Drowned Dialogues: A Preliminary Study on the Behavioral and Auditory Response of Delphinus delphis to Marine Noise Pollution in the Bay of Gibraltar

Abstract

The Bay of Gibraltar is an ecologically and strategically significant marine region, characterized by complex bathymetry that promotes nutrient rich waters and supports immense biodiversity. Its location between two major shipping-dependent countries, the United Kingdom and Spain, and its proximity to the Strait of Gibraltar (linking the Atlantic ocean to the Mediterranean sea) results in exponentially high marine vessel traffic. Increased shipping density contributes substantially to underwater noise pollution, altering the marine soundscape. Chronic exposure to such anthropogenic noise has been proven to have adverse effects on numerous marine organisms in the Bay of Gibraltar. This study aims to investigate these effects, specifically on the common short-beaked dolphin (Delphinus delphis), an especially prominent species in this study site. In particular, relationships between vessel density and dolphin behavior, vessel density and vocalization abundance, ambient noise and vocalization frequencies, as well as vessel and dolphin positioning are examined by means of observational studies, auditory recordings, comparative and linear analyses, and satellite imagery. The findings of this study suggests trends towards more mobile behaviors, masking of auditory signals by ambient noise, and vessel avoidance by the target species. These results aim to enhance our understanding of the impacts of anthropogenic noise pollution on marine soundscapes and dolphin behavior, informing future conservation, management efforts, and studies exploring similar themes interlinking marine and human ecology.