Mireille Consalvey PhD Thesis - University of St Andrews

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Considerable variation in the times for biofilm formation have been
described (see section 4.1.3), from 18 min (Paterson et al. 1998) to 2h (Aleem
1950). The findings of this study fit in between previous times; over 50 % of the
total increase occurred after 94 min of exposure on the Tay Estuary and 60 min
on the Eden (February). However, on the Eden in April it took longer for a
significant increase to occur (210 min); a time scale that supports the findings of
Aleern (1950) and Round and Palmer (1966). Within the space of two months,
there was a clear difference in the migratory patterns on the Eden Estuary. This
may reflect a change in taxonomic composition, biomass or some other
enviro=ental variables.
There was a significant decrease in the F,, 15 yield during the final hour of
exposure on cores from the Tay. This decrease is indicative of an endogenous
rhythm entrained to the time of tidal inundation. At the end of the experiment
some cores were flooded to see if this decline would continue; it did, and the
final F, 15 yield was significantly lower than the initial value. Making the
assumption that two F, '5 values are directly comparable, this could indicate that
cells were deeper at the end of the expenment than at the start, suggesting that at
the start of the experiment cells were already moving to the surface, further
demonstrating an endogenous rhythm.
Whilst there was an apparent decrease in F,, 15 at the end of the low tide
period for the Eden (February), it was not significant. This would agree with the
findings of Perkins (1960) and Honeywill (2001) that cells on the Eden do not
migrate away at the time of high tide. At the time corresponding to tidal
inundation, cores that were darkened and immersed showed a significant
decrease in the F, '5 yield, which was not found for cores that were left exposed
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