Caracterização de paisagens acústicas costeiras sob influência de fontes sonoras antrópicas no estado do Rio de Janeiro, Brasil

Abstract

The soundscape is the set of all types of sounds present in a certain environment. An acoustic approach involving varied acoustic metrics has not yet been applied to the study of the acoustic environment on the coast of Rio de Janeiro. The present work aims to fill this gap in the knowledge of the coastal region of Rio de Janeiro under both a temporal and a spatial aspect. The first chapter presents a temporal approach, in which an autonomous acoustic recorder was deployed at a depth of 20 m. The programmed daily recording cycle was of 30-minute recordings at 15-minute intervals with a 96 kHz sample rate. Analyses of sound pressure levels, acoustic complexity, automatic detection of biological signals and AIS vessel registrations were performed. Sounds from different sources contributed to the local soundscape, with sounds of artificial origin and biological origin. Daylight hours presented higher sound pressure values in the frequency bands between 25 and 63 Hz and in the frequency bands between 794 and 39 810 Hz (MW, p <0.01). Night hours presented higher values in the frequency bands between 100 and 199 Hz (MW, p <0.01). A total of 2290 delphinid signal detections occurred, distributed throughout 52 detection events. The presence of AIS vessels did not present a clear temporal pattern, however there was a significantly higher occurrence (MW, p <0.01) of vessels during the daylight hours. The simple linear regression showed a positive relation between the number of vessels and the sound pressure values in 28 frequency bands. LFACImin obtained higher values than HFACImin. Both were higher were higher at night than during the day (MW, p <0.01). LFACImin and HFACImin were significantly higher during third and first quarter lunar phases (KW, p <0.01). The second chapter presents a spatial approach, in which fifteen collection sites were distributed in the bays of Guanabara, Sepetiba and Ilha Grande. Presential recordings and counting of artificial sound sources were carried out. Sound pressure, acoustic complexity and bioacoustic activity analyses were performed. There was a decrease in sound pressure levels and an increase in the acoustic complexity from Guanabara Bay to Ilha Grande Bay, with intermediate values in Sepetiba Bay. The sites with the highest values of sound pressure and lower acoustic complexity were those with a larger number of vessels, with a significant correlation between these factors (Spearman R, p <0.01). A cluster analysis divided the sites into two groups, which were classified as "impacted" and "non-impacted". Comparisons between these groups indicated that the impacted sites present sound pressure values at least 10 dB higher, as well as a higher number of sound sources and less acoustic complexity. The bioacoustic activity and the type of bottom sediment also influenced the acoustic complexity, with sites of high bioacoustic activity and mud presenting higher complexities and lower noise levels than sand and low activity sites. The results indicate that multiple factors influence the coastal soundscape and that the anthropic presence reduces the natural variability of the landscape