Reconstructing Modern and LGM Water Column Hydrography Using Stable Isotopes of Single Specimens of Multiple Planktic Foraminifera

Oxygen and carbon isotope data from planktic foraminifera play an important role in paleoceanographic reconstructions of temperature, salinity, and nutrients. Typically, such analyses are conducted using multiple shells of the same species. However, important habitat depth and seasonal information are lost in pooled shell analyses. In this study, we have analyzed the δ18O and δ13C of single specimens of different species of planktic foraminifera including G. ruber (pink & white var.), G. sacculifer, O. universa, G. siphonifera, S. dehiscens, G. conglobatus, G. menardii, N. dutertrei, P. obliquiloculata, G. truncatulinoides and G. tumida from a western Caribbean core (OPDP 999A) and eastern equatorial Pacific (EEP) core (TR163-19). We use the average species δ18O values to estimate mean depth habitats and, for comparison purposes, normalize each species δ18O values to the δ18O:temperature relationship of G. ruber/O. universa (Bemis et al., 1998; Thunell et al, 2000). In order to compare δ13CDIC through time and space, we develop δ13C ‘corrections’ to normalize the δ13CFORAM values to the modern δ13CDIC for each core site. We find that both δ18O and δ13C normalization for each species varies between sites and attribute this variation to water column differences in [CO32-] between the Caribbean and EEP. We explore employing these corrections through time by applying the modern corrections to LGM δ13C /δ18O data. This multispecies, individual shell analysis approach may provide a method to infer changes in upper water column δ18OSW and δ13CDIC gradients through time