Underwater soundscape pattern during high season of nautical tourism in Cabo Frio Island, Brazil

Abstract

The underwater soundscape may change in time and/or space and is comprised by abiotic, biotic, and anthropogenic sounds. Several ecological relationships are associated with soundscape patterns. This study aims to characterize the underwater soundscape of the Arraial do Cabo region, Brazil, evaluating biological and anthropogenic acoustic patterns. Signals were recorded from December 2016 to January 2017. The duty cycle was established as a one-minute recording every five minutes, totaling 20% of a 24-hour period. Three frequency ranges were selected (0.1–22 kHz, 0.1–2 kHz, and 2–22 kHz) and the following acoustic measurements were taken: average power, average entropy, and peak frequency. Based on the association between the acoustic measurements, the presence of touristic boats was mainly recorded at frequencies below the 200 Hz range during the daytime. There was a pattern in the acoustic measurements in frequency ranges A and B at 9h. From this period on, there was a decrease in peak frequency and average entropy values and an increase in the average power. The association between the acoustic measurements was shown to be a potential tool in detecting vessels presence in the studied region; this constant disturbance impaired the establishment of the natural pattern of the underwater soundscape.