Underwater noise and other forms of energy input

Human activities at sea can introduce several forms of energy into the marine environment (e.g. underwater noise, thermal pollution, electromagnetism and artificial light). The increase of energy levels in the seas and oceans due to emissions from human activities has been identified to cause various impacts on the marine ecosystem.

Underwater noise is addressed at the technical level as a priority in this stage of the Marine Strategy Framework Directive implementation. The reason for prioritisation of underwater noise is that over the last century human activities at sea increasingly added artificial sounds to the marine environment and changed the ‘soundscape’ for marine fauna. These anthropogenic sounds may be long lasting (continuous noise) or of short duration (impulsive noise). Both continuous and impulsive anthropogenic noise have been recognized as a problem with a broad range of negative effects in a variety of marine species (Andre et al., 2011; Williams et al., 2015).

Many publications refer to effects of human induced underwater noise e.g. on marine mammals especially on cetaceans that are highly vocal and use sound for communication, food-finding, reproduction, detection of predators and navigation. Anthropogenic noise can mask these important signals. Other observed effects of noise on marine mammals include changes in vocalization, stress, changes in respiration, increased swimming speed, orientation away from the sound source, sudden and longer dives, shifts in migration paths, stranding, changes in foraging and breeding behaviour, as well as physiological damage and mortality. Other species, such as fish, birds, reptiles and invertebrates can also be negatively impacted by underwater noise with impacts on behaviour, reproduction and growth. (EIA, 1998; NRC, 2000; Weilgart, 2007; Erbe, 2012; Tasker et al., 2010; Popper et al., 2020).
Other forms of energy input such as thermal pollution, electromagnetism and artificial light have all been identified to cause impacts on marine species. Magnetic fields generated by cables may impair the orientation of fish and marine mammals and affect their migratory behaviour (Gill et al., 2012; Merk, 2009). Heat created by the transfer of electric energy through submarine cables leads to subsequent warming of the surrounding environment. Night-time artificial lighting from coastal development, shipping and offshore infrastructure has been known to disrupt navigation, increase mortality, alter spatial and temporal activity patterns of marine birds, turtles and fish (Witherington et al., 1991; Bourgeois et al., 2009; Merkel, 2010; Becker et al., 2012).

In relation to 'Underwater noise and other forms of energy', the Marine Strategy Framework Directive considers that 'good environmental status' is achieved when ‘Introduction of energy, including underwater noise, is at levels that do not adversely affect the marine environment.'

General outcomes from the regional assessments

The first assessment of Impulsive Noise Indicator was developed to show the distribution and intensity of reported activity in the North-East Atlantic (OSPAR Maritime Area) in 2015. The assessment provides the first detailed information on the distribution of reported impulsive sound sources at the regional scale. Reported activity was more prevalent in the northern and eastern North Sea, to the west of Scotland and in the Skagerrak, and was largely due to seismic survey activity. Sound sources categorised as Low or Very Low intensity were more common than higher intensity sources. This distribution is likely to vary year by year, depending upon the activities undertaken.

Underwater noise from human activities management and assessment is under development in the Baltic Sea region. Soundscape maps were developed in 2016, showing the underwater noise generated by commercial vessels, the major source of human-induced underwater noise in the Baltic Sea. These soundscape maps will serve as a baseline for the development of monitoring and assessment of ambient noise in the Baltic Sea. A regionally organized registry of impulsive events in the Baltic Sea region has been also launched.

Underwater noise assessment is not available for the Mediterranean nor for the Black Sea. Noise from human activities is an objective of the Integrated Monitoring and Assessment Programme adopted by the contracting parties of the Barcelona Convention (EO 11 Energy including underwater noise), but it is still under development. It includes two candidate indicators, addressing impulsive and continuous sound.

Outcomes from the MSFD assessments

In 2018, Member States had to update the Good Environmental Status (GES) assessments performed under Marine Strategy Framework Directive Article 8. The present dashboard displays the overall status reported by countries for the features, where the results show which is the percentage of assessments where GES has been achieved, not achieved or is unknown or not assessed.