Edisto Inlet as a sentinel for Late Holocene environmental changes over the Ross Sea: insights from foraminifera turnover events

Identifying marine environmental changes is im- portant to understand the processes that govern the Earth’s climate system and its interacting components. Microfossil assemblages are one of the most used palaeoenvironmen- tal tracers, with their community composition responding to changes in the physiochemical characteristics of the envi- ronment. In this context, foraminifera have been extensively used due to their preservation potential. However, little atten- tion has been paid to the properties of the whole foraminiferal community that, in turn, can be used to depict a comprehen- sive view of the environment. In this study we focused on the laminated marine sediment core TR17-08 collected in Edisto Inlet (Ross Sea, Antarctica) and the turnover events that char- acterized the benthic foraminiferal fauna over the last 3.6 kyr. Using rate-of-change (RoC) analysis, three distinct turnover events were recognized having a long-term effect on the fauna: at 2.7–2.5, 1.2–1.0 and 0.7 kyr BP. At 2.7–2.5 kyr BP, Miliammina arenacea disappears and are substituted by dif- ferent calcareous species, such as Epistominella exigua, Non- ionella iridea and Stainforthia feylingi. Aligning with the micropalaeontological interpretations, changes in X-ray flu- orescence (XRF) ratios (Zr / Rb; Ca / Ti and Br / Ti) were co- eval with the interpretation derived from the RoC and the microfossils assemblage composition. Over this transition, a switch from multi-year landfast sea ice (3.6–2.7 kyr BP) to a seasonal sea-ice-dominated environment (2.5–1.2 kyr BP) was driven by a change in the water mass characteristics, increasing the mCDW (modified Circumpolar Deep Water) content inside the fjord as well as increase the duration of the summer ice-free period. Higher RoC values suggested the absence of a stable benthic foraminifera community un- der the frequent multi-year landfast sea-ice scenario, while the lowest RoC values during the seasonal sea-ice phase are present, especially within the 2–1.5 kyr BP interval, aligning with the macrofaunal response inside the inlet. Continental archives (penguin and elephant seals remains) along the Vic- toria Land coast recorded such a change in the sea-ice type during the Late Holocene. This study provides further evi- dence of a change in the sea-ice state in the Ross Sea af- ter 2.7–2.5 kyr BP, thus supporting that this water mass in- trusion onto the continental shelf was more prominent dur- ing the 2.5–1.2 kyr BP period, in accordance with the persis- tent summer positive mode of the Southern Annular Mode. Lastly, this study highlights that using ecological proper- ties of the benthic foraminifera community can be a valu- able source of information for high-resolution studies and can provide additional insights into the palaeoenvironmental interpretation and palaeoclimatic reconstruction that uses benthic foraminiferal species as environmental indicators