Total and organic Hg concentrations in cephalopods from the North Eastern Atlantic waters: Influence of geographical origin and feeding ecology

Total (T–Hg) and organic (O–Hg) mercury concentrations and tissue distribution were examined in 20 species of cephalopods (n=278) from the north eastern Atlantic waters, i.e. from the Bay of Biscay to the Faroe Islands. Concentrations of T–Hg in whole cephalopods showed elevated variations among species, i.e. from 40 to 3560ng g−1 dwt, but a low variability within each species (mean CV%=39%). With the exception of oceanic squids, the digestive gland globally displayed higher T–Hg concentrations than the remaining tissues. In contrast, O–Hg concentrations determined in selected species were generally higher in the remaining tissues. Despite higher T–Hg concentrations, the digestive gland weakly contributed to the total body burden of both T–Hg and O– Hg (<25% and <15%, respectively). In fact, from 75% to 95% of the T–Hg and O–Hg were contained in the muscular remaining tissues. Therefore, O–Hg may have a strong affinity to proteins in cephalopods. Sex and size only significantly influenced the bioaccumulation of Hg for the Loliginidae family. T–Hg and O–Hg concentrations were also influenced by geographical origin: Celtic Sea>Bay of Biscay>Faroe Islands, corresponding to the seawater Hg concentrations in these areas. In the Faroe Islands and the Celtic Sea, benthic cephalopods contained significant higher Hg concentrations compared to pelagic ones. This suggests that diet is not the main pathway of Hg uptake in cephalopods as pelagic species were expected to be more exposed to O–Hg through fish consumption than benthic ones.