近日，美国雪城大学Lu, Zunli团队研究了元古代海洋氧梯度纬向反转。2026年1月13日出版的《自然—地球科学》杂志发表了这项成果。

在新元古代-古生代过渡时期，大气和海洋氧合的重大变化引发了包括动物在内的复杂生命的分类多样化和生态扩张。然而，由于当时缺乏对海洋氧气可用性的定量限制，对这一假设的检验受到了阻碍。

研究组展示了海洋碳酸盐中I/Ca比值的空间格局——当地上层海洋中溶解氧的代表——如何提供地球表面氧合状态的指纹。过去20亿年间已公布的I/Ca比率的空间分析研究表明，在元古宙，相对于从中纬度到赤道的氧浓度下降的现代模式，上层海洋氧浓度的纬度梯度是相反的。利用地球系统模型，研究组发现元古代I/Ca纬向格局与低大气氧水平下上层海洋中生物圈控制的氧分布有关，并且I/Ca指标向现代格局的过渡可能对应于今天大气氧浓度的1%左右的阈值。

附：英文原文

Title: A reversed latitudinal ocean oxygen gradient in the Proterozoic Eon

Author: He, Ruliang, Pohl, Alexandre, Zhang, Xingliang, Chang, Chao, Prow-Fleischer, Ashley, Payne, Jonathan L., Xiao, Shuhai, Ridgwell, Andy, Lu, Zunli

Issue&Volume: 2026-01-13

Abstract: Major changes in the oxygenation of the atmosphere and ocean have been suggested to trigger the taxonomic diversification and ecological expansion of complex life, including animals, during the Neoproterozoic–Palaeozoic transition. However, testing this hypothesis is hampered by the paucity of quantitative constraints on the oceanic oxygen availability at that time. Here we show how the spatial pattern of I/Ca ratios in marine carbonates—a proxy for dissolved oxygen in the local upper ocean—provides a fingerprint of the oxygenation state of Earth’s surface. Spatial analyses on published I/Ca ratios spanning the past 2,000 millionyears show that the latitudinal gradient of oxygen concentrations in the upper ocean was reversed in the Proterozoic eon relative to the modern pattern of decreasing oxygen concentrations from the mid-latitudes to the Equator. Using an Earth system model, we identify that the Proterozoic I/Ca latitudinal pattern is associated with a biosphere-controlled distribution of oxygen in the upper ocean at a low atmospheric oxygen level, and the transition to a modern pattern in the I/Ca proxy may correspond to a threshold of around 1% of today’s atmospheric oxygen concentration.

DOI: 10.1038/s41561-025-01896-w

Source: https://www.nature.com/articles/s41561-025-01896-w