because one species perished and other species maintained their populations with
decreased consumption.
7.4.6 Dinotefuran
In recent years, the neonicotinoid pesticide, Dinotefuran, has been widely used as one of
the essential pesticides, but information regarding its influence on the ecosystem
hydrosphere through drainage and river water remains lacking. Here, an environmental
impact assessment of Dinotefuran, a neonicotinoid pesticide, on microbial community
function and structure, was conducted using the experimental flask-sized microcosm. To
assess its influence, Dinotefuran was added at several concentrations on the 16th day
after microcosm cultivation began. Plankton observation using an optical microscope
was conducted on days 0, 2, 4, 7, 14, 16, 18, 20, 23, and 30 after cultivation began, and
the change observed in the populations in the flask at each addition concentration was
used as the structural parameter. Additionally, the DO concentration was measured
consecutively from the 16th day of the culture period onward to evaluate ecosystem
function, using the P/R ratio as the functional parameter.
The results based on the structural parameter revealed that the extinction of
species was not observed in all systems. A species less than 0.5 for B 16–30 (the
population ratio in the period ranging from the 16th day to the 30th day of the
experiment) was recognized at Dinotefuran concentrations of 0.25 and 1.0 mg/L. A
decrease in the population of zooplankton was observed in all addition systems from
N 30 (the abundance on the 30th day). Additionally, the population ratio of all
zooplankton was less than 0.5 at 1.0 mg/L of added Dinotefuran. For the functional
parameter, it was judged that there was no influence in all addition systems based on
statistical analyses (Fig. 7.20). The P/R ratios of all systems converged upon a
similar value as that of the control system. From these results, the m-NOEC of
Dinotefuran was assessed to be over 1.0 mg/L.
7.4.7 4-Chlorophenol
The effect of 4-Chlorophenol was investigated by Dr. Sugiura. 4-Chlorophenol was
added at the start of microcosm culturing (day 0), and the number of organisms and
amounts of respiration and production were continuously tracked. The m-NOEC of
4-Chlorophenol was estimated to be 0.15 mg/L (Sugiura 1992).
7 Example Assessments of the Microcosm N-System
101
decreased consumption.
7.4.6 Dinotefuran
In recent years, the neonicotinoid pesticide, Dinotefuran, has been widely used as one of
the essential pesticides, but information regarding its influence on the ecosystem
hydrosphere through drainage and river water remains lacking. Here, an environmental
impact assessment of Dinotefuran, a neonicotinoid pesticide, on microbial community
function and structure, was conducted using the experimental flask-sized microcosm. To
assess its influence, Dinotefuran was added at several concentrations on the 16th day
after microcosm cultivation began. Plankton observation using an optical microscope
was conducted on days 0, 2, 4, 7, 14, 16, 18, 20, 23, and 30 after cultivation began, and
the change observed in the populations in the flask at each addition concentration was
used as the structural parameter. Additionally, the DO concentration was measured
consecutively from the 16th day of the culture period onward to evaluate ecosystem
function, using the P/R ratio as the functional parameter.
The results based on the structural parameter revealed that the extinction of
species was not observed in all systems. A species less than 0.5 for B 16–30 (the
population ratio in the period ranging from the 16th day to the 30th day of the
experiment) was recognized at Dinotefuran concentrations of 0.25 and 1.0 mg/L. A
decrease in the population of zooplankton was observed in all addition systems from
N 30 (the abundance on the 30th day). Additionally, the population ratio of all
zooplankton was less than 0.5 at 1.0 mg/L of added Dinotefuran. For the functional
parameter, it was judged that there was no influence in all addition systems based on
statistical analyses (Fig. 7.20). The P/R ratios of all systems converged upon a
similar value as that of the control system. From these results, the m-NOEC of
Dinotefuran was assessed to be over 1.0 mg/L.
7.4.7 4-Chlorophenol
The effect of 4-Chlorophenol was investigated by Dr. Sugiura. 4-Chlorophenol was
added at the start of microcosm culturing (day 0), and the number of organisms and
amounts of respiration and production were continuously tracked. The m-NOEC of
4-Chlorophenol was estimated to be 0.15 mg/L (Sugiura 1992).
7 Example Assessments of the Microcosm N-System
101