Abundance and diversity of amphipods (Crustacea: Peracarida) on shallow algae and seagrass in lagoonal ecosystem of the mediterranean Tunisian coast

Abstract

Background: Bizerte lagoon is a semi-enclosed marine ecosystem, where various types of human activities have been developed. To investigate the distribution and temporal variation of amphipod assemblage, monthly sampling was conducted at the Menzel Jemil site from October 2009 to September 2010. Results: A total number of 3,620 specimens were collected from floating algae and seagrass allowing the identification of 10 amphipod species. Moreover, several indices, species richness, dominance, mean density, and diversity index were estimated to characterize the amphipode assemblage. Gammarus aequicauda was the most dominant species in all seasons. In addition, the minimum and maximum values of species richness of amphipod were observed in January (3 species) and April (8 species), respectively. The mean density and species richness were negatively correlated with plant biomass. Mean Shannon index (H′) and evenness (J′) were 1.62 ± 0.34 and 0.67 ± 0.16, respectively. Non-metric multidimensional scaling (MDS) analysis based on the mean species density showed three seasonal groups of samples. Therefore, canonical correspondence analysis (CCA) made it possible to summarize the overall situation for the species, monthly sampling, and environmental parameters on a single graph. Conclusions: Thus, the temperature, turbidity, and chlorophyll a content are the most often reported factors for the distribution and structure of amphipods in the Bizerte lagoon.