Fontes sonoras na paisagem acústica marinha da Baía de Todos os Santos, Nordeste do Brasil

Abstract

The sounds within the soundscape play a crucial role in the ecology of many species, being used for various vital functions and obtaining essential information from the environment. In this study, we investigated some biological and anthropogenic sound sources that compose the underwater soundscape of Todos os Santos Bay (BTS) through two chapters. The first chapter focuses on biological sounds, investigating the acoustic patterns of whistles produced by the Guiana dolphin (Sotalia guianensis), a dolphin species resident in BTS. In the second chapter, human activities that affect the underwater soundscape of BTS are investigated through two articles, with the first describing the sound generated by the practice of fishing with explosives while the second aims to describe the sounds produced by vessel traffic in the region. The data collected was considered within the long-term research program on the behavioral ecology of the Guiana dolphin and the soundscapes of the BTS between October 2016 and May 2018. Recordings were made from a boat-based survey platform using an HTI-90 min hydrophone (sensitivity of 165 dB re 1 V/μPa) connected to a TASCAM DR-40 digital recorder, recording at a depth of 5 to 7 meters. During this period, 24 hours and 55 minutes of biological sounds and 20 hours and 21 minutes containing information on anthropogenic sounds were collected. The analysis provides insights into the acoustic variability of the Guiana dolphin, identifying the whistle sound patterns in a population with no previous acoustic records, and reveals potential negative impacts on the entire local underwater ecosystem caused by certain human activities. Through this study, three sound sources present in BTS were characterized: one biological and two anthropogenic. This is important because the detailed characterization of these sources allows for a better understanding of how natural animal communication patterns and human activities modify the acoustic landscape of the region.