Dear all,

As you have said the term paralic is used by French workers on coastal
lagoons to refer environments and species in transitional zones between
fresh waters and sea (mainly coastal lagoons). This term is closely related
to the term confinement defined by GUELORGET & PERTHUISOT as some kind of
gradient in "vitamins" from the open sea. We have work on this concept and
suggested some modification of its original definition: the confinement and
observed gradients in diversity and biomass in the paralic environments
from the sea or the river to the inner zones would be related with the
colonisation rates of adults and larvae. I include a brief summary
published in

PÉREZ-RUZAFA, A. & MARCOS, C., 1992. 
Colonization rates and dispersal as essential parameters in the confinement
theory to explain the structure and horizontal zonation of lagoon benthic
assemblages. 
Rapp. Comm. int. Mer Medit., 33: 100.

There is a more detailed work in

PÉREZ-RUZAFA, A. & MARCOS, C., 1993. 
La teoría del confinamiento como modelo para explicar la estructura y
zonación horizontal de las comunidades bentónicas en las lagunas costeras. 
Publ. Espec. Inst. Esp. Oceanogr., 11: 347-358.



COLONIZATION RATES AND DISPERSAL AS ESSENTIAL PARAMETERS IN THE CONFINEMENT
THEORY TO EXPLAIN THE STRUCTURE AND HORIZONTAL ZONATION OF LAGOON BENTHIC
ASSEMBLAGES.

Angel PEREZ-RUZAFA & Concepción MARCOS-DIEGO

Dpto. de Ecología. Fac. de Biología. Universidad de Murcia. Aptdo. 4021.
Murcia. Spain.

In place of parameters such as salinity, ionic composition, etc., the
confinement theory proposes renovation-rates of vital elements in marine
water as the main factor to explain the composition and structure of
benthic assemblages and the observed gradients in population-density,
biomass, specific richness, and diversity, in coastal lagoons (GUELORGET &
PERTHUISOT, 1983). 

	However, this model is not altogether free from difficulties. Data cited
in the bibliography, and the results of our work at the Mar Menor lagoon
(SE Spain) (PEREZ-RUZAFA, 1989), show that the distribution of some
communities and macrophytic meadows, like those Caulerpa prolifera, Ruppia
cirrhosa, etc., display patch-distributions, related to the nature of the
bottom, physical and chemical composition of sediments, minimum
temperatures, wave-energy or hydrodynamism, and depth, instead of
horizontal gradients. These species can inhabit zones other than those
predicted by the model of GUELORGET & PERTHUISOT (1983). Furthermore, some
assemblages, of fishes and other vagile macroinvertebrates, do not respond
to the predicted gradients, and recent colonizers show temporary gradients
in horizontal zonation.

	We propose that lagoon zonation and community structure must be considered
in terms of a new conceptual model. This includes a multifactorial approach
in which lagoon- assemblages composition is related, on the one hand, to
reproduction and growth-rates as result of adaptations and energetic costs
to physical and chemical factors, and, on the other, to the confinement
concept reinterpreted as the capability of open-sea organisms to colonize
the paralic environments. In this way, interspecific competition between
colonizers and paralic species can be one of the essential factors
determining community structure. In resolving equations of competition,
population growth-rates also include colonization or effective settlement
rates. Thus, disadvantages in competition can be compensated for if
immigration rates are high enough, so that competitive equilibrium is
permitted. This would explain the higher diversities observed near the
channels of communication with the open sea and the different patterns
shown by sessile and vagile fauna. 

REFERENCES.

GUELORGET, O. & PERTHUISOT, J.P., 1983. Le domaine paralique. Expressions
géologiques, biologiques et économiques du confinement. Travaux du
laboratoire de géologie, 16: 1-136.

PEREZ-RUZAFA, A., 1989. Estudio ecológico y bionómico de los poblamientos
bentónicos del Mar Menor (Murcia, SE de España). Tesis Doctoral.
Universidad de Murcia: 751 pp.




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