Heavy Metal Contamination in Mombasa’s Coastal Waters (2015–2024): A Review of Trends, Sources, and Ecological Risks

Heavy metal pollution poses a significant threat to coastal ecosystems, particularly in rapidly urbanizing and industrializing regions. This review synthesizes studies conducted between 2015 and 2024 on heavy metal contamination in the coastal waters and sediments of Mombasa, Kenya, a major economic hub along the Western Indian Ocean. The review focuses on key metals, including lead (Pb), cadmium (Cd), mercury (Hg), copper (Cu), and zinc (Zn), examining their concentrations, spatial distribution, sources, and ecological risks. Elevated concentrations were reported in areas influenced by port operations, industrial discharge, sewage effluents, and urban runoff, with Tudor Creek, Port Reitz, Makupa Creek, and Kilindini Harbour identified as major pollution hotspots. Sediments were found to function as both sinks and secondary sources of contaminants, increasing long-term ecological risks. Evidence of bioaccumulation in marine organisms, including mollusks and fish, raises concerns about food safety, biodiversity conservation, and ecosystem integrity. Despite several localized assessments, long-term monitoring and standardized ecological risk evaluations remain limited. This review highlights critical knowledge gaps and recommends strengthened pollution control measures, improved environmental regulation enforcement, and enhanced stakeholder participation to support sustainable coastal ecosystem management and the blue economy in Mombasa