Microphytobenthos are the dominant primary producers on estuarine mudflats playing a key role in the functioning of the ecosystem. Studies into microphytobenthic ecology have previously been limited by scale but the advent of fine scale analysis techniques (micrometre) as well as non-destructive sampling has enabled the system to be examined at a level not previously possible. This study will present work examining the formation, structure and function of microphytobenthic biofilms using non-destructive (remote sensing by PAM fluorescence; fibreoptic light microprofiling) and destructive (cryo-freezing and Low temperature scanning electron microscopy) sampling.
Microscale sectioning (micrometre) showed that chlorophyll a was always concentrated in the top 400 micrometres (the photosynthetically active biomass). No clear migratory patterns were detected using microscale sectioning despite LTSEM analysis demonstrating diurnal taxonomic shifts. Therefore in some systems migration occurs over a scale < 400 micrometres providing circumstantial evidence that microphytobenthic cells sub-cycle at the sediment surface to optimise fitness. Light, tidal state, endogeny and combinations thereof were all shown to control migration, demonstrating that predictable migratory rhythms cannot be assumed
The light extinction co-efficient (k) of microphytobenthic biofilms was shown to significantly vary with site, assemblage and also over time. 90% of the surface PPFD had always been attenuated by 400 micrometres, and in many cases before 200 micrometres.
Traditional microphytobenthic primary productivity models do not account for changes in the spatial and temporal distribution of biomass or light attenuation and therefore their applicability to the real situation may be limited.