Mireille Consalvey PhD Thesis - University of St Andrews

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that the upwards migratory response for the microphytobenthic community on
the Eden in April 2000 was purely light driven.
The migration models of Hopkins (1966), Palmer and Round (1965) and
Round and Palmer (1966) all discussed that the response and strength of
response, of motile organisms might vary; therefore, whilst light may bring cells
to the surface, light is not necessarily the cue that will
drive downwards
migration. Cells were exposed to a normal day time low tide period (exposed and
illuminated). In the absence of any change in conditions there was no evidence of
a downwards migration. Therefore, an endogenously
driven downwards
migration on the Eden was discounted. A significant decline in the F, 15 yield was
seen with cores that were darkened, submerged as well as darkened and
submerged. Therefore, both water inundation and light seem to have a key role in
driving downwards migration. Darkening resulted in a decline of 61 +6%
compared to 51 +4% of cores that were submerged, which could
indicate light
(or lack of) as having a stronger influence on downwards migration rather than
tidal inundation alone. A decline of 78 +3% was seen when cores were
darkened and submerged.
4.4.4. Changes in the maximum light utilisation efficiency over low tide
The maximum light utilisation efficiency (FIF,, 15) significantly
decreased over the exposure period for cores taken from the Tay and Eden
(February). There are several possible reasons for this:
QA was not fully oxidising during dark adaptation
NPQ was not fully reversing during dark adaptation
Low biomass
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