Identification of the Lagoon Ecosystems - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 26

B

C 1 C 2

P P

C 3

DOC

C ′ 1

A Available

Stock

m

C ′ 2

Troposphere

D

POC

Soil
Lithosphere

Water
body

Sediments

FIGURE 2.8 A general model that may be used to identify large ecological systems and to
describe biogeochemical cycles.
A = Primary cycling system that comprises the major components of hydrogeomorphological
units (HGMU): soil/lithosphere; water body; sediment; and the troposphere. Low rate physical,
chemical, and geological processes mainly support exchanges among the components.
B = Secondary cycling system that is very dynamic and built on the trophic structure of
biocoenoses, biomes, and biosphere. Recycling rate of macro- and micro-elements by dom-
inant populations of each trophodynamic module is strongly correlated with the level of energy
expenses. Exchanges between the fast recyclable stock and less dynamic pools in the primary
cycling system have worked as very efficient buffering mechanisms for biogeochemical cycles
of all chemical elements. Human impact mainly affects the balance of such exchanges and
finally leads to the increase of available stock.
DOC = dissolved organic carbon; POC = particulate organic carbon; P p = primary producers;
C = consumers; m = microorganisms; D = detritus feeders.

sediment in the aquatic systems togeher with the troposphere have a
certain loading of chemical elements and compounds, as they function
as reservoirs, or pools of the biogeochemical cycles (Figure 2.8A).
Direct exchanges occur among the reservoirs due to physical and chem-
ical phenomena and processes (adsorption, absorption, hydrolysis, oxida-
tion-reduction, precipitation, flocculation, ion exchange, sedimentation,
wet and dry deposition, turbulence, currents, etc.) or they are mediated
by certain components or by the entire recycling network of tropho-
dynamic modules. Through these exchanges and the transport systems of
water and air masses, the biogeochemical cycles occurring at the ecosys-
tem levels (local cycles) and at the micro- and macro-landscapes and
seascapes are closely interconnected, and in fact integrated in the global
biogeochemical cycles. (See Chapter 4 for details.)