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: 4:15:00 PM

Location: Cochiti/Taos

Campbell, R, G, Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA, campbell@gso.uri.edu

Teegarden, G, J, Environmental Studies, Bowdoin College, Brunswick, ME, USA, gteegard@bowdoin.edu

Cembella, A, D, Institute for Marine Biosciences, NRC, Halifax, NS, Canada, Allan.Cembella@nrc.ca

Durbin, E, G, Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA, edurbin@gso.uri.edu

THE ROLE OF ZOOPLANKTON GRAZERS IN ALEXANDRIUM SP. BLOOM DYNAMICS IN THE NEAR-SHORE ENVIRONMENT OF THE GULF OF MAINE

We collected samples at weekly intervals from several stations in coastal waters of the Gulf of Maine during the spring of 1998 and 1999 for zooplankton and phytoplankton abundance, biomass, species composition, and toxin content. In addition, grazing rates of zooplankton were determined using natural water samples. During 1998, there was a moderate bloom of Alexandrium (3000 cells/L), while in 1999 concentrations were very low throughout the study. In 1998, grazing impacts increased from 0 to 80% / day in concert with the vernal increase in zooplankton biomass and appeared to contribute to the bloom’s demise. The feeding behavior of the zooplankton on Alexandrium sp. was species specific: the copepod Acartia hudsonica was non-selective, the copepod Calanus finmarchicus was somewhat selective, and barnacle nauplii avoided them. Toxin levels in zooplankton tissues appeared to be sufficient to pose risks to higher trophic levels. Our findings suggest that grazing can be an important source of mortality and will depend on zooplankton filtration rates, degree of selective feeding, and the biomass and species composition of both the phytoplankton and zooplankton communities.

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Aquatic Sciences Meeting, Albuquerque 2001

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