Late Pleistocene calcification and dissolution patterns in planktonic foraminifera from the Central Indian Basin

Planktonic foraminifera exhibit species-specific responses to temperature, salinity, nutrient supply, and carbonate chemistry, making them sensitive recorders of past ocean conditions. This study investigates the late Pleistocene calcification and dissolution patterns in planktonic foraminifera using two deep-sea sediment cores (BC 37, water depth: 4,252 m; SVBC 37, water depth: 3,992 m) from the Central Indian Basin (CIB). We analysed shell weight, test size, and scanning electron microscopic (SEM) evidence in three species with varying susceptibility to dissolution, namely Globorotalia menardii, Pulleniatina obliquiloculata , and Neogloboquadrina dutertrei . The results reveal species-specific calcification responses to glacial-interglacial climate forcing and a strong post-depositional overprint driven by deep-water carbonate saturation. Notably, enhanced shell weights during glacial stages in G. menardii and N. dutertrei indicate improved preservation associated with higher concentrations of carbonate ions. At the same time, the SEM image confirms progressive test degradation during dissolution-prone intervals, such as Marine Isotope Stage (MIS) 11. Weak correlations between shell weight and size underscore the influence of diagenesis and test wall thinning near the lysocline. Variations in the lysocline and carbonate compensation depth (CCD), together with changes in monsoon-driven productivity, further modulate preservation patterns. These findings highlight the complex interplay between calcification, dissolution, and carbonate chemistry across climate cycles, providing valuable insights into biogenic carbonate dynamics and their implications for both past and future ocean acidification scenarios.