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Abstract
Underwater sound plays an important role in the settlement behaviour of many coastal organisms. Large steel-hulled vessels are known to be a major source of underwater sound in the marine environment. The possibility that underwater sound from vessels may promote biofouling of hulls through triggering natural larval settlement cues was investigated for the mussel, Perna canaliculus. The mussel larvae showed significantly faster settlement when exposed to the underwater noise produced by a 125-m long steel-hulled passenger and freight ferry. Median time to attachment on the substrata (ie settlement) was reduced by 22% and the time taken for all experimental larvae to settle was reduced by 40% relative to a silent control. There was no difference in the survival of the mussel larvae among the various noise treatments. The decrease in settlement time of the mussel larvae appeared to correlate with the intensity of the vessel sound, suggesting that underwater sound emanating from vessels may be an important factor in exacerbating hull fouling by mussels.
Acknowledgements
The authors thank Dan McCall and Bridget Alexander at Shellfish Production and Technology NZ Ltd (Glenhaven Aquaculture Park, Nelson) for providing the cultured mussel larvae and Dr Graeme Inglis (NIWA, Christchurch) for constructive feedback and review of the manuscript. Financial support for the research came from the NIWA Seed Innovation Fund and the Glenn Family Foundation.