Effects of Changing Environmental Conditions on Lagoon Ecology - Coastal Lagoons: Ecosystem Processes and Modeling for Sustainable Use and Development - page 219

some of the main factors to be considered, together with other environmental parameters
(wave exposure, sediment types, oxygen level, etc.) that also play an important role in
the distribution of the species. 89,110,112,113,136 On the other hand, the old concepts of salinity
gradients 106 and confinement 108 related only to water characteristics should be changed
to a model related to the colonization rates of species (Figure 5.11). 112,113,137,138 In
restricted and leaky lagoons, high water renewal rates and low residence time
facilitate the introduction of species by means of trophic or reproductive migratory
activities in swimming stages and current drift transport in pelagic and planktonic
stages such as eggs, larvae, and juveniles. This leads to a more or less intense
horizontal gradient and a zonation of the species assemblages, from open sea to
typical lagoon communities. The penetration of much colonization inside the
lagoon depends on the mobility of the species and on the intensity of the currents
and renewal rates. After this penetration in the lagoon environment, colonizing
species must survive in the new environmental condition. Some species will be

Open sea
assemblages

Possibilities
of
colonization?

YES

LAGOON ASSEMBLAGES

Occasional visitors.
Small influence on
lagoon assemblages.

NO

Survival
capability?

Configuration of stable but
temporary populations.
Their structure and
fluctuations depend on
the colonization rates and
the longevity of
individuals.
Appearance of a gradient
of confinement.

YES

Reproductive
capability in
the lagoon?

YES Existence of

empty
niches?

NO

Appearance of
interspecific competition.
Assemblages are the
result of competition
relationships including
the growth rates
(reproduction and
immigration) of the
respective populations
and their carrying
capacities.

YES

NO

Existence of
empty
niches?

NO

Appearance of interspecific
competition.
Assemblages are the
result of competition
relationships, including
growth rates of the paralic
species populations and
the immigration rates of
allochthonous species.

YES

Configuration of a stable and
permanent assemblage.
The gradient of confinement is
temporary and disappears at
the same time as species
colonized the farthest areas
in the lagoon.

FIGURE 5.11 Conceptual model to explain the structure of lagoon benthic assemblages and
the zonation patterns and gradients observed. According to this model, the confinement would
be related with colonization rates of marine species and indirectly with water renewal rates.
(Modified from Pérez-Ruzafa, A. and Marcos, C., Rapp. Comm. Int. Mer Mediter ., 33, 100,
1992. With permission.)