7.10.7 Ca
An ecosystem impact assessment of Ca was conducted using both the P/R ratio as
the functional parameter and the microbiota as the structural parameter in the
microcosm. The environmental impacts and ecological risks of these materials
were estimated from comparison with the no-addition system (control) in both
assessment methods. The succession pattern of the P/R ratio during the period that
began from the day Ca was added and lasted until the final day of microcosm
cultivation was compared with that of the control system. The results showed that
the P rate was more strongly affected at a 5.0 mg/L concentration of Ca in comparison with the R rate (i.e., the P rate decreased from 1.1 mg/day on the 16th day to
0.6 mg/day on the 21st day (maximum) and recovered to ~1.0 mg/day by the 24th
day). Meanwhile, the R rate increased from 0.9 mg/day on the 16th day to 2.1 mg/
day on the 18th day (maximum) and recovered to ~1.2 mg/day by the 23rd day. The
P/R ratio temporarily decreased from 1.2 to 0.4, and, after that, it recovered to ~1 by
the 23rd day. The microcosm was considered to be influenced by Ca concentrations
of 5.0 mg/L and 10.0 mg/L in this study. According to the results of statistical
analysis, there was a significant difference among the systems with 5.0 mg/L and
10.0 mg/L of added Ca and the control ( p < 0.05). With the P/R ratio as the
functional parameter, the 5.0 mg/L concentration of Ca was considered toxic,
although not chronically. From an estimation of the succession pattern of microorganisms as the structural parameter, Cyclidium glaucoma and Lecane sp. were
greatly influenced by the addition of 5.0 mg/L of Ca, and these two species
decreased in their abundance with the addition of 5.0 mg/L of Ca, but other
microanimals, such as the rotifer, Philodina erythrophthalma, decreased in comparison with the control microcosm. From an estimation of N 30 at a concentration of
5.0 mg/L of Ca, the microorganisms were divided into two groups, those of
increasing abundance and decreasing abundance. The former group contained bacteria as the decomposers, and the latter contained protozoans and metazoans as the
consumers. Algae, as the producers, were divided into two groups; the abundance of
the chlorophyceans, Chlorella sp. and Scenedesmus quadricauda, decreased, and
the abundance of cyanophycean, Tolypothrix sp., increased. This phenomenon was
caused by the growth inhibition of microanimals, especially Aeolosoma hemprichi,
by the sudden increase in pH (from 8.2 to 11.1 just after the addition of 5.0 mg/L of
Ca) and the photosynthetic inhibition of microalgae, especially Chlorella sp. and
Scenedesmus quadricauda, by the light inhibition of Ca. The oligochaete,
Aeolosoma hemprichi, has a strong jaw for eating and destroying flocs contained
in bacteria, algae, other organisms, and detritus (Inamori et al. 1990). It was thought
that Aeolosoma hemprichi was damaged in its physiological activity by the increase
in pH; subsequently, Tolypothrix sp. escaped from the predation by Aeolosoma
hemprichi. Under microscopic observation, it was confirmed that Aeolosoma
hemprichi predated flocs in Tolypothrix sp., bacteria, and detritus in the control
microcosm. The coefficients of variation (standard deviation/mean, expressed as
percentages) for the abundance of each microorganism in the microcosm during the
7 Example Assessments of the Microcosm N-System
119
An ecosystem impact assessment of Ca was conducted using both the P/R ratio as
the functional parameter and the microbiota as the structural parameter in the
microcosm. The environmental impacts and ecological risks of these materials
were estimated from comparison with the no-addition system (control) in both
assessment methods. The succession pattern of the P/R ratio during the period that
began from the day Ca was added and lasted until the final day of microcosm
cultivation was compared with that of the control system. The results showed that
the P rate was more strongly affected at a 5.0 mg/L concentration of Ca in comparison with the R rate (i.e., the P rate decreased from 1.1 mg/day on the 16th day to
0.6 mg/day on the 21st day (maximum) and recovered to ~1.0 mg/day by the 24th
day). Meanwhile, the R rate increased from 0.9 mg/day on the 16th day to 2.1 mg/
day on the 18th day (maximum) and recovered to ~1.2 mg/day by the 23rd day. The
P/R ratio temporarily decreased from 1.2 to 0.4, and, after that, it recovered to ~1 by
the 23rd day. The microcosm was considered to be influenced by Ca concentrations
of 5.0 mg/L and 10.0 mg/L in this study. According to the results of statistical
analysis, there was a significant difference among the systems with 5.0 mg/L and
10.0 mg/L of added Ca and the control ( p < 0.05). With the P/R ratio as the
functional parameter, the 5.0 mg/L concentration of Ca was considered toxic,
although not chronically. From an estimation of the succession pattern of microorganisms as the structural parameter, Cyclidium glaucoma and Lecane sp. were
greatly influenced by the addition of 5.0 mg/L of Ca, and these two species
decreased in their abundance with the addition of 5.0 mg/L of Ca, but other
microanimals, such as the rotifer, Philodina erythrophthalma, decreased in comparison with the control microcosm. From an estimation of N 30 at a concentration of
5.0 mg/L of Ca, the microorganisms were divided into two groups, those of
increasing abundance and decreasing abundance. The former group contained bacteria as the decomposers, and the latter contained protozoans and metazoans as the
consumers. Algae, as the producers, were divided into two groups; the abundance of
the chlorophyceans, Chlorella sp. and Scenedesmus quadricauda, decreased, and
the abundance of cyanophycean, Tolypothrix sp., increased. This phenomenon was
caused by the growth inhibition of microanimals, especially Aeolosoma hemprichi,
by the sudden increase in pH (from 8.2 to 11.1 just after the addition of 5.0 mg/L of
Ca) and the photosynthetic inhibition of microalgae, especially Chlorella sp. and
Scenedesmus quadricauda, by the light inhibition of Ca. The oligochaete,
Aeolosoma hemprichi, has a strong jaw for eating and destroying flocs contained
in bacteria, algae, other organisms, and detritus (Inamori et al. 1990). It was thought
that Aeolosoma hemprichi was damaged in its physiological activity by the increase
in pH; subsequently, Tolypothrix sp. escaped from the predation by Aeolosoma
hemprichi. Under microscopic observation, it was confirmed that Aeolosoma
hemprichi predated flocs in Tolypothrix sp., bacteria, and detritus in the control
microcosm. The coefficients of variation (standard deviation/mean, expressed as
percentages) for the abundance of each microorganism in the microcosm during the
7 Example Assessments of the Microcosm N-System
119