cultivation began (day 0); the microorganism population and amounts of respiration
and production were tracked over time. The m-NOEC of 2,4-dichlorophenol was
estimated to be 10 mg/L (Sugiura 1992).
7.9 Nutrients
7.9.1 Phosphate
An ecological impact assessment of PO 4 -P on the P/R ratio in an experimental
microcosm system was performed. 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 density (N 30 )
on the 30th day. The DO concentration was measured continuously from the 16th
day, and the P/R ratio was calculated from the amounts of production (P) and
respiration (R).
On the 16th day after microcosm cultivation began, 30 mg/L of phosphate, which
is a nutrient source for Chlorella sp. and Tolypothrix sp., was added. This is a very
high concentration in comparison with that of natural aquatic ecosystems. Phytoplankton in the microcosm performed photosynthesis and absorbed phosphate, and
the culture medium was colored a deep green. Chlorella sp. increased to 50 times
that of its original population size, and CO 2 absorption and O 2 emission increased
accordingly. Bacterial abundance increased simultaneously, whereas zooplankton,
such as Cyclidium glaucoma and Philodina erythrophthalma, became extinct, and
their corpses were observed.
7.9.2 Ammonia
The effect of ammonia was investigated and reported by Dr. Sugiura. Ammonia was
added when microcosm cultivation began (day 0), and the populations of microorganisms and amounts of respiration and production were tracked over time. The
amount of production became greater than that of the control system, but, with the
addition of ammonia, the amount of respiration was not observed to change in
comparison to the control system. The m-NOEC of ammonia calculated from the
test concentration was 0.35 mg/L (Sugiura 1992).
7 Example Assessments of the Microcosm N-System
113
and production were tracked over time. The m-NOEC of 2,4-dichlorophenol was
estimated to be 10 mg/L (Sugiura 1992).
7.9 Nutrients
7.9.1 Phosphate
An ecological impact assessment of PO 4 -P on the P/R ratio in an experimental
microcosm system was performed. 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 density (N 30 )
on the 30th day. The DO concentration was measured continuously from the 16th
day, and the P/R ratio was calculated from the amounts of production (P) and
respiration (R).
On the 16th day after microcosm cultivation began, 30 mg/L of phosphate, which
is a nutrient source for Chlorella sp. and Tolypothrix sp., was added. This is a very
high concentration in comparison with that of natural aquatic ecosystems. Phytoplankton in the microcosm performed photosynthesis and absorbed phosphate, and
the culture medium was colored a deep green. Chlorella sp. increased to 50 times
that of its original population size, and CO 2 absorption and O 2 emission increased
accordingly. Bacterial abundance increased simultaneously, whereas zooplankton,
such as Cyclidium glaucoma and Philodina erythrophthalma, became extinct, and
their corpses were observed.
7.9.2 Ammonia
The effect of ammonia was investigated and reported by Dr. Sugiura. Ammonia was
added when microcosm cultivation began (day 0), and the populations of microorganisms and amounts of respiration and production were tracked over time. The
amount of production became greater than that of the control system, but, with the
addition of ammonia, the amount of respiration was not observed to change in
comparison to the control system. The m-NOEC of ammonia calculated from the
test concentration was 0.35 mg/L (Sugiura 1992).
7 Example Assessments of the Microcosm N-System
113