I’m an aquatic ecologist specialised on host-parasite interactions in plankton and the contribution of parasites to aquatic food-web structure and functioning. Parasites have direct, detrimental effects on individuals. But as regulators of populations they can have indirect, positive effects on nutrient and energy flows in food webs and on community diversity. Hence, disease can affect composition and structure of entire ecological communities with repercussions on ecosystem functioning and thereby on economy and human wellbeing. I approach these research questions experimentally and theoretically at different organisational and temporal scales by combining long-term data analysis, field data, laboratory experiments and ecological models.