title: Factors regulating excystment ofAlexandriumin Puget Sound, WA, USA.
abstract: Factors regulating excystment of a toxic dinoflagellate in the genusAlexandriumwere investigated in cysts from Puget Sound, Washington State, USA. Experiments were carried out in the laboratory using cysts collected from benthic seedbeds to determine if excystment is controlled by internal or environmental factors. The results suggest that the timing of germination is not tightly controlled by an endogenous clock, though there is a suggestion of a cyclical pattern. This was explored using cysts that had been stored under cold (4 °C), anoxic conditions in the dark and then incubated for 6 weeks at constant favorable environmental conditions. Excystment occurred during all months of the year, with variable excystment success ranging from 31-90%. When cysts were isolated directly from freshly collected sediments every month and incubated at the in situ bottom water temperature, a seasonal pattern in excystment was observed that was independent of temperature. This pattern may be consistent with secondary dormancy, an externally modulated pattern that prevents excystment during periods that are not favorable for sustained vegetative growth. However, observation over more annual cycles is required and the duration of the mandatory dormancy period of these cysts must be determined before the seasonality of germination can be fully characterized inAlexandriumfrom Puget Sound. Both temperature and light were found to be important environmental factors regulating excystment, with the highest rates of excystment observed for the warmest temperature treatment (20 °C) and in the light.
authors.affiliation: University Corporation for Atmospheric Research, Joint Office for Science Support, Visiting Scientist at Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd. E., Seattle, WA 98112, USA.
authors.forename: Stephanie K
authors.initials: SK
authors.lastname: Moore
authors.affiliation: Environmental and Fisheries Sciences Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd. E., Seattle, WA 98112, USA.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Bill
authors.affiliation: University of Washigton, under contract to Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd. E., Seattle, WA 98112, USA.
authors.forename: Levi R
authors.initials: LR
authors.lastname: Hay
authors.affiliation: University of Washigton, under contract to Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd. E., Seattle, WA 98112, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Emenegger
authors.affiliation: University of Washigton, under contract to Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd. E., Seattle, WA 98112, USA.
authors.forename: Kiara C
authors.initials: KC
authors.lastname: Eldred
authors.affiliation: University of Washington Tacoma, Campus Box 358400, 1900 Commerce St., Tacoma, WA 98402, USA.
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Greengrove
authors.affiliation: University of Washington Tacoma, Campus Box 358400, 1900 Commerce St., Tacoma, WA 98402, USA.
authors.forename: Julie E
authors.initials: JE
authors.lastname: Masura
authors.affiliation: Woods Hole Oceanographic Institution, MS#32, Woods Hole, MA 02543, USA.
authors.forename: Donald M
authors.initials: DM
authors.lastname: Anderson
keywords: Alexandrium; Cysts; Excystment; Harmful algal bloom; Puget Sound; Red tide