Influence of environmental factors and sessile biota on vagile epibionts: The case of amphipods in marinas across a regional scale

Marinas are highly anthropized environments, with singular ecological characteristics. In the present study the spatial variability of the amphipod assemblage associated to floating pontoons was analyzed. Moreover, the influence of environmental data and sessile biota on the amphipod assemblage structure was also assessed. Six marinas were selected along the Southern Iberian Peninsula, three in the Atlantic and three in the Mediterranean, and three floating pontoons were sampled at each marina. Fourteen amphipod species were identified, most corresponding to detritivores and generalist species. Statistical analyses considering amphipod composition and abundance did not show significant differences between the Atlantic and the Mediterranean, but there were significant differences between marinas. Copper had a significant correlation with amphipod assemblage. The sessile species Bugula neritina and Ellisolandia elongata also showed significant influence on the spatial patterns of the amphipod assemblages. Therefore, environmental conditions and sessile composition seem to simultaneously affect the spatial variability of amphipod assemblage associated to floating pontoons in marinas. Both factors are key to understanding the singularity of marinas and should be considered in order to prevent the use of a single management program in these environments.