Distribution and Source of Metals in the Horizontal and Vertical Profiles, and Their Ecological Risk in the Red Sea Coast, Western Saudi Arabia

Metal pollution is a critical environmental challenge that endangers marine life and ecosystems worldwide. This study evaluated the metal distribution in horizontal and vertical profiles, as well as their sources in the Red Sea coast, Western Saudi Arabia, using the contamination factor (CF), ecological risk (Er) index, potential ecological risk index (RI), and multivariate statistical analysis (MSA). Seawater samples were collected from three zones (north (N = 90), middle (N = 60), and south (N = 90); total = 240) and were analyzed for 18 metals (Ag, As, Ba, Cr, Cd, Cs, Cu, Co, Ga, Mn, Ni, Pb, Rb, Se, Tl, U, V, and Zn), EC and pH. The results reveal that metals enrichments differ across zones, namely north (Cr, Zn, Ag, and U), middle (V, Mn, Co, Ga, Ba, and Pb), and south (EC, Cu, Se, and Rb) zones. In the north zone, most metals exhibited higher concentrations in the bottom layer. Horizontal distribution reveals metals’ enrichment in 30 m (Ni, Cu, and Pb) and 60 m (Cr, Zn, and Rb). In the middle zone, higher metal concentrations were observed in the bottom (Cr, Zn, Ni, Cu, Rb, and Ag) and top layers (Mn and Pb). Conversely, most metals in the south zone accumulated in the top layer (Ni, Zn, Rb, and Ba). Seawater in nearshore areas is more polluted than that 30 and 60 m offshore. The CF indicates very high to moderate contaminations in the north and middle zones. In the south zone, Se and Cu show very high contamination, while V exhibits considerable contamination. Er implies a low ecological risk for most metals, except for Cu (in the north and south zones) and Mn (in the middle zones), meaning that it poses a predictably low risk with isolated hotspots of high ecological risk. The RI results suggested that approximately 90% of the samples fell within the low ecological risk category. MSA suggested that the observed metal concentrations were potentially associated with both natural and anthropogenic sources in the study site.