Nannofossil absolute abundances of sediment core GeoB2204-2@en

The calcareous nannofossil assemblages from sediment core GeoB2204-2 from the western equatorial region off Brazil were examined to document oceanographic changes in surface waters during the last 155 ka. Coccolith counts (N) were made manually using a Zeiss DSM 940A scanning electron microscope at 3,000x or 5,000x magnification. The recorded fluctuations in the abundance and composition of coccolithophore communities reflect changes in surface water masses. The community is dominated by species from the deeper photic zone, such as Florisphaera profunda and Gladiolithus flabellatus, indicating predominantly oligotrophic conditions during glacial periods. During interglacial periods, higher abundances and larger proportions of species with an affinity for nutrient-rich surface waters indicate the highest abundances.本研究对取自巴西西侧赤道海域的沉积物岩芯GeoB2204-2中的钙质超微化石（calcareous nannofossil）组合体开展分析，旨在重建过去155 ka以来表层海水的海洋环境变化。颗石藻计数（N）采用蔡司（Zeiss）DSM 940A型扫描电子显微镜，以3000倍或5000倍放大倍率手动完成。记录的颗石藻群落丰度与组成波动，可反映表层水团的演化过程。该群落以栖息于深透光带的物种为主，如富卵球石藻（Florisphaera profunda）和扇形剑石藻（Gladiolithus flabellatus），指示冰期整体以贫营养环境为主。而在间冰期阶段，偏好富营养表层水体的物种丰度更高、占比更大，此时群落总丰度达到峰值。