Earth-Science Reviews 212 (2021) 103382 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev Review Article Permian–Triassic non-marine algae of Gondwana—Distributions, natural T affinities and ecological implications ⁎ Chris Maysa,b, , Vivi Vajdaa, Stephen McLoughlina a Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden b Monash University, School of Earth, Atmosphere and Environment, 9 Rainforest Walk, Clayton, VIC 3800, Australia ARTICLE INFO ABSTRACT Keywords: The abundance, diversity and extinction of non-marine algae are controlled by changes in the physical and Permian–Triassic chemical environment and community structure of continental ecosystems. We review a range of non-marine algae algae commonly found within the Permian and Triassic strata of Gondwana and highlight and discuss the non- mass extinctions marine algal abundance anomalies recorded in the immediate aftermath of the end-Permian extinction interval Gondwana (EPE; 252 Ma). We further review and contrast the marine and continental algal records of the global biotic freshwater ecology crises within the Permian–Triassic interval. Specifically, we provide a case study of 17 species (in 13 genera) palaeobiogeography from the succession spanning the EPE in the Sydney Basin, eastern Australia. The affinities and ecological im- plications of these fossil-genera are summarised, and their global Permian–Triassic palaeogeographic and stra- tigraphic distributions are collated. Most of these fossil taxa have close extant algal relatives that are most common in freshwater, brackish or terrestrial conditions, and all have recognizable affinities to groups known to produce chemically stable biopolymers that favour their preservation over long geological intervals. However, these compounds (e.g., sporopollenin and algaenan) are not universal, so the fossil record is sparse for most algal groups, which hinders our understanding of their evolutionary histories. Owing partly to the high preservational potential of Zygnematophyceae, a clade of freshwater charophyte algae and sister group to land plants, this group has a particularly diverse and abundant Permian–Triassic fossil record in Gondwana. Finally, we review and contrast the marine and continental algal records of the global biotic crises within the Permian–Triassic interval. In continental settings, Permian algal assemblages were broadly uniform across most of southern and eastern Gondwana until the EPE; here, we propose the Peltacystia Microalgal Province to collectively describe these distinct and prolonged freshwater algal assemblages. In the immediate aftermath of the EPE, relative increases in non-marine algae have been consistently recorded, but the distributions of prominent taxa of Permian freshwater algae became severely contracted across Gondwana by the Early Triassic. We highlight the paucity of quantitative, high-resolution fossil evidence for this key group of primary producers during all biotic crises of the Permian and Triassic periods. This review provides a solid platform for further work interpreting abundance and diversity changes in non-marine algae across this pivotal interval in evolutionary history. 1. Introduction et al., 2004, 2012). As such, the fossil records of these groups may provide independent proxies of specific environmental changes, but Aquatic algae provide excellent measures of past and present only if their natural affinities can be established reliably. changes in marine and terrestrial environments. Nutrient, salinity, pH The Permian–Triassic algal record reveals major changes in regional and temperature changes can all lead to significant fluctuations in algal and global environmental conditions. Several distinct and abrupt ex- abundances within modern terrestrial waterways (Wehr and Sheath, tinction pulses are recognised through this interval (Retallack, 2013; 2015). Some groups are extremely sensitive to specific aquatic para- Wignall, 2015), such as the end-Guadalupian event (ca 259.8 Ma; meters; for example, the development of ‘blooms’ of zygnematacean Rampino and Shen, 2019) and the Smithian-Spathian event (ca 249 Ma; algae in lakes and rivers under low-pH conditions (Turner et al., 1995; Lindström et al., 2019), all of which have been associated with a dis- Kleeberg et al., 2006; Watson et al., 2015), or of prasinophyte algae in tinct pulse of marine extinctions. This interval also includes the most marginal marine settings enriched in nutrients (O'Kelly et al., 2003; Not extreme mass extinction event of all, the end-Permian extinction (EPE), ⁎ Corresponding author at: Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden. E-mail address: [email