Coccolithophores, common primary producers in Mesozoic, Cenozoic, and present oceans, are significant components of the earth’s biogeochemical cycles. Being the most productive calcifying organism on earth, their carbonate oozes play a major role in fixing CO₂, thereby forming the most important long‐term CO₂ sink throughout the last 100 Ma. Our understanding of their fossil ancestors is mainly based on data from chalk sequences. Generally, the Cretaceous chalks were deposited at water depths of ≥200 m under stable, pelagic conditions. Here we report on remarkably diverse fossil coccolithophore assemblages from Cenomanian‐Campanian (100‐72 Ma) nearshore deposits, with estimated water depths of ≤40 m. For interpreting the findings in a broader paleoenvironmental context, we additionally analyzed contemporaneous chalk material from the Santonian‐Campanian (86‐72 Ma) interval. Highly diverse coccolithophore associations (50–81 species/sample) characterize the nearshore setting, while the contemporaneous chalk samples are less diverse (43–54 species/sample). The absolute abundances of coccoliths from the nearshore setting are by a factor 2–10 lower than those from the chalk, diversity indices are by 20%–30% higher (Shannon Index = 2.94–3.46) in the nearshore sediments. The presence of highly diverse coccolithophore communities in nearshore settings provides new insights into their paleoecology and evolution and the paleoceanography of the Late Cretaceous. Our data revise the traditional view of coccolithophores being typical open ocean dwellers. Extreme nearshore settings of the Late Cretaceous greenhouse world were characterized by environmental conditions equating those of the hemipelagic realm but supplying a larger variety of ecological niches.

中文翻译：

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晚白垩纪球藻古生物的古生态学：浅海记录的见解

在中生代，新生代和现在的海洋中常见的初级生球藻科，是地球生物地球化学循环的重要组成部分。作为地球上最有生产力的钙化生物，它们的碳酸盐渗出物在固定CO ₂方面起主要作用，从而形成最重要的长期CO _2。在整个100 Ma内下沉。我们对它们的化石祖先的理解主要基于粉笔序列的数据。通常，白垩纪白垩在稳定的中上层条件下沉积在≥200 m的水深中。在这里，我们报道了近海沉积物中Cenomanian-Campanian（100-72 Ma）的化石球石化石组合异常多样，估计水深≤40 m。为了在更广泛的古环境中解释这些发现，我们还分析了桑托尼-坎帕尼亚（86-72 Ma）区间的同期白垩物质。近岸环境的特征是藻类巨石藻协会（50-81个物种/样本），而同期白垩样本的多样性则较低（43-54个物种/样本）。近岸沉积物的硬质岩的绝对丰度比白垩沉积物的绝对丰度低2-10倍，近岸沉积物中的多样性指数高20％至30％（Shannon指数= 2.94至3.46）。近岸环境中高度多样化的球石藻群落的存在为它们的古生态和演化以及晚白垩世的古海洋学提供了新的见解。我们的数据修改了作为典型的开放海洋居民的球墨镜的传统观点。白垩纪晚期温室世界的近岸环境特征是环境条件等同于中海域，但提供了更多种类的生态位。近岸环境中高度多样化的球石藻群落的存在为它们的古生态和演化以及晚白垩世的古海洋学提供了新的见解。我们的数据修改了作为典型的开放海洋居民的球墨镜的传统观点。白垩纪晚期温室世界的近岸环境特征是环境条件等同于中海域，但提供了更多种类的生态位。近岸环境中高度多样化的球石藻群落的存在为它们的古生态和演化以及晚白垩世的古海洋学提供了新的见解。我们的数据修改了作为典型的开放海洋居民的球墨镜的传统观点。白垩纪晚期温室世界的极端近岸环境的特征是环境条件与半地中海域的环境条件相同，但提供了更多种类的生态位。