Assessing sound exposure from shipping in coastal waters using a single hydrophone and Automatic Identification System (AIS) data Nathan D. Merchant a,⇑ , Matthew J. Witt b , Philippe Blondel a , Brendan J. Godley c , George H. Smith d a Department of Physics, University of Bath, Bath BA2 7AY, UK b Environment and Sustainability Institute, College of Life and Environmental Sciences, University of Exeter, Penryn, Cornwall TR10 9EZ, UK c Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn, Cornwall TR10 9EZ, UK d Renewable Energy Research Group, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Penryn, Cornwall TR10 9EZ, UK article info Keywords: Ship noise Noise assessment Coastal management Continuous monitoring Acoustic impact Marine protected area abstract Underwater noise from shipping is a growing presence throughout the world’s oceans, and may be sub- jecting marine fauna to chronic noise exposure with potentially severe long-term consequences. The coincidence of dense shipping activity and sensitive marine ecosystems in coastal environments is of par- ticular concern, and noise assessment methodologies which describe the high temporal variability of sound exposure in these areas are needed. We present a method of characterising sound exposure from shipping using continuous passive acoustic monitoring combined with Automatic Identification System (AIS) shipping data. The method is applied to data recorded in Falmouth Bay, UK. Absolute and relative levels of intermittent ship noise contributions to the 24-h sound exposure level are determined using an adaptive threshold, and the spatial distribution of potential ship sources is then analysed using AIS data. This technique can be used to prioritise shipping noise mitigation strategies in coastal marine environments. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Anthropogenic underwater noise can have deleterious effects on a variety of marine organisms, including mammals (Richardson et al., 1995; Nowacek et al., 2007), fish (Popper and Hastings, 2009a; Slabbekoorn et al., 2010) and cephalopods (André et al., 2011). High-intensity, short-term events such as seismic surveys, pile-driving operations and military sonar activities have been the focus of considerable attention due to their potential to cause physical injury and temporary or permanent loss of hearing sensi- tivity in marine mammals (e.g. Evans and England, 2001; Lucke et al., 2009; Bailey et al., 2010). Less intense sources can also elicit behavioural responses: boat noise, for example, has induced avoid- ance reactions in several cetacean species (Richardson and Würsig, 1997). However, there is also growing recognition of the potential for long-term exposure to anthropogenic noise to induce chronic ef- fects in marine species (Tyack, 2008; Slabbekoorn et al., 2010). These effects may occur at levels below those necessary to induce short-term behavioural responses, and through mechanisms which are more difficult to observe. They include masking of biologically significant sounds (Clark et al., 2009; Popper and Hastings, 2009b), chronic stress (Wright et al., 2007; Rolland et al., 2012), subtle long-term behavioural responses (Picciulin et al., 2010) and shifts in attention (Chan et al., 2010; Purser and Radford, 2011). In situ measurements of long-term exposure to anthropogenic noise both in absolute terms and relative to background levels are needed to inform further investigation in this area (Ellison et al., 2012). Noise from shipping is pervasive throughout the marine envi- ronment, especially at low (<300 Hz) frequencies (Richardson et al., 1995; Chapman and Price, 2011), and is therefore a key con- cern regarding the effects of chronic noise exposure on marine spe- cies (Slabbekoorn et al., 2010). Deep water observations have shown that ambient noise levels have been rising since at least the 1960s due to increases in shipping traffic and tonnage (Andrew et al., 2002; McDonald et al., 2006; Chapman and Price, 2011). Ambient noise levels in shallower coastal waters are more difficult to characterise as they exhibit much higher spatiotemporal vari- ability (Urick, 1983). This is partly due to the greater dependence of acoustic propagation on local environmental factors such as the sound speed profile and seabed composition (Jensen et al., 2011). Significantly, variability is also caused by a higher concen- tration of shipping, industrial activity, and biological noise sources: it is this combination of potentially conflicting acoustic interests that necessitates the development of noise assessment methodol- ogies applicable to coastal environments. To be meaningful, these methodologies must incorporate metrics relevant to the assess- ment of impacts on marine life. 0025-326X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.marpolbul.2012.05.004 ⇑ Corresponding author. Tel.: +44 1225 385543. E-mail address: n.d.merchant@bath.ac.uk (N.D. Merchant). Marine Pollution Bulletin xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul Please cite this article in press as: Merchant, N.D., et al. Assessing sound exposure from shipping in coastal waters using a single hydrophone and Auto- matic Identification System (AIS) data. Mar. Pollut. Bull. (2012), http://dx.doi.org/10.1016/j.marpolbul.2012.05.004