Animal-borne sensors reveal high human impact on soundscapes near a critical sea turtle nesting beach

Abstract

Anthropogenic noise (anthrophony) is pervasive in natural soundscapes and has become an important aspect of conservation. While moored sound recorders have aided marine soundscape research, they do not capture the dynamic experiences of animals as they move through underwater soundscapes.

This study used animal-borne acoustic recording tags to capture the marine soundscape near leatherback turtle nesting grounds in Gabon, Central Africa. Propeller noise was heard in 75 ± 14.7 % (mean ± SD) of recordings and peaks in sound intensity up to 146 dB re 1 μPa were detected in shipping noise frequency bands. Loud noise events (> 141 dB), detected in 10 % of recordings, were distributed throughout the turtle interesting habitat. An anthrophony map was created, identifying peaks in noise corresponding with the Komo estuary —gateway to the nation's main international port and near a key nesting area. The pervasive, loud anthrophony recorded in the study may have negative impacts on nesting leatherback turtles and other species of conservation concern found in the area, and warrants further monitoring and management action.

This study offers one of the first spatio-temporal analyses of sound experienced by an endangered marine vertebrate through animal borne, multi-individual acoustic monitoring. It highlights the utility of animal borne acoustic tags in delineating underwater soundscapes and their applicability to studying concurrent biological phenomena and threats, while supporting the need for similar monitoring efforts in other critical sea turtle habitats.