Applied use of taxonomy: lessons learned from the fi rst German intercalibration exercise for benthic diatoms

The fi rst German intercalibration exercise for benthic diatoms was conducted to improve the application of the implementation of the European Water Framework Directive for running waters and lakes in Germany. The intercalibration exercise revealed several taxonomic problems. Among others, considerable problems occurred with identifying and differentiating species of the following four groups: (I) Amphora indistincta Levkov and A. pediculus (Kützing) Grunow, (II) Cocconeis placentula var. euglypta Ehrenberg and C. placentula var. lineata (Ehrenberg) Van Heurck, (III) Navicula cryptotenella Lange-Bertalot and N. cryptotenelloides Lange-Bertalot and (IV) N. reichardtiana Lange-Bertalot and N. caterva Hohn & Hellermann. The taxonomic problems that emerged occurred due to both insuffi cient use of given taxonomic details (by limnologists) and ambiguous species descriptions and documentation (by taxonomists). Thus, we recommend to the applied limnologist to use the mandatory identifi cation literature and to document any ambiguous valves during routine counts. Also, it would be desirable to further investigate certain species by taxonomists and, in general, to provide more basic data with species descriptions or in identifi cation manuals. These measures will improve the use of diatoms as bioindicators and consequently benefi t both applied limnologists and taxonomists.