Co-evolution of marine life and increased oxygen levels

Researchers from a number of institutions in the US and UK have confirmed that rising oceanic and atmospheric oxygen levels co-evolved with marine life hundreds of millions of years ago.Wanyi Lu, a Ph.D. candidate studying under Associate Professor Zunli Lu (no relation) in the College of Arts and Sciences of Syracuse University, is the lead author of a ground-breaking paper in Science magazine.

The paper stems from a multi-year, multi-national research effort led by Zunli Lu that rethinks the causes and impacts of increased oxygenation on continental shelves during the Phanerozoic Aeon, which began more than 542 million years ago.

Central to the team’s research was a geochemical proxy that Lu pioneered in 2010, when he was a post-doctoral research fellow at Oxford working with Ros Rickaby and Hugh Jenkyns*.  Using a novel approach based on iodine geochemistry, he and his colleagues measured the ratio of iodine to calcium in carbonate minerals and fossils, which is dependent on the degree of oxygenation of the waters in which they were formed.

The iodine data are consistent with a major rise in atmospheric oxygen during the Devonian Period around 400 million years ago, although upper-ocean oxygen levels did not stabilize at near-modern conditions until 200 million years ago around Triassic–Jurassic boundary time, when larger eukaryotic plankton dominated the world’s oceans.   This fundamental change in eukaryotes led to a greater re-mineralization depth of organic matter and, ultimately, to the “resiliently oxygenated” upper ocean that exists today.

Paper:  Late inception of a resiliently oxygenated upper ocean, by Wanyi Lu, Andy Ridgwell, Ellen Thomas, Dalton S. Hardisty, Genming Luo, Thomas J. Algeo, Matthew R. Saltzman, Benjamin C. Gill, Yanan Shen, Hong-Fei Ling, Cole T. Edwards, Michael T. Whalen, Xiaoli Zhou, Kristina M. Gutchess, Li Jin, Rosalind E. M. Rickaby, Hugh C. Jenkyns, Timothy W. Lyons, Timothy M. Lenton, Lee R. Kump and Zunli Lu was published in Science on 31 May 2018.
DOI: 10.1126/science.aar5372

Syracuse University News Article: Scientists Rethink Co-Evolution of Marine Life, Oxygenated Oceans

*Iodine to calcium ratios in marine carbonate as a paleo-redox proxy during oceanic anoxic events, by Zunli Lu, Hugh C. Jenkyns and Rosalind E.M. Rickaby, was published in Geology (2010) 38 (12): 1107-1110, . DOI: https://doi.org/10.1130/G31145.1

Image: Outcrop of Triassic–Jurassic boundary strata deposited when the oceans assumed the oxygenation structure that they have today.   St Audries Bay, Somerset coast.