In a dissolution experiment using the calcifying algae Calcidiscus leptoporus the morphological changes of the coccoliths were followed by analysis using scanning electron microscopy. The decrease in coccolith calcite mass during this experiment was quantified. These data were used for the interpretation of coccolith morphologies within faecal pellets produced in separate feeding experiments with the calanoid copepods Calanus helgolandicus and Temora longicornis. Comparison of the observed coccolith morphologies from the coccolith dissolution experiments with the coccolith morphologies observed within the faecal pellets led us to conclude that coccolith dissolution during copepod gut passage is well below 8 weight percent. © Inter-Research 2007.