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: 11:30:00 AM

Location: Cochiti/Taos

Doucette, G, J, National Ocean Service, Charleston, USA, greg.doucette@noaa.gov

INTERACTIONS BETWEEN ALGICIDAL BACTERIA AND SPECIES OF HARMFUL ALGAE

Two bacterial strains that are lethal to Gymnodinium breve, a bloom-forming, toxic dinoflagellate, were isolated from the west Florida shelf. These bacteria belong to phylogenetic groups that include other algicidal representatives: the Cytophaga-Flavobacterium-Bacteroides (CFB) phylum and the gamma-Proteobacteria. Molecular approaches are being used to assess changes in microbial assemblages associated with G. breve following the introduction of algicidal bacteria to algal cultures. Our findings thus far indicate that bacterial growth responds rapidly to the appearance of its target algal species, with bacterial numbers continuing to increase as the algal cells are lysed. In addition, qualitative changes in those phylotypes comprising the microbial assemblage occur throughout the killing event. Although the algicidal agent(s) is produced constitutively by these bacteria, the killing activity of introduced bacteria seems to vary according to the target alga's physiological status, with resistance to attack decreasing with declining algal growth rate. Efforts are also underway to identify the algicide(s) and elucidate its mechanism of action, and thus its potential effects on algal growth and metabolism.

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Aquatic Sciences Meeting, Albuquerque 2001

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