Two Decades of Coastal Contamination: A Review of Spatiotemporal Assessment of Cadmium and Lead Dynamics in the Bioindicator Mytilus galloprovincialis Along the Algerian Coastline and Compliance with Food Safety Standards

Over the past 24 years, research on trace metal contamination along the Algerian Mediterranean coast has grown substantially, yet its findings remain fragmented. This review compiles and analyses data from 111 samples reported in 24 independent studies on cadmium (Cd) and lead (Pb) concentrations in the sentinel bivalve Mytilus galloprovincialis. The compiled dataset includes 23 samples from 5 harbour stations and 88 samples from 36 open-coast stations, spanning the three major coastal regions of Algeria. To account for the heterogeneity of the dataset, appropriate non-parametric and multivariate statistical analyses were performed using R version 4.3.2. Results revealed that Western Algeria was the most heavily contaminated region, with significant spatial variability in metal concentrations and a pronounced westward contamination gradient (PERMANOVA, Region R2 = 0.27, p < 0.001). These findings identify priority areas for environmental surveillance. Regarding regulatory compliance, Cd concentrations remained below the Codex Alimentarius maximum level for bivalve molluscs at all open sites, whereas Pb exceeded it at 30.3% of stations (10/33), indicating a greater concern with respect to food-safety limits. This synthesis provides the first coherent national assessment of Cd and Pb contamination along the Algerian Mediterranean coast and establishes a scientific foundation for targeted, harmonized biomonitoring strategies.