Science for Environment Policy FUTURE BRIEF: Underwater Noise

June 2013 Issue 7 Revised version*

Environment

*This version of the report, published on 30 October 2013, replaces the earlier versions published on 28 June 2013 and 2 September 2013. Science for Environment Policy This Future Brief is written and edited by the Science Underwater Noise Communication Unit, University of the West of England (UWE), Bristol Email: [email protected]

Contents To cite this publication: Science Communication Unit, University of the West of England, Bristol (2012). Science for Environment Policy Future Introduction 3 Brief: Underwater Noise. Report produced for the European Types and sources of underwater noise 4 Commission DG Environment, June 2013. Available at: http://ec.europa.eu/science-environment-policy Impacts of underwater noise on marine life 4 The ultimate effects of underwater noise on people and society 6 Acknowledgements We wish to thank Rene Dekeling of the Ministry of Monitoring underwater noise 6 Infrastructure and the Environment, Netherlands, and Mark Reducing the impact of underwater noise 7 Tasker of the Joint Nature Conservation Committee (JNCC), Knowledge gaps 7 UK, for their input to this report. Final responsibility for the content and accuracy of the report, however, lies solely with Summary 7 the author.

Images Page 3: ©istockphoto.com/ultramarinfoto. Page 4: Corrigenda ©istockphoto.com/Brad Martin. Page 4: ©istockphoto.com/ crisod. This version of the report, published on 30 October 2013, replaces the earlier versions published on 2nd September 2013 and 28th June 2013. Following consideration of comments received on the Underwater Noise Future Brief, elements of the text have been modified as follows:

Amendments made on 30 October 2013:

Section 1, Types and sources of underwater noise, page 4. This has been amended to acknowledge that "mid frequency naval sonar may be harmful to marine mammals". About Science for Environment Policy Section 2.1. Physical damage, page 4. To better reflect the scientific consensus, the second paragraph has been revised. It draws attention to research (Frantzis, 1998) that indicates that Science for Environment Policy is a free news noise produced by military sonar can cause stranding in beaked whales and provides information and information service published by the European taken from a report by the International Council for the Exploration of the Sea (2005) on the possible mechanisms that may lead to stranding. Commission’s Directorate-General Environment, which provides the latest environmental policy- Amendments made on 2nd September 2013: relevant research findings. Introduction, page 3. To acknowledge existing uncertainty surrounding the evidence, the statement ‘Currently these requirements pose a challenge, particularly considering the limited Future Briefs are a feature of the service, evidence on sounds impacts” has been changed to: ‘Currently these requirements pose a challenge, introduced in 2011, which provide expert forecasts particularly considering the difficulties of generalising based on existing evidence from a range of of environmental policy issues on the horizon. In different species and noise sources.” addition to Future Briefs, Science for Environment Section 2.4. The balance of effects, page 6. To acknowledge existing uncertainty surrounding Policy also publishes a weekly News Alert which the evidence, the statement "As current evidence suggests that noise only rarely kills marine animals, is delivered by email to subscribers and provides those pressures that do very often kill marine species, such as fishing and pollution, could be considered accessible summaries of key scientific studies. more important”, has been changed to “As it remains an open question how many marine animals are killed by noise, those pressures that are known to kill marine species, such as fishing and pollution, could be considered more important.” http://ec.europa.eu/science-environment-policy Summary, page 7. To account for the broad range of noise sources, the statement the summary “Underwater noise from shipping, energy production, fishing and tourism”, has been modified to “Underwater noise from sources including shipping, energy production, fishing and tourism”. Keep up-to-date

The following references have been added to support information provided in the report: Subscribe to Science for Environment Policy’s Frantzis (1998); International Council for the Exploration of the Sea (2005); Løkkeborg et al. (2010). weekly News Alert by emailing: [email protected]

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Introduction Underwater Noise The oceans are increasingly exposed to sounds from human activities, such as shipping and the building of foundations for offshore construction projects. What impact do these sounds have on species that inhabit the marine environment? This Future Brief from Science for Environment Policy explores existing research on the ecological effects of underwater sound. Key gaps in our knowledge are also highlighted, and potential strategies for reducing negative impacts on marine species are outlined.

