Foraminiferal assemblage over the last 2000 years in Edisto Inlet (Ross Sea, Victoria Land Coast, Antarctica) and their palaeoenvironmental significance

The marine sediment core TR17 08 (14.6m), was collected in Edisto Inlet (Ross Sea, Antarctica) during the 2017 Italian oceanographic campaign. The core is composed by laminated sedimentary sequences, making it suitable for studying submillennial processes. We focused on nine common Foraminifera species from the Southern Ocean, both benthic and planktonic. By the comparison between other proxies retrieved from nearby sediment cores (Fig. 6), we were able to distinguish three different environmental phases over the last 2000 yrs (6.5m). The seasonal phase (2012 1486 yrs BP) is characterized by the dominance of calcareous species, indicating a seasonal melting of the sea-ice cover. This led to high productivity and a more open and energetic environment, with possible intrusion of warmerwater masses. During the transitional phase (1486 696 yrs BP) the shift from a calcareous dominated association to an agglutinated dominated one suggests a hypoxic environment with high carbonate dissolution condition and high residency time of the water masses. This can be hypothesized to be derived from a freshwater input derived from the retreat of the local glaciers, coherent with other glaciological studies of the region. During the final cold phase (696 yrs BP present) the sedimentation rate decrease and few foraminiferal specimens are present, thus indicating ephemeral openings or a more prolonged cover of the sea ice during the summer. In addition, despite the hypothesized absence of echinoderm remains in the Southern Ocean due to fast dissolution rate of carbonate, we were able to identify an ophiuroid species and confirm the presence of irregular echinoids. Significant differences regarding the presence/absence of these two groups with respect to the foraminiferal assemblages were detected. This study shows the usefulness of calcareous microfossils in cold marine environments and hints a yet unexplored potential of echinoderm remains as a palaeoceanographic proxy in such regimes