Comparison of the marine soundscape before and during the COVID-19 pandemic in dolphin habitat in Sarasota Bay, FL

Abstract

During the COVID-19 pandemic, decreases in large vessel activity and low-frequency noise have been reported globally. Sarasota Bay is home to a large and increasing number of recreational vessels, as well as a long-term resident community of bottlenose dolphins, Tursiops truncatus. We analyzed data from two hydrophones to compare the soundscape during the COVID-19 pandemic to previous years (March–May 2020 and 2018/2019). Hourly metrics were calculated: vessel passes, 95th percentile noise levels (125 and 16 kHz Third Octave Bands (TOBs) and two broadbands: 88–1122 Hz, 1781–17959 Hz), and dolphin whistle detection, to understand changes in vessel activity and the effect on wildlife. Vessel activity increased during COVID-19 restrictions by almost 80% at one site and remained the same at the other. Changes in noise levels varied between sites. Only the 125 Hz TOB and 88–1122 Hz band increased with vessel activity at both sites, suggesting this may be an appropriate measure of noise from small vessels in very shallow (<10 m) habitats. Dolphin whistle detection decreased during COVID-19 restrictions at one site but remained the same at the site that experienced increased vessel activity. Our results suggest that pandemic effects on wildlife should not be considered to be homogeneous globally.