Noise is not only a land problem generated by various forms of transport and construction activities. Underwater noise is a significant pressure for many marine organisms, especially porpoises and fish.
Marine mammals, many species of fish, and some invertebrates communicate via sound to find partners, potential prey, avoid predators and threats, and for navigation.
Sound is only referred to as ‘noise’ when it is likely to have a negative effect on marine life. It can travel long distances underwater because sound travels more effectively through the water than it does through the air. Sound intensity is easy to measure, but the effect of sound is not well understood in many animal species, making underwater noise management a complex task.
How does underwater noise pollute the sea?
Both natural and anthropogenic noise occur in marine waters. The former is short-lived and generated by wind and wave motion, while the latter is continuous or impulsive.
The sources of impulse noise in Polish sea areas are underwater explosions, seismic surveys, sonar operation and, in the future, also activities involving driving piles during the construction of offshore wind farms.
The sources of continuous noise are, however, maritime transport, sea tourism and fishing, and in the future will also be the operation of offshore wind farms.
Anthropogenic underwater noise can cause animals damage to their body integuments and even death, lead to behavioral changes, or mask other sounds that may be relevant to marine organisms. These factors can lead to negative changes at the level of both a given individual and the entire population. An example is the porpoise, which has an evolutionarily advanced echolocation system. As a result of the strong intensity of extraneous sounds, the hearing aid damages him and prevents him from navigating properly (including identifying obstacles) and gaining food.
Due to this strong behavioral response from the harbor porpoise and some fish species, it is very important to protect the marine environment from this pressure. This element, while still poorly defined in terms of threshold values for good and bad marine environment, is still the subject of intense work at European and national level. The issue of monitoring studies is also similar.
How is underwater noise tested?
Currently, there are few noise measurement data available in Polish sea areas, only for relatively short periods. The analyzes so far have used continuous measurements carried out as part of the international BIAS project in the entire Baltic Sea, but they only cover one year (2014). As part of this research, the highest level of underwater noise was recorded in the Pomeranian Bay – the shipping route to Świnoujście and Szczecin. In Poland, since 2015, the CIEP has been conducting a pilot monitoring of underwater (continuous) noise in designated locations, in accordance with the sea water monitoring program. Information on impulse noise is also successively collected, currently only on the basis of data from recorded explosions (data source: Ministry of National Defense). Still, the level of uncertainty and lack of knowledge is high.
Under the Marine Strategy Framework Directive – Underwater noise and other energy sources constitute Feature 11 within the set of status and pressures characteristics analyzed in detail in the Marine Water Action Program (PMM). As part of aPOWM, we respond to these problems by proposing actions aimed primarily at filling the knowledge gap about this pressure, but also specific actions aimed at real reduction of this pressure. The proposed actions include: