Persistent Environmental Stress Delayed the Recovery of Marine Communities in the Aftermath of the Latest Permian Mass Extinction

Abstract

The aftermath of the latest Permian mass extinction is a key interval for the evolution of modern marine ecosystems. It has been hypothesized that the magnitude of the mass extinction delayed the subsequent recovery, and so to test this, we undertook the highest resolution study to date of the post‐extinction (Griesbachian) microbialite unit on the Great Bank of Guizhou, south China. The benthic community from the microbialite unit is taxonomically diverse when compared to other coeval deposits, recording both inarticulate and articulate brachiopods, crinoids, echinoids, bivalves, gastropods, microconchids, and ostracods. Here we recognize 49 taxa from 4,557 individuals, which raise the known diversity of the Great Bank of Guizhou basal microbialite unit to 84 invertebrate species, making it the most diverse Early Triassic community currently reported. About 89% of the genera are Permian holdovers, whilst only 13% of the species are Permian holdovers. These new data record no temporal trends in the species richness, Simpson diversity, Simpson effective diversity, taxonomic distinctness, functional diversity, or body size of the benthos during the post‐extinction microbialite unit. Nevertheless, the small body sizes of the benthic community, prevalence of opportunistic taxa (e.g., Claraia), and the large lophophoral cavity in the lingulid brachiopod, Sinolingularia huananensis, suggests that these animals lived in a highly stressed environment. We propose that the microbialite unit contains a survival fauna in an interval that represents persistent environmental stress from the latest Permian mass extinction event, associated with deoxygenation, high temperatures, elevated atmospheric carbon dioxide levels (pCO2), and elevated primary productivity.

Facies selectivity of benthic invertebrates in a Permian/Triassic boundary microbialite succession: Implications for the “microbialite refuge” hypothesis

“…Studies of living microbialites have observed metazoans exploiting local oxygen refugia within the microbialites (e.g., Gingras, Lalond, Amskold, & Konhauser, 2007;Rishworth, Perissinotto, & Bird, 2016;Tarhan, Planavsky, Laumer, Stolz, & Reid, 2013). These metazoans, however, are typically softbodied, infaunal, and motile, which is not consistent with the epifaunal, stationary lifestyles of the benthic communities reported from the Great Bank of Guizhou (Foster et al, 2019). In addition, if the microbial mats were a preferable environment, we would expect that the microbial facies would contain a greater species richness and abundance than the surrounding non-microbial rocks, which was not observed in this study (Figures 4 and 5).…”

“…Nevertheless, the detailed investigation of this study records a greater diversity and abundance of fossils in the non‐microbial facies and non‐microbial fabrics found within the microbial facies than the microbial fabrics themselves (Figures and ). Furthermore, the microbialite samples investigated by (Foster, Lehrmann, et al., ) using the mechanical disaggregation method rarely yielded enough specimens (i.e., >50 specimens) for quantitative analysis. Most of the specimens within the microbialites are also disarticulated, and randomly orientated, and are thus inferred to have been transported into the microbialite framework (Figure ).…”

“…Systematic studies of the species that occur in the microbialites also find that at both the genus and species levels the microbialites did not contain a unique suite of benthic invertebrates, and these taxa are also mainly characterized as cosmopolitan taxa (Foster et al, 2019;Hautmann et al, 2015). This observed difference between (Foster et al, 2015;Hips, 1996), Werfen Formation (Foster, Danise, Price, & Twitchett, 2017;a), and Virgin Limestone Formation (Hofmann, Hautmann, Wasmer, & Bucher, 2013;Mata & Bottjer, 2009).…”

“…The recent findings of ecologically complex metazoan communities in shallow settings have also challenged the view that all shallow settings experienced anoxia (Beatty, Zonneveld, & Henderson, ; Twitchett, Krystyn, Baud, Wheeley, & Richoz, ), and relatively diverse metazoan communities have also been associated with microbialite successions (Forel, Crasquin, Kershaw, & Collin, ; Foster, Lehrmann, Yu, Ji, & Martindale, ; Hautmann et al., ; Yang et al., ). This has led some workers to suggest that other environmental stressors, such as high temperatures, are more significant factors than anoxia for extinctions in shallow settings (Foster, Lehrmann, et al., ; Song et al., ). Where microbialite successions had developed, putative coccoid fossils and lipid biomarker evidence suggest that the microbialites were produced by cyanobacterial mats (Heindel et al., ; Wu et al., ; Xie et al., ).…”

Suppressed competitive exclusion enabled the proliferation of Permian/Triassic boundary microbialites

“…In all of the investigated localities, independent of region and stratigraphic level, the microbialites contain a high‐abundance assemblage of ostracods, microconchids, gastropods, bivalves and foraminifera, which have already been previously recognized (Baud et al , ; Forel et al , , ; Yang et al , ; Foster et al , ). These results show significant separation between the different investigated regions with the samples plotting into three main groups (Figure A).…”