Phytoplankton Blooms on the Barents Shelf, Svalbard, Associated With the Permian–Triassic Mass Extinction

Mid- to higher-latitude shallow marine environments are suggested to serve as refugia for organisms during intervals of rapid environmental change associated with hyperthermals. To understand the role of these environments during hyperthermals, we herein investigate the Permian–Triassic environmental crisis, which led to the most severe mass extinction event in the Phanerozoic. Our analysis of siliciclastic deposits from the Boreal Ocean from Lusitaniadalen, Svalbard, reveals a distinct increase of the lipid biomarkers C₃₃-n-alkylcyclohexane (C₃₃-n-ACH) and phytanyl toluene following the extinction event. This increase does not appear to reflect facies changes. Rather, it coincides with the extinction horizon, and persists into the lowermost Triassic (Griesbachian). Our findings suggest that neither C₃₃-n-ACH nor phytanyl toluene are linked to short periods of photic zone euxinia recorded at Lusitaniadalen, but rather are derived from a specific group of phytoplankton. This indicates that higher-latitude ecosystems may have supported regional blooms of unknown primary producers after the Permian–Triassic mass extinction, thus explaining the selective survival of some marine organisms. We also identify (albeit in lower abundance) C₃₃-n-ACH and its pseudohomologs in northern Italy, which is the first report of n-ACHs in the tropical Tethys region across the Permian–Triassic transition outside of South China, highlighting the wide paleogeographic distribution of this biomarker. Phytanyl toluene, however, is found exclusively in deposits recording higher-latitude ecosystems, and is likely linked to organisms occupying a similar ecological niche as the source organism of C₃₃-n-ACH in these settings.