The effect of polluted sediment on the gonadal development and embryogenesis of bivalves ☆

Cockles (Cerastoderma edule) and Baltic clams (Macoma balthica) were kept on polluted sediment from the harbour of Rotterdam, and on clean sediment from the Wadden Sea (control). Their gametogenesis was then followed. In vitro fertilisation (IVF) experiments were carried out and larvae were cultured until the D-stage (veliger-stage). At the end of the experiment, in animals from the Rotterdam harbour sediment, the condition-index (CI) and gonad-index (GI) were significantly lower, whereas the proportion of parasitised animals was higher than in the controls. Spawning- and fertilisation percentages were also lower in animals kept on harbour sediment. Larval development did not show significant differences.