The sea is not silent. For many marine organisms, sound is important for orientation, communication, feeding and avoiding danger. Underwater noise generated by human activities, primarily maritime traffic, is becoming an increasingly serious form of marine pollution.
The Institute is a partner in the UNDERSEA project, implemented within the Interreg Italy-Croatia Programme, whose aim is to improve cross-border monitoring, assessment and reduction of underwater noise in the Adriatic Sea. Our experts coordinate the implementation of a joint underwater acoustic monitoring network, while also participating in partner training, instrument calibration, data collection and processing, and communication of the results.
The UNDERSEA project builds on the Interreg IT-HR SOUNDSCAPE project, in which the Institute was the lead partner. Due to the exceptional circumstances of the COVID-19 pandemic, SOUNDSCAPE also included monitoring of underwater noise in the northern Adriatic during a period of reduced human activity at sea. This provided a rare and valuable baseline for comparison with the current situation, following the return of the usual intensity of maritime traffic, fishing activities, tourism and recreational boating.
Measurements are carried out using passive acoustic recorders, devices that record sounds in the sea. The measurements used autonomous underwater recorders equipped with broadband hydrophones, recording sound in the range from 10 Hz to 20 kHz, with a sampling rate of 48 kHz and 16-bit resolution. Before deployment, the hydrophones were calibrated in the range from 63 Hz to 20 kHz, and sound pressure levels were calculated every 20 seconds.
The results of previous research conducted by Croatian and Italian scientists through two research projects, covering spring periods that included the month of April in 2020, 2021 and 2025 at three monitoring stations in the northern Adriatic, have now been published as a chapter in the open-access book The Effects of Noise on Aquatic Life IV, under the title “From COVID-19 to Business-as-Usual: Sound Pressure Levels in the Busy Shallow Adriatic Basin”.
The publication clearly shows why it is necessary to systematically listen to the Adriatic. However, the full picture will become clearer only after the processing of data collected through the UNDERSEA project, covering a full year of measurements and all monitoring stations. This is particularly important because of the expected increased influence of tourism and recreational boating on underwater noise levels in the Adriatic during the summer months. The results of the project represent an important step towards better coastal management, more effective protection of the marine environment, and the more sustainable development of the Adriatic.
