Heavy metals accumulation in environmental matrices and their influence on potentially harmful dinoflagellates development in the Gulf of Gabes (Tunisia)

Distribution and abundance of potentially harmful dinoflagellates were assessed in three matrices in relation with heavy metals concentrations in the Gulf of Gabes. Tidal Flat Waters (TFW), sediments and macroalgae (Ulva rigida) were collected from five sites along the tidal coast, and nine potentially harmful dinoflagellates were identified. Igeo accumulation index and Enrichment Factor revealed extremely severe enrichment by Cu and Cd at sites situated near to the phosphate factory. Ulva displayed high bioconcentration and bioaccumulation values particularly for Fe and Cr. The relationships between potentially harmful dinoflagellates and heavy metals depend on substrata and species. Amphidinium carterae showed a certain degree of affinity for Cu (p < 0.05; r = 0.97) in sediments, but not on U. rigida. Despite the extremely high enrichment of some heavy metals, potentially harmful dinoflagellates were also consistently found in the most polluted area, revealing a high adaptation to these major contamination levels.