Temporal dynamics of the summer soundscape near oil platforms of the shallow continental shelf off Louisiana.

The northern Gulf of Mexico contains productive soft bottom environments with numerous oil rigs that contain epibionts and reef associated fishes. Soundscapes at these structures may provide insight on diel and seasonal animal activity near these habitats and influences of stressors such as vessel noise, hypoxia, and storms. Yet, bioacoustics of this area remains understudied. We used passive acoustic and abiotic monitoring to better understand biological soundscapes in the shallow continental shelf environment off Louisiana, U.S.A. at two oil rigs off Terrebonne Bay from June-September 2021. We observed four nocturnal chorus types that were distinguished by frequency spectra and temporal patterns associated with different astronomical variables: the 0.5-1 kHz Late Chorus occurred increasingly later each night; the 0.5-1 kHz Early Chorus appeared mid-summer, in early evening, and peaked closer to sunset as the season progressed; the 1-2 kHz Buzz Chorus occurred midevening and peaked later each date; and the 3-4 kHz Snapping Shrimp Chorus peaked after sunset, with a weaker dawn peak and moderate evening amplitude. 0.5-1 kHz Late Chorus occurrence was predicted by non-linear relationships with temperature and daylength and highest temperatures and shortest days increased likelihood of occurrence. Higher dissolved oxygen increased likelihood of 1-2 kHz Buzz Chorus occurrence and predicted higher 0.5-1 kHz Late Chorus amplitudes. Temperature predicted linearly increasing 3-4 kHz Snapping Shrimp Chorus amplitude. Further study on how animals use sound in these habitats is warranted, especially to understand potential impacts with anthropogenic noise, which increased dramatically at one site following Hurricane Ida.