2025-08-25 ワシントン大学(UW)
An artist’s rendering of a prehistoric jawed fish from the Late Devonian called Dunkleosteus. These sorts of large, active vertebrates evolved shortly after the deep ocean became well-oxygenated.© 2008 Nobu Tamura/CC-BY-SA
<関連情報>
- https://www.washington.edu/news/2025/08/25/how-oxygen-made-the-deep-ocean-home-to-animals/
- https://www.pnas.org/doi/10.1073/pnas.2501342122
中期デボン紀の海洋酸素化が、動物の深海生息地への拡大を可能にした Mid-Devonian ocean oxygenation enabled the expansion of animals into deeper-water habitats
Kunmanee Bubphamanee, Michael A. Kipp, Jana Meixnerová, +8 , and Roger Buick
Proceedings of the National Academy of Sciences Published:August 25, 2025
DOI:https://doi.org/10.1073/pnas.2501342122
Significance
The timing of permanent deep-ocean oxygenation is controversial; early work placed it in the Ediacaran, whereas more recent studies point to the mid-Paleozoic. Establishing the timing of this transition has profound implications for the ecological radiation and evolutionary diversification of metazoan life. Here, we better constrain the Paleozoic history of deep-ocean oxygenation using selenium geochemistry. We do not observe permanent deep-ocean oxygenation until the Middle Devonian (393 to 382 Ma), which overlaps with the “mid-Paleozoic marine revolution” in animal life. Ocean oxygenation thus provides a plausible explanation for the evolutionary changes that are documented in this interval. This rise of oxygen was likely driven by organic carbon burial during the spread of woody vascular plants across landmasses.
Abstract
The oxygenation history of Earth’s surface environments has had a profound influence on the ecology and evolution of metazoan life. It was traditionally thought that the Neoproterozoic Oxygenation Event enabled the origin of animals in marine environments, followed by their persistence in aerobic marine habitats ever since. However, recent studies of redox proxies (e.g., Fe, Mo, Ce, I) have suggested that low dissolved oxygen levels persisted in the deep ocean until the Late Devonian, when the first heavily wooded ligniophyte forests raised atmospheric O2 to modern levels. Here, we present a Paleozoic redox proxy record based on selenium enrichments and isotope ratios in fine-grained siliciclastic sediments. Our data reveal transient oxygenation of bottom waters around the Ediacaran–Cambrian boundary, followed by predominantly anoxic deep-water conditions through the Early Devonian (419 to 393 Ma). In the Middle Devonian (393 to 382 Ma), our data document the onset of permanent deep-ocean oxygenation, coincident with the spread of woody biomass across terrestrial landscapes. This episode is concurrent with the ecological occupation and evolutionary radiation of large active invertebrate and vertebrate organisms in deeper oceanic infaunal and epifaunal habitats, suggesting that the burial of recalcitrant wood from the first forests sequestered organic carbon, increased deep marine oxygen levels, and was ultimately responsible for the “mid-Paleozoic marine revolution.”
