Mireille Consalvey PhD Thesis - University of St Andrews

Chý N"I blofilllllýý
artificial and natural assemblage (2) cells in the sediments were receiving less
light because of the rapid attenuation of light in the surface sediment/bio film than
those in the artificial biofilms. The lens tissue sampling method for the artificial
biofilms only includes the motile fraction of the community; it is possible that
episammic forms may have contributed to the overall fluorescence yields of the
natural assemblage and therefore account for the difference in the light utilisation
efficiencies. However, motile forms dominate biofilms on the Eden Estuary
(pers. obs. ) and therefore hypothesis 2 is the most probable reason for any
difference. These higher light utilisation efficiencies further demonstrate that the
estimation of relative electron transport rate (rETR) from FqIF,, ' x PPFD/2
(Hartig et al. 1998; Kromkamp et al. 1998: Barranguet and Kromkamp 2000;
Underwood in press) may be falsely high in intact sediment biofilms, supporting
the findings of Perkins et al. (2001; 2002).
The work in this study demonstrates that care must be taken with all
fluorescence measurements and that far-red adaptation should be considered as a
treatment prior to measuring F, and F,, in microphytobenthic assemblages,
especially for the consideration of parameters such as maximum light utilisation
efficiency and NPQ.
Hypothesis 7: The patterns of change in the fluorescence yields will significantly
differ between a migratory and a non-migratory biofilm
No clear trends over time were evident with the fluorescence yields of
either the artificial (non-migratory) or natural (migratory) biofilm. The minimum
fluorescence yields were comparable to previous studies and therefore it would
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