Adjacent coral reef habitats produce different underwater sound signatures

The underwater sound generated by the organisms on a reef has been shown to provide an important orientation cue for a wide range of larval, juvenile and adult marine organisms. There is some preliminary evidence that some organisms can discriminate among different benthic habitats using sound cues over relatively short spatial ranges (i.e. within hundreds of metres); however, the divergence in the sound emitted from different habitats, often in close proximity to one another, is poorly described. Therefore, the sound emitted from single locations within 3 adjacent habitats, Fringing Reef, Back Reef and Lagoon, at Lizard Island on the Great Barrier Reef, Australia, were recorded during the new moon phase in early summer. Analyses of the sound recordings revealed differences among these 3 habitats in the temporal and frequency composition and in sound levels. Most of the spectral variability among the 3 habitats was observed below 800 Hz, where the duration of the dusk chorus differed between the 3 habitats. Some of these observed differences were due to the acoustic output of some key soniferous organisms dwelling in these habitats, especially snapping shrimp and fish species producing a pop sound. It is possible that these habitat-related differences in underwater sound are being used to remotely guide the movement of coastal organisms in relation to these habitats.