Comparison in Sr/Ca ratios of different morphotypes of surface dwelling planktonic foraminifera species

Surface-dwelling foraminifera species Globigerinoides ruber (white) and Trilobatus sacculifer are the main proxy carriers for past oceanic environments. The Sr/Ca ratios of foraminifera play an important role in reflecting paleo-oceanic environmental changes. To understand the potential differences between the Sr/Ca ratios of these different morphotypes of G. ruber (white) and T. sacculifer and relevant affecting factors, we compared the Sr/Ca measurements of the two basic morphotypes of G. ruber (G. ruber sensu stricto and G. ruber sensu lato) and T. sacculifer (with sac and without sac) via the analysis of surface and downcore samples of sediment from Core MD06-3047B in the Western Philippine Sea. Results reveal that the Sr/Ca ratios of the two morphotypes of G. ruber (white) show a little difference since MIS 3 (～48 ka), while those of two types of T. sacculifer are significantly different from each other, of which that of T. sacculifer (without sac) is generally greater than that of the with-sac type. By comparing the seawater temperature and salinity from the same site, we found that the Sr/Ca ratios of G. ruber s.s., G. ruber s.l. and T. sacculifer (without sac) in our study area might be affected mainly by seawater temperature, and those of T. sacculifer (with sac) are mainly affected by surface salinity.