Early Biodiversity Responses to Underwater Marble Sculptures Deployed as Artificial Reefs: First Scientific Assessment of a Conservation Initiative in the Northern Tyrrhenian Sea

Marine coastal ecosystems are increasingly affected by habitat degradation and loss of structural complexity, with negative consequences for biodiversity, particularly in the Mediterranean Sea. In the Talamone coastal area (Northern Tyrrhenian Sea), additional local pressures include episodes of illegal bottom trawling; however, anti-trawling mitigation actions in the area have been implemented through the deployment of concrete blocks along the coast, whereas underwater artistic installations were conceived primarily to enhance habitat heterogeneity, support conservation outreach and promote community engagement. This study provides the first systematic scientific assessment of an art-based marine conservation initiative promoted by the association “Casa dei Pesci”, based on the deployment of underwater marble sculptures as nature-based artificial reef structures. Five marble statues were deployed in September 2024 in the Baia del Cannone and monitored over one year using standardized underwater visual census techniques to evaluate early biodiversity and community responses associated with the newly introduced hard substrates, considering benthic cover and diversity, fish abundance and assemblage composition, and biological colonization directly on the sculptures. The results show clear early colonization patterns, with the sculptures supporting diverse fish assemblages and increasing local habitat heterogeneity in a predominantly soft-bottom setting. This study provides baseline ecological data for future long-term monitoring and supports the evaluation of underwater marble artworks as complementary nature-based interventions. However, artificial reefs may also generate ecological trade-offs, and longer-term monitoring is required to assess both potential biodiversity benefits and unintended effects in Mediterranean coastal ecosystems.