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and how long it takes to overcome the initial shortage of oxygen in the case of
B
14
(
, z, t
0
) = 16 mg/m
3
.ForB
14
(
, z, t
0
) < 16 mg/m
3
φ
,
ʻ
φ
,
ʻ
the PCE is unable to
proceed to the stationary regime of functioning.
The PCEM is observed to be even more sensitive to a dynamic effect on the
process of water saturation with oxygen. This clearly follows from the behaviour of J
(t) in Fig.
4.13
. A reduction of the oxygen production by 10 % does not in
fl
uence the
PCE dynamics. A subsequent decrease of
ʴ
14
in Eq. (
4.47
) leads up to the dis-
placement in the stable state of the PCE. The PCE does not survive when the
parameter
ʴ
14
is decreased by 22 %. Figure
4.11
illustrates the important qualitative
result when Eq. (
4.50
) gives a possibility for the search of the dangerous zones in
.
Table
4.5
gives the results obtained in computing the PCE dynamics in the case
of a variation of the concentration of nutrients at the initial moment of time t
0
and at
the depth z > 150 m. From the comparison of the results contained herein it follows
that a variation of the nutrient concentration within a wide range at the moment
t=t
0
does not practically affect the behaviour of the system at the moments t >> t
0
.
The system
ʩ
'
health
'
with time from the
'
blows
'
it has suffered and proceeds to the
same functioning level.
It is different when at depths z > 150 m B
12
becomes close or inferior to a certain
value B
12,min
. In this case, the system is unable to make up for the introduced
fl
fluctuations and at B
12
>> 0.1 mg/m
3
the system begins to experience the effect of
strong limitation throughout the area. Such a reduction in the nutrient concentration
is, for instance, possible in the case of contamination of bottom sediments with oil
products.
The effect of variations in the velocity of vertical advection plays an important
role in the PCE evolution. To estimate turbulent escape of nutrients into layers
overlying the thermocline, it is assumed that the velocity of water uprise is equal to
10
-
3
cm/s in the PCEM. The obtained data point to the fact that, on the average, the
integrated pattern of the distribution of community elements is not subject to any
signi
10
−
4
to 10
−
2
and even
10
−
1
cm/s, but is observed that it is drastically distorted under a higher. Slow water
lifting (<10
−
4
cm/s) results the ecosystem extinction.
The simulation experiments enable us to answer the question about securing an
increase in the productivity of the PCE through the creation of arti
cant variations within the velocity range from 3
×
cial upwellings.
For the PCE this can be achieved within up to 40 %. In the open ocean the higher
velocity of vertical advection improves, on the one hand, nutrients supply for surface-
adjoining waters and, on the other it brings down the water temperature, thereby
drastically restricting the productivity of the system. Moreover, on account of the
lengthy trophic chain in the open ocean, the ultimate effect of increased nutrients
saturation proves to be insigni
cant. In the shelf zone the nutrients limitation is absent.
In terms of the GIMS, the PCEM can be considered as one step to the hierar-
chical biosphere model. The PCEM proposed herein is based on the experience of
preceding investigations. The choice of the composition of the system mainly
re
ects the concepts of the trophic and physiochemical nature of links between the
components of the PCE, as are maintained by marine ecologists. In contrast to the
earlier proposed models of marine and oceanic ecosystems,
fl
the PCEM is
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