Parasites have important consequences for the ecology and evolution of their zooplankton host populations. Many endoparasites and epibionts produce resting spores that infect new hosts upon intake. We explored the hypothesis that these spores build up dormant stages in the sediment of Greifensee, which therefore becomes infectious to crustaceans such as Daphnia. We focused on the endoparasite Caullerya mesnili and the epibiont Vorticella sp. In laboratory experiments, we exposed Daphnia galeata and Daphnia galeata × hyalina to sediment suspensions from Greifensee. In a mesocosm experiment, we placed sediment in aquaria and let it develop for two months. The sediment sampling took place in spring 2006 before the usual outbreak of C. mesnili. Most Daphnia analyzed were infected with the epibiont Vorticella sp., suggesting that this parasite forms dormant stages. In one replicate aquarium the endoparasite C. mesnili was found in hatched Daphnia. The presence of C. mesnili spores can not be affirmed with certainty since a) we only found C. mesnili in Daphnia in one aquarium; b) we have a lack of knowledge of activation stimuli and c) other transmission pathways of this parasite were not tested. Despite the uncertainties, these results indicate that C. mesnili can form dormant stages, which can have a profound influence on the coevolution of the Daphnia-endoparasite system.