Biogeography of acoustic biodiversity of NW Mediterranean coralligenous reefs

Abstract

Monitoring the biodiversity of key habitats and understanding the drivers across spatial scales is essential for preserving ecosystem functions and associated services. Coralligenous reefs are threatened marine biodiversity hotspots that are challenging to monitor. As fish sounds reflect biodiversity in other habitats, we unveiled the biogeography of coralligenous reef sounds across the north-western Mediterranean using data from 27 sites covering 2000 km and 3 regions over a 3-year period. We assessed how acoustic biodiversity is related to habitat parameters and environmental status. We identified 28 putative fish sound types, which is up to four times as many as recorded in other Mediterranean habitats. 40% of these sounds are not found in other coastal habitats, thus strongly related to coralligenous reefs. Acoustic diversity differed between geographical regions. Ubiquitous sound types were identified, including sounds from top-predator species and others that were more specifically related to the presence of ecosystem engineers (red coral, gorgonians), which are key players in maintaining habitat function. The main determinants of acoustic community composition were depth and percentage coverage of coralligenous outcrops, suggesting that fish-related acoustic communities exhibit bathymetric stratification and are related to benthic reef assemblages. Multivariate analysis also revealed that acoustic communities can reflect different environmental states. This study presents the first large-scale map of acoustic fish biodiversity providing insights into the ichthyofauna that is otherwise difficult to assess because of reduced diving times. It also highlights the potential of passive acoustics in providing new aspects of the correlates of biogeographical patterns of this emblematic habitat relevant for monitoring and conservation.

A Fish and Dolphin Biophony in the Boat Noise-Dominated Soundscape of the Cres-Lošinj Archipelago (Croatia)

“…Further, for the first time, the knowledge of the local soundscape is expanded to the nocturnal hours by using 24 h recordings, looking for nychthemeral cycles. Animals' vocalization and boat noise were detected by the aural and visual inspection of the acoustic files, in accord with many other studies [6,[38][39][40]. Local soundscape characteristics were also described in terms of broadband and one-third octave band levels.…”

“…The study of the soundscape aims to characterize the spatial and temporal acoustic variation in an environment and uses soundscape characteristics to infer habitat quality [2][3][4]. Marine acoustic diversity patterns, measured as the richness and diversity of sound types emitted by vocal animals, have been proved to provide multi-level information on biodiversity, environmental status, protection level, community stability and habitat functionality, even in cases in which the identity of the emitting species has not been yet identified [5,6]. As a result, underwater soundscapes, monitored by non-invasive and relatively low-cost passive acoustics sensors (PAM: passive acoustic monitoring), are now recognized as fundamental features for obtaining ecologically relevant information, supporting its use instead and/or together with other approaches.…”

Sounding the Call for a Global Library of Underwater Biological Sounds

“…There is increasing evidence that the study of acoustic communities, based on acoustic characteristics of the sounds emitted by animal communities, provides ecologically relevant information (Francis et al, 2009;Farina and James, 2016;Desiderà et al, 2019;Mooney et al, 2020). Soundscapes provide unique opportunities to investigate the biodiversity and community of soniferous species, frequency and temporal niche partitioning, and organism-environment relationships (Ruppe et al, 2015;Di Iorio et al, 2021;McKenna et al, 2021). However, this field is in its infancy and requires a catalog of identified sounds to develop reliable and time-efficient classification techniques that will be necessary for describing the acoustic communities and relating them to the underlying animal assemblages (Mooney et al, 2020).…”

“…In addition, we know more about the sounds of endangered or commercially important species than those of commonly encountered species (Luczkovich et al, 2008;Popper and Hawkins, 2019). This knowledge gap has impeded effective use of underwater soundscapes in monitoring marine biodiversity, but much information on acoustic ecology can still be gleaned from categorized sound types of unknown origin (Le Bot et al, 2015;Rountree et al, 2019;Bertucci et al, 2020;Bolgan et al, 2020a;Di Iorio et al, 2021). A library to archive unknown sounds and their recording times and locations will be crucial for guiding future studies of marine bioacoustics and biodiversity.…”

“…Collectively there are now multi-millions of recording hours around the world that could potentially be assessed for a plethora of both known and, to date, unidentified biological sounds. Only recently have studies begun to address the groupings of such sounds, in the field of acoustic community ecology (Desiderà et al, 2019;Bolgan et al, 2020a;Di Iorio et al, 2021).…”