Mireille Consalvey PhD Thesis - University of St Andrews

significantly higher in the top 0-200/0-400 [tm. The % of total chlorophyll a (in
the top mm) found in the top 400 [tm varied from 40-60%. Therefore, as
sampling depth increases so does the dilution factor of the chlorophyll a content.
Chlorophyll a was expressed as a total in the upper I mm and in 200 [tm depth
sections to compare coarse and fine scale sampling.
PAM fluorescence techniques have been used to assess relative changes
in biomass in the sediment surface layers (Chapters 4 and 5; Ser6dio et al. 1997,
Underwood et al. 1999; 2001; Barranguet and Kromkamp 2000; Honeywill
2001; Perkins et al. 2001; Honeywill et al. 2002). Using fluorescence
parameters, diel/tidal rhythms in microphytobenthic migration have been
detected and one of the principal aims of this study was to investigate if
microscale changes in chlorophyll a could be used to detect such rhythms.
Significant changes in the chlorophyll a content of samples from Point
Clear (day 2,1999) and the Hythe (days I and 2,2000) over the die] period
occurred. At both sites the trends were detected at both the coarse (I mm) and
fine scale (ýtm) level and therefore no advantage was associated with fine scale
sectioning.
6.4.2. How does assemblage type influence the spatial and temporal distribution
of microphytobenthic biomass?
The patterns of change in chlorophyll a did vary between sites and with
assemblage type. Several of the sites provided evidence of patterns characteristic
of either a tidal/diumal rhythm, but these were not significant. However, the
chlorophyll a content significantly changed over time in cores from Point Clear
(diatom dominated; 1999) and the Hythe (euglenoid dominated; 2000).
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