The fouling community at Algeciras Bay exhibits the general features of other warm-temperate fouling communities in which the bryozoan Bugula neritina is a major competitor for space during summer. This bryozoan was sampled in order to study spatio-temporal changes of the peracaridan fauna of Algeciras Bay (Strait of Gibraltar). The results of this work point out the relevance of studying the life cycle patterns of both the living substratum and its associated fauna prior to analyzing the possible classification or ordination of the stations. There was a good correlation between the height of B. neritina and temperature and between the colony dry mass and the number of peracaridan individuals.

Numerical analyses allowed the identification of two groups of stations based on the distribution and abundance of the peracaridan faunas in Algeciras Bay, the internal and the external stations. The external stations had higher diversity, regarding both evenness and species richness, than in the internal stations, where some species, e.g., Jassa marmorata, Phtisica marina, Ischyrocerus inexpectatus, were strongly dominant. Seasonal variation of the substratum, Bugula neritina, and the peracaridan fauna which lives on it minimized the differences between external and internal stations. The ability to utilize B. neritina as living space can be a key to the success of some peracaridan species such as Jassa marmorata, Ischyrocerus inexpectatus, and Podocerus variegatus. Moreover, the temporal and spatial offset in the maximal density shown by some amphipod species might indicate the existence of biological relationships such as competition or predation.