Did Globigerinoides ruber (pink) disappear entirely from the Indian Ocean after 120 kyr BP?

Extant since the Miocene, Globigerinoides ruber is a mixed-layer planktic foraminiferal species, cosmopolitan to the tropical–subtropical oceans. Globigerinoides ruber has multiple morphotypical variants with distinctive white and pink chromotypes. Today, the pink variety is exclusively found in the Atlantic Ocean and its nearby basins. For the past few decades, it was believed that pink-pigmented G. ruber disappeared from the Indo-Pacific Oceans at about 120 kyr BP. However, a recent study from the northwestern Bay of Bengal documented the presence of G. ruber (pink) in surface sediments. Hitherto, there was no evidence of G. ruber (pink) in downcore sediments from the Indian Ocean since 120 kyr BP. In this study, for the first time, we document the re-appearance of G. ruber (pink) from 30 to 8 kyr BP in gravity core MGS30/GC-03. The core was retrieved from the eastern BoB from a water depth of 1883 m, and its chronology was established using eight AMS radiocarbon dates. We observed high abundances of G. ruber (pink) during the Last Glacial Maximum (LGM) and Heinrich Event 1 and 2 (H1 and H2) compared to the Holocene Epoch. Higher abundances of G. ruber (pink) during the LGM were followed by a gradual decrease during the deglaciation and the early Holocene until it disappeared after around 8 kyr BP. Variability in the relative abundance of G. ruber (pink) was compared with mixed-layer and thermocline-dwelling species. The high abundance of G. ruber (pink), N. dutertrei and G. menardii during H2 and LGM in the eastern BoB suggests enhanced NE monsoon-driven vertical mixing, which may have facilitated nutrient transport from deeper layers to the thermocline and photic zone. The presence of G. ruber (pink) during glacial stages and the early Holocene demonstrates that it has not entirely disappeared from the Indian Ocean since 120 kyr BP and that its turnover may be driven by changing hydrographic conditions.