Assessment of heavy metal contamination in sediments, seawater, and marine organisms along the Benghazi coast, northeastern Libya (Mediterranean Sea).

The heavy metal pollution in the coastal environments poses a severe hazard to the marine ecosystems and public health, mainly in the urbanized areas with inadequate wastewater management. This study aimed to assess the spatial distribution, levels, and ecological risks of five heavy metals (Cd, Cu, Fe, Pb, and Zn) in seawater, sediments, and certain marine organisms along the Benghazi coast, northeastern Libya. A total of 45 samples, including sediments, seawater, fish (Epinephelus marginatus and Sarpa salpa), green algae (Ulva lactuca), and mussels (Mytilus galloprovincialis), were collected from five sites in the winter of 2023. The heavy metal concentrations were determined using flame atomic absorption spectrophotometry, and pollution was evaluated using multiple indices (CF, I_geo, EF, SPI, BAF, and RI). The results revealed that Fe showed the highest mean concentration in the sediments (391.6 ± 262.9 mg/kg) and the seawater (3809.8 ± 677.3 µg/L), while Cd levels in seawater (mean = 54.87 ± 15.15 µg/L) considerably exceeded permissible limits (p < 0.001). The statistical analysis (ANOVA) showed important spatial differences in Zn and Cd concentrations in seawater (p < 0.001) and Pb in sediments (p < 0.001). The bioaccumulation was highest for Zn and Pb in mussels (BAF > 3) and in fish livers (Zn BAF up to 8.68). The enrichment factor (EF) and potential ecological risk index (RI) indicate moderate to considerable Cd contamination at specific sites. These findings highlight an urgent need for improved environmental monitoring and wastewater treatment infrastructure along the Benghazi coastline. The use of bioindicators such as M. galloprovincialis is recommended for future biomonitoring programs in the region.