Reconstructing Environmental and Microbial Ecosystem Changes Across the Permian–Triassic Mass Extinction at Lusitaniadalen, Svalbard

Abstract The Permian–Triassic environmental crisis triggered fundamental changes in marine ecosystems, culminating in the most severe biodiversity crisis of the Phanerozoic. Yet, the environmental and geochemical conditions governing the crisis and ecosystem recovery remain debated. The sedimentary succession at Lusitaniadalen, Svalbard, deposited in the Permo–Triassic Boreal Realm, offers insights into mid‐paleolatitudinal, shallow marine ecosystem responses. In a multiproxy study combining lipid biomarker and geochemical data, we reconstruct environmental conditions and microbial ecosystem dynamics across the Permian–Triassic environmental crisis. Generally low enrichments of the redox‐sensitive trace elements Re, V, U, and Mo, predominantly negative Ce anomalies, and a pristane/phytane ratio >1 suggest mainly oxic conditions in the investigated interval. However, while transient dysoxic to anoxic episodes recorded across the extinction horizon support that deoxygenation contributed to the severity of the mass extinction at this Boreal site, the earlier occurrence of similar episodes of deoxygenation in the late Permian challenges the hypothesis of global anoxia as the sole extinction driver across paleolatitudes. Lipid biomarkers reveal a post‐extinction increase in abundance of long‐chain n ‐alkanes derived from terrestrial plants due to increased terrigenous discharge into shallow marine settings across this interval. Pristane and phytane, lipid biomarkers predominantly derived from chlorophyll, reveal a pronounced regional increase in primary productivity following the environmental crisis. The composition of the lipid biomarker inventory recorded in early Griesbachian strata is distinct from the pre‐crisis composition, and did not recover towards the pre‐crisis state within the studied interval.