Ancient โฃOxygen โคSurge Enabled Life to Thrive in Deep Ocean Habitats
SEATTLE – A surge in oceanic oxygen levelsโค roughly 400 million โyears ago during โthe Middle Devonian period dramatically altered marine ecosystems, allowing animals to colonizeโค and diversify โฃin deeper ocean environments, according to new researchโค published August 25, 2025, โขin the Proceedings of the Nationalโข Academy of Sciences.โ The study,ledโ by Kunmanee Bubphamanee and Michael A.Kipp of the University of Washington,โ links this oxygenation event to the rise of woody โplants and offers a cautionary tale โคfor modern oceans facing oxygen depletion.
Researchers found the increase in oxygen coincided with theโ “mid-Paleozoic marine revolution,” a period of notable evolutionary change. As oxygen became established in deeper waters, jawed fish (gnathostomes) and other animals began โคto invade and flourish in โคthese previouslyโ uninhabitable zones. โขThe fossil record also suggests animals grew larger, perhaps due to the increased oxygen availability.
“Our thinking is that, asโ these woody plants increased in number, thay released more oxygen intoโ the air, which led to more oxygen inโ deeper ocean โขenvironments,” explained Kipp, โwho began the research as โa Ph.D. student at the University of Washington.
Theโข team โขalso investigated an earlier, temporary oxygenation event during the Cambrian period, finding that aโข subsequent drop in oxygen levels hindered the expansion of marine life into โคdeeper waters.
The findings have implicationsโฃ for contemporary ocean health. While modernโฃ oceans generally maintain oxygen levels in equilibrium with the atmosphere, localized oxygen depletion is occurring due to nutrient runoff from fertilizers and industrial activity, fuelingโข plankton blooms that consume oxygen as they decay.
“This work shows veryโ clearly the link between oxygen and animal life in the ocean. Thisโฃ was a balance โstruckโ about 400 million years ago, and it wouldโค be a shame to disrupt it today โฃin a matter of decades,” Kipp warned.
The research was supported by an NSF Graduate Research Fellowship, an Agouron Institute Postdoctoral Fellowship, and the NASA Astrobiology Institute’s โฃVirtual Planetary Laboratory.