Pelagic marine ecosystem responses to Plio-Pleistocene Climate Change

中上层海洋生态系统对上更新世气候变化的响应

• 批准号: 2284638
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2284638
• 关键词: Pelagic; marine; ecosystem; responses; Plio

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.

光合纳米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类群）也占全球初级生产的一半左右（Field 等，1998）。这两个群体的适宜栖息地范围在地质时间尺度上存在显着差异（Lazarus et al., 2014; Gibbs et al., 2016），并且人为气候变化预计将在未来几个世纪内导致浮游植物分布的大规模变化（Rost & Riebesell, 2004; Boyd et al., 2016）。未来的气候状态预计将超出这些范围。 在历史时期观察到，但地质记录中存在对这些条件的适当类比（Burke 等人，2018）。在上新世中期暖期（mPWP，3.29-2.97Ma），大气中二氧化碳浓度与现代值相当（约400ppmv），全球平均气温比工业化前高约3℃（Haywood & Valdes，2004）。因此，mPWP 可能是相对浓度路径 (RCP) 4.5（“中间”温室气体排放情景）下近期地球条件的一个很好的类比（IPCC，2014 年；Burke 等人，2018 年）。在末次间冰期（LIG，130-80ka）期间，全球气温比工业化前高出 1C，全球平均海平面高出 4-9m（Dutton 等，2015；Fischer 等，2018），为较低 RCP 情景中不太极端的未来气候提供了类比目标 1。量化过去 3.5 Ma 中硅藻、颗石藻和鱼石的绝对丰度，重点关注 mPWP 和 LIG2。 2. 检验三组与气候之间的协方差。模拟过去和未来温暖时期的中上层食物网 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 探险 306 和 162 期间回收的沉积物岩心样本；我们将调查过去 3.5 Ma 中北大西洋两个地点（图 2）的生态发展。这些样本可以从不来梅大学的 IODP 核心存储库免费获取。我们将以 2ka 分辨率对 mPWP 和 LIG 进行高分辨率采样，将背景时间降低到 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) 针对硅藻的方法。上里欧-更新世期间的鱼类丰度将使用鱼石（鱼类的微观遗骸）进行量化（例如Sibert等人，2020）。鱼石和微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（SDE）将三组的丰度数据与现有的古气候代理相结合（例如Lisiecki＆Raymo，2005）。本研究将使用针对 mPWP、LIG 和 20 世纪末气候情景模拟的 NEMO-ERSEM（Baretta 等人，1995；Madec，2008）、FABM（Bruggeman 和 Bolding，2014）和 MIZER（Blanchard 等人，2014）食物网模型来评估具有商业重要性的中上层渔业未来生态系统崩溃的可能性。