The Effect of COVID-19 Shutdowns on Hawaiian Coral Reef Soundscapes

Global shutdowns during the COVID-19 pandemic offer a unique opportunity to study the impact of manmade noise on marine life. Here we investigate whether reductions in shipping traffic led to changes in biological soundscapes in a coral reef off the coast of Hapuna Beach, Hawaii. Continuously-sampled acoustic measurements are compared between March and May of 2019, 2020, and 2021, where the measurements in 2020 correspond with an emergency rule limiting all commercial and passenger vessels to no more than two unrelated occupants. We investigate changes in the sound intensity of vocalizing fish choruses and parrotfish feeding sounds which are prominent at sunset, as well as seasonal humpback whale vocalizations which dominate the soundscape between January and March. A convolutional neural network detector is also used to quantify the prevalence of humpback vocalizations and compare between the years studied. An increase in the intensity of fish call choruses of approximately 1 dB was observed during the period of suppressed boating activity in 2020. No significant difference in parrotfish feeding sounds or humpback whale vocalizations were observed in 2020 compared to the other years. Humpback choruses started and ended later in the season in 2019, which may be attributed to lower winter temperatures and warmer spring temperatures compared to the other years.