Mireille Consalvey PhD Thesis - University of St Andrews

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amphioxys, migrating into the sediment at high irradiances and another,
Pleurosigma angulatum, staying at the surface.
Whilst microphytobenthic populations show a general increase in
biomass at the sediment surface over a low tide exposure period, subtle
differences between populations/sites have been shown, particularly in tenns of
whether or not the cells remain at the sediment surface towards the end of the
low tide period. Therefore, all future studies into microphytobenthos must take
this variation into account (e. g. all investigations into microphytobenthic primary
productivity should consider migratory induced variation in the surface biomass
to successfully incorporate PAB into primary productivity models). Many studies
have attempted to map biomass distribution at the ecosystem level (basin scale),
but the time involved in sampling often means that short term changes in
biomass such as those shown here are overlooked (e. g. BIOPTIS). There is huge
potential for error in estimating microphytobenthic biomass and future studies
need to incorporate microphytobenthic movements into ecosystem models (e. g.
the HiMoM project which is the second stage of BIOPTIS).
The above studies used fluorescence to trace changes in the distribution
of chlorophyll a (Ser6dio et al. 1997; 2001; Barranguet et al.
1998; Kromkamp
et al. 1998; Perkins et al. 2001; Honeywill et al. 2002) and the advantages and
disadvantages of this technique will be evaluated below. Chlorophyll a is only a
proxy measure for biomass and accurately determining chlorophyll a
content/concentration in sediments has been a challenge for benthic workers.
Wiltshire et al. (1997) developed the Cryolander to sample at a microscale level
(ýtm) which has been a huge advance in the field. The Cryolander was used in
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