[M-IS10] Global climate change driven by the Southern Ocean and the Antarctic Ice Sheet

[MIS10-P12] Distribution of benthic foraminifera off Totten Glacier and Dalton Polynya (Antarctica), and its relation to oceanography

*Mahsa Saeidi Ortakand¹, Yoshimi Kubota¹, Takuya Itaki² (1.National Museum of Nature and Science, Department of Geology and Paleontology, 2.National Institute of Advanced Industrial Science and Technology)

Keywords:Antarctica, Totten Glacier, Dalton Polynya

Benthic foraminifera from surface sediments off Totten Glacier and Dalton Polynya have been studied to investigate their spatial distribution in relation to the oceanographic conditions and to provide insights for interpreting fossil assemblages there. Generally, the benthic foraminifera in most samples were dominated by agglutinated tests. Calcareous species were found in shallow water samples (from 309 to 608 m water depth) above the calcium carbonate compensation depth (CCD) but were largely absent from deeper water assemblages (> 608 m water depth). The absence of calcareous benthic foraminifera in the shallow water assemblage sample above 419 m water depth, very close to Totten Ice Shelf, and the prevalence of resistant agglutinated assemblage there, probably attributed to the pronounced influence of the cold, high-salinity shelf waters rich in CO₂ and the presence of a shallow CCD (at least shallower than 419 m), which creates conditions unfavorable to carbonate precipitation and preservation. Samples collected farther from Totten Ice Shelf, between Totten Glacier and Dalton Polynya, exhibited higher diversity and a greater abundance of calcareous benthic foraminifera, particularly Angulogerina (Trifarina) earlandi. The preservation of various species of calcareous benthic foraminifera, and the relatively high species diversity suggest favorable environmental conditions for this benthic microfauna. Additionally, the presence of other benthic calcareous groups, such as cold-water corals, bivalves, and bryozoans associated with high total organic carbon in these samples, can be linked to abundant nutrients delivered by the intruding modified circumpolar deep water (mCDW), characterized by relatively warm temperature, high salinity, and nutrient richness. Our findings indicate that the composition, diversity, and abundance of taxa in the assemblages are primarily influenced by the CCD and local variations in water mass characteristics.