Dark survival
strategies in marine phytoplankton assessed by cytometric measurement of metabolic
activity with fluorescein diacetate
by
Frank J. Jochem
Marine Biology 135: 721-728; 1999
ABSTRACT
Cytometric quantification of cellular fluorescence upon cleavage of fluorescein
diacetate (FDA) is presented as a sensitive and rapid technique to assess
phytoplankton metabolic activity during exposure to prolonged darkness of
10-12 days. Two distinct types of metabolic response upon darkness are
distinguished: Type I cells (Brachiomonas submarina, Pavlova lutheri,
Chrysochromulina hirta) adapt to prolonged darkness by reducing their
metabolism to a lower level of activity (~10% of initial in P. lutheri,
C. hirta, ~0.5% in B. submarina) within few days whereas type II cells
(Prymnesium parvum, Bacteriastrum sp., unidentified pennate diatom)
continue with unchanged activity. Type I cells were able to maintain
their initial cell abundance and commenced rapid cell growth upon
re-illumination after 12 days of darkness. Among type II cells, diatoms
were able to maintain cell abundance and growth capacity as well whereas
P. parvum was not. Type I cells are expected to exhibit competitive
advantages in environments with frequent or long dark periods. Bacterivory
further supports dark survival in C. hirta.
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