Seasonal Variation of Planktonic Foraminifera Assemblage in response to Seasonal Shift of Inter-Tropical Convergence Zone in the Northeastern Equatorial Pacific

Abstract

A time-series sediment trap was operated at a water depth of 4950 m from July 2003 to May 2004 at KOMO station (10 o 30'N, 131 o 20'W) in the northeastern equatorial Pacific, with the aim of understanding the temporal variation of planktonic foraminifera assemblages in response to the seasonal shift of Inter-Tropical Convergence Zone (ITCZ). A total of 22130 planktonic foraminifera specimens belonging to 30 species and 11 genera were identified, which shows a distinct seasonal variation with high values (125~288 specimens m −2 day −1 ) in the winter to spring (December-May) and low values (16~23 specimens m −2 day −1 ) in the fall (September-November). In addition, seasonal ecological differences of foraminifera assemblages are distinctly recognizable: omnivorous foraminifera occurred predominantly