THE EFFECT OF POLLUTED SEDIMENT ON THE GONADAL DEVELOPMENT AND EMBRYOGENESIS OF BIVALVES

Cockles (Cerastoderma edule) and Baltic clams (Macoma balthica) were k ept on polluted sediment from the harbour of Rotterdam, and on clean s ediment from the Wadden Sea (control). Their gametogenesis was then fo llowed. 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 co ndition-index (CI) and gonad-index (GI) were significantly lower, wher eas the proportion of parasitised animals was higher than in the contr ols. Spawning- and fertilisation percentages were also lower in animal s kept on harbour sediment. Larval development did not show significan t differences.