COMPLEX MARINE ECOSYSTEM ENGINEERING FOLLOWING THE END-PERMIAN MASS EXTINCTION

The end-Permian mass extinction was the most severe of the ‘Big 5’ Phanerozoic mass extinction events and is considered to be analogous in many ways to our current climate change and biotic crisis. In the aftermath of the extinction event, full biotic recovery was delayed for millions of years until the Middle Triassic. Here, we present the first analysis of changes in ecosystem engineering behaviors across a mass extinction boundary. Understanding changes in marine ecosystem engineering behaviors (those which allow organisms to create, modify, and maintain habitable environments) across the Permian-Triassic boundary may also help us understand the nature of biotic recovery during the Early Triassic. Specifically, the trace fossil record is a useful tool to study how marine bioturbators may have redistributed nutrients to the benthos, changed sediment chemistry, and created new ecospace. We compiled trace fossil data from previously published literature and the Paleobiology Database to analyze burrowing ecosystem engineering behavior across the Permian-Triassic boundary in terms of tiering, ecosystem engineering impact (Herringshaw et al. 2017), and ecosystem engineering mode (Minter et al. 2017). We report two key findings: first, that post-extinction bioturbation was more limited to the shallow and semi-infaunal tiers, and second, that high-impact and complex ecosystem engineering behaviors still persisted locally after the end-Permian mass extinction. Therefore, while environmental conditions may have limited deeper burrowing, complex ecosystem engineering behaviors which represent the most potential for associated environmental change were still present in the Early Triassic, at least locally. Bioturbation may have played a critical role in maintaining local environments less affected by extinction conditions or even ameliorated less habitable environments for further ecosystem recovery.