HYPNOZYGOTE CYSTS IN THE GULF OF MAINE

Hypnozygote cysts are a known stage in the life cycle of Alexandrium spp. Negatively buoyant cysts purportedly fall,to the benthos where they undergo mandatory quiescence until their endogenous clock makes germination possible. If oxygen is present and the endogenous clock allows, germination will occur at a rate proportional to light and temperature. Offshore in the Gulf of Maine, where Alexandrium blooms are well documented, the paradigm of benthic cysts is problematic. Sediment surveys have found wide distribution of cysts, with highest cyst concentrations below 100 m in areas where deposition is favored. Germination at these depths is likely slow due to light inhibition; negative effects of burial on germination rate, and losses of cells during the transit from benthos to photic zone also present problems. The purpose of this study was to determine if cysts are suspended in the water column where they would be better positioned to initiate springtime Alexandrium populations. During cruises in February, April, and June of 2000, thirty liter samples were taken from the near-bottom, the top of the bottom nepheloid layer, and near surface, concentrated and stained with primulin for examination using epifluorescenc