Digenetic trematodes are important organisms in shallow-water ecosystems, being parasites of several other animals. These parasites may exhort significant impact on the physiology of their hosts. Yet, they have rarely been taken into account in environmental studies. Trematodes are cryptic determinants of the population dynamics of their hosts, such of benthic organisms monitored in coastal systems, and their ecological repercussions are thus far unknown. In this work, the Mondego estuary is used as a model case, in a long-term study of how environmental factors (eutrophication and standard...