Paleogene to early Neogene calcareous nannoplankton biochronology and evolution (IODP Expedition 390/393)

钙质纳米浮游生物是一种微小的海洋藻类，可以产生方解石外骨骼（球球/球石），在地质记录的几乎所有海洋沉积物中都可以找到。通过研究由国际海洋发现计划（IODP）从海底提取的沉积物中保存的钙质纳米化石，我们可以记录它们随时间的演变，包括物种数量（多样性）的变化，物种形成和灭绝的速度，以及种群组成。我们可以利用这些信息来提供沉积物的准确年龄，这是像IODP JOIDES Resolution这样的深海钻井船的一项重要任务，这些结果将告诉我们是否达到了最初的目标。钙质纳米浮游生物对海洋环境的变化非常敏感，特别是海洋表面温度和营养物质的可用性，个别物种或群体偏爱特定的生态位。利用丰富的化石物种，我们能够重建过去特定时间特定地点的环境条件。IODP探险队390将航行到南大西洋，并从古近纪到新近纪的时间间隔（大约6000万年前到现在）采集深海沉积物，这是地球气候历史上的一个关键时期，标志着从高二氧化碳，非常温暖的“温室”气候过渡到一个更凉爽的“冰库”世界，南极大冰盖盛衰。在这一深刻的气候变化期间，海洋和陆地领域的环境和生态系统发生了巨大变化。始新世早期（~ 5600万- 5000万年前）的特征是一系列快速变暖事件，称为超热事件，随后是始新世晚期的长期降温，然后是渐新世和中新世早期（~ 3300万- 2000万年前）的冰期-间冰期旋回。钙质纳米浮游生物是这一时期海洋浮游植物的主要组成部分，其多样性在始新世达到顶峰，但随后随着从温室到冰窖的重大气候变化而急剧下降。然而，这种进化变化的精确时间和速度仍然知之甚少，我们计划更好地了解浮游生物进化与南大西洋古气候变化之间的关系。更好地理解这种关系是预测未来气候变化对海洋生物圈和生态系统功能的规模和影响的关键。为了回答这些研究问题，我们首先必须检查我们将要钻取的深海岩心是否属于正确的地质年代，是否有连续的时间记录，是否有保存我们需要的化石的沉积物类型。该研究项目将为IODP初步远征390C和395E所钻探的地点提供年龄控制，这将是即将于2022年启航的远征成功的关键。

Calcareous nannoplankton are microscopic marine algae that produce calcite exoskeletons (coccospheres/coccoliths) which can be found in almost all marine sediments in the geological record. By studying the calcareous nannofossils preserved within sediments cored from the sea-floor by the International Ocean Discovery Program (IODP) we can document their evolution through time, including changing number of species (diversity), rates of speciation and extinction, and population compositions. We can use this information to provide accurate ages of the sediments, which is an important task on a deep-sea drilling ship like the IODP JOIDES Resolution, and these results will tell us whether we have achieved our initial objectives. Calcareous nannoplankton are sensitive to changes in ocean environment, particularly sea-surface temperature and nutrient availability, with individual species or groups preferring specific ecological niches. Using the abundance of fossil species, we are able to reconstruct past environmental conditions for a specific location at a given time. IODP Expedition 390 will sail to the South Atlantic Ocean and core deep-sea sediments from the Paleogene to Neogene time interval (around 60 million years ago to present), a key interval in Earth's climate history marking the transition from high CO2, very warm 'greenhouse' climates into a much cooler 'icehouse' world with large Antarctic ice sheets that waxed and waned. This profound interval of climatic change saw dramatic shifts in the environments and ecosystems of the marine and terrestrial realms. A series of rapid warming events, known as hyperthermals, characterise the early Eocene (~56-50 million years ago), followed by long-term cooling through the later Eocene, and then glacial-interglacial cycles through the Oligocene and early Miocene (~33-20 million years ago). Calcareous nannoplankton were the dominant ocean phytoplankton at this time and peaked in diversity in the Eocene but then suffered major decline coinciding with this major climatic change from greenhouse to icehouse. However, the precise timing and speed of this evolutionary change is still poorly known and we plan to better understand this relationship between plankton evolution and palaeoclimatic change in the South Atlantic. A better understanding of this relationship is key to predicting the magnitude and impact of future climate change on the ocean biosphere and ecosystem functions. To answer these research questions, we first have to check that the deep-sea cores that we will drill will be of the right geological age, with continuous records through time, and in sediment types that preserve the fossils we need. This research project will provide the age control for the sites that were drilled by the preliminary IODP Expeditions 390C and 395E and this will be key to the success of the forthcoming expeditions which will sail in 2022.