Predicting the population dynamics in Amoebophrya parasitoids and their dinoflagellate hosts using a mathematical model

Free-living, photosynthetic marine dinoflagellates are frequently infected by microparasites of the genus Amoebophrya. Attacks by Amoebophrya can contribute to the termination of dinoflagellate blooms and have been suggested to influence the geographical distribution of certain host species. Because infection terminates with the killing of the host (i.e. Amoebophrya behaves like a parasitoid), the interaction can be considered, from a modeling point of view, similar to the process of predation, with the difference that it takes a longer time for the parasitoid to kill the host as compared to typical predator-prey interactions. In the present work, we explored the population dynamics in Amoebophrya and their dinoflagellate hosts using the Rosenzweig-MacArthur modification of the traditional Lotka-Volterra predation model. The model was parameterized for 3 systems, Akashiwo sanguinea, Gymnodinium instriatum, and Karlodinium micrum, and their respective Amoebophrya parasitoids, using published experimental data. Parameter validation was possible for parasitoid search rate and mortality. The potential for host control by Amoebophrya and the probability for host extinction were studied with respect to carrying capacity, a parameter that is influenced by e. g. eutrophication. The model may be useful to predict conditions under which Amoebophrya can control populations of its dinoflagellate hosts.