Department of Geosciences, Virginia Tech, Blacksburg, VA, USA.
Global Change Center, Virginia Tech, Blacksburg, VA, USA.
Sci Adv. 2023 Mar 22;9(12):eade9647. doi: 10.1126/sciadv.ade9647.
The early Neoproterozoic Era witnessed the initial ecological rise of eukaryotes at ca. 800 Ma. To assess whether nitrate availability played an important role in this evolutionary event, we measured nitrogen isotope compositions (δN) of marine carbonates from the early Tonian (ca. 1000 Ma to ca. 800 Ma) Huaibei Group in North China. The data reported here fill a critical gap in the δN record and indicate nitrate limitation in early Neoproterozoic oceans. A compilation of Proterozoic sedimentary δN data reveals a stepwise increase in δN values at ~800 Ma. Box model simulations indicate that this stepwise increase likely represents a ~50% increase in marine nitrate availability. Limited nitrate availability in early Neoproterozoic oceans may have delayed the ecological rise of eukaryotes until ~800 Ma when increased nitrate supply, together with other environmental and ecological factors, may have contributed to the transition from prokaryote-dominant to eukaryote-dominant marine ecosystems.
早新元古代（约 800 百万年前）见证了真核生物的最初生态崛起。为了评估硝酸盐的可用性是否在这一进化事件中发挥了重要作用，我们测量了华北早元古代（约 1000 百万年前至约 800 百万年前）的淮北群海相碳酸盐的氮同位素组成（δN）。这里报告的数据填补了 δN 记录中的一个关键空白，并表明早新元古代海洋中存在硝酸盐限制。元古代沉积 δN 数据的汇编表明，约 800 百万年前，δN 值呈阶梯式上升。箱式模型模拟表明，这种阶梯式上升可能代表海洋硝酸盐可用性增加了约 50%。早新元古代海洋中硝酸盐的有限可用性可能延迟了真核生物的生态崛起，直到约 800 百万年前，随着硝酸盐供应的增加，以及其他环境和生态因素的共同作用，可能促成了从以原核生物为主导的海洋生态系统向以真核生物为主导的海洋生态系统的转变。
