[B-PT03] Biomineralization and Geochemistry of Proxies

[BPT03-P02] Seasonal variation in planktic foraminifera from sediment trap samples in the North Pacific Subtropical Gyre

*Azumi Kuroyanagi¹, Atsushi Suzuki², Kyoko Yamaoka², Yuri Hashimoto³, Takeshi Fujii⁴, Shunsuke Kondo⁴, Jumpei Minatoya⁵ (1.Tohoku University Museum, Tohoku University, 2.Geological Survey of Japan, AIST, 3.Graduate School of Science, Tohoku University, 4.KANSO TECHNOS, 5.JOGMEC)

Keywords:Planktic foraminifers, sediment trap, North Pacific Subtropical Gyre

Planktic foraminifers are marine plankton with calcite tests, and live in the ocean surface layers. Their calcite shells constitute a significant part of the total deep-marine calcite budget in the global carbonate cycle. Moreover, the chemical composition of the shells and assemblage composition can provide the environmental conditions of their habitat. Therefore, it is essential to examine the relationship between environmental parameters (temperature, salinity, primary production, etc.) and the biological responses of foraminifera in order to better understand the carbon cycle and paleoenvironmental reconstruction. However, only a few sediment trap studies of planktic foraminifera have been reported in the North Pacific Subtropical Gyre. In the study, we investigated seasonal changes in the flux and assemblage of planktic foraminifera collected by sediment traps deployed in the subtropical gyre. Foraminiferal fluxes showed prominent seasonal variations, which was not related to total flux. It suggests that foraminiferal flux is generally controlled by factors different from the total flux in this area. In the North Pacific Subtropical Gyre, characterized by low chlorophyll-aconcentration, organic carbon flux and foraminiferal flux are less related, which may be due to the dominance of symbiont-bearing warm species (e.g., Globigerinoides ruberand Trilobatus sacculifer).Foraminiferal fluxes of each species also exhibited a significant seasonal change, however, similar seasonal trends were observed among similar biology species. This could be attributed to the different environmental factors controlling each ecological group.