RAB/83/016
RER/83/001
Field Document
February 1989

THE PARALIC REALM
GEOLOGICAL, BIOLOGICAL AND ECONOMIC EXPRESSIONS OF CONFINEMENT

Report prepared for the Mediterranean Regional Aquaculture Project

O. Guelorget and J.-P. Perthuisot

This report was prepared during the course of the project identified on the title page. The conclusions and recommendations given in the report are those considered appropriate at the time of its preparation. They may be modified in the light of further knowledge gained at subsequent stages of the project.

The designations employed and the presentation of the material in this document do not imply the expression of any opinion whatsoever on the part of the United Nations or the Food and Agriculture Organization of the United Nations concerning the legal or constitutional status of any country, territory or sea area, or concerning the delimitation of frontiers.

ABSTRACT

The paralic aquatic milieux which are situated between the marine and continental domains are extremely different as far as their size, morphology and genesis are concerned. Furthermore, the regional climatic and hydrographic conditions, along with the local hydrological patterns, induce a great variety and variability of the physical and chemical parameters and of the sedimentary deposits.

On the contrary, the biological populations are characterized by species strictly bound to that kind of milieu; their common qualitative and quantitative zonal organization is independent of salinity and/or salinity gradients, and they are relatively stable in spite of variations of the milieu. These original biological features allow the paralic milieux to be considered together as an autonomous ecological domain: it is proposed to call it the “paralic domain”

The parameter which appears largely to control the distribution of organisms and the features of living populations may be described as the time of renewal of the elements of marine origin at any given point, and is referred to as “confinement” (by comparison with the sea). A confinement scale is proposed from biological data, which essentially concerns the seaward part of the paralic domain, where thalassoid species still persist (Near paralic). Further from the sea, the Far paralic is characterized by the appearance of freshwater, or on the contrary, evaporitic associations, and changes gradually towards the continental domain.

In the light of these new ideas, it appears that, far from being marginal, the paralic domain has played an important role in the history of the biosphere and lithosphere of our planet.

Lastly, given the high organic productivity and original sedimentological features of the paralic domain, it appears that paralic basins are a considerable source of economic richness. Confinement may be in many cases the key to a rational exploitation of their economic potentialities.

FOREWORD

The work of synthesis presented here is a first stage in the combined studies of two naturalists, a biologist and a geologist working together on paralic milieux over several years. This study has led to a proposal of a new global concept of these very often little known milieux which may perhaps seem farfetched and over-ambitious. An attempt has been made to clarify all the geological, biological and economic implications, even the most audacious. In the process, many disciplines and specialities outside the authors' usual field of study have been touched upon, and it is possible that there may be errors. Further, this work is not intended to be exhaustive and is essentially the result of experience based - but not exclusively - on the study of Mediterranean lagoons. Thus other bio-geographical fields and certain milieux such as estuaries and delta channels will be mentioned in passsing, but the authors' limited experience of these environments, and bibliographic data, suggest that the pattern proposed here is applicable to them. The aim is not to impose any new dogma, but on the contrary, to stimulate new trends of thought in each speciality so that better scientific knowledge of the Paralic Domain may be acquired, and its economic value better developed.

The fortuitous meeting in Corsica in the autumn of 1978 would have been without result, and the Paralic Domain Study Group would no doubt never have been created without the financial and practical help of the Compagnie Française des Pétroles, and the presence of André Maurin to whom grateful thanks is extended at the beginning of this text. He is associated with the very “theory” of the Paralic Domain along with Guy François Frisoni whose amiable competence in the field of phytoplankton was of considerable help.

It is not possible to mention here the names of the many people who helped in the various studies which constitute the basis of this work and the authors hereby sincerely thank them all. But special appreciation is expressed to Jacquaeline Gaudin and the team at the Antenne Graphique du CNRS at the Laboratory of Geology who contributed to the organization of this work, and to Professor André Jauzein who has kindly contributed the preface to this sixteenth volume of the collection which he initiated in 1967 and which will no doubt be the last published before his departure for a well-deserved retirement.

N.B. Certain commentaries or digressions which would have been inappropriate within the body of the text have been included in Appendix 3.

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Rome, 1989

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ABSTRACT

FOREWORD

TABLE OF CONTENTS