Preliminary determinations of heavy metals in winkles Littorina littorea along a concentration gradient in the Fal Estuary suggested that whole body concentrations might be related to those of the water. When animals were transplanted to this heavily contaminated estuary, changes in tissue concentrations of As, Co, Cu and Zn were largely complete after 2 months.
Relations between the winkle and water concentrations may be indirect since its algal diet is thought to be the main source for most heavy metals. Data from a large number of United Kingdom estuaries were used to compare concentrations of 12 metals in L. littorea with those of the brown seaweed Fucus vesiculosus which forms part of its diet. Very significant relations were found for Ag, As, Cd and Pb, suggesting that since concentrations in the seaweed probably reflect those of the surrounding water, so also do those of the winkle. However, concentrations of Ag in the animal also appeared to be influenced by dietary Cu levels. In addition, significant relations between the two species were found for Cu, Fe, Hg and Zn, but the slopes were shallow, perhaps indicating regulation by the winkle. For Cr and Mn relations were not very significant and, for Co and Ni, concentrations in the winkle appeared to be influenced by those of Cu and Zn.
Compared with concentrations in L. littorea, those of L. littoralis from the same site were generally higher whilst in L. saxatilis they were usually of the same order or lower.
In assessing the winkle as an indicator of metal contamination the present results have been combined with those of other workers to produce comparisons between most estuaries in England and Wales. It is concluded that whilst the winkle is a useful indicator for Cd and a few other metals, it is certainly not a perfect indicator organism.