Diatoms

The basic requirements for diatom analysis have changed little over the last few decades in terms of sampling, slide preparation, microscopy and taxonomy but, on the other hand, there have been major improvements in our knowledge of diatom distribution and ecology and a revolution in our ability to analyse diatom data. These changes have been driven by the increasing recognition of the practical uses of diatoms as indicators of environmental change and by the development of novel numerical and computing techniques that allow diatom-environment relationships to be quantified. However, in the future and despite the application of new techniques (e.g., Vasko et al., 2000), it is unlikely that there will be significant improvements in transfer function statistics or in the range of environmental variables for which diatoms can be confidently used. Nevertheless, there is real scope for making transfer functions much more widely applicable around the world principally through web-based information systems such as EDDI (Battarbee et al., 2000), and in using the databases generated through merged training sets to explore unresolved and vastly under-researched questions of diatom biogeography. In addition, as multi-proxy approaches in palaeolimnology become common, diatomists should be able to focus more on questions of ecological response to environmental change rather than on reconstructing environmental change per se. Such a move would be especially welcome as it would herald a change from purely empirical mechanistic approaches inherent in the transfer function method to approaches that require a deeper understanding of diatom habitats, life-cycles and competitive strategies and a wider consideration of the role of diatoms in the overall functioning of aquatic ecosystems