The total combined taxon count of all data sets was 2146. Most
taxa were identified to species level or below (1675) or genus level
(406), the restwere identified to a higher taxonomic level. The most
common organisms, normalized by the sampling effort between
regions, were unidentified centric diatoms, unidentified taxa,
Skeletonema costatum and Ceratoneis closterium, which were
encountered in 57, 50, 47 and 47% of the samples, respectively
(Fig. 2). Algae identified as Skeletonema costatum may contain
several closely related species. E.g. in the Baltic Sea and adjacent
coastal waters much of the earlier records of S. costatum should be