are composed of at least four bacterial species normally observed in natural ecosystems as decomposers, including Pseudomonas putida, Bacillus cereus,
Acinetobacter sp., and coryneform bacteria. The consumers include a protozoan
ciliate (Cyclidium glaucoma), metazoan rotifers (Philodina erythrophthalma and
Lecane sp.), and a metazoan oligochaete (Aeolosoma hemprichi), and the producers
include green algae (Chlorella sp. and Scenedesmus quadricauda) and filamentous
cyanobacteria (Tolypothrix sp.). These microcosms are considered highly reproducible and stable aquatic model ecosystems. When the microcosms are transferred to a
new medium during their stable phase, similar proliferation curves are observed,
and, once the system reaches a steady state, it will endure for an extended period of
time with the same amount of biomass. Therefore, unlike model ecosystems
(mesocosms) established from environmental water, this microcosm will not result
in the loss of species—the producers, consumers, and decomposers that constitute an
ecosystem—and their impact can be properly assessed from the perspectives of
function and structure. Thus, this microcosm is an abstract model ecosystem
consisting of producers, consumers, and decomposers. Additionally, it has been
demonstrated that the system still endures even if a small fish, such as a guppy
(Poecilia reticulata), is introduced as a high-level predator. Moreover, despite
variations in the number of days required to reach a steady state, this microcosm
developed into systems with similar species compositions and similar amounts of
biomass at various culture temperatures, ranging from 10, 20, 25, and 30
C. For this
reason, using microcosms with differing culture temperatures allows researchers to
evaluate the effects of variations in water temperature on ecosystems. Furthermore,
with regard to the effects of cesium radiation on ecosystems, in our joint research
with the National Institute of Radiological Sciences (NIRS), Japan, we have reported
the novel finding that bacteria, algae, protozoans, and metazoans that underlie the
food chain are not affected by even high doses of cesium, which supports the
feasibility of assessing the impact of different chemical substances.
As discussed above, the microcosm, with its high reproducibility and stability,
allows for different approaches in assessing ecosystems from a functional perspective. When viewed as a standardized model for multi-species testing of the impacts
of chemical substances and microorganisms on an ecosystem, it is a very effective
model. Additionally, it holds a great value as an ecosystem impact test that assesses
the effects of chemical substances and microorganisms on the stability of a system in
which material cycles and energy flows exist, which are the foundations of any
ecosystem (Fig. 1.1).
1.3 Purpose
The aim of the testing method presented in this book is to perform an aquatic
ecosystem risk assessment using a microcosm. Various interactions in the ecosystem
were exposed to a chemical substance, which served as a pollutant, and these are
shown in Fig. 1.2. The microcosm is a model ecosystem that simulates, at a reduced
4
Y. Inamori and R. Inamori
Acinetobacter sp., and coryneform bacteria. The consumers include a protozoan
ciliate (Cyclidium glaucoma), metazoan rotifers (Philodina erythrophthalma and
Lecane sp.), and a metazoan oligochaete (Aeolosoma hemprichi), and the producers
include green algae (Chlorella sp. and Scenedesmus quadricauda) and filamentous
cyanobacteria (Tolypothrix sp.). These microcosms are considered highly reproducible and stable aquatic model ecosystems. When the microcosms are transferred to a
new medium during their stable phase, similar proliferation curves are observed,
and, once the system reaches a steady state, it will endure for an extended period of
time with the same amount of biomass. Therefore, unlike model ecosystems
(mesocosms) established from environmental water, this microcosm will not result
in the loss of species—the producers, consumers, and decomposers that constitute an
ecosystem—and their impact can be properly assessed from the perspectives of
function and structure. Thus, this microcosm is an abstract model ecosystem
consisting of producers, consumers, and decomposers. Additionally, it has been
demonstrated that the system still endures even if a small fish, such as a guppy
(Poecilia reticulata), is introduced as a high-level predator. Moreover, despite
variations in the number of days required to reach a steady state, this microcosm
developed into systems with similar species compositions and similar amounts of
biomass at various culture temperatures, ranging from 10, 20, 25, and 30
C. For this
reason, using microcosms with differing culture temperatures allows researchers to
evaluate the effects of variations in water temperature on ecosystems. Furthermore,
with regard to the effects of cesium radiation on ecosystems, in our joint research
with the National Institute of Radiological Sciences (NIRS), Japan, we have reported
the novel finding that bacteria, algae, protozoans, and metazoans that underlie the
food chain are not affected by even high doses of cesium, which supports the
feasibility of assessing the impact of different chemical substances.
As discussed above, the microcosm, with its high reproducibility and stability,
allows for different approaches in assessing ecosystems from a functional perspective. When viewed as a standardized model for multi-species testing of the impacts
of chemical substances and microorganisms on an ecosystem, it is a very effective
model. Additionally, it holds a great value as an ecosystem impact test that assesses
the effects of chemical substances and microorganisms on the stability of a system in
which material cycles and energy flows exist, which are the foundations of any
ecosystem (Fig. 1.1).
1.3 Purpose
The aim of the testing method presented in this book is to perform an aquatic
ecosystem risk assessment using a microcosm. Various interactions in the ecosystem
were exposed to a chemical substance, which served as a pollutant, and these are
shown in Fig. 1.2. The microcosm is a model ecosystem that simulates, at a reduced
4
Y. Inamori and R. Inamori