Bioindicators of severe ocean acidification are absent from the end-Permian mass extinction

Abstract

The role of ocean acidification in the end-Permian mass extinction is highly controversial with conflicting hypotheses relating to its timing and extent. Observations and experiments on living molluscs demonstrate that those inhabiting acidic settings exhibit characteristic morphological deformities and disordered shell ultrastructures. These deformities should be recognisable in the fossil record, and provide a robust palaeo-proxy for severe ocean acidification. Here, we use fossils of originally aragonitic invertebrates to test whether ocean acidification occurred during the Permian–Triassic transition. Our results show that we can reject a hypothesised worldwide basal Triassic ocean acidification event owing to the absence of deformities and repair marks on bivalves and gastropods from the Triassic Hindeodus parvus Conodont Zone. We could not, however, utilise this proxy to test the role of a hypothesised acidification event just prior to and/or during the mass extinction event. If ocean acidification did develop during the mass extinction event, then it most likely only occurred in the latest Permian, and was not severe enough to impact calcification.

Shallow-water temperature seasonality in the middle Cretaceous mid-latitude northwestern Pacific

“…The needle-like crystals of chlorite present in the shell were considered pseudomorphs of biogenic aragonite produced by diagenetic alteration based on their morphology, distribution, and orientation. Silicification of biogenic carbonate with preserved microstructures has been observed in other areas (Suzuki et al, 1998;Zakhera et al, 2001;Foster et al, 2022). The arrangement of growth lines and crystals in the outermost part of the outer shell layer of A. pseudoplana is similar to some venerid bivalves (Chioninae and Mercenaria stimpsoni: Shimamoto, 1986); its shell microstructure is similar to the arcticid bivalve Arctica islandica (Dunca et al, 2009;Höche et al, 2021).…”

Response of siliceous marine organisms to the Permian-Triassic climate crisis based on new findings from central Spitsbergen, Svalbard

“…2). The concretions come from interbeds of siltstones and very fine sandstones, where the heterolithic beds are bioturbated by shallow burrowing Skolithos and Arenicolites and both record ripple structures and a diverse fauna, which indicate deposition in an oxygenated, shallow, marine setting (Foster et al, 2017; 2022).…”

Response of Siliceous Marine Organisms to the Permian‐Triassic Climate Crisis Based on New Findings From Central Spitsbergen, Svalbard

“…The radiolarians and sponges from these sections are, therefore, well-constrained as belonging to the latest Changhsingian to early Griesbachian Clarkina meishanensis-Hindeodus parvus Conodont Zones (Mørk et al, 1999;Zuchuat et al, 2020) (Figure 2). The siliceous fossils come from concretions within interbeds of siltstones and very fine sandstones, where the heterolithic beds are bioturbated by shallow burrowing Skolithos and Arenicolites and both record ripple structures and a diverse fauna, which indicate deposition in an oxygenated, shallow, marine setting (Foster et al, 2017(Foster et al, , 2022.…”