When microcosm culturing with the river water began soon after pesticide
dispersion, an increase was seen in the bacteria, as in the control system. Additionally, an increase was also seen in the abundance of the producer, Chlorella sp., as
was observed before pesticide dispersion, but the increase in Tolypothrix sp. was
controlled, and the survival of Lecane sp. and Philodina erythrophthalma was
confirmed. Cyclidium glaucoma, which predominated early in the culture of the
control system, and Aeolosoma hemprichi were not observed again. As for the
patchy structure, the formation of clusters decreased after pesticide dispersion
relative to before pesticide dispersion, and abundant, distributed Chlorella sp. was
recognized. From this, it was suggested that, after pesticide dispersion in the river
water, the species composition of the microcosm ecosystem came to be more
affected by an increase in river water volume.
9.3.6 River Water Containing Pesticides and Herbicides
River water was targeted for evaluation by the raising of a seedling box with
insecticide (Gazette granules) and a weedkiller (precutting emulsion, crushing 1 kg
of granules, Mamet SM granules) in a rice field after dispersion, before dispersion,
and with the passage of water, and it was sampled for a day. Additionally, the rice
field consisted of upper reaches, where it is thought that there is an inflow of
pesticide, areas in which it is thought that pesticide does not flow into the lower
reaches, and areas in which it is thought that there is an inflow of pesticide.
An inorganic salt solution and 5 mg/L of polypeptone Taub’s basal medium were
added to the river water, which was then filtered and sterilized. An inorganic salt
solution and 5 mg/L of polypeptone Taub’s basal medium were added to the
experimental system and Milli-Q water and then poured by 200 mL. Finally, a
TP 50 nutrient medium was used in the control system, and the microcosm was
subcultured in a TP 50 nutrient medium with a microcosm seed at 2800 lux
(L/D ¼ 12 h/12 h), 25
C, without stirring. The species composition of the microcosm did not exhibit any remarkable changes. When compared with the control
system, at the location where it was assumed that there was no inflow of pesticide, no
substantial difference was observed before and after weedkiller dispersion.
At the upper reaches of the farm, no change was observed in the abundance of
Chlorella sp., the threadlike blue-green alga, Tolypothrix sp., or in the rotifer,
Philodina erythrophthalma, in the microcosm using river water sampled on the
day when herbicidal dispersion was completed at the farm. However, a decrease
was observed in the abundance of the rotifer, Lecane sp., the oligochaete, Aeolosoma
hemprichi, and in a bacterium. Meanwhile, an increase was observed in the abundance of the protozoan, Cyclidium glaucoma. Moreover, a decrease in the abundance of Lecane sp. was remarkable, and their presence was not able to be confirmed
by the 21st day of the experiment.
At a downstream location at the farm, no change was observed in the abundance
of Chlorella sp., Tolypothrix sp., Philodina erythrophthalma, or Aeolosoma
178
Y. Inamori et al.
dispersion, an increase was seen in the bacteria, as in the control system. Additionally, an increase was also seen in the abundance of the producer, Chlorella sp., as
was observed before pesticide dispersion, but the increase in Tolypothrix sp. was
controlled, and the survival of Lecane sp. and Philodina erythrophthalma was
confirmed. Cyclidium glaucoma, which predominated early in the culture of the
control system, and Aeolosoma hemprichi were not observed again. As for the
patchy structure, the formation of clusters decreased after pesticide dispersion
relative to before pesticide dispersion, and abundant, distributed Chlorella sp. was
recognized. From this, it was suggested that, after pesticide dispersion in the river
water, the species composition of the microcosm ecosystem came to be more
affected by an increase in river water volume.
9.3.6 River Water Containing Pesticides and Herbicides
River water was targeted for evaluation by the raising of a seedling box with
insecticide (Gazette granules) and a weedkiller (precutting emulsion, crushing 1 kg
of granules, Mamet SM granules) in a rice field after dispersion, before dispersion,
and with the passage of water, and it was sampled for a day. Additionally, the rice
field consisted of upper reaches, where it is thought that there is an inflow of
pesticide, areas in which it is thought that pesticide does not flow into the lower
reaches, and areas in which it is thought that there is an inflow of pesticide.
An inorganic salt solution and 5 mg/L of polypeptone Taub’s basal medium were
added to the river water, which was then filtered and sterilized. An inorganic salt
solution and 5 mg/L of polypeptone Taub’s basal medium were added to the
experimental system and Milli-Q water and then poured by 200 mL. Finally, a
TP 50 nutrient medium was used in the control system, and the microcosm was
subcultured in a TP 50 nutrient medium with a microcosm seed at 2800 lux
(L/D ¼ 12 h/12 h), 25
C, without stirring. The species composition of the microcosm did not exhibit any remarkable changes. When compared with the control
system, at the location where it was assumed that there was no inflow of pesticide, no
substantial difference was observed before and after weedkiller dispersion.
At the upper reaches of the farm, no change was observed in the abundance of
Chlorella sp., the threadlike blue-green alga, Tolypothrix sp., or in the rotifer,
Philodina erythrophthalma, in the microcosm using river water sampled on the
day when herbicidal dispersion was completed at the farm. However, a decrease
was observed in the abundance of the rotifer, Lecane sp., the oligochaete, Aeolosoma
hemprichi, and in a bacterium. Meanwhile, an increase was observed in the abundance of the protozoan, Cyclidium glaucoma. Moreover, a decrease in the abundance of Lecane sp. was remarkable, and their presence was not able to be confirmed
by the 21st day of the experiment.
At a downstream location at the farm, no change was observed in the abundance
of Chlorella sp., Tolypothrix sp., Philodina erythrophthalma, or Aeolosoma
178
Y. Inamori et al.