A. Kremp, Effects of cyst resuspension on germination and seeding of two bloom-forming dinoflagellates in the Baltic Sea, MAR ECOL-PR, 216, 2001, pp. 57-66
The implications of cyst resuspension on germination and subsequent seeding
of the 2 spring-bloom dinoflagellates Scrippsiella hangoei (Schiller) Lars
en and Peridiniella catenata (Levender) Balech from the Baltic Sea were inv
estigated in a field study and laboratory experiments. Sedimentation of res
uspended cysts was monitored by an automated sediment trap in 2 consecutive
winters prior to and throughout the germination period off the SW coast of
Finland. The effects of increased irradiances and water motion on germinat
ion and germling survival were tested by incubating cysts at different ligh
t levels and in turbulent water, Cyst fluxes of both species were low durin
g the calm and cold winter of 1998/1999. In 1999/2000, heavy storms caused
strong resuspension of S. hangoei cysts, Light significantly increased the
germination frequency of S. hangoei cysts and supported germling survival a
nd cell division. In P. catenata, the percentage of excystment was not sign
ificantly influenced by light and germination was successfully completed in
both darkness and light. Subsequent growth of the species, however, requir
ed light, although maximum cell numbers were encountered at an irradiance a
s low as 10 mu mol m(-2) s(-1). Small-scale turbulence reduced the germinat
ion frequency of S. hangoei but did not affect excystment in P. catenata. N
o negative effects on subsequent growth were detected. The favourable effec
ts of light on germination and germling survival of S. hangoei emphasize th
at resuspension would be advantageous for the bloom initiation of this spec
ies. Cyst resuspension seems to be less important in P. catenata population
dynamics, since germination can be successfully completed in darkness and
the amount of cysts transported to the water surface is insignificant even
with strong turbulent mixing. It is concluded that cyst resuspension may be
advantageous for dinoflagellate bloom initiation, depending on its extent
and timing and the specific germination requirements of the respective orga
nism.