Factors influencing the concentrations of heavy metals in the asteroid Asterias rubens L. (Echinodermata)

Seasonal, geographical, anatomical and sex-related variations in heavy metal concentrations were investigated in the asteroid Asterias rubens collected in four representative biotopes of the NE Atlantic at four periods of an annual gametogenic cycle. Zn, Pb, Cd, Fe, Cr, Cu, Ti and Hg concentrations were measured in the gonads, the central digestive tract, the pyloric caeca, the body wall and the skeleton. According to multi-way analyses of variance, the factors considered in the present study accounted for a large proportion (59–93%) of total variability in concentrations of all metals except Hg (26%). The body compartment appeared as the most important factor (9.7 – 88% of total variability). Interactions between the body compartment and the sampling location factors accounted for up to 29% of total variability indicating that bioaccumulation differed from site to site. Weak interactions between the body compartment and the sampling period factors indicated that bioaccumulation was synchronous within the asteroid body. Concentrations of groups Ib and IIb metals and Fe were significantly higher in the pyloric caeca. The other elements were preferentially accumulated in the skeleton. Most bioconcentration factors (BCF) towards prey were lower than 1 in asteroids feeding on filter-feeders (ascidians and mussels). On the contrary, most BCF in asteroids feeding on grazers (gastropods) were higher than 1. Sex-related differences in the gonads were significant for Zn, Cd, Fe and Cr concentrations (variation ratio: 1.7 – 3.3).