Underwater noise is an important aspect of the Marine addition, under the Habitats Directive, noise is regarded Strategy Framework Directive (MSFD), which aims as a disturbance that may have detrimental effects on to achieve good environmental status (GES) of the wildlife, including marine life. In particular, it prohibits European marine environment by 2020. Noise is deliberate disturbances that affect populations of defined here as sound that causes negative effects. protected species and their ability to survive, breed and rear their young (European Commission, 2007). GES is defined according to a set of 11 broad indicators or ‘descriptors’1, including those focusing on biological However, as part of the MSFD roadmap, EU Member diversity, fish populations and marine litter. Descriptor States will need to address sound more directly and 11 focuses on energy inputs, including underwater work together in shared waters to achieve GES as noise. In February 2012, the MSFD Technical Subgroup defined under descriptor 11. This will involve defining on Underwater Noise delivered a report to the European potentially harmful levels of underwater sound, and Commission, providing guidance on implementing putting in place monitoring systems (by 2014) and aspects of the MSFD under descriptor 11 (Van Der measures (by 2015) that will be needed if underwater Graaf et al, 2012). sound needs to be reduced. Currently these requirements pose a challenge, particularly considering the difficulties Some existing measures indirectly control sound in of generalising based on existing evidence from a range European waters. For example, permits for pile-driving of different species and noise sources. – the sinking of pole-like foundations – are granted based on Environmental Impact Assessments. In 1. http://ec.europa.eu/environment/water/marine/ges.htm UNDERWATER NOISE 4

1. Types and sources of underwater noise

Sound travels rapidly through water – four times faster than through air. As in open air, sounds are transmitted in water as a pressure wave. They can be loud or soft, high- or low-pitched, constant or intermittent, and volume decreases with increasing distance from source. Sound pressure is most commonly measured in decibels (dB). Underwater noise (as viewed by the MSFD) has been divided into two main types:

• Impulsive: loud, intermittent or infrequent noises, such as those generated by piling, and seismic surveys • Continuous: lower-level constant noises, such as those generated by shipping and wind turbines

These two types of MSFD-related noise have different impacts on marine life. In addition, mid-frequency naval sonar may be harmful to marine mammals. The frequency, or pitch, of the noise is also important, as animals are sensitive to different frequencies. For instance, most of the noise produced by leisure boats is low frequency, below 1.5 kilohertz (kHz). Although most sensitive to sounds above 15 kHz, bottlenose dolphins could be disturbed by these boat noises because Studies suggest that the loud noises used by seismic survey ships to map the geology of the oceans and seas can they hear in the wider range 0.075 - 150 kHz and some affect the hearing and behaviour of some marine species. calls, thought to be food-related, are below 2 kHz (Rako et al, 2013).

The underwater environment is becoming noisier in some areas as it is increasingly exploited (Subsidiary ‘The underwater environment is becoming noisier in some Body on Scientific, Technical and Technological Advice, 2012). Diminishing resources mean that we are turning areas as it is increasingly exploited.’ to the oceans to generate our energy, by building offshore installations, and to mine precious minerals, and fishermen use sonar to tell them where to fish. 2. Impacts of underwater noise on marine life

