Aquatic Sciences Meeting, Albuquerque 2001

SS20 Biological Control of Harmful Algal Blooms: Role of Grazers, Parasites, Viruses and Bacteria

Date: Monday, February 12, 2001, Time: 2:30:00 PM

Location: Cochiti/Taos

Johansson, M, B, Stockholm University, Dept of Systems Ecology, Stockholm,SE-10691, Sweden, mojo@system.ecology.su.se

Coats, D, W, Smithsonian Environmental Research Center, Edgewater MD 21037-0028, USA, coats@serc.si.edu

CILIATE GRAZING ON THE PARASITE AMOEBOPHRYA SP DECREASES INFECTION ON THE RED TIDE DINOFLAGELLATE GYMNODINIUM SANGUINEUM

Gymnodinium sanguineum (Dinoflagellata) often causes red tides in Chesapeake Bay on the East Coast of USA (38°52’N 76°32’E). The parasitic dinoflagellate Amoebophrya sp. is known to infect and kill G. sanguineum, and can be a regulating factor of the red tides. However, G. sanguineum is not always infected although the conditions are favorable, i.e. high cell number of G. sanguineum. We explored the possibility that grazing on Amoebophrya sp. by ciliates is regulating the infection of the red-tide G. sanguineum. Laboratory experiments shows that the ciliate Strobilidium sp. (Choreotrichida) could eat and digest Amoebophrya at high rates. Further experiments revealed that grazing by Strobilidium on Amoebophrya decreased the infection of G. sanguineum by 70-80%. Field populations of ciliates from Chesapeake Bay significantly lowered the infection of G. sanguineum in several experiments. This implies that grazing by natural populations of ciliates on Amoebophrya may be a controlling factor on the infection of G. sanguineum in nature. Thereby, ciliate grazing on parasites may also indirectly regulate the occurrence of red tides.

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Aquatic Sciences Meeting, Albuquerque 2001

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