Guiding principles for assessing the impact of underwater noise

Over the last two decades, marine noise pollution has become increasingly recognized as an issue of major significance. The issue has become a primary focus of marine mammal research, but is also of concern to the public and policy makers. The result has been efforts involving a variety of disciplines, and relevant legislation and associated guidance are now in place in many parts of the world. Most current mitigation efforts are directed at reducing the risk of injury from exposure to intense noise, although the effectiveness of such mitigation measures in terms of risk reduction has rarely been quantified. Longer-term chronic impacts of noise including disturbance or masking of sounds critical for feeding and reproduction have received substantially less attention in management. New technologies are being developed for a number of activities which can substantially reduce noise inputs into the marine environment. As with other forms of pollution, reducing input at source is likely...

Underwater noise from human activities appears to be rising, with ramifications for acoustically sensitive marine organisms and the functioning of marine ecosystems. Policymakers are beginning to address the risk of ecological impact, but are constrained by a lack of data on current and historic noise levels. Here, we present the first nationally coordinated effort to quantify underwater noise levels, in support of UK policy objectives under the EU Marine Strategy Framework Directive (MSFD). Field measurements were made during 2013–2014 at twelve sites around the UK. Median noise levels ranged from 81.5–95.5 dB re 1 μPa for one-third octave bands from 63–500 Hz. Noise exposure varied considerably, with little anthropogenic influence at the Celtic Sea site, to several North Sea sites with persistent vessel noise. Comparison of acoustic metrics found that the RMS level (conventionally used to represent the mean) was highly skewed by outliers, exceeding the 97 th percentile at some frequencies. We conclude that environmental indicators of anthropogenic noise should instead use percentiles, to ensure statistical robustness. Power analysis indicated that at least three decades of continuous monitoring would be required to detect trends of similar magnitude to historic rises in noise levels observed in the Northeast Pacific. Underwater noise pollution can have adverse effects on marine organisms 1–4 and appears to be correlated with global economic growth 5. Sources of noise such as shipping 6 , pile driving 7 , geophysical seismic surveys 8,9 , and naval sonar operations 10 have each been linked to detrimental effects on marine fauna. Long-term measurements from deep-water sites in the Northeast Pacific have shown that low-frequency (<~50 Hz) noise levels in that ocean basin increased markedly (by ~10 dB) between the 1960 s and mid-1990 s 11,12. Since then, this trend has largely levelled off or begun to decline 13 , and data from the past decade suggest that more recent trends in noise levels for other ocean basins may also be mixed 14. The extent to which these open-ocean trends apply to the shallower continental shelf seas where human activity is concentrated is unclear 15 , since long-term datasets for these regions are lacking. Sources of anthropogenic noise can be categorised as impulsive or continuous 16. Each type is associated with particular effects on marine fauna, and each requires a bespoke management approach to mitigate potential impact 17. Impulsive noise consists of brief, discrete sounds with a sudden onset, such as acoustic pulses from explosions, pile driving, or seismic airguns. Such sources can elicit acute effects on animals including permanent or temporary auditory damage 16 , physiological stress, and antipredator responses (e.g. displacement 18). For example, short-term displacement of harbour porpoise has been reported in response to pile driving 7 and seismic surveys 19 , and in situ exposure of European seabass to pile driving has been observed to induce physiological stress 20. Such noise sources are associated with activities that are typically subject to a regulatory consenting process , and can therefore be managed through licence conditions required by these regulatory processes. Continuous anthropogenic noise is primarily generated by shipping. Since shipping routinely crosses international boundaries, management of shipping noise requires a coordinated international response (e.g. through the International Maritime Organisation). The widespread increase in noise levels caused by continuous sources has been associated with acoustic masking of biologically important cues 18,21 , disruption to foraging 22 , increased physiological stress 2,6 , and developmental deficiencies 23 in aquatic species. Although continuous noise sources are typically less intense than impulsive sources, the pervasive presence of continuous noise from shipping could lead to more significant and widespread effects 2,24. This is of particular concern given that vessel noise can affect species that mediate important ecosystem functions 25 , as well as altering predator-prey dynamics 26 .

