[B-PT03] Biomineralization and Geochemistry of Proxies

[BPT03-P02] Seasonal changes of planktic foraminifera in the subtropical Northwest Pacific based on sediment trap samples

*Azumi Kuroyanagi¹, Atsushi Suzuki², Kyoko Yamaoka², Yuri Hashimoto³, Takeshi Fujii⁴, Shunsuke Kondo⁴, Jumpei Minatoya⁵ (1.Tohoku University Museum, The Center for Academic Resources and Archives, Tohoku University, 2.Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 3.Tohoku University, 4.KANSO, 5.Japan Oil, Gas and Metals National Corporation (JOGMEC))

Keywords:Planktic Foraminifers, Sediment trap, Western North Pacific

Planktic foraminifers are marine plankton with calcite tests, and the ocean surface environment can be reflected in their abundance, assemblage and shell chemical composition. Thus, planktic foraminifera plays an important role in the reconstruction of paleoenvironments. In fact, based on planktic foraminiferal records, subtropical biodiversity is predicted to decrease in the near future due to global warming. However, only a few modern planktic foraminifera studies in the subtropical Pacific Ocean have been reported. In this study, we used sediment trap samples from the subtropical Pacific Ocean with a two-week time resolution to examine in detail the seasonal changes in fluxes and assemblage of planktic foraminifera. Foraminiferal fluxes showed large seasonal variations, generally high in winter and low in summer. This was not associated with fluctuations in total fluxes, which were relatively high in summer and autumn. It suggests that foraminiferal fluxes in the subtropics are generally dominated by factors unrelated to total fluxes, such as sea surface temperature and water column stratification.Foraminiferal assemblage composition also showed a large seasonal variation, with each species showing a peak in flux at different times. This might be attributed to the different environmental factors that regulate each species.