Monitoring water contamination through shellfish: A systematic review of biomarkers, species selection, and host response.

Shellfish are ubiquitous inhabitants of water environments and an important food source. Their presence in habitats affected by human activities and bioaccumulation potential support their use as indicators of contamination. Using these organisms as bioindicators may provide a simple, cost-effective alternative for monitoring contamination risk without requiring complex sample preparation and analytical procedures. However, there is no consensus on biomarkers, species selection, or standard methodologies. This systematic review explores the significance of shellfish as bioindicators, the methodologies employed, and the interactions between contaminants and host response. Research strategy and selection criteria followed PRISMA and SPICE guidelines. Peer-reviewed papers were obtained from Scopus, Pubmed and Google Scholar using the keywords: shellfish, bioindicator, environmental, contaminant, and host response. Out of 3050 results, 20 studies were selected after a rigorous, unbiased process. These studies spanned 14 countries, assessing 26 shellfish species, 24 contaminants, and 35 effects. A wide range of biomarkers was identified, reflecting changes in water condition due to contaminants or adverse environmental parameters. Results indicate that shellfish are highly sensitive to minor environmental changes, making them reliable bioindicators of water quality and potential risks of consumption from contaminated sites. This study highlights the need for standardized protocols to enable consistent shellfish-based monitoring of water conditions worldwide.