Relation between benthic foraminifera and organic carbon during the Last Glacial-Holocene climate transition in the Potiguar Basin

BACKGROUND The Last Glacial-Holocene transition was characterized by climatic events and Atlantic Meridional Overturning Circulation (AMOC) changes recorded in the marine sediments. We hypothesize that during millennial-scale climatic extremes, such as the Heinrich Event 1 and the deglacial transition (Termination I), AMOC slowdown triggered shifts in productivity, directly linked to organic carbon flux to the seafloor, causing physiological disturbances in the species and assemblages of deep-sea benthic foraminifera of the Brazilian Equatorial Margin. OBJECTIVES Define benthic foraminifera assemblages, functional groups, and morphotypes variability and their relation with organic carbon, since the Marine Isotope Stage (MIS) 2; Illustrate potential taphonomic alterations in recovered species using Scanning Electron Microscope (SEM) microphotographs; Perform univariate and multivariate statistical analyses, inputting δ 18O, grain size, and total carbon data to infer structural variations in the benthic foraminifera community over the last 24ka. METHODS The sedimentary core MD09-3253CQ was collected at 3.867 m depth during the oceanographic expedition 173/RETRO III (RV/Marion Dufresne) using a Calypso Square Core (CASQ). For assemblage analysis, at least 300 specimens per sample were picked at a 10 cm resolution. MIS 1 corresponds to the upper 0-32cmand MIS 2 from 32.5 to 108 cm. The age-depth model was stablished by radiocarbon dating and stable oxygen isotope (δ¹⁸O) tie-points. Statistical analyses used PRIMER 6, and taxonomy was validated via the World Register of Marine Species (WoRMS). Microphotographs of dominant species were acquired using a SEM (Hitachi ™ 3000). RESULTS Foraminiferal assemblages from MIS 2 and Termination I suggest less pronounced surface primary production. In MIS 1, rotaliids dominate, led by Epistominella exigua, Alabaminella weddellensis and Globocassidulina subglobosa. Most of the species' exhibit trochospiral coiling and absence of large pores, typical of epifaunal taxa, showing the occurrence of Phyto detritus on the sediment surface. Elongated infaunal species, such as Fursenkoina davisi, known as deposit feeders, were also present, showing the microhabitat preferences driven by Total Organic Carbon (TOC) availability and oxygen gradients. These species are known as r-strategists, and their abundance reflects seasonal phytodetrital pulses. CONCLUSION R-strategists species responded to abrupt TOC pulses with rapid growth and reproduction, becoming the most abundant in some biofacies. As TOC shape the microhabitats of some deep-sea benthic foraminiferal species, and once benthic activity controls deep-sea floor carbon budgets, paleoreconstructions based in this coupled analysis reveals events beyond glacial-interglacial cycles controlling biofacies of benthic foraminiferal communities.