Mercury (Hg) is a globally concerning contaminant due to its persistence, toxicity, and biomagnification potential. Polychaetes, as sediment-dwelling invertebrates and key trophic intermediaries in benthic food webs, have drawn increasing attention for their role in mercury transfer and biomonitoring. This systematic review synthesizes data from 49 studies conducted across major ocean regions worldwide, spanning 27 countries and Antarctica and covering 21 polychaete families. This study evaluates methodological practices and ecological factors influencing Hg and methylmercury (MeHg) accumulation. Nearly half of the reported total Hg (THg) concentrations exceeded the corresponding EQS-Biota threshold (110 μg/kg, dw). Feeding guilds were found to influence bioaccumulation patterns, with families classified as surface deposit feeders / suspension feeders and subsurface deposit feeders generally showing higher bioaccumulation factors (BAF) than carnivorous / omnivorous groups. Methodological inconsistencies, such as variations in sample depuration, tissue selection, and data reporting formats, also found to limit cross-study interpretation. This review highlights the need for harmonized analytical protocols, expanded biogeographic and taxonomic representation, and feed guilds-based approaches to better utilize polychaetes in mercury monitoring. These insights offer scientific foundations for more robust ecological risk assessments and the development of effective marine pollution management strategies.
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