Quantifying vessel noise and acoustic habitat loss in marine soundscapes

Abstract

Quantifying underwater vessel noise in marine ecosystems is challenging, due to difficulties in accounting for small, not publicly tracked boats, creating a knowledge gap in marine management. We present a computationally efficient framework that detects all vessel noise in hydrophone recordings and quantifies associated excess noise levels as well as acoustic habitat loss, offering a cost-effective and replicable tool for assessing vessel noise effects on marine soundscapes. Applied to one year of acoustic data from five sites along the coast of British Columbia (BC), Canada, the detector achieved 96.4 % accuracy and was robust against varying levels of vessel traffic and weather conditions. Across sites, vessel noise impacts increased with proximity to urban centers. Following this trend, average annual vessel noise presence ranged between 24 % and 85 %, increasing the 500 Hz decidecade band by 1.0 dB to 6.4 dB across sites. The average year-round acoustic habitat loss for killer whales, expressed as the reduction of listening space in a 0.5–15 kHz communication band, ranged from 6.6 % to 46.9 %. Vessel noise impacts were generally higher during daylight hours and in the summer months. The results are the first comprehensive, empirical assessment of vessel presence and associated noise impacts for a regional ecosystem in BC.