Underwater Soundscapes
Soundscape ecology is the study of habitats through understanding the unique collection of sounds heard within them. A soundscape is the union of ambient biological, geophysical, and anthropogenic noise associated with individual habitats. The biological component of a soundscape consists of noises produced by living organisms and is referred to as biophony. Living organisms produce sounds for a variety of reasons including navigation, mating, foraging, spawning, social encounters, and predation. Sound is an essential sensory tool for marine organisms in particular because it travels over long distances whereas other senses, like vision, are limited. The sounds that animals produce can be uniquely identifiable to the species or even individual level.
The main geophysical sounds that contribute to soundscapes are earthquakes, wind, and rain. These are referred to as geophony. Anthropophony is the term for the anthropogenic, or human-made, contributions to soundscapes. Humans produce a variety of noises that can be heard in marine environments including boat engines, seismic blasts, military sonar, and the construction of oceanic structures like wind turbines. Anthropogenic noise has increased in the marine soundscapes over the last century as a result of escalating human presence in, and use of, marine environments.
Data on soundscapes is collected through passive acoustic monitoring, which is a way of listening to marine environments using underwater microphones. Passive acoustic monitoring is an increasingly popular method to survey marine environments as it is cheaper, noninvasive, and more reliable than alternative monitoring methods (such as visual surveys) under the challenging survey conditions associated with marine environments (variable weather, high pressure, or darkness). Recording soundscapes over long periods using passive acoustic monitoring devices and understanding their changes and variation can be used as a tool to study which animals are present in a location, when they are there and what they are doing when they are there. This information can be used to evaluate ecosystem health, monitor marine protected areas and document changes that are happening as a result of human impacts, climate change and storms. Soundscape analysis has been used for species detection, environmental monitoring, biodiversity estimations, and identification of acoustic hotspots which are areas with particularly high concentrations of noise.
BMMRO has deployed multiple passive acoustic recorders in the Marsh Harbour area of Abaco Island. Three of their recorders are deployed near, or in, ferry routes. These data, in combination with BMMRO’s visual surveys, can provide an understanding of how dolphins may navigate areas with heavy boat traffic and if boat traffic presents challenges to dolphins. Additionally, BMMRO was able to collect acoustic data through passive acoustic monitoring before and after Hurricane Dorian. Analysis of this data has provided insight into how dolphins may have responded to the storm as well as how the animals are changing their behavior as more people return to Abaco as the island continues to recover causing increased boat traffic. Analyzing soundscapes around Abaco has aided BMMRO in its research goals and helped to understand how local dolphins navigate their environment. For my own master’s thesis through the University of St Andrews, I will be using BMMRO’s soundscape data to evaluate what species are present on reefs around Abaco reefs and when. This is done by identifying different animal vocalizations and can provide information on the health of reefs or areas that may be home to higher amounts of marine life and are therefore important to conserve.
Written by India Haber (University of St Andrews)