Early Palaeozoic ocean anoxia and global warming driven by the evolution of shallow burrowing

Timothy M Lenton,Benjamin J W Mills,Sebastiaan Van De Velde,Simon W Poulton,Filip J R Meysman

doi:10.1038/s41467-018-04973-4

Abstract

The evolution of burrowing animals forms a defining event in the history of the Earth. It has been hypothesised that the expansion of seafloor burrowing during the Palaeozoic altered the biogeochemistry of the oceans and atmosphere. However, whilst potential impacts of bioturbation on the individual phosphorus, oxygen and sulphur cycles have been considered, combined effects have not been investigated, leading to major uncertainty over the timing and magnitude of the Earth system response to the evolution of bioturbation. Here we integrate the evolution of bioturbation into the COPSE model of global biogeochemical cycling, and compare quantitative model predictions to multiple geochemical proxies. Our results suggest that the advent of shallow burrowing in the early Cambrian contributed to a global low-oxygen state, which prevailed for ~100 million years. This impact of bioturbation on global biogeochemistry likely affected animal evolution through expanded ocean anoxia, high atmospheric CO2 levels and global warming.

Highlights

The evolution of burrowing animals forms a defining event in the history of the Earth
The existence of an anoxic oxygen minimum zone (OMZ) along productive continental margin settings has been advocated for the early Cambrian[28]
Samples from within the OMZ would give a very different redox signature compared to samples from oxic shallower and deeper waters

Summary

Introduction

The evolution of burrowing animals forms a defining event in the history of the Earth. We present an evaluation of the global Earth system response to the rise of bioturbation, using a global biogeochemical model (COPSE)[26,27] that simulates the coupled cycling of carbon, oxygen, phosphorus and sulphur.

Results

Conclusion