Aspects saisonniers de la fixation de l’épifaune benthique de l’étage infralittoral de l’estuaire du Saint-Laurent

Abstract

This work conducted during two seasons (May–October 1969, 1970) was designed to study the dynamic aspects of the settlement of benthic epifauna on hard substrata. The stations were distributed on a 200-km distance, the salinity gradient ranging from 15 to 27‰. Although over 60 species were identified on the plates, the analysis shows that only three of these are abundant: Polydora ciliata, Balanus balanoides, and Balanus crenatus. In general, the settlement period of the species is very short and most of the settling processes are concentrated in June, July, and August. The populations reached a peak of abundance during settlement and decreased regularly afterwards. This decrease is due mainly to intraspecific and interspecific competition for space, accumulation of sediment, and hydrodynamic factors in autumn. The marked physical seasonality of this subarctic environment, more than true biotic succession, is reflected in the development of the community: during the summer, the community is biologically accommodated, whereas in autumn and winter it is physically controlled.