Marine seismic surveys are a major source of anthropogenic underwater noise, with low-frequency airgun signals capable of propagating over basin-scale distances. This study investigates the long-range propagation of airgun-array signals from the ULYSSE seismic survey conducted in the Aegean Sea and evaluates their potential effects on acoustically sensitive marine fauna at distances of approximately 650 km. Numerical simulations were performed using a combination of an airgun array source model and a range-dependent acoustic propagation model, previously validated against hydrophone recordings from the NEMO-SN1 cabled observatory in the Ionian Sea. To assess ecological relevance, a species-specific acoustic communication framework was developed for fin whales, Mediterranean monk seals, gilthead seabream, and the common cuttlefish. Results show that while received airgun levels at ~650 km are below behavioral disturbance thresholds, long-range propagation substantially reduces communication space through masking—by tens of kilometers for fin whales and to sub-kilometer scales for monk seals and gilthead seabream—while remaining below detection thresholds for cuttlefish. These findings demonstrate that biologically relevant acoustic masking can occur far beyond survey areas, underscoring the importance of accurate source characterization and long-range propagation modeling in environmental impact assessments of seismic surveys.