Global drivers of parasitism in freshwater plankton communities

Abstract

Zooplankton and phytoplankton communities play host to a wide diversity of parasites, which have been found to play a significant role in a number of ecosystem processes, such as facilitating energy transfer and promoting species succession through altering interspecific competition. Yet we know little about the mechanisms that drive parasite dynamics in aquatic ecosystems. Recent mathematical models have shown how habitat can shape parasite dynamics through influencing the efficacy of parasite transmission; however, these predictions have yet to be tested at larger ecological scales. Here, we present a comparative analysis of parasitism in planktonic communities, assembling data from a range of host and parasite taxa, habitat types, and geographic regions. Our results suggest that the prominent depth-prevalence relationship observed in studies on Daphnia in temperate lakes of North America is applicable to a wide range of aquatic habitats, hosts, and parasites; however, differences in transmission strategies between parasites can lead to considerable variation in parasite dynamics. Observational studies which incorporate a diversity of habitat types will be important in uncovering the mechanisms which underlie this relationship. In particular, more experimental work on transmission stage survivability and infectivity in aquatic environments will be necessary before we can make accurate predictive models of parasite spread in these ecosystems.