Vessel generator noise as a settlement cue for marine biofouling species

Abstract

Underwater noise is increasing globally, largely due to increased vessel numbers and international ocean trade. Vessels are also a major vector for translocation of non-indigenous marine species which can have serious implications for biosecurity. The possibility that underwater noise from fishing vessels may promote settlement of biofouling on hulls was investigated for the ascidian Ciona intestinalis. Spatial differences in biofouling appear to be correlated with spatial differences in the intensity and frequency of the noise emitted by the vessel’s generator. This correlation was confirmed in laboratory experiments where C. intestinalis larvae showed significantly faster settlement and metamorphosis when exposed to the underwater noise produced by the vessel generator. Larval survival rates were also significantly higher in treatments exposed to vessel generator noise. Enhanced settlement attributable to vessel generator noise may indicate that vessels not only provide a suitable fouling substratum, but vessels running generators may be attracting larvae and enhancing their survival and growth.

Keywords:

• underwater sound
• ascidian
• larval settlement
• metamorphosis
• vessel noise
• biofouling

Acknowledgements

The authors thank Kailis Marine (Terry Hewitt) for access to vessels in Fremantle, Caroline Williams (NIWA) for collecting Ciona intestinalis adults, the University of Auckland Leigh Marine Laboratory for provision of laboratory space and equipment, Samantha Bridgwood for assistance with fieldwork and internal reviewers for constructive feedback and review of the manuscript. This research was funded by NIWA under the Innovative Seed Fund (2011/2012) and Coasts and Oceans Programme 4 – Marine Biosecurity (2014/15 SCI), the Glenn Family Foundation and Western Australian Department of Fisheries. The authors wish to thank Wayne Young and Dan Pederson (Dampier Port Authority) for their support and enthusiasm.