Acoustic habitat of an oceanic archipelago in the Southwestern Atlantic

• Autonomous acoustic monitoring occurred in Trindade-Martin Vaz Archipelago.
• Underwater noise levels were measured and compared between summer and winter.
• Fish and humpback whales vocalizations were detected and compared between seasons.
• The archipelago's acoustic habitat is dominated by sounds of biological origin.
• Results indicate the archipelago's importance to humpback whales during winter.

Underwater soundscapes can be highly variable, and in natural conditions are often dominated by biological signals and physical features of the environment. Few studies, however, focused on oceanic islands soundscapes. Islands in the middle of ocean basins can provide a good example of how untouched marine soundscapes are. Autonomous acoustic recordings were carried out in two different seasons in Trindade-Martin Vaz Archipelago, Southwestern Atlantic, providing nearly continuous data for both periods. Sound levels varied daily and between seasons. During summer, higher frequencies were noisier than lower frequencies, with snapping shrimp being the dominating sound source. During winter, lower frequencies were noisier than higher frequencies due to humpback whale constant singing. Biological signal detection had a marked temporal pattern, playing an important role in the soundscape. Over 1000 humpback whale sounds were detected hourly during winter. Fish vocalizations were detected mostly during night time during both summer and winter. The results show an acoustic habitat dominated by biological sound sources and highlight the importance of the island to humpback whales in winter.