8
198
Use of Radioisotopic Methodology in Aquatic Microbial Ecology
to measure dark background (dark bottle) and the other to measure photosynthetic 14COZ uptake (light bottle). After sampling, all the bottles, both light
and dark, are put into black bags and placed in a black box to be transferred
to a darkened place to be charged with the isotopic solution. After being
charged with equal portions of 14C-carbonate solution, they are closed hermetically with ground glass stoppers without air bubbles. The light bottles arc
attached then to the clamps to be fixed on the rope for subsequent in situ incubation. The stoppers are covered with plastic film held in place by rubber bands
to prevent their opening during incubation. Light bottles thus prepared for
incubation are placed into the black box and transferred to the winch. Here,
the bottles are fixed to the rope at a fixed distance to each other, the black
bags are taken out, and this row of bottles is immersed as quickly as possible
to the depth necessary to cross the illuminated part of the redox zone. The
whole operation should take 2-3 min. At dusk, after incubation of a whole light
day, the bottles are extracted and fixed with a weak Lugol solution. The parallel series of dark background bottles may be incubated at the in situ temperature either in an aquarium placed inside a black box or in situ inside the
safe black bags which are attached together to the end of the rope (temperature gradient within the redox zone is insignificant). The black bags for in situ
incubations must be checked for possible light penetration.
The content of each bottle is filtered as two parallel equal subsamples
100-140ml each and two filters from each bottle are separately radioassayed.
The radioactivity of photosynthetically assimilated 14COZ is calculated as the
difference of means from the light and the dark bottles. Calculation of the photosynthesis rate thus measured is made as described for phytoplankton photosynthesis. An example of vertical profiles of bacterial photosynthesis rates
in meromictic basins is given in Fig. 4.11.
o 50 100 150
15 30 45
15 30 45
BP
10
12
14
16
14
"
"'
Fig.4.11. Vertical profiles of anoxic bacterial photosynthesis (BP, mg C m- 3 day-I) in the
water column of meromictic lakes. I Mogilnoye Lake (Gorlenko 1978). II Faro Lake.
III Belovod Lake; Hm depth, m
198
Use of Radioisotopic Methodology in Aquatic Microbial Ecology
to measure dark background (dark bottle) and the other to measure photosynthetic 14COZ uptake (light bottle). After sampling, all the bottles, both light
and dark, are put into black bags and placed in a black box to be transferred
to a darkened place to be charged with the isotopic solution. After being
charged with equal portions of 14C-carbonate solution, they are closed hermetically with ground glass stoppers without air bubbles. The light bottles arc
attached then to the clamps to be fixed on the rope for subsequent in situ incubation. The stoppers are covered with plastic film held in place by rubber bands
to prevent their opening during incubation. Light bottles thus prepared for
incubation are placed into the black box and transferred to the winch. Here,
the bottles are fixed to the rope at a fixed distance to each other, the black
bags are taken out, and this row of bottles is immersed as quickly as possible
to the depth necessary to cross the illuminated part of the redox zone. The
whole operation should take 2-3 min. At dusk, after incubation of a whole light
day, the bottles are extracted and fixed with a weak Lugol solution. The parallel series of dark background bottles may be incubated at the in situ temperature either in an aquarium placed inside a black box or in situ inside the
safe black bags which are attached together to the end of the rope (temperature gradient within the redox zone is insignificant). The black bags for in situ
incubations must be checked for possible light penetration.
The content of each bottle is filtered as two parallel equal subsamples
100-140ml each and two filters from each bottle are separately radioassayed.
The radioactivity of photosynthetically assimilated 14COZ is calculated as the
difference of means from the light and the dark bottles. Calculation of the photosynthesis rate thus measured is made as described for phytoplankton photosynthesis. An example of vertical profiles of bacterial photosynthesis rates
in meromictic basins is given in Fig. 4.11.
o 50 100 150
15 30 45
15 30 45
BP
10
12
14
16
14
"
"'
Fig.4.11. Vertical profiles of anoxic bacterial photosynthesis (BP, mg C m- 3 day-I) in the
water column of meromictic lakes. I Mogilnoye Lake (Gorlenko 1978). II Faro Lake.
III Belovod Lake; Hm depth, m