Cadmium bioaccumulation in two resident limpet species, Scutellastra granularis and Siphonaria capensis, along the South African coastline

We investigated cadmium (Cd) bioaccumulation in two limpet species, Scutellastra granularis and Siphonaria capensis, along the South African coastline from three sites: Namaqua National Park, West Coast National Park and Garden Route National Park. Significant spatial variations in Cd accumulation were observed, with the highest concentrations found in limpets from Namaqua National Park (S. granularis: 4.17±1.99 µg/g; S. capensis: 2.92±1.45 µg/g) despite having the lowest water Cd levels (0.13±0.07 µg/L). This suggests alternative Cd uptake pathways, such as dietary intake from contaminated algae or sediments. Additionally, larger limpets exhibited higher Cd concentrations, highlighting the importance of considering organism size in biomonitoring studies. The bioconcentration factor analysis further indicated significant site-specific differences, with the highest factor at Namaqua National Park (S. granularis: 32.59±15.62; S. capensis: 22.81±11.29). These findings highlight the relationship between environmental exposure and physiological traits in Cd bioaccumulation and the necessity for site-specific assessments and using multiple bioindicator species in environmental monitoring. This study shows the importance of continued research into long-term and spatial variations in metal bioaccumulation in marine ecosystems. Significance: • This study highlights Cd bioaccumulation in limpets, indicating potential pollution pathways. • We have demonstrated that S. granularis and S. capensis can serve as bioindicator species for Cd monitoring. • Results on spatial significance stress the importance of site-specific monitoring. • Our results show that organism size matters in pollution assessments. • There was no correlation between metal concentration in the water and that in the organism.