Distribution of benthic foraminifera from the southern Tyrrhenian continental shelf (South Italy)

Benthic foraminiferal assemblages in 153 surface sediment samples, collected at water depth between 6 and 195 m between Gulf of Salerno and Gulf of Policastro (Southern Tyrrhenian Sea), were analysed. Statistical analyses (Cluster and Principal Component Analysis) performed on the 37 most abundant species (> 5%) resulted in the identification of five distinct assemblages, mainly related to water depth, nature of substrate and organic matter at the sea floor. A typical infralittoral assemblage (6-28 m) on sands, sandy silt or silty sands, influenced by the river outflows, dominated by Ammonia beccarii, Eggerella scabra and Triloculina schreibersiana; a second infralittoral assemblages (13-60 m) on silt, silty sands and sandy silt with Ammonia parkinsoniana, Ammonia tepida, Adelosina longirostra and Siphonaperta aspera, not directly subject to the river inflow; a third assemblage associated with sandy bottoms and/or vegetated environments (12-195 m) (Connemarella rudis, Peneroplis pertusus, Planorbulina mediterranensis, Rosalina bradyi and Rosalina floridiana); a fourth assemblage (30-125 m) characterized by the dominance of the opportunistic species Nonionella turgida, related to silty bottoms rich in organic matter; and the widest assemblage (14-184 m), on silty clayey sediments, dominated by Bigenerina nodosaria and Bulimina aculeata. The composition, structure and the distribution of the benthic foraminiferal assemblage suggest a strong linkage between the substrate nature and quantity of organic matter supplies to the sea floor.