Assessment of three marine soundscapes amidst small-boat-generated noise in the Gulf of Tribugá, Colombia

Sound is crucial in marine ecosystems, serving as the primary conduit for information transfer for many organisms. The effects of anthropogenic noise on marine organisms vary from behavioral changes to physical harm. The Gulf of Tribugá has diverse ecosystems and species of high ecological and economic value. This research aimed to characterize three sites in the Gulf of Tribugá using acoustic indices, distinguishing between conditions with and without boat noise across different years. Since 2018, 1518 recordings from passive acoustic monitoring at three sites in the Gulf have been analyzed, categorized as having boat noise present or not. A descriptive analysis of acoustic indices was conducted (1) across space and time, (2) between times with and without boat noise, and (3) between two frequency ranges. Passive acoustic monitoring at three Colombian sites (2018 -2022) used EAR and SNAP recorders deployed at ~16 -25 m, recording 10 min every 20 min at 15,625 or 48,000 Hz. Eight 10_min files daily were manually annotated for sound sources and boat presence. Acoustic indices (ACI, ADI, AEI) and SPL were computed in R and MANTA. Statistical comparisons assessed temporal/spatial differences with/without boat noise. All sites had significantly different Acoustic Complexity Index values based on boat noise presence, which were dependent on the frequency range examined. The absolute values of the acoustic indices varied over time, as significant differences were found across an annual time span for the Acoustic Evenness Index and Acoustic Diversity Index when comparing recordings with and without boat noise. Furthermore, a difference in sound pressure levels of 10 dB re 1 µPa over the full bandwidth was found before compared to after COVID-19. These results could serve as a guide for other studies and continued monitoring in the area, but they are not comparable with other sites, as changes may depend on different factors, or the indices may not be suitable for other cases.