Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 7596
Title: Factors regulating excystment of Alexandrium catenella in Puget Sound, WA, USA
Author: Stephanie K. Moore, Brian D. Bill, Levi R. Hay, Jennifer Emenegger, Kiara C. Eldred, Cheryl L. Greengrove, Julie E. Masura, Donald M. Anderson
Publication Year: 2015
Journal: Harmful Algae
Volume: 43
Pages: 103-110
Keywords: Puget Sound,harmful algal bloom,Alexandrium spp.,cysts

Factors regulating excystment of the toxic dinoflagellate Alexandrium catenella were 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 (4ºC), 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 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 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 in A. catenella from 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.

Theme: Sustainable, safe and secure seafood for healthy populations and vibrant communities
Foci: Provide scientific support to ensure safe seafood for healthy populations and characterize how human activities and climate affect risks from pathogens, chemical contaminants and biotoxins