Heavy metal contamination in seawater, sediments, algae, and fish from Susah and Tobruk, Mediterranean Sea

Heavy metal contamination in marine environments poses serious threats to ecological health and human safety. This study examines the concentrations of zinc (Zn), copper (Cu), iron (Fe), cadmium (Cd), and lead (Pb) in sediments, seawater, and marine organisms (Ulva lactuca and Epinephelus marginatus) along the coastlines of Susah and Tobruk, Libya. The sampling involved 66 samples from 10 sites conducted in winter 2023. The contamination of cadmium clearly showed in all studied samples in Susah and Tobruk, whereas lead surpassed permissible in seawaters and livers, gills, and tissues of E. marginatus. The iron was high in the seawaters of Susah and Tobruk, particularly near Susah port and in Tobruk Gulf, reflecting the influence of industrial and anthropogenic activities. The results revealed that cadmium levels in the sediments indicated considerable contamination in Susah (CF = 5.897) and moderate contamination in Tobruk (CF = 1.12). The assessment employed several pollution indices, including the Geo-accumulation Index (Igeo), which indicated that all studied metals were uncontaminated in Tobruk, while Cd showed moderate contamination in Susah (Igeo = 1.975). The Nemerow Pollution Index (NI) categorized Susah as seriously polluted (NI = 6.01) and Tobruk as lightly polluted (NI = 1.195). Additionally, bioaccumulation factors for heavy metals in both U. lactuca and E. marginatus indicated acute contamination, particularly lead in fish tissues. These findings underscore the urgent need for effective environmental management strategies to address heavy metal pollution and protect the health of marine ecosystems and local communities reliant on these coastal resources. PRACTITIONER POINTS: Comprehensive pollution profiling (CF, Igeo, NI, and EF) in the study areas. GIS spatial mapping (heavy metal distribution and pollution sources identification) Bioaccumulation insights (bioaccumulation in fish and algae, showing ecological risk). Data for future monitoring (data for a significant gap in environmental monitoring) Public health awareness (urgent need for management and treatment options).