protected] (C. Mays). https://doi.org/10.1016/j.earscirev.2020.103382 Received 6 July 2020; Received in revised form 21 September 2020; Accepted 22 September 2020 0012-8252/ © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/). C. Mays, et al. Earth-Science Reviews 212 (2021) 103382 which resulted in the loss of > 80% of marine species (Stanley, 2016) interpretations for the most common forms of algae and possible algae and an unparalleled overturn of terrestrial plants (McElwain and (acritarchs) found in non-marine Permian and Triassic strata of Punyasena, 2007; Cascales-Miñana et al., 2016) and animals (Ward Gondwana. et al., 2005). The abundances of organic microfossils have long been employed as indicators of regional (e.g., Micrhystridium evansii; Price, 1983, 1997) or global (e.g., Reduviasporonites; Eshet et al., 1995; 2. Permian–Triassic palaeoenvironmental conditions of eastern Visscher et al., 1996) environmental changes, thus serving as key Australia biostratigraphic markers for the Permian and Triassic periods. Simi- larly, modifications in algal (or acritarch) morphology have been uti- The stratigraphic successions of eastern Australia provide a near- lised to signal changes in local marine conditions (van Soelen et al., continuous record of Permian (Fielding et al., 2008; Phillips et al., 2018; Lei et al., 2019). Furthermore, distinct changes in algal com- 2017) to Triassic (Banks, 1978; Totterdell et al., 2009) near-shore munities have been identified concurrent with the EPE from almost marine to continental sedimentation. These strata are preserved pri- every examined marine succession (e.g., Twitchett et al., 2001; Grice marily in the Bowen-Gunnedah-Sydney basin complex (BGSBC), a large et al., 2005; Grice et al., 2007; Schneebeli-Hermann et al., 2012b; van meridional foreland system encompassing > 160,000 km2 of Queens- Soelen and Kürschner, 2018), although probably not all of these strictly land and New South Wales, Australia (Fig. 1). In the Cisuralian to represent ‘algal blooms’ since the absolute concentrations of cysts tend Guadalupian epochs (early to middle Permian), the basin system un- to decline across the EPE strata in some cases (Shen et al., 2013; Lei derwent broad extension and thermal subsidence, which facilitated the et al., 2019). accommodation of thick (locally > 10 km) sedimentary packages Linking the specific environmental parameters undergoing change (Korsch and Totterdell, 2009). The early to middle Permian subsidence to algal diversities and abundances has been hindered by ambiguous phase is represented by a transgressive trend and the formation of an affinities and ecological tolerances of the algae. Tappan (1980) carried epicontinental shelf, with shallow marine to coastal plain environments out a major review of fossil algae and their probable biological affi- prevalent (Fielding et al., 2001). This marine phase was followed by a nities, and further significant advances were made for Palaeozoic and regression from the Lopingian (late Permian) to Early Triassic caused by Triassic groups by Colbath and Grenfell (1995) and Brenner and Foster foreland thrust loading, in addition to sediment loading by erosion of an (1994), respectively. Since that time, significant advances have been active volcanic arc to the east, the New England Orogen (Rosenbaum, made to our understanding of algal chemistry and wall microstructures 2018). This regression led to the establishment of predominantly non- (e.g., de Leeuw et al., 2006; Baudelet et al., 2017), thus facilitating marine environments across the BGSBC from the Lopingian to Middle direct comparisons between fossils and their extant counterparts (e.g., Triassic (Fielding et al., 2001). Broad alluvial plains hosting forested Moczydłowska and Willman, 2009; Steemans et al., 2010; mires (in the Lopingian) and ephemeral lakes (in the Early Triassic) Moczydłowska et al., 2011), and highlighting the contrasting pre- with an overall southward fluvial drainage system prevailed during this servational potential of algae groups over geological time (Versteegh interval (Cowan, 1993; Herbert, 1997; Fielding et al., 2020). The EPE and Blokker, 2004). Furthermore, molecular phylogenies of extant represented a major biotic collapse in the late Lopingian, and the onset groups have provided a robust framework for interpreting the evolu- of continental ecosystem collapse likely preceded the Permian–Triassic tionary histories of green algae (Leliaert et al., 2012; Del Cortona et al., boundary by > 300,000 years based on CA-ID-TIMS dating of zircons 2020). from tuff beds intercalated with the fossiliferous succession in both Here, we document algal occurrences through