North Sea soundscapes from a fish perspective: Directional patterns in particle motion and masking potential from anthropogenic noise

Abstract

The aquatic world of animals is an acoustic world as sound is the most prominent sensory capacity to extract information about the environment for many aquatic species. Fish can hear particle motion, and a swim bladder potentially adds the additional capacity to sense sound pressure. Combining these capacities allows them to sense direction, distance, spectral content, and detailed temporal patterns. Both sound pressure and particle motion were recorded in a shallow part of the North Sea before and during exposure to a full-scale airgun array from an experimental seismic survey. Distinct amplitude fluctuations and directional patterns in the ambient noise were found to be fluctuating in phase with the tidal cycles and coming from distinct directions. It was speculated that the patterns may be determined by distant sources associated with large rivers and nearby beaches. Sounds of the experimental seismic survey were above the ambient conditions for particle acceleration up to 10 km from the source, at least as detectable for the measurement device, and up to 31 km for the sound pressure. These results and discussion provide a fresh perspective on the auditory world of fishes and a shift in the understanding about potential ranges over which they may have access to biologically relevant cues and be masked by anthropogenic noise.

How the noises could affect marine food webs? A lack of zooplankton’s studies.

“…Because zooplankton species have not developed a hearing system, they use only external mechanoreceptors. Consequently, the main characteristic of the sound that is important is not the pressure level (i.e., the classical measure in dB), but the particle motion (i.e., the tidal velocity in m/s) (Nedelec et al, 2016;Rogers et al, 2021). So, it is now recognized that measuring the particle motion is mandatory to understand zooplankton reactions to noises (André et al, 2016;Popper and Hawkins, 2018).…”

A decade of underwater noise research in support of the European Marine Strategy Framework Directive

“…This may be possible via extrapolation from existing sound-pressure assessments, but this has yet to be demonstrated. In any case, such monitoring presents significant challenges due the importance of directionality in the detection of particle motion (Rogers et al, 2021). A greater emphasis on fish species within the MSFD may also necessitate further research on the soundscapes of estuarine and freshwater ecosystems, which are important habitats for spawning, foraging, and migration.…”

Determining the directionality of anthropogenic noise using an underwater acoustic vector sensor: a case study in a Norwegian fjord

“…An AVS can also detect the directionality of weak sound sources. An AVS deployed along the coast of Belgium revealed the ambient noise (20-40 Hz) coming from the direction of the Thames River [11].…”