Trematode parasites are usually omnipresent in coastal and transitional waters, but their pathogenicity is considered low due to lack of overt signs of disease. This often the case for the final and second intermediate host (usually an invertebrate) but not true for the first intermediate host (always a mollusc), where infection can lead to death or castration. Nevertheless, even for final and second intermediate hosts, parasite abundance can reach high values and disrupt basic functions (e.g., reproduction, growth, filtration) with a possible knock-on effect on community and ecosystem (through alterations on functional traits, e.g., bioturbation). Due to its complex life cycle, trematodes experience vastly distinct habitats with varying abiotic and biotic conditions that affect parasite infection success and consequently can alter the ecological interactions of the involved hosts and remaining free-living fauna. Therefore, it is of prime relevance to recognize and examine the parasite-host system dynamics to better predict conservation threats to communities and ecosystems and maximize the success of disease outbreak monitoring and management. I propose to develop an innovative mesocosm approach to examine trematode effects on 1) host-parasite dynamics, 2) the broader community, and 3) at the ecosystem level. The study of host-parasite dynamics and environmental implications is critical, especially in a changing world where diseases’ detrimental or beneficial effects on communities and ecosystems are anticipated to fluctuate dramatically in present and future global change scenarios, with still unknown repercussions. As a result, this proposal aims to highlight parasites as fundamental components of ecosystems by verifying the hypothesis that parasitism is linked to changes in community and environmental influencing processes.
