Underwater noise from human activities is increasing in the marine environment. Such sounds can have a significant negative impact on animals in a number of ways, from effects on single individuals to potential effects at the population level.
There are many different sources of underwater noise e.g. construction and operation of offshore facilities, shipping, dredging, geological prospecting, etc. Sound can travel long distances under water and some frequencies can even travel across ocean basins as sound propagates more efficiently in water than in air. The intensity of sound can readily be measured, but impacts of sound are not well understood in many animal species, making management of underwater noise a complex task.
In 2013, HELCOM Copenhagen Ministerial Declaration agreed that the level of ambient and distribution of impulsive sounds in the Baltic Sea should not have negative impact on marine life and that human activities that are assessed to result in negative impacts on marine life should be carried out only if relevant mitigation measures are in place.
The HELCOM Expert Group on Underwater Noise (EG Noise) was established to prepare and facilitate the implementation of a roadmap to building a knowledge base on underwater noise in a short term (2015-2017).
The Life+ project Baltic Sea Information on the Acoustic Soundscape (BIAS project) produced soundscape maps in 2016, showing the underwater noise generated by commercial vessels, the major source of human-induced underwater noise in the Baltic Sea. Seasonal soundscape maps were produced for the demersal, pelagic and surface zones. These soundscape served as a baseline for the development of monitoring programme of continuous noise in the Baltic Sea.
New soundscape maps for 2018 have been developed within a dedicated activity on underwater noise (A4) in the HELCOM BLUES project and together with the national monitoring data available in the HELCOM database on continuous noise will be used to elaborate the section on continuous noise to be part of HOLAS3, the third holistic assessment of the Baltic Sea (2016-2021).
A regionally organized registry of impulsive events in the Baltic Sea region is also available. Such registry makes an account of the number of days with activities that create impulsive sounds that can be harmful for marine animals and make it possible to evaluate cumulative impacts of noise. Data contained in the registry will be utilised for the assessment of impulsive noise in HOLAS3.
When it comes to measures addressing underwater noise, the evaluation of the implementation of the Regional Baltic Underwater Noise Roadmap 2015-2017 adopted at the HELCOM 37 meeting (Annex 3 of the Outcome of HELCOM 37-2016) served as basis for elaboration of the Regional Action Plan on Underwater Noise adopted as HELCOM Recommendation 42-43/1 in 2021.