Elemental composition of whole body soft tissues in bivalves from the Bijagos Archipelago, Guinea-Bissau

Marine bivalves are bioindicators of coastal environmental pollution, integrating monitoring programs worldwide. Nonetheless, the choice of particular species as an indicator requires validation, achieved by understanding the differences in element concentrations among and within species. The present study compares the chemical composition of whole body soft tissues of four common bivalve species from the BijagOs Archipelago, a pristine region of West Africa. Significant differences were recorded in the concentrations of various elements among studied species, which likely arise from species-specific uptake and bioaccumulation processes. Overall, there was a segregation between a group including the bloody cockle Sentha senllis and oyster Crassostrea tulipa (with high Cd and Zn concentrations) versus the two other species, Austromacoma nymphalis (with low Cu and high Mn, Se, Hg, Pb concentrations) and Diplodonta spp. (with high values of Cu, Al, Fe, V, Cr, Hg, Pb). C. tulipa was sampled in two different substrates (rock beds and mangrove roots), and the two groups revealed different chemical profiles, with significantly higher concentrations of P, Si, Zn and Cr and lower Cu in specimens fixed in mangrove roots. These results strongly suggest the influence of small-scale environmental variability on the accumulation of particular elements. We found extremely high Cd concentrations in S. senllis (27.1 +/- 7.53 mu g g(-1) DW) and identified C. tulipa as another high Cd-accumulating species (ca. 10 mu g g(-1 )DW). Our results suggest a detoxifying mechanism linked with the presence of Se to reduce the potential toxic effects of Cd in these two species. Cadmium concentrations reported for some bivalve species in this area largely exceed the maximum values proposed by the European Union, emphasizing the need for a regular contamination assessment.

Automated summary

Marine bivalves serve as bioindicators of coastal environmental pollution and are used in monitoring programs worldwide. This study compared the chemical composition of four common bivalve species from a pristine region in West Africa, revealing significant differences in element concentrations among species. Some species, such as the bloody cockle and oyster, showed higher concentrations of certain elements like Cd and Zn, while others had unique chemical profiles with varying levels of different elements.