7.15.1 Global Warming
Global warming is one of the most important environmental problems because of the
seriousness of its effects on ecosystem structure, including upon energy flow, material
circulation, and biological interactions. The Intergovernmental Panel on Climate
Change (IPCC) reported in 2007 that 40% of all wildlife species on Earth will become
extinct with a 4
C increase in global atmospheric temperatures. However, information
about the mechanisms underlying the relationship between global warming and the
succession of biological species in aquatic environments has been insufficient to
establish countermeasures, either academically or administratively. For this reason,
experimental data are of extreme importance and must be obtained rapidly and in great
abundance. We investigated the effects of temperature on microbial community
function and structure using the experimental flask-sized microcosm.
A flask-sized microcosm was cultured at 25
C under 2400 lux (12 h. L/12 h. D)
and without stirring for use as the control system. To assess the influence of
temperature, 30
C, 35
C, and 40
C were used as the high-temperature conditions
of global warming, and 10
C and 20
C were used as the low temperature conditions
of global cooling. The vessel for cultivation was a 300 mL Erlenmeyer flask, and
200 mL of Taub’s basal medium was poured; the concentration of the polypeptone
as a substrate was adjusted to 100 mg/L. Plankton observation using an optical
microscope was conducted from the start of culturing, on days 0, 2, 4, 7, 14, 16,
18, 20, 23, and 30. The kind of change observed in a flask under each temperature
condition was used as the structural parameter. Additionally, the DO concentration
was measured consecutively from the 16th day of the culture period onward to
evaluate the functioning of the ecosystems by using the P/R ratio as the functional
parameter.
In high-temperature conditions (35
C and 40
C), zooplankton consumers
disappeared, whereas all microbial species maintained coexistence at 30
C. The
no-effect temperature in the microcosm was evaluated as less than 35
C from the
viewpoint of ecosystem structure. With increases in temperature, the activity of the
system increased, and the P/R ratio was stable. However, the DO amplitude damped
with the extinction of the microcosm at 35
C. The maximum environmental
temperature to have no effect on the microcosm, judging from the functional
parameter, was evaluated to be less than 35
C. At the lowest temperature (10
C),
the consumer population of the microcosm decreased, the activity of the ecosystem
decreased, and the rate of succession slowed. It was shown that the influence of high
temperatures was particularly strong with respect to the consumers, and the entire
system eventually collapsed (Figs. 7.43 and 7.44).
156
K. Murakami et al.
Global warming is one of the most important environmental problems because of the
seriousness of its effects on ecosystem structure, including upon energy flow, material
circulation, and biological interactions. The Intergovernmental Panel on Climate
Change (IPCC) reported in 2007 that 40% of all wildlife species on Earth will become
extinct with a 4
C increase in global atmospheric temperatures. However, information
about the mechanisms underlying the relationship between global warming and the
succession of biological species in aquatic environments has been insufficient to
establish countermeasures, either academically or administratively. For this reason,
experimental data are of extreme importance and must be obtained rapidly and in great
abundance. We investigated the effects of temperature on microbial community
function and structure using the experimental flask-sized microcosm.
A flask-sized microcosm was cultured at 25
C under 2400 lux (12 h. L/12 h. D)
and without stirring for use as the control system. To assess the influence of
temperature, 30
C, 35
C, and 40
C were used as the high-temperature conditions
of global warming, and 10
C and 20
C were used as the low temperature conditions
of global cooling. The vessel for cultivation was a 300 mL Erlenmeyer flask, and
200 mL of Taub’s basal medium was poured; the concentration of the polypeptone
as a substrate was adjusted to 100 mg/L. Plankton observation using an optical
microscope was conducted from the start of culturing, on days 0, 2, 4, 7, 14, 16,
18, 20, 23, and 30. The kind of change observed in a flask under each temperature
condition was used as the structural parameter. Additionally, the DO concentration
was measured consecutively from the 16th day of the culture period onward to
evaluate the functioning of the ecosystems by using the P/R ratio as the functional
parameter.
In high-temperature conditions (35
C and 40
C), zooplankton consumers
disappeared, whereas all microbial species maintained coexistence at 30
C. The
no-effect temperature in the microcosm was evaluated as less than 35
C from the
viewpoint of ecosystem structure. With increases in temperature, the activity of the
system increased, and the P/R ratio was stable. However, the DO amplitude damped
with the extinction of the microcosm at 35
C. The maximum environmental
temperature to have no effect on the microcosm, judging from the functional
parameter, was evaluated to be less than 35
C. At the lowest temperature (10
C),
the consumer population of the microcosm decreased, the activity of the ecosystem
decreased, and the rate of succession slowed. It was shown that the influence of high
temperatures was particularly strong with respect to the consumers, and the entire
system eventually collapsed (Figs. 7.43 and 7.44).
156
K. Murakami et al.