microcosm. The populations of Aeolosoma hemprichi and Cyclidium glaucoma
decreased remarkably by the 30th day. The influence of MCPA was recognized as
a tendency to decrease population sizes at concentrations ranging from 0.3 to 0.4 mg/
L. Most species were observed to increase in population size with the addition of
0.2 mg/L of MCPA because a system is opposed to this for weed killer MCPA, and it
may be said that populations increased because they were active. Therefore, the
m-NOEC of the structural parameter was estimated to be 0.4 mg/L. There was no
observed difference in the functional parameters of the control and addition systems
until an addition concentration of 0.3 mg/L was reached. However, activity gradually decreased at an addition concentration of 0.4 mg/L, and the results were similar
at concentrations of more than 0.5 mg/L. While the P/R ratio of the control system
was ~1 and stable, the activity tended to increase at a concentration of 0.3 mg/L and
decrease at a concentration of 0.4 mg/L loading (Fig. 7.13). Thus, it can be estimated
that the m-NOEC of the functional parameter is 0.4 mg/L.
7.3.7 Alachlor
Alachlor is an acid amide herbicide, and it is considered to wither plants by
interrupting normal cell division at the position of new growth by synthesizing
inhibitors of very-long-chain fatty acids. On the 16th day after the start of the
microcosm culture, Alachlor was adjusted to concentrations of 0.1, 1, and 4 mg/L
and added. Evaluation of production (P) and respiration (R) in the microcosm
showed that the m-NOEC of Alachlor was present in the range of 1–4 mg/L
(Fig. 7.14).
7.3.8 3-(3,4-Dichlorophenyl)-1,1-Dimethylurea (DCMU)
3-(3,4-Dichlorophenyl)-1,1-dimethylurea (DCMU) is a typical, urea-based, photosynthesis-inhibiting herbicide. Its herbicidal action is mild, and it is used as a
(A)
(B)
1 23 4
5
6 7
9
0
2
4
6
8
10
12
0 2 4 6 8 10 12
1 2
3
4 5
6
7
8
9
10 11
12 13
14
0
2
4
6
8
10
12
0 2 4 6 8 10 12
Fig. 7.13 Time course of
P/R ratio in MCPA-added
microcosm N-system. (a)
0.3 mg/L addition. (b)
0.4 mg/L addition
7 Example Assessments of the Microcosm N-System
91
decreased remarkably by the 30th day. The influence of MCPA was recognized as
a tendency to decrease population sizes at concentrations ranging from 0.3 to 0.4 mg/
L. Most species were observed to increase in population size with the addition of
0.2 mg/L of MCPA because a system is opposed to this for weed killer MCPA, and it
may be said that populations increased because they were active. Therefore, the
m-NOEC of the structural parameter was estimated to be 0.4 mg/L. There was no
observed difference in the functional parameters of the control and addition systems
until an addition concentration of 0.3 mg/L was reached. However, activity gradually decreased at an addition concentration of 0.4 mg/L, and the results were similar
at concentrations of more than 0.5 mg/L. While the P/R ratio of the control system
was ~1 and stable, the activity tended to increase at a concentration of 0.3 mg/L and
decrease at a concentration of 0.4 mg/L loading (Fig. 7.13). Thus, it can be estimated
that the m-NOEC of the functional parameter is 0.4 mg/L.
7.3.7 Alachlor
Alachlor is an acid amide herbicide, and it is considered to wither plants by
interrupting normal cell division at the position of new growth by synthesizing
inhibitors of very-long-chain fatty acids. On the 16th day after the start of the
microcosm culture, Alachlor was adjusted to concentrations of 0.1, 1, and 4 mg/L
and added. Evaluation of production (P) and respiration (R) in the microcosm
showed that the m-NOEC of Alachlor was present in the range of 1–4 mg/L
(Fig. 7.14).
7.3.8 3-(3,4-Dichlorophenyl)-1,1-Dimethylurea (DCMU)
3-(3,4-Dichlorophenyl)-1,1-dimethylurea (DCMU) is a typical, urea-based, photosynthesis-inhibiting herbicide. Its herbicidal action is mild, and it is used as a
(A)
(B)
1 23 4
5
6 7
9
0
2
4
6
8
10
12
0 2 4 6 8 10 12
1 2
3
4 5
6
7
8
9
10 11
12 13
14
0
2
4
6
8
10
12
0 2 4 6 8 10 12
Fig. 7.13 Time course of
P/R ratio in MCPA-added
microcosm N-system. (a)
0.3 mg/L addition. (b)
0.4 mg/L addition
7 Example Assessments of the Microcosm N-System
91