Changes in benthic ecosystems and ocean circulation in the Southeast Atlantic across Eocene Thermal Maximum 2 BENTHIC ECOSYSTEM RESPONSE TO ETM2
Changes in benthic ecosystems and ocean circulation in the Southeast Atlantic across Eocene Thermal Maximum 2 BENTHIC ECOSYSTEM RESPONSE TO ETM2
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始新世热最大值 2 东南大西洋底栖生态系统和海洋环流的变化 底栖生态系统对 ETM2 的响应
DOI：
10.1002/2015pa002821
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
Jennions S
中科院分区：
文献类型：
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作者：
Jennions S
始新世热极大期2 （ETM2）发生在古新世—始新世热极大期（PETM）之后约1.8 Myr，与PETM一样，具有负碳同位素偏移和变暖的特征。我们结合东南大西洋1263 （1500 m古深度）和1262 （3600 m古深度）的底栖有孔虫和沉积学记录，发现在ETM2峰值期间，底栖有孔虫多样性和积累速率在较浅的地点下降得更为急剧和严重。由于这些地点距离很近，地表生产力的差异不可能造成这种差异效应。相反，我们推断穿越ETM2的海洋环流变化可能在中深度产生了更明显的变暖（站点1263）。变暖的影响包括代谢率的增加、有效食物供应的减少和脱氧的增加，因此可能解释了1263站点更严重的底栖生物影响。因此，1263地点的生物扰动可能比1262地点减少得更多，这对总体碳酸盐记录的影响有所不同。我们使用沉积物-启用地球系统模型来测试生物扰动的减少和/或更差通风水域的碳酸盐饱和度可能降低是否可以解释Site 1263中体积δ13C的更极端偏移和wt % caco3的更剧烈转变。我们发现，在ETM2峰值期间，酸化增强和生物扰动减少都需要解释所观察到的特征。我们的综合生态学和模型分析说明了海洋环流变化在放大局部环境变化和推动暂时但剧烈的底栖生物多样性和丰度丧失方面的潜在作用。
Eocene Thermal Maximum 2 (ETM2) occurred ~1.8 Myr after the Paleocene‐Eocene Thermal Maximum (PETM) and, like the PETM, was characterized by a negative carbon isotope excursion and warming. We combined benthic foraminiferal and sedimentological records for Southeast Atlantic Sites 1263 (1500 m paleodepth) and 1262 (3600 m paleodepth) to show that benthic foraminiferal diversity and accumulation rates declined more precipitously and severely at the shallower site during peak ETM2. As the sites are in close proximity, differences in surface productivity cannot have caused this differential effect. Instead, we infer that changes in ocean circulation across ETM2 may have produced more pronounced warming at intermediate depths (Site 1263). The effects of warming include increased metabolic rates, a decrease in effective food supply and increased deoxygenation, thus potentially explaining the more severe benthic impacts at Site 1263. In response, bioturbation may have decreased more at Site 1263 than at Site 1262, differentially affecting bulk carbonate records. We use a sediment‐enabled Earth system model to test whether a reduction in bioturbation and/or the likely reduced carbonate saturation of more poorly ventilated waters can explain the more extreme excursion in bulk δ13C and sharper transition in wt % CaCO3at Site 1263. We find that both enhanced acidification and reduced bioturbation during the ETM2 peak are needed to account for the observed features. Our combined ecological and modeling analysis illustrates the potential role of ocean circulation changes in amplifying local environmental changes and driving temporary, but drastic, loss of benthic biodiversity and abundance.