Phosphorus Cycle and Primary Productivity Changes in the Tethys Ocean During the Permian-Triassic Transition: Starving Marine Ecosystems

Johann Müller,Alicia Fantasia,Fen Yang,Yadong Sun,Michael Joachimski

doi:10.3389/feart.2022.832308

Abstract

The ultimate cause(s) of the end-Permian mass extinction (∼252 Ma ago) has been disputed. A complex interplay of various effects, rather than a single, universal killing mechanism, were most likely involved. Climate warming as consequence of greenhouse gas emissions by contemporaneous Siberian Traps volcanism is widely accepted as an initial trigger. Synergetic effects of global warming include increasing stratification of the oceans, inefficient water column mixing, and eventually low marine primary productivity culminating in a series of consequences for higher trophic levels. To explore this scenario in the context of the end-Permian mass extinction, we investigated sedimentary total organic carbon, phosphorus speciation as well as nickel concentrations in two low-latitude Tethyan carbonate sections spanning the Permian-Triassic transition. Total organic carbon, reactive phosphorus and nickel concentrations all decrease in the latest Permian and are low during the Early Triassic, pointing to a decline in primary productivity within the Tethyan realm. We suggest that the productivity collapse started in the upper C. yini conodont Zone, approximately 30 ka prior to the main marine extinction interval. Reduced primary productivity would have resulted in food shortage and thus may serve as explanation for pre-mass extinction perturbations among marine heterotrophic organisms.

Highlights

Anthropogenic global warming is expected to decline marine primary productivity with severe consequences for global ecosystems as well as for mankind (Mora et al, 2013)
Downward trends in sedimentary productivity proxies (TOC, Niexcess, and Preact) from two Tethyan successions suggest a reduction of the organic matter sinking flux due to a decrease of marine primary productivity from the Lopingian to the Early Triassic
This commenced in the upper C. yini conodont Zone 30 ka before the main marine extinction level

Summary

Introduction

Anthropogenic global warming is expected to decline marine primary productivity with severe consequences for global ecosystems as well as for mankind (Mora et al, 2013). This is because climate warming likely slows down the meridional overturning circulation, decreases winddriven coastal and equatorial upwelling intensity but increases thermal stratification thereby inhibiting the mixing of shallow and deep waters (Behrenfeld et al, 2006). Bulk primary production in today’s oceans is mainly confined to equatorial and shelf areas where upwelling systems replenish nutrients to the euphotic zone (Boyd et al, 2014). 1) upwelling systems replenish phosphorus (P) to the euphotic zone 2) organic matter remineralization consumes oxygen and 3) seafloor hypoxia favors P recycling from sediments (Figure 1; e.g., Ingall et al, 1993). If vertical mixing weakens due to warming, the nutrient P will be trapped in deeper waters where it cannot be utilized by phytoplankton (Behrenfeld et al, 2006), leading to a food shortage for higher trophic levels

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Conclusion