Research of the impact of underwater noise

Research of the impact of underwater noise (sound pollution) on dolphins and their habitat use began in 2004 through the application of passive bioacoustics around the Lošinj archipelago. At great depths, where visibility is reduced, dolphins rely on their hearing to understand their environment. Over time, they have evolved a highly-sophisticated system of sound production and reception called echolocation, which is used for communication, prey detection, locating potential threats, orientation and navigation. The sound they make varies according to their activities. In coastal waters, due to strong human pressure, increased underwater noise may inhibit dolphins from acoustically interpreting their environment. The most common effect is behavioural disturbance, which results in localized displacement of the animals and the avoidance of extremely noisy areas. The use of hydrophones (passive acoustic recording devices) allows us to study dolphin vocalization and to monitor the effects of noise pollution in their habitats. Long-term acoustic monitoring of sea ambient noise in the Cres –Lošinj archipelago is carried out on predefined locations using a hydrophone connected to a digital recorder. In addition, data on vessel presence is collected simultaneously. This method allows us to identify critical areas, in terms of noise and vessel presence. Analysis shows that the progressive increase of vessel traffic has contributed significantly to the intensity of underwater noise and that in turn has led to dolphin changing the use of their habitat.