Most of the research on the impacts of underwater noise has until 2.1 Physical damage recently focused on marine mammals, such as harbour porpoises. There has been less work to understand its effects on fish and other species. Studies on underwater noise have established that noise can cause permanent injury in some marine animals (Popper et al, 2005). In the In theory, the behaviour of any species with the ability to sense or use worst cases, physiological damage caused by noise can lead to death. sound may be affected by manmade noise. However, to what extent, For example, fish with swim bladders are particularly susceptible to in most cases, remains uncertain. Very loud noises, such as those made loud noises, such as those from pile driving, because the gas in their by explosives, may result in permanent damage to animals close to the swim bladders is easily expanded by sound pressure (Jones & Street, source. Whether a species is affected may also depend on that species’ 2009). This can cause the swim bladder to rupture. hearing range. Humpback whales, for example, can hear lower-pitched sounds than killer whales (Southall et al, 2007). There are many Mass strandings of marine mammals in the EU, including in Greece, difficulties associated with analysing the impacts of noise. For example, have been linked to military sonar (Frantzis, 1998). Noise produced it is difficult to understand the severity of effects that noise causes by military sonar can cause stranding in beaked whales, although it and to identify the level at which these effects become unacceptable. is not entirely clear whether stranding is due to direct physiological Furthermore, it is difficult to determine exactly which aspects of noise effects of noise, or behavioural responses to noise that lead indirectly cause adverse effects, for example, whether frequency, repetition rate or to stranding (International Council for the Exploration of the Sea, other aspects are to blame. 2005). It has been suggested that if deep-diving whales surface rapidly UNDERWATER NOISE 5

in response to noise from sonar they might suffer bubble-related tissue of cages (Fewtrell and McCauley, 2012). damage similar to that which occurs in decompression sickness in humans, and that this may lead to stranding. Less information on the effects of noise is available for marine invertebrates, such as squid. However, Fewtrell and McCauley (2012) Noise can also temporarily or permanently damage the structures of the also noted that squid jetted away from airgun noise, suggesting they ear. One study found that sonar pulses led only to temporary hearing would have left the area if they had not been confined by cages. They loss in bottlenose dolphins (Mooney et al, 2009). Unsurprisingly, also released ink, a potential alarm response. In follow-up trials, the however, hearing effects vary with the type and level of noise, as well same animals became less responsive to airgun noise, but it is not clear as between different animals. Air gun blasts similar to those used in whether this was due to hearing damage or to the animals becoming seismic surveys have been shown to cause temporary hearing loss in accustomed to the noise. northern pike fish, whereas the same blasts had no effect on broad 2 whitefish (Hastings and Popper, 2005). In turn, effects on hearing may As part of the European Commission-funded project AQUO , 13 affect animal behaviour. European partners will assess the impact of shipping noise on marine life, by linking noise maps to migration of marine species (Quiet Oceans, 2013). 2.2 Habitat displacement Exposed to noise, some marine species may move to quieter waters. As with physical effects, understanding the effects of this displacement 2. http://aquo.eu is important – some animals may return to their former habitats after loud, impulsive noise, some may be permanently displaced by low- level continuous noise, but others may remain unaffected. At present, ‘Exposed to noise, some marine species may however, displacement effects have only been observed for a few species in the short term. Longer-term studies that can distinguish between move to quieter waters.’ the effects of noise and other stressors are needed.

The range at which sound can affect marine organisms depends on many factors and varies. Madsen et al, (2006) estimated that pile- 2.3 Hunting and communication driving noises should be perceptible by marine mammals over 100 kilometres away, but evidence of displacement of harbour porpoises is disturbances limited to 15-20 kilometres. In addition, different noise sources may Even at significant distances, it is thought that manmade noises may overlap in their impacts on animal populations. alter animal behaviour by masking the sounds made by the animals themselves. For example, noise from whale-watching boats may interfere Danish nature and energy agencies and commercial wind farm with killer whale calls up to a distance of 14 kilometres (Richardson et companies have been monitoring populations of fish and marine al, 1995). Marine mammals, such as whales and dolphins, use sound to mammals at the Horns Rev and Nysted offshore wind farms since hunt, communicate and navigate, for example, using high-pitched clicks 2002 (Pickaver, 2010; Danish Energy Authority, 2006). The results that bounce off their prey. Interference with these signals by manmade for harbour porpoises are conflicting, with the population at the noise is termed ‘masking’. Masking occurs at different frequencies, with Horns Rev wind farm decreasing slightly during construction and then each species having its own critical range of frequencies and levels, recovering during operation. At Nysted, there was a larger decrease depending on the type of sounds used by the animal (Reichmuth, 2012). during construction and a slower recovery. Seals appeared only to be affected during the construction phase and fish were affected One study used modelling to estimate the impact of communication little overall. masking caused by shipping noise on fin, humpback and right whales, based on noise data collected in whale habitats in the Gulf of California In popular leisure boating areas, animal populations have shown and Mediterranean Sea (Clark et al, 2009). Shipping noise was predicted seasonal dips. Research in the northern Adriatic Sea of Croatia between to affect the endangered North Atlantic right whale more severely 2007 and 2009 showed that bottlenose dolphin populations in the because its calls are quieter. However, more research on the variability Cres-Lošinji region declined during the tourist season, between June and meaning of whale calls is needed to fully understand the impact of and September (Rako et al, 2013). The authors of the study linked the shipping noise, including its potential implications for social bonding, dips to continuous low-frequency noise produced by the engines and mating and feeding. propellers of leisure boats and suggested that dolphins avoid noisy areas because noise interferes with their ability to communicate. It is unclear to what extent marine animals are able to overcome masking noises, for instance, by altering their calls. In addition, the masking Studies on responses to underwater noise in fish suggest that loud noises effects of high-frequency sounds, such as those from echo-sounders and made by airguns in seismic surveys can affect behaviour, although real sonar systems, are highlighted as a key knowledge gap in the report of impacts in the marine environment are difficult to measure. A 2012 the Technical Subgroup on Underwater Noise (Van Der Graaf et al, experimental study conducted in sea cages found that fish swam faster 2012). in response to air gun noise, in tighter schools and closer to the bottom UNDERWATER NOISE 6

2.4 The balance of effects

Because the effects of noise interact, it can be difficult to differentiate Separating the effects of noise from other environmental disturbances between the impacts of noise on marine species. For example, changes can also be complex. According to Pickaver (2010), for example, the in behaviour may be caused directly by noise, or caused indirectly cables that carry electricity to the shore at offshore wind farms produce by physical damage arising from noise that leads to an inability to an electromagnetic field that some fish may avoid. In addition, the perceive communication calls or detect prey. It might be that prey displacement of one species could indirectly trigger the disappearance distribution is affected, reducing the ability of predators to forage of predators or an increase in prey. effectively. The impacts of noise must be viewed in a wider context, considering Researchers who mapped the underwater noise environment near a how the effects of noise on populations compare to those of other fuel receiving facility off Sha Chau Island in Hong Kong highlighted human pressures on the marine environment. As it remains an open the difficulty of understanding the impact of tanker noise on dolphins question how many marine animals are killed by noise, those pressures in the region (Würsig and Greene, 2002). It was unclear whether the that are known to kill marine species, such as fishing and pollution, dolphins had adapted to the noise, whether their hearing had been could be considered more important. It is also debatable whether damaged, whether important communication signals were being habitat displacement is a negative impact, particularly when resources masked, or whether noise even had an impact at all. such as food and space are abundant.

3. The ultimate effects of underwater noise on people and society

The human impacts of environmental change are often understood in terms of ecosystem goods, such as fish stocks used by humans for food, and ecosystem services, such as tourism. Both of these examples are relevant to underwater noise, which affects fish populations and may have implications for tourism associated with whales and dolphins. At present, however, there is little evidence to guide our understanding of the direction or magnitude of any effect, with studies focusing on the most sensitive species, rather than commercially important.

The results of research funded by the Norwegian Petroleum Directorate in 2009 suggest that noise from seismic survey guns both increased and decreased fish catches off Vesterålen, Norway, depending on the species and fishing method (Løkkeborg , 2010). Noise may have driven

Greenland halibut into nets, thus increasing catches. On the other hand, Dolphins use sound to hunt, communicate and navigate, but manmade noise may be pollack and line-caught halibut catches were reduced during the surveys. interfering with these signals.

4. Monitoring underwater noise

Prior to the MSFD, the law did not explicitly compel EU Member on Underwater Noise proposed compiling a database of loud impulsive States to monitor underwater noise. However, Member States will noises likely to cause significant impacts on marine animals, potentially need to coordinate their efforts to ensure that appropriate systems are in an EU-wide noise register. Guidance on measuring noise and in place in shared waters by the MSFD deadline in 2014. interpreting noise data is currently being developed.

