Pelagic marine ecosystem responses to Plio-Pleistocene Climate Change

光合作用的纳米浮游生物在海洋食物网和全球碳循环中都发挥着重要作用。海洋浮游植物，其中球石藻和硅藻是优势群体，也占全球初级产量的一半左右（Field等人，1998年）。这两类生物的适宜栖息地在不同的地质时间尺度上存在显著差异（Lazarus et al., 2014; Gibbs et al., 2016），预计未来几个世纪，人为气候变化将导致浮游植物分布发生大规模变化（Rost & Riebesell, 2004; Boyd et al., 2016）。预计未来的气候状态将超出历史时期观察到的范围，但在地质记录中可以找到适合这些条件的类比（Burke et al., 2018）。在上新世中期暖期（mPWP, 3.29-2.97Ma），大气CO2浓度与现代值~400ppmv相当，全球平均温度比工业化前升高约3C （Haywood & Valdes, 2004）。因此，mPWP可能很好地类比了相对浓度路径（RCP） 4.5下的近未来地球条件，这是一种“中间”温室气体排放情景（IPCC, 2014； Burke等人，2018）。在末次间冰期（LIG, 130-80ka），全球气温比工业化前升高了1℃，全球平均海平面升高了4-9米（Dutton等，2015；Fischer等，2018），这为在较低RCP情景下未来不那么极端的气候提供了模拟。量化过去3.5Ma的硅藻、球石藻和鱼石藻的绝对丰度，重点是mPWP和LIG2。2. 三组与气候之间的协方差检验。模拟过去和未来暖期的远洋食物网。预测未来人为气候变化下鱼类生物量和丰度的变化——基于IODP考察306和162的沉积物岩心样本我们将调查两个北大西洋地区在过去3.5 Ma的生态发展（图2）。这些示例可以从不来梅大学的IODP核心存储库中免费获得。我们将在2ka分辨率下对mPWP和LIG进行高分辨率采样，将背景时间减少到30ka。将采用不同的方法来计算每个浮游植物群的绝对丰度：SYRACO软件将自动计数颗石藻（Beaufort & Dollfus, 2004）；以及Warnock & Scherer（2014）对硅藻的方法。上新世至更新世期间的鱼类丰度将通过鱼石（鱼的微观遗骸）来量化。（sibert et al., 2020）。鱼石类和纳米浮游生物可以从相同的沉积物样本中获得。我们将使用随机微分方程（SDEs）将来自这三组的丰度数据与现有的古气候代用物（例如Lisiecki & Raymo， 2005）相结合。本研究将利用NEMO-ERSEM （Baretta et al., 1995; Madec, 2008）、FABM （Bruggeman & Bolding, 2014）和MIZER （Blanchard et al., 2014）模拟mPWP、LIG和20世纪后期气候情景的食物网模型，评估具有重要商业意义的远洋渔业未来生态系统崩溃的可能性。

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.