Underwater noise

Assessment of progress towards the achievement of Good Environmental Status for noise.

The extent to which Good Environmental Status has been achieved

The achievement of Good Environmental Status for underwater noise in the UK is uncertain. Research and monitoring programmes established since 2012 have provided an improved understanding of the impacts of sound on marine ecosystems.

How progress has been assessed

Step 1: We agreed characteristics of Good Environmental Status for Underwater Noise

In the Marine Strategy Part One (HM Government, 2012) the UK set out the following high-level, qualitative description of what the marine environment should look like when Good Environmental Status is achieved for Underwater Noise:

  • Loud, low and mid frequency impulsive sounds and continuous low frequency sounds introduced into the marine environment through human activities do not have adverse effects on marine ecosystems:
  • Human activities potentially introducing loud, low and mid frequency impulsive sounds into the marine environment are managed to the extent that no significant long-term adverse effects are incurred at the population level or specifically to vulnerable/threatened species and key functional groups.
  • Continuous low frequency sound inputs do not pose a significant risk to marine life at the population level, or specifically to vulnerable/threatened species and key functional groups, for example through the masking of biologically significant sounds and behavioural reactions.

The UK aims that loud, low and mid frequency impulsive sounds and continuous low frequency sounds introduced into the marine environment through human activities are managed to the extent that they do not have adverse effects on marine ecosystems and animals at the population level.

Step 2: We set targets to assess the extent that the characteristics of Good Environmental Status were achieved

Two operational targets were set to put in place the tools needed to demonstrate the extent to which Good Environmental Status, as articulated in the criteria for Underwater Noise in the Commission Decision 2010/477/EU (European Commission, 2010), had been achieved.

Target 1: To establish a ‘noise registry’ to record, assess, and manage the distribution and timing of anthropogenic sound sources measured over the frequency band 10 Hz to 10 kHz, exceeding the energy source level 186 dB re 1 μPa² m² s; or the zero to peak source level of 224 dB re 1 μPa² m² over the entire UK hydrocarbon licence block area.

Target 2: Surveillance indicator to monitor trends in the ambient noise level within the ⅓ octave bands 63 and 125 Hz (centre frequency) (re 1μPa RMS; average noise level in these octave bands over a year) measured by observation stations.

Step 3: We set up indicators

Indicators were used to establish these operational targets, working with colleagues in OSPAR to ensure a coordinated approach for the convention area.

Step 4: We evaluated progress

We looked at the progress made with the establishment of the noise registry and the monitoring programmes for ambient noise to assess what more needed to be done to achieve our Good Environmental Status aim.

Progress since 2012

Noise Registry

A Marine Noise Registry has been developed to record impulsive sound from various activities in the UK seas, which feeds into a European registry through the OSPAR Convention. The registry holds data for seven different impulsive sound generating activities:

  1. seismic survey
  2. sub-bottom profiling
  3. impact pile driving
  4. unclassified Ministry of Defence activity
  5. detonation of explosives
  6. acoustic deterrent devices
  7. multi-beam echosounders (≤12 kHz)

Programme of measures

A programme of measures has been put in place. Most activities creating sounds exceeding levels judged to be harmful to marine animals sensitive to disturbances, such as pile driving, must be licensed or notified and conducted under strict conditions.

The main measures consist of:

  • The Marine Noise Registry where the data are recorded to assess levels and distribution of impulsive noise sources to determine whether they could potentially compromise the achievement of Good Environmental Status.
  • UK Marine Licensing regimes which cover most activities creating potentially harmful sound. As part of marine licensing, potential impacts associated with a development are considered by regulators before licences are granted. This can include levels and impacts of noise as well as mitigation, where relevant.
  • Impact assessments, undertaken to protect habitats and species identified as Natura 2000 sites and European Protected Species by the Habitats Directive (92/43/EEC) (European Council, 1992). Noise risk assessments are a standard component of the impact assessment processes for many noise-generating activities and are used in implementing these instruments.
  • Marine planning, which will provide insight into where best to conduct certain activities, particularly regarding multiple use (cumulative effects) as our understanding of the levels, patterns and impacts of underwater noise improves.
  • Monitoring and research programmes which have established recent ambient noise levels at several sites in the Greater North Sea and Celtic Seas. Research programmes are helping to provide a more robust picture of the impacts of sound on marine ecosystems and animals. There are presently no threshold values agreed at UK level to determine the risk of adverse ecological impact.
  • Monitoring for underwater noise using autonomous underwater recorders moored to the seabed. During 2014-2014 11 locations were monitored: 10 locations in the North Sea (9 locations in the Northern North Sea by Marine Scotland, and 1 location in the Southern North Sea by Cefas), and one location in the Celtic Seas (by the University of Exeter). Detection of trends will require several decades of monitoring.
  • Coordination and collaboration: The UK coordinates with OSPAR Contracting Parties through the Intersessional Correspondence Group on Noise (ICG-NOISE) and is collaborating with other OSPAR Contracting Parties on two projects for joint noise monitoring, one covering the Greater North Sea, the other covering the Atlantic Area.

