Temperate reef soundscapes exhibit similar temporal patterns but distinct spectral content: a comparison of natural and artificial reefs

Sound plays a critical role in the ecology of many species, and soundscapes on natural and artificial reefs could affect ecosystem function through species behavior and interactions. We documented the temporal and spectral patterns of biological sound production across four rocky or artificial reef habitats on the North Carolina, USA continental shelf during five, week-long hydrophone deployments. We observed three dominant fish vocalizers with seasonal chorusing patterns, including a toadfish species (Opsanus spp.) Analysis of the patterns of sound pressure level on hourly and seasonal scales identified peak biological acoustic activity daily at dusk in the fish-dominated, low-frequency band and during crepuscular periods in the invertebrate-dominated, high-frequency band. Seasonally, sound pressure levels (SPL) were greatest in both frequency bands in April. Although each reef exhibited similar temporal patterns, multivariate analyses indicate that each reef had a distinct low-frequency spectral composition, with each site driven by dominant acoustic activity in a specific frequency band that varied seasonally. During seasons with increased acoustic activity, multivariate analyses revealed that soundscapes from the same reef type are more similar than those of different reef types. Our findings suggest that the soundscapes of shipwreck reefs may differ from the soundscapes of natural rocky reefs, possibly due to differing community composition and differences in non-vocalization sounds that contribute to the ambient soundscape present on each reef. Furthermore, consistent patterns in relative SPL and unique spectral composition among sites suggests that marine soundscapes may encode habitat and community traits.