European Diatom Database-Surface Waters Acidification Programme

The European Diatom Database (EDDI) is a web-based information system designed
to enhance the application of diatom analysis to problems of surface water
acidification, eutrophication and climate change.

The Surface Waters Acidification Programme (SWAP) calibration training set
included initially 178 surface sediment diatom assemblages and the associated
environmental variables from 170 sites. Data-screening reduced these to 167
lakes, which using weighted averaging give superior results in terms of lowest
root mean squared errors of prediction in cross-validation (Birks et al. 1990a;
Birks et al. 1990b). The refined diatom/water chemistry training set used
within the SWAP project is derived from five regional datasets (number of
samples in parentheses) from Sweden (30), Norway (51), Scotland (60), Wales
(32) and the English Lake District (5). These sites represent upland lakes in
Britain and both upland and lowland lakes in Scandinavia with a bias towards
acidic waters. Using gravity or a piston corer, surface sediment samples were
usually taken from the deepest point in each lake and in all cases the top 0.5
cm was used for diatom preparation. A total of approximately 500 diatom valves
per sample were counted. As a result of the considerable variation in taxonomic
and nomenclatural usage between diatomists in different laboratories a
programme of taxonomic harmonization was undertaken to construct a common
diatom dataset (Munro et al. 1990). The development and application of the SWAP
training set is very well documented in the publications cited below and in
many subsequent projects which have applied SWAP training set in other contexts
or compared its performance with that of new training sets.