Studio delle associazioni a foraminiferi epibentonici nel Mare di Ross (Antartide): nuove prospettive sulla biodiversità di ambienti profondi.

Samples for this master thesis dissertation were taken in the Eastern Ross Sea, during the XXXII Italian Expedition of the Italian Programme of Researches in Antarctica (PNRA 2017) in the framework of the ODYSSEA project, that is a multidisciplinary study to resolve the relationship between climatic and oceanic changes in West Antarctic Ice Sheet (WAIS), particularly its evolution through the Quaternary. In this framework, I focused my study on deep living benthic foraminifera which live attached on hard substrates such as hydrocorals skeleton, shells and clasts and within the sediment (0-1cm) along a bathymetric transect along-slope on the Hillary Canyon with the aim to characterize the specialized epibenthic foraminiferal taxa. Most of them are hidden species highlighting their importance for the foraminiferal biodiversity total budget: in fact, sampling of superficial sediment for the same stations has demonstrated totally different foraminiferal assemblages compared to the hard substrates, with few species in common. As a result, I interpret a general decreasing trend in the foraminiferal abundance and biodiversity along the bathymetric transect of the Hillary Canyon. However, the abundance on Hard Substrates is higher respect the superficial (0-1cm) Sediment foraminiferal species which shows also a lower biodiversity. Anyway, they have in common the general dominance of agglutinated foraminiferal species both on Hard Substrates and Sediment, allowing also to find a new genus among Monothalamous agglutinated foraminifera. Those assemblages could be shaped by the extreme features of the canyon where high bottom currents and dense shelf water cascade (DSWC), in an oligotrophic environment, create high disturbance and an unstable habitat. By attaching themselves hardly on clasts or biogenic structures, epibenthic foraminifera could face that extreme environment. The relative high presence of Hard substrates foraminiferal assemblages increases the total biodiversity budget, together with species living at interface water-sediment usually studied, thus highlighting the dominance and importance of this phylum in the deep ocean floor.