Appropriate technologies and methods for monitoring are available, As part of the EU LIFE-funded project ‘Baltic Sea Information on the but a number of issues still need to be resolved for monitoring to Acoustic Soundscape’ (BIAS), partners in Denmark, Estonia, Finland, be effective. For instance, there are different ways of measuring and Germany, Poland and Sweden are collaborating to create a sound map expressing noise, and for comparison at national, European and of the Baltic Sea via 40 noise monitoring stations (SYKE, 2013). The international levels, data must be consistent. In addition, to avoid high project aims to define Good Environmental Status, as required under economic costs, the level of detail must be balanced against coverage the MSFD roadmap, and refine a measurement system for monitoring (Van der Graaf et al, 2012). In 2012, the MSFD Technical Subgroup underwater noise. UNDERWATER NOISE 7

5. Reducing the impact of underwater noise

According to Parsons et al (2009), the simplest way to reduce the can avoid piling, while air bubbles that absorb or deflect sound waves impact of underwater noise on marine life is to avoid carrying out and alternative piling hammers may help reduce piling noise. In 2009, noisy activities where and when noise-sensitive species are present. In the California Department of Transportation reported successfully practice, this is not always feasible, owing to competing interests, such employing air bubble ‘curtains’ to reduce noise from piling during as the need to generate renewable energy and income from tourism, bridge construction projects and protect fish (Reyff, 2009). There are and limited knowledge about the distribution of marine species. Risk further challenges associated with pile driving in deeper water or at mapping can provide information to aid in the avoidance of important higher current speeds. In addition, many ‘solutions’ may be costly in habitats. However, weighting of the importance of sensitive species will relation to other measures likely to improve the welfare of the species determine what impact is considered acceptable. being affected.

One recent study in the Mediterranean sought to understand whether Noise generated by boats is associated with moving parts in the engine, models based purely on environmental characteristics could be used flow around the hull and with ‘cavitation’ (the creation and collapse to accurately map beaked whale habitats without carrying out surveys of bubbles) caused by the rotation of propellers (Rako et al, 2013). (Azzellino et al, 2011). The researchers argue that their predictions Driving at the ‘design speed’ can help reduce noise. were of acceptable accuracy and suggest that risk maps generated through the same approach could be used to minimise noise impacts Some countries also recommend ‘soft-start’ approaches that progress on beaked whales. from quieter to noisier activity, for instance, in sonar and seismic surveys, and that noise activities are carried out in the presence of a Alternative technologies and construction techniques can directly trained marine mammal observer. reduce the noise associated with human activities. Floating wind farms

6. Knowledge gaps

Noise is just one of many pressures faced by marine species. Future ‘There is... growing concern of the cumulative studies will improve our understanding of the effects of underwater noise and its importance in the context of an environment that is effects of anthropogenic sound and other already at risk from other manmade threats. Key knowledge gaps stressors and how this can affect populations include: and communities... The additional threat • Does noise matter if animals remain in noisy areas or leave but of living in a noisy environment may push later return? already highly stressed marine animals into • What are the cumulative effects of less frequent, loud, impulsive noise? population decline with subsequent effects on • How strong are the effects of low-level, constant noise on marine communities and biodiversity.’ habitat displacement? Convention on Biological Diversity report (2012) • To what extent are animals capable of adapting to noise? • How are less well studied species affected by underwater noise?

Summary

Underwater noise from sources including shipping, energy production, The MSFD will soon require EU Member States to have strategies fishing and tourism has been found to affect the marine environment in in place for monitoring and, where necessary, mitigating underwater various ways. Impacts on species, including marine mammals and fish, noise. To inform these efforts, the best available evidence in this range from permanent physical damage to temporary displacement developing field will need to be used, and efforts in shared waters must from an area. However, for many species, the nature and severity of be coordinated. There is a need to define harmful levels of noise and effects remain uncertain and unproven. In particular, further research protect the most sensitive species. is needed to understand the long-term impacts of loud, infrequent noises and low-level continuous noise on marine life. UNDERWATER NOISE 8

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