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Spatial dynamics of microphytobenthos determined by PAM fluorescence
No full textThe distribution of microphytobenthos on intertidal flats is heterogeneous and described as ‘‘patchy’’ over spatial scales of
centimetres to kilometres. The spatial structure and the dynamics of microphytobenthic biomass during tidal emersion were
investigated by creating high resolution fluorescence distribution maps of biomass (Fo) at the sediment surface (0.5 cm pixels,
20 cm!20 cm). The PSII maximum quantum efficiency was also calculated for correlation with biomass structure. Intertidal areas
of the Biezelingsche Ham (Westerschelde) and Zandkreek (Oosterschelde), The Netherlands, were sampled during June 2000. The
spaceetime variability of the discrete fields obtained was analysed by studying their spatial variogram and their time
autocorrelation. Sites showed significant differences in absolute variation of microphytobenthic biomass and in the dynamics of
the development of spatial structure throughout the emersion period. The variograms indicated little spatial correlations in the
biomass fields above the 2 cm scale, while the time autocorrelation showed a strong persistence of biomass structure at time scales
between 1 h and 5 h. The Biezelingse Ham biofilm was shown to be migratory in nature while the Zandkreek system was more
stable. At the former site, biomass distribution became more homogenous with time, as upward migration of cells attenuated
horizontal patchiness. At the Biezelingsche Ham site, maximum PSII quantum efficiencies varied inversely with biomass areas;
reasons for this may include nutrient depletion and CO2 limitation within dense biofilms
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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