58-7 Disturbed? Probably: Investigation into how Anoxia and Ocean Acidification Affected the Functional Diversity of Late Triassic Marine Ecosystems Across the Norian–Rhaetian Boundary

Session: Future Leaders in Paleontology

Presenting Author:

Fiorella Ramirez-Guasp

Authors:

Ramirez-Guasp, Fiorella S.¹, Tackett, Lydia Schiavo², Banker, Roxanne M.W.³, Dineen, Ashley A.⁴, Roopnarine, Peter D.⁵, Tyler, Carrie L.⁶

(1) Department of Geoscience, University of Nevada, Las Vegas, Las Vegas, NV, USA, (2) Missouri State University, Springfield, MO, USA, (3) Providence College, Providence, RI, USA, (4) UC Museum of Paleontology, Berkeley, CA, USA, (5) California Academy of Sciences, Invertebrate Zoology & Geology, San Francisco, CA, USA, (6) University of Nevada, Las Vegas, NV, USA,

Abstract:

Functional diversity is crucial to ecosystem stability and resilience and is increasingly used to quantify how ecosystems respond to disturbances. Here we explore changes in ecosystem functioning across the Norian–Rhaetian boundary (NRB; ~205 Ma) in the Late Triassic to better help us understand the effects of anoxia and ocean acidification, as well as predict how modern marine ecosystems may respond in the future. Global Norian and Rhaetian marine assemblages were compared using species occurrences from the Paleobiology Database. A total of 775 species were assessed to determine four functional traits (i.e., tiering, motility, feeding, and mineralogy) which were used to calculate functional entities (unique groupings of traits), functional redundancy, functional vulnerability, and functional over-redundancy to identify changes in functional diversity. The Norian assemblage consisted of 672 species and yielded 45 functional entities, while the Rhaetian assemblage contained 346 species and yielded only 36 functional entities. Overall, the way species were distributed among functions differed (Spearman’s Rank Correlation; ρ = 0.68, p < 0.001), and functional redundancy (14.93 in the Norian and 9.61 in the Rhaetian), functional vulnerability (0.42 and 0.33), and functional over-redundancy (0.63 and 0.57) all decreased over time. The loss of nine functional entities is notable, as the NRB is not considered a mass extinction event, and suggests that these disturbances were consequential enough to cause ecosystem restructuring, potentially weakening the ecosystem prior to the end-Triassic mass extinction. In addition, the decrease in functional richness corresponded to a substantial decrease in the number of species. This suggests that even with decreased functional redundancy, many species occupied similar functional groups through time, buffering the ecosystem from functional losses. Future work aims to focus on functional diversity changes at high spatial and temporal resolution, using the Triassic shallow marine coral reefs from Panthalassa now found in New York Canyon, Nevada. Understanding restructuring that occurs in the marine fossil record is beneficial for understanding modern marine ecosystem restructuring in response to anoxia and acidification today.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8500

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