Nearly the same effects and degradation were observed when LAS was added to
the scaled-up microcosm, which included the same microbiota as those in the culture
medium of the flask-sized microcosm. This microcosm was scaled up to a 10 L glass
jar (depth, 30 cm; surface area, 490 cm
2 ) containing 7 L (depth, 16 cm) of TP
medium. In this experiment, concentrations of LAS, adenosine triphosphate (ATP),
nutrients, DO, pH, oxidation reduction potential (ORP), chemical oxygen demands
(COD), dissolved organic carbon (DOC), suspended solid (SS), and chlorophyll
a (Chl.a) were also analyzed. When the initial concentration of LAS was 1.5 mg/L,
changes in the abundance of all microorganisms were the same as those in the
control system. At 2.5 mg/L, the abundance of Cyclidium glaucoma decreased for
2 days after the addition of LAS, but it slowly increased again. At 5.0 mg/L,
Cyclidium glaucoma and Tolypothrix sp. were eliminated from the system. The
abundance of Philodina erythrophthalma and Aeolosoma hemprichi decreased for
2 days after the addition of LAS, but it slowly increased again until equilibrating
with that of the control system. The abundance of bacteria was ten times higher than
that of the control on day 2 after the LAS addition. At 10 mg/L, the abundance of
Philodina erythrophthalma and Lecane sp. decreased for 2 days after LAS addition
and then slowly increased. Aeolosoma hemprichi was eliminated from the system.
The abundance of bacteria was 100 times higher than in the control on days 2–7 after
LAS addition. The effect of LAS on Chlorella sp. was not recognized in the LAS
concentrations added in this experiment. The NOEC of LAS on the population
density was less than 1.5 mg/L.
When the initial concentration of LAS was less than 2.5 mg/L, the concentration of
ATP remained the same as in the control system (Fig. 7.1). At LAS concentrations of
5.0 mg/L and 10.0 mg/L, the concentration of ATP decreased, which corresponded to
a decrease in the abundance of microorganisms, such as Cyclidium glaucoma,
Philodina erythrophthalma, and Tolypothrix sp. It was found that ATP reflected the
decrease in the population densities of the microcosm system. Evaluation on the basis
of ATP showed that the NOEC of LAS was less than 2.5 mg/L. At initial LAS
concentrations of less than 2.5 mg/L, the concentration of DO and the P/R ratio
remained the same as those in the control system. At an LAS concentration of
5.0 mg/L, the concentration of DO and the P/R ratio decreased for 4 days after the
addition of LAS, but, toward the end of the experiment, DO recovered to the same
level as in the control system. At an LAS concentration of 10.0 mg/L, the concentration of DO decreased and converged to 3.6 mg/L; the P/R ratio also decreased for
4 days from 1.1 to À5.1, but, toward the end of the experiment, it recovered to the
same level as in the control system. The NOEC of LAS was less than 2.5 mg/L when
evaluated according to the concentration of DO and the P/R ratio. No effect of LAS on
other measured parameters, such as pH, ORP, and nutrients, was observed at these
initial LAS concentrations. These results demonstrate that the effect of LAS on
microcosm population densities was simultaneously reflected by the concentrations
of ATP and DO. Moreover, it was suggested that ATP and DO were sensitive to the
changes in population densities caused by the addition of LAS and, thus, that using
these parameters can allow for precise environmental assessments to be performed.
7 Example Assessments of the Microcosm N-System
71
the scaled-up microcosm, which included the same microbiota as those in the culture
medium of the flask-sized microcosm. This microcosm was scaled up to a 10 L glass
jar (depth, 30 cm; surface area, 490 cm
2 ) containing 7 L (depth, 16 cm) of TP
medium. In this experiment, concentrations of LAS, adenosine triphosphate (ATP),
nutrients, DO, pH, oxidation reduction potential (ORP), chemical oxygen demands
(COD), dissolved organic carbon (DOC), suspended solid (SS), and chlorophyll
a (Chl.a) were also analyzed. When the initial concentration of LAS was 1.5 mg/L,
changes in the abundance of all microorganisms were the same as those in the
control system. At 2.5 mg/L, the abundance of Cyclidium glaucoma decreased for
2 days after the addition of LAS, but it slowly increased again. At 5.0 mg/L,
Cyclidium glaucoma and Tolypothrix sp. were eliminated from the system. The
abundance of Philodina erythrophthalma and Aeolosoma hemprichi decreased for
2 days after the addition of LAS, but it slowly increased again until equilibrating
with that of the control system. The abundance of bacteria was ten times higher than
that of the control on day 2 after the LAS addition. At 10 mg/L, the abundance of
Philodina erythrophthalma and Lecane sp. decreased for 2 days after LAS addition
and then slowly increased. Aeolosoma hemprichi was eliminated from the system.
The abundance of bacteria was 100 times higher than in the control on days 2–7 after
LAS addition. The effect of LAS on Chlorella sp. was not recognized in the LAS
concentrations added in this experiment. The NOEC of LAS on the population
density was less than 1.5 mg/L.
When the initial concentration of LAS was less than 2.5 mg/L, the concentration of
ATP remained the same as in the control system (Fig. 7.1). At LAS concentrations of
5.0 mg/L and 10.0 mg/L, the concentration of ATP decreased, which corresponded to
a decrease in the abundance of microorganisms, such as Cyclidium glaucoma,
Philodina erythrophthalma, and Tolypothrix sp. It was found that ATP reflected the
decrease in the population densities of the microcosm system. Evaluation on the basis
of ATP showed that the NOEC of LAS was less than 2.5 mg/L. At initial LAS
concentrations of less than 2.5 mg/L, the concentration of DO and the P/R ratio
remained the same as those in the control system. At an LAS concentration of
5.0 mg/L, the concentration of DO and the P/R ratio decreased for 4 days after the
addition of LAS, but, toward the end of the experiment, DO recovered to the same
level as in the control system. At an LAS concentration of 10.0 mg/L, the concentration of DO decreased and converged to 3.6 mg/L; the P/R ratio also decreased for
4 days from 1.1 to À5.1, but, toward the end of the experiment, it recovered to the
same level as in the control system. The NOEC of LAS was less than 2.5 mg/L when
evaluated according to the concentration of DO and the P/R ratio. No effect of LAS on
other measured parameters, such as pH, ORP, and nutrients, was observed at these
initial LAS concentrations. These results demonstrate that the effect of LAS on
microcosm population densities was simultaneously reflected by the concentrations
of ATP and DO. Moreover, it was suggested that ATP and DO were sensitive to the
changes in population densities caused by the addition of LAS and, thus, that using
these parameters can allow for precise environmental assessments to be performed.
7 Example Assessments of the Microcosm N-System
71