Trophic interactions also play a role in the dynamics of algal blooms. Species of Amoebophrya are particularly noteworthy, as they are widely distributed in coastal environments, with infections known for numerous host taxa from Europe, North America, Asia, and Australia. Infections prevent reproduction of the host, are short in duration, and invariably result in death of the host, all of which make these parasites likely candidates for controlling host populations. Infection levels are highly variable, ranging from < 1 to 80% in a variety of coastal settings, with high levels of parasitism usually associated with high host abundance. Epidemic outbreaks of Amoebophrya have been linked to the decline of dinoflagellate blooms in several marine systems, with estimates of parasite induced mortality of host species ranging from a maximum of 8% daily in the main stem of Chesapeake Bay to 54% daily in a shallow subestuary of the Bay.

The focus of our research proposal is on the dinoflagellate parasite from the genus Amoebophrya, and its interaction with its HAB-forming host, Alexandrium tamarense, a toxic dinoflagellate that impacts U.S. coastal waters. This work will seek to further our basic understanding of this little-known group of parasitic organisms, including their biology, life history, behavior, and local distribution over space and time. This work will also further investigate the interaction and dynamics between parasite and host to examine how this parasite can influence host abundance both in the laboratory and in the field. These studies, together with practical and ecological considerations, may allow us to evaluate the strategy of using this parasite as a biological agent to control harmful algal blooms like those produced by Alexandrium tamarense.

Alexandrium sp. bloom in Japan affecting aquaculture

Alexandrium sp. bloom Alexandrium sp. cell infected by Amoebophrya sp. (DIC)
Amoebophrya sp in Alexandrium cell (protargol) Amoebophrya sp in Alexandrium cell (protargol) Amoebophrya sp in Alexandrium cell (epifluorescence) Red= host, Green= parasite< /SPAN>