7.14 Biomanipulation
Changing the fish population of bodies of water as a part of watershed management
can facilitate desirable changes in aquatic ecosystems suffering from eutrophication,
which is characterized by phytoplankton dominance, thus aiding ecosystem restoration, an application of restoration ecology. In ponds or lakes, alternative stable
conditions (i.e., one with high algal populations, little other plant life, and turbid
water) and another with low algae populations, a diverse plant population, and clear
water may exist. In addition, to prevent excess nutrients such as phosphorus and
nitrates, the removal of certain fish species adapted to turbid water may facilitate
change from one steady state to the other, through the application of dynamical
systems theory. Fish species may be removed by means of poisoning, harvesting, or
the introduction of predatory species. Since a different fish community will result
from these processes, it will affect recreational and commercial fishermen whose
cooperation is important.
Biomanipulation technology attracts attention as a method for improving the
quality of the water. Biomanipulation is a method used to introduce a creature, but
this method poses a danger by collapsing existing ecosystems. Therefore, the environmental assessment needed to perform biomanipulation is important. The experiments below were carried out to investigate the basic ecosystem impact statement with
respect to the water quality improvement from the biomanipulation. This study
performed the basic environmental assessment, which focused its attention on ecosystem function as the P/R ratio using a microcosm. The risk assessment of top-down
control and bottom-up control as a biomanipulation method on an aquatic ecosystem
was conducted using a flask-sized microcosm system and its production/respiration
ratio and succession of microbial biota, in comparison with a control system.
7.14.1 Cyclidium glaucoma (Primary Consumer
in the Microcosm N-System)
In this experiment, the microcosm was loaded with Cyclidium glaucoma, which is a
primary predator in this gnotobiotic microcosm. For on-site biomanipulation, either
the top predator or primary predator was introduced into a eutrophied ecosystem to
ablate the irregular phytoplankton growth, such as in an algal bloom. As the structural
parameter, the population of Cyclidium glaucoma decreased after the 20th day and
converged equivalently with the control on the 30th day (Fig. 7.36). As for both
microcosms, all microorganisms did not disappear from the system, and it was thought
that the predator-prey interactions between the microbe and its prey functioned. As the
functional parameter, the 10-times loaded system showed the same behavior as the
control system. However, the amplitude (activity) of the 10-times loaded system is
larger than that of the control system. The Cyclidium glaucoma-loaded system keeps
its function as an ecosystem. However, this system caused a structural change. As the
functional parameter, any P/R ratio of a loaded system becomes approximately
144
K. Murakami et al.
Changing the fish population of bodies of water as a part of watershed management
can facilitate desirable changes in aquatic ecosystems suffering from eutrophication,
which is characterized by phytoplankton dominance, thus aiding ecosystem restoration, an application of restoration ecology. In ponds or lakes, alternative stable
conditions (i.e., one with high algal populations, little other plant life, and turbid
water) and another with low algae populations, a diverse plant population, and clear
water may exist. In addition, to prevent excess nutrients such as phosphorus and
nitrates, the removal of certain fish species adapted to turbid water may facilitate
change from one steady state to the other, through the application of dynamical
systems theory. Fish species may be removed by means of poisoning, harvesting, or
the introduction of predatory species. Since a different fish community will result
from these processes, it will affect recreational and commercial fishermen whose
cooperation is important.
Biomanipulation technology attracts attention as a method for improving the
quality of the water. Biomanipulation is a method used to introduce a creature, but
this method poses a danger by collapsing existing ecosystems. Therefore, the environmental assessment needed to perform biomanipulation is important. The experiments below were carried out to investigate the basic ecosystem impact statement with
respect to the water quality improvement from the biomanipulation. This study
performed the basic environmental assessment, which focused its attention on ecosystem function as the P/R ratio using a microcosm. The risk assessment of top-down
control and bottom-up control as a biomanipulation method on an aquatic ecosystem
was conducted using a flask-sized microcosm system and its production/respiration
ratio and succession of microbial biota, in comparison with a control system.
7.14.1 Cyclidium glaucoma (Primary Consumer
in the Microcosm N-System)
In this experiment, the microcosm was loaded with Cyclidium glaucoma, which is a
primary predator in this gnotobiotic microcosm. For on-site biomanipulation, either
the top predator or primary predator was introduced into a eutrophied ecosystem to
ablate the irregular phytoplankton growth, such as in an algal bloom. As the structural
parameter, the population of Cyclidium glaucoma decreased after the 20th day and
converged equivalently with the control on the 30th day (Fig. 7.36). As for both
microcosms, all microorganisms did not disappear from the system, and it was thought
that the predator-prey interactions between the microbe and its prey functioned. As the
functional parameter, the 10-times loaded system showed the same behavior as the
control system. However, the amplitude (activity) of the 10-times loaded system is
larger than that of the control system. The Cyclidium glaucoma-loaded system keeps
its function as an ecosystem. However, this system caused a structural change. As the
functional parameter, any P/R ratio of a loaded system becomes approximately
144
K. Murakami et al.