**Abstract**

Coastal ecosystems are exposed to pollution by various contaminants due to several anthropogenic activities. Numerous pollutants, such as pesticides, drugs, metals, Polycyclic Aromatic Hydrocarbons (PAHs), Brominated flame retardants (BFRs), and Microplastics (MPs), transported in the water column tend to persist in the sediments. Among the Tunisian coastal areas, the Bizerte and Ghar El Melh lagoons are exposed to several pollutants resulting from different activities, such as agriculture, urbanization, and industrialization. Consequently, sediments are intensely dirtied by a wide range of pollutants. Due to their relatively short life cycles and high turnover rates, free-living nematodes reacted quickly to environmental changes. This most dominant meiobenthic taxon, has been mainly exploited as indicator of disturbance because of its ubiquity, high abundance, and taxonomic diversity. In this current chapter, we cited the different environmental pollutants effects and show the importance of nematodes as bio-indicator species in environmental monitoring.

**Keywords:** Tunisian Lagoon ecosystems, free-living nematodes, emerging contaminants (ECs), risk assessment, experimental approach
