Parasites in marine food webs

Parasites have important and unique impacts on marine food webs. By infecting taxa across all trophic levels, parasites affect both bottom-up and top-down processes in marine systems. When host densities are high enough, parasites can regulate or even decimate their populations, causing regime shifts in marine systems. As consumers and resources, parasites are enmeshed in food webs in ways that are different from free-living species. Their unique lifestyle renders parasites more susceptible to perturbations than their free-living hosts. As a result, parasites serve as useful indicators of ecosystem integrity. A theory for how food webs affect parasites will help us better understand why a particular infectious disease has become problematic, give insight into how restoration might reduce a costly marine disease, or let us use parasites as indicators to follow changes in food-web complexity.