MEPS prepress abstract  -  DOI: https://doi.org/10.3354/meps12370

Mapping the diversity of spectral shapes discriminates between adjacent benthic biophonies

J. Lossent*, L. Di Iorio, C-A. Valentini-Poirier, P. Boissery, C. Gervaise

*Email: julie.lossent@chorusacoustics.com

ABSTRACT: Coastal soundscapes are dominated by broadband transient sounds primarily emitted by benthic invertebrates. These sounds are characterized by a very large dynamic of amplitude. The loudest ones propagate further and interfere with the detectability of benthic sounds by invading other more distant habitats. Acoustic diversity assessment is therefore biased when applying acoustic indices related to the signal’s power. Here, we propose new acoustic indices (IDSS: Indices of the Diversity of Spectral Shape) capable of extracting the diversity of the Benthic Invertebrate Biophony (BIB) despite the interference of loud and abundant sounds. A passive acoustic ecological survey was conducted in a shallow water Mediterranean bay with a small-scale mosaic of biocenosis. Sound pressure level and spectrum of the BIB revealed that the rocky fringe has the most powerful biophony propagating up to 3680m, thus “invading” other habitats. These power-based indices failed in depicting BIB diversity. The IDSS allowed to discriminate the BIB diversity despite the interfering rocky fringe biophony and including low-power sounds not depicted by traditional power-based methods. Four main categories of Benthic Invertebrates Sounds (BIS) spectra were found. Two categories (high-power, peak frequencies ~3kHz, 4kHz) were mainly linked to the rocky fringe. Their contribution to the diversity (56%) decreased with increasing distance to the fringe where low-power BIS (peak frequencies above 15kHz) predominantly contributed to the BIB (42%) and may be specific to coralligenous reefs. The IDSS enable a better characterization and quantification of the BIB diversity and of the soundscape structure with a fine spatial resolution (~200m).