Mireille Consalvey PhD Thesis - University of St Andrews

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living on, as well as moving through, fine cohesive sediments. The ability of the
microphytobenthos to migrate makes such aggregations variable in both space
and time. Therefore, the traditional definition of biofilms being fixed to a
substratum do not hold true in sedimentary systems and the formation of
microphytobenthic biofilms can be examined over several time scales:
9 Pnmary development as cells colonise a new area
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0 Secondary development as cells migrate to the sediment surface to
photosynthesise
9 Tertiary development as cells sub-cycle within the biofilm.
Therefore, microphytobenthic biofilms are not necessarily fixed in time and
space. Epipelic cells are able to respond to changing environmental conditions,
therefore having a selective advantage over non-motile species.
Underwood and Paterson (1993) monitored the development of a
microphytobenthic biofilm after the application of biocide. In this study a storm
disturbance event was simulated and is a more realistic simulation of the natural
situation. The formation of a primary biofilm was examined and it was
demonstrated that the system recovered over a very short period of time (days).
The work suggested that biological changes occur more rapidly than physical
ones but that the physical changes were dependent upon the biological changes.
This was further demonstrated in a more controlled laboratory investigation.
Significant positive correlations were shown between chlorophyll a (biomass)
and colloidal carbohydrate/water and sediment stability. These findings further
demonstrate the pivitol role of microphytobenthos in the functioning of the
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