Paisagem acústica submarina: padrões acústicos de invertebrados bentônicos

Abstract

Over the past two decades, soundscape monitoring has evolved as an important tool for the characterization and evaluation of several aspects of marine ecosystems. Among these environments, rocky shores are dominated by benthic invertebrates and have a characteristic acoustic signature. Most of these organisms are known to produce impulsive and bandwidth sounds. Were evaluate underwater soundscape patterns in a Cabo Frio Island rocky shore (Arraial do Cabo-RJ, Brazil) for one year. Spectral, temporal and seasonal analyzes were carried out, in addition to the evaluation of the influence of abiotic factors in 1/3 octave bands. Spectral analysis showed that the highest SPL values occurred in 4, 5 and 6.3 kHz bands, which correspond to the frequency peaks recorded for snapping shrimp, sea urchins and bivalves based on the scientific literature. All 1/3 octave bands analyzed, presented a circadian pattern, with higher SPL values in twilight, followed by the night period and with lower values in the daytime period. This is a characteristic pattern of invertebrates, which have a crepuscular peak of activity and remain active at night to feed. The months of February and March 2018, and December and January 2019 (summer and early autumn) showed the highest SPL values. Summer and winter were statistically different, except for the 2 kHz band. Summer and winter were statistically different, except for the 2 kHz band. The abiotic factors with the highest correlations with the 1/3 octave bands were solar radiation and water temperature, factors directly related to the circadian pattern and metabolism of benthic invertebrates. The sounds of the most representative organisms in terms of acoustic energy were characterized using an automatic classification method based on unsupervised machine learning techniques. Were identified three classes of snaps, which presented similar acoustic signatures, with most of the acoustic energy concentrated up to 8 kHz and frequency peaks varying between 3.7 and 4.55 kHz. Acoustic signatures patterns and the SPL of snaps are compatible with those registered by other authors for snapping shrimp. However, other benthic invertebrates, such as barnacles, bivalves and sea urchins, have high densities in the study area, and it is not possible to discard the hypothesis that the acoustic signatures represent snaps produced by a group of organisms.