Identification of the Lagoon Ecosystems - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 24

have the possibility of recycling the raw material necessary to photosynthe-
sis and chemosynthesis and maximizing the efficiency of using the concen-
trated energy by the primary producers and thus, of the density of the
concentrated energy flow. In the land/seascapes, recycling of raw materials
(especially micro- and macronutrients) and maximizing the concentrated
energy flow are made possible by the functional differentiation of certain
ecosystems that are partially or totally “heterotrophic.”
• In the sequence of mechanisms for the transfer and conversion of the solar
energy that has as its support the sequence of tropho-dynamic modules and
the trophic network of any ecosystem, there is a process of concentrating
the energy from more diluted forms (low quality) into more concentrated
forms (high quality and with higher information content) ( Figure 2.7d) .
Therefore, the energy flow in an ecological system is unidirectional from
the permanent solar energy source toward the higher tropho-dynamic mod-
ules. Along this sequence, the quantity of energy decreases but its quality
increases. The same quantity of energy, but of a different form and of a
different quality, ensures different mechanical work. In this respect, from
the viewpoint of quality, the very concentrated energy existing at the level
of the third-order consumers or the energy of the fossil fuels (oil, natural
gas) has a much higher quality than diluted solar energy. 58
The concentration or quality of energy can be expressed in terms of
the amount of energy of a certain type and quality required to develop
energy of higher quality (Figure 2.7d). Odum 58 estimated that, on average,
for one kcal of energy concentrated in the biomass of primary producers,
almost 200 kcal of solar energy are required; in the biomass of herbivores
2000 kcal of solar energy are required; and in the biomass of carnivores
10,000 kcal of diluted solar energy are required. In addition, it can be
estimated that 50-100 kcal of primary producers and 5-10 kcal of herbi-
vores are required for one kcal of energy concentrated by first-order
carnivores.
• In any given ecological system the concentrated energy flow is maintained
with important energy expenses. For energy absorption and concentration,
each population in the structure of tropho-dynamic modules spends very
large quantities of the concentrated energy for its own maintenance. In
this respect, biological systems convert large quantities (>40%) of the
energy that is concentrated by the process of assimilation and biosynthesis
into heat, through respiration. The energy needed to concentrate energy
and for maintenance (or development) of spatio-temporal organization
increases from the primary producers (40-85% of gross primary produc-
tion with an average of 50%) to the third-order consumers (an average of
80% of the assimilated energy). It is very important to emphasize that,
when dealing with herbivores and carnivores, only 20-40% of the energy
assimilated is concentrated in their biomass. The rest of the energy is
spent on self-maintenance of the spatio-temporal organization and recy-
cling the macro- and microelements.