The oceans, essential for climate regulation, biodiversity, and human resources, are under increasing pressure from anthropogenic pollution. This pollution comes primarily from urban, industrial, and agricultural activities, in addition to atmospheric and marine inputs such as oil spills and plastic waste. Pollutants include heavy metals, hydrocarbons, excess nutrients, and radionuclides, which compromise water quality, disrupt food chains, and threaten the food security of coastal populations. Transport pathways runoff, atmospheric deposition, ocean circulation, and sedimentation favor their accumulation in particularly vulnerable areas such as the Mediterranean. Radionuclides occupy a unique position: as persistent contaminants, they are also powerful tracers for studying pollution dynamics and dating sedimentary deposits. Their fate depends on intrinsic properties (half-life, chemical affinity, decay mode) and environmental conditions (pH, salinity, suspended solids). Certain isotopes, such as 137Cs or 210Pb, can identify the origin of sediments, while tritium and carbon-14 are integrated into major biogeochemical cycles. In addition, bioaccumulating organisms mussels, fish, seagrass beds play a role as biological sentinels, revealing contamination and its effects on ecosystems. The integration of radionuclides and bioindicators, combined with modern biomonitoring techniques, strengthens our understanding of transfer processes and provides strategic tools for managing and preventing environmental risks. This study places these approaches within the framework of biomonitoring, emphasizing the methodological integration to characterize ecological quality and guide environmental management.