(Table DR1) Abundance of benthonic foraminifera in sediments from ODP Hole 113-690

A mass extinction of deep-sea benthic foraminifera has been documented globally, coeval with the negative carbon isotope excursion (CIE) at the Paleocene-Eocene boundary, which was probably caused by dissociation of methane hydrate. A detailed record of benthic foraminiferal faunal change over ~30 k.y. across the carbon isotopic excursion at the Ocean Drilling Program Site 690 (Southern Ocean) shows that shortly before the CIE absolute benthic foraminiferal abundance at that site started to increase. 'Doomed species' began to decrease in abundance at the CIE by a few thousand years. After the extinction faunas were dominated by small species, which resemble opportunistic taxa under high-productivity regions in the present oceans. Calcareous nannofossils (primary producers), however, show a transition to more oligotrophic nannofloras exactly where the benthic faunas show the opposite. Plankton and benthos is thus decoupled. Possibly, a larger fraction of food particles reached the seafloor after the CIE, so that food for benthos increased although productivity declined. Enhanced organic preservation might have resulted from low-oxygen conditions caused by oxidation of methane. Alternatively, and speculatively, there was a food-source at the ocean floor. Benthic foraminifera dominating the post-extinction fauna resemble living species that symbiotically use chemosynthetic bacteria at cold seeps. During increased, diffuse methane escape from hydrates, sulfate-reducing bacteria could have produced sulfide used by chemosynthetic bacteria, which in turn were used by the benthic foraminifera, causing extinction by a change in food supply.全球范围内均已记录到深海底栖有孔虫（deep-sea benthic foraminifera）的大规模灭绝事件，该事件与古新世-始新世界线（Paleocene-Eocene boundary）处的负碳同位素偏移（negative carbon isotope excursion, CIE）同期发生，其诱因可能为甲烷水合物（methane hydrate）的解离。对大洋钻探计划（Ocean Drilling Program）690号站位（南大洋）处跨越该碳同位素偏移事件、时长约3万年的底栖有孔虫动物群变化的详细记录显示，在CIE发生前不久，该站位的底栖有孔虫绝对丰度即开始上升。'注定灭绝类群'在CIE发生后的数千年内，其丰度开始下降。灭绝事件发生后，动物群以小型物种为主，这类类群与现代海洋高生产力区域内的机会主义类群特征相似。然而，作为初级生产者（primary producers）的钙质超微化石（calcareous nannofossils），其群落组成向更贫营养型超微浮游植物群（oligotrophic nannofloras）转变的趋势，恰好与底栖动物群的变化趋势相反。由此可见，浮游生物（plankton）与底栖生物（benthos）的生态响应出现了解耦现象。一种可能的解释是，在CIE发生后，有更大比例的食物颗粒抵达海底，使得底栖生物的食物供给得以提升，尽管此时海洋初级生产力有所下降。甲烷氧化作用引发的低氧环境，可能增强了海底有机质的保存效率。另外一种带有推测性的假说则认为，海底存在额外的食物来源：灭绝事件后占动物群主导地位的底栖有孔虫，与冷泉（cold seeps）环境中与化能合成细菌（chemosynthetic bacteria）共生的现生物种特征相似。在甲烷水合物弥散性逸出量增加的过程中，硫酸盐还原菌（sulfate-reducing bacteria）可产生硫化物，供化能合成细菌利用，而后者又可作为底栖有孔虫的食物来源，最终通过改变食物供给路径引发了本次灭绝事件。