Valutazione dell'impatto dei subacquei sulle comunità bentoniche

The increasing popularity of recreational scuba diving in coastal areas has contributed to the global expansion of marine tourism. Although diving is generally considered a low-impact activity, several studies show that direct contact between divers and the seabed can negatively affect benthic ecosystems. In the Mediterranean Sea, a basin characterised by high biodiversity and intense anthropogenic pressure, these impacts may be particularly relevant, especially within coralligenous habitats dominated by slow-growing sessile organisms. The aim of this thesis was to quantitatively evaluate the effects of recreational scuba diving on Mediterranean benthic communities through a systematic review and meta-analysis of the scientific literature. A bibliographic search in the Web of Science database identified 222 studies, which were screened through a multi-step selection process. Among these, 12 studies met the criteria for quantitative analysis. Effect sizes were calculated for each impact–control comparison using the log response ratio (lnR) and analysed with a multilevel random-effects meta-analytic model. The analysis showed a strong geographical concentration of studies in the Western Mediterranean and a focus on coralligenous habitats, with habitat-forming taxa such as bryozoans, gorgonians, ascidians and corals being the most frequently investigated groups. Overall, results indicate that recreational diving can reduce density, alter colony size structure and increase partial mortality in sensitive organisms. Most impacts were linked to involuntary contacts between divers, equipment and the substrate, particularly at sites with high diving pressure. These findings highlight that even activities considered low impact may produce measurable ecological changes in Mediterranean benthic ecosystems and emphasise the importance of appropriate management strategies to ensure the long-term sustainability of diving tourism.