Pelagic marine ecosystem responses to Plio-Pleistocene Climate Change

光合微型浮游生物在海洋食物网和全球碳循环中发挥着重要作用。海洋浮游植物，其中颗石藻和硅藻是主要群体，也负责全球初级生产的大约一半（Field等人，1998年）。这两个群体的适宜栖息地的范围在地质时间尺度上有很大变化（Lazarus等人，2014; Gibbs等人，2016年）和人为气候变化预计将导致浮游植物分布在未来几个世纪的大规模变化（Rost & Riebesell，2004年;博伊德等人，2016).未来的气候状态预计会超出历史时期观测到的范围，但地质记录中存在这些条件的适当类比（Burke et al.，2018年）。在上新世中期温暖期（mPWP，3.29-2.97Ma），大气中的CO2浓度与现代值相当，约为400 ppmv，全球平均气温比工业化前高出约3摄氏度（Haywood & Valdes，2004）。因此，mPWP可能是相对浓度路径（RCP）4.5下的近期地球条件的一个很好的类比，这是一种“中间”温室气体排放情景（IPCC，2014; Burke等人，2018年）。在末次间冰期（LIG，130- 80 ka），全球气温比工业化前高出1 ℃，全球平均海平面高出4- 9米（达顿等人，2015; Fischer等人，2018年），提供了一个模拟的未来气候不那么极端，在较低的RCP目标1。量化过去3.5Ma硅藻、颗石藻和鱼化石的绝对丰度，重点关注mPWP和LIG 2。2.三组与气候之间的协方差检验3。过去和未来温暖期的浮游食物网模型4。预测未来人为气候变化下鱼类生物量和丰度的变化使用IODP考察306和162期间回收的沉积物岩心样本;我们将调查北大西洋两个地点的生态发展（图2）。在过去的3.5 Ma。这些样品可从不莱梅大学的IODP岩心库免费获得。我们将对mPWP和LIG进行2ka分辨率的高分辨率采样，背景时间减少到30 ka。将采用不同的方法计算每种浮游植物的绝对丰度：SYRACO软件将自动计算颗石藻（博福特和Dollfus，2004年）; Warnock和谢勒（2014年）的方法计算硅藻。上新世-更新世的鱼类丰度将使用鱼类化石（鱼类的显微镜遗骸）进行量化（例如Sibert等人，2020年）。我们将使用随机微分方程（SDES）将这三组的丰度数据与现有的古气候代用指标（例如，Lisiecki & Raymo，2005）相结合。这项研究将使用NEMO-ERSEM评估具有商业重要性的远洋渔业未来生态系统崩溃的可能性（Baretta等人，1995; Madec，2008）、FABM（Bruggeman & Bolding，2014）和MIZER（Blanchard等人，2014）食物网模型模拟了mPWP，LIG和20世纪末的气候情景。

Photosynthetic nannoplankton play a fundamental role in both ocean food webs and the global carbon cycle. Marine phytoplankton, of which coccolithophore and diatoms are the dominant groups, are also responsible for around half of global primary production (Field et al., 1998). Extent of suitable habitat for these two groups has varied significantly over geological timescales (Lazarus et al., 2014; Gibbs et al., 2016) and anthropogenic climate change is expected to cause large-scalechanges in phytoplankton distributionover the coming centuries (Rost & Riebesell, 2004; Boyd et al., 2016).Future climate states are expected to fall outside of the range of those observed in historic times, but suitable analogies for these conditionsexist in the geological record (Burke et al., 2018). During the mid-Pliocene Warm Period(mPWP, 3.29-2.97Ma), atmospheric CO2 concentrations were comparable to modern values of ~400ppmv, and mean global temperature was around 3C warmer than preindustrial (Haywood & Valdes, 2004). Hence, the mPWP is potentially a good analogy for near-future Earth conditions under Relative Concentration Pathway (RCP) 4.5, an 'intermediate' greenhouse gas emissions scenario (IPCC, 2014; Burke et al., 2018). During the Last Interglacial (LIG, 130-80ka), global temperatures were up to 1C warmer than preindustrial, and global mean sea level around was 4-9m higher(Dutton et al., 2015; Fischer et al., 2018), providing an analogue for a less extreme future climate ina lower RCP scenarioObjectives1. Quantify the absolute abundance of diatoms, coccolithophores and ichthyoliths over the past 3.5Ma, with a focus on the mPWP and LIG2. 2. Test for covariance between the three groups and climate3. Model pelagic food webs for both past and future warm periods 4. Predict changes in fish biomass and abundance under future anthropogenic climate changeUsing sediment core samples recovered during IODP expeditions 306 and 162; we will investigate the ecological development of two North Atlantic locations (Fig. 2.) over the last 3.5 Ma. These samples are freely available from the IODP core repository at the University of Bremen.We will carry out high-resolution sampling for both the mPWP and LIG at 2ka resolution, reducing to 30ka for background times. Different methods will be employed to calculate the absolute abundance of each phytoplankton group: the SYRACO software will make automated counts of coccolithophores (Beaufort & Dollfus, 2004); and the method of Warnock & Scherer (2014) for diatoms. Fish abundance through the Plio-Pleistocene will be quantified using ichthyoliths, the microscopic remains of fish(e.gSibert et al., 2020). Ichthyoliths and nannoplankton can be obtained from the same sediment samples.We will use stochastic differential equations (SDEs) to integrate abundance data from the three groups withexisting proxies for palaeoclimate (e.g. Lisiecki & Raymo, 2005). This study will assess the possibility of future ecosystem collapse in commercially-important pelagic fisheries using the NEMO-ERSEM (Baretta et al., 1995; Madec, 2008), FABM (Bruggeman & Bolding, 2014) and MIZER (Blanchard et al., 2014) food web modelssimulated for the mPWP, LIG, and late-20thcentury climate scenarios.