Variation in habitat soundscape characteristics influences settlement of a reef-building coral

Abstract

Coral populations, and the productive reef ecosystems they support, rely on successful recruitment of reef-building species, beginning with settlement of dispersing larvae into habitat favourable to survival. Many substrate cues have been identified as contributors to coral larval habitat selection; however, the potential for ambient acoustic cues to influence coral settlement responses is unknown. Using in situ settlement chambers that excluded other habitat cues, larval settlement of a dominant Caribbean reef-building coral, Orbicella faveolata, was compared in response to three local soundscapes, with differing acoustic and habitat properties. Differences between reef sites in the number of larvae settled in chambers isolating acoustic cues corresponded to differences in sound levels and reef characteristics, with sounds at the loudest reef generating significantly higher settlement during trials compared to the quietest site (a 29.5 % increase). These results suggest that soundscapes could be an important influence on coral settlement patterns and that acoustic cues associated with reef habitat may be related to larval settlement. This study reports an effect of soundscape variation on larval settlement for a key coral species, and adds to the growing evidence that soundscapes affect marine ecosystems by influencing early life history processes of foundational species.

Underwater Soundscape Monitoring and Fish Bioacoustics: A Review

“…These studies have found suggestive differences in the acoustic signatures of healthy versus degraded habitats, but such differences may just as likely be based upon the variation in biological communities. The playback of healthy coral reef habitat sounds also results in greater attraction by the settlement stages of coral, mollusk, and coral reef fish larvae, which are migrating from offshore [5][6][7][8]11,106].…”

“…Power spectral density (PSD) was the most commonly used [3,7,[17][18][19]21,22,38,43,46,59,61,63,64,[66][67][68]. Sound pressure level (SPL), or root mean square (RMS)-SPL, were the next most frequently used parameters [6,8,11,17,20,21,38,53,54,59,61,63,64,68,69]. SPL is a logarithmic summary measure of the ratio of the pressure of a sound relative to a reference value and results in a measurement in decibels (dB).…”

“…Our review paper aimed to compile a summary table of acoustic measurements from various aquatic habitats to allow for an analysis of the spatial variability between the soundscapes of different underwater ecosystems. After surveying 22 studies that characterized the ambient soundscape of a particular habitat, or multiple habitats [3,6,[17][18][19]21,22,38,43,53,54,61,64,65,69,71,[83][84][85][86][87][88], only seven studies provided exact quantitative measurements either in the body of the paper or in a table/supplementary material [18,19,38,54,61,71,83]. However, the values provided in these seven papers were different metrics (PSD, SPL, sound intensity, and ACI), and therefore could not be directly compared.…”

“…Coral reef habitats were once thought to be in a "silent sea", but have now been revealed as "choral reefs" based on using new acoustic technologies [4]. Ship and other man-made noises in the oceans have increased drastically over the past few decades and have raised concerns about interference with animal behavior, such as masking animal communication or impeding larval settlement [5][6][7][8][9][10][11]. This has all lead to the development of methods to monitor underwater sounds in order to document the soundscapes of different habitats at given locations over time.…”

Settlement Patterns of Corals and other Benthos on Reefs with Divergent Environments and Disturbances Histories around the Northeastern Arabian Peninsula

“…Whether reefs can recover from these disturbances will depend, in part, on the supply of colonists available to settle to newly opened space that appears on reefs following a disturbance (Gilmour et al, 2013). Both stochastic processes which affect the supply of potential colonists and deterministic processes such as habitat availability, larval preferences, and interactions with existing community members, can influence settlement patterns (Lillis et al, 2016). Post-settlement processes then further shape subsequent community development (Caley et al, 1996).…”