cell count, while the value of each functional parameter decreased at 55 mg/L of Mn
more than in the control system. Therefore, functional parameters appear to be more
susceptible to chemical substances than to structural parameters.
When Cu was added to the microcosm N-system, the production and respiration
rates rose in a concentration-dependent manner between 0.3 and 1.2 mg/L but
declined at 1.5 mg/L. The production rate increased at 0.4–1.2 mg/L in comparison
with the control system and decreased at 1.5 mg/L. The respiration rate increased at
1.2 mg/L and 1.5 mg/L, higher than in the control system. The P/R ratio was not
clearly influenced at 1.2 mg/L or less but decreased at 1.5 mg/L more clearly than in
the control system. These effects corresponded to the risk assessment pattern “A-2”
(i.e., maintenance of the system, with no influence on the P/R ratio and wherein
organismic activity increased) at low concentrations (0.3–1.2 mg/L) and to the “D-2”
pattern (i.e., collapse of the system in which the P/R ratio decreased and did not
recover) at the high concentration (1.5 mg/L). When Cu was added to the microcosm
N-system, there was no apparent influence on the population at 0.6 mg/L or less, and
this result is similar to that in the microcosm subsystem. A decrease or increase in the
abundance of individual species was recognized in comparison with the control
system when 0.9 mg/L or 1.2 mg/L of Cu was added to the microcosm N-system, but
no species perished.
When Mn was added to the microcosm N-system, neither functional parameter
was affected, nor did they exhibit the “A-1” (i.e., maintenance of the system, with no
influence on the P/R ratio and biological activity) pattern at 0.1 mg/L. By adding
1 mg/L of Mn, the production rate was not clearly influenced, and the respiration rate
increased only temporarily after the addition of more than that of the control system.
As a result, the P/R ratio temporarily decreased after the addition of Mn to less than
that of the control system. Therefore, it can be assigned to the risk assessment pattern
“B-2” (i.e., recovery of the system in which P/R decreased and recovered). In
contrast, by loading the experiment for the microcosm subsystem, 55 mg/L and
550 mg/L of Mn was added and exhibited a “D-2” pattern (i.e., collapse of the
system in which P/R decreased and did not recover). When Mn was added to the
microcosm N-system, there was no apparent influence of the population observed at
0.1 mg/L. At 1 mg/L, some species perished, and the populations of others decreased
or increased in comparison with the control system. However, no species perished
even at 5.5 mg/L of Mn added to the microcosm subsystem, and there was little
influence on the cell count. Therefore, it was suggested that the sensitivity of
structural parameters to Mn was lower in the subsystem than in the microcosm
N-system.
It was made clear that the sensitivities of the microcosm subsystem and microcosm N-system were similar or that of the subsystem was lower in both the
functional parameter and structural parameter endpoints. However, there was a
difference in the addition concentration of loading experiments, and there remains
the problem that the loadings only accounted for two kinds of metals. For a stable
evaluation, the superiority of the biologically diverse N-system becomes clear.
11 A Subsystem Microcosm Verification of the Microcosm N-System
199
more than in the control system. Therefore, functional parameters appear to be more
susceptible to chemical substances than to structural parameters.
When Cu was added to the microcosm N-system, the production and respiration
rates rose in a concentration-dependent manner between 0.3 and 1.2 mg/L but
declined at 1.5 mg/L. The production rate increased at 0.4–1.2 mg/L in comparison
with the control system and decreased at 1.5 mg/L. The respiration rate increased at
1.2 mg/L and 1.5 mg/L, higher than in the control system. The P/R ratio was not
clearly influenced at 1.2 mg/L or less but decreased at 1.5 mg/L more clearly than in
the control system. These effects corresponded to the risk assessment pattern “A-2”
(i.e., maintenance of the system, with no influence on the P/R ratio and wherein
organismic activity increased) at low concentrations (0.3–1.2 mg/L) and to the “D-2”
pattern (i.e., collapse of the system in which the P/R ratio decreased and did not
recover) at the high concentration (1.5 mg/L). When Cu was added to the microcosm
N-system, there was no apparent influence on the population at 0.6 mg/L or less, and
this result is similar to that in the microcosm subsystem. A decrease or increase in the
abundance of individual species was recognized in comparison with the control
system when 0.9 mg/L or 1.2 mg/L of Cu was added to the microcosm N-system, but
no species perished.
When Mn was added to the microcosm N-system, neither functional parameter
was affected, nor did they exhibit the “A-1” (i.e., maintenance of the system, with no
influence on the P/R ratio and biological activity) pattern at 0.1 mg/L. By adding
1 mg/L of Mn, the production rate was not clearly influenced, and the respiration rate
increased only temporarily after the addition of more than that of the control system.
As a result, the P/R ratio temporarily decreased after the addition of Mn to less than
that of the control system. Therefore, it can be assigned to the risk assessment pattern
“B-2” (i.e., recovery of the system in which P/R decreased and recovered). In
contrast, by loading the experiment for the microcosm subsystem, 55 mg/L and
550 mg/L of Mn was added and exhibited a “D-2” pattern (i.e., collapse of the
system in which P/R decreased and did not recover). When Mn was added to the
microcosm N-system, there was no apparent influence of the population observed at
0.1 mg/L. At 1 mg/L, some species perished, and the populations of others decreased
or increased in comparison with the control system. However, no species perished
even at 5.5 mg/L of Mn added to the microcosm subsystem, and there was little
influence on the cell count. Therefore, it was suggested that the sensitivity of
structural parameters to Mn was lower in the subsystem than in the microcosm
N-system.
It was made clear that the sensitivities of the microcosm subsystem and microcosm N-system were similar or that of the subsystem was lower in both the
functional parameter and structural parameter endpoints. However, there was a
difference in the addition concentration of loading experiments, and there remains
the problem that the loadings only accounted for two kinds of metals. For a stable
evaluation, the superiority of the biologically diverse N-system becomes clear.
11 A Subsystem Microcosm Verification of the Microcosm N-System
199