Marine acoustic monitoring is a non-invasive tool for studying marine biodiversity and ecosystem dynamics through the analysis of the underwater soundscape. This method enables the detection of cryptic species and behaviours not easily observed through traditional visual surveys. It also helps to assess anthropogenic disturbance, as noise pollution. Posidonia oceanica meadows, protected under the Habitat Directive 92/43/CEE, are vulnerable to such pressures, since noise can alter fish sound production and behaviour.

This study aims to investigate the acoustic community of the Posidonia oceanica meadows in the Capo Gallo - Isola delle Femmine Marine Protected Area (MPA), by using acoustic indices, and analysing the differences among sites and between high and low touristic seasons. Additionally, the effect of boat noise on species acoustic occurrence was assessed.
Six sites within the MPA were selected. Autonomous underwater recorders (RASP-URec384k-Nauta RCS) were deployed in mid-June and mid-August, recording 15 minutes every hour (6 hours/day).

Recordings were analysed using Raven Pro 1.6 (FFT =8192, Hamming window, 50% overlap). All recordings were manually screened to detect fish sounds and boat noise. Acoustic abundance and richness were calculated to assess the habitat acoustic community. A total of 502 hours of recordings were collected, with three days per site analysed. Preliminary results revealed 9,247 fish sound occurrences, mainly at night. The dominant species were Scorpaena spp. (79%), Sciaena umbra (21%) and Ophidion rochei (0.01%). Punta Barcarello was the site with the greatest acoustic richness, and the highest acoustic abundance was observed during the high season. Boat noise was present in 57% of recordings, and its increased duration at night corresponded with a decreased fish sound occurrence.

These results support the integration of passive acoustic monitoring into the management of MPAs, particularly for understanding ecological patterns and the effects of anthropogenic noise on vulnerable seagrass ecosystems.