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Underwater noise in the Baltic Sea a risk for fish and marine mammals

Underwater noise in the Baltic Sea a risk for fish and marine mammals

Press release 2017-01-25 at 9:05

Underwater noise in the Baltic Sea has been measured for the first time. According to an international project co-led by the Finnish Environment Institute, the level of human-introduced underwater noise is remarkable. However, the situation varies widely in different parts of the Baltic. High-level noise may adversely affect fish and marine mammals.

"The percentage of noise caused by shipping out of the total for sounds is highest in the southern Baltic area, particularly in the Danish straits. Conversely, there are areas in the Gulf of Finland where human-introduced noise is very rare. Because underwater noise travels long distances, its management requires international co-operation," explains Senior Adviser Jukka Pajala of the Finnish Environment Institute.

The Baltic Sea Information on the Acoustic Soundscape (BIAS) project studied Baltic Sea noise levels. Underwater noise is caused by a wide variety of activities in maritime areas, such as shipping and marine construction. Growth in shipping and the construction of marine wind farms are increasing underwater noise levels in the Baltic Sea.

The joint project, which unites countries in the Baltic region, has produced a number of tools to help authorities in planning the use of maritime areas and reduce the harmful impact of noise.

Noise causes changes in the behaviour of marine fauna

Noise that far exceeds the level of the natural soundscape can cause harm to entire animal populations. Disturbances in communication, changes in behaviour and even physical injury have been observed in fish and marine mammals. The soundscape is vital to fish because they use sound and hearing for communication, locating mates and avoiding predators. Marine mammals also use sound to locate food.

Although the harmful impacts of noise vary according to the time of year, sound is intensified significantly in the winter. In addition to this, water temperature and salinity stratification causes drastic changes in the speed of sound, thus also affecting how sound travels. New research data is needed for a more precise measurement of seasonal variations and to examine the sensitivity of endemic species.

Picture is showing a sound pressure map of the Baltic Sea. Median value at a one-third octave band of 125 Hz in 2014. The map includes both natural and human-introduced noise. The largest shipping lanes are clearly shown.

Noise maps provide support for planning maritime areas

Sound pressure maps covering the entire area of the Baltic Sea were processed for the first time by means of modelling. The maps are based on measurements taken at 38 points throughout the Baltic Sea. The situation of the year measurements were taken (2014) is used as the baseline, to which future noise measurements will be compared. Noise maps can be used in the planning of maritime area uses, by combining them with, for example, information on the distribution of species and nature reserves.

The BIAS project meets the objective of the Marine Strategy Framework Directive. The aim of the Directive is to achieve Good Environmental Status (GES) of the EU's marine waters by 2020. In addition to this, underwater noise must be limited to a level that causes no harm to marine ecosystems.

The Baltic Sea Information on the Acoustic Soundscape (BIAS) project drafted underwater noise measurement and analysis guidelines, created a joint, Baltic-wide organization and developed a tool for managing human-introduced noise. The project also increased public awareness of the acoustic soundscape and harm caused by noise. The project was funded by the European Union LIFE+ 11ENV program and participating organizations. Finland, Sweden, Estonia, Poland, Germany and Denmark participated in the project, which ran from 2012 to 2016.