Mireille Consalvey PhD Thesis - University of St Andrews

Cha ici 8 Oencral Di-scussion
largely be-determined by drying out and compaction of the sediments as would
be expected, however, more subtle changes were also occurring and may relate to
taxonomic and/or structural (e. g. cell layering) changes within the biofilm.
8.3. Appraisal of main microphytobenthic sampling techniques used
8.3.1. PAM Fluorescence
The linear relationship shown to exist between minimum fluorescence
and microphytobenthic biomass in the laboratory and in situ has been the basis of
several studies into microphytobenthic migration (see Ser6dio et al. 1997,2001;
Honeywill 2001). In this study changes in F,, 15 at the sediment surface followed
the broadly expected patterns of microphytobenthic migration and proved to be a
valuable remote sensing tool.
However, the limitations of the technique must also be considered. Whilst
the linear nature of the relationship between chlorophyll a and
dark level
minimum fluorescence has been shown (Ser6dio et aL 1997; Barranguet and
Kromkamp 2000; Honeywill 2001; Scr6dio et al. 2001; Honeywill et al. 2002)
the slope and intercept of the line are open to variation (Ser6dio et al. 1997).
Therefore the chlorophyll a content per se cannot be inferred from this
technique. Furthen-nore no inference can be made with reference to changes in
the depth distnbution within this zone. In a situation with identical biomass the
distance of cells from the surface, as well as their orientation, may alter the
relationship between F, 15 and biomass (Figure 8.1 A, B and C). Also in a
situation of high biomass (Figure S. ID) there are additional questions relating to
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