In 1983, when the Surface Waters Acidification Programme (SWAP) was announced, we were asked
to design and implement a palaeolimnology sub-project involving scientists from Sweden, Norway,
and the UK. Our aim was to reconstruct the acidification history of a range of sites in the three
countries and to identify and evaluate the various alternative causes of lake acidification. The results of the project have been published recently (Battarbee et al. 1990, Renberg and Battarbee 1990). Although a comprehensive range of palaeolimnological methods and approaches was used in the study we recognised diatom analysis as central to the entire project. We consequently committed
considerable effort to improving our diatom methodology and we were especially concerned with the
pursuit of a common approach to diatom taxonomy and pH reconstruction. This effort centred on the
creation and analysis of a large data-set of surface-sediment diatom assemblages and associated
environmental variables from 170 sites representing the full range of lake types in the acid-sensitive
and acidified regions of the three countries
