Effects of Repeated and Continuous Sound Exposures on Mussels (Mytilus spp.) in the Lab

Human activities at sea have increasingly changed the marine soundscape over the last decades, and many of these have been shown to potentially impact marine life. Bivalves and other invertebrates received limited attention in sound impact studies, despite their importance to the marine ecosystem. Furthermore, many studies only focus on the effects of the sound onset or on the effects of the sound exposure as a whole. However, the impact over time of an exposure or over repeated exposures may also reveal relevant information on how bivalves respond to sound and what mechanisms may explain variation in their responsiveness. This chapter analyzes the combined results of four published experiments on the effects of sound on mussels (Mytilus spp.) to reveal generalities in their valve gape behavior throughout the trials of all studies. Across studies, mussels responded to sound by partial valve closure and also returned to pre-exposure valve gape levels within the exposure periods. Furthermore, the closing response decayed over sequential sound exposures. These results provide insight into the initial and long-term effects of sound on mussels. Future studies should examine effect of sound in situ and link this to fitness and population consequences.