Mireille Consalvey PhD Thesis - University of St Andrews

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7.2.2. Experiment 1: The effect of different light intensities and temperatures on
fluorescence parameters in a non-migratory biofilm
Artificial biofilms were created (Winter, 2000) and placed in the dark
(representing night/immersion) ovemight (12 h) to acclimatise. The samples
were randomly assigned to a 10 or 20 'C water bath under a Halogen light
(Figure 7.3). The experiment was conducted in a 10 'C cold room; therefore the
10 'C bath was at ambient temperature but the 20 T bath was heated by two
tropical aquarium heaters. The water was constantly circulated to minimise any
temperature increases as a result of the lights. The cores were pen-nanently
emerged to prevent cell loss into the water column. To maximise
the water baths were surrounded
by foil.
light intensity,
After the ovemight period, and at the time co-inciding with the start of
the exposure period at the site, the first fluorescence measurements (F,, and F,, )
were taken and the maximum light utilisation efficiency (FIF,, ) calculated
(FMS2). The cores were then exposed to one of 4 light regimes
(Dark/Low/Medium/High light) (n = 4) for the duration of the low tide period (6
h) (Figure 7.3; Table 7.1).
Table 7.1: Four different light regimes
PPFD ( -tmol m-2 s- f)
Temperature Dark Low Medium High
Low (I O'C) 0 5 90 300
High (20 OC) 0 5 .
120 370
Each core was exposed to its own light by means of a filter lid. The fluorescence
yield before the saturating beam (F, in the dark samples and F in the light
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