Mireille Consalvey PhD Thesis - University of St Andrews

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been detailed (see General Introduction) and therefore understanding the
colonisation and recovery rates of microphytobenthic biofilms is essential in our
understanding of the estuarine ecosystem. The rate of recovery is important if
these systems are to respond to the predicted threat of sea level rise (15 - 90 cm
over the time period 1990 - 2100 was predicted by Jones 1994), increased storyn
frequency, as well as from episodic pollution and disturbance events.
Underwood and Paterson (1993) monitored the recovery of an intertidal
benthic diatom assemblage after a biocide treatment. Immediately there was a
significant decrease in chlorophyll a (as a proxy for biomass) as well as a
decrease in the concentration of colloidal carbohydrate. Associated with the
death of the cell population was increased sediment erosion and transport away
from the site by the tides. However, after 6 days the chlorophyll a content had
returned to levels similar to the control site. The source of the recolonising
organisms was unclear. Lateral recolonisation was considered unlikely based
upon the speed of diatom locomotion (estimated maximum speed =2m
Recolonising cells could have come from below the surface or from the water
column. No correlation was found between stability and carbohydrate content but
higher rates of erosion at the biocide treated site were observed. A positive
relationship between chlorophyll a and carbohydrate concentration was detailed
and a model has since been developed by Underwood and Smith (1998) to
predict sediment colloidal carbohydrate concentration from chlorophyll a; this
model has been verified by Kelly et al. (2001).
Using fine scale sectioning techniques, spatial/temporal differences in
biomass and carbohydrate distribution can be detected (Taylor and Paterson
1998; de Brouwer and Stal 2001; Kelly et al. 2001). Sampling at 200 ýtm depth
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