Kremp, A. University of Helsinki, Devision of Hydrobiology,

The germination of resting cysts is a basic requirement for the initiation of the vernal dinoflagellate blooms in the northern Baltic Sea, which is regulated by endogenous and environmental mechanisms. Dormancy, temperature and oxygen conditions as factors controlling germination of Scrippsiella hangoei resting cysts were studied in laboratory experiments. Monthly incubation of newly formed cysts in + 3 C and 12/12 light:dark cycle showed, that cysts must proceed 5-6 months of mandatory dormancy before they are physiologically able to germinate. Mature cysts were exposed to a range of temperatures between 0 and 20 C. Low temperatures (1-5 C) are favourable for the germination of S. hangoei whereas temperatures >9 C completely suppress excystment.The potential of anoxia to override favourable temperatures was tested by anaerobic incubation of resting cysts. Germination does not occur in total anoxia and germination frequencies remain low in hypoxic conditions. Subsequent exposure of the resting cysts to normoxic conditions showed, that short periods of anoxia, particularly if coupled to the presence of H2S, can significantly decrease the germination potential. Thus, prolonged periods of anoxia at the sediment surface as currently observed in the study area might diminish the seed population and cause problems in S.hangoei bloom initiation.
Day: Thursday, Feb. 4
Time: 02:30 - 02:45pm
Location: Hilton of Santa Fe
Code: SS24TH0230H