Plant mutations and ecosystem disruption induced by toxic metals and climatic warming during the end-Permian extinction

The investigation of mass extinction events is paramount for understanding the resilience of ecosystems to a range of abiotic stressors, such as climate change and environmental toxicity. Insights gained from such research may provide the means to mitigate the risks of analogous anthropogenically-driven crises in the modern World. At the end of the Permian Period, rapid climatic change and oceanic acidification triggered by Siberian Traps volcanism resulted in the most severe mass extinction in Earth’s history. The event culminated in a major biotic crisis in the marine realm, but its impact on terrestrial ecosystems, particularly plant communities, remains poorly known.

While a mass extinction in plants at the Permian-Triassic Boundary (PTB) is debatable (e.g. Nowak et al., 2019), there is mounting palynological evidence for mutation among various plant lineages. Recent geochemical studies of several PTB localities globally have revealed an abrupt increase in the levels of various volcanically-derived heavy metals, including As, Co, Hg, and Ni. Despite being well-documented as mutagenic agents among modern plants, their role as potential mutagens during the end-Permian has not been previously assessed.

Here we present the results of a high resolution palynological and geochemical study from the PTB in the Norwegian Arctic. Out data shows the transient disruption of plant communities without significant turnover in species or decrease in diversity, consistent with other records from the Boreal Realm (e.g. Schneebeli-Hermann et al., 2017). However, the abrupt appearance and high abundance of aberrant spores and pollen, coinciding with elevated concentrations of As, Co, Hg, and Ni, is interpreted as the first evidence for heavy metal-induced mutagenesis during the EPE. We propose that biomagnification of these elements may have been a significant yet unrecognised driver for the end-Permian biotic crisis.

References:

• Nowak, H. Schneebeli-Hermann, E., Kustatscher, E. 2019. No mass extinction for land plants at the Permian-Triassic transition. Nature Communications 10, Article number 384.
• Schneebeli-Hermann, E., Hochuli, P.A., Bucher, H. 2017. Palynofloral associations before and after the Permian-Triassic mass extinction. Global Planetary Change 37(1), 178-195.