Conclusions d'une étude quantitative dans la biocénose des algues photophiles en Méditerranée sur les côtes de Provence (France)

Abstract

A study dealing with 283 samples, taken in the upper levels of the “etage infralittoral” on rocky substratum, reveals that there is only one biocenosis in this biotope. A quantitative survey of this biocenosis resulted in biomass values varying between 0.160 kg/m² and 2.226 kg/m² of dry organic matter, 0.094 kg/m² and 22.832 kg/m² of organic calcareous matter, 1.754 kg/m² and 29.664 kg/m² of wet weight. Even though it is not possible to calculate exactly the annual production in the photophilous seaweed biocenosis, it can be said that a great quantity of organic matter is available. Along the provencal coasts, there are practically no direct consumers of this organic matter. An essay of a quantitative definition of the “faciès” was attempted; it was, however, not possible to generalize this definition. Comparisons with results of other authors are difficult because information on rocky substrates in rare and the methods employed are, in general, different. Nevertheless, in terms of the photophilous seaweed biocenosis, the Mediterranean Sea cannot be considered poor in regard to organic production.