Outstanding issues

The key knowledge gap is to understand whether and how levels of man-made marine noise lead to effects at the population and ecosystem scales, particularly for vulnerable/threatened species and key functional groups, and how to quantify the risk of impact at these scales. Risks to populations need to be more clearly established in order to develop proportionate measures.

There is considerable evidence for the effects of impulsive sound on individual marine organisms. The effects can be subtle (such as hearing sensitivity reduction or physiological stress) or obvious (such as changes in behaviour, death), however, there is uncertainty over the potential impacts on individual vital rates, and on populations and ecosystems.

While there is clear and mounting evidence for negative effects of manmade noise on individual animals (and effects on animal interactions) which indicates a risk of population-level impacts, it is scientifically challenging to isolate the effect of manmade noise on a particular animal population or ecosystem from other potential sources of variability.

Achievement of targets

The two operational targets proposed in 2012 have both been set up, become operational and been achieved. The Noise Registry to record the distribution and timing of man-made impulsive sound sources measured over key frequencies is now in use. The surveillance indicator to monitor trends in the ambient noise measured by observation stations has been established and information is being recorded at observation status.

Indicators used to assess targets

Impulsive noise
Ambient noise
 

Two indicators are used to asses targets for underwater noise in the Celtic Sea and the Greater North Sea:

  1. Impulsive noise indicator: records impulsive sound (developed both nationally and together with OSPAR Contracting parties (see OSPAR, 2017)).
  2. Surveillance indicator for ambient noise; records ambient "continuous" noise

Human activities introduce many forms of energy into the marine environment including sound, light and other electromagnetic fields, heat and radioactive energy. The Marine Strategy Framework Directive descriptor “introduction of energy, including underwater noise” aims to ensure that “the introduction of energy, including underwater noise, is at levels that do not adversely affect the marine environment” (European Commission, 2008; 2010). Underwater sound is thought to be the most widespread and pervasive form of energy input by human activities into the oceans (Tasker and others, 2010). The amount of underwater sound resulting from human activities, and its associated effects on ecosystems, has likely increased since the advent of steam-driven ships, although there have been very few studies that have quantified these changes (Tasker and others, 2010).

Sound sources can be categorised as continuous or impulsive. Impulsive sounds are pulse-like sounds of short duration and start suddenly (such as explosions, impact pile driving, seismic airguns, sonar), while continuous sounds are long lasting and do not have pulse characteristics (such as shipping, dredging). Impulsive sounds may be repeated at intervals (such as in pile driving), and this repetition may lead to sound diffusing with distance and becoming indistinguishable from continuous sound. In addition, the spread of sound is affected by its frequency, with high frequency sounds unable to propagate as well in the marine environment whereas lower frequency sounds can travel great distances in sufficiently deep waters.

In 2015 impulsive sound, especially from seismic surveys, was found to be prevalent in the Greater North Sea, but some events were also recorded in the Celtic Sea, including the deep waters off the northwest coast of Scotland, and in the western English Channel and Irish Sea.

The ambient noise indicator recorded field data in 2013 and 2014 from activities such as shipping which provides baseline levels for a number of monitoring locations in the Greater North Sea and the Celtic Sea. These will serve as a benchmark to assess future ambient noise levels.

Moving forward

We will work with other countries sharing our seas to develop threshold values for levels of impulsive and continuous sound which are likely to cause harm at population so that common quantitative targets can be established in the future.

We will work in international forums such as IMO to ensure that continuous underwater noise from shipping is robustly controlled at global level.

References

Acknowledgements

European Commission (2008) ‘Directive 2008/56/EC of the European Parliament and of the Council of 17 June 2008 establishing a framework for community action in the field of marine environmental policy (Marine Strategy Framework Directive)’ Official Journal of the European Union L 164, 25.6.2008, pages 19-40 (viewed on 21 September 2018)

European Commission (2010). Commission Decision of 1 September 2010 on criteria and methodological standards on Good Environmental Status of marine waters (notified under document C (2010) 5956) (Text with EEA Relevance) (2010/477/EU). Official Journal of the European Union L232, 2.9.2010, p. 14-24. (viewed on 5 July 2018)

European Council (1992) Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora. Official Journal of the European Union L 206, 22.7.1992, p. 7-50. (viewed 1 October 2018)

HM Government (2012) Marine Strategy Part One: UK Initial Assessment and Good Environmental Status. December 2012. (viewed on 5 July 2018)

OSPAR (2017) Intermediate Assessment 2017 (viewed on 21 September 2018)