Boat noise prevents soundscape-based habitat selection by coral planulae

David Lecchini,Frédéric Bertucci,Danielle L Dixson,Natacha Roux,Laetitia Hédouin,Maggy M Nugues,Cecile Berthe,Adam Khalife,Shubha Singh,Camille Gache,Eric Parmentier,Rohan M Brooker,Marc Besson

doi:10.1038/s41598-018-27674-w

Abstract

Understanding the relationship between coral reef condition and recruitment potential is vital for the development of effective management strategies that maintain coral cover and biodiversity. Coral larvae (planulae) have been shown to use certain sensory cues to orient towards settlement habitats (e.g. the odour of live crustose coralline algae - CCA). However, the influence of auditory cues on coral recruitment, and any effect of anthropogenic noise on this process, remain largely unknown. Here, we determined the effect of protected reef (MPA), exploited reef (non-MPA) soundscapes, and a source of anthropogenic noise (boat) on the habitat preference for live CCA over dead CCA in the planula of two common Indo-Pacific coral species (Pocillopora damicornis and Acropora cytherea). Soundscapes from protected reefs significantly increased the phonotaxis of planulae of both species towards live CCA, especially when compared to boat noise. Boat noise playback prevented this preferential selection of live CCA as a settlement substrate. These results suggest that sources of anthropogenic noise such as motor boat can disrupt the settlement behaviours of coral planulae. Acoustic cues should be accounted for when developing management strategies aimed at maximizing larval recruitment to coral reefs.

Highlights

Larval replenishment is essential for the maintenance and recovery of marine benthic communities, especially in systems that rely on functionally important or foundation species, such as coral reefs[1]
Coral planulae respond positively to the natural reef sounds produced by resident fish and crustaceans[20] and ‘high amplitude’ soundscapes have been shown to generate a higher settlement rates compared to quieter environments[21]
Together with a control treatment, all sounds were tested on P. damicornis, while the sounds of only one Marine Protected Areas (MPA)/non-MPA pair, and the boat sound were tested on A. cytherea

Summary

Introduction

Larval replenishment is essential for the maintenance and recovery of marine benthic communities, especially in systems that rely on functionally important or foundation species, such as coral reefs[1]. Reef ’s sound is temporally variable at a range of scales, changing diurnally, over lunar cycles, and with the seasons[17,18,19] These acoustic cues play an important role during recruitment with several studies showing the phonotaxis of larval fishes and crustacean to reef habitats[5]. Healthy coral reef communities are associated with specific ambient soundscapes[27,28] with a positive correlation between coral cover, fish density and sound levels[29] This may be a result of positive feedback mechanisms, with healthy, biodiverse reefs inherently louder and richer acoustically than degraded locations[30,31]

Methods

Results

Conclusion