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As for the dependence of k
0
(T
W
), the speci
c intensity of the phytoplankton
photosynthesis
first increases with the temperature changing from low to high
values, reaches in some interval of temperatures a maximum value optimal for p,
and then, with the further increase of the temperature it begins to decrease. Near the
maximum the following approximation is often used:
ln
ðh
0
Þg;
k
0
T
ðÞ
¼exp
f
T
W
T
W
;
opt
0
\
h
0
2
:
The dependence of the rate of photosynthesis on the concentration of nutrient
elements n(
, z, t) (phosphorus, silicon, nitrogen, and others), expressed in the
formula (
4.19
) by the exponential term, is, of course, more complicated. The
nutrient elements are one of the most important parts of the ecosystem, since they
regulate the energy
φ
,
ʻ
flux in the ecosystem. The nutrient elements supplies are spent
in the process of photosynthesis at a rate R
n
, usually approximated by the
expression R
n
=
fl
ʴ
ʴ
cient. The nutrient elements
supplies are replenished due to their sweeping out with the lifting of deep waters,
where their supplies are formed as a result of chemical processes of the dead
organic matter decomposition. This process is controlled by several abiotic con-
ditions which are characteristic of various climatic zones of the World Ocean. The
vertical
R
p
, where
is the proportion coef
flux of nutrient elements is determined by conditions of water mixing. In
the tropical zones, where the vertical structure of the water has a clear 3-layer
con
fl
guration with a layer where the temperature leaps suddenly (the layer of
thermocline), the vertical motion of nutrient elements is con
ned to this layer. In the
water bodies where the thermocline is located at depths 40
100 m, the upper layer
is usually poor in nutrient elements, and their input to this layer takes place only in
the zones of upwelling. In this case, the average rate of the vertical water lifting
beneath the thermocline varies within 10
-
3
-
10
-
2
cm/s, and in the zones of
upwelling (break-through of the thermocline) it can reach 0.1 cm/s.
-
4.6.2 Equations of the World Ocean Ecosystem Dynamics
The entire volume of ocean water is considered as a single biocenosis, in which the
fl
flux of organic matter produced in the surface layers and then descending to
maximum depths of the ocean is the main connecting factor. All model parameters
are assumed to be able to change as functions of place and time, and their para-
metric description is made by average characteristics (i.e., deterministic models).
Let us suppose the food bonds between trophic levels are adequately described
by the Ivlev model (i.e., the consumption of various kinds of food by the i-th trophic
level is proportional to the ef
ciency of their biomasses). Taking into account the
diagram of food bonds shown in Fig.
4.3
and the structure of the trophic pyramid of
a typical ocean ecosystem, we can consider each trophic level in detail.
Bacterioplankton b plays an important role in the trophic chains of the ocean. By
the available estimates, not less than 30 % of the bacterioplankton mass is in natural
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