Identification of the Lagoon Ecosystems - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 28

• Recyclable stocks of many chemical elements and compounds are usually
distributed in that compartment of HGMU that performs the most active
exchanges with the cycling compartment ( Figure 2.8) , in relatively low
concentrations. However, the density of flow between the dominant com-
ponents of the tropho-dynamic modules is increased, and more often
multiplied by hundreds and thousands of times, through the phenomena
of accumulation and concentration.
• In many cases, the concentration of certain heavy metals, radionuclides,
and chemical compounds in the main pool of the cycling system is main-
tained below safe threshold levels established by toxicity tests. However,
most of the components in the terminal tropho-dynamic modules raise the
concentration far beyond safe threshold levels. Thus, the trophic chains
directly open to human populations more often transfer significantly higher
amounts of “toxics” and expose individuals and human populations to
mutagenic effects and chronic diseases to a greater extent than expected.
Therefore, the real level of exposure and the potential toxic effects
cannot be estimated to an acceptably accurate degree unless we combine
the classical methodology based on toxicity tests with the evaluation of
the density of mass transfer along the trophic chains. Under such circum-
stances, the common procedure of discharging gaseous or liquid wastes
into the troposphere and large surface water bodies (freshwater or marine)
assuming high dilution coefficients must be seriously reconsidered.
• The recycling of the “raw material” or the macro- and microelements is
one of the key driving forces for gross primary productivity. It is carried
out by the dominant populations of the tropho-dynamic modules of an
ecological system, not only in a single functional category.
Figure 2.8B shows the main recycling mechanisms of the macro- and
microelements occurring in the aquatic and terrestrial ecological systems.
These mechanisms are provided by the dominant populations of the tropho-
dynamic modules network needing high-energy expenses. The energy
requirement may comprise up to 50 to 80% of the total energy concentrated
in the form of gross primary production or energy assimilated by the
autotrophic and heterotrophic populations. These mechanisms that are
coupled by mass and energy transfer chains make up the cycling system
functioning in any natural or semi-natural ecological system. They consist
of a sequence of coupled natural “technologies” effective in processing
the organic by-products (“wastes”) and recycling the raw materials that
are required for the maintenance or maximization of the concentrated
energy flow, as well as for the production of natural goods and services.
In contrast, in ecological systems created or dominated by the human
population, processing of the organic by-products (dissolved and partic-
ulate organic matter) and the solid organic waste is performed by tech-
nologies that are bound to a considerable input of concentrated energy,
usually in fossil fuels.
• Recent statistical data processed by various specialized institutions have
shown that more than 100,000 chemical compounds (e.g., pesticides, plastics,