Radiolarian assemblages of the late Neogene North Pacific

Radiolarian census and abundance data were collected from three deep-sea cores drilled by the Ocean Drilling Program Sites 884, 887 and 1151 to investigate patterns of ecologic changes in space and time during the last 16 million years for the mid-latitude to subarctic North Pacific. High concentrations of radiolarians occurred between 9.0 and 2.7 Ma. Radiolarian species richness was highest in the early middle Miocene at each site and gradually decreased up to about 7 Ma, coinciding with a well-established global cooling trend. A degree of overlap index calculated for radiolarian assemblages revealed 11 faunal change events, of which 8 corresponded to global cooling events and expansions of polar ice sheets. Three of the faunal change events were observed within the peak of radiolarian accumulation rate and were ascribed to changes in primary productivity in the North Pacific rather than global climatic changes. […]

通过对深海岩芯的采样，海洋钻探计划中的884、887和1151号站点收集了放射虫种群及其丰度数据，旨在研究过去1600万年中，中纬度至副北极的北太平洋地区生态变化的空间与时间模式。在距今9.0至2.7百万年的时期内，放射虫的浓度较高。在各个采样点，放射虫物种多样性在渐新世早期达到峰值，随后逐渐下降至约700万年前，这一时期恰与全球性的降温趋势相吻合。对放射虫组合群所计算的交叉重叠指数揭示了11次生物群落变化事件，其中8次与全球冷却事件和极地冰盖的扩张相对应。在放射虫积累速率峰值期间观察到的3次生物群落变化事件，归因于北太平洋初级生产力的变化，而非全球气候变化。 [...]