Mireille Consalvey PhD Thesis - University of St Andrews

v vs. 11011-IT . ratory hiolilms
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seem that the microphytobenthic assemblage samples were less migratory than
those seen previously. This may reflect a shift in species and would require
further investigation, but at this stage the hypothesis 7 must be rejected.
The light utilisation efficiencies of natural and artificial b1ofilms
significantly declined after 90 min of treatment. However, there was evidence of
recovery in the natural biofilms during a 15 min dark adaptation period in
samples from the low and medium light condition. This was not found in the
high light condition and therefore light history did significantly affect the light
utilisation efficiency. In artificial biofilms cells from the medium and high light
conditions did not recover and this may reflect the inability of cells to migrate
into the sediment, therefore cells in the artificial biofilm were receiving more
light than cells in the sediment biofilm.
Hypothesis 8: 15 min of dark adaptation will lead to a significant decrease in the
minimum fluorescence yield and significant increases in the maximum
fluorescence yield and light utilisation efficiencies
No decline in the minimum fluorescence yield was found in the artificial
biofilm but there was a significant decrease in sediment cores, suggesting QA
oxidation or migration. As no decline was seen in ar-tificial biofilms, migration
may be implicated as the most probable reason, but further investigation is
necessary. There was an increase in the maximum fluorescence yield in the
artificial biofilm but no change was seen during 15 min of dark adaptation in the
sediment cores. It is possible that migration was occurring in the sediment cores,
therefore obscuring any increase associated with NPQ reversal. Regardless, in
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