Mireille Consalvey PhD Thesis - University of St Andrews

('haPltcT 7
-Migiatoiv \. -,. tion-, mivratory hiot-Ifills
(Perkins et al. 2002). Therefore the aims of this chapter were to examine the
effect of light (and temperature) on the PAM fluorescence yields of
microphytobenthic communities and to consider the implications of using
parameters such as F,, 15 under in situ conditions.
Hypothesis 1: Temperature will have a significant effect on fluorescence yield
The minimum fluorescence yield has previously been described to be
virtually invariable under a wide range of temperatures representative of in situ
(Ting and Owens 1994; Scr6dio et aL 1997). Overall, the minimum fluorescence
yield has been described to be the least sensitive over the temperatures 10 - 35
'C and therefore recommended as being the most reliable parameter to trace
changes in the chlorophyll a content at the sediment surface (Ser6dio et al.
2001). Some species-specific differences have been recorded (Ser6dio et al.
2001) and attributed to fundamental differences in the photosynthetic apparatus
(the discussion of which is outwith the scope of this study). In this study the
minimum/maximum fluorescence yields as well as the maximum light utilisation
efficiencies, were all apparently affected by temperature and hypothesis I was
accepted.
The same volume of diatom solution was added to each filter paper to
create an artificial biofilm. Since the stress of filtering cells was undeten-ninable
the cells were left to acclimatise over night (divided between the water baths).
During this period significant differences in the fluorescence parameters F,, F,,
and FIF,, occurred, with all variables being significantly higher at the lower
temperature of 10 'C. Therefore, even a temperature difference of 10 'C can
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