The deep sea comprises more than 90% of the ocean; therefore, understanding the controlling factors of biodiversity in the deep sea is of great importance for predicting future changes in the functioning of the ocean system. Consensus has recently been increasing on two plausible factors that have often been discussed as the drivers of deep‐sea species richness in the contexts of the species‐energy and physiological tolerance hypotheses: (i) seafloor particulate organic carbon (POC) derived from primary production in the euphotic zone and (ii) temperature. Nonetheless, factors that drive deep-sea biodiversity are still actively debated potentially owing to a mirage of correlations (sign and magnitude are generally time dependent), which are often found in nonlinear, complex ecological systems, making the characterization of causalities difficult. Here, we tested the causal influences of POC flux and temperature on species richness using long-term palaeoecological datasets derived from sediment core samples and convergent cross mapping, a numerical method for characterizing causal relationships in complex systems. The results showed that temperature, but not POC flux, influenced species richness over 10³–10⁴-year time scales. The temperature–richness relationship in the deep sea suggests that human-induced future climate change may, under some conditions, affect deep-sea ecosystems through deep-water circulation changes rather than surface productivity changes.

深海占海洋面积的 90% 以上；因此，了解深海生物多样性的控制因素对于预测未来海洋系统功能的变化具有重要意义。在物种能量和生理耐受性假设的背景下，经常被讨论为深海物种丰富度驱动因素的两个似是而非的因素最近得到了越来越多的共识：（i）来自初级生产的海底颗粒有机碳（POC）在透光区和（ii）温度。尽管如此，由于相关海市蜃楼（符号和大小通常与时间相关），驱动深海生物多样性的因素仍在积极辩论中，这些相关性通常存在于非​​线性、复杂的生态系统中，使得因果关系的表征变得困难。在这里，我们使用来自沉积物核心样本和收敛交叉映射的长期古生态数据集测试了 POC 通量和温度对物种丰富度的因果影响，这是一种表征复杂系统中因果关系的数值方法。结果表明，温度而不是 POC 通量影响物种丰富度超过 10³ –10 ⁴年时间尺度。深海的温度-丰富度关系表明，在某些条件下，人类引起的未来气候变化可能通过深水环流变化而不是地表生产力变化来影响深海生态系统。