Origins of natural and anthropogenic sounds in a coastal, seasonally ice-covered, Antarctic marine soundscape

Baseline characterisation of the acoustic underwater environment is integral to understanding changes in the soundscape of a location. We used passive acoustic monitoring to investigate the soundscape of a seasonally ice-covered, shallow marine environment close to a permanently occupied research station in Prydz Bay, East Antarctica, from July (winter ice cover) 2021 through to February (summer open water) 2022. We applied a suite of automated detectors to detect sounds, with manual analysis of a subset of recordings to validate automated detections and characterise detector performance. From July until late November, the landfast ice cover had a dampening effect on mean daily ambient underwater sound pressure levels. The anthropophony of the ice-covered environment included contributions from aircraft landings and the movements of over-ice vehicles. The biophony was most influenced by the sounds of Weddell, crabeater and leopard seals and Antarctic minke whales. Mean daily sound levels increased immediately as the ice cover decreased and the sea surface became exposed to the effects of wind. The soundscape of the open-water/drifting pack-ice environment then altered to include noise from ship and small boat activities and vocalisations of killer whales and leopard and Ross seals. The results demonstrate a study site with high seasonality in natural sound sources and an unprecedented contribution of noise from human activities during the period of ice cover. There is likely a year-round contribution of anthropogenic noise to the Antarctic coastal marine environment close to research stations that are often co-located with regional hot-spots in faunal occurrences.