Distribution patterns of epibiotic macrobenthic foraminifera associated to coralligenous habitats of the strait of Gibraltar

Coralligenous habitats represent the main biodiversity hotspot in the Mediterranean Sea and foraminifera constitute a key element in this environment, both in terms of species richness and ecological functionality. Despite this, species composition and distribution trends of foraminiferal assemblages in most Mediterranean regions are poorly known. In this sense, the present study explores the diversity and the spatial distribution patterns (i.e. host and environmental specificity) of benthic foraminifera inhabiting coralligenous habitats of the Strait of Gibraltar. Four different dominant substrates were considered: the macroalgae Sphaerococcus coronopifolius and Rugulopteryx okamurae, the sponge Spongia lamella and the gorgonian Paramuricea clavata. Four replicate samples of each host substrate were collected by SCUBA diving at three different stations with marked differences in their Atlantic/Mediterranean influence. The whole epifaunal community was sorted and a total of 120 foraminifera specimens were collected, belonging to five genera: Cibicidoides, Elphidium, Eponides, Massilina and Poroeponides. According to the statistical analyses conducted, epibiotic foraminiferal assemblages was homogeneous across host substrates and study locations. Despite the absence of significant differences among factors in terms of abundance and species richness, certain species such as Eponides repandus or Elphidium macellum showed spatial trends related to their spatial distribution (North vs South Bay), that could be attributed to environmental fluctuations (tempertature, hydrodynamism) derived from the transition between Atlantic and Mediterranean conditions in the Strait of Gibraltar.