2.1.2 Culture Vessel
Constructing optimum culture conditions is necessary for generating a standardized
microcosm. Specifically, the following must be optimized: (i) the movement of the
experimental water body, (ii) the wall effects, (iii) species composition and abundance, and (iv) light and temperature conditions. To ensure an optimum microcosm
cultivation volume, an 18 mL test tube and 100 mL, 300 mL, 500 mL, and 1000 mL
Erlenmeyer flasks were used for investigation.
In culture vessels of any volume, all microorganisms in the microcosm transited
the same growth curve, and no difference was observed among any of the culture
vessels. The numbers (N) of each microorganism in the steady state were approximately as follows: 100 N/mL of Cyclidium glaucoma, 30 N/mL of Lecane sp., 40 N/
mL of Philodina erythrophthalma, and 10 N/mL of Aeolosoma hemprichi. This
indicates that the volume of the microcosm, ranging from 18 mL to 1000 mL, does
not affect the succession of microbiota for the purposes of conducting the microcosm
test. Although there is no influence on the succession of microbiota, a 300 mL
Erlenmeyer flask is appropriate from the standpoints of handling, cultivation space,
and sampling of the microorganisms.
2.1.3 Stirring
The effect of stirring on the stability of the microcosm was investigated. The
microbiota in the microcosm was divided into two groups, influenced species and
uninfluenced species, in the succession period. Specifically, the blue-green alga,
Tolypothrix sp., grew in a fragmentary manner when stirred. However, there was no
difference in the microbiota between the stirred microcosm and static microcosm by
the 16th day after cultivation began. This indicates that stirring, as an outside factor,
disturbs the stability of the microcosm during the succession period but has no affect
in the stable period. In the microcosm, which is used as a model of natural
ecosystems, spatial inhomogeneity is important as an ecological characteristic.
Although some differences were observed in the growth patterns of certain
microbiota, a stable system could be obtained under both stirring and static
conditions.
2.1.4 Temperature
Culture temperatures were set to 10, 20, 25, and 30 degrees Celsius (
C), and the
growth patterns of microorganisms in the microcosm were observed. The effect of
temperature on microorganism growth was conspicuous, and the speed of succession
2 Standardization of the Microcosm N-System
13
Constructing optimum culture conditions is necessary for generating a standardized
microcosm. Specifically, the following must be optimized: (i) the movement of the
experimental water body, (ii) the wall effects, (iii) species composition and abundance, and (iv) light and temperature conditions. To ensure an optimum microcosm
cultivation volume, an 18 mL test tube and 100 mL, 300 mL, 500 mL, and 1000 mL
Erlenmeyer flasks were used for investigation.
In culture vessels of any volume, all microorganisms in the microcosm transited
the same growth curve, and no difference was observed among any of the culture
vessels. The numbers (N) of each microorganism in the steady state were approximately as follows: 100 N/mL of Cyclidium glaucoma, 30 N/mL of Lecane sp., 40 N/
mL of Philodina erythrophthalma, and 10 N/mL of Aeolosoma hemprichi. This
indicates that the volume of the microcosm, ranging from 18 mL to 1000 mL, does
not affect the succession of microbiota for the purposes of conducting the microcosm
test. Although there is no influence on the succession of microbiota, a 300 mL
Erlenmeyer flask is appropriate from the standpoints of handling, cultivation space,
and sampling of the microorganisms.
2.1.3 Stirring
The effect of stirring on the stability of the microcosm was investigated. The
microbiota in the microcosm was divided into two groups, influenced species and
uninfluenced species, in the succession period. Specifically, the blue-green alga,
Tolypothrix sp., grew in a fragmentary manner when stirred. However, there was no
difference in the microbiota between the stirred microcosm and static microcosm by
the 16th day after cultivation began. This indicates that stirring, as an outside factor,
disturbs the stability of the microcosm during the succession period but has no affect
in the stable period. In the microcosm, which is used as a model of natural
ecosystems, spatial inhomogeneity is important as an ecological characteristic.
Although some differences were observed in the growth patterns of certain
microbiota, a stable system could be obtained under both stirring and static
conditions.
2.1.4 Temperature
Culture temperatures were set to 10, 20, 25, and 30 degrees Celsius (
C), and the
growth patterns of microorganisms in the microcosm were observed. The effect of
temperature on microorganism growth was conspicuous, and the speed of succession
2 Standardization of the Microcosm N-System
13