Temporal variation in the shore amphipod community in the supralittoral zone of Bizerte Lagoon (northern Tunisia)

Abstract

Seasonal variation in the structure of the amphipod community on the banks of Bizerte Lagoon was studied at Menzel Jmil (37°13′8″N 09°55′1″E) from July 2006 to June 2007. The distance between the actual sites of collection (sampling points) and the shoreline varied from 70 cm in September to 6.8 m in December. Specimens were mainly collected from under roots ofCymodocea nodosaandSuaeda maritima. In the laboratory, the specimens of Amphipoda (N = 10 645) were preserved in ethanol 70%, identified, sexed, and counted under a binocular microscope. Monthly counts varied between 553 (November) and 1240 individuals (April). Eight species of talitrids were identified, based on the specific characters of their gnathopods and pereiopods. Furthermore, the results show that the amphipod community of Bizerte Lagoon is primarily composed of 3 species,Orchestia mediterranea,Orchestia gammarellusandOrchestia montagui. The species last-mentioned represented the most frequent form in summer, whereas the other two,Orchestia mediterraneaandOrchestia gammarellus, dominated in autumn.Orchestia stephenseni,Platorchestia platensis,Talorchestia deshayesii,Talitrus saltator, andOrchestia cavimana, were also found.A subsequent analysis of various diversity parameters of the amphipod community indicated a seasonal variation in abundance, species richness, and diversity.