Response of marine invertebrate larvae to natural and anthropogenic sound: a pilot study

Many vertebrates and invertebrates in the marine environment create and respond to sound. Due to increasing use of waterways, levels of anthropogenic sound are greater than ever. We examined the responses of larvae of temperate invertebrates to three sound treatments: natural ambient sound (shallow rocky reef), anthropogenic sound (an outboard motor) and no sound (control). Sound recordings were played to molluscan, echinoderm and bryozoan larvae in Petri dishes in the laboratory and the movement of swimming larvae was filmed and quantified in two-dimensional space. Larvae of the gastropod Bembicium nanum increased their swimming activity in response to both natural and anthropogenic sound, while larvae of the bryozoan Bugula neritina decreased swimming activity when exposed to boat sounds, but not recordings from the natural reef. Considerable variation was observed in the swimming behavior of larvae of the echinoid Heliocidaris erythrogramma and we did not observe any differences in response among the treatments. The behavior of the oyster Crassostrea gigas was dependent on its nutritional status. Unfed larvae did not respond to sound, whereas fed larvae increased swimming activity, but only in response to natural sound. Hence effects were highly species-specific, with three of the four species showing some response to sound and apparently distinguishing among different sound frequencies. This study adds to the growing body of evidence that sound may be an important behavioral cue. It may justify further research into the use of sound as an antifouling agent or a tool in the restoration of reef species.