The Permian-Triassic (P-T) transition witnessed the most severe biocrisis in the Phanerozoic, yet microbial community dynamics across this interval remain poorly constrained in key regions of the Paleotethys. Here, we present high-resolution hydrocarbon biomarker records from the Zal section (NW Iran) to reconstruct ecological disturbances and microbial responses from the Lopingian to Early Triassic. Our results reveal: (1) Elevated 2 alpha methylhopane index suggests a microbial community shift from eukaryotic green/red algae to bacteria, with cyanobacterial blooms at the extinction interval; (2) Repeated episodes of bottom-water anoxia and watercolumn stratification, indicated by a high gammacerane index, alongside persistent euxinia as shown by low pristane/phytane ratios and a strong even-over-odd predominance in n-alkanes; and (3) Enhanced terrestrial inputs from wildfires, recorded by pyrogenic polycyclic aromatic hydrocarbons, and soil erosion, marked by elevated dibenzofuran and dibenzothiophene, implicating land-derived nutrients in marine eutrophication. Critically, biomarker anomalies coincide with negative delta 13C excursions and mirror trends in South China, supporting the interpretation of synchronous ecological degradation across the Paleotethys. These findings underscore volcanism-driven terrestrial collapse and expanded marine anoxia as pivotal amplifiers of the P-T biocrisis.