Bryozoan distribution in a Messinian coral reef complex of western Algeria

In north-western Algeria, the Djebel Tzioua is an upper Miocene coral reef complex. The distribution of the associated bryozoans (59 species) reveals a zonation corresponding to an ecological succession. A small number of zoarial growth forms are observed at the base of the main bioherm, corresponding to the stabilization of a shoal by oysters and corals. It is followed by a colonization , characterised by an increase in the number of zoarial forms, with predominating massive and lamellar species, together with some erect colonies. A diversification of species belonging to various Zoarial forms then occurs at the top of the bioherm with an increase of the space available for reef dwellers. Other constructions above the bioherm and also laterally are elaborated by vermetids and serpulids bound to the coral reefs. The bryozoans associated with these secondary frame builders show a higher number of zoarial forms with a predominance of massive and encrusting species.