Plankton evolution during peak greenhouse climates

钙质纳米浮游生物是一种微小的海洋藻类，它们分泌的钙质细胞覆盖物（球石）在地理上广泛分布的远洋沉积记录中得到了保存。通过研究保存在沉积物中的钙质纳米化石组合，我们可以记录它们随时间的演变，包括变化的多样性，物种形成和灭绝的速度，以及种群组成。钙质纳米浮游生物对环境参数的变化非常敏感，特别是海洋表面温度和营养物质的可用性，个别物种或群体对特定的生态位表现出特殊的偏好。因此，利用一个组合中物种的数量丰度，我们能够重建过去特定地点在给定时间的环境条件。国际海洋发现计划第371远征队将在西南太平洋钻探深海沉积物，回收始新世时期的岩心。始新世是地球气候历史上的一个关键时期，标志着从非常温暖的“温室”气候过渡到一个更凉爽的“冰窖”世界，那里有大片的南极冰盖。在这一深刻的气候变化期间，海洋和陆地领域的物理、化学和生物参数发生了重大变化。始新世早期的特征是一系列快速变暖事件，即所谓的超热现象，随后是始新世中期和晚期的长期降温。钙质纳米浮游生物是这一时期主要的海洋浮游植物群，其多样性达到顶峰，但随后急剧下降，并经历了与这一重大气候重组相一致的重大种群变化。然而，这种进化变化的确切时间和结构仍然鲜为人知。在这项研究中，我们将制作钙质纳米浮游生物组合记录（多样性和种群数据），以确定纳米浮游生物进化与西南太平洋古气候和古海洋变化之间的关系。

Calcareous nannoplankton are microscopic marine algae that secrete calcitic cell coverings (coccoliths) which are preserved throughout the geographically-widespread pelagic sedimentary record. By studying calcareous nannofossil assemblages preserved within sediments we can document their evolution through time, including changing diversity, rates of speciation and extinction, and population compositions. Calcareous nannoplankton are very responsive to changes in environmental parameters, particularly sea surface temperature and nutrient availability, with individual species or groups exhibiting particular preferences for specific ecological niches. Using the quantitative abundance of species within an assemblage we are therefore able to reconstruct past environmental conditions for a specific location at a given time. International Ocean Discovery Program Expedition 371 will drill deep-sea sediments in the Southwest Pacific Ocean, recovering cores which are from the Eocene epoch, a key interval in Earth's climate history marking the transition from very warm 'greenhouse' climates into a much cooler 'icehouse' world with large Antarctic icesheets. This profound interval of climatic change saw major shifts in physical, chemical and biological parameters in the marine and terrestrial realms. A series of rapid warming events, known as hyperthermals, characterise the early Eocene, followed by a long-term cooling through the middle and late Eocene. Calcareous nannoplankton, which were the dominant oceanic phytoplankton group at this time, peaked in diversity but then suffered a major decline and underwent significant population change coinciding with this major climatic reorganisation. However, the precise timing and structure of this evolutionary change is still poorly known. In this research we will produce calcareous nannoplankton assemblage records (diversity and population data) in order to determine the relationship between nannoplankton evolution and palaeoclimatic and palaeoceanographic change in the South West Pacific.