In benthic food webs, parasites with complex life cycles frequently increase their transmission to definitive hosts (where reproduction occurs) by increasing the susceptibility of intermediate hosts to predation by definitive hosts. While recent evidence finds that eutrophication can alter the relationships between hosts and parasites, whether eutrophication interacts with intermediate host modification to influence infection prevalence and food web structure remains unknown. We develop a nutrient-limited food web model to investigate how parasitic manipulation of intermediate host susceptibility, nutrient supply, and predator diversity determine parasite abundance and infection prevalence in intermediate and definitive hosts.

Results/Conclusions

We show that the effects of intermediate host susceptibility on parasite abundance and infection prevalence are not only less responsive than effects due to increasing nutrients, but are also dependent on enrichment. In contrast, the coexistence of competing definitive hosts and “dead-ends” (where parasites cannot reproduce) depends on the susceptibility of intermediate hosts, but does not depend on enrichment. Our results suggest that anthropogenic changes in nutrient supply will have a greater effect on parasite abundance and infection prevalence in benthic systems than responses of intermediate hosts to parasites, but responses of intermediate hosts will have a greater influence on benthic food web structure than enrichment.