Abstract
Auditory information is widely used throughout the animal kingdom in both terrestrial and aquatic environments. Some marine species are dependent on reefs for adult survival and reproduction, and are known to use reef noise to guide orientation towards suitable habitat. Many others that forage in food-rich inshore waters would, however, benefit from avoiding the high density of predators resident on reefs, but nothing is known about whether acoustic cues are used in this context. By analysing a sample of nearly 700,000 crustaceans, caught during experimental playbacks in light traps in the Great Barrier Reef lagoon, we demonstrate an auditory capability in a broad suite of previously neglected taxa, and provide the first evidence in any marine organisms that reef noise can act as a deterrent. In contrast to the larvae of species that require reef habitat for future success, which showed an attraction to broadcasted reef noise, taxa with a pelagic or nocturnally emergent lifestyle actively avoided it. Our results suggest that a far greater range of invertebrate taxa than previously thought can respond to acoustic cues, emphasising yet further the potential negative impact of globally increasing levels of underwater anthropogenic noise.
Highlights
Across the animal kingdom, acoustic information is frequently used in orientation, habitat selection and predator avoidance
There was no significant difference in the number of brachyuran megalops caught depending on sound treatment (GLMM: Wald statistic = 3.05, df = 1, P = 0.085), but brachyuran zoea were caught in significantly higher numbers in traps playing back reef noise compared to control traps (Wald statistic = 5.63, df = 1, P = 0.021; Fig. 2a)
Of the five taxa that tend to be mostly nocturnally emergent, Cumacea did not show a significant response to reef noise playback (Wald statistic = 2.79, df = 1, P = 0.100), but Caridea (Wald statistic = 18.89, df = 1, P,0.001), Gammaridea (Wald statistic = 24.39, df = 1, P,0.001), Mysidae (Wald statistic = 16.88, df = 1, P,0.001) and Ostracoda (Wald statistic = 52.87, df = 1, P,0.001) were all significantly more common in control traps compared to those playing back reef noise (Fig. 2c)
Summary
Acoustic information is frequently used in orientation, habitat selection and predator avoidance. Underwater, sound has two major components: in the acoustic nearfield (confined to an area within 1 or 2 wavelengths) particle velocity dominates, while in the acoustic farfield, the propagating pressure wave component dominates [3,4] These acoustic components are detected by animals in two ways: sensory hair-like receptors are used to detect one-way particle displacement of water in the nearfield, whereas membranous receptors are used for the detection of farfield two-way particle oscillations. While these sensory mechanisms are well understood for fish and marine mammals, there is a relative paucity of information on whether aquatic invertebrates can detect and utilise acoustic cues. Selection might be expected to act on these species to evolve an ability to detect and avoid reef noise, but this possibility has never been explored
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