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of kilometers, including distinct lagoons in the same area) and local (the inside of
the lagoon) (Table 5.1).
From both structural and functional points of view, it is possible to categorize two
extreme types of lagoons, one with a stable and predictable environment and the other
with frequent physical and chemical disturbances and fluctuations
or, according to
1
Sanders,
biologically adapted lagoons and physically controlled ones, respectively.
Species strategies respond to these situations according to a continuum of life-history
strategies,
7
r
vs.
K
(
r
refers to the rate of increase in the exponential population growth
curve and
K
refers to the carrying capacity of the population in the logistic growth
model).
-strategy involves increased reproductive effort through early reproduc-
tion, small and numerous offspring with large dispersive capability, short life span,
and small body size of adults. This provides a selective advantage in unpredictable or
short-lived environments. At the other extreme,
The
r
8
-strategy species spend more energy
on maintenance structures and adaptations, in a predictable environment, than on
reproduction. Species with this kind of strategy usually are larger, long living, less
abundant, and show higher biomass/reproductive ratios.
The models used to simulate lagoons dynamics can work at different spatial
and temporal scales depending on the process considered, the grid size used, and
the quality of input data. Physical and hydrodynamic numerical models can
provide quantitative descriptions in a continuum of spatial and temporal scales
because of the linearity of many of the involved processes (
see Chapters 3
and
6 for details).
However, biological processes are complex and show nonlinear
K
TABLE 5.1
Main Sources of Variability to Explain Differences at Hierarchical Spatial
and Temporal Scales, in Coastal Lagoons
Main Source
of Spatial Variability
Main Source of
Temporal Variability
Spatial Scales
Temporal Scales
10
3
km
Biogeographical climatic
differences
>10
4
years
Global climatic change
(ecosystem level)
10
2
-10
3
km
Hydrographic features and
geomorphology of lagoons
(mainly isolation degree);
trophic status
10
1
-10
4
years
Changes in hydrographic
and geomorphological
features and trophic status
(sucessional level)
10
−
3
-10
2
km
Substrate type; confinement
gradient; hydrodynamics;
trophic status
10
0
-10
1
years
Interannual fluctuations in
populations; changes in
recruitment; colonization
of species and migrations;
predation and
competition processes
(community level)
10
−
5
-10
−
3
km
Vertical zonation; patchiness
of species distribution and
population density;
microhabitat heterogeneity
< 10
0
years
Seasonal fluctuations of
populations; predation
and competition
processes (population and
community level)
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