Calcareous nannoplankton ecology and community change across the Paleocene-Eocene Thermal Maximum

The Paleocene-Eocene Thermal Maximum (PETM; ca. 55.8 Ma) is thought to coincide with a profound but entirely transient change among nannoplankton communities throughout the ocean. Here we explore the ecology of nannoplankton during the PETM by using multivariate analyses of a global data set that is based upon the distribution of taxa in time and space. We use these results, coupled with stable isotope data and geochemical modeling, to reinterpret the ecology of key genera. The results of the multivariate analyses suggest that the community was perturbed significantly in coastal and high- latitudes sites compared to the open ocean, and the relative influence of temperature and nutrient availability on the assemblage varies regionally. The open ocean became more stratified and less productive during the PETM and the oligotrophic assemblage responded primarily to changes in nutrient availability. Alternatively, assemblages at the equator and in the Southern Ocean responded to temperature more than to nutrient reduction. In addition, the assemblage change at the PETM was not merely transient-there is evidence of adaptation and a long-term change in the nannoplankton community that persists after the PETM and results in the disappearance of a high- latitude assemblage. The long-term effect on communities caused by transient warming during the PETM has implications for modern- day climate change, suggesting similar permanent changes to nannoplankton community structure as the oceans warm.

古新世-始新世极热事件（Paleocene-Eocene Thermal Maximum, PETM；约5580万年前）被认为与全球海洋中超微浮游生物（nannoplankton）群落发生的深刻且完全短暂的变化相吻合。本研究基于全球各时空尺度下类群分布数据构建的全球数据集，通过多变量分析探究了PETM时期超微浮游生物的生态特征。我们结合上述分析结果与稳定同位素数据、地球化学模拟，重新阐释了关键属的生态特征。多变量分析结果显示，与开阔大洋相比，沿岸与高纬度海域的群落受到的扰动更为显著，且温度与营养盐可利用性对生物组合的相对影响存在区域差异。PETM时期，开阔大洋层化程度加剧且生产力下降，贫营养生物组合主要响应营养盐可利用性的变化；与之相反，赤道与南大洋的生物组合对温度的响应程度高于营养盐降低的影响。此外，PETM时期的群落变化并非仅为短暂现象——有证据表明，超微浮游生物群落发生了适应性演化与长期改变，这种改变在PETM结束后仍持续存在，并最终导致某一高纬度生物组合的消失。PETM期间的短暂变暖对海洋群落造成的长期影响，对现代气候变化具有启示意义：该结果表明，随着海洋温度升高，超微浮游生物群落结构将发生类似的永久性改变。