| Summary: | The increasing heavy metal accumulation in edible fauna is harmful to human health. Among mangrove crabs, Cardisoma armatum is the most consumed despite their doubtful hygienic states. This study aims at assessing heavy metal accumulation in associated sediments and C. armatum crabs related to season and site differences and their implications on human health. Mean concentrations of metals in sediments were ordered: Aluminium (Al=3191.84 mg/kg)> Zinc (Zn=139.90 mg/kg)> Copper (Cu=48.50 mg/kg)> Lead (Pb=36.17 mg/kg)> Iron (Fe=23.08 mg/kg)> Cadmium (Cd=0.35 mg/kg). Occurrence and levels of metals showed high differences between sites and enrichment in the sediments are mainly related to human activities. Copper was not found at Mpalla site and in both seasons. Dried sediments were higher in concentration than wet sediments for all metals because of the regular soil leaching which occurred in the wet periods. For crab tissues, mean concentrations of metals were ranked: Fe (127.43 mg/kg) > Zn (67.07 mg/kg) > Al (13.69 mg/kg) > Cu (3.09 mg/kg) > Cd (0.19 mg/kg) > Pb (0.11 mg/kg). Likewise, patterns of metal levels were highly different in both sites and all metals were prominent during the dry season resulting probably in biological cycle changes in C. armatum. Levels of essential metals (Cu, Zn and Fe) were found higher possibly to maintain biological functions. Concentrations of metals were largely exceeded threshold values (except for Cu and Pb) which imply unpleasant human health risks could occur. Bioconcentration factor (BCF) value of Fe (5.52) was largely above 1. It seems that Fe appears to be a good tool for monitoring Fe pollution in the area. The elevated metal pollution index (MPI=4.37) indicated high bioaccumulation affinities with all metals. This therefore implies that consuming C. armatum may pose non-negligible health implications to humans.
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