Fatores naturais e antrópciso que colaboram para a paisagem acústica submarina da APA de Guapi-Mirim, Baía de Guanabara (RJ)

Abstract

Passive Acoustic Monitoring has presented remarkable progress, as it allows us to collect data passively and continuously, to understand the activities that occur in the aquatic environment and, consequently, the soundscape of a certain region. The soundscape represents a unique and particular characteristic of the different sounds present in a given environment, whether of natural or artificial origin, providing us with details about the habitat, on how animals use sounds to survive and on how anthropogenic activities harm the environment and its resident organisms. The present study carried out recordings at two points in Guanabara Bay: at Bouy 5 (near the Guapi-mirim MPA) and in Machado’s Rock. The acoustic data were recorded continuously, recording periods of 24 hours at both points, having, in a total of 10 days of collection, 240 hours of recording in Bouy 5 and 120 hours in Machado’s Rock. First, the data were submitted to TOL (Third Octave Levels) analyses to calculate sound pressure values for each frequency band in one third of an octave, where the frequency bands selected for analysis were: 63 Hz, 125 Hz, 1 kHz and 10 kHz. The highest mean sound pressure values in Bouy 5 was 89.9 ± 2.9 dB re 1 μPa in the frequency band of 63 Hz, recorded on 25/04/2022 and in Machado’s Rock it was 94.2 ± 4.7 dB re 1 μPa in the frequency of 1 kHz, during the day of 23/02/2022. The results showed that the soundscape of Bouy 5 was dominated by sounds of fish and crustaceans, occupying frequencies from 70 Hz to 2 kHz and from 3 kHz to 20 kHz, respectively, where higher sound pressure values were found during the night. In Machado’s Rock, anthropic noises at frequencies between 3 kHz and 40 kHz were very dominant and sound pressure values were higher during the day. The present study aims to fill the gaps in the acoustic knowledge not only of the Guapi-mirim MPA, but also of Guanabara Bay, with results of sound pressure values during the night period. The implementation of continuous acoustic monitoring during light and dark hours is extremely important, especially in coastal regions and marine protected areas, as it allows us to have a complete view of the soundcape of the area and define mitigating actions, putting into practice more effective management plans to minimize recurrent noise pollution in these regions.