Abstract:
Although marine parasites are often small cryptic organisms that are difficult to study, they are a highly adapted, diverse group of organisms playing important roles within ecosystems. Parasites have complex lifecycles that involve a single host or a number of intermediate hosts. Parasites have been shown to act as ecosystem engineers, sometimes changing the behaviour of one host in order to enable their transition to the next host. The many modifications that individual parasites make have implications for the structure of food webs and the functioning of ecosystems. Their ubiquitous presence can be used to understand the structure of and pressures on host species and food webs. While it is tempting to assume that parasites have similar biogeographic patterns as their hosts, studies have shown that external parasites have different spatial distribution trends, trends which have implications with regards to climate change. Although marine species are generally expected to decline as climate change increases, current research indicates that climate change may be favorable for parasite pathogenicity and distribution. This could have economic impacts on fisheries and aquaculture and biological impacts on the function and structure of marine ecosystems. This article reviews our current biological and ecological knowledge of parasites, discusses how parasites have been used as a tool to understand other aspects of the marine realm, and outlines current predictions regarding the response of parasites to climate change.