252 / 2025-04-15 20:21:20

Spatio-temporal dynamics of marine primary producer communities in the Permian-Triassic mass extinction: A biomarker perspective

Biomarker,Mass extinction,Primary producer community,Cyanobacteria,Marine algae

Theme 4: Microbial and Biogeochemical Evolution through Time > Session 4b: Roles of Microbes in Shaping Our Habitable Earth

The latest Permian mass extinction (EPME) was accompanied by profound changes in primary producer communities, yet their spatial variation patterns remain largely enigmatic. Using biomarkers, including hopane/sterane (H/S), 2α-methylhopane index (2-MHI) and the relative abundance of C₂₇ and C₂₉ steranes among total steranes (C₂₇/C_27–29 St and C₂₉/C_27–29 St) from 10 worldwide Permian-Triassic boundary (PTB) sections, we reveal three critical patterns: (1) Low-latitude oceans had higher bacterial productivity (higher H/S) than mid-latitudes, suggesting stronger bacterial dominance. Deep waters favored red algae (higher C₂₇ steranes abundance), while shallow waters hosted green algae. These microbial community gradients in PTB oceans were analogous to those observed in modern marine systems. (2) In low-latitude oceans, the first extinction episode of the PTB was marked by increased bacterial abundance relative to algae, along with blooms of cyanobacteria or other anaerobic bacteria and red algae, potentially driven by enhanced terrestrial inputs. The second extinction episode was characterized by even greater bacterial blooms and a decline in red algae, possibly due to early Triassic environmental stressors such as climatic hyperwarming, water column stratification, and ocean acidification. However, such significant microbial community changes were not observed in mid-latitude sections, likely due to higher rates of metazoan extinctions and more sulfidic surface seawaters in low-latitude oceans. (3) In South China, the dramatic shift towards a bacteria-dominated marine system likely caused substantial declines in both net primary and export production, ultimately leading to a productivity collapse from the latest Permian to earliest Triassic. Our biomarker study not only demonstrated the two-episode temporal coupling between microbial community changes, environmental perturbations, and metazoan extinctions, but also revealed their spatial coupling. Furthermore, this research provided new insights into the impact of bacterial and algal community shifts on marine productivity during this critical interval in Earth’s history.