Atenuação acústica em duas regiões distintas da Plataforma Continental do Sudeste Brasileiro

Abstract

This study assessed the acoustic attenuation in high-productivity regions of the southeastern Brazilian continental shelf, specifically examining how zooplank- ton biomass influences sound propagation. The research was conducted in two areas with contrasting oceanographic regimes: Arraial do Cabo/RJ, known for its upwelling system, and Sepetiba/RJ, characterized by more stable coastal waters. Oceanographic and biological data were collected during two Tactical System of Environmental Factors (STFA) project campaigns. The findings indicated that although zooplankton–induced acoustic attenuation was generally low, it varied significantly depending on the size fractions of the zooplankton and the sound fre- quencies analyzed. Larger zooplankton contributed more to attenuation at lower frequencies, while microzooplankton had a more pronounced impact at higher fre- quencies. Fluorescence was identified as a valuable tool for estimating zooplankton concentration and distribution, offering insights into how these organisms influence acoustic propagation. Future research should focus on exploring additional oceanic regions and bearing a broader range of biological and physical factors that may affect sound transmission in the marine environment.