The Role of Sea Surface Circulation and Weather Dynamics in the PAH Contamination in Coastal Mussels: A Case Study in the Southern Tyrrhenian Sea

Laura Fortunato^1*Mauro Esposito²Vincenzo Capozzi¹Fabio Conversano³Luigi Gifuni¹Paola De Ruggiero¹Giuseppe Aulicino¹Diana Di Luccio¹Enrico Zambianchi⁴Giorgio Budillon¹Yuri Cotroneo¹

• ¹University of Naples Parthenope, Naples, Italy
• ²Experimental Zooprophylactic Institute of Southern Italy (IZSM), Portici, Italy
• ³Anton Dohrn Zoological Station Naples, Naples, Campania, Italy
• ⁴Sapienza University of Rome, Rome, Lazio, Italy

The Gulf of Pozzuoli, a marginal sub-basin of the Tyrrhenian Sea, has a longstanding tradition of bivalve mollusc farming. However, its historical importance in aquaculture contrasts considerably with significant anthropogenic pressures—most notably from the decommissioned industrial site at Bagnoli. Monitoring data show that contamination of mussels by polycyclic aromatic hydrocarbons (PAHs) follows a seasonal trend, with peaks typically occurring in late autumn and early winter. This study investigates the oceanographic and meteorological dynamics driving PAH contamination, focusing on 2016, when one farming site in the Gulf exhibited elevated PAH concentrations. A combination of in situ data, satellite observations, numerical model outputs, and Lagrangian simulations was employed to analyse sea surface circulation, wind patterns, wave dynamics, and particle transport pathways. Results indicate that contamination events were consistently preceded, by about one week, by the development of a northwestward surface current, likely facilitating pollutant transport from Bagnoli toward the farming area. Additionally, southerly waves exceeding 1.2 meters in height and with periods longer than 8 seconds were recorded in the days before contamination peaks, suggesting a role for wave-induced resuspension of PAHs from sediments. These hydrodynamic conditions coincided with prevailing southwesterly winds. These findings support the hypothesis that specific meteorological and oceanographic conditions facilitate PAH transport from the Bagnoli site to the farming area, posing risks to bivalve farming and public health. Starting from previous data, this work develops and provides robust conclusions on the problem of PAH pollution in mussels farmed in the Gulf of Pozzuoli—a local issue with relevance to similar contexts—offering a rationale for improving monitoring and management strategies to mitigate contamination risks in vulnerable coastal environments.