Soundscapes and living communities in coral reefs: temporal and spatial variation

Abstract

Acoustic landscapes, or soundscapes, can vary due to biological ('biophony'), geophysical ('geophony') and anthropogenic ('anthrophony') components, and in some environments, such as many coral reefs, biophony dominates the soundscape. We compared 126 sound recordings from 3 different times of day (day, dusk and night) at 42 locations with concurrent fish and habitat surveys to investigate the relationships of acoustic parameters with biological and physical characteristics of coral reefs in the Gambier Archipelago, French Polynesia. Principal Component Analysis revealed that most of the variability in soundscapes could be described using only 4 factors: (1) full bandwidth root mean squared sound pressure level (SPL; 0.01 to 22.5 kHz in dB re 1 µPa); SPL of frequencies (2) >0.63 kHz and (3) between 0.16 and 2.5 kHz; and (4) the number of snaps made by snapping shrimp. Number of snaps in a recording and SPL above 0.63 kHz were negatively related to live coral cover, and the density and diversity of adult and juvenile fish, but positively related to dead coral cover and time of day (as the day progressed from day to dusk to night). Full bandwidth SPL and midrange SPL were positively related to sea state, depth, Porites coral, the coral forms 'branched' and 'massive' and whether the bottom was coverd by coral (live or dead). Soundscape recordings can contribute to a more complete assessment of ecological landscapes and, in cases where logistical constraints preclude traditional survey methods, passive acoustic monitoring may give valuable information on whether habitats are changing over time.

Rapidly obtained ecosystem indicators from coral reef soundscapes

“…Due to the complex nature of the acoustic environment in shallow water and the high degree of variability in sounds produced by organisms, careful interpretation and vetting of recordings with ecological data is necessary. Following work in terrestrial environments (Sueur et al 2008, Depraetere et al 2012), a number of recent studies (Kennedy et al 2010, McWilliam & Hawkins 2013, Lillis et al 2014, Piercy et al 2014, Nedelec et al 2015 have explored relationships between spectral and temporally filtered aspects of the underwater soundscape and ecological data using a variety of statistical techniques. Nighttime sound levels are observed to be generally higher in all studies, although attempts to quantify faunal activity through direct observation at night were problematic due to the need for divers to use illumination that (1) limited the observable area and (2) subsequently altered animal behavior (Nedelec et al 2015).…”

“…Following work in terrestrial environments (Sueur et al 2008, Depraetere et al 2012), a number of recent studies (Kennedy et al 2010, McWilliam & Hawkins 2013, Lillis et al 2014, Piercy et al 2014, Nedelec et al 2015 have explored relationships between spectral and temporally filtered aspects of the underwater soundscape and ecological data using a variety of statistical techniques. Nighttime sound levels are observed to be generally higher in all studies, although attempts to quantify faunal activity through direct observation at night were problematic due to the need for divers to use illumination that (1) limited the observable area and (2) subsequently altered animal behavior (Nedelec et al 2015). Nevertheless, it is generally accepted that nocturnal sound levels above several hundred Hertz are elevated due to invertebrate activity (Johnson et al 1947, Freeman et al 2014, Staaterman et al 2013.…”

“…These techniques can introduce sampling error (due to the limited range of diver vision, optical sensors and diver endurance) and bias (due to the effect of the diver's presence on animal behavior). Furthermore, these surveys generally require a research vessel on station, and thus are not conducted frequently and cannot be conducted at night when benthic organisms are more active (Johnson et al 1947, Freeman et al 2014, Nedelec et al 2015. The majority of faunal biomass on a coral reef may be small, cryptic and subterranean (Plaisance et al Outside ABSTRACT: Present-day coral reef ecosystem monitoring techniques can be costly, labor-intensive point measurements that can potentially introduce intractable sampling bias and error.…”

Emerging opportunities and challenges for passive acoustics in ecological assessment and monitoring

“…There is a rich literature on the effects of anthropogenic noise on cetacean and increasingly avian populations and behaviour (e.g., Pirotta, Merchant, Thompson, Barton, & Lusseau, ; Proppe, Sturdy, & St. Clair, ). Sensor networks can monitor ecosystems over large geographical and temporal scales, facilitating the characterisation of acoustic communities across habitats and biomes and the development of putative acoustic biodiversity indices (Nedelec et al., ; Sueur, Farina, Gasc, Pieretti, & Pavoine, ; Sueur, Pavoine, Hamerlynck, & Duvail, ) (Table ). Researchers are also now starting to explore the opportunities afforded by archived audio datasets collected over years or decades, often by volunteers or multiple research groups (Jones et al., ; Van Parijs et al., ).…”

Building capacity in biodiversity monitoring at the global scale

“…These advances render soundscaping highly usable for biodiversity monitoring to sample species that create typical sounds (singing of birds, croaking of amphibians, chirping of grasshoppers, etc.). Similarly, hydrophones can be used for monitoring marine species (Lammers et al 2008;Nedelec et al 2015;Wiggins and Hildebrand 2007). Rollout of standardized protocols for soundscaping and camera trapping across large regions can provide extensive monitoring based on recording the presence of species as well as population sizes and abundances; recently, this has been explored widely in the marine biome (Erbe et al 2016;Merchant et al 2016; Sánchez-Gendriz and Padovese 2016).…”