species in the microcosm. Aeolosoma hemprichi was eliminated, and the number of
Chlorella sp. decreased to one-third its original value at Benthiocarb concentrations
above 0.5 mg/L. In the microcosm, the concentration of benthiocarb decreased to
30% for 15 days after the addition of 1.0 mg/L. It was found that the toxicity of
Benthiocarb could be evaluated based on the behaviors of the constituent microorganisms and pesticides. Addition concentrations of benthiocarb were set to 1.0, 2.0,
4.0, and 8.0 mg/L. As the controls, only methanol-addition and methanol
no-addition systems were constructed to compare the influence of methanol as a
pesticide solvent.
Using the structural parameter, there was no difference observed in the
populations of microorganisms between the methanol-addition and no-addition
control systems. In the microcosms where 1.0–4.0 mg/L of Benthiocarb was
added, there was also no significant influence on the population; however, both
Aeolosoma hemprichi and Philodina erythrophthalma perished with the addition of
8.0 mg/L of Benthiocarb. The functional parameter and the amounts of respiration
(R) and production (P) increased with the addition of methanol, but not only was
there no observed influence on the ecosystems of the methanol-addition system and
in the case of Benthiocarb loading, but there was also no difference recognized at the
high load of 8.0 mg/L of benthiocarb. The P/R ratio did not change with the addition
of Benthiocarb (Fig. 7.11). Differences in the amounts of production and respiration
on each measurement day after the addition of Benthiocarb were not recognized as
statistically significant in comparison with either of the methanol control systems
according to the results of ANOVA. No significant difference in the P/R ratio was
recognized between the methanol-addition system and Benthiocarb-load systems,
either. With respect to the toxicity of Benthiocarb to animals, it was reported that the
LD 50 values for carp and Daphnia are 3.6 mg/L and 1.7 mg/L, respectively, but the
concentration responsible for the mortality of microanimals in the microcosm was
approximately 8.0 mg/L. However, no influence from Benthiocarb itself was
observed on the amounts of production or respiration at the concentration in which
microanimal populations became extinct.
7.3.5 Propyzamide
Propyzamide is a benzamide herbicide used for the weeding of a particularly
gramineous plant and works by obstructing the microtubular composition that is
necessary for cell division. Acetone was used as a solvent and regulated to a
concentration of 0.24% after addition to the TP medium. The addition concentration
of Propyzamide was adjusted to 0.1, 0.2, 1, 3, and 5 mg/L, and it was added on the
16th day of the stable state into the microcosm. 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, and it was evaluated from the
results of B 16–30 (days 16–30), which was the ratio of abundance and population
88
K. Murakami et al.
Chlorella sp. decreased to one-third its original value at Benthiocarb concentrations
above 0.5 mg/L. In the microcosm, the concentration of benthiocarb decreased to
30% for 15 days after the addition of 1.0 mg/L. It was found that the toxicity of
Benthiocarb could be evaluated based on the behaviors of the constituent microorganisms and pesticides. Addition concentrations of benthiocarb were set to 1.0, 2.0,
4.0, and 8.0 mg/L. As the controls, only methanol-addition and methanol
no-addition systems were constructed to compare the influence of methanol as a
pesticide solvent.
Using the structural parameter, there was no difference observed in the
populations of microorganisms between the methanol-addition and no-addition
control systems. In the microcosms where 1.0–4.0 mg/L of Benthiocarb was
added, there was also no significant influence on the population; however, both
Aeolosoma hemprichi and Philodina erythrophthalma perished with the addition of
8.0 mg/L of Benthiocarb. The functional parameter and the amounts of respiration
(R) and production (P) increased with the addition of methanol, but not only was
there no observed influence on the ecosystems of the methanol-addition system and
in the case of Benthiocarb loading, but there was also no difference recognized at the
high load of 8.0 mg/L of benthiocarb. The P/R ratio did not change with the addition
of Benthiocarb (Fig. 7.11). Differences in the amounts of production and respiration
on each measurement day after the addition of Benthiocarb were not recognized as
statistically significant in comparison with either of the methanol control systems
according to the results of ANOVA. No significant difference in the P/R ratio was
recognized between the methanol-addition system and Benthiocarb-load systems,
either. With respect to the toxicity of Benthiocarb to animals, it was reported that the
LD 50 values for carp and Daphnia are 3.6 mg/L and 1.7 mg/L, respectively, but the
concentration responsible for the mortality of microanimals in the microcosm was
approximately 8.0 mg/L. However, no influence from Benthiocarb itself was
observed on the amounts of production or respiration at the concentration in which
microanimal populations became extinct.
7.3.5 Propyzamide
Propyzamide is a benzamide herbicide used for the weeding of a particularly
gramineous plant and works by obstructing the microtubular composition that is
necessary for cell division. Acetone was used as a solvent and regulated to a
concentration of 0.24% after addition to the TP medium. The addition concentration
of Propyzamide was adjusted to 0.1, 0.2, 1, 3, and 5 mg/L, and it was added on the
16th day of the stable state into the microcosm. 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, and it was evaluated from the
results of B 16–30 (days 16–30), which was the ratio of abundance and population
88
K. Murakami et al.