Ichthyolith accumulation and age models from DSDP 527, DSDP 596, ODP 886, ODP 1209, and Gubbio

Open ocean ecosystems experienced profound disruption in biodiversity and structure during the Cretaceous-Paleogene (K-Pg) mass extinction ~66 million years ago. Extinction scenarios have suggested that a collapse of phytoplankton production rippled up the food chain causing wholesale loss of consumers and top predators. Pelagic fishes represent a key trophic link between primary producers and top predators and provide a means to examine the influence of trophic relationships during extinctions. Here we show that there is geographic heterogeneity in the abundance of fishes through the mass extinction using the accumulation rate of ichthyoliths (i.e., microscopic fish teeth and shark dermal scales). In the Tethys Sea, fish abundance falls abruptly at the boundary and remains depressed for at least 3 million years. In contrast, fish abundance in the Pacific Ocean remained at or above pre-boundary levels for at least four million years following the mass extinction, despite drastic extinctions in co-occurring primary producers and zooplankton consumers. Geographic differences in these post-disaster ecosystems suggest that the mass extinction did not produce a uniformly "dead" ocean or microbially dominated system, but instead supported, at least regionally, ecosystems with mid-trophic level abundances similar to or above those of the Late Cretaceous.约6600万年前的白垩纪-古近纪（K-Pg）大灭绝事件中，开阔海洋生态系统的生物多样性与群落结构遭受了严重破坏。相关灭绝情景研究提出，浮游植物生产力的崩溃沿食物链逐级传递，最终引发消费者与顶级捕食者的大规模消亡。远洋鱼类作为初级生产者与顶级捕食者之间的关键营养级纽带，为探究灭绝事件中的营养级联效应提供了重要研究载体。本研究通过分析鱼形微化石（ichthyoliths，即显微级鱼类牙齿与鲨鱼真皮鳞片）的堆积速率，证实了大灭绝事件期间鱼类丰度存在地理异质性。在特提斯洋，鱼类丰度在灭绝界线处骤降，并至少持续300万年处于低位；而在太平洋，尽管同期初级生产者与浮游动物消费者均发生了大规模灭绝，但其鱼类丰度在大灭绝事件后至少400万年始终维持在界线前水平或更高。此项研究揭示的灾后生态系统地理差异表明，K-Pg大灭绝并未造就全域“死寂”的海洋或完全由微生物主导的生态系统，反而至少在部分区域维持了营养级丰度与晚白垩世相当甚至更高的生态系统。