Sr/Ca in multiple species of planktonic foraminifera: Implications for reconstructions of seawater Sr/Ca.

Sr/Ca ratios were measured on eight species of planktonic foraminifera from a core top transect of the North Atlantic. Five of the species (Globigerinoides ruber, Globigerina bulloides, Neogloboquadrina pachyderma, Globigerinoides sacculifer, Globigerinella siphonifera) show remarkably little within-species variability in Sr/Ca (1.2 ± 0.1%). Three globorotaliid species (Globorotalia hirsuta, Globorotalia inflata, Globorotalia truncatulinoides) show somewhat greater variability (3-7%). Interspecies variations are of ∼10%. The variability in globorotaliid Sr/Ca is explained either by a greater temperature sensitivity than for other species or by depth-dependent dissolution. Other than this effect, the overwhelming control on foraminiferal Sr/Ca appears to be seawater Sr/Ca. In contrast, time series Sr/Ca records of four species from a North Atlantic sediment core over a glacial-interglacial cycle show very significant differences. N. pachyderma shows large-amplitude changes in Sr/Ca (9.7%), in phase with