concentration was measured continuously from the 16th day, and the P/R ratio was
calculated from the amounts of production (P) and respiration (R).
As the structural parameter, B 16–30 , the abundance 14 days after the addition of
Co, was evaluated. Microorganisms in the microcosm did not perish during the
period of acute influence, but extinction was observed during the periods of subacute
influence and chronic influence. Increases and decreases in the populations of each
microorganism were observed with Co addition, and the tendency for populations to
slightly increase in a low-concentration system was recognized in Philodina
erythrophthalma, but large decreases in population were observed in Cyclidium
glaucoma and Lecane sp. Additionally, it was revealed that many populations
decreased in the high-concentration systems from B 16–30 . It is thought that the
population ratio changed due to differences in the Co-resistance of each microbial
species. As a functional parameter, the amplitude of the DO damped in the 5 mg/L of
Co + 0.5 mg/L of Ni system, and it is thought that the system collapsed. The P/R
ratio in all systems was stable at approximately 1.
From these results, the m-NOEC of the structural parameter was estimated to be
1 mg/L of Co + 0.1 mg/L of Ni because microorganisms in the microcosm perished
at this concentration during the period of chronic influence. Meanwhile, the
m-NOEC of the functional parameter was estimated to be 5 mg/L of Co + 0.5 mg/
L of Ni because the system collapsed at concentrations higher than this from the
viewpoint of the changes in the concentration of DO. In comparison with Co-only
addition system, the m-NOEC was nearly equal, but the biomass ratio of the
zooplankton largely decreased in the low-concentration system.
7.10.11 Cs
Cesium was supplied for assessment, and a no-addition system (control) and addition
systems (0.1, 0.5, 1, and 2 mg/L) were adjusted and added as CsCl 16 days after the
start of cultivation. The endpoints were abundance (structural parameter) and the
concentration of DO (functional parameter), and the population was measured using
an optical microscope and counted from the start of culturing on days 0, 2, 4, 7, 14, 16,
18, 20, 23, and 30; it was evaluated from the results of B 16–30 (days 16–30), which was
the ratio of the abundance and population density (N 30 ) on the 30th day. The DO
concentration was measured continuously from the 16th day, and the P/R ratio was
calculated from the amounts of production (P) and respiration (R).
As a structural parameter, although a decrease was observed in the population of
the protozoan, Cyclidium glaucoma, which was the primary consumer, no major
change was observed for the entire microcosm. However, Cyclidium glaucoma
perished on the 30th day (14th day after addition) at a Cs concentration of 1 mg/L,
and an immediate decrease in the population after addition was observed at a
concentration of 2 mg/L. From this, the m-NOEC was estimated to be less than
1 mg/L for Cs. Additionally, it was thought that there was a possibility of metastasis
of the system due to Cs addition because the microanimals, such as Philodina
7 Example Assessments of the Microcosm N-System
123
calculated from the amounts of production (P) and respiration (R).
As the structural parameter, B 16–30 , the abundance 14 days after the addition of
Co, was evaluated. Microorganisms in the microcosm did not perish during the
period of acute influence, but extinction was observed during the periods of subacute
influence and chronic influence. Increases and decreases in the populations of each
microorganism were observed with Co addition, and the tendency for populations to
slightly increase in a low-concentration system was recognized in Philodina
erythrophthalma, but large decreases in population were observed in Cyclidium
glaucoma and Lecane sp. Additionally, it was revealed that many populations
decreased in the high-concentration systems from B 16–30 . It is thought that the
population ratio changed due to differences in the Co-resistance of each microbial
species. As a functional parameter, the amplitude of the DO damped in the 5 mg/L of
Co + 0.5 mg/L of Ni system, and it is thought that the system collapsed. The P/R
ratio in all systems was stable at approximately 1.
From these results, the m-NOEC of the structural parameter was estimated to be
1 mg/L of Co + 0.1 mg/L of Ni because microorganisms in the microcosm perished
at this concentration during the period of chronic influence. Meanwhile, the
m-NOEC of the functional parameter was estimated to be 5 mg/L of Co + 0.5 mg/
L of Ni because the system collapsed at concentrations higher than this from the
viewpoint of the changes in the concentration of DO. In comparison with Co-only
addition system, the m-NOEC was nearly equal, but the biomass ratio of the
zooplankton largely decreased in the low-concentration system.
7.10.11 Cs
Cesium was supplied for assessment, and a no-addition system (control) and addition
systems (0.1, 0.5, 1, and 2 mg/L) were adjusted and added as CsCl 16 days after the
start of cultivation. The endpoints were abundance (structural parameter) and the
concentration of DO (functional parameter), and the population was measured using
an optical microscope and counted from the start of culturing on days 0, 2, 4, 7, 14, 16,
18, 20, 23, and 30; it was evaluated from the results of B 16–30 (days 16–30), which was
the ratio of the abundance and population density (N 30 ) on the 30th day. The DO
concentration was measured continuously from the 16th day, and the P/R ratio was
calculated from the amounts of production (P) and respiration (R).
As a structural parameter, although a decrease was observed in the population of
the protozoan, Cyclidium glaucoma, which was the primary consumer, no major
change was observed for the entire microcosm. However, Cyclidium glaucoma
perished on the 30th day (14th day after addition) at a Cs concentration of 1 mg/L,
and an immediate decrease in the population after addition was observed at a
concentration of 2 mg/L. From this, the m-NOEC was estimated to be less than
1 mg/L for Cs. Additionally, it was thought that there was a possibility of metastasis
of the system due to Cs addition because the microanimals, such as Philodina
7 Example Assessments of the Microcosm N-System
123