Advances in experimental medicine and biology, 2016

The project conducts application-oriented research on impacts of underwater noise on marine vertebrates in the North and Baltic Seas. In distinct subprojects, the hearing sensitivity of harbor porpoises and gray seals as well as the acoustic tolerance limit of harbor porpoises to impulsive noise from pile driving and stress reactions caused by anthropogenic noise is investigated. Animals are equipped with DTAGs capable of recording the actual surrounding noise field of free-swimming harbor porpoises and seals. Acoustic noise mapping including porpoise detectors in the Natura 2000 sites of the North and Baltic Seas will help to fully understand current noise impacts.

2016

Assessment of underwater noise is increasingly required by regulators of development projects in marine and freshwater habitats, and noise pollution can be a constraining factor in the consenting process. Noise levels arising from the proposed activity are modelled and the potential impact on species of interest within the affected area is then evaluated. Although there is considerable uncertainty in the relationship between noise levels and impacts on aquatic species, the science underlying noise modelling is well understood. Nevertheless, many EIAs do not reflect best practice, and stakeholders and decision makers in the EIA process are often unfamiliar with the concepts and terminology that are integral to interpreting noise exposure predictions. In this paper, we review the process of underwater noise modelling and explore the factors affecting predictions of noise exposure. Finally, we illustrate the consequences of errors and uncertainties in noise modelling, and discuss future research needs to reduce uncertainty in noise assessments.

2000

In recent years the volume and spatial extent of anthropological noise pollution of the oceans has become clearer as underwater acoustic research has matured in the open literature following the run-down of the cold war. In parallel, the range, depth and dependence of marine mammals on sound for communication and environmental sensing has been brought sharply into focus by an

Anthropogenic underwater noise is now recognized as a worldwide problem, and recent studies have shown a broad range of negative effects in a variety of taxa. Underwater noise from shipping is increasingly recognized as a significant and pervasive pollutant with the potential to impact marine ecosystems on a global scale. We reviewed six regional case studies as examples of recent research and management activities relating to ocean noise in a variety of taxonomic groups, locations, and approaches. However, as no six projects could ever cover all taxa, sites and noise sources, a brief bibliometric analysis places these case studies into the broader historical and topical context of the peer-reviewed ocean noise literature as a whole. The case studies highlighted emerging knowledge of impacts, including the ways that non-injurious effects can still accumulate at the population level, and detailed approaches to guide ocean noise management. They build a compelling case that a number of anthropogenic noise types can affect a variety of marine taxa. Meanwhile, the bibliometric analyses revealed an increasing diversity of ocean noise topics covered and journal outlets since the 1940s. This could be seen in terms of both the expansion of the literature from more physical interests to ecological impacts of noise, management and policy, and consideration of a widening range of taxa. However, if our scientific knowledge base is ever to get ahead of the curve of rapid industrialization of the ocean, we are going to have to identify naïve populations and relatively pristine seas, and construct mechanistic models, so that we can predict impacts before they occur, and guide effective mitigation for the most vulnerable populations.

Journal of International Wildlife Law & Policy, 2007

Trends in Ecology & Evolution, 2010

IEEE Journal of Oceanic Engineering, 2006

Effects of Sound on the Marine Environment (ESME) is a computer model of the effects of underwater sound on marine life. The modular design behind the ESME model is motivated by the sonar equation, with subcomponent models for characterization of the source, for modeling of sound transmission through a medium, and for receiver properties (e.g., hearing abilities, behavioral responses to sound, and receiver distribution and abundance). Each subcomponent of ESME is intended to capture the current state of understanding in the relevant scientific field and to be capable of being updated as the understanding in the field advances. ESME is envisioned to have three primary applications: 1) retrospective studies of historical data, 2) predictive modeling of anticipated outcomes from a given scenario of sound in a marine environment, and 3) prescriptive guidance for research investments and efforts that will likely have the greatest effect on increasing confidence in decisions about underwater sound use and its effects.