were assessed, there was a risk for LAS ¼ 10 mg/L. Plasticity was required, but it
was made clear that the NOEC of the LAS estimated was less than 5 mg/L.
10.2.2 AE
A scaled-up microcosm as a model aquatic ecosystem, including aquatic animals and
plants, which was nearer to the conditions of a real ecosystem than was the
microcosm N-system was constructed, and the ecosystem risk posed by a nonionic
surfactant, alcohol ethoxylate (AE), as a chemical substance was assessed. As a
result of examining the appropriate combination of large aquatic animals and plants,
a stable, large-scale model ecosystem was constructed as the ecological impact
assessment system in which Rhodeus ocellatus and Rhinogobius sp. (aquatic fish)
and Egeria densa (a submerged plant) coexisted as consumers and a producer, and
the P/R ratio was approximately constant at 1. Additionally, it may be useful to
construct a stable ecosystem index using the P/R ratio. The NOEC of AE in this
scaled-up aquatic microcosm was estimated as 2 mg/L. As a result of AE addition to
the scaled-up microcosm, aquatic animals were not affected up to 2 mg/L of AE, and
the submerged plant was not affected up to 5 mg/L of AE. The influence of AE was
felt in the scaled-up microcosm at additions of 3–5 mg/L, and the P/R ratio increased
above 1, exhibiting similar behavior to the system that included submerged
plants only.
Using consecutive measurements of the DO in the scaled-up microcosm, ecological balance and a steady state can be informed, and the persistence of aquatic
populations can be judged. An activity state can be quickly derived from the
changing pattern (inspection of the recovery accuracy) of the DO level or the P/R
ratio. The possibility of evaluating ecological risk from the DO pattern and the P/R
ratio, without measuring the population of the aquatic organisms and using a
continual measurement of DO, was illustrated. The NOEC of this scaled-up microcosm was nearly equal to the m-NOEC of the N-system, which was correlated with
the flask microcosm test as shown in Fig. 10.4. This indicates that, even if the
diversity and hierarchical structure of the organisms change, there is no substantial
difference in the influence concentration. More specifically, the validity and effectiveness of the microcosm N-system was demonstrated by the experimental results
of the scaled-up microcosm system (Fig. 10.4).
10.3 Comparison with the Microcosm N-System
In the reports of Sugiura (Sugiura 2009, 2010), it was presumed that, in a microcosm
where the production and respiration can be balanced, even if the diversity of the
constituent species and the hierarchical structure are changed somewhat, there is no
substantial difference in the influence of the concentration. The correspondence
10 A Scaled-Up Model Ecosystem Verification of the Microcosm N-System
191
was made clear that the NOEC of the LAS estimated was less than 5 mg/L.
10.2.2 AE
A scaled-up microcosm as a model aquatic ecosystem, including aquatic animals and
plants, which was nearer to the conditions of a real ecosystem than was the
microcosm N-system was constructed, and the ecosystem risk posed by a nonionic
surfactant, alcohol ethoxylate (AE), as a chemical substance was assessed. As a
result of examining the appropriate combination of large aquatic animals and plants,
a stable, large-scale model ecosystem was constructed as the ecological impact
assessment system in which Rhodeus ocellatus and Rhinogobius sp. (aquatic fish)
and Egeria densa (a submerged plant) coexisted as consumers and a producer, and
the P/R ratio was approximately constant at 1. Additionally, it may be useful to
construct a stable ecosystem index using the P/R ratio. The NOEC of AE in this
scaled-up aquatic microcosm was estimated as 2 mg/L. As a result of AE addition to
the scaled-up microcosm, aquatic animals were not affected up to 2 mg/L of AE, and
the submerged plant was not affected up to 5 mg/L of AE. The influence of AE was
felt in the scaled-up microcosm at additions of 3–5 mg/L, and the P/R ratio increased
above 1, exhibiting similar behavior to the system that included submerged
plants only.
Using consecutive measurements of the DO in the scaled-up microcosm, ecological balance and a steady state can be informed, and the persistence of aquatic
populations can be judged. An activity state can be quickly derived from the
changing pattern (inspection of the recovery accuracy) of the DO level or the P/R
ratio. The possibility of evaluating ecological risk from the DO pattern and the P/R
ratio, without measuring the population of the aquatic organisms and using a
continual measurement of DO, was illustrated. The NOEC of this scaled-up microcosm was nearly equal to the m-NOEC of the N-system, which was correlated with
the flask microcosm test as shown in Fig. 10.4. This indicates that, even if the
diversity and hierarchical structure of the organisms change, there is no substantial
difference in the influence concentration. More specifically, the validity and effectiveness of the microcosm N-system was demonstrated by the experimental results
of the scaled-up microcosm system (Fig. 10.4).
10.3 Comparison with the Microcosm N-System
In the reports of Sugiura (Sugiura 2009, 2010), it was presumed that, in a microcosm
where the production and respiration can be balanced, even if the diversity of the
constituent species and the hierarchical structure are changed somewhat, there is no
substantial difference in the influence of the concentration. The correspondence
10 A Scaled-Up Model Ecosystem Verification of the Microcosm N-System
191