary to measure the At
values in the light and dark bottles. Then the corresponding At values are multiplied: the one found in the light bottles per duration of daylight, and that in
the dark bottle per duration of the darkness in hours. Their sum gives the At
value per day. Then the turnover time (T) of the stock of inorganic phosphate
in natural waters also can be calculated: T = Pi, where Pi is the content of
At
P0 4 -P in water, )lgPl- 1 , and At the uptake rate of P04-P, )lgPl-1day-l.
5.7.3 Estimation of the Share of Bacterioplankton in Total P04-P
Consumption by Microplankton
The total P04-P uptake by microplankton is the sum of its uptake by
phytoplankton (Ap) and bacterioplankton (Ab): At = Ap + A b • Its uptake by
bacterioplankton can be estimated as the difference At - Ap- It is possible to