Use of the Radiocarbon Method to Determine Primary Production
81
Water level
- - - b
/
Bottom
Fig. 2.22. Underwater table for overnight preservation of weed samples collected in
the evening to be used during the next morning's experiments: a storage aquarium with
perforated side walls; b plankton net cover over the aquarium; c experimental vessel
sories for water stirring or mixing, and are filled with water to a level of some
2-3 cm above the outside level of the water basin.
As was mentioned above, the photosynthesis rate, and also the rate of respiration in hydrophytes, may be dependent on the velocity of water movement. Therefore the experimental vessels should be supplied with devices for
stirring or pumping water within the enclosed systems vessel - pump - vessel.
Such devices are necessary also to mix water in the vessel after insertion of
the radioisotope working solution. For this, the plastic lid of the jar or Plexiglas vessel must have an opening with a special Teflon plug, with a hole to pass
the shaft of stirring propeller through it (Fig. 2.20). The shaft can be brought
into motion by hand if it is to be used only for mixing the water column in the
vessel after insertion of the radioisotope solution . For permanent stirring, on
the upper side of the lid air-driven magnetic stirrers (A.H. Thomas Co.) might
be also installed, operated by compressed air from the scuba tanks. Batteryoperated stirrers and peristaltic water pumps can also be used (Bittaker and
Iverson 1976; Rogers and Salesky 1981). Open cylinders or tubes employed
for in situ incubations without lids may have a stirring device fixed on to a lath
attached to the upper edge. To induce water motion in the vessels, incubated
in situ, it is also possible to use the force of waves.
Stirring is not recommended for use during all routine incubations, so that
installation of stirring accessories in all incubation vessels is not necessary. It
is sufficient to have only one, which should be used to establish the correction
coefficient to correct estimations done without stirring for this factor. For this,
parallel experiments should be carried out with measurements of photosynthetic 14C uptake rates (Reo cpm, g-l h- 1 ) in a container with and without stirring (or water pumping). When performing this kind of experiment, care is
81
Water level
- - - b
/
Bottom
Fig. 2.22. Underwater table for overnight preservation of weed samples collected in
the evening to be used during the next morning's experiments: a storage aquarium with
perforated side walls; b plankton net cover over the aquarium; c experimental vessel
sories for water stirring or mixing, and are filled with water to a level of some
2-3 cm above the outside level of the water basin.
As was mentioned above, the photosynthesis rate, and also the rate of respiration in hydrophytes, may be dependent on the velocity of water movement. Therefore the experimental vessels should be supplied with devices for
stirring or pumping water within the enclosed systems vessel - pump - vessel.
Such devices are necessary also to mix water in the vessel after insertion of
the radioisotope working solution. For this, the plastic lid of the jar or Plexiglas vessel must have an opening with a special Teflon plug, with a hole to pass
the shaft of stirring propeller through it (Fig. 2.20). The shaft can be brought
into motion by hand if it is to be used only for mixing the water column in the
vessel after insertion of the radioisotope solution . For permanent stirring, on
the upper side of the lid air-driven magnetic stirrers (A.H. Thomas Co.) might
be also installed, operated by compressed air from the scuba tanks. Batteryoperated stirrers and peristaltic water pumps can also be used (Bittaker and
Iverson 1976; Rogers and Salesky 1981). Open cylinders or tubes employed
for in situ incubations without lids may have a stirring device fixed on to a lath
attached to the upper edge. To induce water motion in the vessels, incubated
in situ, it is also possible to use the force of waves.
Stirring is not recommended for use during all routine incubations, so that
installation of stirring accessories in all incubation vessels is not necessary. It
is sufficient to have only one, which should be used to establish the correction
coefficient to correct estimations done without stirring for this factor. For this,
parallel experiments should be carried out with measurements of photosynthetic 14C uptake rates (Reo cpm, g-l h- 1 ) in a container with and without stirring (or water pumping). When performing this kind of experiment, care is