Mireille Consalvey PhD Thesis - University of St Andrews

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6.1.3. Examining primary productivity on intertidal mudflats
Despite limited periods of light exposure (Ser6dio and Catarino 1999)
and highly variable temperature conditions (Blanchard and Guarini 1996;
Ser6dio and Catarino 1999) estuarine microphytobenthos have been recorded to
contribute up to 1/3 of the total estuarine carbon budget (Sullivan and Moncrieff
1988; Sundback et al. 1997; see Underwood and Kromkamp 1999 for further
discussion). Guarini et al. (2000) discussed the "vertical scale compression
problem" whereby photosynthetic activity is limited to the upper gm. It is the
problems associated with sampling at this scale that has hindered progress in this
field compared to pelagic systems as well as the daily changes In photon fluence
rates, temperatures and the migration of cells in and out of the photic zone
(discussed above). Therefore, the inherent variation in microphytobenthic
primary productivity patterns (seasonal and hourly) (Kromkamp et al. 1995;
Barranguet 1997) complicates any extrapolations/estimations.
Guarini et al. (2000) examined the behavioural and physiological
processes that control primary productivity on intertidal mudflats, proposing and
verifying a simple model of primary productivity and biomass changes over the
exposure penod. The authors concluded that temperature was the prominent
feature controlling the dynamics of benthic primary production, but discussed the
key role of light in controlling the migration of phototrophs to the sediment
surface. They separated the sediment biofilm into two compartments: surface and
sub-surface and hypothesised the surface component to be saturated with
biomass and having a continuous light distribution.
Pinckney and Zingmark (1991) attributed daily variations in primary
production to changes in the distribution of biomass related to tidal stage and sun
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