UC San Diego

The Antarctic Peninsula is undergoing rapid environmental change while several baleen whale species continue to recover from historical exploitation. Understanding how whales respond to this dynamic ecosystem is therefore important for identifying the environmental processes that shape feeding habitat. This study examines the acoustic occurrence of humpback (Megaptera novaeangliae), fin (Balaenoptera physalus), and blue whales (B. musculus) near the South Shetland Islands across three site-year deployments between 2014 and 2016. Passive acoustic recordings were used to quantify humpback whale song and non-song vocalizations, fin whale 20 Hz calls, and blue whale Z- and D-calls. Generalized additive models related acoustic occurrence to environmental variables describing mesoscale circulation, hydrography, primary productivity, and sea ice. Acoustic patterns differed between species, call types, and sites. Fin whale calling showed the clearest seasonality, blue whale Z-calls were persistent year-round, blue whale D-calls occurred in brief episodic events, and humpback whale acoustic occurrence varied strongly among sites. Final models explained 22-69% of deviance, and environmental relationships were predominantly nonlinear. Finite-size Lyapunov exponent (FSLE) magnitude, orientation, or both were retained in 10 of 12 models, making mesoscale structure the most consistently selected environmental component. Chlorophyll a was significant in nine models, while temperature, salinity, and dissolved oxygen anomalies, particularly at 130-222 m, were also frequently retained. These results suggest that baleen whale acoustic occurrence near the South Shetland Islands is associated with interacting patterns of mesoscale circulation, water mass variability, productivity, sea ice, and species- or behavior-specific habitat use.